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Sample records for perturbed conformal field

  1. Cosmological density perturbations in a conformal scalar field theory

    NASA Astrophysics Data System (ADS)

    Libanov, M. V.; Rubakov, V. A.

    2012-02-01

    We consider a scenario in which primordial scalar perturbations are generated when a complex conformal scalar field rolls down its negative quartic potential. Initially, these are perturbations of the phase of this field, which are then converted into adiabatic perturbations of the density. The existence of perturbations in the radial field direction, which have a red power spectrum, is a potentially dangerous feature of this scenario. But we show that in the linear order in the small parameter, the self-coupling, the infrared effects are completely nullified by an appropriate field redefinition. We evaluate the statistical anisotropy inherent in the model because of the presence of the long-wave perturbations of the radial field component. In the linear order in the self-coupling, the infrared effects do not affect the statistical anisotropy. They are manifested only at the quadratic order in the self-coupling, weakly (logarithmically) enhancing the corresponding contribution to the statistical anisotropy. The resulting statistical anisotropy is a combination of a large term, which decreases as the momentum increases, and a momentum-independent nonamplified term.

  2. Masses of higher spin fields on AdS4 and conformal perturbation theory

    NASA Astrophysics Data System (ADS)

    Hikida, Yasuaki

    2016-07-01

    We study the breaking of gauge symmetry for higher spin theory on AdS4 dual to the 3d critical O (N ) vector model. It was argued that the breaking is due to the change of boundary condition for a scalar field through a loop effect and the Goldstone modes are bound states of a scalar field and higher spin field. The masses of higher spin fields were obtained from the anomalous dimensions of dual currents at the leading order in 1 /N , and we reproduce them from the O (N ) vector model in the conformal perturbation theory. The anomalous dimensions can be computed from the bulk theory using Witten diagrams, and we show that the bulk computation reduces to the boundary one in the conformal perturbation theory. With this fact our computation provides an additional support for the bulk interpretation.

  3. Integrable perturbations of conformal field theories and Yetter-Drinfeld modules

    SciTech Connect

    Bücher, David; Runkel, Ingo

    2014-11-15

    In this paper we relate a problem in representation theory — the study of Yetter-Drinfeld modules over certain braided Hopf algebras — to a problem in two-dimensional quantum field theory, namely, the identification of integrable perturbations of a conformal field theory. A prescription that parallels Lusztig's construction allows one to read off the quantum group governing the integrable symmetry. As an example, we illustrate how the quantum group for the loop algebra of sl(2) appears in the integrable structure of the perturbed uncompactified and compactified free boson.

  4. New perturbation theory representation of the conformal symmetry breaking effects in gauge quantum field theory models

    NASA Astrophysics Data System (ADS)

    Kataev, A. L.; Mikhailov, S. V.

    2012-02-01

    We propose a hypothesis on the detailed structure for the representation of the conformal symmetry breaking term in the basic Crewther relation generalized in the perturbation theory framework in QCD renormalized in the overline {MS} scheme. We establish the validity of this representation in the O(α{/s 4 }) approximation. Using the variant of the generalized Crewther relation formulated here allows finding relations between specific contributions to the QCD perturbation series coefficients for the flavor nonsinglet part of the Adler function D{/A ns } for the electron-positron annihilation in hadrons and to the perturbation series coefficients for the Bjorken sum rule S Bjp for the polarized deep-inelastic lepton-nucleon scattering. We find new relations between the α{/s 4 } coefficients of D{/A ns } and S Bjp . Satisfaction of one of them serves as an additional theoretical verification of the recent computer analytic calculations of the terms of order α{/s 4 } in the expressions for these two quantities.

  5. Fitting of Hadron Mass Spectra and Contributions to Perturbation Theory of Conformal Quantum Field Theory

    NASA Astrophysics Data System (ADS)

    Luna Acosta, German Aurelio

    The masses of observed hadrons are fitted according to the kinematic predictions of Conformal Relativity. The hypothesis gives a remarkably good fit. The isospin SU(2) gauge invariant Lagrangian L(,(pi)NN)(x,(lamda)) is used in the calculation of d(sigma)/d(OMEGA) to 2nd-order Feynman graphs for simplified models of (pi)N(--->)(pi)N. The resulting infinite mass sums over the nucleon (Conformal) families are done via the Generalized-Sommerfeld-Watson Transform Theorem. Even though the models are too simple to be realistic, they indicate that if (DELTA)-internal lines were to be included, 2nd-order Feynman graphs may reproduce the experimental data qualitatively. The energy -dependence of the propagator and couplings in Conformal QFT is different from that of ordinary QFT. Suggestions for further work are made in the areas of ultra-violet divergences and OPEC calculations.

  6. Extended conformal field theories

    NASA Astrophysics Data System (ADS)

    Taormina, Anne

    1990-08-01

    Some extended conformal field theories are briefly reviewed. They illustrate how non minimal models of the Virasoro algebra (c≥1) can become minimal with respect to a larger algebra. The accent is put on N-extended superconformal algebras, which are relevant in superstring compactification.

  7. Conformal scalar field wormholes

    NASA Technical Reports Server (NTRS)

    Halliwell, Jonathan J.; Laflamme, Raymond

    1989-01-01

    The Euclidian Einstein equations with a cosmological constant and a conformally coupled scalar field are solved, taking the metric to be of the Robertson-Walker type. In the case Lambda = 0, solutions are found which represent a wormhole connecting two asymptotically flat Euclidian regions. In the case Lambda greater than 0, the solutions represent tunneling from a small Tolman-like universe to a large Robertson-Walker universe.

  8. Warped conformal field theory

    NASA Astrophysics Data System (ADS)

    Detournay, Stéphane; Hartman, Thomas; Hofman, Diego M.

    2012-12-01

    We study field theories in two spacetime dimensions invariant under a chiral scaling symmetry that acts only on right-movers. The local symmetries include one copy of the Virasoro algebra and a U(1) current algebra. This differs from the two-dimensional conformal group but in some respects is equally powerful in constraining the theory. In particular, the symmetries on a torus lead to modular covariance of the partition function, which is used to derive a universal formula for the asymptotic density of states. For an application we turn to the holographic description of black holes in quantum gravity, motivated by the fact that the symmetries in the near-horizon geometry of any extremal black hole are identical to those of a two-dimensional field theory with chiral scaling. We consider two examples: black holes in warped AdS3 in topologically massive gravity and in string theory. In both cases, the density of states in the two-dimensional field theory reproduces the Bekenstein-Hawking entropy of black holes in the gravity theory.

  9. Logarithmic conformal field theory

    NASA Astrophysics Data System (ADS)

    Gainutdinov, Azat; Ridout, David; Runkel, Ingo

    2013-12-01

    Conformal field theory (CFT) has proven to be one of the richest and deepest subjects of modern theoretical and mathematical physics research, especially as regards statistical mechanics and string theory. It has also stimulated an enormous amount of activity in mathematics, shaping and building bridges between seemingly disparate fields through the study of vertex operator algebras, a (partial) axiomatisation of a chiral CFT. One can add to this that the successes of CFT, particularly when applied to statistical lattice models, have also served as an inspiration for mathematicians to develop entirely new fields: the Schramm-Loewner evolution and Smirnov's discrete complex analysis being notable examples. When the energy operator fails to be diagonalisable on the quantum state space, the CFT is said to be logarithmic. Consequently, a logarithmic CFT is one whose quantum space of states is constructed from a collection of representations which includes reducible but indecomposable ones. This qualifier arises because of the consequence that certain correlation functions will possess logarithmic singularities, something that contrasts with the familiar case of power law singularities. While such logarithmic singularities and reducible representations were noted by Rozansky and Saleur in their study of the U (1|1) Wess-Zumino-Witten model in 1992, the link between the non-diagonalisability of the energy operator and logarithmic singularities in correlators is usually ascribed to Gurarie's 1993 article (his paper also contains the first usage of the term 'logarithmic conformal field theory'). The class of CFTs that were under control at this time was quite small. In particular, an enormous amount of work from the statistical mechanics and string theory communities had produced a fairly detailed understanding of the (so-called) rational CFTs. However, physicists from both camps were well aware that applications from many diverse fields required significantly more

  10. Logarithmic conformal field theory

    NASA Astrophysics Data System (ADS)

    Gainutdinov, Azat; Ridout, David; Runkel, Ingo

    2013-12-01

    Conformal field theory (CFT) has proven to be one of the richest and deepest subjects of modern theoretical and mathematical physics research, especially as regards statistical mechanics and string theory. It has also stimulated an enormous amount of activity in mathematics, shaping and building bridges between seemingly disparate fields through the study of vertex operator algebras, a (partial) axiomatisation of a chiral CFT. One can add to this that the successes of CFT, particularly when applied to statistical lattice models, have also served as an inspiration for mathematicians to develop entirely new fields: the Schramm-Loewner evolution and Smirnov's discrete complex analysis being notable examples. When the energy operator fails to be diagonalisable on the quantum state space, the CFT is said to be logarithmic. Consequently, a logarithmic CFT is one whose quantum space of states is constructed from a collection of representations which includes reducible but indecomposable ones. This qualifier arises because of the consequence that certain correlation functions will possess logarithmic singularities, something that contrasts with the familiar case of power law singularities. While such logarithmic singularities and reducible representations were noted by Rozansky and Saleur in their study of the U (1|1) Wess-Zumino-Witten model in 1992, the link between the non-diagonalisability of the energy operator and logarithmic singularities in correlators is usually ascribed to Gurarie's 1993 article (his paper also contains the first usage of the term 'logarithmic conformal field theory'). The class of CFTs that were under control at this time was quite small. In particular, an enormous amount of work from the statistical mechanics and string theory communities had produced a fairly detailed understanding of the (so-called) rational CFTs. However, physicists from both camps were well aware that applications from many diverse fields required significantly more

  11. Osmolyte perturbation reveals conformational equilibria in spin-labeled proteins

    PubMed Central

    López, Carlos J; Fleissner, Mark R; Guo, Zhefeng; Kusnetzow, Ana K; Hubbell, Wayne L

    2009-01-01

    Recent evidence suggests that proteins at equilibrium can exist in a manifold of conformational substates, and that these substates play important roles in protein function. Therefore, there is great interest in identifying regions in proteins that are in conformational exchange. Electron paramagnetic resonance spectra of spin-labeled proteins containing the nitroxide side chain (R1) often consist of two (or more) components that may arise from slow exchange between conformational substates (lifetimes > 100 ns). However, crystal structures of proteins containing R1 have shown that multicomponent spectra can also arise from equilibria between rotamers of the side chain itself. In this report, it is shown that these scenarios can be distinguished by the response of the system to solvent perturbation with stabilizing osmolytes such as sucrose. Thus, site-directed spin labeling (SDSL) emerges as a new tool to explore slow conformational exchange in proteins of arbitrary size, including membrane proteins in a native-like environment. Moreover, equilibrium between substates with even modest differences in conformation is revealed, and the simplicity of the method makes it suitable for facile screening of multiple proteins. Together with previously developed strategies for monitoring picosecond to millisecond backbone dynamics, the results presented here expand the timescale over which SDSL can be used to explore protein flexibility. PMID:19585559

  12. Osmolyte perturbation reveals conformational equilibria in spin-labeled proteins.

    PubMed

    López, Carlos J; Fleissner, Mark R; Guo, Zhefeng; Kusnetzow, Ana K; Hubbell, Wayne L

    2009-08-01

    Recent evidence suggests that proteins at equilibrium can exist in a manifold of conformational substates, and that these substates play important roles in protein function. Therefore, there is great interest in identifying regions in proteins that are in conformational exchange. Electron paramagnetic resonance spectra of spin-labeled proteins containing the nitroxide side chain (R1) often consist of two (or more) components that may arise from slow exchange between conformational substates (lifetimes > 100 ns). However, crystal structures of proteins containing R1 have shown that multicomponent spectra can also arise from equilibria between rotamers of the side chain itself. In this report, it is shown that these scenarios can be distinguished by the response of the system to solvent perturbation with stabilizing osmolytes such as sucrose. Thus, site-directed spin labeling (SDSL) emerges as a new tool to explore slow conformational exchange in proteins of arbitrary size, including membrane proteins in a native-like environment. Moreover, equilibrium between substates with even modest differences in conformation is revealed, and the simplicity of the method makes it suitable for facile screening of multiple proteins. Together with previously developed strategies for monitoring picosecond to millisecond backbone dynamics, the results presented here expand the timescale over which SDSL can be used to explore protein flexibility. PMID:19585559

  13. Conformational Analysis on structural perturbations of the zinc finger NEMO

    NASA Astrophysics Data System (ADS)

    Godwin, Ryan; Salsbury, Freddie; Salsbury Group Team

    2014-03-01

    The NEMO (NF-kB Essential Modulator) Zinc Finger protein (2jvx) is a functional Ubiquitin-binding domain, and plays a role in signaling pathways for immune/inflammatory responses, apoptosis, and oncogenesis [Cordier et al., 2008]. Characterized by 3 cysteines and 1 histidine residue at the active site, the biologically occurring, bound zinc configuration is a stable structural motif. Perturbations of the zinc binding residues suggest conformational changes in the 423-atom protein characterized via analysis of all-atom molecular dynamics simulations. Structural perturbations include simulations with and without a zinc ion and with and without de-protonated cysteines, resulting in four distinct configurations. Simulations of various time scales show consistent results, yet the longest, GPU driven, microsecond runs show more drastic structural and dynamic fluctuations when compared to shorter duration time-scales. The last cysteine residue (26 of 28) and the helix on which it resides exhibit a secondary, locally unfolded conformation in addition to its normal bound conformation. Combined analytics elucidate how the presence of zinc and/or protonated cysteines impact the dynamics and energetic fluctuations of NEMO. Comprehensive Cancer Center of Wake Forest University Computational Biosciences shared resource supported by NCI CCSG P30CA012197.

  14. Statistical anisotropy of the curvature perturbation from vector field perturbations

    SciTech Connect

    Dimopoulos, Konstantinos; Karciauskas, Mindaugas; Lyth, David H.; Rodriguez, Yeinzon E-mail: m.karciauskas@lancaster.ac.uk E-mail: yeinzon.rodriguez@uan.edu.co

    2009-05-15

    The {delta}N formula for the primordial curvature perturbation {zeta} is extended to include vector as well as scalar fields. Formulas for the tree-level contributions to the spectrum and bispectrum of {zeta} are given, exhibiting statistical anisotropy. The one-loop contribution to the spectrum of {zeta} is also worked out. We then consider the generation of vector field perturbations from the vacuum, including the longitudinal component that will be present if there is no gauge invariance. Finally, the {delta}N formula is applied to the vector curvaton and vector inflation models with the tensor perturbation also evaluated in the latter case.

  15. Cosmological perturbations: Vorticity, isocurvature and magnetic fields

    NASA Astrophysics Data System (ADS)

    Christopherson, Adam J.

    2014-10-01

    In this paper, I review some recent, interlinked, work undertaken using cosmological perturbation theory — a powerful technique for modeling inhomogeneities in the universe. The common theme which underpins these pieces of work is the presence of nonadiabatic pressure, or entropy, perturbations. After a brief introduction covering the standard techniques of describing inhomogeneities in both Newtonian and relativistic cosmology, I discuss the generation of vorticity. As in classical fluid mechanics, vorticity is not present in linearized perturbation theory (unless included as an initial condition). Allowing for entropy perturbations, and working to second order in perturbation theory, I show that vorticity is generated, even in the absence of vector perturbations, by purely scalar perturbations, the source term being quadratic in the gradients of first order energy density and isocurvature, or nonadiabatic pressure perturbations. This generalizes Crocco's theorem to a cosmological setting. I then introduce isocurvature perturbations in different models, focusing on the entropy perturbation in standard, concordance cosmology, and in inflationary models involving two scalar fields. As the final topic, I investigate magnetic fields, which are a potential observational consequence of vorticity in the early universe. I briefly review some recent work on including magnetic fields in perturbation theory in a consistent way. I show, using solely analytical techniques, that magnetic fields can be generated by higher order perturbations, albeit too small to provide the entire primordial seed field, in agreement with some numerical studies. I close this paper with a summary and some potential extensions of this work.

  16. Quantum field perturbation theory revisited

    NASA Astrophysics Data System (ADS)

    Matone, Marco

    2016-03-01

    Schwinger's formalism in quantum field theory can be easily implemented in the case of scalar theories in D dimension with exponential interactions, such as μDexp (α ϕ ). In particular, we use the relation exp (α δ/δ J (x ) )exp (-Z0[J ])=exp (-Z0[J +αx]) with J the external source, and αx(y )=α δ (y -x ). Such a shift is strictly related to the normal ordering of exp (α ϕ ) and to a scaling relation which follows by renormalizing μ . Next, we derive a new formulation of perturbation theory for the potentials V (ϕ )=λ/n ! :ϕn: , using the generating functional associated to :exp (α ϕ ):. The Δ (0 )-terms related to the normal ordering are absorbed at once. The functional derivatives with respect to J to compute the generating functional are replaced by ordinary derivatives with respect to auxiliary parameters. We focus on scalar theories, but the method is general and similar investigations extend to other theories.

  17. Non-Perturbative Field Theories.

    NASA Astrophysics Data System (ADS)

    Stephenson, David

    Available from UMI in association with The British Library. Requires signed TDF. Some non-perturbative aspects of field theories are studied by applying lattice gauge theory techniques. The low-lying hadronic mass spectrum is calculated numerically using quenched lattice quantum chromodynamics. The results of large numerical simulations performed on a distributed array processor are presented and analysed. Particular emphasis is stressed upon the understanding of systematic and statistical errors in the calculation. In addition, the pion decay constant and the chiral condensate are evaluated. An attempt is made to relate the numerical findings to the experimentally measured quantities. A pioneering attempt to understand Yukawa couplings is discussed. A toy Fermion-Higgs system is studied numerically on a transputer array. Dynamical fermions are included in the investigation of the behavior of the system over a wide range of Yukawa couplings. A phase diagram is found for the model which shows evidence of spontaneous chiral symmetry breaking transitions. Extensions of the model are discussed together some speculations concerning the behaviour of Yukawa couplings in general. The possibility of using the lattice as a model for space-time is investigated by studying the propagation of particles on a fractal lattice. In addition, the use of truncated fractals as novel regulators is studied numerically in the hope that the problem of fermion doubling will be alleviated.

  18. Inflation and deformation of conformal field theory

    SciTech Connect

    Garriga, Jaume; Urakawa, Yuko E-mail: yurakawa@ffn.ub.es

    2013-07-01

    It has recently been suggested that a strongly coupled phase of inflation may be described holographically in terms of a weakly coupled quantum field theory (QFT). Here, we explore the possibility that the wave function of an inflationary universe may be given by the partition function of a boundary QFT. We consider the case when the field theory is a small deformation of a conformal field theory (CFT), by the addition of a relevant operator O, and calculate the primordial spectrum predicted in the corresponding holographic inflation scenario. Using the Ward-Takahashi identity associated with Weyl rescalings, we derive a simple relation between correlators of the curvature perturbation ζ and correlators of the deformation operator O at the boundary. This is done without specifying the bulk theory of gravitation, so that the result would also apply to cases where the bulk dynamics is strongly coupled. We comment on the validity of the Suyama-Yamaguchi inequality, relating the bi-spectrum and tri-spectrum of the curvature perturbation.

  19. A hydrodynamic approach to non-equilibrium conformal field theories

    NASA Astrophysics Data System (ADS)

    Bernard, Denis; Doyon, Benjamin

    2016-03-01

    We develop a hydrodynamic approach to non-equilibrium conformal field theory. We study non-equilibrium steady states in the context of one-dimensional conformal field theory perturbed by the T\\bar{T} irrelevant operator. By direct quantum computation, we show, to first order in the coupling, that a relativistic hydrodynamic emerges, which is a simple modification of one-dimensional conformal fluids. We show that it describes the steady state and its approach, and we provide the main characteristics of the steady state, which lies between two shock waves. The velocities of these shocks are modified by the perturbation and equal the sound velocities of the asymptotic baths. Pushing this approach further, we are led to conjecture that the approach to the steady state is generically controlled by the power law t -1/2, and that the widths of the shocks increase with time according to t 1/3.

  20. Logarithmic operators and logarithmic conformal field theories

    NASA Astrophysics Data System (ADS)

    Gurarie, Victor

    2013-12-01

    Logarithmic operators and logarithmic conformal field theories are reviewed. Prominent examples considered here include c = -2 and c = 0 logarithmic conformal field theories. c = 0 logarithmic conformal field theories are especially interesting since they describe some of the critical points of a variety of longstanding problems involving a two dimensional quantum particle moving in a spatially random potential, as well as critical two dimensional self-avoiding random walks and percolation. Lack of classification of logarithmic conformal field theories remains a major impediment to progress towards finding complete solutions to these problems.

  1. Solving the Helmholtz equation in conformal mapped ARROW structures using homotopy perturbation method.

    PubMed

    Reck, Kasper; Thomsen, Erik V; Hansen, Ole

    2011-01-31

    The scalar wave equation, or Helmholtz equation, describes within a certain approximation the electromagnetic field distribution in a given system. In this paper we show how to solve the Helmholtz equation in complex geometries using conformal mapping and the homotopy perturbation method. The solution of the mapped Helmholtz equation is found by solving an infinite series of Poisson equations using two dimensional Fourier series. The solution is entirely based on analytical expressions and is not mesh dependent. The analytical results are compared to a numerical (finite element method) solution. PMID:21368995

  2. Holographic de Sitter Geometry from Entanglement in Conformal Field Theory

    NASA Astrophysics Data System (ADS)

    de Boer, Jan; Heller, Michal P.; Myers, Robert C.; Neiman, Yasha

    2016-02-01

    We demonstrate that, for general conformal field theories (CFTs), the entanglement for small perturbations of the vacuum is organized in a novel holographic way. For spherical entangling regions in a constant time slice, perturbations in the entanglement entropy are solutions of a Klein-Gordon equation in an auxiliary de Sitter (dS) spacetime. The role of the emergent timelike direction in dS spacetime is played by the size of the entangling sphere. For CFTs with extra conserved charges, e.g., higher-spin charges, we show that each charge gives rise to a separate dynamical scalar field in dS spacetime.

  3. Vertex operator algebras and conformal field theory

    SciTech Connect

    Huang, Y.Z. )

    1992-04-20

    This paper discusses conformal field theory, an important physical theory, describing both two-dimensional critical phenomena in condensed matter physics and classical motions of strings in string theory. The study of conformal field theory will deepen the understanding of these theories and will help to understand string theory conceptually. Besides its importance in physics, the beautiful and rich mathematical structure of conformal field theory has interested many mathematicians. New relations between different branches of mathematics, such as representations of infinite-dimensional Lie algebras and Lie groups, Riemann surfaces and algebraic curves, the Monster sporadic group, modular functions and modular forms, elliptic genera and elliptic cohomology, Calabi-Yau manifolds, tensor categories, and knot theory, are revealed in the study of conformal field theory. It is therefore believed that the study of the mathematics involved in conformal field theory will ultimately lead to new mathematical structures which would be important to both mathematics and physics.

  4. Non Perturbative Aspects of Field Theory

    SciTech Connect

    Bashir, A.

    2009-04-20

    For any quantum field theory (QFT), there exists a set of Schwinger-Dyson equations (SDE) for all its Green functions. However, it is not always straight forward to extract quantitatively exact physical information from this set of equations, especially in the non perturbative regime. The situation becomes increasingly complex with growing number of external legs. I give a qualitative account of the hunt for the non perturbative Green functions in gauge theories.

  5. Defects in conformal field theory

    NASA Astrophysics Data System (ADS)

    Billò, Marco; Gonçalves, Vasco; Lauria, Edoardo; Meineri, Marco

    2016-04-01

    We discuss consequences of the breaking of conformal symmetry by a flat or spherical extended operator. We adapt the embedding formalism to the study of correlation functions of symmetric traceless tensors in the presence of the defect. Two-point functions of a bulk and a defect primary are fixed by conformal invariance up to a set of OPE coefficients, and we identify the allowed tensor structures. A correlator of two bulk primaries depends on two cross-ratios, and we study its conformal block decomposition in the case of external scalars. The Casimir equation in the defect channel reduces to a hypergeometric equation, while the bulk channel blocks are recursively determined in the light-cone limit. In the special case of a defect of codimension two, we map the Casimir equation in the bulk channel to the one of a four-point function without defect. Finally, we analyze the contact terms of the stress-tensor with the extended operator, and we deduce constraints on the CFT data. In two dimensions, we relate the displacement operator, which appears among the contact terms, to the reflection coefficient of a conformal interface, and we find unitarity bounds for the latter.

  6. Perturbations of single-field inflation in modified gravity theory

    NASA Astrophysics Data System (ADS)

    Qiu, Taotao; Xia, Jun-Qing

    2015-05-01

    In this paper, we study the case of single field inflation within the framework of modified gravity theory where the gravity part has an arbitrary form f (R). Via a conformal transformation, this case can be transformed into its Einstein frame where it looks like a two-field inflation model. However, due to the existence of the isocurvature modes in such a multi-degree-of-freedom (m.d.o.f.) system, the (curvature) perturbations are not equivalent in two frames, so despite of its convenience, it is illegal to treat the perturbations in its Einstein frame as the "real" ones as we always do for pure f (R) theory or single field with nonminimal coupling. Here by pulling the results of curvature perturbations back into its original Jordan frame, we show explicitly the power spectrum and spectral index of the perturbations in the Jordan frame, as well as how it differs from the Einstein frame. We also fit our results with the newest Planck data. Since there is large parameter space in these models, we show that it is easy to fit the data very well.

  7. Perturbative renormalization of the electric field correlator

    NASA Astrophysics Data System (ADS)

    Christensen, C.; Laine, M.

    2016-04-01

    The momentum diffusion coefficient of a heavy quark in a hot QCD plasma can be extracted as a transport coefficient related to the correlator of two colour-electric fields dressing a Polyakov loop. We determine the perturbative renormalization factor for a particular lattice discretization of this correlator within Wilson's SU(3) gauge theory, finding a ∼ 12% NLO correction for values of the bare coupling used in the current generation of simulations. The impact of this result on existing lattice determinations is commented upon, and a possibility for non-perturbative renormalization through the gradient flow is pointed out.

  8. Perturbative double field theory on general backgrounds

    NASA Astrophysics Data System (ADS)

    Hohm, Olaf; Marques, Diego

    2016-01-01

    We develop the perturbation theory of double field theory around arbitrary solutions of its field equations. The exact gauge transformations are written in a manifestly background covariant way and contain at most quadratic terms in the field fluctuations. We expand the generalized curvature scalar to cubic order in fluctuations and thereby determine the cubic action in a manifestly background covariant form. As a first application we specialize this theory to group manifold backgrounds, such as S U (2 )≃S3 with H -flux. In the full string theory this corresponds to a Wess-Zumino-Witten background CFT. Starting from closed string field theory, the cubic action around such backgrounds has been computed before by Blumenhagen, Hassler, and Lüst. We establish precise agreement with the cubic action derived from double field theory. This result confirms that double field theory is applicable to arbitrary curved background solutions, disproving assertions in the literature to the contrary.

  9. An introduction to conformal field theory

    NASA Astrophysics Data System (ADS)

    Gaberdiel, Matthias R.

    2000-04-01

    A comprehensive introduction to two-dimensional conformal field theory is given. The structure of the meromorphic subtheory is described in detail, and a number of examples are presented explicitly. Standard constructions such as the coset and the orbifold construction are explained. The concept of a representation of the meromorphic theory is introduced, and the role of Zhu's algebra in classifying highest weight representations is elucidated. The fusion product of two representations and the corresponding fusion rules are defined, and Verlinde's formula is explained. Finally, higher correlation functions are considered, and the polynomial relations of Moore and Seiberg and the quantum group structure of chiral conformal field theory are discussed. The treatment is relatively general and also allows for a description of less well known classes of theories such as logarithmic conformal field theories.

  10. Entanglement entropy of excited states in conformal perturbation theory and the Einstein equation

    NASA Astrophysics Data System (ADS)

    Speranza, Antony J.

    2016-04-01

    For a conformal field theory (CFT) deformed by a relevant operator, the entanglement entropy of a ball-shaped region may be computed as a perturbative expansion in the coupling. A similar perturbative expansion exists for excited states near the vacuum. Using these expansions, this work investigates the behavior of excited state entanglement entropies of small, ball-shaped regions. The motivation for these calculations is Jacobson's recent work on the equivalence of the Einstein equation and the hypothesis of maximal vacuum entropy [arXiv:1505.04753], which relies on a conjecture stating that the behavior of these entropies is sufficiently similar to a CFT. In addition to the expected type of terms which scale with the ball radius as R d , the entanglement entropy calculation gives rise to terms scaling as R 2Δ, where Δ is the dimension of the deforming operator. When \\varDelta ≤ d/2 , the latter terms dominate the former, and suggest that a modification to the conjecture is needed.

  11. CFT driven cosmology and conformal higher spin fields

    NASA Astrophysics Data System (ADS)

    Barvinsky, A. O.

    2016-05-01

    Conformal higher spin (CHS) field theory, which is a solid part of recent advanced checks of AdS/CFT correspondence, finds applications in cosmology. The hidden sector of weakly interacting CHS fields suggests a resolution of the hierarchy problem in the model of initial conditions for inflationary cosmology driven by a conformal field theory. These initial conditions are set by thermal garland-type cosmological instantons in the sub-Planckian energy range for the model of CHS fields with a large positive coefficient β of the Gauss-Bonnet term in their total conformal anomaly and a large number of their polarizations N . The upper bound of this range MP/√{β } is shown to be much lower than the gravitational cutoff MP/√{N } which is defined by the requirement of smallness of the perturbatively nonrenormalizable graviton loop contributions. In this way we justify the approximation scheme in which the nonrenormalizable graviton sector is subject to effective field theory under this cutoff, whereas the renormalizable sector of multiple CHS fields is treated beyond perturbation theory and dynamically generates the bound on the inflation scale of the CFT cosmology MP/√{β }≪MP/√{N }. This confirms recent predictions for the origin of the Starobinsky R2 and Higgs inflation models from the CHS cosmology, which occurs at the energy scale 3 or 4 orders of magnitude below the gravitational cutoff, √{N /β }˜10-3- 10-4 . We also consider cosmological models dominated by fermionic CHS fields with a negative β and anomaly free models of infinite towers of CHS fields with β =0 and briefly discuss the status of unitarity in CHS models.

  12. Causality constraints in conformal field theory

    NASA Astrophysics Data System (ADS)

    Hartman, Thomas; Jain, Sachin; Kundu, Sandipan

    2016-05-01

    Causality places nontrivial constraints on QFT in Lorentzian signature, for example fixing the signs of certain terms in the low energy Lagrangian. In d dimensional conformal field theory, we show how such constraints are encoded in crossing symmetry of Euclidean correlators, and derive analogous constraints directly from the conformal bootstrap (analytically). The bootstrap setup is a Lorentzian four-point function corresponding to propagation through a shockwave. Crossing symmetry fixes the signs of certain log terms that appear in the conformal block expansion, which constrains the interactions of low-lying operators. As an application, we use the bootstrap to rederive the well known sign constraint on the (∂ ϕ)4 coupling in effective field theory, from a dual CFT. We also find constraints on theories with higher spin conserved currents. Our analysis is restricted to scalar correlators, but we argue that similar methods should also impose nontrivial constraints on the interactions of spinning operators.

  13. Perturbative quantum gravity in double field theory

    NASA Astrophysics Data System (ADS)

    Boels, Rutger H.; Horst, Christoph

    2016-04-01

    We study perturbative general relativity with a two-form and a dilaton using the double field theory formulation which features explicit index factorisation at the Lagrangian level. Explicit checks to known tree level results are performed. In a natural covariant gauge a ghost-like scalar which contributes even at tree level is shown to decouple consistently as required by perturbative unitarity. In addition, a lightcone gauge is explored which bypasses the problem altogether. Using this gauge to study BCFW on-shell recursion, we can show that most of the D-dimensional tree level S-matrix of the theory, including all pure graviton scattering amplitudes, is reproduced by the double field theory. More generally, we argue that the integrand may be reconstructed from its single cuts and provide limited evidence for off-shell cancellations in the Feynman graphs. As a straightforward application of the developed technology double field theory-like expressions for four field string corrections are derived.

  14. Parallel magnetic field perturbations in gyrokinetic simulations

    SciTech Connect

    Joiner, N.; Hirose, A.; Dorland, W.

    2010-07-15

    At low beta it is common to neglect parallel magnetic field perturbations on the basis that they are of order beta{sup 2}. This is only true if effects of order beta are canceled by a term in the nablaB drift also of order beta[H. L. Berk and R. R. Dominguez, J. Plasma Phys. 18, 31 (1977)]. To our knowledge this has not been rigorously tested with modern gyrokinetic codes. In this work we use the gyrokinetic code GS2[Kotschenreuther et al., Comput. Phys. Commun. 88, 128 (1995)] to investigate whether the compressional magnetic field perturbation B{sub ||} is required for accurate gyrokinetic simulations at low beta for microinstabilities commonly found in tokamaks. The kinetic ballooning mode (KBM) demonstrates the principle described by Berk and Dominguez strongly, as does the trapped electron mode, in a less dramatic way. The ion and electron temperature gradient (ETG) driven modes do not typically exhibit this behavior; the effects of B{sub ||} are found to depend on the pressure gradients. The terms which are seen to cancel at long wavelength in KBM calculations can be cumulative in the ion temperature gradient case and increase with eta{sub e}. The effect of B{sub ||} on the ETG instability is shown to depend on the normalized pressure gradient beta{sup '} at constant beta.

  15. Conformers of CL-20 explosive and ab initio refinement using perturbation theory: implications to detonation mechanisms.

    PubMed

    Molt, Robert W; Bartlett, Rodney J; Watson, Thomas; Bazanté, Alexandre P

    2012-12-13

    We have identified the major conformers of CL-20 explosive, otherwise known as 2,4,6,8,10,12-hexanitrohexaazaisowurtzitane, more formally known as 2,4,6,8,10,12-hexanitrohexaazatetracyclo[5.5.0.0]-dodecane, via Monte Carlo search in conformational space through molecular mechanics and subsequent quantum mechanical refinement using perturbation theory. Our search produced enough conformers to account for all of the various forms of CL-20 found in crystals. This suggests that our methodology will be useful in studying the conformational landscape of other nitramines. The energy levels of the conformers found are all within 0.25 eV of one another based on MBPT(2)/6-311G(d,p); consequently, without further refinement from a method such as coupled cluster theory, all conformers may reasonably be populated at STP in the gas phase. We also report the harmonic vibrational frequencies of conformers, including the implications on the mechanism of detonation. In particular, we establish that the weakest N-N nitramine of CL-20 is the cyclohexane equatorial nitramine. This preliminary mapping of the conformers of CL-20 makes it possible to study the mechanism of detonation of this explosive rigorously in future work. PMID:23136867

  16. Multiloop calculations in perturbative quantum field theory

    NASA Astrophysics Data System (ADS)

    Blokland, Ian Richard

    This thesis deals with high-precision calculations in perturbative quantum field theory. In conjunction with detailed experimental measurements, perturbative quantum field theory provides the quantitative framework with which much of modern particle physics is understood. The results of three new theoretical calculations are presented. The first is a definitive resolution of a recent controversy involving the interaction of a muon with a magnetic field. Specifically, the light-by-light scattering contribution to the anomalous magnetic moment of the muon is shown to be of positive sign, thereby decreasing the discrepancy between theory and experiment. Despite this adjustment to the theoretical prediction, the remaining discrepancy might be a subtle signature of new kinds of particles. The second calculation involves the energy levels of a bound state formed from two charged particles of arbitrary masses. By employing recently developed mass expansion techniques, new classes of solutions are obtained for problems in a field of particle physics with a very rich history. The third calculation provides an improved prediction for the decay of a top quark. In order to obtain this result, a large class of multiloop integrals has been solved for the first time. Top quark decay is just one member of a family of interesting physical processes to which these new results apply. Since specialized calculational techniques are essential ingredients in all three calculations, they are motivated and explained carefully in this thesis. These techniques, once automated with symbolic computational software, have recently opened avenues of solution to a wide variety of important problems in particle physics.

  17. Conformal field theory of critical Casimir forces

    NASA Astrophysics Data System (ADS)

    Emig, Thorsten; Bimonte, Giuseppe; Kardar, Mehran

    2015-03-01

    Thermal fluctuations of a critical system induce long-ranged Casimir forces between objects that couple to the underlying field. For two dimensional conformal field theories (CFT) we derive exact results for the Casimir interaction for a deformed strip and for two compact objects of arbitrary shape in terms of the free energy of a standard region (circular ring or flat strip) whose dimension is determined by the mutual capacitance of two conductors with the objects' shape; and a purely geometric energy that is proportional to conformal charge of the CFT, but otherwise super-universal in that it depends only on the shapes and is independent of boundary conditions and other details. The effect of inhomogenous boundary conditions is also discussed.

  18. Adiabatic and isocurvature perturbation projections in multi-field inflation

    NASA Astrophysics Data System (ADS)

    Gordon, Chris; Saffin, Paul M.

    2013-08-01

    Current data are in good agreement with the predictions of single field inflation. However, the hemispherical asymmetry, seen in the cosmic microwave background data, may hint at a potential problem. Generalizing to multi-field models may provide one possible explanation. A useful way of modeling perturbations in multi-field inflation is to investigate the projection of the perturbation along and perpendicular to the background fields' trajectory. These correspond to the adiabatic and isocurvature perturbations. However, it is important to note that in general there are no corresponding adiabatic and isocurvature fields. The purpose of this article is to highlight the distinction between a field redefinition and a perturbation projection. We provide a detailed derivation of the evolution of the isocurvature perturbation to show that no assumption of an adiabatic or isocurvature field is needed. We also show how this evolution equation is consistent with the field covariant evolution equations for the adiabatic perturbation in the flat field space limit.

  19. Relativistic Lagrangian displacement field and tensor perturbations

    NASA Astrophysics Data System (ADS)

    Rampf, Cornelius; Wiegand, Alexander

    2014-12-01

    We investigate the purely spatial Lagrangian coordinate transformation from the Lagrangian to the basic Eulerian frame. We demonstrate three techniques for extracting the relativistic displacement field from a given solution in the Lagrangian frame. These techniques are (a) from defining a local set of Eulerian coordinates embedded into the Lagrangian frame; (b) from performing a specific gauge transformation; and (c) from a fully nonperturbative approach based on the Arnowitt-Deser-Misner (ADM) split. The latter approach shows that this decomposition is not tied to a specific perturbative formulation for the solution of the Einstein equations. Rather, it can be defined at the level of the nonperturbative coordinate change from the Lagrangian to the Eulerian description. Studying such different techniques is useful because it allows us to compare and develop further the various approximation techniques available in the Lagrangian formulation. We find that one has to solve the gravitational wave equation in the relativistic analysis, otherwise the corresponding Newtonian limit will necessarily contain spurious nonpropagating tensor artifacts at second order in the Eulerian frame. We also derive the magnetic part of the Weyl tensor in the Lagrangian frame, and find that it is not only excited by gravitational waves but also by tensor perturbations which are induced through the nonlinear frame dragging. We apply our findings to calculate for the first time the relativistic displacement field, up to second order, for a Λ CDM Universe in the presence of a local primordial non-Gaussian component. Finally, we also comment on recent claims about whether mass conservation in the Lagrangian frame is violated.

  20. Non-linear realizations of conformal symmetry and effective field theory for the pseudo-conformal universe

    SciTech Connect

    Hinterbichler, Kurt; Joyce, Austin; Khoury, Justin E-mail: joyceau@sas.upenn.edu

    2012-06-01

    The pseudo-conformal scenario is an alternative to inflation in which the early universe is described by an approximate conformal field theory on flat, Minkowski space. Some fields acquire a time-dependent expectation value, which breaks the flat space so(4,2) conformal algebra to its so(4,1) de Sitter subalgebra. As a result, weight-0 fields acquire a scale invariant spectrum of perturbations. The scenario is very general, and its essential features are determined by the symmetry breaking pattern, irrespective of the details of the underlying microphysics. In this paper, we apply the well-known coset technique to derive the most general effective lagrangian describing the Goldstone field and matter fields, consistent with the assumed symmetries. The resulting action captures the low energy dynamics of any pseudo-conformal realization, including the U(1)-invariant quartic model and the Galilean Genesis scenario. We also derive this lagrangian using an alternative method of curvature invariants, consisting of writing down geometric scalars in terms of the conformal mode. Using this general effective action, we compute the two-point function for the Goldstone and a fiducial weight-0 field, as well as some sample three-point functions involving these fields.

  1. Logarithmic conformal field theory: beyond an introduction

    NASA Astrophysics Data System (ADS)

    Creutzig, Thomas; Ridout, David

    2013-12-01

    This article aims to review a selection of central topics and examples in logarithmic conformal field theory. It begins with the remarkable observation of Cardy that the horizontal crossing probability of critical percolation may be computed analytically within the formalism of boundary conformal field theory. Cardy’s derivation relies on certain implicit assumptions which are shown to lead inexorably to indecomposable modules and logarithmic singularities in correlators. For this, a short introduction to the fusion algorithm of Nahm, Gaberdiel and Kausch is provided. While the percolation logarithmic conformal field theory is still not completely understood, there are several examples for which the formalism familiar from rational conformal field theory, including bulk partition functions, correlation functions, modular transformations, fusion rules and the Verlinde formula, has been successfully generalized. This is illustrated for three examples: the singlet model \\mathfrak {M} (1,2), related to the triplet model \\mathfrak {W} (1,2), symplectic fermions and the fermionic bc ghost system; the fractional level Wess-Zumino-Witten model based on \\widehat{\\mathfrak {sl}} \\left( 2 \\right) at k=-\\frac{1}{2}, related to the bosonic βγ ghost system; and the Wess-Zumino-Witten model for the Lie supergroup \\mathsf {GL} \\left( 1 {\\mid} 1 \\right), related to \\mathsf {SL} \\left( 2 {\\mid} 1 \\right) at k=-\\frac{1}{2} and 1, the Bershadsky-Polyakov algebra W_3^{(2)} and the Feigin-Semikhatov algebras W_n^{(2)}. These examples have been chosen because they represent the most accessible, and most useful, members of the three best-understood families of logarithmic conformal field theories. The logarithmic minimal models \\mathfrak {W} (q,p), the fractional level Wess-Zumino-Witten models, and the Wess-Zumino-Witten models on Lie supergroups (excluding \\mathsf {OSP} \\left( 1 {\\mid} 2n \\right)). In this review, the emphasis lies on the representation theory

  2. Scale invariance, conformality, and generalized free fields

    NASA Astrophysics Data System (ADS)

    Dymarsky, Anatoly; Farnsworth, Kara; Komargodski, Zohar; Luty, Markus A.; Prilepina, Valentina

    2016-02-01

    This paper addresses the question of whether there are 4D Lorentz invariant unitary quantum field theories with scale invariance but not conformal invariance. An important loophole in the arguments of Luty-Polchinski-Rattazzi and Dymarsky-Komargodski-Schwimmer-Theisen is that trace of the energy-momentum tensor T could be a generalized free field. In this paper we rule out this possibility. The key ingredient is the observation that a unitary theory with scale but not conformal invariance necessarily has a non-vanishing anomaly for global scale transformations. We show that this anomaly cannot be reproduced if T is a generalized free field unless the theory also contains a dimension-2 scalar operator. In the special case where such an operator is present it can be used to redefine ("improve") the energy-momentum tensor, and we show that there is at least one energy-momentum tensor that is not a generalized free field. In addition, we emphasize that, in general, large momentum limits of correlation functions cannot be understood from the leading terms of the coordinate space OPE. This invalidates a recent argument by Farnsworth-Luty-Prilepina (FLP). Despite the invalidity of the general argument of FLP, some of the techniques turn out to be useful in the present context.

  3. Shape dependence of entanglement entropy in conformal field theories

    NASA Astrophysics Data System (ADS)

    Faulkner, Thomas; Leigh, Robert G.; Parrikar, Onkar

    2016-04-01

    We study universal features in the shape dependence of entanglement entropy in the vacuum state of a conformal field theory (CFT) on R^{1,d-1} . We consider the entanglement entropy across a deformed planar or spherical entangling surface in terms of a perturbative expansion in the infinitesimal shape deformation. In particular, we focus on the second order term in this expansion, known as the entanglement density. This quantity is known to be non-positive by the strong-subadditivity property. We show from a purely field theory calculation that the non-local part of the entanglement density in any CFT is universal, and proportional to the coefficient C T appearing in the two-point function of stress tensors in that CFT. As applications of our result, we prove the conjectured universality of the corner term coefficient σ /C_T=π^2/24 in d = 3 CFTs, and the holographic Mezei formula for entanglement entropy across deformed spheres.

  4. Marginally Relevant Topics in Conformal Field Theories

    NASA Astrophysics Data System (ADS)

    Cleary, Kevin Francis

    We consider a set of topics in conformal field theory. We provide an example of a 4D theory that exhibits the Contino-Pomarol-Rattazzi mechanism, where breaking conformal symmetry by an almost marginal operator leads to a light pseudo-Goldstone boson, the dilaton, and a parametrically suppressed contribution to vacuum energy. We consider SUSY QCD at the edge of the conformal window and break conformal symmetry by weakly gauging a subgroup of the flavor symmetry. Using Seiberg duality we show that for a range of parameters the singlet meson in the dual theory reaches the unitarity bound, however, this theory does not have a stable vacuum. We stabilize the vacuum with soft breaking terms, compute the mass of the dilaton, and determine the range of parameters where the leading contribution to the dilaton mass is from the almost marginal coupling. We also weigh in on a widely held belief that increasing bounds on the gluino mass, which feeds down to the stop mass through renormalization group running, are making a light stop increasingly unlikely. Here we present a counter-example. We examine the case of the Minimal Composite Supersymmetric Standard Model which has a light composite stop. The large anomalous dimension of the stop from strong dynamics pushes the stop mass toward a quasi-fixed point in the infrared, which is smaller than standard estimates by a factor of a large logarithm. The gluino can be about three times heavier than the stop, which is comparable to hierarchy achieved with supersoft Dirac gluino masses. Thus, in this class of models, a heavy gluino is not necessarily indicative of a heavy stop.

  5. Entanglement entropy in warped conformal field theories

    NASA Astrophysics Data System (ADS)

    Castro, Alejandra; Hofman, Diego M.; Iqbal, Nabil

    2016-02-01

    We present a detailed discussion of entanglement entropy in (1+1)-dimensional Warped Conformal Field Theories (WCFTs). We implement the Rindler method to evaluate entanglement and Renyi entropies for a single interval and along the way we interpret our results in terms of twist field correlation functions. Holographically a WCFT can be described in terms of Lower Spin Gravity, a SL (2, ℝ) × U (1) Chern-Simons theory in three dimensions. We show how to obtain the universal field theory results for entanglement in a WCFT via holography. For the geometrical description of the theory we introduce the concept of geodesic and massive point particles in the warped geometry associated to Lower Spin Gravity. In the Chern-Simons description we evaluate the appropriate Wilson line that captures the dynamics of a massive particle.

  6. Dual of the Janus solution: An interface conformal field theory

    NASA Astrophysics Data System (ADS)

    Clark, A. B.; Freedman, D. Z.; Karch, A.; Schnabl, M.

    2005-03-01

    We propose and study a specific gauge theory dual of the smooth, nonsupersymmetric (and apparently stable) Janus solution of Type IIB supergravity found in Bak et al. [J. High Energy Phys., JHEPFG, 1029-8479 05 (2003) 072]. The dual field theory is N=4 SYM theory on two half-spaces separated by a planar interface with different coupling constants in each half-space. We assume that the position dependent coupling multiplies the operator L' which is the fourth descendent of the primary TrX{IXJ} and closely related to the N=4 Lagrangian density. At the classical level supersymmetry is broken explicitly, but SO(3,2) conformal symmetry is preserved. We use conformal perturbation theory to study various correlation functions to first and second order in the discontinuity of g2YM, confirming quantum level conformal symmetry. Certain quantities such as the vacuum expectation value are protected to all orders in g2YMN, and we find perfect agreement between the weak coupling value in the gauge theory and the strong coupling gravity result. SO(3,2) symmetry requires vanishing vacuum energy, =0, and this is confirmed in first order in the discontinuity.

  7. Transformations among large c conformal field theories

    NASA Astrophysics Data System (ADS)

    Jankiewicz, Marcin; Kephart, Thomas W.

    2006-06-01

    We show that there is a set of transformations that relates all of the 24 dimensional even self-dual (Niemeier) lattices, and also leads to non-lattice objects some of which can perhaps be interpreted as a basis for the construction of holomorphic conformal field theory. In the second part of this paper, we extend our observations to higher-dimensional conformal field theories build on extremal partition functions, where we generate c=24k theories. We argue that there exists generalizations of the c=24 models based on Niemeier lattices and of the non-Niemeier spin-1 theories. The extremal cases have spectra decomposable into the irreducible representations of the Fischer-Griess Monster. This additional symmetry leads us to conjecture that these extremal theories, as well as the higher-dimensional analogs of the group lattice bases Niemeiers, will eventually yield to a full construction of their associated CFTs. We observe interesting periodicities in the coefficients of extremal partition functions and characters of the extremal vertex operator algebras.

  8. Introduction to string theory and conformal field theory

    SciTech Connect

    Belavin, A. A. Tarnopolsky, G. M.

    2010-05-15

    A concise survey of noncritical string theory and two-dimensional conformal field theory is presented. A detailed derivation of a conformal anomaly and the definition and general properties of conformal field theory are given. Minimal string theory, which is a special version of the theory, is considered. Expressions for the string susceptibility and gravitational dimensions are derived.

  9. Near horizon extremal geometry perturbations: dynamical field perturbations vs. parametric variations

    NASA Astrophysics Data System (ADS)

    Hajian, K.; Seraj, A.; Sheikh-Jabbari, M. M.

    2014-10-01

    In [1] we formulated and derived the three universal laws governing Near Horizon Extremal Geometries (NHEG). In this work we focus on the Entropy Perturbation Law (EPL) which, similarly to the first law of black hole thermodynamics, relates perturbations of the charges labeling perturbations around a given NHEG to the corresponding entropy perturbation. We show that field perturbations governed by the linearized equations of motion and symmetry conditions which we carefully specify, satisfy the EPL. We also show that these perturbations are limited to those coming from difference of two NHEG solutions (i.e. variations on the NHEG solution parameter space). Our analysis and discussions shed light on the "no-dynamics" statements of [2, 3].

  10. R{sup 2}-inflation with conformal SM Higgs field

    SciTech Connect

    Gorbunov, Dmitry; Tokareva, Anna E-mail: tokareva@ms2.inr.ac.ru

    2013-12-01

    We introduce conformal coupling of the Standard Model Higgs field to gravity and discuss the subsequent modification of R{sup 2}-inflation. The main observation is a lower temperature of reheating which happens mostly through scalaron decays into gluons due to the conformal (trace) anomaly. This modifies all predictions of the original R{sup 2}-inflation. To the next-to-leading order in slow roll parameters we calculate amplitudes and indices of scalar and tensor perturbations produced at inflation. The results are compared to the next-to-leading order predictions of R{sup 2}-inflation with minimally coupled Higgs field and of Higgs-inflation. We discuss additional features in gravity wave signal that may help to distinguish the proposed variant of R{sup 2}-inflation. Remarkably, the features are expected in the region available for study at future experiments like BBO and DECIGO. Finally, we check that (meta)stability of electroweak vacuum in the cosmological model is consistent with recent results of searches for the Higgs boson at LHC.

  11. Conformal perturbation of off-critical correlators in the 3D Ising universality class

    NASA Astrophysics Data System (ADS)

    Caselle, M.; Costagliola, G.; Magnoli, N.

    2016-07-01

    Thanks to the impressive progress of conformal bootstrap methods we have now very precise estimates of both scaling dimensions and operator product expansion coefficients for several 3D universality classes. We show how to use this information to obtain similarly precise estimates for off-critical correlators using conformal perturbation. We discuss in particular the ⟨σ (r )σ (0 )⟩ , ⟨ɛ (r )ɛ (0 )⟩ and ⟨σ (r )ɛ (0 )⟩ two-point functions in the high and low temperature regimes of the 3D Ising model and evaluate the leading and next to leading terms in the s =trΔt expansion, where t is the reduced temperature. Our results for ⟨σ (r )σ (0 )⟩ agree both with Monte Carlo simulations and with a set of experimental estimates of the critical scattering function.

  12. Plasma-satellite interaction driven magnetic field perturbations

    SciTech Connect

    Saeed-ur-Rehman; Marchand, Richard

    2014-09-15

    We report the first fully kinetic quantitative estimate of magnetic field perturbations caused by the interaction of a spacecraft with space environment. Such perturbations could affect measurements of geophysical magnetic fields made with very sensitive magnetometers on-board satellites. Our approach is illustrated with a calculation of perturbed magnetic fields near the recently launched Swarm satellites. In this case, magnetic field perturbations do not exceed 20 pT, and they are below the sensitivity threshold of the on-board magnetometers. Anticipating future missions in which satellites and instruments would be subject to more intense solar UV radiation, however, it appears that magnetic field perturbations associated with satellite interaction with space environment, might approach or exceed instruments' sensitivity thresholds.

  13. Relative entropies in conformal field theory.

    PubMed

    Lashkari, Nima

    2014-08-01

    Relative entropy is a measure of distinguishability for quantum states, and it plays a central role in quantum information theory. The family of Renyi entropies generalizes to Renyi relative entropies that include, as special cases, most entropy measures used in quantum information theory. We construct a Euclidean path-integral approach to Renyi relative entropies in conformal field theory, then compute the fidelity and the relative entropy of states in one spatial dimension at zero and finite temperature using a replica trick. In contrast to the entanglement entropy, the relative entropy is free of ultraviolet divergences, and is obtained as a limit of certain correlation functions. The relative entropy of two states provides an upper bound on their trace distance. PMID:25126908

  14. Suppression of edge-localized modes by magnetic field perturbations

    SciTech Connect

    Kleva, Robert G.; Guzdar, Parvez N.

    2010-11-15

    Transport bursts in simulations of edge-localized modes (ELMs) in tokamaks are suppressed by the application of magnetic field perturbations. The amplitude of the applied magnetic field perturbations is characterized by a stochasticity parameter S. When S>1, magnetic flux surfaces are destroyed and the magnetic field lines diffuse in minor radius. As S increases in the simulations, the magnitude of the ELM bursts decreases. The size of bursts is reduced to a very small value while S is still less than unity and most of the magnetic flux surfaces are still preserved. Magnetic field line stochasticity is not a requirement for the stabilization of ELMs by the magnetic field perturbations. The magnetic field perturbations act by suppressing the growth of the resistive ballooning instability that underlies the ELM bursts.

  15. On conformal field theories with extremal values

    NASA Astrophysics Data System (ADS)

    Zhiboedov, Alexander

    2014-04-01

    Unitary conformal field theories (CFTs) are believed to have positive (non-negative) energy correlators. Energy correlators are universal observables in higher-dimensional CFTs built out of integrated Wightman functions of the stress-energy tensor. We analyze energy correlators in parity invariant four-dimensional CFTs. The goal is to use the positivity of energy correlators to further constrain unitary CFTs. It is known that the positivity of the simplest one-point energy correlator implies that where a and c are the Weyl anomaly coefficients. We use the positivity of higher point energy correlators to show that CFTs with extremal values of have trivial scattering observables. More precisely, for and all energy correlators are fixed to be the ones of the free boson and the free vector theory correspondingly. Similarly, we show that the positivity and finiteness of energy correlators together imply that the three-point function of the stress tensor in a CFT cannot be proportional to the one in the theory of free boson, free fermion or free vector field.

  16. Perturbative analysis of multiple-field cosmological inflation

    SciTech Connect

    Lahiri, Joydev . E-mail: gautam@theory.saha.ernet.in

    2006-04-15

    We develop a general formalism for analyzing linear perturbations in multiple-field cosmological inflation based on the gauge-ready approach. Our inflationary model consists of an arbitrary number of scalar fields with non-minimal kinetic terms. We solve the equations for scalar- and tensor-type perturbations during inflation to the first order in slow roll, and then obtain the super-horizon solutions for adiabatic and isocurvature perturbations after inflation. Analytic expressions for power-spectra and spectral indices arising from multiple-field inflation are presented.

  17. Logarithmic conformal field theory: a lattice approach

    NASA Astrophysics Data System (ADS)

    Gainutdinov, A. M.; Jacobsen, J. L.; Read, N.; Saleur, H.; Vasseur, R.

    2013-12-01

    Logarithmic conformal field theories (LCFT) play a key role, for instance, in the description of critical geometrical problems (percolation, self-avoiding walks, etc), or of critical points in several classes of disordered systems (transition between plateaux in the integer and spin quantum Hall effects). Much progress in their understanding has been obtained by studying algebraic features of their lattice regularizations. For reasons which are not entirely understood, the non-semi-simple associative algebras underlying these lattice models—such as the Temperley-Lieb algebra or the blob algebra—indeed exhibit, in finite size, properties that are in full correspondence with those of their continuum limits. This applies not only to the structure of indecomposable modules, but also to fusion rules, and provides an ‘experimental’ way of measuring couplings, such as the ‘number b’ quantifying the logarithmic coupling of the stress-energy tensor with its partner. Most results obtained so far have concerned boundary LCFTs and the associated indecomposability in the chiral sector. While the bulk case is considerably more involved (mixing in general left and right moving sectors), progress has also recently been made in this direction, uncovering fascinating structures. This study provides a short general review of our work in this area.

  18. Conformational Mobility in Cytochrome P450 3A4 Explored by Pressure-Perturbation EPR Spectroscopy.

    PubMed

    Davydov, Dmitri R; Yang, Zhongyu; Davydova, Nadezhda; Halpert, James R; Hubbell, Wayne L

    2016-04-12

    We used high hydrostatic pressure as a tool for exploring the conformational landscape of human cytochrome P450 3A4 (CYP3A4) by electron paramagnetic resonance and fluorescence spectroscopy. Site-directed incorporation of a luminescence resonance energy transfer donor-acceptor pair allowed us to identify a pressure-dependent equilibrium between two states of the enzyme, where an increase in pressure increased the spatial separation between the two distantly located fluorophores. This transition is characterized by volume change (ΔV°) and P1/2 values of -36.8 ± 5.0 mL/mol and 1.45 ± 0.33 kbar, respectively, which corresponds to a Keq° of 0.13 ± 0.06, so that only 15% of the enzyme adopts the pressure-promoted conformation at ambient pressure. This pressure-promoted displacement of the equilibrium is eliminated by the addition of testosterone, an allosteric activator. Using site-directed spin labeling, we demonstrated that the pressure- and testosterone-sensitive transition is also revealed by pressure-induced changes in the electron paramagnetic resonance spectra of a nitroxide side chain placed at position 85 or 409 of the enzyme. Furthermore, we observed a pressure-induced displacement of the emission maxima of a solvatochromic fluorophore (7-diethylamino-3-((((2-maleimidyl)ethyl)amino)carbonyl) coumarin) placed at the same positions, which suggests a relocation to a more polar environment. Taken together, the results reveal an effector-dependent conformational equilibrium between open and closed states of CYP3A4 that involves a pronounced change at the interface between the region of α-helices A/A' and the meander loop of the enzyme, where residues 85 and 409 are located. Our study demonstrates the high potential of pressure-perturbation strategies for studying protein conformational landscapes. PMID:27074675

  19. Central charge bounds in 4D conformal field theory

    SciTech Connect

    Rattazzi, Riccardo; Vichi, Alessandro; Rychkov, Slava

    2011-02-15

    We derive model-independent lower bounds on the stress tensor central charge C{sub T} in terms of the operator content of a 4-dimensional conformal field theory. More precisely, C{sub T} is bounded from below by a universal function of the dimensions of the lowest and second-lowest scalars present in the conformal field theory. The method uses the crossing symmetry constraint of the 4-point function, analyzed by means of the conformal block decomposition.

  20. Scalar field conformally coupled to a charged BTZ black hole

    NASA Astrophysics Data System (ADS)

    Valtancoli, P.

    2016-06-01

    We study the Klein-Gordon equation of a scalar field conformally coupled to a charged BTZ black hole. The background metric is obtained by coupling a non-linear and conformal invariant Maxwell field to (2 + 1) gravity. We show that the radial part is generally solved by a Heun function and, in the pure gravity limit, by a hypergeometric function.

  1. Conformal field theories, representations and lattice constructions

    NASA Astrophysics Data System (ADS)

    Dolan, L.; Goddard, P.; Montague, P.

    1996-07-01

    An account is given of the structure and representations of chiral bosonic meromorphic conformal field theories (CFT's), and, in particular, the conditions under which such a CFT may be extended by a representation to form a new theory. This general approach is illustrated by considering the untwisted and Z 2-twisted theories, ℋ( Λ) andtilde H(Λ ) respectively, which may be constructed from a suitable even Euclidean lattice Λ. Similarly, one may construct latticesΛ _C andtilde Λ _C by analogous constructions from a doubly-even binary codeC. In the case whenC is self-dual, the corresponding lattices are also. Similarly, ℋ( Λ) andtilde H(Λ ) are self-dual if and only if Λ is. We show thatH(Λ _C ) has a natural “triality” structure, which induces an isomorphismH(tilde Λ _C ) ≡tilde H(Λ _C ) and also a triality structure ontilde H(tilde Λ _C ). ForC the Golay code,tilde Λ _C is the Leech lattice, and the triality ontilde H(tilde Λ _C ) is the symmetry which extends the natural action of (an extension of) Conway's group on this theory to the Monster, so setting triality and Frenkel, Lepowsky and Meurman's construction of the natural Monster module in a more general context. The results also serve to shed some light on the classification of self-dual CFT's. We find that of the 48 theories ℋ( Λ) andtilde H(Λ ) with central charge 24 that there are 39 distinct ones, and further that all 9 coincidences are accounted for by the isomorphism detailed above, induced by the existence of a doubly-even self-dual binary code.

  2. Finite field-dependent symmetries in perturbative quantum gravity

    NASA Astrophysics Data System (ADS)

    Upadhyay, Sudhaker

    2014-01-01

    In this paper we discuss the absolutely anticommuting nilpotent symmetries for perturbative quantum gravity in general curved spacetime in linear and non-linear gauges. Further, we analyze the finite field-dependent BRST (FFBRST) transformation for perturbative quantum gravity in general curved spacetime. The FFBRST transformation changes the gauge-fixing and ghost parts of the perturbative quantum gravity within functional integration. However, the operation of such symmetry transformation on the generating functional of perturbative quantum gravity does not affect the theory on physical ground. The FFBRST transformation with appropriate choices of finite BRST parameter connects non-linear Curci-Ferrari and Landau gauges of perturbative quantum gravity. The validity of the results is also established at quantum level using Batalin-Vilkovisky (BV) formulation.

  3. Perturbations of matter fields in the second-order gauge-invariant cosmological perturbation theory

    NASA Astrophysics Data System (ADS)

    Nakamura, Kouji

    2009-12-01

    To show that the general framework of the second-order gauge-invariant perturbation theory developed by K. Nakamura [Prog. Theor. Phys. 110, 723 (2003)PTPKAV0033-068X10.1143/PTP.110.723; Prog. Theor. Phys. 113, 481 (2005)PTPKAV0033-068X10.1143/PTP.113.481] is applicable to a wide class of cosmological situations, some formulas for the perturbations of the matter fields are summarized within the framework of the second-order gauge-invariant cosmological perturbation theory in a four-dimensional homogeneous isotropic universe, which is developed in Prog. Theor. Phys. 117, 17 (2007)PTPKAV0033-068X10.1143/PTP.117.17. We derive the formulas for the perturbations of the energy-momentum tensors and equations of motion for a perfect fluid, an imperfect fluid, and a single scalar field, and show that all equations are derived in terms of gauge-invariant variables without any gauge fixing. Through these formulas, we may say that the decomposition formulas for the perturbations of any tensor field into gauge-invariant and gauge-variant parts, which are proposed in the above papers, are universal.

  4. Carbon nanotube bundles under electric field perturbations

    NASA Astrophysics Data System (ADS)

    Hammes, I.; Latgé, A.

    2012-03-01

    Here we address the important role played by electric fields applied in carbon nanotube bundles in providing convenient scenarios for their use in electronic devices. We show that a gap modulation may be derived depending on the bundle configuration and the details of the applied field configuration. The system is described by a tight binding Hamiltonian and the Green function formalism is used to calculate the local density of states. Small bundles were used to validate our model on the basis of ab initio calculations. Further analysis shows that the number of tubes, geometrical configuration details and field intensities may be controlled to tune the electronic structure close to the Fermi energy, envisaging atomic-scale devices.

  5. Perturbations of the Richardson number field by gravity waves

    NASA Technical Reports Server (NTRS)

    Wurtele, M. G.; Sharman, R. D.

    1985-01-01

    An analytic solution is presented for a stratified fluid of arbitrary constant Richardson number. By computer aided analysis the perturbation fields, including that of the Richardson number can be calculated. The results of the linear analytic model were compared with nonlinear simulations, leading to the following conclusions: (1) the perturbations in the Richardson number field, when small, are produced primarily by the perturbations of the shear; (2) perturbations of in the Richardson number field, even when small, are not symmetric, the increase being significantly larger than the decrease (the linear analytic solution and the nonlinear simulations both confirm this result); (3) as the perturbations grow, this asymmetry increases, but more so in the nonlinear simulations than in the linear analysis; (4) for large perturbations of the shear flow, the static stability, as represented by N2, is the dominating mechanism, becoming zero or negative, and producing convective overturning; and (5) the convectional measure of linearity in lee wave theory, NH/U, is no longer the critical parameter (it is suggested that (H/u sub 0) (du sub 0/dz) takes on this role in a shearing flow).

  6. Keep on Moving: Discovering and Perturbing the Conformational Dynamics of Enzymes

    PubMed Central

    2015-01-01

    Conspectus Because living organisms are in constant motion, the word “dynamics” can hold many meanings to biologists. Here we focus specifically on the conformational changes that occur in proteins and how studying these protein dynamics may provide insights into enzymatic catalysis. Advances in integrating techniques such as X-ray crystallography, nuclear magnetic resonance, and electron cryomicroscopy (cryo EM) allow us to model the dominant structures and exchange rates for many proteins and protein complexes. For proteins amenable to atomic resolution techniques, the major questions shift from simply describing the motions to discovering their role in function. Concurrently, there is an increasing need for using perturbations to test predictive models of dynamics–function relationships. Examples are the catalytic cycles of dihydrofolate reductase (DHFR) and cyclophilin A (CypA). In DHFR, mutations that alter the ability of the active site to sample productive higher energy states on the millisecond time scale reduce the rate of hydride transfer significantly. Recently identified rescue mutations restore function, but the mechanism by which they do so remains unclear. The exact role of any changes in the dynamics remains an open question. For CypA, a network of side chains that exchange between two conformations is critical for catalysis. Mutations that lock the network in one state also reduce catalytic activity. A further understanding of enzyme dynamics of well-studied enzymes such as dihydrofolate reductase and cyclophilin A will lead to improvement in ability to modulate the functions of computationally designed enzymes and large macromolecular machines. In designed enzymes, directed evolution experiments increase catalytic rates. Detailed X-ray studies suggest that these mutations likely limit the conformational space explored by residues in the active site. For proteins where atomic resolution information is currently inaccessible, other techniques

  7. Finite field-dependent symmetries in perturbative quantum gravity

    SciTech Connect

    Upadhyay, Sudhaker

    2014-01-15

    In this paper we discuss the absolutely anticommuting nilpotent symmetries for perturbative quantum gravity in general curved spacetime in linear and non-linear gauges. Further, we analyze the finite field-dependent BRST (FFBRST) transformation for perturbative quantum gravity in general curved spacetime. The FFBRST transformation changes the gauge-fixing and ghost parts of the perturbative quantum gravity within functional integration. However, the operation of such symmetry transformation on the generating functional of perturbative quantum gravity does not affect the theory on physical ground. The FFBRST transformation with appropriate choices of finite BRST parameter connects non-linear Curci–Ferrari and Landau gauges of perturbative quantum gravity. The validity of the results is also established at quantum level using Batalin–Vilkovisky (BV) formulation. -- Highlights: •The perturbative quantum gravity is treated as gauge theory. •BRST and anti-BRST transformations are developed in linear and non-linear gauges. •BRST transformation is generalized by making it finite and field dependent. •Connection between linear and non-linear gauges is established. •Using BV formulation the results are established at quantum level also.

  8. Approach to exact solutions of cosmological perturbations: Tachyon field inflation

    NASA Astrophysics Data System (ADS)

    Herrera, Ramón; Pérez, Roberto G.

    2016-03-01

    An inflationary universe scenario in the context of a tachyon field is studied. This study is carried out using an ansatz for the effective potential of cosmological perturbations U (η ). We describe in great detail the analytical solutions of the scalar and tensor perturbations for two different Ansätze for the effective potential of cosmological perturbations: Easther's model and an effective potential similar to power-law inflation. Also, we find from the background equations that the effective tachyonic potentials V (φ ) in both models satisfy the properties of a tachyonic potential. We consider the recent data from the Planck to constrain the parameters in our effective potential generating the cosmological perturbations.

  9. Bianchi type-I models with conformally invariant scalar field

    SciTech Connect

    Accioly, A.J.; Vaidya, A.N.; Som, M.M.

    1983-05-15

    The solutions of the Einstein equations with the trace-free energy-momentum tensor of conformally invariant scalar field as source are obtained in a spatially homogeneous anisotropic space-time. Some interesting features of the solutions are discussed.

  10. Fast ion loss associated with perturbed field by resonant magnetic perturbation coils in KSTAR

    NASA Astrophysics Data System (ADS)

    Kim, Jun Young; Kim, Junghee; Rhee, Tongnyeol; Yoon, S. W.; Park, G. Y.; Jeon, Y. M.; Isobe, M.; Shimizu, A.; Ogawa, K.; Park, J.-K.; Garcia-Munoz, M.

    2013-10-01

    Resonant magnetic perturbation (RMP) is the most promising strategies for ELM mitigation/suppression. However, it has been found through the modeling and the experiments that RMP for the ELM mitigation can enhance the toroidally localized fast ion loss. During KSTAR experimental campaigns in 2011 and 2012, sudden increase or decrease of the fast ion loss has been observed by the scintillator-based fast ion loss detector (FILD) when the RMP is applied. Three-dimensional perturbed magnetic field by RMP coil in vacuum is calculated by Biot-Savart's law embedded in the Lorentz orbit code (LORBIT). The LORBIT code which is based on gyro-orbit following motion has been used for the simulation of the three-dimensional fast ion trajectories in presence of non-axisymmetric magnetic perturbation. It seems the measured fast ion loss rate at the localized position depends on not only the RMP field configuration but also the plasma profile such as safety factor and so on, varying the ratio between radial drift and stochastization of the fat-ion orbits. The simulation results of fast ion orbit under magnetic perturbation w/ and w/o plasma responses will be presented and compared with KSTAR FILD measurement results in various cases.

  11. Missile launch detection electric field perturbation experiment. Final report

    SciTech Connect

    Kane, R.J.; Rynne, T.M.

    1993-04-28

    The Lawrence Livermore National Laboratory and SARA Inc. participated in the ATMD missile launch activities that occurred at WSMR during January 1993. LLNL and SARA deployed sensors for monitoring of basic phenomena. An attempt was made to measure perturbations of the earth geo-potential during the launch of a Lance missile. The occurrence of the perturbation is expected from the conducting body of the missile and the exhaust plume. A set of voltage-probe antennas were used to monitor the local electric field perturbation from the launch at ranges of approximately 1 km. Examination of the data acquired during the launch period failed to show identifiable correlation of the field variations with the launch event. Three reasons are ascribed to this lack of event data: (1) The electric field potential variations have a limited spatial correlation length - the fields measured in one region have little correlation to measurements made at distances of a kilometer away. The potential variations are related to localized atmospheric disturbances and are generally unpredictable. A value for the spatial correlation length is also not known. (2) The conductivity of the plume and missile body are not adequate to produce a field perturbation of adequate magnitude. Phenomena related to the exhaust plume and missile may exist and be outside of the collection range of the equipment employed for these measurements. (3) The presence of 60 Hz power line noise was of sufficient magnitude to irreversibly contaminate measurements.

  12. Waterfall field in hybrid inflation and curvature perturbation

    SciTech Connect

    Gong, Jinn-Ouk; Sasaki, Misao E-mail: misao@yukawa.kyoto-u.ac.jp

    2011-03-01

    We study carefully the contribution of the waterfall field to the curvature perturbation at the end of hybrid inflation. In particular we clarify the parameter dependence analytically under reasonable assumptions on the model parameters. After calculating the mode function of the waterfall field, we use the δN formalism and confirm the previously obtained result that the power spectrum is very blue with the index 4 and is absolutely negligible on large scales. However, we also find that the resulting curvature perturbation is highly non-Gaussian and hence we calculate the bispectrum. We find that the bispectrum is at leading order independent of momentum and exhibits its peak at the equilateral limit, though it is unobservably small on large scales. We also present the one-point probability distribution function of the curvature perturbation.

  13. Perturbation Theory of Massive Yang-Mills Fields

    DOE R&D Accomplishments Database

    Veltman, M.

    1968-08-01

    Perturbation theory of massive Yang-Mills fields is investigated with the help of the Bell-Treiman transformation. Diagrams containing one closed loop are shown to be convergent if there are more than four external vector boson lines. The investigation presented does not exclude the possibility that the theory is renormalizable.

  14. Conformal symmetry limit of QED and QCD and identities between perturbative contributions to deep-inelastic scattering sum rules

    NASA Astrophysics Data System (ADS)

    Kataev, A. L.

    2014-02-01

    Conformal symmetry-based relations between concrete perturbative QED and QCD approximations for the Bjorken , the Ellis-Jaffe sum rules of polarized lepton- nucleon deep-inelastic scattering (DIS), the Gross-Llewellyn Smith sum rules of neutrino-nucleon DIS, and for the Adler functions of axial-vector and vector channels are derived. They result from the application of the operator product expansion to three triangle Green functions, constructed from the non-singlet axial-vector, and two vector currents, the singlet axial-vector and two non-singlet vector currents and the non-singlet axial-vector, vector and singlet vector currents in the limit, when the conformal symmetry of the gauge models with fermions is considered unbroken. We specify the perturbative conditions for this symmetry to be valid in the case of the U(1) and SU( N c) models. The all-order perturbative identity following from the conformal invariant limit between the concrete contributions to the Bjorken, the Ellis-Jaffe and the Gross-Llewellyn Smith sum rules is proved. The analytical and numerical O( α 4) and conformal symmetry based approximations for these sum rules and for the Adler function of the non-singlet vector currents are summarized. Possible theoretical applications of the results presented are discussed.

  15. The interaction between plasma rotation, stochastic fields and tearing mode excitation by external perturbation fields

    NASA Astrophysics Data System (ADS)

    DeBock, M. F. M.; Classen, I. G. J.; Busch, C.; Jaspers, R. J. E.; Koslowski, H. R.; Unterberg, B.; TEXTOR Team

    2008-01-01

    For fusion reactors, based on the principle of magnetic confinement, it is important to avoid so-called magnetic islands or tearing modes. They reduce confinement and can be the cause of major disruptions. One class of magnetic islands is that of the perturbation field driven modes. This perturbation field can, for example, be the intrinsic error field. Theoretical work predicts a strong relationship between plasma rotation and the excitation of perturbation field modes. Experimentally, the theory on mode excitation and plasma rotation has been confirmed on several tokamaks. In those experiments, however, the control over the plasma rotation velocity and direction, and over the externally applied perturbation field was limited. In this paper experiments are presented that were carried out at the TEXTOR tokamak. Two tangential neutral beam injectors and a set of helical perturbation coils, called the dynamic ergodic divertor (DED), provide control over both the plasma rotation and the external perturbation field in TEXTOR. This made it possible to set up a series of experiments to test the theory on mode excitation and plasma rotation in detail. The perturbation field induced by the DED not only excites magnetic islands, it also sets up a layer near the plasma boundary where the magnetic field is stochastic. It will be shown that this stochastic field alters both the rotational response of the plasma on the perturbation field and the threshold for mode excitation. It therefore has to be included in an extended theory on mode excitation.

  16. Coupling structure of multi-field primordial perturbations

    SciTech Connect

    Gao, Xian

    2013-10-01

    We investigate the coupling relations among perturbations in general multi-field models. We derived the equations of motion for both background and perturbations in a general basis. Within this formalism, we revisit the construction of kinematic orthogonal normal vectors using the successive time derivatives of the background field velocity. We show that the coupling relations among modes in this kinematic basis can be reduced, by employing the background equations of motion for the scalar fields and their high order time derivatives. There are two typical features in the field space: inflationary trajectory and geometry of the potential. Correspondingly, the couplings among modes fall into two categories: one is controlled only by the kinematic quantities, the other involves high order derivatives of the potential. Remarkably, the couplings of the first category, i.e. controlled by the kinematic quantities only, show a ''chain'' structure. That is, each mode is only coupled to its two neighbour modes.

  17. New method of applying conformal group to quantum fields

    NASA Astrophysics Data System (ADS)

    Han, Lei; Wang, Hai-Jun

    2015-09-01

    Most of previous work on applying the conformal group to quantum fields has emphasized its invariant aspects, whereas in this paper we find that the conformal group can give us running quantum fields, with some constants, vertex and Green functions running, compatible with the scaling properties of renormalization group method (RGM). We start with the renormalization group equation (RGE), in which the differential operator happens to be a generator of the conformal group, named dilatation operator. In addition we link the operator/spatial representation and unitary/spinor representation of the conformal group by inquiring a conformal-invariant interaction vertex mimicking the similar process of Lorentz transformation applied to Dirac equation. By this kind of application, we find out that quite a few interaction vertices are separately invariant under certain transformations (generators) of the conformal group. The significance of these transformations and vertices is explained. Using a particular generator of the conformal group, we suggest a new equation analogous to RGE which may lead a system to evolve from asymptotic regime to nonperturbative regime, in contrast to the effect of the conventional RGE from nonperturbative regime to asymptotic regime. Supported by NSFC (91227114)

  18. Understanding conformal field theory through parafermions and Chern Simons theory

    SciTech Connect

    Hotes, S.A.

    1992-11-19

    Conformal field theories comprise a vast class of exactly solvable two dimensional quantum field theories. Conformal theories with an enlarged symmetry group, the current algebra symmetry, axe a key ingredient to possible string compactification models. The following work explores a Lagrangian approach to these theories. In the first part of this thesis, a large class of conformal theories, the so-called coset models, are derived semi-classically from a gauged version Of the Wess-Zumino-Witten functional. A non-local field transformation to the parafermionic field description is employed in the quantization procedure. Classically, these parafermionic fields satisfy non-trivial Poisson brackets, providing insight into the fractional spin nature of the conformal theory. The W-algebra symmetry is shown to appear naturally in this approach. In the second part of this thesis, the connection between the fusion algebra structure of Wess-Zumino-Witten models and the quantization of the Chern-Simons action on the torus is made explicit. The modular properties of the conformal model are also derived in this context, giving a natural demonstration of the Verlinde conjecture. The effects of background gauge fields and monopoles are also discussed.

  19. Irreversibility and higher-spin conformal field theory

    NASA Astrophysics Data System (ADS)

    Anselmi, Damiano

    2000-08-01

    I discuss the properties of the central charges c and a for higher-derivative and higher-spin theories (spin 2 included). Ordinary gravity does not admit a straightforward identification of c and a in the trace anomaly, because it is not conformal. On the other hand, higher-derivative theories can be conformal, but have negative c and a. A third possibility is to consider higher-spin conformal field theories. They are not unitary, but have a variety of interesting properties. Bosonic conformal tensors have a positive-definite action, equal to the square of a field strength, and a higher-derivative gauge invariance. There exists a conserved spin-2 current (not the canonical stress tensor) defining positive central charges c and a. I calculate the values of c and a and study the operator-product structure. Higher-spin conformal spinors have no gauge invariance, admit a standard definition of c and a and can be coupled to Abelian and non-Abelian gauge fields in a renormalizable way. At the quantum level, they contribute to the one-loop beta function with the same sign as ordinary matter, admit a conformal window and non-trivial interacting fixed points. There are composite operators of high spin and low dimension, which violate the Ferrara-Gatto-Grillo theorem. Finally, other theories, such as conformal antisymmetric tensors, exhibit more severe internal problems. This research is motivated by the idea that fundamental quantum field theories should be renormalization-group (RG) interpolations between ultraviolet and infrared conformal fixed points, and quantum irreversibility should be a general principle of nature.

  20. Proton Radiography as an electromagnetic field and density perturbation diagnostic

    SciTech Connect

    Mackinnon, A; Patel, P; Town, R; Edwards, M; Phillips, T; Lerner, S; Price, D; Hicks, D; Key, M; Hatchett, S; Wilks, S; King, J; Snavely, R; Freeman, R; Boehlly, T; Koenig, M; Martinolli, E; Lepape, S; Benuzzi-Mounaix, A; Audebert, P; Gauthier, J; Borghesi, M; Romagnani, L; Toncian, T; Pretzler, G; Willi, O

    2004-04-15

    Laser driven proton beams have been used to diagnose transient fields and density perturbations in laser produced plasmas. Grid deflectometry techniques have been applied to proton radiography to obtain precise measurements of proton beam angles caused by electromagnetic fields in laser produced plasmas. Application of proton radiography to laser driven implosions has demonstrated that density conditions in compressed media can be diagnosed with MeV protons. This data has shown that proton radiography can provide unique insight into transient electromagnetic fields in super critical density plasmas and provide a density perturbation diagnostics in compressed matter . PACS numbers: 52.50.Jm, 52.40.Nk, 52.40.Mj, 52.70.Kz

  1. Adler function and Bjorken polarized sum rule: Perturbation expansions in powers of the S U (Nc) conformal anomaly and studies of the conformal symmetry limit

    NASA Astrophysics Data System (ADS)

    Cvetič, Gorazd; Kataev, A. L.

    2016-07-01

    We consider a new form of analytical perturbation theory expansion in the massless S U (Nc) theory, for the nonsinglet part of the e+e--annihilation to hadrons Adler function Dn s and of the Bjorken sum rule of the polarized lepton-hadron deep-inelastic scattering Cns B j p, and demonstrate its validity at the O (αs4)-level at least. It is a two-fold series in powers of the conformal anomaly and of S U (Nc) coupling αs. Explicit expressions are obtained for the {β }-expanded perturbation coefficients at O (αs4) level in MS ¯ scheme, for both considered physical quantities. Comparisons of the terms in the {β }-expanded coefficients are made with the corresponding terms obtained by using extra gluino degrees of freedom, or skeleton-motivated expansion, or Rδ-scheme motivated expansion in the Principle of Maximal Conformality. Relations between terms of the {β }-expansion for the Dn s- and Cns B j p-functions, which follow from the conformal symmetry limit and its violation, are presented. The relevance to the possible new analyses of the experimental data for the Adler function and Bjorken sum rule is discussed.

  2. Unitary Fermi Gas, ɛ Expansion, and Nonrelativistic Conformal Field Theories

    NASA Astrophysics Data System (ADS)

    Nishida, Yusuke; Son, Dam Thanh

    We review theoretical aspects of unitary Fermi gas (UFG), which has been realized in ultracold atom experiments. We first introduce the ɛ expansion technique based on a systematic expansion in terms of the dimensionality of space. We apply this technique to compute the thermodynamic quantities, the quasiparticle cum, and the criticl temperature of UFG. We then discuss consequences of the scale and conformal invariance of UFG. We prove a correspondence between primary operators in nonrelativistic conformal field theories and energy eigenstates in a harmonic potential. We use this correspondence to compute energies of fermions at unitarity in a harmonic potential. The scale and conformal invariance together with the general coordinate invariance constrains the properties of UFG. We show the vanishing bulk viscosities of UFG and derive the low-energy effective Lagrangian for the superfluid UFG. Finally we propose other systems exhibiting the nonrelativistic scaling and conformal symmetries that can be in principle realized in ultracold atom experiments.

  3. Cosmological perturbations for an inflaton field coupled to radiation

    SciTech Connect

    Visinelli, Luca

    2015-01-01

    Within the framework of the interacting fluid formalism, we provide the numerical solution to the Boltzmann equation describing the evolution of an inflaton field coupled to radiation. We study the behavior of the system during the slow-roll regime, in the case in which an additional stochastic source term is included in the set of equations, and we recover the expression for the cosmological perturbations previously obtained in the Warm inflation scenarios.

  4. Cosmological perturbations in coherent oscillating scalar field models

    NASA Astrophysics Data System (ADS)

    Cembranos, J. A. R.; Maroto, A. L.; Jareño, S. J. Núñez

    2016-03-01

    The fact that fast oscillating homogeneous scalar fields behave as perfect fluids in average and their intrinsic isotropy have made these models very fruitful in cosmology. In this work we will analyse the perturbations dynamics in these theories assuming general power law potentials V( ϕ) = λ| ϕ| n /n. At leading order in the wavenumber expansion, a simple expression for the effective sound speed of perturbations is obtained c eff 2 = ω = ( n - 2)/( n + 2) with ω the effective equation of state. We also obtain the first order correction in k 2/ ω eff 2 , when the wavenumber k of the perturbations is much smaller than the background oscillation frequency, ω eff. For the standard massive case we have also analysed general anharmonic contributions to the effective sound speed. These results are reached through a perturbed version of the generalized virial theorem and also studying the exact system both in the super-Hubble limit, deriving the natural ansatz for δϕ; and for sub-Hubble modes, exploiting Floquet's theorem.

  5. Modular Hamiltonian for Excited States in Conformal Field Theory.

    PubMed

    Lashkari, Nima

    2016-07-22

    We present a novel replica trick that computes the relative entropy of two arbitrary states in conformal field theory. Our replica trick is based on the analytic continuation of partition functions that break the Z_{n} replica symmetry. It provides a method for computing arbitrary matrix elements of the modular Hamiltonian corresponding to excited states in terms of correlation functions. We show that the quantum Fisher information in vacuum can be expressed in terms of two-point functions on the replica geometry. We perform sample calculations in two-dimensional conformal field theories. PMID:27494465

  6. Modular Hamiltonian for Excited States in Conformal Field Theory

    NASA Astrophysics Data System (ADS)

    Lashkari, Nima

    2016-07-01

    We present a novel replica trick that computes the relative entropy of two arbitrary states in conformal field theory. Our replica trick is based on the analytic continuation of partition functions that break the Zn replica symmetry. It provides a method for computing arbitrary matrix elements of the modular Hamiltonian corresponding to excited states in terms of correlation functions. We show that the quantum Fisher information in vacuum can be expressed in terms of two-point functions on the replica geometry. We perform sample calculations in two-dimensional conformal field theories.

  7. Magnetic field homogeneity perturbations in finite Halbach dipole magnets.

    PubMed

    Turek, Krzysztof; Liszkowski, Piotr

    2014-01-01

    Halbach hollow cylinder dipole magnets of a low or relatively low aspect ratio attract considerable attention due to their applications, among others, in compact NMR and MRI systems for investigating small objects. However, a complete mathematical framework for the analysis of magnetic fields in these magnets has been developed only for their infinitely long precursors. In such a case the analysis is reduced to two-dimensions (2D). The paper details the analysis of the 3D magnetic field in the Halbach dipole cylinders of a finite length. The analysis is based on three equations in which the components of the magnetic flux density Bx, By and Bz are expanded to infinite power series of the radial coordinate r. The zeroth term in the series corresponds to a homogeneous magnetic field Bc, which is perturbed by the higher order terms due to a finite magnet length. This set of equations is supplemented with an equation for the field profile B(z) along the magnet axis, presented for the first time. It is demonstrated that the geometrical factors in the coefficients of particular powers of r, defined by intricate integrals are the coefficients of the Taylor expansion of the homogeneity profile (B(z)-Bc)/Bc. As a consequence, the components of B can be easily calculated with an arbitrary accuracy. In order to describe perturbations of the field due to segmentation, two additional equations are borrowed from the 2D theory. It is shown that the 2D approach to the perturbations generated by the segmentation can be applied to the 3D Halbach structures unless r is not too close to the inner radius of the cylinder ri. The mathematical framework presented in the paper was verified with great precision by computations of B by a highly accurate integration of the magnetostatic Coulomb law and utilized to analyze the inhomogeneity of the magnetic field in the magnet with the accuracy better than 1 ppm. PMID:24316186

  8. Local conformational perturbations of the DNA molecule in the SG-model

    NASA Astrophysics Data System (ADS)

    Krasnobaeva, L. A.; Shapovalov, A. V.

    2015-11-01

    Within the formalism of the Fokker-Planck equation, the influence of nonstationary external force, random force, and dissipation effects on dynamics local conformational perturbations (kink) propagating along the DNA molecule is investigated. Such waves have an important role in the regulation of important biological processes in living systems at the molecular level. As a dynamic model of DNA was used a modified sine-Gordon equation, simulating the rotational oscillations of bases in one of the chains DNA. The equation of evolution of the kink momentum is obtained in the form of the stochastic differential equation in the Stratonovich sense within the framework of the well-known McLaughlin and Scott energy approach. The corresponding Fokker-Planck equation for the momentum distribution function coincides with the equation describing the Ornstein-Uhlenbek process with a regular nonstationary external force. The influence of the nonlinear stochastic effects on the kink dynamics is considered with the help of the Fokker- Planck nonlinear equation with the shift coefficient dependent on the first moment of the kink momentum distribution function. Expressions are derived for average value and variance of the momentum. Examples are considered which demonstrate the influence of the external regular and random forces on the evolution of the average value and variance of the kink momentum. Within the formalism of the Fokker-Planck equation, the influence of nonstationary external force, random force, and dissipation effects on the kink dynamics is investigated in the sine-Gordon model. The equation of evolution of the kink momentum is obtained in the form of the stochastic differential equation in the Stratonovich sense within the framework of the well-known McLaughlin and Scott energy approach. The corresponding Fokker-Planck equation for the momentum distribution function coincides with the equation describing the Ornstein-Uhlenbek process with a regular nonstationary

  9. Local conformational perturbations of the DNA molecule in the SG-model

    SciTech Connect

    Krasnobaeva, L. A.; Shapovalov, A. V.

    2015-11-17

    Within the formalism of the Fokker–Planck equation, the influence of nonstationary external force, random force, and dissipation effects on dynamics local conformational perturbations (kink) propagating along the DNA molecule is investigated. Such waves have an important role in the regulation of important biological processes in living systems at the molecular level. As a dynamic model of DNA was used a modified sine-Gordon equation, simulating the rotational oscillations of bases in one of the chains DNA. The equation of evolution of the kink momentum is obtained in the form of the stochastic differential equation in the Stratonovich sense within the framework of the well-known McLaughlin and Scott energy approach. The corresponding Fokker–Planck equation for the momentum distribution function coincides with the equation describing the Ornstein–Uhlenbek process with a regular nonstationary external force. The influence of the nonlinear stochastic effects on the kink dynamics is considered with the help of the Fokker– Planck nonlinear equation with the shift coefficient dependent on the first moment of the kink momentum distribution function. Expressions are derived for average value and variance of the momentum. Examples are considered which demonstrate the influence of the external regular and random forces on the evolution of the average value and variance of the kink momentum. Within the formalism of the Fokker–Planck equation, the influence of nonstationary external force, random force, and dissipation effects on the kink dynamics is investigated in the sine–Gordon model. The equation of evolution of the kink momentum is obtained in the form of the stochastic differential equation in the Stratonovich sense within the framework of the well-known McLaughlin and Scott energy approach. The corresponding Fokker–Planck equation for the momentum distribution function coincides with the equation describing the Ornstein–Uhlenbek process with a regular

  10. Toroidal modeling of penetration of the resonant magnetic perturbation field

    SciTech Connect

    Liu Yueqiang; Kirk, A.

    2013-04-15

    A toroidal, quasi-linear model is proposed to study the penetration dynamics of the resonant magnetic perturbation (RMP) field into the plasma. The model couples the linear, fluid plasma response to a toroidal momentum balance equation, which includes torques induced by both fluid electromagnetic force and by (kinetic) neoclassical toroidal viscous (NTV) force. The numerical results for a test toroidal equilibrium quantify the effects of various physical parameters on the field penetration and on the plasma rotation braking. The neoclassical toroidal viscous torque plays a dominant role in certain region of the plasma, for the RMP penetration problem considered in this work.

  11. Kinetic and Thermodynamic Characterization of Dihydrotestosterone-Induced Conformational Perturbations in Androgen Receptor Ligand-Binding Domain

    PubMed Central

    Jasuja, Ravi; Ulloor, Jagadish; Yengo, Christopher M.; Choong, Karen; Istomin, Andrei Y.; Livesay, Dennis R.; Jacobs, Donald J.; Swerdloff, Ronald S.; Mikšovská, Jaroslava; Larsen, Randy W.; Bhasin, Shalender

    2009-01-01

    Ligand-induced conformational perturbations in androgen receptor (AR) are important in coactivator recruitment and transactivation. However, molecular rearrangements in AR ligand-binding domain (AR-LBD) associated with agonist binding and their kinetic and thermodynamic parameters are poorly understood. We used steady-state second-derivative absorption and emission spectroscopy, pressure and temperature perturbations, and 4,4′-bis-anilinonaphthalene 8-sulfonate (bis-ANS) partitioning to determine the kinetics and thermodynamics of the conformational changes in AR-LBD after dihydrotestosterone (DHT) binding. In presence of DHT, the second-derivative absorption spectrum showed a red shift and a change in peak-to-peak distance. Emission intensity increased upon DHT binding, and center of spectral mass was blue shifted, denoting conformational changes resulting in more hydrophobic environment for tyrosines and tryptophans within a more compact DHT-bound receptor. In pressure perturbation calorimetry, DHT-induced energetic stabilization increased the Gibbs free energy of unfolding to 8.4 ± 1.3 kcal/mol from 3.5 ± 1.6 kcal/mol. Bis-ANS partitioning studies revealed that upon DHT binding, AR-LBD underwent biphasic rearrangement with a high activation energy (13.4 kcal/mol). An initial, molten globule-like burst phase (k ∼30 sec−1) with greater solvent accessibility was followed by rearrangement (k ∼0.01 sec−1), leading to a more compact conformation than apo-AR-LBD. Molecular simulations demonstrated unique sensitivity of tyrosine and tryptophan residues during pressure unfolding with rearrangement of residues in the coactivator recruitment surfaces distant from the ligand-binding pocket. In conclusion, DHT binding leads to energetic stabilization of AR-LBD domain and substantial rearrangement of residues distant from the ligand-binding pocket. DHT binding to AR-LBD involves biphasic receptor rearrangement including population of a molten globule

  12. Conformal field theories with infinitely many conservation laws

    SciTech Connect

    Todorov, Ivan

    2013-02-15

    Globally conformal invariant quantum field theories in a D-dimensional space-time (D even) have rational correlation functions and admit an infinite number of conserved (symmetric traceless) tensor currents. In a theory of a scalar field of dimension D-2 they were demonstrated to be generated by bilocal normal products of free massless scalar fields with an O(N), U(N), or Sp(2N) (global) gauge symmetry [B. Bakalov, N. M. Nikolov, K.-H. Rehren, and I. Todorov, 'Unitary positive energy representations of scalar bilocal fields,' Commun. Math. Phys. 271, 223-246 (2007); e-print arXiv:math-ph/0604069v3; and 'Infinite dimensional Lie algebras in 4D conformal quantum field theory,' J. Phys. A Math Theor. 41, 194002 (2008); e-print arXiv:0711.0627v2 [hep-th

  13. Detailed ultraviolet asymptotics for AdS scalar field perturbations

    NASA Astrophysics Data System (ADS)

    Evnin, Oleg; Jai-akson, Puttarak

    2016-04-01

    We present a range of methods suitable for accurate evaluation of the leading asymptotics for integrals of products of Jacobi polynomials in limits when the degrees of some or all polynomials inside the integral become large. The structures in question have recently emerged in the context of effective descriptions of small amplitude perturbations in anti-de Sitter (AdS) spacetime. The limit of high degree polynomials corresponds in this situation to effective interactions involving extreme short-wavelength modes, whose dynamics is crucial for the turbulent instabilities that determine the ultimate fate of small AdS perturbations. We explicitly apply the relevant asymptotic techniques to the case of a self-interacting probe scalar field in AdS and extract a detailed form of the leading large degree behavior, including closed form analytic expressions for the numerical coefficients appearing in the asymptotics.

  14. Introduction to conformal field theory and string theory

    SciTech Connect

    Dixon, L.J.

    1989-12-01

    These lectures are meant to provide a brief introduction to conformal field theory (CFT) and string theory for those with no prior exposure to the subjects. There are many excellent reviews already available, and most of these go in to much more detail than I will be able to here. 52 refs., 11 figs.

  15. Non-linear curvature perturbation in multi-field inflation models with non-minimal coupling

    SciTech Connect

    White, Jonathan; Minamitsuji, Masato; Sasaki, Misao E-mail: masato.minamitsuji@ist.utl.pt

    2013-09-01

    Using the δN formalism we consider the non-linear curvature perturbation in multi-field models of inflation with non-minimal coupling. In particular, we focus on the relation between the δN formalism as applied in the conformally related Jordan and Einstein frames. Exploiting results already known in the Einstein frame, we give expressions for the power spectrum, spectral tilt and non-gaussianity associated with the Jordan frame curvature perturbation. In the case that an adiabatic limit has not been reached, we find that in general these quantities differ from those associated with the Einstein frame curvature perturbation, and also confirm their equivalence in the absence of isocurvature modes. We then proceed to consider two analytically soluble examples, the first involving a non-minimally coupled 'spectator' field and the second being a non-minimally coupled extension of the multi-brid inflation model. In the first model we find that predictions can easily be brought into agreement with the recent Planck results, as the tensor-to-scalar ratio is generally small, the spectral tilt tuneable and the non-gaussianity suppressed. In the second model we find that predictions for all three parameters can differ substantially from those predicted in the minimally coupled case, and that the recent Planck results for the spectral tilt can be used to constrain the non-minimal coupling parameters.

  16. Non-linear curvature perturbation in multi-field inflation models with non-minimal coupling

    NASA Astrophysics Data System (ADS)

    White, Jonathan; Minamitsuji, Masato; Sasaki, Misao

    2013-09-01

    Using the δN formalism we consider the non-linear curvature perturbation in multi-field models of inflation with non-minimal coupling. In particular, we focus on the relation between the δN formalism as applied in the conformally related Jordan and Einstein frames. Exploiting results already known in the Einstein frame, we give expressions for the power spectrum, spectral tilt and non-gaussianity associated with the Jordan frame curvature perturbation. In the case that an adiabatic limit has not been reached, we find that in general these quantities differ from those associated with the Einstein frame curvature perturbation, and also confirm their equivalence in the absence of isocurvature modes. We then proceed to consider two analytically soluble examples, the first involving a non-minimally coupled `spectator' field and the second being a non-minimally coupled extension of the multi-brid inflation model. In the first model we find that predictions can easily be brought into agreement with the recent Planck results, as the tensor-to-scalar ratio is generally small, the spectral tilt tuneable and the non-gaussianity suppressed. In the second model we find that predictions for all three parameters can differ substantially from those predicted in the minimally coupled case, and that the recent Planck results for the spectral tilt can be used to constrain the non-minimal coupling parameters.

  17. Conformal consistency relations for single-field inflation

    SciTech Connect

    Creminelli, Paolo; Noreña, Jorge; Simonović, Marko E-mail: jorge.norena@gmail.com

    2012-07-01

    We generalize the single-field consistency relations to capture not only the leading term in the squeezed limit — going as 1/q{sup 3}, where q is the small wavevector — but also the subleading one, going as 1/q{sup 2}. This term, for an (n+1)-point function, is fixed in terms of the variation of the n-point function under a special conformal transformation; this parallels the fact that the 1/q{sup 3} term is related with the scale dependence of the n-point function. For the squeezed limit of the 3-point function, this conformal consistency relation implies that there are no terms going as 1/q{sup 2}. We verify that the squeezed limit of the 4-point function is related to the conformal variation of the 3-point function both in the case of canonical slow-roll inflation and in models with reduced speed of sound. In the second case the conformal consistency conditions capture, at the level of observables, the relation among operators induced by the non-linear realization of Lorentz invariance in the Lagrangian. These results mean that, in any single-field model, primordial correlation functions of ζ are endowed with an SO(4,1) symmetry, with dilations and special conformal transformations non-linearly realized by ζ. We also verify the conformal consistency relations for any n-point function in models with a modulation of the inflaton potential, where the scale dependence is not negligible. Finally, we generalize (some of) the consistency relations involving tensors and soft internal momenta.

  18. Large perturbation flow field analysis and simulation for supersonic inlets

    NASA Technical Reports Server (NTRS)

    Varner, M. O.; Martindale, W. R.; Phares, W. J.; Kneile, K. R.; Adams, J. C., Jr.

    1984-01-01

    An analysis technique for simulation of supersonic mixed compression inlets with large flow field perturbations is presented. The approach is based upon a quasi-one-dimensional inviscid unsteady formulation which includes engineering models of unstart/restart, bleed, bypass, and geometry effects. Numerical solution of the governing time dependent equations of motion is accomplished through a shock capturing finite difference algorithm, of which five separate approaches are evaluated. Comparison with experimental supersonic wind tunnel data is presented to verify the present approach for a wide range of transient inlet flow conditions.

  19. Boundary conformal field theory and tunneling of edge quasiparticles in non-Abelian topological states

    SciTech Connect

    Fendley, Paul; Fisher, Matthew P.A.; Nayak, Chetan

    2009-07-15

    We explain how (perturbed) boundary conformal field theory allows us to understand the tunneling of edge quasiparticles in non-Abelian topological states. The coupling between a bulk non-Abelian quasiparticle and the edge is due to resonant tunneling to a zero mode on the quasiparticle, which causes the zero mode to hybridize with the edge. This can be reformulated as the flow from one conformally invariant boundary condition to another in an associated critical statistical mechanical model. Tunneling from one edge to another at a point contact can split the system in two, either partially or completely. This can be reformulated in the critical statistical mechanical model as the flow from one type of defect line to another. We illustrate these two phenomena in detail in the context of the {nu}=5/2 quantum Hall state and the critical Ising model. We briefly discuss the case of Fibonacci anyons and conclude by explaining the general formulation and its physical interpretation.

  20. Quantum entanglement of local operators in conformal field theories.

    PubMed

    Nozaki, Masahiro; Numasawa, Tokiro; Takayanagi, Tadashi

    2014-03-21

    We introduce a series of quantities which characterize a given local operator in any conformal field theory from the viewpoint of quantum entanglement. It is defined by the increased amount of (Rényi) entanglement entropy at late time for an excited state defined by acting the local operator on the vacuum. We consider a conformal field theory on an infinite space and take the subsystem in the definition of the entanglement entropy to be its half. We calculate these quantities for a free massless scalar field theory in two, four and six dimensions. We find that these results are interpreted in terms of quantum entanglement of a finite number of states, including Einstein-Podolsky-Rosen states. They agree with a heuristic picture of propagations of entangled particles. PMID:24702348

  1. Conformal field theory out of equilibrium: a review

    NASA Astrophysics Data System (ADS)

    Bernard, Denis; Doyon, Benjamin

    2016-06-01

    We provide a pedagogical review of the main ideas and results in non-equilibrium conformal field theory and connected subjects. These concern the understanding of quantum transport and its statistics at and near critical points. Starting with phenomenological considerations, we explain the general framework, illustrated by the example of the Heisenberg quantum chain. We then introduce the main concepts underlying conformal field theory (CFT), the emergence of critical ballistic transport, and the CFT scattering construction of non-equilibrium steady states. Using this we review the theory for energy transport in homogeneous one-dimensional critical systems, including the complete description of its large deviations and the resulting (extended) fluctuation relations. We generalize some of these ideas to one-dimensional critical charge transport and to the presence of defects, as well as beyond one-dimensional criticality. We describe non-equilibrium transport in free-particle models, where connections are made with generalized Gibbs ensembles, and in higher-dimensional and non-integrable quantum field theories, where the use of the powerful hydrodynamic ideas for non-equilibrium steady states is explained. We finish with a list of open questions. The review does not assume any advanced prior knowledge of conformal field theory, large-deviation theory or hydrodynamics.

  2. Post-measurement bipartite entanglement entropy in conformal field theories

    NASA Astrophysics Data System (ADS)

    Rajabpour, M. A.

    2015-08-01

    We derive exact formulas for bipartite von Neumann entanglement entropy after partial projective local measurement in (1 +1 ) -dimensional conformal field theories with periodic and open boundary conditions. After defining the setup we will check numerically the validity of our results in the case of Klein-Gordon field theory (coupled harmonic oscillators) and spin-1 /2 X X chain in a magnetic field. The agreement between analytical results and the numerical calculations is very good. We also find a lower bound for localizable entanglement in coupled harmonic oscillators.

  3. Locality of Gravitational Systems from Entanglement of Conformal Field Theories.

    PubMed

    Lin, Jennifer; Marcolli, Matilde; Ooguri, Hirosi; Stoica, Bogdan

    2015-06-01

    The Ryu-Takayanagi formula relates the entanglement entropy in a conformal field theory to the area of a minimal surface in its holographic dual. We show that this relation can be inverted for any state in the conformal field theory to compute the bulk stress-energy tensor near the boundary of the bulk spacetime, reconstructing the local data in the bulk from the entanglement on the boundary. We also show that positivity, monotonicity, and convexity of the relative entropy for small spherical domains between the reduced density matrices of any state and of the ground state of the conformal field theory are guaranteed by positivity conditions on the bulk matter energy density. As positivity and monotonicity of the relative entropy are general properties of quantum systems, this can be interpreted as a derivation of bulk energy conditions in any holographic system for which the Ryu-Takayanagi prescription applies. We discuss an information theoretical interpretation of the convexity in terms of the Fisher metric. PMID:26196612

  4. Reheating dynamics affects non-perturbative decay of spectator fields

    NASA Astrophysics Data System (ADS)

    Enqvist, Kari; Lerner, Rose N.; Rusak, Stanislav

    2013-11-01

    The behaviour of oscillating scalar spectator fields after inflation depends on the thermal background produced by inflaton decay. Resonant decay of the spectator is often blocked by large induced thermal masses. We account for the finite decay width of the inflaton and the protracted build-up of the thermal bath to determine the early evolution of a homogeneous spectator field σ coupled to the Higgs Boson Φ through the term g2σ2Φ2, the only renormalisable coupling of a new scalar to the Standard Model. We find that for very large higgs-spectator coupling ggtrsim10-3, the resonance is not always blocked as was previously suggested. As a consequence, the oscillating spectator can decay quickly. For other parameter values, we find that although qualitative features of the thermal blocking still hold, the dynamics are altered compared to the instant decay case. These findings are important for curvaton models, where the oscillating field must be relatively long lived in order to produce the curvature perturbation. They are also relevant for other spectator fields, which must decay sufficiently early to avoid spoiling the predictions of baryogenesis and nucleosynthesis.

  5. Reheating dynamics affects non-perturbative decay of spectator fields

    SciTech Connect

    Enqvist, Kari; Lerner, Rose N.; Rusak, Stanislav E-mail: rose.lerner@helsinki.fi

    2013-11-01

    The behaviour of oscillating scalar spectator fields after inflation depends on the thermal background produced by inflaton decay. Resonant decay of the spectator is often blocked by large induced thermal masses. We account for the finite decay width of the inflaton and the protracted build-up of the thermal bath to determine the early evolution of a homogeneous spectator field σ coupled to the Higgs Boson Φ through the term g{sup 2}σ{sup 2}Φ{sup 2}, the only renormalisable coupling of a new scalar to the Standard Model. We find that for very large higgs-spectator coupling g∼>10{sup −3}, the resonance is not always blocked as was previously suggested. As a consequence, the oscillating spectator can decay quickly. For other parameter values, we find that although qualitative features of the thermal blocking still hold, the dynamics are altered compared to the instant decay case. These findings are important for curvaton models, where the oscillating field must be relatively long lived in order to produce the curvature perturbation. They are also relevant for other spectator fields, which must decay sufficiently early to avoid spoiling the predictions of baryogenesis and nucleosynthesis.

  6. Transverse Field Perturbation For PIP-II SRF Cavities

    SciTech Connect

    Berrutti, Paolo; Khabiboulline, Timergali N.; Lebedev, Valeri; Yakovlev, Vyacheslav P.

    2015-06-01

    Proton Improvement Plan II (PIP-II) consists in a plan for upgrading the Fermilab proton accelerator complex to a beam power capability of at least 1 MW delivered to the neutrino production target. A room temperature section accelerates H⁻ ions to 2.1 MeV and creates the desired bunch structure for injection into the superconducting (SC) linac. Five cavity types, operating at three different frequencies 162.5, 325 and 650 MHz, provide acceleration to 800 MeV. This paper presents the studies on transverse field perturbation on particle dynamic for all the superconducting cavities in the linac. The effects studied include quadrupole defocusing for coaxial resonators, and dipole kick due to couplers for elliptical cavities. A multipole expansion has been performed for each of the cavity designs including effects up to octupole.

  7. The unitary conformal field theory behind 2D Asymptotic Safety

    NASA Astrophysics Data System (ADS)

    Nink, Andreas; Reuter, Martin

    2016-02-01

    Being interested in the compatibility of Asymptotic Safety with Hilbert space positivity (unitarity), we consider a local truncation of the functional RG flow which describes quantum gravity in d > 2 dimensions and construct its limit of exactly two dimensions. We find that in this limit the flow displays a nontrivial fixed point whose effective average action is a non-local functional of the metric. Its pure gravity sector is shown to correspond to a unitary conformal field theory with positive central charge c = 25. Representing the fixed point CFT by a Liouville theory in the conformal gauge, we investigate its general properties and their implications for the Asymptotic Safety program. In particular, we discuss its field parametrization dependence and argue that there might exist more than one universality class of metric gravity theories in two dimensions. Furthermore, studying the gravitational dressing in 2D asymptotically safe gravity coupled to conformal matter we uncover a mechanism which leads to a complete quenching of the a priori expected Knizhnik-Polyakov-Zamolodchikov (KPZ) scaling. A possible connection of this prediction to Monte Carlo results obtained in the discrete approach to 2D quantum gravity based upon causal dynamical triangulations is mentioned. Similarities of the fixed point theory to, and differences from, non-critical string theory are also described. On the technical side, we provide a detailed analysis of an intriguing connection between the Einstein-Hilbert action in d > 2 dimensions and Polyakov's induced gravity action in two dimensions.

  8. Bootstrapping conformal field theories with the extremal functional method.

    PubMed

    El-Showk, Sheer; Paulos, Miguel F

    2013-12-13

    The existence of a positive linear functional acting on the space of (differences between) conformal blocks has been shown to rule out regions in the parameter space of conformal field theories (CFTs). We argue that at the boundary of the allowed region the extremal functional contains, in principle, enough information to determine the dimensions and operator product expansion (OPE) coefficients of an infinite number of operators appearing in the correlator under analysis. Based on this idea we develop the extremal functional method (EFM), a numerical procedure for deriving the spectrum and OPE coefficients of CFTs lying on the boundary (of solution space). We test the EFM by using it to rederive the low lying spectrum and OPE coefficients of the two-dimensional Ising model based solely on the dimension of a single scalar quasiprimary--no Virasoro algebra required. Our work serves as a benchmark for applications to more interesting, less known CFTs in the near future. PMID:24483643

  9. Universal entanglement and boundary geometry in conformal field theory

    NASA Astrophysics Data System (ADS)

    Herzog, Christopher P.; Huang, Kuo-Wei; Jensen, Kristan

    2016-01-01

    Employing a conformal map to hyperbolic space cross a circle, we compute the universal contribution to the vacuum entanglement entropy (EE) across a sphere in even-dimensional conformal field theory. Previous attempts to derive the EE in this way were hindered by a lack of knowledge of the appropriate boundary terms in the trace anomaly. In this paper we show that the universal part of the EE can be treated as a purely boundary effect. As a byproduct of our computation, we derive an explicit form for the A-type anomaly contribution to the Wess-Zumino term for the trace anomaly, now including boundary terms. In d = 4 and 6, these boundary terms generalize earlier bulk actions derived in the literature.

  10. Volume rendering: application in static field conformal radiosurgery

    NASA Astrophysics Data System (ADS)

    Bourland, J. Daniel; Camp, Jon J.; Robb, Richard A.

    1992-09-01

    Lesions in the head which are large or irregularly shaped present challenges for radiosurgical treatment by linear accelerator or other radiosurgery modalities. To treat these lesions we are developing static field, conformal stereotactic radiosurgery. In this procedure seven to eleven megavoltage x-ray beams are aimed at the target volume. Each beam is designed from the beam's-eye view, and has its own unique geometry: gantry angle, table angle, and shape which conforms to the projected cross-section of the target. A difficulty with this and other 3- D treatment plans is the visualization of the treatment geometry and proposed treatment plan. Is the target volume geometrically covered by the arrangement of beams, and is the dose distribution adequate? To answer these questions we have been investigating the use of ANALYZETM volume rendering to display the target anatomy and the resultant dose distribution.

  11. The Stochastic Elastica and Excluded-Volume Perturbations of DNA Conformational Ensembles

    PubMed Central

    Chirikjian, Gregory S.

    2010-01-01

    A coordinate-free Lie-group formulation for generating ensembles of DNA conformations in solution is presented. In this formulation, stochastic differential equations define sample paths on the Euclidean motion group. The ensemble of these paths exhibits the same behavior as solutions of the Fokker-Planck equation for the stochastically forced elastica. Longer chains for which the effects of excluded volume become important are handled by piecing together shorter chains and modeling their interactions. It is assumed that the final chain lengths of interest are long enough for excluded volume effects to become important, but not so long that the semi-flexible nature of the chain is lost. The effect of excluded volume is then taken into account by grouping short self-avoiding conformations into ‘bundles’ with common end constraints and computing average interaction effects between bundles. The accuracy of this approximation is shown to be good when using a numerically generated ensemble of self-avoiding sample paths as the baseline for comparison. PMID:20228889

  12. Non-conformal evolution of magnetic fields during reheating

    NASA Astrophysics Data System (ADS)

    Calzetta, Esteban; Kandus, Alejandra

    2015-03-01

    We consider the evolution of electromagnetic fields coupled to conduction currents during the reheating era after inflation, and prior to the establishing of the proton-electron plasma. We assume that the currents may be described by second order causal hydrodynamics. The resulting theory is not conformally invariant. The expansion of the Universe produces temperature gradients which couple to the current and generally oppose Ohmic dissipation. Although the effect is not strong, it suggests that the unfolding of hydrodynamic instabilities in these models may follow a different pattern than in first order theories, and even than in second order theories on non expanding backgrounds.

  13. Cosmological perturbations in SFT inspired non-local scalar field models

    NASA Astrophysics Data System (ADS)

    Koshelev, Alexey S.; Vernov, Sergey Yu.

    2012-10-01

    We study cosmological perturbations in models with a single non-local scalar field originating from the string field theory description of the rolling tachyon dynamics. We construct the equation for the energy density perturbations of the non-local scalar field and explicitly prove that for the free field it is identical to a system of local cosmological perturbation equations in a particular model with multiple (maybe infinitely many) local free scalar fields. We also show that vector and tensor perturbations are absent in this set-up.

  14. Entanglement of low-energy excitations in conformal field theory.

    PubMed

    Alcaraz, Francisco Castilho; Ibáñez Berganza, Miguel; Sierra, Germán

    2011-05-20

    In a quantum critical chain, the scaling regime of the energy and momentum of the ground state and low-lying excitations are described by conformal field theory (CFT). The same holds true for the von Neumann and Rényi entropies of the ground state, which display a universal logarithmic behavior depending on the central charge. In this Letter we generalize this result to those excited states of the chain that correspond to primary fields in CFT. It is shown that the nth Rényi entropy is related to a 2n-point correlator of primary fields. We verify this statement for the critical XX and XXZ chains. This result uncovers a new link between quantum information theory and CFT. PMID:21668218

  15. Entanglement of Low-Energy Excitations in Conformal Field Theory

    SciTech Connect

    Alcaraz, Francisco Castilho; Ibanez Berganza, Miguel; Sierra, German

    2011-05-20

    In a quantum critical chain, the scaling regime of the energy and momentum of the ground state and low-lying excitations are described by conformal field theory (CFT). The same holds true for the von Neumann and Renyi entropies of the ground state, which display a universal logarithmic behavior depending on the central charge. In this Letter we generalize this result to those excited states of the chain that correspond to primary fields in CFT. It is shown that the nth Renyi entropy is related to a 2n-point correlator of primary fields. We verify this statement for the critical XX and XXZ chains. This result uncovers a new link between quantum information theory and CFT.

  16. Gauge invariant two-point vertices of shadow fields, AdS/CFT, and conformal fields

    SciTech Connect

    Metsaev, R. R.

    2010-05-15

    In the framework of gauge invariant Stueckelberg approach, totally symmetric arbitrary spin shadow fields in flat space-time of dimension greater than or equal to four are studied. Gauge invariant two-point vertices for such shadow fields are obtained. We demonstrate that, in Stueckelberg gauge frame, these gauge invariant vertices become the standard two-point vertices of CFT. Light-cone gauge two-point vertices of the shadow fields are also obtained. AdS/CFT correspondence for the shadow fields and the non-normalizable solutions of free massless totally symmetric arbitrary spin AdS fields is studied. AdS fields are considered in a modified de Donder gauge and this simplifies considerably the study of AdS/CFT correspondence. We demonstrate that the bulk action, when it is evaluated on solution of the Dirichlet problem, leads to the two-point gauge invariant vertex of shadow field. Also we show that the bulk action evaluated on solution of the Dirichlet problem leads to new description of conformal fields. The new description involves Stueckelberg gauge symmetries and gives simple higher-derivative Lagrangian for the conformal arbitrary spin field. In the Stueckelberg gauge frame, our Lagrangian becomes the standard Lagrangian of conformal field. Light-cone gauge Lagrangian of the arbitrary spin conformal field is also obtained.

  17. Molecular Dynamics Investigations of the Local Structural Characteristics of DNA Oligonucleotides: Studies of Helical Axis Deformations, Conformational Sequence Dependence and Modified Nucleoside Perturbations.

    NASA Astrophysics Data System (ADS)

    Louise-May, Shirley

    The present DNA studies investigate the local structure of DNA oligonucleotides in order to characterize helical axis deformations, sequence dependent fine structure and modified nucleoside perturbations of selected oligonucleotide sequences. The molecular dynamics method is used to generate an ensemble of energetically feasible DNA conformations which can then be analyzed for dynamical conformational properties, some of which can be compared to experimentally derived values. A theory and graphical presentation for the analysis of helical deformations of DNA based on the configurational statistics of polymers, called "Persistence Analysis", was designed. The results of the analysis on prototype forms, static crystal structures and two solvated MD simulations of the sequence d(CGCGAATTCGCG) indicate that all of the expected features of bending can be sensitively and systematically identified by this approach. Comparison of the relative performance of three molecular dynamics potential functions commonly used for dynamical modeling of biological macromolecules; CHARMm, AMBER and GROMOS was investigated via in vacuo MD simulations on the dodecamer sequence d(CGCGAATTCGCG)_2 with respect to the conformational properties of each dynamical model and their ability to support A and B families of DNA. Vacuum molecular dynamics simulations using the CHARMm force field carried out on simple homo- and heteropolymers of DNA led to the conclusion that sequence dependent fine structure appears to be well defined for adenine-thymine rich sequences both at the base pair and base step level whereas much of the the fine structure found in cytosine -guanine rich sequences appears to be context dependent. The local conformational properties of the homopolymer poly (dA) -poly (dT) revealed one dynamical model which was found in general agreement with fiber models currently available. Investigation of the relative structural static and dynamical effect of the misincorporation of

  18. Positive Energy Conditions in 4D Conformal Field Theory

    NASA Astrophysics Data System (ADS)

    Farnsworth, Kara; Luty, Markus; Prilepina, Valentina

    2016-03-01

    We argue that all consistent 4D quantum field theories obey a spacetime-averaged weak energy inequality avgT00 >= - C /L4 , where L is the size of the smearing region, and C is a positive constant that depends on the theory. If this condition is violated, the theory has states that are indistinguishable from states of negative total energy by any local measurement, and we expect instabilities or other inconsistencies. We apply this condition to 4D conformal field theories, and find that it places constraints on the OPE coefficients of the theory. The constraints we find are weaker than the ``conformal collider'' constraints of Hofman and Maldacena. We speculate that there may be theories that violate the Hofman-Maldacena bounds, but satisfy our bounds. In 3D CFTs, the only constraint we find is equivalent to the positivity of 2-point function of the energy-momentum tensor, which follows from unitarity. Our calculations are performed using momentum-space Wightman functions, which are remarkably simple functions of momenta, and may be of interest in their own right.

  19. Dynamics of perturbations in Double Field Theory & non-relativistic string theory

    NASA Astrophysics Data System (ADS)

    Ko, Sung Moon; Melby-Thompson, Charles M.; Meyer, René; Park, Jeong-Hyuck

    2015-12-01

    Double Field Theory provides a geometric framework capable of describing string theory backgrounds that cannot be understood purely in terms of Riemannian geometry — not only globally (`non-geometry'), but even locally (`non-Riemannian'). In this work, we show that the non-relativistic closed string theory of Gomis and Ooguri [1] arises precisely as such a non-Riemannian string background, and that the Gomis-Ooguri sigma model is equivalent to the Double Field Theory sigma model of [2] on this background. We further show that the target-space formulation of Double Field Theory on this non-Riemannian background correctly reproduces the appropriate sector of the Gomis-Ooguri string spectrum. To do this, we develop a general semi-covariant formalism describing perturbations in Double Field Theory. We derive compact expressions for the linearized equations of motion around a generic on-shell background, and construct the corresponding fluctuation Lagrangian in terms of novel completely covariant second order differential operators. We also present a new non-Riemannian solution featuring Schrödinger conformal symmetry.

  20. Synchrotron radiation in strongly coupled conformal field theories

    SciTech Connect

    Athanasiou, Christiana; Chesler, Paul M.; Liu, Hong; Rajagopal, Krishna; Nickel, Dominik

    2010-06-15

    Using gauge/gravity duality, we compute the energy density and angular distribution of the power radiated by a quark undergoing circular motion in strongly coupled N=4 supersymmetric Yang-Mills theory. We compare the strong coupling results to those at weak coupling, finding them to be very similar. In both regimes, the angular distribution of the radiated power is in fact similar to that of synchrotron radiation produced by an electron in circular motion in classical electrodynamics: the quark emits radiation in a narrow beam along its velocity vector with a characteristic opening angle {alpha}{approx}1/{gamma}. To an observer far away from the quark, the emitted radiation appears as a short periodic burst, just like the light from a lighthouse does to a ship at sea. Our strong coupling results are valid for any strongly coupled conformal field theory with a dual classical gravity description.

  1. Energy flux positivity and unitarity in conformal field theories.

    PubMed

    Kulaxizi, Manuela; Parnachev, Andrei

    2011-01-01

    We show that in most conformal field theories the condition of the energy flux positivity, proposed by Hofman and Maldacena, is equivalent to the absence of ghosts. At finite temperature and large energy and momenta, the two-point functions of the stress energy tensor develop lightlike poles. The residues of the poles can be computed, as long as the only spin-two conserved current, which appears in the stress energy tensor operator-product expansion and acquires a nonvanishing expectation value at finite temperature, is the stress energy tensor. The condition for the residues to stay positive and the theory to remain ghost-free is equivalent to the condition of positivity of energy flux. PMID:21231731

  2. Energy Flux Positivity and Unitarity in Conformal Field Theories

    SciTech Connect

    Kulaxizi, Manuela; Parnachev, Andrei

    2011-01-07

    We show that in most conformal field theories the condition of the energy flux positivity, proposed by Hofman and Maldacena, is equivalent to the absence of ghosts. At finite temperature and large energy and momenta, the two-point functions of the stress energy tensor develop light like poles. The residues of the poles can be computed, as long as the only spin-two conserved current, which appears in the stress energy tensor operator-product expansion and acquires a nonvanishing expectation value at finite temperature, is the stress energy tensor. The condition for the residues to stay positive and the theory to remain ghost-free is equivalent to the condition of positivity of energy flux.

  3. Perturbative no-hair property of form fields for higher dimensional static black holes

    SciTech Connect

    Shiromizu, Tetsuya; Ohashi, Seiju; Tanabe, Kentaro

    2011-04-15

    In this paper we examine the static perturbation of p-form field strengths around higher dimensional Schwarzschild spacetimes. As a result, we can see that the static perturbations do not exist when p{>=}3. This result supports the no-hair properties of p-form fields. However, this does not exclude the presence of the black objects having nonspherical topology.

  4. Warped conformal field theory as lower spin gravity

    NASA Astrophysics Data System (ADS)

    Hofman, Diego M.; Rollier, Blaise

    2015-08-01

    Two dimensional Warped Conformal Field Theories (WCFTs) may represent the simplest examples of field theories without Lorentz invariance that can be described holographically. As such they constitute a natural window into holography in non-AdS space-times, including the near horizon geometry of generic extremal black holes. It is shown in this paper that WCFTs posses a type of boost symmetry. Using this insight, we discuss how to couple these theories to background geometry. This geometry is not Riemannian. We call it Warped Geometry and it turns out to be a variant of a Newton-Cartan structure with additional scaling symmetries. With this formalism the equivalent of Weyl invariance in these theories is presented and we write two explicit examples of WCFTs. These are free fermionic theories. Lastly we present a systematic description of the holographic duals of WCFTs. It is argued that the minimal setup is not Einstein gravity but an SL (2, R) × U (1) Chern-Simons Theory, which we call Lower Spin Gravity. This point of view makes manifest the definition of boundary for these non-AdS geometries. This case represents the first step towards understanding a fully invariant formalism for WN field theories and their holographic duals.

  5. Quantum corrections to the cosmological evolution of conformally coupled fields

    SciTech Connect

    Cembranos, Jose A.R.; Olive, Keith A.; Peloso, Marco; Uzan, Jean-Philippe E-mail: olive@physics.umn.edu E-mail: uzan@iap.fr

    2009-07-01

    Because the source term for the equations of motion of a conformally coupled scalar field, such as the dilaton, is given by the trace of the matter energy momentum tensor, it is commonly assumed to vanish during the radiation dominated epoch in the early universe. As a consequence, such fields are generally frozen in the early universe. Here we compute the finite temperature radiative correction to the source term and discuss its consequences on the evolution of such fields in the early universe. We discuss in particular, the case of scalar tensor theories of gravity which have general relativity as an attractor solution. We show that, in some cases, the universe can experience an early phase of contraction, followed by a non-singular bounce, and standard expansion. This can have interesting consequences for the abundance of thermal relics; for instance, it can provide a solution to the gravitino problem. We conclude by discussing the possible consequences of the quantum corrections to the evolution of the dilaton.

  6. Time-dependent perturbation of a two-state quantum system by a sinusoidal field

    NASA Technical Reports Server (NTRS)

    Dion, D. R.; Hirschfelder, J. O.

    1976-01-01

    Different methods for solving the 'two-level problem' are discussed, namely, the problem of what happens to a material system having only two nondegenerate energy levels when it is perturbed by an electromagnetic field that varies with time in a monochromatic sinusoidal fashion. The various methods discussed include: (1) the Sen Gupta technique using nondegenerate Rayleigh-Schroedinger perturbation theory, (2) the Salwen-Winter-Shirley partitioning perturbation technique, (3) the Shirley and series degenerate Rayleigh-Schroedinger expansion, (4) the degenerate Rayleigh-Schroedinger technique for considering high frequency fields, and (5) the singular perturbation expansion technique.

  7. Impact of resistive MHD plasma response on perturbation field sidebands

    NASA Astrophysics Data System (ADS)

    Orlov, D. M.; Evans, T. E.; Moyer, R. A.; Lyons, B. C.; Ferraro, N. M.; Park, G.-Y.

    2016-07-01

    Single fluid linear simulations of a KSTAR RMP ELM suppressed discharge with the M3D-C1 resistive magnetohydrodynamic code have been performed for the first time. The simulations show that the application of the n  =  1 perturbation using the KSTAR in-vessel control coils (IVCC), which apply modest levels of n  =  3 sidebands (~20% of the n  =  1), leads to levels of n  =  3 sideband that are comparable to the n  =  1 when plasma response is included. This is due to the reduced level of screening of the rational-surface-resonant n  =  3 component relative to the rational-surface-resonant n  =  1 component. The n  =  3 sidebands could play a similar role in ELM suppression on KSTAR as the toroidal sidebands (n  =  1, 2, 4) in DIII-D n  =  3 ELM suppression with missing I-coil segments (Paz Soldan et al 2014 Nucl. Fusion 54 073013). This result may help to explain the uniqueness of ELM suppression with n  =  1 perturbations in KSTAR since the effective perturbation is a mixed n  =  1/n  =  3 perturbation similar to n  =  3 ELM suppression in DIII-D.

  8. Scalar field dark energy perturbations and their scale dependence

    SciTech Connect

    Unnikrishnan, Sanil; Seshadri, T. R.; Jassal, H. K.

    2008-12-15

    We estimate the amplitude of perturbation in dark energy at different length scales for a quintessence model with an exponential potential. It is shown that on length scales much smaller than Hubble radius, perturbation in dark energy is negligible in comparison to that in dark matter. However, on scales comparable to the Hubble radius ({lambda}{sub p}>1000 Mpc) the perturbation in dark energy in general cannot be neglected. As compared to the {lambda}CDM model, the large-scale matter power spectrum is suppressed in a generic quintessence dark energy model. We show that on scales {lambda}{sub p}<1000 Mpc, this suppression is primarily due to different background evolution compared to the {lambda}CDM model. However, on much larger scales perturbation in dark energy can affect the matter power spectrum significantly. Hence this analysis can act as a discriminator between the {lambda}CDM model and other generic dark energy models with w{sub de}{ne}-1.

  9. Large-scale perturbations from the waterfall field in hybrid inflation

    SciTech Connect

    Fonseca, José; Wands, David; Sasaki, Misao E-mail: misao@yukawa.kyoto-u.ac.jp

    2010-09-01

    We estimate large-scale curvature perturbations from isocurvature fluctuations in the waterfall field during hybrid inflation, in addition to the usual inflaton field perturbations. The tachyonic instability at the end of inflation leads to an explosive growth of super-Hubble scale perturbations, but they retain the steep blue spectrum characteristic of vacuum fluctuations in a massive field during inflation. The power spectrum thus peaks around the Hubble-horizon scale at the end of inflation. We extend the usual δN formalism to include the essential role of these small fluctuations when estimating the large-scale curvature perturbation. The resulting curvature perturbation due to fluctuations in the waterfall field is second-order and the spectrum is expected to be of order 10{sup −54} on cosmological scales.

  10. Perturbation analysis of deformed Q-balls and primordial magnetic fields

    SciTech Connect

    Uesugi, Tomoko; Shiromizu, Tetsuya; Aoki, Mayumi

    1999-11-19

    We study the excited states of the Q-balls by performing stationary perturbation on the spherical Q-balls. We find the exact solution of the stationary perturbation of the global Q-ball. For local Q-balls we solve the equations of motion for the perturbative part approximately by using expansion about the coupling constant. Furthermore we comment on the magnetic field generated by the excited states of local Q-balls during the phase transition.

  11. Apparatus and method for microwave processing of materials using field-perturbing tool

    DOEpatents

    Tucker, Denise A.; Fathi, Zakaryae; Lauf, Robert J.

    2001-01-01

    A variable frequency microwave heating apparatus designed to allow modulation of the frequency of the microwaves introduced into a multi-mode microwave cavity for heating or other selected applications. A field-perturbing tool is disposed within the cavity to perturb the microwave power distribution in order to apply a desired level of microwave power to the workpiece.

  12. Automated conformational energy fitting for force-field development

    PubMed Central

    Guvench, Olgun; MacKerell, Alexander D.

    2010-01-01

    We present a general conformational-energy fitting procedure based on Monte Carlo simulated annealing (MCSA) for application in the development of molecular mechanics force fields. Starting with a target potential energy surface and an unparameterized molecular mechanics potential energy surface, an optimized set of either dihedral or grid-based correction map (CMAP) parameters is produced that minimizes the root mean squared error (RMSE) between the parameterized and targeted energies. The fitting is done using an MCSA search in parameter space and consistently converges to the same RMSE irrespective of the randomized parameters used to seed the search. Any number of dihedral parameters can be simultaneously parameterized, allowing for fitting to multi-dimensional potential energy scans. Fitting options for dihedral parameters include non-uniform weighting of the target data, constraining multiple optimized parameters to the same value, constraining parameters to be no greater than a user-specified maximum value, including all or only a subset of multiplicities defining the dihedral Fourier series, and optimization of phase angles in addition to force constants. The dihedral parameter fitting algorithm’s performance is characterized through multi-dimensional fitting of cyclohexane, tetrahydropyran, and hexopyranose monosaccharide energetics, with the latter case having a 30-dimensional parameter space. The CMAP fitting is applied in the context of polypeptides, and is used to develop a parameterization that simultaneously captures the φ, ψ energetics of the alanine dipeptide and the alanine tetrapeptide. Because the dihedral energy term is common to many force fields, we have implemented the dihedral-fitting algorithm in the portable Python scripting language and have made it freely available as Supplementary Material. PMID:18458967

  13. Test of the Anti-de Sitter-Space/Conformal-Field-Theory Correspondence Using High-Spin Operators

    SciTech Connect

    Benna, M. K.; Benvenuti, S.; Klebanov, I. R.; Scardicchio, A.

    2007-03-30

    In two remarkable recent papers the planar perturbative expansion was proposed for the universal function of the coupling appearing in the dimensions of high-spin operators of the N=4 super Yang-Mills theory. We study numerically the integral equation derived by Beisert, Eden, and Staudacher, which resums the perturbative series. In a confirmation of the anti-de Sitter-space/conformal-field-theory (AdS/CFT) correspondence, we find a smooth function whose two leading terms at strong coupling match the results obtained for the semiclassical folded string spinning in AdS{sub 5}. We also make a numerical prediction for the third term in the strong coupling series.

  14. Effective field theory program for conformal quantum anomalies

    SciTech Connect

    Camblong, Horacio E.; Epele, Luis N.; Fanchiotti, Huner; Canal, Carlos A. Garcia; Ordonez, Carlos R.

    2005-09-15

    The emergence of conformal states is established for any problem involving a domain of scales where the long-range SO(2,1) conformally invariant interaction is applicable. Whenever a clear-cut separation of ultraviolet and infrared cutoffs is in place, this renormalization mechanism is capable of producing binding in the strong-coupling regime. A realization of this phenomenon, in the form of dipole-bound anions, is discussed.

  15. Reliability of the Optimized Perturbation Theory for scalar fields at finite temperature

    SciTech Connect

    Farias, R. L.; Teixeira, D. L. Jr.; Ramos, R. O.

    2013-03-25

    The thermodynamics of a massless scalar field with a quartic interaction is studied up to third order in the Optimized Perturbation Theory (OPT) method. A comparison with other nonperturbative approaches is performed such that the reliability of OPT is accessed.

  16. On estimating perturbative coefficients in quantum field theory and statistical physics

    SciTech Connect

    Samuel, M.A. |

    1994-05-01

    The authors present a method for estimating perturbative coefficients in quantum field theory and Statistical Physics. They are able to obtain reliable error-bars for each estimate. The results, in all cases, are excellent.

  17. Noncommutative Geometry in M-Theory and Conformal Field Theory

    SciTech Connect

    Morariu, Bogdan

    1999-05-01

    In the first part of the thesis I will investigate in the Matrix theory framework, the subgroup of dualities of the Discrete Light Cone Quantization of M-theory compactified on tori, which corresponds to T-duality in the auxiliary Type II string theory. After a review of matrix theory compactification leading to noncommutative supersymmetric Yang-Mills gauge theory, I will present solutions for the fundamental and adjoint sections on a two-dimensional twisted quantum torus and generalize to three-dimensional twisted quantum tori. After showing how M-theory T-duality is realized in supersymmetric Yang-Mills gauge theories on dual noncommutative tori I will relate this to the mathematical concept of Morita equivalence of C*-algebras. As a further generalization, I consider arbitrary Ramond-Ramond backgrounds. I will also discuss the spectrum of the toroidally compactified Matrix theory corresponding to quantized electric fluxes on two and three tori. In the second part of the thesis I will present an application to conformal field theory involving quantum groups, another important example of a noncommutative space. First, I will give an introduction to Poisson-Lie groups and arrive at quantum groups using the Feynman path integral. I will quantize the symplectic leaves of the Poisson-Lie group SU(2)*. In this way we obtain the unitary representations of U{sub q}(SU(2)). I discuss the X-structure of SU(2)* and give a detailed description of its leaves using various parametrizations. Then, I will introduce a new reality structure on the Heisenberg double of Fun{sub q} (SL(N,C)) for q phase, which can be interpreted as the quantum phase space of a particle on the q-deformed mass-hyperboloid. I also present evidence that the above real form describes zero modes of certain non-compact WZNW-models.

  18. Short perturbations of cosmic ray intensity and electric field in atmosphere

    NASA Technical Reports Server (NTRS)

    Alexeyenko, V. V.; Chudakov, A. E.; Sborshikov, V. G.; Tizengauzen, V. A.

    1985-01-01

    Short perturbations of cosmic ray intensity were found to be a common phenomenon. Its meteorological origin and correlation with electric field is established. The phenomenon can be explained by the electric field if the strength of this field at high altitudes is much bigger than the measured one at surface.

  19. Perturbative quantum field theory in the framework of the fermionic projector

    SciTech Connect

    Finster, Felix

    2014-04-15

    We give a microscopic derivation of perturbative quantum field theory, taking causal fermion systems and the framework of the fermionic projector as the starting point. The resulting quantum field theory agrees with standard quantum field theory on the tree level and reproduces all bosonic loop diagrams. The fermion loops are described in a different formalism in which no ultraviolet divergences occur.

  20. Projector Augmented-Wave formulation of response to strain and electric field perturbation within the density-functional perturbation theory

    NASA Astrophysics Data System (ADS)

    Martin, Alexandre; Torrent, Marc; Caracas, Razvan

    2015-03-01

    A formulation of the response of a system to strain and electric field perturbations in the pseudopotential-based density functional perturbation theory (DFPT) has been proposed by D.R Hamman and co-workers. It uses an elegant formalism based on the expression of DFT total energy in reduced coordinates, the key quantity being the metric tensor and its first and second derivatives. We propose to extend this formulation to the Projector Augmented-Wave approach (PAW). In this context, we express the full elastic tensor including the clamped-atom tensor, the atomic-relaxation contributions (internal stresses) and the response to electric field change (piezoelectric tensor and effective charges). With this we are able to compute the elastic tensor for all materials (metals and insulators) within a fully analytical formulation. The comparison with finite differences calculations on simple systems shows an excellent agreement. This formalism has been implemented in the plane-wave based DFT ABINIT code. We apply it to the computation of elastic properties and seismic-wave velocities of iron with impurity elements. By analogy with the materials contained in meteorites, tested impurities are light elements (H, O, C, S, Si).

  1. Correspondence between Asymptotically Flat Spacetimes and Nonrelativistic Conformal Field Theories

    SciTech Connect

    Bagchi, Arjun

    2010-10-22

    We find a surprising connection between asymptotically flat spacetimes and nonrelativistic conformal systems in one lower dimension. The Bondi-Metzner-Sachs (BMS) group is the group of asymptotic isometries of flat Minkowski space at null infinity. This is known to be infinite dimensional in three and four dimensions. We show that the BMS algebra in 3 dimensions is the same as the 2D Galilean conformal algebra (GCA) which is of relevance to nonrelativistic conformal symmetries. We further justify our proposal by looking at a Penrose limit on a radially infalling null ray inspired by nonrelativistic scaling and obtain a flat metric. The BMS{sub 4} algebra is also discussed and found to be the same as another class of GCA, called semi-GCA, in three dimensions. We propose a general BMS-GCA correspondence. Some consequences are discussed.

  2. The characteristics of quasistatic electric field perturbations observed by DEMETER satellite before large earthquakes

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Shen, X.; Zhao, S.; Yao, Lu; Ouyang, X.; Qian, J.

    2014-01-01

    This paper presents new results after processing the ULF electric field (DC-15 Hz) observed by DEMETER satellite (h = 660-710 km). Typical perturbations were picked up in quasistatic electric field around some large earthquakes in 2010 at first. And then, 27 earthquakes were selected to be analyzed on quasistatic electric field in two seismic regions of Indonesia and Chile at equatorial and middle latitude area respectively. Three-component electric field data related to earthquakes were collected along all the up-orbits (in local nighttime) in a limited distance of 2000 km to the epicenters during 9 days with 7 days before and 1 day after those cases, and totally 57 perturbations were found around them. All the results show that the amplitude of quasistatic electric field perturbations varies from 1.5 to 16 mV/m in the upper ionosphere, mostly smaller than 10 mV/m. And the perturbations were mainly located just over the epicentral area or at the end of seismic faults constructed by a series of earthquakes where electromagnetic emissions may be easily formed during preparation and development processes of seismic sequences. Among all 27 cases, there are 10 earthquakes with perturbations occurring just one day before, which demonstrates the close correlation in time domain between quasistatic electric field in ionosphere and large earthquakes. Finally, combined with in situ observation of plasma parameters, the coupling mechanism of quasistatic electric field in different earth spheres was discussed.

  3. Non-perturbative methods in relativistic field theory

    SciTech Connect

    Franz Gross

    2013-03-01

    This talk reviews relativistic methods used to compute bound and low energy scattering states in field theory, with emphasis on approaches that John Tjon and I discussed (and argued about) together. I compare the Bethe–Salpeter and Covariant Spectator equations, show some applications, and then report on some of the things we have learned from the beautiful Feynman–Schwinger technique for calculating the exact sum of all ladder and crossed ladder diagrams in field theory.

  4. Proton radiography as an electromagnetic field and density perturbation diagnostic (invited)

    SciTech Connect

    Mackinnon, A.J.; Patel, P.K.; Town, R.P.; Edwards, M.J.; Phillips, T.; Lerner, S.C.; Price, D.W.; Hicks, D.; Key, M.H.; Hatchett, S.; Wilks, S.C.; Borghesi, M.; Romagnani, L.; Kar, S.; Toncian, T.; Pretzler, G.; Willi, O.; Koenig, M.; Martinolli, E.; Lepape, S.

    2004-10-01

    Laser driven proton beams have been used to diagnose transient fields and density perturbations in laser produced plasmas. Grid deflectometry techniques have been applied to proton radiography to obtain precise measurements of proton beam angles caused by electromagnetic fields in laser produced plasmas. Application of proton radiography to laser driven implosions has demonstrated that density conditions in compressed media can be diagnosed with million electron volt protons. This data has shown that proton radiography can provide unique insight into transient electromagnetic fields in super critical density plasmas and provide a density perturbation diagnostics in compressed matter.

  5. Virasoro conformal blocks and thermality from classical background fields

    DOE PAGESBeta

    Fitzpatrick, A. Liam; Kaplan, Jared; Walters, Matthew T.

    2015-11-30

    We show that in 2d CFTs at large central charge, the coupling of the stress tensor to heavy operators can be re-absorbed by placing the CFT in a non-trivial background metric. This leads to a more precise computation of the Virasoro conformal blocks between heavy and light operators, which are shown to be equivalent to global conformal blocks evaluated in the new background. We also generalize to the case where the operators carry U(1) charges. The refined Virasoro blocks can be used as the seed for a new Virasoro block recursion relation expanded in the heavy-light limit. Furthermore, we commentmore » on the implications of our results for the universality of black hole thermality in AdS3 , or equivalently, the eigenstate thermalization hypothesis for CFT2 at large central charge.« less

  6. Virasoro conformal blocks and thermality from classical background fields

    SciTech Connect

    Fitzpatrick, A. Liam; Kaplan, Jared; Walters, Matthew T.

    2015-11-30

    We show that in 2d CFTs at large central charge, the coupling of the stress tensor to heavy operators can be re-absorbed by placing the CFT in a non-trivial background metric. This leads to a more precise computation of the Virasoro conformal blocks between heavy and light operators, which are shown to be equivalent to global conformal blocks evaluated in the new background. We also generalize to the case where the operators carry U(1) charges. The refined Virasoro blocks can be used as the seed for a new Virasoro block recursion relation expanded in the heavy-light limit. Furthermore, we comment on the implications of our results for the universality of black hole thermality in AdS3 , or equivalently, the eigenstate thermalization hypothesis for CFT2 at large central charge.

  7. Nonlinear perturbations of cosmological scalar fields with non-standard kinetic terms

    NASA Astrophysics Data System (ADS)

    Renaux-Petel, Sébastien; Tasinato, Gianmassimo

    2009-01-01

    We adopt a covariant formalism to derive exact evolution equations for nonlinear perturbations, in a universe dominated by two scalar fields. These scalar fields are characterized by non-canonical kinetic terms and an arbitrary field space metric, a situation typically encountered in inflationary models inspired by string theory. We decompose the nonlinear scalar perturbations into adiabatic and entropy modes, generalizing the definition adopted in the linear theory, and we derive the corresponding exact evolution equations. We also obtain a nonlinear generalization of the curvature perturbation on uniform density hypersurfaces, showing that on large scales it is sourced only by the nonlinear version of the entropy perturbation. We then expand these equations to second order in the perturbations, using a coordinate based formalism. Our results are relatively compact and elegant and enable one to identify the new effects coming from the non-canonical structure of the scalar fields Lagrangian. We also explain how to analyze, in our formalism, the interesting scenario of multi-field Dirac-Born-Infeld inflation.

  8. Close intramolecular sulfur-oxygen contacts: modified force field parameters for improved conformation generation.

    PubMed

    Lupyan, Dmitry; Abramov, Yuriy A; Sherman, Woody

    2012-11-01

    The Cambridge Structural Database (CSD) offers an excellent data source to study small molecule conformations and molecular interactions. We have analyzed 130 small molecules from the CSD containing an intramolecular sulfur-oxygen distance less than the sum of their van der Waals (vdW) radii. Close S···O distances are observed in several important medicinal chemistry motifs (e.g. a carbonyl oxygen connected by a carbon or nitrogen linker to a sulfur) and are not treated well with existing parameters in the MMFFs or OPLS_2005 force fields, resulting in suboptimal geometries and energetics. In this work, we develop modified parameters for the OPLS_2005 force field to better treat this specific interaction in order to generate conformations close to those found in the CSD structures. We use a combination of refitting a force field torsional parameter, adding a specific atom pair vdW term, and attenuating the electrostatic interactions to obtain an improvement in the accuracy of geometry minimizations and conformational searches for these molecules. Specifically, in a conformational search 58 % of the cases produced a conformation less than 0.25 Å from the CSD crystal conformation with the modified OPLS force field parameters developed in this work. In contrast, 25 and 37 % produced a conformation less than 0.25 Å with the MMFFs and OPLS_2005 force fields, respectively. As an application of the new parameters, we generated conformations for the tyrosine kinase inhibitor axitinib (trade name Inlyta) that could be correctly repacked into three observed polymorphic structures, which was not possible with conformations generated using MMFFs or OPLS_2005. The improved parameters can be mapped directly onto physical characteristics of the systems that are treated inadequately with the molecular mechanics force fields used in this study and potentially other force fields as well. PMID:23053737

  9. Effects of Large-scale Non-axisymmetric Perturbations in the Mean-field Solar Dynamo.

    NASA Astrophysics Data System (ADS)

    Pipin, V. V.; Kosovichev, A. G.

    2015-11-01

    We explore the response of a nonlinear non-axisymmetric mean-field solar dynamo model to shallow non-axisymmetric perturbations. After a relaxation period, the amplitude of the non-axisymmetric field depends on the initial condition, helicity conservation, and the depth of perturbation. It is found that a perturbation that is anchored at 0.9 R⊙ has a profound effect on the dynamo process, producing a transient magnetic cycle of the axisymmetric magnetic field, if it is initiated at the growing phase of the cycle. The non-symmetric, with respect to the equator, perturbation results in a hemispheric asymmetry of the magnetic activity. The evolution of the axisymmetric and non-axisymmetric fields depends on the turbulent magnetic Reynolds number Rm. In the range of Rm = 104-106 the evolution returns to the normal course in the next cycle, in which the non-axisymmetric field is generated due to a nonlinear α-effect and magnetic buoyancy. In the stationary state, the large-scale magnetic field demonstrates a phenomenon of “active longitudes” with cyclic 180° “flip-flop” changes of the large-scale magnetic field orientation. The flip-flop effect is known from observations of solar and stellar magnetic cycles. However, this effect disappears in the model, which includes the meridional circulation pattern determined by helioseismology. The rotation rate of the non-axisymmetric field components varies during the relaxation period and carries important information about the dynamo process.

  10. Relative unitary implementability of perturbed quantum field dynamics on de-Sitter space

    NASA Astrophysics Data System (ADS)

    Poon, Gary K.

    In this article, we study the quantum dynamics of a Klein-Gordon field on de-Sitter space. We prove time evolution is not unitarily implementable. We also consider a Klein-Gordon field perturbed by a local potential V. In this case we prove that the deviation from the V = 0 dynamics is unitarily implementable.

  11. Evolution operators in conformal field theories and conformal mappings: Entanglement Hamiltonian, the sine-square deformation, and others

    NASA Astrophysics Data System (ADS)

    Wen, Xueda; Ryu, Shinsei; Ludwig, Andreas W. W.

    2016-06-01

    By making use of conformal mapping, we construct various time-evolution operators in (1+1)-dimensional conformal field theories (CFTs), which take the form ∫d x f (x )H (x ) , where H (x ) is the Hamiltonian density of the CFT and f (x ) is an envelope function. Examples of such deformed evolution operators include the entanglement Hamiltonian and the so-called sine-square deformation of the CFT. Within our construction, the spectrum and the (finite-size) scaling of the level spacing of the deformed evolution operator are known exactly. Based on our construction, we also propose a regularized version of the sine-square deformation, which, in contrast to the original sine-square deformation, has the spectrum of the CFT defined on a spatial circle of finite circumference L , and for which the level spacing scales as 1 /L2 , once the circumference of the circle and the regularization parameter are suitably adjusted.

  12. Higher spin conformal geometry in three dimensions and prepotentials for higher spin gauge fields

    NASA Astrophysics Data System (ADS)

    Henneaux, Marc; Hörtner, Sergio; Leonard, Amaury

    2016-01-01

    We study systematically the conformal geometry of higher spin bosonic gauge fields in three spacetime dimensions. We recall the definition of the Cotton tensor for higher spins and establish a number of its properties that turn out to be key in solving in terms of prepotentials the constraint equations of the Hamiltonian (3 + 1) formulation of four-dimensional higher spin gauge fields. The prepotentials are shown to exhibit higher spin conformal symmetry. Just as for spins 1 and 2, they provide a remarkably simple, manifestly duality invariant formulation of the theory. While the higher spin conformal geometry is developed for arbitrary bosonic spin, we explicitly perform the Hamiltonian analysis and derive the solution of the constraints only in the illustrative case of spin 3. In a separate publication, the Hamiltonian analysis in terms of prepotentials is extended to all bosonic higher spins using the conformal tools of this paper, and the same emergence of higher spin conformal symmetry is confirmed.

  13. Setting the renormalization scale in perturbative QCD: Comparisons of the principle of maximum conformality with the sequential extended Brodsky-Lepage-Mackenzie approach

    NASA Astrophysics Data System (ADS)

    Ma, Hong-Hao; Wu, Xing-Gang; Ma, Yang; Brodsky, Stanley J.; Mojaza, Matin

    2015-05-01

    A key problem in making precise perturbative QCD (pQCD) predictions is how to set the renormalization scale of the running coupling unambiguously at each finite order. The elimination of the uncertainty in setting the renormalization scale in pQCD will greatly increase the precision of collider tests of the Standard Model and the sensitivity to new phenomena. Renormalization group invariance requires that predictions for observables must also be independent on the choice of the renormalization scheme. The well-known Brodsky-Lepage-Mackenzie (BLM) approach cannot be easily extended beyond next-to-next-to-leading order of pQCD. Several suggestions have been proposed to extend the BLM approach to all orders. In this paper we discuss two distinct methods. One is based on the "Principle of Maximum Conformality" (PMC), which provides a systematic all-orders method to eliminate the scale and scheme ambiguities of pQCD. The PMC extends the BLM procedure to all orders using renormalization group methods; as an outcome, it significantly improves the pQCD convergence by eliminating renormalon divergences. An alternative method is the "sequential extended BLM" (seBLM) approach, which has been primarily designed to improve the convergence of pQCD series. The seBLM, as originally proposed, introduces auxiliary fields and follows the pattern of the β0 -expansion to fix the renormalization scale. However, the seBLM requires a recomputation of pQCD amplitudes including the auxiliary fields; due to the limited availability of calculations using these auxiliary fields, the seBLM has only been applied to a few processes at low orders. In order to avoid the complications of adding extra fields, we propose a modified version of seBLM which allows us to apply this method to higher orders. We then perform detailed numerical comparisons of the two alternative scale-setting approaches by investigating their predictions for the annihilation cross section ratio Re+e- at four-loop order in pQCD.

  14. In vivo static field perturbations in magnetic resonance

    NASA Astrophysics Data System (ADS)

    Koch, Kevin Matthew

    2007-12-01

    Fundamental magnetic resonance (MR) theory assumes the spatial homogeneity of a dominating static magnetic field B = B 0ẑ. When this assumption is violated, a myriad of artifacts and compromising factors are introduced to MR spectra and images. Though in vivo nuclear magnetic resonance (NMR) is one of the most widely used scientific and diagnostic tools in medicine and biology, it remains haunted by the continual and persistant ghost of B0 inhomogeneity. An inclusive list of in vivo NMR applications severely impacted by B0 inhomogeneity could go on ad infinitum. Examples of such applications include neurosurgical utility in functional magnetic resonance imaging (fMRI), cerebral metabolic flux mapping, cerebral diffusion tractography, and abdominal diagnostic imaging. Given this wide impact on in vivo NMR, significant effort has been exerted in developing methods of compensating B0 inhomogeneity. Complicating this task is the sample-specific nature of in vivo B 0 inhomogeneity and its exacerbation with ever increasing B 0 field strengths. State of the art B 0 inhomogeneity compensation is currently at a critical juncture where homogenization demands are overwhelming the outer capabilities of existing technology and methods. This thesis addresses the B 0 inhomogeneity problem in the mammalian brain and presents novel solutions to the homogenization technology stalemate.

  15. Exact conformal blocks for the W-algebras, twist fields and isomonodromic deformations

    NASA Astrophysics Data System (ADS)

    Gavrylenko, P.; Marshakov, A.

    2016-02-01

    We consider the conformal blocks in the theories with extended conformal W-symmetry for the integer Virasoro central charges. We show that these blocks for the generalized twist fields on sphere can be computed exactly in terms of the free field theory on the covering Riemann surface, even for a non-abelian monodromy group. The generalized twist fields are identified with particular primary fields of the W-algebra, and we propose a straightforward way to compute their W-charges. We demonstrate how these exact conformal blocks can be effectively computed using the technique arisen from the gauge theory/CFT correspondence. We discuss also their direct relation with the isomonodromic tau-function for the quasipermutation monodromy data, which can be an encouraging step on the way of definition of generic conformal blocks for W-algebra using the isomonodromy/CFT correspondence.

  16. Cosmological perturbations in antigravity

    NASA Astrophysics Data System (ADS)

    Oltean, Marius; Brandenberger, Robert

    2014-10-01

    We compute the evolution of cosmological perturbations in a recently proposed Weyl-symmetric theory of two scalar fields with oppositely signed conformal couplings to Einstein gravity. It is motivated from the minimal conformal extension of the standard model, such that one of these scalar fields is the Higgs while the other is a new particle, the dilaton, introduced to make the Higgs mass conformally symmetric. At the background level, the theory admits novel geodesically complete cyclic cosmological solutions characterized by a brief period of repulsive gravity, or "antigravity," during each successive transition from a big crunch to a big bang. For simplicity, we consider scalar perturbations in the absence of anisotropies, with potential set to zero and without any radiation. We show that despite the necessarily wrong-signed kinetic term of the dilaton in the full action, these perturbations are neither ghostlike nor tachyonic in the limit of strongly repulsive gravity. On this basis, we argue—pending a future analysis of vector and tensor perturbations—that, with respect to perturbative stability, the cosmological solutions of this theory are viable.

  17. Conformal field theory dual of the RS model with gauge fields in the bulk

    NASA Astrophysics Data System (ADS)

    Agashe, K.; Delgado, A.

    2003-02-01

    It has been conjectured that the (weakly coupled) Randall-Sundrum (RS) model with gauge fields in the bulk is dual to a (strongly coupled) 4D conformal field theory (CFT) with an UV cutoff and in which global symmetries of the CFT are gauged. We elucidate features of this dual CFT which are crucial for a complete understanding of the proposed duality. We argue that the limit of no (or small) brane-localized kinetic term for bulk gauge field on the RS side (often studied in the literature) is dual to no bare kinetic term for the gauge field which is coupled to the CFT global current. In this limit, the kinetic term for this gauge field in the dual CFT is “induced” by CFT loops. Then, this CFT loop contribution to the gauge field 1PI two-point function is dual (on the RS side) to the full gauge propagator (i.e., including the contribution of Kaluza-Klein and zero modes) with both external points on the Planck brane. We also emphasize that loop corrections to the gauge coupling on the RS side are dual to subleading effects in a large-N expansion on the CFT side; these subleading corrections to the gauge coupling in the dual CFT are (in general) sensitive to the strong dynamics of the CFT.

  18. Dynamics of Peccei-Quinn breaking field after inflation and axion isocurvature perturbations

    SciTech Connect

    Harigaya, Keisuke; Ibe, Masahiro; Kawasaki, Masahiro; Yanagida, Tsutomu T.

    2015-11-04

    The Peccei-Quinn mechanism suffers from the problem of the isocurvature perturbations. The isocurvature perturbations are suppressed if the Peccei-Quinn breaking scale is large during inflation. The oscillation of the Peccei-Quinn breaking field after inflation, however, leads to the formation of domain walls due to the parametric resonance effect. In this paper, we discuss the evolution of the Peccei-Quinn breaking field after inflation in detail, and propose a model where the parametric resonance is ineffective and hence domain walls are not formed. We also discuss consistency of our model with supersymmetric theory.

  19. Ideal plasma response to vacuum magnetic fields with resonant magnetic perturbations in non-axisymmetric tokamaks

    SciTech Connect

    Kim, Kimin; Ahn, J-W; Scotti, F.; Park, J-K; Menard, J. E.

    2015-09-03

    Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifies the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.

  20. Ideal plasma response to vacuum magnetic fields with resonant magnetic perturbations in non-axisymmetric tokamaks

    SciTech Connect

    Kim, Kimin; Ahn, J. -W.; Scotti, F.; Park, J. -K.; Menard, J. E.

    2015-09-03

    Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifies the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Furthermore, amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.

  1. Evolution of perturbations in distinct classes of canonical scalar field models of dark energy

    SciTech Connect

    Jassal, H. K.

    2010-04-15

    Dark energy must cluster in order to be consistent with the equivalence principle. The background evolution can be effectively modeled by either a scalar field or by a barotropic fluid. The fluid model can be used to emulate perturbations in a scalar field model of dark energy, though this model breaks down at large scales. In this paper we study evolution of dark energy perturbations in canonical scalar field models: the classes of thawing and freezing models. The dark energy equation of state evolves differently in these classes. In freezing models, the equation of state deviates from that of a cosmological constant at early times. For thawing models, the dark energy equation of state remains near that of the cosmological constant at early times and begins to deviate from it only at late times. Since the dark energy equation of state evolves differently in these classes, the dark energy perturbations too evolve differently. In freezing models, since the equation of state deviates from that of a cosmological constant at early times, there is a significant difference in evolution of matter perturbations from those in the cosmological constant model. In comparison, matter perturbations in thawing models differ from the cosmological constant only at late times. This difference provides an additional handle to distinguish between these classes of models and this difference should manifest itself in the integrated Sachs-Wolfe effect.

  2. Ambipolar radial electric field generated by anomalous transport induced by magnetic perturbations

    NASA Astrophysics Data System (ADS)

    Chen, Dunqiang; Zhu, Siqiang; Zhang, Debing; Wang, Shaojie

    2016-05-01

    The anomalous particle transport induced by magnetic perturbations in a tokamak is investigated. The correlation between the radial position and the kinetic energy of electrons, Dr K=-e ErDr r , is predicted theoretically and is verified by simulations in the presence of a mean radial electric field. This correlation leads to a radial particle flux produced by the radial electric field. The ambipolar radial electric field can thus be predicted by using the ambipolarity condition Γri=Γre .

  3. On the reach of perturbative methods for dark matter density fields

    NASA Astrophysics Data System (ADS)

    Baldauf, Tobias; Schaan, Emmanuel; Zaldarriaga, Matias

    2016-03-01

    We study the mapping from Lagrangian to Eulerian space in the context of the Effective Field Theory (EFT) of Large Scale Structure. We compute Lagrangian displacements with Lagrangian Perturbation Theory (LPT) and perform the full non-perturbative transformation from displacement to density. When expanded up to a given order, this transformation reproduces the standard Eulerian Perturbation Theory (SPT) at the same order. However, the full transformation from displacement to density also includes higher order terms. These terms explicitly resum long wavelength motions, thus making the resulting density field better correlated with the true non-linear density field. As a result, the regime of validity of this approach is expected to extend that of the Eulerian EFT, and match that of the IR-resummed Eulerian EFT. This approach thus effectively enables a test of the IR-resummed EFT at the field level. We estimate the size of stochastic, non-perturbative contributions to the matter density power spectrum. We find that in our highest order calculation, at redshift z = 0 the power spectrum of the density field is reproduced with an accuracy of 1% (10%) up to k = 0.25 hMpc-1 (k = 0.46 hMpc-1). We believe that the dominant source of the remaining error is the stochastic contribution. Unfortunately, on these scales the stochastic term does not yet scale as k4 as it does in the very low k regime. Thus, modeling this contribution might be challenging.

  4. Non-Gaussianity at tree and one-loop levels from vector field perturbations

    SciTech Connect

    Valenzuela-Toledo, Cesar A.; Rodriguez, Yeinzon; Lyth, David H.

    2009-11-15

    We study the spectrum P{sub {zeta}} and bispectrum B{sub {zeta}} of the primordial curvature perturbation {zeta} when the latter is generated by scalar and vector field perturbations. The tree-level and one-loop contributions from vector field perturbations are worked out considering the possibility that the one-loop contributions may be dominant over the tree-level terms [both (either) in P{sub {zeta}} and (or) in B{sub {zeta}}] and vice versa. The level of non-Gaussianity in the bispectrum, f{sub NL}, is calculated and related to the level of statistical anisotropy in the power spectrum, g{sub {zeta}}. For very small amounts of statistical anisotropy in the power spectrum, the level of non-Gaussianity may be very high, in some cases exceeding the current observational limit.

  5. Membrane potential perturbations induced in tissue cells by pulsed electric fields

    SciTech Connect

    Cooper, M.S.

    1995-09-01

    Pulsed electric fields directly influence the electrophysiology of tissue cells by transiently perturbing their transmembrane potential. To determine the magnitude and time course of this interaction, electronic cable theory was used to calculate the membrane potential perturbations induced in tissue cells by a spatially uniform, pulsed electric field. Analytic solutions were obtained that predict shifts in membrane potential along the length of cells as a function of time in response to an electrical pulse. For elongated tissue cells, or groups of tissue cells that are couple electronically by gap junctions, significant hyperpolarizations and depolarizations can result form millisecond applications of electric fields with strengths on the order of 10--100 mV/cm. The results illustrate the importance of considering cellular cable parameters in assessing the effects of transient electric fields on biological systems, as well as in predicting the efficacy of pulsed electric fields in medical treatments.

  6. Modelling of plasma response to resonant magnetic perturbation fields in MAST and ITER

    NASA Astrophysics Data System (ADS)

    Liu, Yueqiang; Kirk, A.; Gribov, Y.; Gryaznevich, M. P.; Hender, T. C.; Nardon, E.

    2011-08-01

    The resonant magnetic perturbation (RMP) fields, including the plasma response, are computed within a linear, full toroidal, single-fluid resistive magnetohydrodynamic (MHD) model, and under realistic plasma conditions for MAST and ITER. The response field is found to be considerably reduced, compared with the vacuum field produced by the magnetic perturbation coils. This field reduction relies strongly on the screening effect from the toroidal plasma rotation. Computations also quantify three-dimensional (3D) distortions of the plasma surface, caused by RMP fields. A correlation is found between the computed mode structures, the plasma surface displacement and the observed density pump-out effect in MAST experiments. Generally, the density pump-out tends to occur when the surface displacement peaks near the X-points.

  7. Peak deconvolution in high-field asymmetric waveform ion mobility spectrometry (FAIMS) to characterize macromolecular conformations

    NASA Astrophysics Data System (ADS)

    Robinson, Errol W.; Sellon, Rachel E.; Williams, Evan R.

    2007-01-01

    Protonated poly(ethylene glycol), produced by electrospray ionization (ESI), with molecular weights ranging from 0.3 to 5 kDa and charge states from 1+ to 7+ were characterized using high-field asymmetric waveform ion mobility spectrometry (FAIMS). Results for all but some of the 3+ and 4+ charge states are consistent with a single gas-phase conformer or family of unresolved conformers for each of these charge states. The FAIMS compensation voltage scans resulted in peaks that could be accurately fit with a single Gaussian for each peak. The peak widths increase linearly with compensation voltage for maximum ion transmission but do not depend on m/z or molecular weight. Fitting parameters obtained from the poly(ethylene glycol) data were used to analyze conformations of oxidized and reduced lysozyme formed from different solutions. For oxidized lysozyme formed from a buffered aqueous solution, a single conformer (or group of unresolved conformers) was observed for the 7+ and 8+ charge states. Two conformers were observed for the 9+ and 10+ charge states formed from more denaturing solutions. Data for the fully reduced form indicate the existence of up to three different conformers for each charge state produced directly by ESI and a general progression from a more extended to a more folded structure with decreasing charge state. These results are consistent with those obtained previously by proton-transfer reactivity and drift tube ion mobility experiments, although more conformers were identified for the fully reduced form of lysozyme using FAIMS.

  8. Conformally invariant 'massless' spin-2 field in the de Sitter universe

    SciTech Connect

    Dehghani, M.; Rouhani, S.; Takook, M. V.; Tanhayi, M. R.

    2008-03-15

    A massless spin-2 field equation in de Sitter space, which is invariant under the conformal transformation, has been obtained. The framework utilized is the symmetric rank-2 tensor field of the conformal group. Our method is based on the group theoretical approach and six-cone formalism, initially introduced by Dirac. Dirac's six-cone is used to obtain conformally invariant equations on de Sitter space. The solution of the physical sector of massless spin-2 field (linear gravity) in de Sitter ambient space is written as a product of a generalized polarization tensor and a massless minimally coupled scalar field. Similar to the minimally coupled scalar field, for quantization of this sector, the Krein space quantization is utilized. We have calculated the physical part of the linear graviton two-point function. This two-point function is de Sitter invariant and free of pathological large-distance behavior.

  9. Anti-de Sitter-Space/Conformal-Field-Theory Casimir Energy for Rotating Black Holes

    SciTech Connect

    Gibbons, G.W.; Perry, M.J.; Pope, C.N.

    2005-12-02

    We show that, if one chooses the Einstein static universe as the metric on the conformal boundary of Kerr-anti-de Sitter spacetime, then the Casimir energy of the boundary conformal field theory can easily be determined. The result is independent of the rotation parameters, and the total boundary energy then straightforwardly obeys the first law of thermodynamics. Other choices for the metric on the conformal boundary will give different, more complicated, results. As an application, we calculate the Casimir energy for free self-dual tensor multiplets in six dimensions and compare it with that of the seven-dimensional supergravity dual. They differ by a factor of 5/4.

  10. Perturbative path-integral study of active- and passive-tracer diffusion in fluctuating fields

    NASA Astrophysics Data System (ADS)

    Démery, Vincent; Dean, David S.

    2011-07-01

    We study the effective diffusion constant of a Brownian particle linearly coupled to a thermally fluctuating scalar field. We use a path-integral method to compute the effective diffusion coefficient perturbatively to lowest order in the coupling constant. This method can be applied to cases where the field is affected by the particle (an active tracer) and cases where the tracer is passive. Our results are applicable to a wide range of physical problems, from a protein diffusing in a membrane to the dispersion of a passive tracer in a random potential. In the case of passive diffusion in a scalar field, we show that the coupling to the field can, in some cases, speed up the diffusion corresponding to a form of stochastic resonance. Our results on passive diffusion are also confirmed via a perturbative calculation of the probability density function of the particle in a Fokker-Planck formulation of the problem. Numerical simulations on simplified systems corroborate our results.

  11. Comparison of perturbations in fluid and scalar field models of dark energy

    SciTech Connect

    Jassal, H. K.

    2009-06-15

    We compare perturbations in a fluid model of dark energy with those in a scalar field. As compared to the {lambda}CDM model, large scale matter power spectrum is suppressed in fluid model as well as in a generic quintessence dark energy model. To check the efficacy of fluid description of dark energy in emulating a scalar field, we consider a potential which gives the same background evolution as a fluid with a constant equation of state. We show that for sub-Hubble scales, a fluid model effectively emulates a scalar field model. At larger scales, where dark energy perturbations may play a significant role, the fluid analogy breaks down and the evolution of matter density contrast depends on individual scalar field models.

  12. Conformal fields and the quantum state of the universe

    NASA Astrophysics Data System (ADS)

    Kamenshchik, Alexander Y.

    2012-02-01

    The creation of a quantum Universe is described by a density matrix which yields an ensemble of universes with the cosmological constant limited to a bounded range Λmin <= Λ <= Λmax. The domain Λ < Λmin is ruled out by a cosmological bootstrap requirement (the self-consistent back reaction of hot matter). The upper cutoff results from the quantum effects of vacuum energy and the conformal anomaly mediated by a special ghost-avoidance renormalization. The cutoff Λmax establishes a new quantum scale - the accumulation point of an infinite sequence of garland-type instantons. The cosmological evolution starting with these initial conditions also have some new features: the stage of cosmic acceleration can be followed by a big boost singularity - a rapid growth up to infinity of the scale factor acceleration parameter. A correspondence between the 4-dimensional modified quantum Freidmann equations and the Friedmann equations arising in the context of 5-dimensional classical cosmological models was established.

  13. Gauge invariant approach to low-spin anomalous conformal currents and shadow fields

    SciTech Connect

    Metsaev, R. R.

    2011-05-15

    Conformal low-spin anomalous currents and shadow fields in flat space-time of dimensions greater than or equal to four are studied. The gauge invariant formulation for such currents and shadow fields is developed. Gauge symmetries are realized by involving Stueckelberg and auxiliary fields. The gauge invariant differential constraints for anomalous currents and shadow fields and the realization of global conformal symmetries are obtained. Gauge invariant two-point vertices for anomalous shadow fields are also obtained. In the Stueckelberg gauge frame, these gauge invariant vertices become the standard two-point vertices of conformal field theory. Light-cone gauge two-point vertices of the anomalous shadow fields are derived. The AdS/CFT correspondence for anomalous currents and shadow fields and the respective normalizable and non-normalizable solutions of massive low-spin anti-de Sitter fields is studied. The bulk fields are considered in a modified de Donder gauge that leads to decoupled equations of motion. We demonstrate that leftover on-shell gauge symmetries of bulk massive fields correspond to gauge symmetries of boundary anomalous currents and shadow fields, while the modified (Lorentz) de Donder gauge conditions for bulk massive fields correspond to differential constraints for boundary anomalous currents and shadow fields.

  14. Quasi-conformal remapping for compensation of human visual field defects - Advances in image remapping for human field defects

    NASA Technical Reports Server (NTRS)

    Juday, Richard D.; Loshin, David S.

    1989-01-01

    Image coordinate transformations are investigated for possible use in a low vision aid for human patients. These patients typically have field defects with localized retinal dysfunction predominately central (age related maculopathy) or peripheral (retinitis pigmentosa). Previously simple eccentricity-only remappings which do not maintain conformality were shown. Initial attempts on developing images which hold quasi-conformality after remapping are presented. Although the quasi-conformal images may have less local distortion, there are discontinuities in the image which may counterindicate this type of transformation for the low vision application.

  15. Quasi-Conformal Remapping For Compensation Of Human Visual Field Defects: Advances In Image Remapping For Human Field Defects

    NASA Astrophysics Data System (ADS)

    Juday, Richard D.; Loshin, David S.

    1989-06-01

    We are investigating image coordinate transformations possibly to be used in a low vision aid for human patients. These patients typically have field defects with localized retinal dysfunction predominately central (age related maculopathy) or peripheral (retinitis pigmentosa). Previously we have shown simple eccentricity-only remappings which do not maintain conformality. In this report we present our initial attempts on developing images which hold quasi-conformality after remapping. Although the quasi-conformal images may have less local distortion, there are discontinuities in the image which may counterindicate this type of transformation for the low vision application.

  16. Conformally invariant spin-3/2 field equation in de Sitter space-time

    NASA Astrophysics Data System (ADS)

    Fatahi, N.

    2015-09-01

    In the previous paper (Behroozi et al., Phys Rev D 74:124014, 2006; Dehghani et al., Phys Rev D 77:064028, 2008), conformal invariance for massless tensor fields (scalar, vector and spin-2 fields) was studied and the solutions of their wave equations and two-point functions were obtained. In the present paper, conformally invariant wave equation for massless spinor field in de Sitter space-time has been obtained. For this propose, we use Dirac's six-cone formalism. The solutions of massless spin-1/2 and -3/2 equations, in the ambient space notation, have been calculated.

  17. On representations of conformal field theories and the construction of orbifolds

    NASA Astrophysics Data System (ADS)

    Montague, P. S.

    1996-09-01

    We consider representations of meromorphic bosonic chiral conformal field theories and demonstrate that such a representation is completely specified by a state within the theory. The necessary and sufficient conditions upon this state are derived and, because of their form, we show that we may extend the representation to a representation of a suitable larger conformal field theory. In particular, we apply this procedure to the (untwisted) lattice conformal field theories (i.e. corresponding to the propagation of a bosonic string on a torus), and deduce that Dong's proof of the uniqueness of the twisted representation for the reflection-twisted projection of the Leech lattice conformal field theory generalises to an arbitrary even (self-dual) lattice. As a consequence, we see that the reflection-twisted lattice theories of Dolan, Goddard and Montague are truly self-dual, extending the analogies with the theories of lattices and codes which were being pursued. Some comments are also made on the general concept of the definition of an orbifold of a conformal field theory in relation to this point of view.

  18. Fully non-linear cosmological perturbations of multicomponent fluid and field systems

    NASA Astrophysics Data System (ADS)

    Hwang, Jai-chan; Noh, Hyerim; Park, Chan-Gyung

    2016-09-01

    We present fully non-linear and exact cosmological perturbation equations in the presence of multiple components of fluids and minimally coupled scalar fields. We ignore the tensor-type perturbation. The equations are presented without taking the temporal gauge condition in the Friedmann background with general curvature and the cosmological constant. We include the anisotropic stress. Even in the absence of anisotropic stress of individual component, the multiple component nature introduces the anisotropic stress in the collective fluid quantities. We prove the Newtonian limit of multiple fluids in the zero-shear gauge and the uniform-expansion gauge conditions, present the Newtonian hydrodynamic equations in the presence of general relativistic pressure in the zero-shear gauge, and present the fully non-linear equations and the third-order perturbation equations of the non-relativistic pressure fluids in the CDM-comoving gauge.

  19. The ion-induced folding of the hammerhead ribozyme: core sequence changes that perturb folding into the active conformation.

    PubMed Central

    Bassi, G S; Murchie, A I; Lilley, D M

    1996-01-01

    The hammerhead ribozyme undergoes an ion-dependent folding process into the active conformation. We find that the folding can be blocked at specific stages by changes of sequence or functionality within the core. In the the absence of added metal ions, the global structure of the hammerhead is extended, with a large angle subtended between stems I and II. No core sequence changes appear to alter this geometry, consistent with an unstructured core under these conditions. Upon addition of low concentrations of magnesium ions, the hammerhead folds by an association of stems II and III, to include a large angle between them. This stage is inhibited or altered by mutations within the oligopurine sequence lying between stems II and III, and folding is completely prevented by an A14G mutation. Further increase in magnesium ion concentration brings about a second stage of folding in the natural sequence hammerhead, involving a reorientation of stem I, which rotates around into the same direction of stem II. Because this transition occurs over the same range of magnesium ion concentration over which the hammerhead ribozyme becomes active, it is likely that the final conformation is most closely related to the active form of the structure. Magnesium ion-dependent folding into this conformation is prevented by changes at G5, notably removal of the 2'-hydroxyl group and replacement of the base by cytidine. The ability to dissect the folding process by means of sequence changes suggests that two separate ion-dependent stages are involved in the folding of the hammerhead ribozyme into the active conformation. PMID:8752086

  20. Physical unitarity for a massive Yang-Mills theory without the Higgs field: A perturbative treatment

    NASA Astrophysics Data System (ADS)

    Kondo, Kei-Ichi; Suzuki, Kenta; Fukamachi, Hitoshi; Nishino, Shogo; Shinohara, Toru

    2013-01-01

    In a series of papers, we examine the physical unitarity in a massive Yang-Mills theory without the Higgs field in which the color gauge symmetry is not spontaneously broken and kept intact. For this purpose, we use a new framework proposed in the previous paper Kondo [arXiv:1208.3521] based on a nonperturbative construction of a non-Abelian field describing a massive spin-one vector boson field, which enables us to perform the perturbative and nonperturbative studies on the physical unitarity. In this paper, we present a new perturbative treatment for the physical unitarity after giving the general properties of the massive Yang-Mills theory. Then we reproduce the violation of physical unitarity in a transparent way. This paper is a preliminary work to the subsequent papers in which we present a nonperturbative framework to propose a possible scenario of restoring the physical unitarity in the Curci-Ferrari model.

  1. Curvature perturbation spectrum in two-field inflation with a turning trajectory

    SciTech Connect

    Pi, Shi; Sasaki, Misao E-mail: misao@yukawa.kyoto-u.ac.jp

    2012-10-01

    We revisit a two-component inflaton model with a turning trajectory in the field space, where the field slowly rolls down along the trajectory. We consider the case when the effective mass in the direction perpendicular to the trajectory, namely the isocurvature direction, is either of the same order as or much larger than the Hubble parameter. Assuming that the turning angular velocity is small, we compute analytically the corrections to the power spectrum of curvature perturbation caused by the mediation of the heavy isocurvature perturbation, and compare our analytic results with the numerical ones. Especially, when M{sub eff}{sup 2} >> H{sup 2}, we find that it is proportional to M{sub eff}{sup −2}. This result is consistent with the one obtained previously by an effective field theory approach.

  2. The perturbation correction factor of ionisation chambers in beta-radiation fields.

    PubMed

    Böhm, J

    1980-01-01

    In determining the absorbed dose in a solid medium by means of gas-filled ionisation chambers, the perturbation of the radiation field by the chamber needs to be taken into account. So far, an appropriate correction factor has neither been calculated nor measured for beta-radiation. This work describes its experimental determination for an extrapolation chamber and beta-radiation fields of 147Pm, 204Tl, and 90Sr + 90Y. The results show that the correction factor may be assumed to be the product of a shield factor and a scatter factor the magnitudes of which depend on the chamber geometry and the radiation field. The change of the perturbation correction factor with phantom depth is important for the measurement of depth dose curves. This is demonstrated by an example. PMID:7360793

  3. Enhanced Magnetic Field Perturbations and Electric Currents Observed Downstream of the High Power Helicon

    NASA Astrophysics Data System (ADS)

    Race Roberson, B.; Winglee, Robert; Ziemba, Tim; Prager, James

    2010-11-01

    The high power helicon (HPH) is a compact plasma source that can generate downstream densities of 10^17-10^18 m-3 and directed ion energies greater than 20 eV that continue to increase tens of centimeters downstream of the source. In order to understand the coupling mechanism between the helicon antenna and the plasma outside the immediate source region, measurements were made in the plasma plume downstream from the thruster of the propagating wave magnetic field and the perturbation of the axial bulk field. This magnetic field perturbation (δB) peaks at more than 15 gauss in strength downstream of the plasma source and propagates tens of centimeters downstream, cancelling the base magnetic field as it propagates. Taking the curl of this measured magnetic perturbation and assuming azimuthal symmetry suggests a peak current density of 20 kA m-2. Data will be presented that relates the cancellation of the base magnetic field to the propagation of the helicon wave and the region where the plasma current system closes.

  4. Correlation between magnetic and electric field perturbations in the field-aligned current regions deduced from DE 2 observations

    NASA Technical Reports Server (NTRS)

    Ishii, M.; Sugiura, M.; Iyemori, T.; Slavin, J. A.

    1992-01-01

    The satellite-observed high correlations between magnetic and electric field perturbations in the high-latitude field-aligned current regions are investigated by examining the dependence of the relationship between Delta-B and E on spatial scale, using the electric and magnetic field data obtained by DE 2 in the polar regions. The results are compared with the Pedersen conductivity inferred from the international reference ionosphere model and the Alfven wave velocity calculated from the in situ ion density and magnetic field measurements.

  5. A test of magnetic field draping induced Bz perturbations ahead of fast coronal mass ejecta

    NASA Technical Reports Server (NTRS)

    Mccomas, D. J.; Gosling, J. T.; Bame, S. J.; Smith, E. J.; Cane, H. V.

    1989-01-01

    ICE plasma and magnetic field data are examined to look for observational evidence of IMF draping ahead of fast coronal mass ejections (CMEs). The utility of the draping model for predicting the Bz perturbations and hence geomagnetic activity associated with the sheath regions ahead of such CMEs is also examined. A simple prediction scheme based on the upstream radial field component is developed and a set of interplanetary shock events previously associated with interplanetary type II bursts, and hence solar source locations, is used. Of 17 events the radial component predictor developed here correctly predicts the direction considered of the Bz perturbations for 13 events (76 percent). While this result is certainly not conclusive, it is considered to be supportive of the draping scenario.

  6. Electric field-perturbation measurement of the interaction between two laser-induced plasmas

    NASA Astrophysics Data System (ADS)

    Sánchez-Aké, C.; Bredice, F.; Villagrán-Muniz, M.

    2012-02-01

    The interaction between two ns-laser-induced plasmas in air at the early-stage of expansion has been analyzed by using a method based on the direct measurement of the perturbation of an externally applied electric field. In this experimental method, the plasmas were produced by focusing two laser beams between the plates of a parallel-plane-charged capacitor. These plasmas produce a perturbation in the electric field of the capacitor which can be measured as a voltage change across a resistor connected to the ground plate. It was found that for delays shorter than 5 ns, the interaction between plasmas is mainly due to the interaction of the dipole-charge distribution of each plasma. For longer time delays, the shielding effect was dominant.

  7. Electric field-perturbation measurement of the interaction between two laser-induced plasmas

    SciTech Connect

    Sanchez-Ake, C.; Villagran-Muniz, M.; Bredice, F.

    2012-02-15

    The interaction between two ns-laser-induced plasmas in air at the early-stage of expansion has been analyzed by using a method based on the direct measurement of the perturbation of an externally applied electric field. In this experimental method, the plasmas were produced by focusing two laser beams between the plates of a parallel-plane-charged capacitor. These plasmas produce a perturbation in the electric field of the capacitor which can be measured as a voltage change across a resistor connected to the ground plate. It was found that for delays shorter than 5 ns, the interaction between plasmas is mainly due to the interaction of the dipole-charge distribution of each plasma. For longer time delays, the shielding effect was dominant.

  8. Electric field-perturbation measurement of the interaction between two laser-induced plasmas.

    PubMed

    Sánchez-Aké, C; Bredice, F; Villagrán-Muniz, M

    2012-02-01

    The interaction between two ns-laser-induced plasmas in air at the early-stage of expansion has been analyzed by using a method based on the direct measurement of the perturbation of an externally applied electric field. In this experimental method, the plasmas were produced by focusing two laser beams between the plates of a parallel-plane-charged capacitor. These plasmas produce a perturbation in the electric field of the capacitor which can be measured as a voltage change across a resistor connected to the ground plate. It was found that for delays shorter than 5 ns, the interaction between plasmas is mainly due to the interaction of the dipole-charge distribution of each plasma. For longer time delays, the shielding effect was dominant. PMID:22380088

  9. Saturn's periodic magnetic field perturbations caused by a rotating partial ring current

    NASA Astrophysics Data System (ADS)

    Brandt, P. C.; Khurana, K. K.; Mitchell, D. G.; Sergis, N.; Dialynas, K.; Carbary, J. F.; Roelof, E. C.; Paranicas, C. P.; Krimigis, S. M.; Mauk, B. H.

    2010-11-01

    We demonstrate that the periodic magnetic field perturbations as observed from Cassini are caused by the plasma pressure of the energetic (>2 keV) particle distributions that are periodically injected and subsequently drift around Saturn. Plasma pressures inferred from the Cassini Plasma Spectrometer (CAPS) (<2 keV) and the Magnetospheric Imaging Instrument (MIMI) (>2 keV) are used to compute the three-dimensional pressure-driven currents and their associated magnetic field perturbations. The distribution of the “hot” (>2 keV) plasma pressure is derived from Energetic Neutral Atom (ENA) images obtained by the Ion Neutral Camera (INCA) and in-situ spectral measurements. The radial profile of “cold” (<2 keV) plasma pressure is obtained from statistical studies and is assumed to be azimuthally symmetric.

  10. On twistors and conformal field theories from six dimensions

    SciTech Connect

    Saemann, Christian; Wolf, Martin

    2013-01-15

    We discuss chiral zero-rest-mass field equations on six-dimensional space-time from a twistorial point of view. Specifically, we present a detailed cohomological analysis, develop both Penrose and Penrose-Ward transforms, and analyse the corresponding contour integral formulae. We also give twistor space action principles. We then dimensionally reduce the twistor space of six-dimensional space-time to obtain twistor formulations of various theories in lower dimensions. Besides well-known twistor spaces, we also find a novel twistor space amongst these reductions, which turns out to be suitable for a twistorial description of self-dual strings. For these reduced twistor spaces, we explain the Penrose and Penrose-Ward transforms as well as contour integral formulae.

  11. Optical visualization of electric and magnetic field perturbations in tokamak discharges by hydrogen pellet injection

    NASA Astrophysics Data System (ADS)

    Drawin, H.-W.; Dubois, M. A.

    1992-09-01

    Two-dimensional intensity distribution mappings of photographs of pellet ablation cloud trajectories in TFR and TORE SUPRA reveal irregular shapes of the luminous striations. The observed features are not well understood, but a likely interpretation is that these features are caused by pre-existing electric and/or magnetic field perturbations in the hot core of tokamak plasmas. It is suggested to further investigate pellet injection as a diagnostic tool for the study of plasma structures and transport phenomena

  12. Neutron stars in a perturbative f(R) gravity model with strong magnetic fields

    SciTech Connect

    Cheoun, Myung-Ki; Deliduman, Cemsinan; Güngör, Can; Keleş, Vildan; Ryu, C.Y.; Kajino, Toshitaka; Mathews, Grant J. E-mail: cemsinan@msgsu.edu.tr E-mail: kelesvi@itu.edu.tr E-mail: kajino@nao.ac.jp

    2013-10-01

    In Kaluza-Klein electromagnetism it is natural to associate modified gravity with strong electromagnetic fields. Hence, in this paper we investigate the combined effects of a strong magnetic field and perturbative f(R) gravity on the structure of neutron stars. The effect of an interior strong magnetic field of about 10{sup 17−18} G on the equation of state is derived in the context of a quantum hadrodynamics (QHD) equation of state (EoS) including effects of the magnetic pressure and energy along with occupied Landau levels. Adopting a random orientation of interior field domains, we solve the modified spherically symmetric hydrostatic equilibrium equations derived for a gravity model with f(R) = R+αR{sup 2}. Effects of both the finite magnetic field and the modified gravity are detailed for various values of the magnetic field and the perturbation parameter α along with a discussion of their physical implications. We show that there exists a parameter space of the modified gravity and the magnetic field strength, in which even a soft equation of state can accommodate a large ( > 2 M{sub s}un) maximum neutron star mass.

  13. First-Principle Perturbative Computation of Phonon Properties of Insulators in Finite Electric Fields

    NASA Astrophysics Data System (ADS)

    Wang, Xinjie

    2005-03-01

    The methods of density-functional perturbation theory have been shown to provide a powerful tool for realistic calculations of lattice-vibrational, dielectric, elastic, and other response properties of crystals.ootnotetextS. Baroni et al., Rev. Mod. Phys. 73, 515 (2001). Recently, a total-energy method for insulators in nonzero electric fields was proposed.ootnotetextI. Souza, J. 'Iñiguez, and D. Vanderbilt, Phys. Rev. Lett. 89, 117602 (2002). However, the perturbative computation of phonon properties under a dc bias field has not previously been addressed. Here, we start from a variational total-energy functional with a field coupling term that represents the effect of the electric field on the crystal. The linear response of the field-polarized Bloch functions is obtained by minimizing the second-order derivative of the total-energy functional. Due to the presence of the electric field, the field-polarized Bloch functions at each k-point in the Brillouin zone are weakly coupled to those at the neighboring k-points. We implement the method in the ABINIT code and perform illustrative calculations of the phonon frequencies for III-V semicondutors.

  14. Accurate Structure Prediction and Conformational Analysis of Cyclic Peptides with Residue-Specific Force Fields.

    PubMed

    Geng, Hao; Jiang, Fan; Wu, Yun-Dong

    2016-05-19

    Cyclic peptides (CPs) are promising candidates for drugs, chemical biology tools, and self-assembling nanomaterials. However, the development of reliable and accurate computational methods for their structure prediction has been challenging. Here, 20 all-trans CPs of 5-12 residues selected from Cambridge Structure Database have been simulated using replica-exchange molecular dynamics with four different force fields. Our recently developed residue-specific force fields RSFF1 and RSFF2 can correctly identify the crystal-like conformations of more than half CPs as the most populated conformation. The RSFF2 performs the best, which consistently predicts the crystal structures of 17 out of 20 CPs with rmsd < 1.1 Å. We also compared the backbone (ϕ, ψ) sampling of residues in CPs with those in short linear peptides and in globular proteins. In general, unlike linear peptides, CPs have local conformational free energies and entropies quite similar to globular proteins. PMID:27128113

  15. Relative entropy of excited states in two dimensional conformal field theories

    NASA Astrophysics Data System (ADS)

    Sárosi, Gábor; Ugajin, Tomonori

    2016-07-01

    We study the relative entropy and the trace square distance, both of which measure the distance between reduced density matrices of two excited states in two dimensional conformal field theories. We find a general formula for the relative entropy between two primary states with the same conformal dimension in the limit of a single small interval and find that in this case the relative entropy is proportional to the trace square distance. We check our general formulae by calculating the relative entropy between two generalized free fields and the trace square distance between the spin and disorder operators of the critical Ising model. We also give the leading term of the relative entropy in the small interval expansion when the two operators have different conformal dimensions. This turns out to be universal when the CFT has no primaires lighter than the stress tensor. The result reproduces the previously known special cases.

  16. Control of nonlinear systems using periodic parametric perturbations with application to a reversed field pinch

    SciTech Connect

    Mirus, K.A.

    1998-06-01

    In this thesis, the possibility of controlling low- and high-dimensional chaotic systems by periodically driving an accessible system parameter is examined. This method has been carried out on several numerical systems and the MST Reversed Field Pinch. The numerical systems investigated include the logistic equation, the Lorenz equations, the Roessler equations, a coupled lattice of logistic equations, a coupled lattice of Lorenz equations, the Yoshida equations, which model tearing mode fluctuations in a plasma, and a neural net model for magnetic fluctuations on MST. This method was tested on the MST by sinusoidally driving a magnetic flux through the toroidal gap of the device. Numerically, periodic drives were found to be most effective at producing limit cycle behavior or significantly reducing the dimension of the system when the perturbation frequency was near natural frequencies of unstable periodic orbits embedded in the attractor of the unperturbed system. Several different unstable periodic orbits have been stabilized in this way for the low-dimensional numerical systems, sometimes with perturbation amplitudes that were less than 5% of the nominal value of the parameter being perturbed. In high-dimensional systems, limit cycle behavior and significant decreases in the system dimension were also achieved using perturbations with frequencies near the natural unstable periodic orbit frequencies. Results for the MST were not this encouraging, most likely because of an insufficient drive amplitude, the extremely high dimension of the plasma behavior, large amounts of noise, and a lack of stationarity in the transient plasma pulses.

  17. Control of nonlinear systems using periodic parametric perturbations with application to a reversed field pinch

    NASA Astrophysics Data System (ADS)

    Mirus, Kevin Andrew

    In this thesis, the possibility of controlling low- and high-dimensional chaotic systems by periodically driving an accessible system parameter is examined. This method has been carried out on several numerical systems and the MST Reversed Field Pinch. The numerical systems investigated include the logistic equation, the Lorenz equations, the Rossler equations, a coupled lattice of logistic equations, a coupled lattice of Lorenz equations, the Yoshida equations, which model tearing mode fluctuations in a plasma, and a neural net model for magnetic fluctuations on MST. This method was tested on the MST by sinusoidally driving a magnetic flux through the toroidal gap of the device. Numerically, periodic drives were found to be most effective at producing limit cycle behavior or significantly reducing the dimension of the system when the perturbation frequency was near natural frequencies of unstable periodic orbits embedded in the attractor of the unperturbed system. Several different unstable periodic orbits have been stabilized in this way for the low-dimensional numerical systems, sometimes with perturbation amplitudes that were less than 5% of the nominal value of the parameter being perturbed. In high- dimensional systems, limit cycle behavior and significant decreases in the system dimension were also achieved using perturbations with frequencies near the natural unstable periodic orbit frequencies. Results for the MST were not this encouraging, most likely because of an insufficient drive amplitude, the extremely high dimension of the plasma behavior, large amounts of noise, and a lack of stationarity in the transient plasma pulses.

  18. Impact of Resonant Magnetic Perturbation Fields on NSTX-U Advanced Divertor Topologies

    NASA Astrophysics Data System (ADS)

    Waters, Ian; Frerichs, Heinke; Schmitz, Oliver; Ahn, Joon-Wook; Canal, Gustavo; Evans, Todd; Soukhanovskii, Vlad

    2015-11-01

    Explorations are under way to optimize the magnetic topology in the plasma edge of NSTX-U with the goal of improving neutral and impurity fueling and exhaust. The use of magnetic perturbation fields is being considered to spread heat and particle fluxes in the divertor, adjust plasma refueling, control impurity transport, and improve coupling to the exhaust systems. Also, advanced divertor configurations are being considered to improve peak heat loads on divertors. An assessment is made of the topologies of a number of representative NSTX-U advanced divertor configurations: lower single null, exact snowflake, and snowflake minus. Wall to wall magnetic connection lengths for each configuration are assessed in both their perturbed and axisymmetric configurations with perturbation coil currents of 1kA and 3kA. The magnetic perturbations yield complex strike patterns on divertor elements that are expected to be resolvable experimentally. The EMC3-EIRENE fluid plasma and kinetic neutral transport code will be used to study neutral and impurity transport and exhaust in these topologies. This work was funded in part by the Department of Energy under grant DE-SC0012315 and by startup funds of the Department of Engineering Physics at the University of Wisconsin-Madison.

  19. Neutron star structure in the presence of conformally coupled scalar fields

    NASA Astrophysics Data System (ADS)

    Sultana, Joseph; Bose, Benjamin; Kazanas, Demosthenes

    2014-10-01

    Neutron star models are studied in the context of scalar-tensor theories of gravity in the presence of a conformally coupled scalar field, using two different numerical equations of state (EoS) representing different degrees of stiffness. In both cases we obtain a complete solution by matching the interior numerical solution of the coupled Einstein-scalar field hydrostatic equations, with an exact metric on the surface of the star. These are then used to find the effect of the scalar field and its coupling to geometry, on the neutron star structure, particularly the maximum neutron star mass and radius. We show that in the presence of a conformally coupled scalar field, neutron stars are less dense and have smaller masses and radii than their counterparts in the minimally coupled case, and the effect increases with the magnitude of the scalar field at the center of the star.

  20. Neutron Star Structure in the Presence of Conformally Coupled Scalar Fields

    NASA Technical Reports Server (NTRS)

    Sultana, Joseph; Bose, Benjamin; Kazanas, Demosthenes

    2014-01-01

    Neutron star models are studied in the context of scalar-tensor theories of gravity in the presence of a conformally coupled scalar field, using two different numerical equations of state (EoS) representing different degrees of stiffness. In both cases we obtain a complete solution by matching the interior numerical solution of the coupled Einstein-scalar field hydrostatic equations, with an exact metric on the surface of the star. These are then used to find the effect of the scalar field and its coupling to geometry, on the neutron star structure, particularly the maximum neutron star mass and radius. We show that in the presence of a conformally coupled scalar field, neutron stars are less dense and have smaller masses and radii than their counterparts in the minimally coupled case, and the effect increases with the magnitude of the scalar field at the center of the star.

  1. Riemann correlator in de Sitter including loop corrections from conformal fields

    NASA Astrophysics Data System (ADS)

    Fröb, Markus B.; Roura, Albert; Verdaguer, Enric

    2014-07-01

    The Riemann correlator with appropriately raised indices characterizes in a gauge-invariant way the quantum metric fluctuations around de Sitter spacetime including loop corrections from matter fields. Specializing to conformal fields and employing a method that selects the de Sitter-invariant vacuum in the Poincaré patch, we obtain the exact result for the Riemann correlator through order H4/mp4. The result is expressed in a manifestly de Sitter-invariant form in terms of maximally symmetric bitensors. Its behavior for both short and long distances (sub- and superhorizon scales) is analyzed in detail. Furthermore, by carefully taking the flat-space limit, the explicit result for the Riemann correlator for metric fluctuations around Minkowki spacetime is also obtained. Although the main focus is on free scalar fields (our calculation corresponds then to one-loop order in the matter fields), the result for general conformal field theories is also derived.

  2. Riemann correlator in de Sitter including loop corrections from conformal fields

    SciTech Connect

    Fröb, Markus B.; Verdaguer, Enric

    2014-07-01

    The Riemann correlator with appropriately raised indices characterizes in a gauge-invariant way the quantum metric fluctuations around de Sitter spacetime including loop corrections from matter fields. Specializing to conformal fields and employing a method that selects the de Sitter-invariant vacuum in the Poincaré patch, we obtain the exact result for the Riemann correlator through order H{sup 4}/m{sub p}{sup 4}. The result is expressed in a manifestly de Sitter-invariant form in terms of maximally symmetric bitensors. Its behavior for both short and long distances (sub- and superhorizon scales) is analyzed in detail. Furthermore, by carefully taking the flat-space limit, the explicit result for the Riemann correlator for metric fluctuations around Minkowki spacetime is also obtained. Although the main focus is on free scalar fields (our calculation corresponds then to one-loop order in the matter fields), the result for general conformal field theories is also derived.

  3. Ideal plasma response to vacuum magnetic fields with resonant magnetic perturbations in non-axisymmetric tokamaks

    NASA Astrophysics Data System (ADS)

    Kim, Kimin; Ahn, J.-W.; Scotti, F.; Park, J.-K.; Menard, J. E.

    2015-10-01

    Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n   =   3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifies the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n   =   3. Amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n   =   1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.

  4. Ideal plasma response to vacuum magnetic fields with resonant magnetic perturbations in non-axisymmetric tokamaks

    DOE PAGESBeta

    Kim, Kimin; Ahn, J. -W.; Scotti, F.; Park, J. -K.; Menard, J. E.

    2015-09-03

    Ideal plasma shielding and amplification of resonant magnetic perturbations in non-axisymmetric tokamak is presented by field line tracing simulation with full ideal plasma response, compared to measurements of divertor lobe structures. Magnetic field line tracing simulations in NSTX with toroidal non-axisymmetry indicate the ideal plasma response can significantly shield/amplify and phase shift the vacuum resonant magnetic perturbations. Ideal plasma shielding for n = 3 mode is found to prevent magnetic islands from opening as consistently shown in the field line connection length profile and magnetic footprints on the divertor target. It is also found that the ideal plasma shielding modifiesmore » the degree of stochasticity but does not change the overall helical lobe structures of the vacuum field for n = 3. Furthermore, amplification of vacuum fields by the ideal plasma response is predicted for low toroidal mode n = 1, better reproducing measurements of strong striation of the field lines on the divertor plate in NSTX.« less

  5. Next-Generation Force Fields from Symmetry-Adapted Perturbation Theory

    NASA Astrophysics Data System (ADS)

    McDaniel, Jesse G.; Schmidt, J. R.

    2016-05-01

    Symmetry-adapted perturbation theory (SAPT) provides a unique set of advantages for parameterizing next-generation force fields from first principles. SAPT provides a direct, basis-set superposition error free estimate of molecular interaction energies, a physically intuitive energy decomposition, and a seamless transition to an asymptotic picture of intermolecular interactions. These properties have been exploited throughout the literature to develop next-generation force fields for a variety of applications, including classical molecular dynamics simulations, crystal structure prediction, and quantum dynamics/spectroscopy. This review provides a brief overview of the formalism and theory of SAPT, along with a practical discussion of the various methodologies utilized to parameterize force fields from SAPT calculations. It also highlights a number of applications of SAPT-based force fields for chemical systems of particular interest. Finally, the review ends with a brief outlook on the future opportunities and challenges that remain for next-generation force fields based on SAPT.

  6. Next-Generation Force Fields from Symmetry-Adapted Perturbation Theory.

    PubMed

    McDaniel, Jesse G; Schmidt, J R

    2016-05-27

    Symmetry-adapted perturbation theory (SAPT) provides a unique set of advantages for parameterizing next-generation force fields from first principles. SAPT provides a direct, basis-set superposition error free estimate of molecular interaction energies, a physically intuitive energy decomposition, and a seamless transition to an asymptotic picture of intermolecular interactions. These properties have been exploited throughout the literature to develop next-generation force fields for a variety of applications, including classical molecular dynamics simulations, crystal structure prediction, and quantum dynamics/spectroscopy. This review provides a brief overview of the formalism and theory of SAPT, along with a practical discussion of the various methodologies utilized to parameterize force fields from SAPT calculations. It also highlights a number of applications of SAPT-based force fields for chemical systems of particular interest. Finally, the review ends with a brief outlook on the future opportunities and challenges that remain for next-generation force fields based on SAPT. PMID:27070322

  7. Gravitational perturbation and Kerr/CFT correspondence

    NASA Astrophysics Data System (ADS)

    Ghezelbash, A. M.

    2016-07-01

    We find the explicit form of two-point function for the conformal spin-2 energy momentum operators on the near horizon of a near extremal Kerr black hole by variation of a proper boundary action. In this regard, we consider an appropriate boundary action for the gravitational perturbation of the Kerr black hole. We show that the variation of the boundary action with respect to the boundary fields yields the two-point function for the energy momentum tensor of a conformal field theory. We find agreement between the two-point function and the correlators of the dual conformal field theory to the Kerr black hole.

  8. Screening of external magnetic perturbation fields due to sheared plasma flow

    NASA Astrophysics Data System (ADS)

    Li, L.; Liu, Y. Q.; Liang, Y.; Wang, N.; Luan, Q.; Zhong, F. C.; Liu, Y.

    2016-09-01

    Within the single fluid resistive magnetohydrodynamic model, systematic toroidal modelling efforts are devoted to investigate the plasma response induced screening of the applied external 3D magnetic field perturbations in the presence of sheared toroidal flow. One particular issue of interest is addressed, when the local flow speed approaches zero at the perturbation rational surface inside the plasma. Subtle screening physics, associated with the favourable averaged toroidal curvature effect (the GGJ effect (Glasser et al 1975 Phys. Fluids 7 875)), is found to play an essential role during slow flow near the rational surface by enhancing the screening at reduced flow. A strong cancellation effect between different terms of Ohm’s law is discovered, leading to different screening physics in the GGJ regime, as compared to that of conventional screening of the typical resistive-inertial regime occurring at faster flow. These modelling results may be applicable to interpret certain mode locking experiments, as well as type-I edge localized mode suppression experiments, with resonant magnetic field perturbations being applied to tokamak plasmas at low input toroidal torque.

  9. On the reach of perturbative descriptions for dark matter displacement fields

    NASA Astrophysics Data System (ADS)

    Baldauf, Tobias; Schaan, Emmanuel; Zaldarriaga, Matias

    2016-03-01

    We study Lagrangian Perturbation Theory (LPT) and its regularization in the Effective Field Theory (EFT) approach. We evaluate the LPT displacement with the same phases as a corresponding N-body simulation, which allows us to compare perturbation theory to the non-linear simulation with significantly reduced cosmic variance, and provides a more stringent test than simply comparing power spectra. We reliably detect a non-vanishing leading order EFT coefficient and a stochastic displacement term, uncorrelated with the LPT terms. This stochastic term is expected in the EFT framework, and, to the best of our understanding, is not an artifact of numerical errors or transients in our simulations. This term constitutes a limit to the accuracy of perturbative descriptions of the displacement field and its phases, corresponding to a 1% error on the non-linear power spectrum at k = 0.2 h-1Mpc at z = 0. Predicting the displacement power spectrum to higher accuracy or larger wavenumbers thus requires a model for the stochastic displacement.

  10. Field-Aligned and Ionospheric Current Contributions to Ground Magnetic Perturbations

    NASA Astrophysics Data System (ADS)

    Connors, M. G.; McPherron, R. L.; Anderson, B. J.; Korth, H.; Russell, C. T.; Chu, X.

    2014-12-01

    AMPERE data provides global space-derived radial electric currents on temporal and spatial scales suited to studying magnetic fields at ULF frequencies. It responds little to ionspheric currents, which dominate ground-based measurements, so that AMPERE and ground datasets complement each other to give a comprehensive view of near-Earth electric currents. Connors et al. (GRL, 2014) found that a three-dimensional current system slightly modified from the original substorm current wedge (SCW) concept of McPherron et al. (JGR, 1973) represented substorm midnight sector perturbations well both in the auroral and subauroral regions, if a current equivalent to that found by integrating AMPERE downward current was used, located where clear SCW signatures were indicated by AMPERE, and featuring an ionospheric electrojet. The AMPERE upward current was found to exceed that in the SCW, at least in part since the evening sector electrojet fed into it. We extend these results with a more detailed accounting of field-aligned and ionospheric currents throughout the active period (including growth phase). Ionospheric currents for the study are obtained from ground perturbations through optimization of a simple forward model over regions or on a meridian chain. We also investigate the degree to which subauroral perturbations may be directly calculated from AMPERE results. We further find that auroral zone currents may be very localized, to the extent that the entire SCW ionospheric current flows in a very restricted latitudinal range near onset, possibly corresponding to a single auroral arc.

  11. Statistical maps of geomagnetic perturbations as a function of the interplanetary magnetic field

    NASA Astrophysics Data System (ADS)

    Weimer, D. R.; Clauer, C. R.; Engebretson, M. J.; Hansen, T. L.; Gleisner, H.; Mann, I.; Yumoto, K.

    2010-10-01

    Mappings of geomagnetic perturbations are shown for different combinations of the solar wind velocity, interplanetary magnetic field (IMF), and dipole tilt angle (season). Average maps were derived separately for the northward, eastward, and vertical (downward) components of the geomagnetic disturbances, using spherical cap harmonics in least error fits of sorted measurements. The source data are obtained from 104 ground-based magnetometer stations in the Northern Hemisphere at geomagnetic latitudes over 40° during the years 1998 through 2001. Contour maps of statistical fits are shown along-side scatter plots of individual measurements in corrected geomagnetic apex coordinates. The patterns are consistent with previous mappings of ionospheric electric potential. Interestingly, the vertical component of the magnetic perturbations closely resembles maps of the overhead, field-aligned currents, including the Northward IMF configuration. The maximum and minimum values from the statistical mappings are graphed to show their changes as a function of southward IMF magnitude, solar wind velocity, and seasons. It is expected that this work will lead to better advance predictions of the geomagnetic perturbations that are based on real-time IMF measurements.

  12. On discrete field theory properties of the dimer and Ising models and their conformal field theory limits

    SciTech Connect

    Kriz, Igor; Loebl, Martin; Somberg, Petr

    2013-05-15

    We study various mathematical aspects of discrete models on graphs, specifically the Dimer and the Ising models. We focus on proving gluing formulas for individual summands of the partition function. We also obtain partial results regarding conjectured limits realized by fermions in rational conformal field theories.

  13. Diagnosing Chaos Using Four-Point Functions in Two-Dimensional Conformal Field Theory

    NASA Astrophysics Data System (ADS)

    Roberts, Daniel A.; Stanford, Douglas

    2015-09-01

    We study chaotic dynamics in two-dimensional conformal field theory through out-of-time-order thermal correlators of the form ⟨W (t )V W (t )V ⟩ . We reproduce holographic calculations similar to those of Shenker and Stanford, by studying the large c Virasoro identity conformal block. The contribution of this block to the above correlation function begins to decrease exponentially after a delay of ˜t*-(β /2 π )log β2EwEv , where t* is the fast scrambling time (β /2 π )log c and Ew,Ev are the energy scales of the W ,V operators.

  14. Diagnosing Chaos Using Four-Point Functions in Two-Dimensional Conformal Field Theory.

    PubMed

    Roberts, Daniel A; Stanford, Douglas

    2015-09-25

    We study chaotic dynamics in two-dimensional conformal field theory through out-of-time-order thermal correlators of the form ⟨W(t)VW(t)V⟩. We reproduce holographic calculations similar to those of Shenker and Stanford, by studying the large c Virasoro identity conformal block. The contribution of this block to the above correlation function begins to decrease exponentially after a delay of ~t_{*}-(β/2π)logβ^{2}E_{w}E_{v}, where t_{*} is the fast scrambling time (β/2π)logc and E_{w},E_{v} are the energy scales of the W,V operators. PMID:26451543

  15. A statistical approach to multifield inflation: many-field perturbations beyond slow roll

    NASA Astrophysics Data System (ADS)

    McAllister, Liam; Renaux-Petel, Sébastien; Xu, Gang

    2012-10-01

    We study multifield contributions to the scalar power spectrum in an ensemble of six-field inflationary models obtained in string theory. We identify examples in which inflation occurs by chance, near an approximate inflection point, and we compute the primordial perturbations numerically, both exactly and using an array of truncated models. The scalar mass spectrum and the number of fluctuating fields are accurately described by a simple random matrix model. During the approach to the inflection point, bending trajectories and violations of slow roll are commonplace, and `many-field' effects, in which three or more fields influence the perturbations, are often important. However, in a large fraction of models consistent with constraints on the tilt the signatures of multifield evolution occur on unobservably large scales. Our scenario is a concrete microphysical realization of quasi-single-field inflation, with scalar masses of order H, but the cubic and quartic couplings are typically too small to produce detectable non-Gaussianity. We argue that our results are characteristic of a broader class of models arising from multifield potentials that are natural in the Wilsonian sense.

  16. A statistical approach to multifield inflation: many-field perturbations beyond slow roll

    SciTech Connect

    McAllister, Liam; Xu, Gang; Renaux-Petel, Sébastien E-mail: S.Renauxpetel@damtp.cam.ac.uk

    2012-10-01

    We study multifield contributions to the scalar power spectrum in an ensemble of six-field inflationary models obtained in string theory. We identify examples in which inflation occurs by chance, near an approximate inflection point, and we compute the primordial perturbations numerically, both exactly and using an array of truncated models. The scalar mass spectrum and the number of fluctuating fields are accurately described by a simple random matrix model. During the approach to the inflection point, bending trajectories and violations of slow roll are commonplace, and 'many-field' effects, in which three or more fields influence the perturbations, are often important. However, in a large fraction of models consistent with constraints on the tilt the signatures of multifield evolution occur on unobservably large scales. Our scenario is a concrete microphysical realization of quasi-single-field inflation, with scalar masses of order H, but the cubic and quartic couplings are typically too small to produce detectable non-Gaussianity. We argue that our results are characteristic of a broader class of models arising from multifield potentials that are natural in the Wilsonian sense.

  17. Second-Order Perturbation Theory for Generalized Active Space Self-Consistent-Field Wave Functions.

    PubMed

    Ma, Dongxia; Li Manni, Giovanni; Olsen, Jeppe; Gagliardi, Laura

    2016-07-12

    A multireference second-order perturbation theory approach based on the generalized active space self-consistent-field (GASSCF) wave function is presented. Compared with the complete active space (CAS) and restricted active space (RAS) wave functions, GAS wave functions are more flexible and can employ larger active spaces and/or different truncations of the configuration interaction expansion. With GASSCF, one can explore chemical systems that are not affordable with either CASSCF or RASSCF. Perturbation theory to second order on top of GAS wave functions (GASPT2) has been implemented to recover the remaining electron correlation. The method has been benchmarked by computing the chromium dimer ground-state potential energy curve. These calculations show that GASPT2 gives results similar to CASPT2 even with a configuration interaction expansion much smaller than the corresponding CAS expansion. PMID:27276688

  18. Horizon-preserving dualities and perturbations in non-canonical scalar field cosmologies

    SciTech Connect

    Geshnizjani, Ghazal; Kinney, William H.; Dizgah, Azadeh Moradinezhad E-mail: whkinney@buffalo.edu

    2012-02-01

    We generalize the cosmological duality between inflation and cyclic contraction under the interchange a↔H to the case of non-canonical scalar field theories with varying speed of sound. The single duality in the canonical case generalizes to a family of three dualities constructed to leave the cosmological acoustic horizon invariant. We find three classes of models: (I) DBI inflation, (II) the non-canonical generalization of cyclic contraction, and (III) a new cosmological solution with rapidly decreasing speed of sound and relatively slowly growing scale factor, which we dub stalled cosmology. We construct dual analogs to the inflationary slow roll approximation, and solve for the curvature perturbation in all three cases. Both cyclic contraction and stalled cosmology predict a strongly blue spectrum for the curvature perturbations inconsistent with observations.

  19. Perturbative Calculation of Quasi-Potential in Non-equilibrium Diffusions: A Mean-Field Example

    NASA Astrophysics Data System (ADS)

    Bouchet, Freddy; Gawȩdzki, Krzysztof; Nardini, Cesare

    2016-06-01

    In stochastic systems with weak noise, the logarithm of the stationary distribution becomes proportional to a large deviation rate function called the quasi-potential. The quasi-potential, and its characterization through a variational problem, lies at the core of the Freidlin-Wentzell large deviations theory (Freidlin and Wentzell, Random perturbations of dynamical systems, 2012). In many interacting particle systems, the particle density is described by fluctuating hydrodynamics governed by Macroscopic Fluctuation Theory (Bertini et al., arXiv:1404.6466 , 2014), which formally fits within Freidlin-Wentzell's framework with a weak noise proportional to 1/√{N}, where N is the number of particles. The quasi-potential then appears as a natural generalization of the equilibrium free energy to non-equilibrium particle systems. A key physical and practical issue is to actually compute quasi-potentials from their variational characterization for non-equilibrium systems for which detailed balance does not hold. We discuss how to perform such a computation perturbatively in an external parameter λ , starting from a known quasi-potential for λ =0. In a general setup, explicit iterative formulae for all terms of the power-series expansion of the quasi-potential are given for the first time. The key point is a proof of solvability conditions that assure the existence of the perturbation expansion to all orders. We apply the perturbative approach to diffusive particles interacting through a mean-field potential. For such systems, the variational characterization of the quasi-potential was proven by Dawson and Gartner (Stochastics 20:247-308, 1987; Stochastic differential systems, vol 96, pp 1-10, 1987). Our perturbative analysis provides new explicit results about the quasi-potential and about fluctuations of one-particle observables in a simple example

  20. Perturbative Calculation of Quasi-Potential in Non-equilibrium Diffusions: A Mean-Field Example

    NASA Astrophysics Data System (ADS)

    Bouchet, Freddy; Gawȩdzki, Krzysztof; Nardini, Cesare

    2016-04-01

    In stochastic systems with weak noise, the logarithm of the stationary distribution becomes proportional to a large deviation rate function called the quasi-potential. The quasi-potential, and its characterization through a variational problem, lies at the core of the Freidlin-Wentzell large deviations theory (Freidlin and Wentzell, Random perturbations of dynamical systems, 2012). In many interacting particle systems, the particle density is described by fluctuating hydrodynamics governed by Macroscopic Fluctuation Theory (Bertini et al., arXiv:1404.6466, 2014), which formally fits within Freidlin-Wentzell's framework with a weak noise proportional to 1/√{N} , where N is the number of particles. The quasi-potential then appears as a natural generalization of the equilibrium free energy to non-equilibrium particle systems. A key physical and practical issue is to actually compute quasi-potentials from their variational characterization for non-equilibrium systems for which detailed balance does not hold. We discuss how to perform such a computation perturbatively in an external parameter λ , starting from a known quasi-potential for λ =0 . In a general setup, explicit iterative formulae for all terms of the power-series expansion of the quasi-potential are given for the first time. The key point is a proof of solvability conditions that assure the existence of the perturbation expansion to all orders. We apply the perturbative approach to diffusive particles interacting through a mean-field potential. For such systems, the variational characterization of the quasi-potential was proven by Dawson and Gartner (Stochastics 20:247-308, 1987; Stochastic differential systems, vol 96, pp 1-10, 1987). Our perturbative analysis provides new explicit results about the quasi-potential and about fluctuations of one-particle observables in a simple example of mean field diffusions: the Shinomoto-Kuramoto model of coupled rotators (Prog Theoret Phys 75:1105-1110, [74]). This

  1. Binding analysis of carbon nanoparticles to human immunoglobulin G: Elucidation of the cytotoxicity of CNPs and perturbation of immunoglobulin conformations

    NASA Astrophysics Data System (ADS)

    Zhang, Shengrui; Yang, Haitao; Ji, Xiaohui; Wang, Qin

    2016-02-01

    The chemical compositions, sizes and fluorescent properties of synthesized carbon nanoparticles (CNPs) were characterized. Escherichia coli (E. coli) cells were used as a model to study the cytotoxicity of CNPs, and the results of the cellular uptake of CNPs yielded excellent results: the CNPs demonstrated good biocompatibility and were non-toxic to the growth of the E. coli cells. Moreover, to assess the potential toxicity of CNPs to human health, the binding behavior of CNPs with human immunoglobulin G (HIgG) was examined by fluorescence quenching spectroscopy, synchronous fluorescence spectroscopy and circular dichroism spectroscopy under physiological conditions. The fluorescence quenching constants and parameters for the interaction at different temperatures had been calculated according to Scatchard. The thermodynamic parameters, such as enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG), were calculated, and the results indicated strong static quenching and showed that van der Waals forces, hydrogen bonds and hydrophobic interactions were the predominant intermolecular forces stabilizing the CNP-HIgG complex. Synchronous fluorescence and circular dichroism spectra provided information regarding the conformational alteration of HIgG in the presence of CNPs. These findings help to characterize the interactions between CNPs and HIgG, which may clarify the potential risks and undesirable health effects of CNPs, as well as the related cellular trafficking and systemic translocation.

  2. Binding analysis of carbon nanoparticles to human immunoglobulin G: Elucidation of the cytotoxicity of CNPs and perturbation of immunoglobulin conformations.

    PubMed

    Zhang, Shengrui; Yang, Haitao; Ji, Xiaohui; Wang, Qin

    2016-02-01

    The chemical compositions, sizes and fluorescent properties of synthesized carbon nanoparticles (CNPs) were characterized. Escherichia coli (E. coli) cells were used as a model to study the cytotoxicity of CNPs, and the results of the cellular uptake of CNPs yielded excellent results: the CNPs demonstrated good biocompatibility and were non-toxic to the growth of the E. coli cells. Moreover, to assess the potential toxicity of CNPs to human health, the binding behavior of CNPs with human immunoglobulin G (HIgG) was examined by fluorescence quenching spectroscopy, synchronous fluorescence spectroscopy and circular dichroism spectroscopy under physiological conditions. The fluorescence quenching constants and parameters for the interaction at different temperatures had been calculated according to Scatchard. The thermodynamic parameters, such as enthalpy change (ΔH), entropy change (ΔS) and free energy change (ΔG), were calculated, and the results indicated strong static quenching and showed that van der Waals forces, hydrogen bonds and hydrophobic interactions were the predominant intermolecular forces stabilizing the CNP-HIgG complex. Synchronous fluorescence and circular dichroism spectra provided information regarding the conformational alteration of HIgG in the presence of CNPs. These findings help to characterize the interactions between CNPs and HIgG, which may clarify the potential risks and undesirable health effects of CNPs, as well as the related cellular trafficking and systemic translocation. PMID:26505286

  3. Computational ligand-based rational design: Role of conformational sampling and force fields in model development

    PubMed Central

    Shim, Jihyun; MacKerell, Alexander D.

    2011-01-01

    A significant number of drug discovery efforts are based on natural products or high throughput screens from which compounds showing potential therapeutic effects are identified without knowledge of the target molecule or its 3D structure. In such cases computational ligand-based drug design (LBDD) can accelerate the drug discovery processes. LBDD is a general approach to elucidate the relationship of a compound's structure and physicochemical attributes to its biological activity. The resulting structure-activity relationship (SAR) may then act as the basis for the prediction of compounds with improved biological attributes. LBDD methods range from pharmacophore models identifying essential features of ligands responsible for their activity, quantitative structure-activity relationships (QSAR) yielding quantitative estimates of activities based on physiochemical properties, and to similarity searching, which explores compounds with similar properties as well as various combinations of the above. A number of recent LBDD approaches involve the use of multiple conformations of the ligands being studied. One of the basic components to generate multiple conformations in LBDD is molecular mechanics (MM), which apply an empirical energy function to relate conformation to energies and forces. The collection of conformations for ligands is then combined with functional data using methods ranging from regression analysis to neural networks, from which the SAR is determined. Accordingly, for effective application of LBDD for SAR determinations it is important that the compounds be accurately modelled such that the appropriate range of conformations accessible to the ligands is identified. Such accurate modelling is largely based on use of the appropriate empirical force field for the molecules being investigated and the approaches used to generate the conformations. The present chapter includes a brief overview of currently used SAR methods in LBDD followed by a more

  4. Computational ligand-based rational design: Role of conformational sampling and force fields in model development.

    PubMed

    Shim, Jihyun; Mackerell, Alexander D

    2011-05-01

    A significant number of drug discovery efforts are based on natural products or high throughput screens from which compounds showing potential therapeutic effects are identified without knowledge of the target molecule or its 3D structure. In such cases computational ligand-based drug design (LBDD) can accelerate the drug discovery processes. LBDD is a general approach to elucidate the relationship of a compound's structure and physicochemical attributes to its biological activity. The resulting structure-activity relationship (SAR) may then act as the basis for the prediction of compounds with improved biological attributes. LBDD methods range from pharmacophore models identifying essential features of ligands responsible for their activity, quantitative structure-activity relationships (QSAR) yielding quantitative estimates of activities based on physiochemical properties, and to similarity searching, which explores compounds with similar properties as well as various combinations of the above. A number of recent LBDD approaches involve the use of multiple conformations of the ligands being studied. One of the basic components to generate multiple conformations in LBDD is molecular mechanics (MM), which apply an empirical energy function to relate conformation to energies and forces. The collection of conformations for ligands is then combined with functional data using methods ranging from regression analysis to neural networks, from which the SAR is determined. Accordingly, for effective application of LBDD for SAR determinations it is important that the compounds be accurately modelled such that the appropriate range of conformations accessible to the ligands is identified. Such accurate modelling is largely based on use of the appropriate empirical force field for the molecules being investigated and the approaches used to generate the conformations. The present chapter includes a brief overview of currently used SAR methods in LBDD followed by a more

  5. Scalar particle in general inertial and gravitational fields and conformal invariance revisited

    NASA Astrophysics Data System (ADS)

    Silenko, Alexander J.

    2013-08-01

    The new manifestation of conformal invariance for a massless scalar particle in a Riemannian spacetime of general relativity is found. Conformal transformations conserve the Hamiltonian and wave function in the Foldy-Wouthuysen representation. Similarity of manifestations of conformal invariance for massless scalar and Dirac particles is proved. New exact Foldy-Wouthuysen Hamiltonians are derived for both massive and massless scalar particles in a general static spacetime and in a frame rotating in the Kerr field approximated by a spatially isotropic metric. The latter case covers an observer on the ground of the Earth or on a satellite and takes into account the Lense-Thirring effect. High-precision formulas are obtained for an arbitrary spacetime metric. General quantum-mechanical equations of motion are derived. Their classical limit coincides with corresponding classical equations.

  6. Three-dimensional black holes with conformally coupled scalar and gauge fields

    NASA Astrophysics Data System (ADS)

    Cárdenas, Marcela; Fuentealba, Oscar; Martínez, Cristián

    2014-12-01

    We consider three-dimensional gravity with negative cosmological constant in the presence of a scalar and an Abelian gauge field. Both fields are conformally coupled to gravity, the scalar field through a nonminimal coupling with the curvature and the gauge field by means of a Lagrangian given by a power of the Maxwell one. A sixth-power self-interaction potential, which does not spoil conformal invariance is also included in the action. Using a circularly symmetric ansatz, we obtain black hole solutions dressed with the scalar and gauge fields, which are regular on and outside the event horizon. These charged hairy black holes are asymptotically anti-de Sitter spacetimes. The mass and the electric charge are computed by using the Regge-Teitelboim Hamiltonian approach. If both leading and subleading terms of the asymptotic condition of the scalar field are present, a boundary condition that functionally relates them is required for determining the mass. Since the asymptotic form of the scalar field solution is defined by two integration constants, the boundary condition may or may not respect the asymptotic conformal symmetry. An analysis of the temperature and entropy of these black holes is presented. The temperature is a monotonically increasing function of the horizon radius as expected for asymptotically anti-de Sitter black holes. However, restrictions on the parameters describing the black holes are found by requiring the entropy to be positive, which, given the nonminimal coupling considered here, does not follow the area law. Remarkably, the same conditions ensure that the conformally related solutions become black holes in the Einstein frame.

  7. From charge motion in general magnetic fields to the non perturbative gyrokinetic equation

    NASA Astrophysics Data System (ADS)

    Di Troia, C.

    2015-04-01

    The exact analytical description of non relativistic charge motion in general magnetic fields is, apparently, a simple problem, even if it has not been solved until now, apart for rare cases. The key feature of the present derivation is to adopt a non perturbative magnetic field description to find new solutions of motion. Among all solutions, two are particularly important: guiding particle and gyro-particle solutions. The guiding particle has been characterized to be minimally coupled to the magnetic field; the gyro-particle has been defined to be maximally coupled to the magnetic field and, also, to move on a closed orbit. The generic charged particle motion is shown to be expressed as the sum of such particular solutions. This non perturbative approach corresponds to the description of the particle motion in the gyro-center and/or guiding center reference frame obtained at all the orders of the modern gyro-center transformation. The Boltzmann equation is analyzed with the described exact guiding center coordinates. The obtained gyrokinetic equation is solved for the Boltzmann equation at marginal stability conditions.

  8. Perturbative path-integral study of active- and passive-tracer diffusion in fluctuating fields.

    PubMed

    Démery, Vincent; Dean, David S

    2011-07-01

    We study the effective diffusion constant of a Brownian particle linearly coupled to a thermally fluctuating scalar field. We use a path-integral method to compute the effective diffusion coefficient perturbatively to lowest order in the coupling constant. This method can be applied to cases where the field is affected by the particle (an active tracer) and cases where the tracer is passive. Our results are applicable to a wide range of physical problems, from a protein diffusing in a membrane to the dispersion of a passive tracer in a random potential. In the case of passive diffusion in a scalar field, we show that the coupling to the field can, in some cases, speed up the diffusion corresponding to a form of stochastic resonance. Our results on passive diffusion are also confirmed via a perturbative calculation of the probability density function of the particle in a Fokker-Planck formulation of the problem. Numerical simulations on simplified systems corroborate our results. PMID:21867153

  9. Modelling of ion energy transport in perturbed magnetic field in collisionless toroidal plasma

    NASA Astrophysics Data System (ADS)

    Kanno, Ryutaro; Nunami, Masanori; Satake, Shinsuke; Takamaru, Hisanori; Okamoto, Masao; Ohyabu, Nobuyoshi

    2010-11-01

    Although all physical parameters of background plasma and magnetic field are fixed, it is not trivial that transport coefficients in an ergodic region bounded radially on both sides can be always evaluated as constants with respect to time because of non-Brownian motion of guiding centres in low-collisionality cases, as shown previously in mono-energetic test-particle simulations by Maluckov et al (2003 Physica A 322 13). Here the ergodic region consists of chaotic magnetic field lines caused by resonant magnetic perturbations (RMPs). In order to understand the fundamental properties of transport phenomena in the radially bounded ergodic region, a new computer simulation code based on the δf method solving the drift kinetic equation is developed and the energy transport of ions (protons) in the perturbed magnetic field is investigated in low-collisionality cases. We evaluate the ion thermal diffusivity as a constant with respect to time by using a quasi-steady-state solution of the guiding centre distribution function in five-dimensional phase space and find that the diffusivity depends on both the strength of the RMPs and the collision frequency. The diffusivity estimated by the δf simulation in the ergodic region is extremely small compared with the prediction of field-line diffusion theory. The radial transport is affected by the fact that the width of the ergodic region is finite.

  10. From charge motion in general magnetic fields to the non perturbative gyrokinetic equation

    SciTech Connect

    Di Troia, C.

    2015-04-15

    The exact analytical description of non relativistic charge motion in general magnetic fields is, apparently, a simple problem, even if it has not been solved until now, apart for rare cases. The key feature of the present derivation is to adopt a non perturbative magnetic field description to find new solutions of motion. Among all solutions, two are particularly important: guiding particle and gyro-particle solutions. The guiding particle has been characterized to be minimally coupled to the magnetic field; the gyro-particle has been defined to be maximally coupled to the magnetic field and, also, to move on a closed orbit. The generic charged particle motion is shown to be expressed as the sum of such particular solutions. This non perturbative approach corresponds to the description of the particle motion in the gyro-center and/or guiding center reference frame obtained at all the orders of the modern gyro-center transformation. The Boltzmann equation is analyzed with the described exact guiding center coordinates. The obtained gyrokinetic equation is solved for the Boltzmann equation at marginal stability conditions.

  11. Auxiliary Conformally Invariant Higher-Spin Field in de Sitter Space

    NASA Astrophysics Data System (ADS)

    Elmizadeh, M.; Tanhayi, M. R.

    2016-03-01

    We employ de Sitter isometry to study a mixed symmetric rank-3 tensor field in de Sitter space by finding the field equation, solution and two-point function which are conformally invariant. It is proved that such a tensor field plays a key role in conformal theory of linear gravity (Binegar et al., Phys. Rev. D 27, 2249, 1983) . In de Sitter space from the group theoretical point of view this kind of tensor could associate with two unitary irreducible representations (UIR) of the de Sitter group (Takook et al., J.Math. Phys. 51, 032503, 2010), which one representation has a flat limit, namely, in zero curvature coincides to the UIR of Poincaré group, however, the second one which is named as auxiliary field, becomes significant in the study of conformal gravity in de Sitter background. We show that the rank-3 tensor solution can be written in terms of a massless minimally coupled scalar field and also the related two-point function is a function of a massless minimally coupled scalar two-point function.

  12. Ulysses Observations of Tripolar Guide-Magnetic Field Perturbations Across Solar Wind Reconnection Exhausts

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Peng, B.; Markidis, S.; Gosling, J. T.; McComas, D. J.; Lapenta, G.; Newman, D. L.

    2014-12-01

    We report observations from 15 solar wind reconnection exhausts encountered along the Ulysses orbit beyond 4 AU in 1996-1999 and 2002-2005. The events, which lasted between 17 and 45 min, were found at heliospheric latitudes between -36o and 21o with one event detected as high as 58o. All events shared a common characteristic of a tripolar guide-magnetic field perturbation being detected across the observed exhausts. The signature consists of an enhanced guide field magnitude within the exhaust center and two regions of significantly depressed guide-fields adjacent to the center region. The events displayed magnetic field shear angles as low as 37o with a mean of 89o. This corresponds to a strong external guide field relative to the anti-parallel reconnecting component of the magnetic field with a mean ratio of 1.3 and a maximum ratio of 3.1. A 2-D kinetic reconnection simulation for realistic solar wind conditions reveals that tripolar guide fields form at current sheets in the presence of multiple X-lines as two magnetic islands interact with one another for such strong guide fields. The Ulysses observations are also compared with the results of a 3-D kinetic simulation of multiple flux ropes in a strong guide field.

  13. Non-perturbative treatment of strongly-interacting fields: Insights from liquid theory

    NASA Astrophysics Data System (ADS)

    Trachenko, K.; Brazhkin, V. V.

    2014-08-01

    We outline a new programme of solving the problem of treating strong interactions in field theories. The programme does not involve perturbation theories and associated problems of divergences. We apply our recent idea of treating strongly interacting liquids to field theories by showing the equivalence of Hamiltonians of liquids and interacting fields. In this approach, the motion of the field results in the disappearance of n-1 transverse modes with frequency smaller than the Frenkel frequency ωF, similar to the loss of two transverse modes in a liquid with frequency ω<ωF. We illustrate the proposed programme with the calculation of the energy and propagator, and show that the results cannot be obtained in perturbation theory to any finite order. Importantly, the Frenkel energy gap EF=ħωF and the associated massive Frenkel particle naturally appear in our consideration, the result that is relevant for current efforts to demonstrate a mass gap in interacting field theories such as Yang-Mills theory. Notably, our mechanism involves a physically sensible starting point in terms of real masses (frequencies) in the harmonic non-interacting field, in contrast to the Higgs effect involving the imaginary mass as a starting point. We further note that the longitudinal mode in our approach remains gapless, implying that both short-range and long-range forces with massive and massless particles naturally emerge and unify in a single interacting field, a result not hitherto anticipated. Finally, we comment on the relationship between our results and hydrodynamic description of the quark-gluon plasma.

  14. Stochastic geometry of critical curves, Schramm Loewner evolutions and conformal field theory

    NASA Astrophysics Data System (ADS)

    Gruzberg, Ilya A.

    2006-10-01

    Conformally invariant curves that appear at critical points in two-dimensional statistical mechanics systems and their fractal geometry have received a lot of attention in recent years. On the one hand, Schramm (2000 Israel J. Math. 118 221 (Preprint math.PR/9904022)) has invented a new rigorous as well as practical calculational approach to critical curves, based on a beautiful unification of conformal maps and stochastic processes, and by now known as Schramm-Loewner evolution (SLE). On the other hand, Duplantier (2000 Phys. Rev. Lett. 84 1363; Fractal Geometry and Applications: A Jubilee of Benot Mandelbrot: Part 2 (Proc. Symp. Pure Math. vol 72) (Providence, RI: American Mathematical Society) p 365 (Preprint math-ph/0303034)) has applied boundary quantum gravity methods to calculate exact multifractal exponents associated with critical curves. In the first part of this paper, I provide a pedagogical introduction to SLE. I present mathematical facts from the theory of conformal maps and stochastic processes related to SLE. Then I review basic properties of SLE and provide practical derivation of various interesting quantities related to critical curves, including fractal dimensions and crossing probabilities. The second part of the paper is devoted to a way of describing critical curves using boundary conformal field theory (CFT) in the so-called Coulomb gas formalism. This description provides an alternative (to quantum gravity) way of obtaining the multifractal spectrum of critical curves using only traditional methods of CFT based on free bosonic fields.

  15. Perturbative Aspects of the Chern-Simons Topological Quantum Field Theory

    NASA Astrophysics Data System (ADS)

    Bar-Natan, Dror-Dror

    We investigate the Feynman-diagram perturbative expansion of the Chern-Simons topological quantum field theory. After introducing the theory, we compute the on -loop expectation value for knots and links, recovering Gauss' linking number formula for links and the self-linking number of a framed knot. The self-linking formula is shown to suffer from an anomaly proportional to the total torsion of the knot, whose definition requires 'framing' the knot. This explains the appearance of framings. In an appendix, we use these results to characterize the total torsion of a curve as the only parametrization independent quantity of vanishing scaling dimension having 'local' variation, explaining why no further anomalies are expected. We then treat rigorously the two loop expectation value of a knot, finding it to be finite and invariant under isotopy. We identify the resulting knot invariant to essentially be the second coefficient of the Conway polynomial, in agreement with Witten's earlier non-perturbative computation. We give 'formal' (namely, algebraic with missing analytical details) proofs that the perturbative expansion gives manifold and link invariants and suggest that a slight generalization of the Feynman rules of the Chern-Simons theory might still give knot invariants, possibly new. We discuss the relation between perturbation theory and the Vassiliev knot invariants, solving a related algebraic problem posed by Birman and Lin. We compute the stationary phase approximation to the Chern-Simons path integral with compact and non -compact gauge group, explaining the appearance of framings of 3-manifolds and the so called 'shift in k', and finding the result in the non-compact case not to be a simple analytic continuation of the result in the compact case. Finally we outline our expectation for the behavior of the theory beyond the one- and two-loop rigorous results.

  16. Primordial Perturbations Produced by a Self Interacting Scalar Field in the Braneworld: The Dynamical Systems Perspective

    NASA Astrophysics Data System (ADS)

    García Aspeitia, Miguel A.; Magaña, Juan Aldebarán; Matos, Tonatiuh; Rodriguez, Pablo A.

    2010-07-01

    In this work we explore the primordial perturbations by the slow-roll inflation produced by the simplest chaotic inflation model driven by a scalar field with potential VΦ = 12mφ2φ2 in a hidden brane and it is analyzed through a dynamical system to explore the consecuences in the evolution of the visible brane (our Universe). We use the most accepted constraints of the five dimensional Planck mass endorsed by the current experimental data in our universe (visible brane) to fit the initial conditions of φ and φ of the inflation in the hidden brane.

  17. Use of Earth’s Magnetic Field for Mitigating Gyroscope Errors Regardless of Magnetic Perturbation

    PubMed Central

    Afzal, Muhammad Haris; Renaudin, Valérie; Lachapelle, Gérard

    2011-01-01

    Most portable systems like smart-phones are equipped with low cost consumer grade sensors, making them useful as Pedestrian Navigation Systems (PNS). Measurements of these sensors are severely contaminated by errors caused due to instrumentation and environmental issues rendering the unaided navigation solution with these sensors of limited use. The overall navigation error budget associated with pedestrian navigation can be categorized into position/displacement errors and attitude/orientation errors. Most of the research is conducted for tackling and reducing the displacement errors, which either utilize Pedestrian Dead Reckoning (PDR) or special constraints like Zero velocity UPdaTes (ZUPT) and Zero Angular Rate Updates (ZARU). This article targets the orientation/attitude errors encountered in pedestrian navigation and develops a novel sensor fusion technique to utilize the Earth’s magnetic field, even perturbed, for attitude and rate gyroscope error estimation in pedestrian navigation environments where it is assumed that Global Navigation Satellite System (GNSS) navigation is denied. As the Earth’s magnetic field undergoes severe degradations in pedestrian navigation environments, a novel Quasi-Static magnetic Field (QSF) based attitude and angular rate error estimation technique is developed to effectively use magnetic measurements in highly perturbed environments. The QSF scheme is then used for generating the desired measurements for the proposed Extended Kalman Filter (EKF) based attitude estimator. Results indicate that the QSF measurements are capable of effectively estimating attitude and gyroscope errors, reducing the overall navigation error budget by over 80% in urban canyon environment. PMID:22247672

  18. Vacuum modeling of three-dimensional magnetic field topology under resonant magnetic perturbations on EAST

    NASA Astrophysics Data System (ADS)

    Jia, M.; Sun, Y.; Zhong, F.; Li, H.; Li, G.; Wang, L.; Gan, K.; Zhang, B.; Qian, J.; Shen, B.

    2016-05-01

    A numerical model using field line tracing for modeling of three-dimensional magnetic field topology under resonant magnetic perturbations (RMPs) on experimental advanced superconducting tokamak (EAST) is presented. The topological structure is calculated in the vacuum paradigm. The modeling result predicts that the possible strike point splitting on a plasma-facing component and the lobes-like structure on the boundary are observable in the diagnostics at different locations. It is shown that the magnetic perturbations with a resonant dominant spectrum can induce a large footprint splitting effect as well as a wide stochastic layer. This is useful for observations using diagnostics with limited spatial resolution. The impact of RMP fields on marginally disconnected double null configurations is investigated. To avoid the transient heat load on the upper divertor or plasma-facing components near the upper x-point, it is necessary to keep the distance between two separatrices of a near double null configuration larger than a threshold value that depends on the RMP strength and the equilibrium properties. A preliminary RMP experiment on EAST shows that there is a good agreement between the splitting width predicted by the code and that of the particle flux measured by divertor probes. An enhancement of particle flux on the upper divertor during the RMP phase is observed in the lower single null discharge.

  19. Field perturbation experiments, an alternate approach to the assessment of human effects in terrestrial ecosystems

    SciTech Connect

    Suter, II, G W

    1980-01-01

    The National Environmental Policy Act of 1969 (NEPA) was initially interpreted as requiring full disclosure of the environmental impacts of a federal action. Because of the limitations of time, money, and manpower, this requirement that all impacts be considered has led to superficial analysis of many important impacts. Data collection has largely been limited to the enumeration of species because this information can be applied to the analysis of any problem. The President's Council on Environmental Quality (CEQ) has provided a solution to this problem by reinterpreting NEPA as requiring analysis of those impacts which have significant bearing on decision making. Because assessment resources can now be concentrated on a few critical issues, it should be possible to perform field perturbation experiments to provide direct evidence of the effects of a specific mixture of pollutants or physical disturbances on the specific mixture of pollutants or physical disturbances on the specific receiving ecosystem. Techniques are described for field simulation of gaseous and particulate air pollution, soil pollutants, disturbance of the earth's surface, and disturbance of wildlife. These techniques are discussed in terms of their realism, cost, and the restrictions which they place on the measurement of ecological parameters. Development and use of these field perturbation techniques should greatly improve the accuracy of predictive assessments and further our understanding of ecosystem processes.

  20. Tumor Treating Fields Perturb the Localization of Septins and Cause Aberrant Mitotic Exit

    PubMed Central

    Holtzman, Talia S.; Lee, Sze Xian; Wong, Eric T.; Swanson, Kenneth D.

    2015-01-01

    The anti-tumor effects of chemotherapy and radiation are thought to be mediated by triggering G1/S or G2/M cell cycle checkpoints, while spindle poisons, such as paclitaxel, block metaphase exit by initiating the spindle assembly checkpoint. In contrast, we have found that 150 kilohertz (kHz) alternating electric fields, also known as Tumor Treating Fields (TTFields), perturbed cells at the transition from metaphase to anaphase. Cells exposed to the TTFields during mitosis showed normal progression to this point, but exhibited uncontrolled membrane blebbing that coincided with metaphase exit. The ability of such alternating electric fields to affect cellular physiology is likely to be dependent on their interactions with proteins possessing high dipole moments. The mitotic Septin complex consisting of Septin 2, 6 and 7, possesses a high calculated dipole moment of 2711 Debyes (D) and plays a central role in positioning the cytokinetic cleavage furrow, and governing its contraction during ingression. We showed that during anaphase, TTFields inhibited Septin localization to the anaphase spindle midline and cytokinetic furrow, as well as its association with microtubules during cell attachment and spreading on fibronectin. After aberrant metaphase exit as a consequence of TTFields exposure, cells exhibited aberrant nuclear architecture and signs of cellular stress including an overall decrease in cellular proliferation, followed by apoptosis that was strongly influenced by the p53 mutational status. Thus, TTFields are able to diminish cell proliferation by specifically perturbing key proteins involved in cell division, leading to mitotic catastrophe and subsequent cell death. PMID:26010837

  1. Toroidal modeling of plasma response and resonant magnetic perturbation field penetration

    NASA Astrophysics Data System (ADS)

    Liu, Y. Q.; Kirk, A.; Sun, Y.; Cahyna, P.; Chapman, I. T.; Denner, P.; Fishpool, G.; Garofalo, A. M.; Harrison, J. R.; Nardon, E.; the MAST Team

    2012-12-01

    The penetration dynamics of the resonant magnetic perturbation (RMP) field is simulated in the full toroidal geometry, under realistic plasma conditions in MAST experiments. The physics associated with several aspects of the RMP penetration—the plasma response and rotational screening, the resonant and non-resonant torques and the toroidal momentum balance—are highlighted. In particular, the plasma response is found to significantly amplify the non-resonant component of the RMP field for some of the MAST plasmas. A fast rotating plasma, in response to static external magnetic fields, experiences a more distributed electromagnetic torque due to the resonance with continuum waves in the plasma. At fast plasma flow (such as for the MAST plasma), the electromagnetic torque is normally dominant over the neoclassical toroidal viscous (NTV) torque. However, at sufficiently slow plasma flow, the NTV torque can play a significant role in the toroidal momentum balance, thanks to the precession drift resonance enhanced, so-called superbanana plateau regime.

  2. On the correction, perturbation and modification of small field detectors in relative dosimetry.

    PubMed

    Papaconstadopoulos, P; Tessier, F; Seuntjens, J

    2014-10-01

    The purpose of this study was to derive a complete set of correction and perturbation factors for output factors (OF) and dose profiles. Modern small field detectors were investigated including a plastic scintillator (Exradin W1, SI), a liquid ionization chamber (microLion 31018, PTW), an unshielded diode (Exradin D1V, SI) and a synthetic diamond (microDiamond 60019, PTW). A Monte Carlo (MC) beam model was commissioned for use in small fields following two commissioning procedures: (1) using intermediate and moderately small fields (down to 2 × 2 cm(2)) and (2) using only small fields (0.5 × 0.5 cm(2) -2 × 2 cm(2)). In the latter case the detectors were explicitly modelled in the dose calculation. The commissioned model was used to derive the correction and perturbation factors with respect to a small point in water as suggested by the Alfonso formalism. In MC calculations the design of two detectors was modified in order to minimize or eliminate the corrections needed. The results of this study indicate that a commissioning process using large fields does not lead to an accurate estimation of the source size, even if a 2 × 2 cm(2) field is included. Furthermore, the detector should be explicitly modelled in the calculations. On the output factors, the scintillator W1 needed the smallest correction (+0.6%), followed by the microDiamond (+1.3%). Larger corrections were observed for the microLion (+2.4%) and diode D1V (-2.4%). On the profiles, significant corrections were observed out of the field on the gradient and tail regions. The scintillator needed the smallest corrections (-4%), followed by the microDiamond (-11%), diode D1V (+13%) and microLion (-15%). The major perturbations reported were due to volume averaging and high density materials that surround the active volumes. These effects presented opposite trends in both OF and profiles. By decreasing the radius of the microLion to 0.85 mm we could modify the volume averaging effect in order

  3. [Research in two-dimensional critical phenomena and conformal field theory]. Final report

    SciTech Connect

    Not Available

    1990-12-31

    A very theoretical description is given of research in two- dimensional critical phenomena and conformal field theory. Major progress is reported in the field of fluctuating two-dimensional surfaces. A discretized representation of fluctuating geometry is used where surfaces are represented by triangulations; continuum surfaces are recovered by taking the size of the triangles to zero. One of the central goals of the theory of critical phenomena is to find all possible universality classes of n-dimensional critical phenomena; this goal has been translated into the problem of clasifying all possible scale-invariant euclidean quantum field theories. (RWR)

  4. Experimental investigation of mechanisms of mid-latitude ionosphere and geophysical fields perturbation

    NASA Astrophysics Data System (ADS)

    Gavrilov, Boris; Zetzer, Julius; Egorov, Dmitry

    The investigations are carried out to study mechanisms and channels of the mid-latitude ionosphere, near-Earth electric field and current perturbations, and their connection to high-latitude and magnetospheric events. The basis of these investigations is a measurement of the geophysical fields in the Geophysical Observatory Mikhnevo (54.9 N, 37,8 E) of the Institute of Geospheres Dynamics RAS situated at 80 km to the south from Moscow. The observatory includes a set of measuring complexes for radiophysics, magnetic, electrical, optic, infrasound, seismic, and other investigations. All of them are controlled by the united computer centre in the common scale of time. Our approach bases on well known conception that the main reasons of the mid-latitude perturbations are the processes in the auroral regions. But auroral phenomena impact on mid-latitudes by means of different physical mechanisms and agents of disturbances. Fortunately, they differ from each other in the time of their generation and velocities of their propagation. For example, the typical velocity of propagation of thermosphere winds is about 100 m/s, the acoustic gravity wave propagate with a velocity of about 400 m/s, and a prompt penetration of the magnetospheric electric field affects the mid-latitude practically instantly. If we can determine a time lag between the action of the perturbation source and mid-latitude ionosphere response, we can determine the velocity of perturbation propagation and recognize the dominating mechanisms and channels of disturbances. The important requirements for the organization of such investigation is a positioning of different measuring facilities in one place and organization of coordinated and synchronous registration of the ionosphere parameters and geophysical fields variations with high temporal resolution. The Mikhnevo observatory gives us such ability. As an indicator and marker of high latitude events (magnetic storms and substorms) we use AE-index. The

  5. Classification of operator algebraic conformal field theories in dimensions one and two

    NASA Astrophysics Data System (ADS)

    Kawahigashi, Yasuyuki

    2006-03-01

    We formulate conformal field theory in the setting of algebraic quantum field theory as Haag-Kastler nets of local observable algebras with diffeomorphism covariance on the two-dimensional Minkowski space. We then obtain a decomposition of a two-dimensional theory into two chiral theories. We give the first classification result of such chiral theories with representation theoretic invariants. That is, we use the central charge as the first invariant, and if it is less than 1, we obtain a complete classification. Our classification list contains a new net which does not seem to arise from the known constructions such as the coset or orbifold constructions. We also present a classification of full two-dimensional conformal theories. These are joint works with Roberto Longo.

  6. Entanglement entropy of black holes and anti-de Sitter space/conformal-field-theory correspondence.

    PubMed

    Solodukhin, Sergey N

    2006-11-17

    A recent proposal by Ryu and Takayanagi for a holographic interpretation of entanglement entropy in conformal field theories dual to supergravity on anti-de Sitter space is generalized to include entanglement entropy of black holes living on the boundary of anti-de Sitter space. The generalized proposal is verified in boundary dimensions d=2 and d=4 for both the uv-divergent and uv-finite terms. In dimension d=4 an expansion of entanglement entropy in terms of size L of the subsystem outside the black hole is considered. A new term in the entropy of dual strongly coupled conformal-field theory, which universally grows as L(2)lnL and is proportional to the value of the obstruction tensor at the black hole horizon, is predicted. PMID:17155672

  7. Quantum quenches in 1  +  1 dimensional conformal field theories

    NASA Astrophysics Data System (ADS)

    Calabrese, Pasquale; Cardy, John

    2016-06-01

    We review the imaginary time path integral approach to the quench dynamics of conformal field theories. We show how this technique can be applied to the determination of the time dependence of correlation functions and entanglement entropy for both global and local quenches. We also briefly review other quench protocols. We carefully discuss the limits of applicability of these results to realistic models of condensed matter and cold atoms.

  8. Thigmomorphogenesis: field and laboratory studies of Abies fraseri in response to wind or mechanical perturbation

    NASA Technical Reports Server (NTRS)

    Telewski, F. W.; Jaffe, M. J.

    1986-01-01

    Field- and greenhouse-grown Abies fraseri (Pursh) Poir. (Fraser fir) were analyzed for wind- or mechanically-induced flexure changes. These changes included inhibition of stem and needle elongation, reinforcement of branch bases around the stem, and increased radial growth in the direction of the mechanical perturbation (MP). Mature trees exposed to high wind conditions were severely flag-formed. These modified tree crowns had a lower drag than crowns of non-flag formed trees in wind-tunnel tests. In both field-grown and greenhouse-grown A. fraseri, MP induced a decrease in flexibility and increased elasticity of the stems. The increased radial growth of the stems overrode the increase in elasticity, resulting in the overall decrease in flexibility. The increase in radial growth caused by wind or mechanical flexure was due to greater cell divisions of the vascular cambium, resulting in increased numbers of tracheids. The decrease in stem elongation in these trees was due, at least in part, to a decrease in tracheid length. The potential biological and mechanical significance of these induced growth changes in trees are addressed. The data support the thigmomorphogenetic theory, which states that plants respond to wind and other mechanical perturbations in a way that is favorable to the plant for continued survival in windy environments.

  9. Conformational dynamics and aggregation behavior of piezoelectric diphenylalanine peptides in an external electric field

    PubMed Central

    Kelly, Catherine M.; Northey, Thomas; Ryan, Kate; Brooks, Bernard R.; Kholkin, Andrei; Rodriguez, Brian J.; Buchete, Nicolae-Viorel

    2014-01-01

    Aromatic peptides such as diphenylalanine (FF) have the characteristic capacity to self-assemble into ordered nanostructures such as peptide nanotubes, which are biocompatible, thermally and chemically stable, and have strong piezoelectric activity and high mechanical strength. The physical properties of FF aggregates open up a variety of potential biomedical applications. Electric fields are commonly applied to align FF nanotubes, yet little is known about the effect of the electric field on the assembly process. Using all-atom molecular dynamics with explicit water molecules, we probe the conformational dynamics of individual, solvated FF molecules with both charged and neutral ends, to account for different possible pH conditions. With charged ends, the FF molecules show more complex dynamics, experiencing three main conformational states (cis, trans and extended). We first examine the structural response of FF monomers to the application of a constant external electric field over a range of intensities. We also probe the aggregation mechanism of FF peptides, both with and without an externally applied electric field, and find that the presence of even relatively weak fields can accelerate the formation of ordered FF aggregates, primarily by facilitating the alignment of individual molecular dipole moments. The correlation between the strength of the external electric field and the local dipolar interactions is modulated both by the conformational response of individual FF peptides (e.g. backbone stretching, hydrogen bonds and relative alignment of aromatic sidechains) and by the response of neighboring FF and water molecules. These field-dependent observations may facilitate future studies on the controlled formation of nano-structured aggregates of piezoelectric peptides and the understanding of their specific electromechanical properties. PMID:25240398

  10. Delta-N formalism for the evolution of the curvature perturbations in generalized multi-field inflation

    NASA Astrophysics Data System (ADS)

    Matsuda, Tomohiro

    2009-11-01

    The δN formalism is considered to calculate the evolution of the curvature perturbation in generalized multi-field inflation models. The result is consistent with the usual calculation of the standard kinetic term. For the calculation of the generalized kinetic term, we improved the definition of the adiabatic field. Our calculation improves the usual calculation of R˙ based on the field equations and the perturbations, giving a very simple and intuitive argument for the evolution equations in terms of the perturbations of the inflaton velocity. Significance of non-equilibrium corrections are also discussed, which is caused by the small-scale (decaying) inhomogeneities. This formalism based on the modulated inflation scenario (i.e., calculation based on the perturbations related to the inflaton velocity) provides a powerful tool for investigating the signature of moduli that may appear in string theory.

  11. Hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field limit: General formalism and perturbations analysis

    NASA Astrophysics Data System (ADS)

    Suárez, Abril; Chavanis, Pierre-Henri

    2015-07-01

    Using a generalization of the Madelung transformation, we derive the hydrodynamic representation of the Klein-Gordon-Einstein equations in the weak field limit. We consider a complex self-interacting scalar field with a λ |φ |4 potential. We study the evolution of the spatially homogeneous background in the fluid representation and derive the linearized equations describing the evolution of small perturbations in a static and in an expanding Universe. We compare the results with simplified models in which the gravitational potential is introduced by hand in the Klein-Gordon equation, and assumed to satisfy a (generalized) Poisson equation. Nonrelativistic hydrodynamic equations based on the Schrödinger-Poisson equations or on the Gross-Pitaevskii-Poisson equations are recovered in the limit c →+∞. We study the evolution of the perturbations in the matter era using the nonrelativistic limit of our formalism. Perturbations whose wavelength is below the Jeans length oscillate in time while perturbations whose wavelength is above the Jeans length grow linearly with the scale factor as in the cold dark matter model. The growth of perturbations in the scalar field model is substantially faster than in the cold dark matter model. When the wavelength of the perturbations approaches the cosmological horizon (Hubble length), a relativistic treatment is mandatory. In that case, we find that relativistic effects attenuate or even prevent the growth of perturbations. This paper exposes the general formalism and provides illustrations in simple cases. Other applications of our formalism will be considered in companion papers.

  12. Shocked magnetic fields in the perturbed galaxies NGC 3627 and NGC 4254

    NASA Astrophysics Data System (ADS)

    Chyży, K. T.; Soida, M.; Urbanik, M.; Beck, R.

    Normal spiral galaxies usually show magnetic fields well aligned with spiral arms. However, recently Beck et al. (1999, Nature 397, 324) discovered a sudden magnetic field jump in the barred spiral NGC~1097 associated (but not coincident) with the bar-driven shock. To study such phenomena in detail we performed a VLA study at 8.44~GHz and 4.85~GHz of two perturbed galaxies: the tidally interacting NGC~3627 and the wind-swept NGC~4254. NGC~3627 shows a sudden jump of magnetic field direction close to a heavy dust lane in the western arm. However, contrary to predictions of the density wave shock models, the magnetic "shock" is displaced by about 1~kpc upstream from the dust lane. In the eastern arm, the magnetic field ignores the region of strong gas compression, running across the heavy dust lane at a high angle. Such behaviour was never seen before in spiral galaxies. NGC~4254 shows a bright narrow polarized ridge along its southern edge, suggestive for a shock caused by the intergalactic wind. However, against classical shock models the magnetic field shows a shock-like, sudden deviation along the line perpendicular to the ridge. Strong gradients of Faraday rotation in this region imply a complex, three dimensional magnetic field twisting.

  13. Hyperfine magnetic field at Ta impurities in nickel: Perturbed angular correlation and first principle calculation study

    NASA Astrophysics Data System (ADS)

    Cekić, B. Dj.; Umićević, A. B.; Belošević-Čavor, J. N.; Koteski, V. J.; Ivanovski, V. N.; Stojković, M. N.

    2008-03-01

    The hyperfine magnetic field (H) in 0.2 at.% Hf-Ni alloy is measured at the 181Ta probe using the time-differential perturbed angular correlation (TDPAC) method, in the temperature range 78-675 K. The obtained value of 8.6 (3) T at room temperature is in good agreement with the previously reported measurements for similar Hf concentrations in Ni. X-ray powder diffraction (XRPD) experiments confirmed that small atomic concentrations of Hf atoms (<1 at.%) mainly substitute on Ni lattice sites in the fcc crystal lattice without forming any intermetallic phase. In addition, ab-initio calculation using all-electron augmented plane waves plus local orbitals (APW+lo) formalism is performed and the obtained result for the hyperfine magnetic field at Ta site is in accordance with the measurement.

  14. Material deposition and migration processes with resonant magnetic perturbation fields at TEXTOR

    NASA Astrophysics Data System (ADS)

    Laengner, Ruth; Schmitz, O.; Brezinsek, S.; Coenen, J. W.; Eich, T.; Freisinger, M.; Kirschner, A.; Kreter, A.; Möller, S.; Laengner, M.; Philipps, V.; Pospieszczyk, A.; Reimer, H.; Samm, U.; Wienhold, P.; Textor Team

    2013-07-01

    Resonant Magnetic Perturbations (RMPs) are applied with the Dynamic Ergodic Divertor (DED) at TEXTOR to control the plasma edge transport and the plasma surface interaction. This leads to the formation of a three-dimensional (3D) topology of the scrape-off layer (SOL). To quantify the erosion/deposition balance and the material migration in this 3D boundary, spherical test limiters were exposed to plasmas with and without RMP fields applied. Methane doped with 13C as tracer element was injected through a gas inlet in the test limiter. The local gas source was monitored by spatially resolving spectroscopy and the resulting deposition patterns on the limiters were analysed with colourimetry and nuclear reaction analysis. These measurements were compared to simulations of the magnetic field topology simulations. The data provide evidence of a particle migration dominated by an ExB drift within stochastic zones of the 3D plasma boundary.

  15. Subsolar magnetopause observation and kinetic simulation of a tripolar guide magnetic field perturbation consistent with a magnetic island

    NASA Astrophysics Data System (ADS)

    Eriksson, S.; Cassak, P. A.; Retinò, A.; Mozer, F. S.

    2016-04-01

    The Polar satellite recorded two reconnection exhausts within 6 min on 1 April 2001 across a subsolar magnetopause that displayed a symmetric plasma density, but different out-of-plane magnetic field signatures for similar solar wind conditions. The first magnetopause crossing displayed a bipolar guide field variation in a weak external guide field consistent with a symmetric Hall field from a single X line. The subsequent crossing represents the first observation of a tripolar guide field perturbation at Earth's magnetopause in a strong guide field. This perturbation consists of a significant guide field enhancement between two narrow guide field depressions. A particle-in-cell simulation for the prevailing conditions across this second event resulted in a magnetic island between two simulated X lines across which a tripolar guide field developed consistent with the observation. The simulated island supports a scenario whereby Polar encountered the asymmetric quadrupole Hall magnetic fields between two X lines for symmetric conditions across the magnetopause.

  16. Perturbation theory, effective field theory, and oscillations in the power spectrum

    NASA Astrophysics Data System (ADS)

    Vlah, Zvonimir; Seljak, Uroš; Yat Chu, Man; Feng, Yu

    2016-03-01

    We explore the relationship between the nonlinear matter power spectrum and the various Lagrangian and Standard Perturbation Theories (LPT and SPT). We first look at it in the context of one dimensional (1-d) dynamics, where 1LPT is exact at the perturbative level and one can exactly resum the SPT series into the 1LPT power spectrum. Shell crossings lead to non-perturbative effects, and the PT ignorance can be quantified in terms of their ratio, which is also the transfer function squared in the absence of stochasticity. At the order of PT we work, this parametrization is equivalent to the results of effective field theory (EFT), and can thus be expanded in terms of the same parameters. We find that its radius of convergence is larger than the SPT loop expansion. The same EFT parametrization applies to all SPT loop terms and if stochasticity can be ignored, to all N-point correlators. In 3-d, the LPT structure is considerably more complicated, and we find that LPT models with parametrization motivated by the EFT exhibit running with k and that SPT is generally a better choice. Since these transfer function expansions contain free parameters that change with cosmological model their usefulness for broadband power is unclear. For this reason we test the predictions of these models on baryonic acoustic oscillations (BAO) and other primordial oscillations, including string monodromy models, for which we ran a series of simulations with and without oscillations. Most models are successful in predicting oscillations beyond their corresponding PT versions, confirming the basic validity of the model. We show that if primordial oscillations are localized to a scale q, the wiggles in power spectrum are approximately suppressed as exp[-k2Σ2(q)/2], where Σ(q) is rms displacement of particles separated by q, which saturates on large scales, and decreases as q is reduced. No oscillatory features survive past k ~ 0.5h/Mpc at z = 0.

  17. Orbit-attitude perturbation of a charged spacecraft in the geomagnetic field

    NASA Astrophysics Data System (ADS)

    Mohammed, Hani M.; Ahmed, M. K. M.; Owis, Ashraf H.

    2012-06-01

    In this work we investigate the orbit-attitude perturbations of a rigid spacecraft due to the effects of several forces and torques. The spacecraft is assumed to be of a cylindrical shape and equipped with a charged screen with charge density ξ. Clearly the main force affecting the motion of the spacecraft is the gravitational force of the Earth with uniform spherical mass. The effect of oblate Earth up to J2 is considered as perturbation on both the orbit and attitude of the spacecraft, where the attitude of the spacecraft is acted upon by what is called gravity gradient torque. Another source of perturbation on the attitude of the spacecraft comes from the motion of the charged spacecraft in the geomagnetic field. This motion generates a force known as the Lorentz force which is the source of the Lorentz force torque influencing the rotational motion of the spacecraft. In this work we give an analytical treatment of the orbital-rotational dynamics of the spacecraft. We first use the definitions of Delaunay and Andoyer variables in order to formulate the Hamiltonian of the orbit-attitude motion under the effects of forces and torques of interest. Since the Lorentz force is a non-conservative force, a potential like function is introduced and added to the Hamiltonian. We solve the canonical equations of the Hamiltonian system by successive transformations using a technique proposed by Lie and modified by Deprit and Kamel to solve the problem. In this technique we make two successive transformations to eliminate.

  18. CMB power spectra induced by primordial cross-bispectra between metric perturbations and vector fields

    SciTech Connect

    Shiraishi, Maresuke; Saga, Shohei; Yokoyama, Shuichiro E-mail: saga.shohei@nagoya-u.jp

    2012-11-01

    We study temperature and polarization anisotropies of the cosmic microwave background (CMB) radiation sourced from primordial cross-bispectra between metric perturbations and vector fields, which are generated from the inflation model where an inflaton and a vector field are coupled. In case the vector field survives after the reheating, both the primordial scalar and tensor fluctuations can be enhanced by the anisotropic stress composed of the vector fields during radiation dominated era. We show that through this enhancement the primordial cross-bispectra generate not only CMB bispectra but also CMB power spectra. In general, we can expect such cross-bispectra produce the non-trivial mode-coupling signals between the scalar and tensor fluctuations. However, we explicitly show that such mode-coupling signals do not appear in CMB power spectra. Through the numerical analysis of the CMB scalar-mode power spectra, we find that although signals from these cross-bispectra are smaller than primary non-electromagnetic ones, these have some characteristic features such as negative auto-correlations of the temperature and polarization modes, respectively. On the other hand, signals from tensor modes are almost comparable to primary non-electromagnetic ones and hence the shape of observed B-mode spectrum may deviate from the prediction in the non-electromagnetic case. The above imprints may help us to judge the existence of the coupling between the scalar and vector fields in the early Universe.

  19. Covariant second-order perturbations in generalized two-field inflation

    SciTech Connect

    Tzavara, Eleftheria; Tent, Bartjan van; Mizuno, Shuntaro E-mail: Shuntaro.Mizuno@apc.univ-paris7.fr

    2014-07-01

    We examine the covariant properties of generalized models of two-field inflation, with non-canonical kinetic terms and a possibly non-trivial field metric. We demonstrate that kinetic-term derivatives and covariant field derivatives do commute in a proper covariant framework, which was not realized before in the literature. We also define a set of generalized slow-roll parameters, using a unified notation. Within this framework, we study the most general class of models that allows for well-defined adiabatic and entropic sound speeds, which we identify as the models with parallel momentum and field velocity vectors. For these models we write the exact cubic action in terms of the adiabatic and isocurvature perturbations. We thus provide the tool to calculate the exact non-Gaussianity beyond slow-roll and at any scale for these generalized models. We illustrate our general results by considering their long-wavelength limit, as well as with the example of two-field DBI inflation.

  20. Hairy black holes sourced by a conformally coupled scalar field in D dimensions

    NASA Astrophysics Data System (ADS)

    Giribet, Gaston; Leoni, Matías; Oliva, Julio; Ray, Sourya

    2014-04-01

    There exist well-known no-hair theorems forbidding the existence of hairy black hole solutions in general relativity coupled to a scalar conformal field theory in asymptotically flat space. Even in the presence of cosmological constant, where no-hair theorems can usually be circumvented and black holes with conformal scalar hair were shown to exist in D≤4 dimensions, no-go results were reported for D>4. In this paper we prove that these obstructions can be evaded and we answer in the affirmative a question that remained open: Whether hairy black holes do exist in general relativity sourced by a conformally coupled scalar field in arbitrary dimensions. We find the analytic black hole solution in arbitrary dimension D>4, which exhibits a backreacting scalar hair that is regular everywhere outside and on the horizon. The metric asymptotes to (anti-)de Sitter spacetime at large distance and admits spherical horizon as well as horizon of a different topology. We also find analytic solutions when higher-curvature corrections O(Rn) of arbitrary order n are included in the gravity action.

  1. Effects of the pressure perturbation field in numerical models of unidirectionally sheared thunderstorm convection - Two versus three dimensions

    NASA Technical Reports Server (NTRS)

    Schlesinger, R. E.

    1984-01-01

    The physical roles of 'buoyant' and 'dynamic' pressure components, and the distinction between buoyant and hydrostatic pressure perturbations, are aspects of the pressure perturbation field in strongly sheared convective storms studied by means of two- and three-dimensional anelastic numerical modeling experiments with common environmental profiles. The pressure analysis clarifies the differences between two- and three-dimensional storms. In the main updraft, strong midlevel thermal buoyancy is partly opposed by a downward-perturbed vertical pressure gradient force. This, however, occurs to a much greater extent in two dimensions than in three, contributing to smaller net upward accelerations. While the buoyant and hydrostatic fields are intimately related to the total buoyancy distribution, the buoyant pressure perturbation is smoother and of lower amplitude than its hydrostatic counterpart. For the model experiments, this distinction is far greater in three dimensions than in two, in association with the smaller scale of the active convection in three dimensions.

  2. Chaotic transport in Hamiltonian systems perturbed by a weak turbulent wave field

    SciTech Connect

    Abdullaev, S. S.

    2011-08-15

    Chaotic transport in a Hamiltonian system perturbed by a weak turbulent wave field is studied. It is assumed that a turbulent wave field has a wide spectrum containing up to thousands of modes whose phases are fluctuating in time with a finite correlation time. To integrate the Hamiltonian equations a fast symplectic mapping is derived. It has a large time-step equal to one full turn in angle variable. It is found that the chaotic transport across tori caused by the interactions of small-scale resonances have a fractal-like structure with the reduced or zero values of diffusion coefficients near low-order rational tori thereby forming transport barriers there. The density of rational tori is numerically calculated and its properties are investigated. It is shown that the transport barriers are formed in the gaps of the density of rational tori near the low-order rational tori. The dependencies of the depth and width of transport barriers on the wave field spectrum and the correlation time of fluctuating turbulent field (or the Kubo number) are studied. These numerical findings may have importance in understanding the mechanisms of transport barrier formation in fusion plasmas.

  3. Information field theory for cosmological perturbation reconstruction and nonlinear signal analysis

    NASA Astrophysics Data System (ADS)

    Enßlin, Torsten A.; Frommert, Mona; Kitaura, Francisco S.

    2009-11-01

    We develop information field theory (IFT) as a means of Bayesian inference on spatially distributed signals, the information fields. A didactical approach is attempted. Starting from general considerations on the nature of measurements, signals, noise, and their relation to a physical reality, we derive the information Hamiltonian, the source field, propagator, and interaction terms. Free IFT reproduces the well-known Wiener-filter theory. Interacting IFT can be diagrammatically expanded, for which we provide the Feynman rules in position-, Fourier-, and spherical-harmonics space, and the Boltzmann-Shannon information measure. The theory should be applicable in many fields. However, here, two cosmological signal recovery problems are discussed in their IFT formulation. (1) Reconstruction of the cosmic large-scale structure matter distribution from discrete galaxy counts in incomplete galaxy surveys within a simple model of galaxy formation. We show that a Gaussian signal, which should resemble the initial density perturbations of the Universe, observed with a strongly nonlinear, incomplete and Poissonian-noise affected response, as the processes of structure and galaxy formation and observations provide, can be reconstructed thanks to the virtue of a response-renormalization flow equation. (2) We design a filter to detect local nonlinearities in the cosmic microwave background, which are predicted from some early-Universe inflationary scenarios, and expected due to measurement imperfections. This filter is the optimal Bayes’ estimator up to linear order in the nonlinearity parameter and can be used even to construct sky maps of nonlinearities in the data.

  4. Continuum resonance induced electromagnetic torque by a rotating plasma response to static resonant magnetic perturbation field

    SciTech Connect

    Liu Yueqiang; Connor, J. W.; Cowley, S. C.; Ham, C. J.; Hastie, R. J.; Hender, T. C.

    2012-10-15

    A numerical study is carried out, based on a simple toroidal tokamak equilibrium, to demonstrate the radial re-distribution of the electromagnetic torque density, as a result of a rotating resistive plasma (linear) response to a static resonant magnetic perturbation field. The computed electromagnetic torque peaks at several radial locations even in the presence of a single rational surface, due to resonances between the rotating response, in the plasma frame, and both Alfven and sound continuum waves. These peaks tend to merge together to form a rather global torque distribution, when the plasma resistivity is large. The continuum resonance induced net electromagnetic torque remains finite even in the limit of an ideal plasma.

  5. Conformational dynamics of two natively unfolded fragment peptides: Comparison of the AMBER and CHARMM force fields

    PubMed Central

    Chen, Wei; Shi, Chuanyin; MacKerell, Alexander D.; Shen, Jana

    2015-01-01

    Physics-based force fields are the backbone of molecular dynamics simulations. In recent years, significant progress has been made in the assessment and improvement of commonly-used force fields for describing conformational dynamics of folded proteins. However, the accuracy for the unfolded states remains unclear. The latter is however important for detailed studies of protein folding pathways, conformational transitions involving unfolded states and dynamics of intrinsically disordered proteins. In this work we compare the three commonly-used force fields, AMBER ff99SB-ILDN, CHARMM22/CMAP and CHARMM36, for modeling the natively unfolded fragment peptides, NTL9(1-22) and NTL9(6-17), using explicit-solvent replica-exchange molecular dynamics simulations. All three simulations show that NTL9(6-17) is completely unstructured, while NTL9(1-22) transiently samples various β-hairpin states, reminiscent of the first β-hairpin in the structure of the intact NT9 protein. The radius of gyration of the two peptides is force field independent but likely underestimated due to the current deficiency of additive force fields. Compared to the CHARMM force fields, ff99SB-ILDN gives slightly higher β-sheet propensity and more native-like residual structures for NTL9(1-22), which may be attributed to its known β preference. Surprisingly, only two sequence-local pairs of charged residues make appreciable ionic contacts in the simulations of NTL9(1-22), which are sampled slightly more by the CHARMM force fields. Taken together, these data suggest that the current CHARMM and AMBER force fields are globally in agreement in modeling the unfolded states corresponding to β-sheet in the folded structure, while differing in details such as the native-likeness of the residual structures and interactions. PMID:26020564

  6. Conformational Dynamics of Two Natively Unfolded Fragment Peptides: Comparison of the AMBER and CHARMM Force Fields.

    PubMed

    Chen, Wei; Shi, Chuanyin; MacKerell, Alexander D; Shen, Jana

    2015-06-25

    Physics-based force fields are the backbone of molecular dynamics simulations. In recent years, significant progress has been made in the assessment and improvement of commonly used force fields for describing conformational dynamics of folded proteins. However, the accuracy for the unfolded states remains unclear. The latter is however important for detailed studies of protein folding pathways, conformational transitions involving unfolded states, and dynamics of intrinsically disordered proteins. In this work, we compare the three commonly used force fields, AMBER ff99SB-ILDN, CHARMM22/CMAP, and CHARMM36, for modeling the natively unfolded fragment peptides, NTL9(1-22) and NTL9(6-17), using explicit-solvent replica-exchange molecular dynamics simulations. All three simulations show that NTL9(6-17) is completely unstructured, while NTL9(1-22) transiently samples various β-hairpin states, reminiscent of the first β-hairpin in the structure of the intact NTL9 protein. The radius of gyration of the two peptides is force field independent but likely underestimated due to the current deficiency of additive force fields. Compared to the CHARMM force fields, ff99SB-ILDN gives slightly higher β-sheet propensity and more native-like residual structures for NTL9(1-22), which may be attributed to its known β preference. Surprisingly, only two sequence-local pairs of charged residues make appreciable ionic contacts in the simulations of NTL9(1-22), which are sampled slightly more by the CHARMM force fields. Taken together, these data suggest that the current CHARMM and AMBER force fields are globally in agreement in modeling the unfolded states corresponding to β-sheet in the folded structure, while differing in details such as the native-likeness of the residual structures and interactions. PMID:26020564

  7. Supersymmetric moose models: An extra dimension from a broken deformed conformal field theory

    NASA Astrophysics Data System (ADS)

    Erlich, Joshua; Anly Tan, Jong

    2006-09-01

    We find a class of four dimensional deformed conformal field theories which appear extra dimensional when their gauge symmetries are spontaneously broken. The theories are supersymmetric moose models which flow to interacting conformal fixed points at low energies, deformed by superpotentials. Using a-maximization we give strong nonperturbative evidence that the hopping terms in the resulting latticized action are relevant deformations of the fixed-point theories. These theories have an intricate structure of RG flows between conformal fixed points. Our results suggest that at the stable fixed points each of the bulk gauge couplings and superpotential hopping terms is turned on, in favor of the extra-dimensional interpretation of the theory. However, we argue that the higher-dimensional gauge coupling is generically small compared to the size of the extra dimension. In the presence of a brane the topology of the extra dimension is determined dynamically and depends on the numbers of colors and bulk and brane flavors, which suggests phenomenological applications. The RG flows between fixed points in these theories provide a class of tests of Cardy’s conjectured a-theorem.

  8. Supersymmetric moose models: An extra dimension from a broken deformed conformal field theory

    SciTech Connect

    Erlich, Joshua; Anly Tan, Jong

    2006-09-15

    We find a class of four dimensional deformed conformal field theories which appear extra dimensional when their gauge symmetries are spontaneously broken. The theories are supersymmetric moose models which flow to interacting conformal fixed points at low energies, deformed by superpotentials. Using a-maximization we give strong nonperturbative evidence that the hopping terms in the resulting latticized action are relevant deformations of the fixed-point theories. These theories have an intricate structure of RG flows between conformal fixed points. Our results suggest that at the stable fixed points each of the bulk gauge couplings and superpotential hopping terms is turned on, in favor of the extra-dimensional interpretation of the theory. However, we argue that the higher-dimensional gauge coupling is generically small compared to the size of the extra dimension. In the presence of a brane the topology of the extra dimension is determined dynamically and depends on the numbers of colors and bulk and brane flavors, which suggests phenomenological applications. The RG flows between fixed points in these theories provide a class of tests of Cardy's conjectured a-theorem.

  9. Cosmological perturbations and the Weinberg theorem

    NASA Astrophysics Data System (ADS)

    Akhshik, Mohammad; Firouzjahi, Hassan; Jazayeri, Sadra

    2015-12-01

    The celebrated Weinberg theorem in cosmological perturbation theory states that there always exist two adiabatic scalar modes in which the comoving curvature perturbation is conserved on super-horizon scales. In particular, when the perturbations are generated from a single source, such as in single field models of inflation, both of the two allowed independent solutions are adiabatic and conserved on super-horizon scales. There are few known examples in literature which violate this theorem. We revisit the theorem and specify the loopholes in some technical assumptions which violate the theorem in models of non-attractor inflation, fluid inflation, solid inflation and in the model of pseudo conformal universe.

  10. The statistical relationship between magnetosheath ion temperatures and magnetic field perturbations throughout the dayside magnetosheath.

    NASA Astrophysics Data System (ADS)

    Dimmock, Andrew; Osmane, Adnane; Pulkkinen, Tuija; Nykyri, Katariina

    2016-04-01

    The magnetosheath layer functions as an interface between interplanetary and near Earth space. As a result, the magnetosheath plasma properties dictate the efficiency and occurrence of processes which regulate the energy and momentum transport to the inner magnetosphere. Two (and possibly correlated) magnetosheath plasma properties which may play a significant role are ion temperatures and magnetic field perturbations; both of which comfortably exceed their solar wind counterparts. It has been proposed that magnetic field fluctuations, particularly those close to ion gyro-scales, can heat ions. In some cases, especially close to the magnetopause, these may facilitate diffusive plasma transport via kinetic Alfvén waves. The results presented here describe a statistical study using THEMIS and OMNI data between 2008 through 2015 in which we study the statistical relationship between magnetosheath ion temperatures and magnetic field variations over Pc 1-5 scale lengths. We show that higher amplitude fluctuations behind the quasi-parallel shock can produce higher ion temperatures subsequently driving a dawn-dusk asymmetry. We will also determine which scale/s are more effective at driving higher temperatures. We ascertain whether this relationship varies with spatial location, and if there are any global implications.

  11. Tests of conformal field theory at the Yang-Lee singularity

    SciTech Connect

    Wydro, Tomasz; McCabe, John F.

    2009-12-14

    This paper studies the Yang-Lee edge singularity of 2-dimensional (2D) Ising model based on a quantum spin chain and transfer matrix measurements on the cylinder. Based on finite-size scaling, the low-lying excitation spectrum is found at the Yang-Lee edge singularity. Based on transfer matrix techniques, the single structure constant is evaluated at the Yang-Lee edge singularity. The results of both types of measurements are found to be fully consistent with the predictions for the (A{sub 4}, A{sub 1}) minimal conformal field theory, which was previously identified with this critical point.

  12. Conformally covariant quantization of the Maxwell field in de Sitter space

    NASA Astrophysics Data System (ADS)

    Faci, S.; Huguet, E.; Queva, J.; Renaud, J.

    2009-12-01

    In this article, we quantize the Maxwell (“massless spin one”) de Sitter field in a conformally invariant gauge. This quantization is invariant under the SO0(2,4) group and consequently under the de Sitter group. We obtain a new de Sitter-invariant two-point function which is very simple. Our method relies on the one hand on a geometrical point of view which uses the realization of Minkowski, de Sitter and anti-de Sitter spaces as intersections of the null cone in R6 and a moving plane, and on the other hand on a canonical quantization scheme of the Gupta-Bleuler type.

  13. Wilson lines and holographic entanglement entropy in Galilean conformal field theories

    NASA Astrophysics Data System (ADS)

    Basu, Rudranil; Riegler, Max

    2016-02-01

    In this paper we present in more detail a construction using Wilson lines and the corresponding dual Galilean conformal field theory calculations for analytically determining holographic entanglement entropy for flat space in 2 +1 dimensions first presented in A. Bagchi, R. Basu, D. Grumiller, and M. Riegler, Phys. Rev. Lett. 114, 111602 (2015). In addition, we show how the construction using Wilson lines can be expanded to flat space higher-spin theories and determine the thermal entropy of (spin-3 charged) flat space cosmologies using this approach.

  14. Spectral perturbations from silicon diode detector encapsulation and shielding in photon fields

    SciTech Connect

    Eklund, Karin; Ahnesjoe, Anders

    2010-11-15

    Purpose: Silicon diodes are widely used as detectors for relative dose measurements in radiotherapy. The common manufacturing practice is to encapsulate the diodes in plastic for protection and to facilitate mounting in scanning devices. Diodes intended for use in photon fields commonly also have a shield of a high atomic number material (usually tungsten) integrated into the encapsulation to selectively absorb low-energy photons to which silicon diodes would otherwise over-response. However, new response models based on cavity theories and spectra calculations have been proposed for direct correction of the readout from unshielded (e.g., ''electron'') diodes used in photon fields. This raises the question whether it is correct to assume that the spectrum in a water phantom at the location of the detector cavity is not perturbed by the detector encapsulation materials. The aim of this work is to investigate the spectral effects of typical encapsulations, including shielding, used for clinical diodes. Methods: The effects of detector encapsulation of an unshielded and a shielded commercial diode on the spectra at the detector cavity location are studied through Monte Carlo simulations with PENELOPE-2005. Variance reduction based on correlated sampling is applied to reduce the CPU time needed for the simulations. Results: The use of correlated sampling is found to be efficient and to not introduce any significant bias to the results. Compared to reference spectra calculated in water, the encapsulation for an unshielded diode is demonstrated to not perturb the spectrum, while a tungsten shielded diode caused not only the desired decrease in low-energy scattered photons but also a large increase of the primary electron fluence. Measurements with a shielded diode in a 6 MV photon beam proved that the shielding does not completely remove the field-size dependence of the detector response caused by the over-response from low-energy photons. Response factors of a properly

  15. Perturbative Particle Simulation for an Intense Ion Beam in a Periodic Quadrupole Focusing Field

    NASA Astrophysics Data System (ADS)

    Lee, W. W.

    1996-11-01

    footnotetext[1]This work is supported the DOE contract DE-AC02-76-CHO-3073. footnotetext[2]In collaboration with Q. Qian and R. C. Davidson, PPPL. Stability and transport properties of an intense ion beam propagating through an alternating-gradient quadrupole focusing field with initial Kapchinskij-Vladimirskij (KV) distribution(I. M. Kapchinksij and V. V. Vladimirskj, Proceedings of the International Conference on High Energy Accelerators and Instrumentation (CERN Geneva, 1959), p. 274.) are studied using newly-developed perturbative particle simulation techniques. Specifically, two different schemes have been investigated: the first is based on the δ f scheme originally developed for tokamak plasmas,(A. Dimits and W. W. Lee, J. Comput. Phys. 107), 309 (1993); S. Parker and W. W. Lee, Phys. Fluids B 5, 77 (1993). and the other is related to the linearized trajectory scheme.(J. Byers, Proceedings of the 4th Conference on Numerical Simulation of Plasmas, (NRL, Washington D.C., 1970),p.496.) While the former is useful for both linear and nonlinear simulations, the latter can be used for benchmark purpose. Stability properties and associated mode structures are investigated over a wide range of beam current and focusing field strength. The new schemes are found to be highly effective in describing detailed properties of beam stability and propagation over long distances. For example, a stable KV beam can indeed propagate over hundreds of lattice period in the simulation with negligible growth. On the other hand, in the unstable region when the beam current is sufficiently high,(I. Hoffman, L. Laslett, L. Smith, and I. Haber, Particle Accelerators 13), 145 (1983). large-amplitude density perturbations with (δ n)_max/hatn0 ~ 1 with low azimuthal harmonic numbers, concentrated near the beam surface, are observed. The corresponding mode structures are of Gaussian shape in the radial direction. The physics of nonlinear saturation and emittance growth will be discussed

  16. Plasma transport in stochastic magnetic field caused by vacuum resonant magnetic perturbations at diverted tokamak edge

    SciTech Connect

    Park, G.; Chang, C. S.; Joseph, I.; Moyer, R. A.

    2010-10-15

    A kinetic transport simulation for the first 4 ms of the vacuum resonant magnetic perturbations (RMPs) application has been performed for the first time in realistic diverted DIII-D tokamak geometry [J. Luxon, Nucl. Fusion 42, 614 (2002)], with the self-consistent evaluation of the radial electric field and the plasma rotation. It is found that, due to the kinetic effects, the stochastic parallel thermal transport is significantly reduced when compared to the standard analytic model [A. B. Rechester and M. N. Rosenbluth, Phys. Rev. Lett. 40, 38 (1978)] and the nonaxisymmetric perpendicular radial particle transport is significantly enhanced from the axisymmetric level. These trends agree with recent experimental result trends [T. E. Evans, R. A. Moyer, K. H. Burrell et al., Nat. Phys. 2, 419 (2006)]. It is also found, as a side product, that an artificial local reduction of the vacuum RMP fields in the vicinity of the magnetic separatrix can bring the kinetic simulation results to a more detailed agreement with experimental plasma profiles.

  17. Field transformations and the classical equation of motion in chiral perturbation theory

    SciTech Connect

    Scherer, S.; Fearing, H.W.

    1995-12-01

    The construction of effective Lagrangians commonly involves the application of the ``classical equation of motion`` to eliminate redundant structures and thus generate the minimal number of independent terms. We investigate this procedure in the framework of chiral perturbation theory with particular emphasis on the new features which appear at {ital O}({ital p}{sup 6}). The use of the ``classical equation of motion`` is interpreted in terms of field transformations. Such an interpretation is crucial if one wants to bring a given Lagrangian into a canonical form with a minimal number of terms. We emphasize that the application of field transformations leads to a modification of the coefficients of higher-order terms as well as eliminating structures, or what is equivalent, expressing certain structures in terms of already known different structures. This will become relevant once one considers the problem of expressing in canonical form a model effective interaction containing terms beyond next-to-leading order, i.e., beyond {ital O}({ital p}{sup 4}). In such circumstances the naive application of the clasical equation of motion to simply drop terms, as is commonly done at lowest order, leads to subtle errors, which we discuss.

  18. Q-colourings of the triangular lattice: exact exponents and conformal field theory

    NASA Astrophysics Data System (ADS)

    Vernier, Eric; Lykke Jacobsen, Jesper; Salas, Jesús

    2016-04-01

    We revisit the problem of Q-colourings of the triangular lattice using a mapping onto an integrable spin-one model, which can be solved exactly using Bethe ansatz techniques. In particular we focus on the low-energy excitations above the eigenlevel g 2, which was shown by Baxter to dominate the transfer matrix spectrum in the Fortuin-Kasteleyn (chromatic polynomial) representation for {Q}0≤slant Q≤slant 4, where {Q}0=3.819 671\\cdots . We argue that g 2 and its scaling levels define a conformally invariant theory, the so-called regime IV, which provides the actual description of the (analytically continued) colouring problem within a much wider range, namely Q\\in (2,4]. The corresponding conformal field theory is identified and the exact critical exponents are derived. We discuss their implications for the phase diagram of the antiferromagnetic triangular-lattice Potts model at non-zero temperature. Finally, we relate our results to recent observations in the field of spin-one anyonic chains.

  19. Logarithmic conformal field theories as limits of ordinary CFTs and some physical applications

    NASA Astrophysics Data System (ADS)

    Cardy, John

    2013-12-01

    We describe an approach to logarithmic conformal field theories as limits of sequences of ordinary conformal field theories with varying central charge c. Logarithmic behaviour arises from degeneracies in the spectrum of scaling dimensions at certain values of c. The theories we consider are all invariant under some internal symmetry group, and logarithmic behaviour occurs when the decomposition of the physical observables into irreducible operators becomes singular. Examples considered are quenched random magnets using the replica formalism, self-avoiding walks as the n → 0 limit of the O(n) model, and percolation as the limit Q → 1 of the Potts model. In these cases we identify logarithmic operators and pay particular attention to how the c → 0 paradox is resolved and how the b-parameter is evaluated. We also show how this approach gives information on logarithmic behaviour in the extended Ising model, uniform spanning trees and the O( - 2) model. Most of our results apply to general dimensionality. We also consider massive logarithmic theories and, in two dimensions, derive sum rules for the effective central charge and the b-parameter.

  20. Shape Dependence of Holographic Rényi Entropy in Conformal Field Theories

    NASA Astrophysics Data System (ADS)

    Dong, Xi

    2016-06-01

    We develop a framework for studying the well-known universal term in the Rényi entropy for an arbitrary entangling region in four-dimensional conformal field theories that are holographically dual to gravitational theories. The shape dependence of the Rényi entropy Sn is described by two coefficients: fb(n ) for traceless extrinsic curvature deformations and fc(n ) for Weyl tensor deformations. We provide the first calculation of the coefficient fb(n ) in interacting theories by relating it to the stress tensor one-point function in a deformed hyperboloid background. The latter is then determined by a straightforward holographic calculation. Our results show that a previous conjecture fb(n )=fc(n ), motivated by surprising evidence from a variety of free field theories and studies of conical defects, fails holographically.

  1. Shape Dependence of Holographic Rényi Entropy in Conformal Field Theories.

    PubMed

    Dong, Xi

    2016-06-24

    We develop a framework for studying the well-known universal term in the Rényi entropy for an arbitrary entangling region in four-dimensional conformal field theories that are holographically dual to gravitational theories. The shape dependence of the Rényi entropy S_{n} is described by two coefficients: f_{b}(n) for traceless extrinsic curvature deformations and f_{c}(n) for Weyl tensor deformations. We provide the first calculation of the coefficient f_{b}(n) in interacting theories by relating it to the stress tensor one-point function in a deformed hyperboloid background. The latter is then determined by a straightforward holographic calculation. Our results show that a previous conjecture f_{b}(n)=f_{c}(n), motivated by surprising evidence from a variety of free field theories and studies of conical defects, fails holographically. PMID:27391713

  2. Geospace Environment Modeling 2008-2009 Challenge: Ground Magnetic Field Perturbations

    NASA Technical Reports Server (NTRS)

    Pulkkinen, A.; Kuznetsova, M.; Ridley, A.; Raeder, J.; Vapirev, A.; Weimer, D.; Weigel, R. S.; Wiltberger, M.; Millward, G.; Rastatter, L.; Hesse, M.; Singer, H. J.; Chulaki, A.

    2011-01-01

    Acquiring quantitative metrics!based knowledge about the performance of various space physics modeling approaches is central for the space weather community. Quantification of the performance helps the users of the modeling products to better understand the capabilities of the models and to choose the approach that best suits their specific needs. Further, metrics!based analyses are important for addressing the differences between various modeling approaches and for measuring and guiding the progress in the field. In this paper, the metrics!based results of the ground magnetic field perturbation part of the Geospace Environment Modeling 2008 2009 Challenge are reported. Predictions made by 14 different models, including an ensemble model, are compared to geomagnetic observatory recordings from 12 different northern hemispheric locations. Five different metrics are used to quantify the model performances for four storm events. It is shown that the ranking of the models is strongly dependent on the type of metric used to evaluate the model performance. None of the models rank near or at the top systematically for all used metrics. Consequently, one cannot pick the absolute winner : the choice for the best model depends on the characteristics of the signal one is interested in. Model performances vary also from event to event. This is particularly clear for root!mean!square difference and utility metric!based analyses. Further, analyses indicate that for some of the models, increasing the global magnetohydrodynamic model spatial resolution and the inclusion of the ring current dynamics improve the models capability to generate more realistic ground magnetic field fluctuations.

  3. Hybrid modelling of near-field coupling onto grounded wire under ultra-short duration perturbation

    NASA Astrophysics Data System (ADS)

    Ravelo, B.; Liu, Y.

    2014-10-01

    A time-frequency (TF) hybrid model (HM) for investigating the interaction between EM near-field (NF) aggression and grounded wire is addressed. The HM is based on the combination of techniques for extracting the EM NF radiated by electronic structures and the calculation of electrical disturbances across the wire due to EM coupling. The computation method is fundamentally inspired from transmission line (TL) theory under EM illumination. The methodology including flow chart interpreting the routine algorithm based on the combination of frequency and time domain approaches is featured. An experimental result showing the EM coupling between patch antenna-wire from 1.5-3.5GHz reveals the efficiency of the HM in frequency domain. The relevance of this HM was illustrated with a structure comprised of 20cm aggressor and 5cm victim I-shaped wires placed above a planar ground plane. The aggressor was excited with 40ns duration perturbation signal. After Matlab implementation of the HM, the disturbance voltages across the extremity of the victim wire were extracted. This simple and fast HM is useful for the EMC engineering during the design and fabrication phases of electrical and electronic systems.

  4. Conformational dynamics and aggregation behavior of piezoelectric diphenylalanine peptides in an external electric field.

    PubMed

    Kelly, Catherine M; Northey, Thomas; Ryan, Kate; Brooks, Bernard R; Kholkin, Andrei L; Rodriguez, Brian J; Buchete, Nicolae-Viorel

    2015-01-01

    Aromatic peptides including diphenylalanine (FF) have the capacity to self-assemble into ordered, biocompatible nanostructures with piezoelectric properties relevant to a variety of biomedical applications. Electric fields are commonly applied to align FF nanotubes, yet little is known about the effect of the electric field on the assembly process. Using all-atom molecular dynamics with explicit water molecules, we examine the response of FF monomers to the application of a constant external electric field over a range of intensities. We probe the aggregation mechanism of FF peptides, and find that the presence of even relatively weak fields can accelerate ordered aggregation, primarily by facilitating the alignment of individual molecular dipole moments. This is modulated by the conformational response of individual FF peptides (e.g., backbone stretching) and by the cooperative alignment of neighboring FF and water molecules. These observations may facilitate future studies on the controlled formation of nanostructured aggregates of piezoelectric peptides and the understanding of their electro-mechanical properties. PMID:25240398

  5. Entanglement negativity after a local quantum quench in conformal field theories

    NASA Astrophysics Data System (ADS)

    Wen, Xueda; Chang, Po-Yao; Ryu, Shinsei

    2015-08-01

    We study the time evolution of the entanglement negativity after a local quantum quench in (1 + 1)-dimensional conformal field theories (CFTs), which we introduce by suddenly joining two initially decoupled CFTs at their end points. We calculate the negativity evolution for both adjacent intervals and disjoint intervals explicitly. For two adjacent intervals, the entanglement negativity grows logarithmically in time right after the quench. After developing a plateau-like feature, the entanglement negativity drops to the ground-state value. For the case of two spatially separated intervals, a light-cone behavior is observed in the negativity evolution; in addition, a long-range entanglement, which is independent of the distance between two intervals, can be created. Our results agree with the heuristic picture that quasiparticles, which carry entanglement, are emitted from the joining point and propagate freely through the system. Our analytical results are confirmed by numerical calculations based on a critical harmonic chain.

  6. The spectral theory of a functional-difference operator in conformal field theory

    NASA Astrophysics Data System (ADS)

    Takhtajan, L. A.; Faddeev, L. D.

    2015-04-01

    We consider the functional-difference operator H=U+U-1+V, where U and V are the Weyl self-adjoint operators satisfying the relation UV=q2VU, q=eπ iτ, τ>0. The operator H has applications in the conformal field theory and representation theory of quantum groups. Using the modular quantum dilogarithm (a q-deformation of the Euler dilogarithm), we define the scattering solution and Jost solutions, derive an explicit formula for the resolvent of the self-adjoint operator H on the Hilbert space L2( R), and prove the eigenfunction expansion theorem. This theorem is a q-deformation of the well-known Kontorovich-Lebedev transform in the theory of special functions. We also present a formulation of the scattering theory for H.

  7. Polysiloxanes: ab initio force field and structural, conformational and thermophysical properties

    NASA Astrophysics Data System (ADS)

    Sun, Huai; Rigby, David

    1997-07-01

    Various levels of ab initio calculation have been performed to determine the optimum strategy for parameterization of the valence parameters of a CFF-type force field for siloxanes and polysiloxanes. Electrostatic nonbond parameters have been determined using scaled electrostatic potential (ESP) charges adjusted for known systematic differences between ab initio and experimental data, while van der Waals nonbond parameters have been determined using a classical approach involving fitting to experimental liquid density and cohesive energy density data measured at atmospheric pressure and a single temperature for a set of four small molecules. Simulations have been performed on molecular crystals, liquids and isolated molecules, yielding results which agree favorably with available experimental data. Properties calculated include unit cell parameters and crystal densities, liquid densities from 303-473 K and 0-1800 bar, dependence of oligomer density and solubility parameters on chain length and temperature, gas-phase geometries and vibrational frequencies, and gas and liquid-phase conformational behavior.

  8. Wave functions of symmetry-protected topological phases from conformal field theories

    NASA Astrophysics Data System (ADS)

    Scaffidi, Thomas; Ringel, Zohar

    2016-03-01

    We propose a method for analyzing two-dimensional symmetry-protected topological (SPT) wave functions using a correspondence with conformal field theories (CFTs) and integrable lattice models. This method generalizes the CFT approach for the fractional quantum Hall effect wherein the wave-function amplitude is written as a many-operator correlator in the CFT. Adopting a bottom-up approach, we start from various known microscopic wave functions of SPTs with discrete symmetries and show how the CFT description emerges at large scale, thereby revealing a deep connection between group cocycles and critical, sometimes integrable, models. We show that the CFT describing the bulk wave function is often also the one describing the entanglement spectrum, but not always. Using a plasma analogy, we also prove the existence of hidden quasi-long-range order for a large class of SPTs. Finally, we show how response to symmetry fluxes is easily described in terms of the CFT.

  9. Analysis of perturbations in the lateral far-field of blue InGaN laser diodes

    NASA Astrophysics Data System (ADS)

    Kopp, F.; Lell, A.; Eichler, C.; Schwarz, U. T.; Strauss, U.

    2013-01-01

    The origin of perturbations in the Gaussian-shaped lateral far-field of blue InGaN laser diodes is explored. Near-field measurements reveal that small stray light intensity peaks beside the ridge waveguide exist. In order to prove quantitatively the impact of this stray light on the far field, an exemplary beam propagation method simulation is performed. Moreover, laser cuts as a chip technological process to block stray light from the out-couple facet are presented. These laser cuts result in a significant improvement of the lateral far-field.

  10. A perturbation theory study of electron vortices in electromagnetic fields: the case of infinitely long line charge and magnetic dipole.

    PubMed

    Xie, L; Wang, P; Pan, X Q

    2014-08-01

    The novel discovery of electron vortices carrying quantized orbital angular momentum motivated intensive research of their basic properties as well as applications, e.g. structural characterization of magnetic materials. In this paper, the fundamental interactions of electron vortices within infinitely long atomic-column-like electromagnetic fields are studied based on the relativistically corrected Pauli-Schrödinger equation and the perturbation theory. The relative strengths of three fundamental interactions, i.e. the electron-electric potential interaction, the electron-magnetic potential/field interaction and the spin-orbit coupling are discussed. The results suggest that the perturbation energies of the last two interactions are in an order of 10(3)-10(4) smaller than that of the first one for electron vortices. In addition, it is also found that the strengths of these interactions are strongly dependant on the spatial distributions of the electromagnetic field as well as the electron vortices. PMID:24690540

  11. Compact optical gimbal as a conformal beam director for large field-of-regard lasercom applications

    NASA Astrophysics Data System (ADS)

    Kesner, Jessica E.; Hinrichs, Keith M.; Narkewich, Lawrence E.; Stephens, Timothy

    2015-03-01

    Laser communication offers advantages over traditional RF communication, including reduced size, weight, and power, higher data rates, and resistance to jamming. However, existing beam directors used for large field-of-regard lasercom terminals have limitations. Traditional gimbals require either domes or large conformal windows to achieve large fields of regard. Risley prism-based beam directors have temperature- and wavelength-dependent pointing necessitating tight temperature control and pointing correction techniques. Other methods, like liquid crystal optical phased array beam directors, have low transmittance and low technology readiness levels (TRLs). This paper presents a detailed design and preliminary performance results of a prototype Compact Optical Gimbal (COG) beam director that provides a 2 inch beam over a +/- 65o field-of-regard through a small (~12 inch) flat window. The COG differs from the traditional gimbal in that it includes three-axis steering with off-axis elevation and dither control, and a folded refractive afocal telescope incorporated into the body of the gimbal to minimize size. The COG's optical system does not have the pointing challenges characteristic of Risley prisms, and it utilizes high TRL components, including many commercial off-theshelf parts, to simplify implementation. The compact size and performance support a variety of beam steering applications and platforms.

  12. Conformational Entropy Mechanism for Periodic Motion of DNA under Constant-Field Gel Electrophoresis

    NASA Astrophysics Data System (ADS)

    Azuma, Ryuzo; Takayama, Hajime

    2006-06-01

    Entropic elasticity of a single charged polymer undergoing gel electrophoresis is a fundamental theme of polymer statistical physics since the discovery of “periodic” behavior in constant field gel electrophoresis (CFGE). In the present work we address the problem numerically by two steps. In the first step, we carry out Brownian dynamics (BD) simulations on CFGE by solving semi-microscopic Langevin equations of a polymer consisting of beads separated by a mean distance much smaller than the Kuhn length. Results are analyzed based on coarse-graining over the Kuhn length scale. We show the averaged elongation-contraction motion involves asymmetric V-shaped configurations whose shorter arm length depends on the field and the temperature consistently with what is expected when the BD chain is described by the freely-jointed chain (FJC) model with a suitable Kuhn length. To our knowledge, this is the first numerical confirmation of the FJC model itself from a submicroscopic description of polymer motion. The saturation of chain mobility in high fields agrees well with the nonlinear dependence of this shorter arm length on the field. In the second step, we discuss the periodic elongation-contraction motion of the coarse-grained chain by such a simplified model as a one-dimensional chain consisting of beads, elastic strings, and obstacles. The results from these two chain models indicate that the periodic elongation-contraction motion of DNA under CFGE is self-organized by a balance between the field force and the conformational entropic force.

  13. Active control of Type-I Edge-Localized Modes with n=1 Perturbation Fields in the JET Tokamak

    SciTech Connect

    Liang, Y.; Koslowski, R.; Thomas, P.; Nardon, E.; Alper, B.; Baranov, Y.; Beurskens, M.; Bigi, M.; Crombe, K.; de la Luna, E.; De Vries, P.; Fundamenski, W.; Rachlew, Elisabeth G; Zimmermann, O.

    2007-06-01

    Type-I edge-localized modes (ELMs) have been mitigated at the JET tokamak using a static external n=1 perturbation field generated by four error field correction coils located far from the plasma. During the application of the n=1 field the ELM frequency increased by a factor of 4 and the amplitude of the D signal decreased. The energy loss per ELM normalized to the total stored energy, W/W, dropped to values below 2%. Transport analyses shows no or only a moderate (up to 20%) degradation of energy confinement time during the ELM mitigation phase.

  14. Quartic AdS interactions in higher-spin gravity from Conformal Field Theory

    NASA Astrophysics Data System (ADS)

    Bekaert, X.; Erdmenger, J.; Ponomarev, D.; Sleight, C.

    2015-11-01

    Clarifying the locality properties of higher-spin gravity is a pressing task, but notoriously difficult due to the absence of a weakly-coupled flat regime. The simplest non-trivial case where this question can be addressed is the quartic self-interaction of the AdS scalar field present in the higher-spin multiplet. We investigate this issue in the context of the holographic duality between the minimal bosonic higher-spin theory on AdS4 and the free O( N) vector model in three dimensions. In particular, we determine the exact explicit form of the derivative expansion of the bulk scalar quartic vertex. The quartic vertex is obtained from the field theory four-point function of the operator dual to the bulk scalar, by making use of our previous results for the Witten diagrams of higher-spin exchanges. This is facilitated by establishing the conformal block expansions of both the boundary four-point function and the dual bulk Witten diagram amplitudes. We show that the vertex we find satisfies a generalised notion of locality.

  15. Ionospheric Irregularities at High Latitudes During Geomagnetic Storms and Substorms: Simultaneous Observations of Magnetic Field Perturbations and GPS Scintillations

    NASA Astrophysics Data System (ADS)

    Kim, H.; Deshpande, K.; Clauer, C. R.; Bust, G. S.; Crowley, G.; Humphreys, T. E.; Kim, L.; Lessard, M.; Weatherwax, A. T.; Zachariah, T. P.

    2012-12-01

    Plasma instability in the ionosphere is often observed as disturbance and distortion of the amplitude and phase of radio signals, which are known as ionospheric scintillations. High-latitude ionospheric plasma, closely connected to solar wind and magnetospheric dynamics, produce very dynamic and short-lived GPS scintillations, making it challenging to characterize them. This study reports simultaneous observations of geomagnetic pulsations and GPS signal scintillations during geomagnetic storms and substorms using a newly designed Autonomous Adaptive Low-Power Instrument Platform (AAL-PIP) installed at the South Pole. A statistical investigation of the AAL-PIP data recorded from January through May 2012 is presented to study local time distribution of scintillation events and a correlation between GPS scintillation and magnetic field perturbations. This report discusses a possible connection between magnetic field perturbations associated with the ionospheric currents and the creation of plasma instability by examining relative contribution of storm/substorm activity to ionospheric irregularities.

  16. Effect of n = 3 perturbation field amplitudes below the ELM triggering threshold on edge and SOL transport in NSTX

    DOE PAGESBeta

    J. M. Canik; Lore, J. D.; Ahn, J. -W.; Bortolon, A.; Fredrickson, E. D.; Jaworski, M. A.; Kramer, G. J.; Maingi, R.; McLean, A. G.; Scotti, F.; et al

    2013-01-12

    Here, the pulsed application of n = 3 magnetic perturbation fields with amplitudes below that which triggers ELMs results in distinct, transient responses observable on several edge and divertor diagnostics in NSTX. We refer to these responses as Sub-Threshold Edge Perturbations (STEPs). An analysis of edge measurements suggests that STEPs result in increased transport in the plasma edge and scrape-off layer, which leads to augmentation of the intrinsic strike point splitting due to error fields, i.e., an intensification of the helical divertor footprint flux pattern. These effects are much smaller in magnitude than those of triggered ELMs, and are observedmore » for the duration of the field perturbation measured internal to the vacuum vessel. In addition, STEPs are correlated with changes to the MHD activity, along with transient reductions in the neutron production rate. Ideally the STEPs could be used to provide density control and prevent impurity accumulation, in the same manner that on-demand ELM triggering is used on NSTX, without the impulsive divertor fluxes and potential for damage to plasma facing components associated with ELMs.« less

  17. A full-field perturbation approach to scattering and reverberation in range-dependent environments with rough interfaces.

    PubMed

    Ivakin, Anatoliy N

    2016-07-01

    A perturbation approach to roughness scattering and reverberation in range-dependent environments is developed treating each interface as a superposition of a smooth reference interface, which may include large-scale deterministic features (such as bathymetry changes), and small compared to the acoustic wavelength vertical deviations from this interface that are considered as random roughness perturbations. The reference interface is assumed to be smooth enough to allow analytic or numerical solution for the field in the vicinity of this interface that can then be used in perturbation theory. Expressions for both the reverberation field and average reverberation intensity in a general case of an arbitrary number of rough interfaces are obtained in a form convenient for numerical simulations. In the case of long-range ocean reverberation, several approximations for these expressions are developed, relevant to various environmental scenarios and different types of interfaces: sea-surface, water-sediment interface, buried sediment interfaces, and bottom basement. The results are presented in a simple form and provide a direct relationship of the reverberation intensity with three critical characteristics defined at each interface: (1) local spectrum of roughness, (2) local contrast of acoustic parameters, and (3) two-way full-field transmission intensity calculated taking into account only large-scale changes of the environment. PMID:27475187

  18. Evaluation of the toroidal torque driven by external non-resonant non-axisymmetric magnetic field perturbations in a tokamak

    NASA Astrophysics Data System (ADS)

    Kasilov, Sergei V.; Kernbichler, Winfried; Martitsch, Andreas F.; Maassberg, Henning; Heyn, Martin F.

    2014-09-01

    The toroidal torque driven by external non-resonant magnetic perturbations (neoclassical toroidal viscosity) is an important momentum source affecting the toroidal plasma rotation in tokamaks. The well-known force-flux relation directly links this torque to the non-ambipolar neoclassical particle fluxes arising due to the violation of the toroidal symmetry of the magnetic field. Here, a quasilinear approach for the numerical computation of these fluxes is described, which reduces the dimension of a standard neoclassical transport problem by one without model simplifications of the linearized drift kinetic equation. The only limiting condition is that the non-axisymmetric perturbation field is small enough such that the effect of the perturbation field on particle motion within the flux surface is negligible. Therefore, in addition to most of the transport regimes described by the banana (bounce averaged) kinetic equation also such regimes as, e.g., ripple-plateau and resonant diffusion regimes are naturally included in this approach. Based on this approach, a quasilinear version of the code NEO-2 [W. Kernbichler et al., Plasma Fusion Res. 3, S1061 (2008).] has been developed and benchmarked against a few analytical and numerical models. Results from NEO-2 stay in good agreement with results from these models in their pertinent range of validity.

  19. Evaluation of the toroidal torque driven by external non-resonant non-axisymmetric magnetic field perturbations in a tokamak

    SciTech Connect

    Kasilov, Sergei V.; Kernbichler, Winfried; Martitsch, Andreas F.; Heyn, Martin F.; Maassberg, Henning

    2014-09-15

    The toroidal torque driven by external non-resonant magnetic perturbations (neoclassical toroidal viscosity) is an important momentum source affecting the toroidal plasma rotation in tokamaks. The well-known force-flux relation directly links this torque to the non-ambipolar neoclassical particle fluxes arising due to the violation of the toroidal symmetry of the magnetic field. Here, a quasilinear approach for the numerical computation of these fluxes is described, which reduces the dimension of a standard neoclassical transport problem by one without model simplifications of the linearized drift kinetic equation. The only limiting condition is that the non-axisymmetric perturbation field is small enough such that the effect of the perturbation field on particle motion within the flux surface is negligible. Therefore, in addition to most of the transport regimes described by the banana (bounce averaged) kinetic equation also such regimes as, e.g., ripple-plateau and resonant diffusion regimes are naturally included in this approach. Based on this approach, a quasilinear version of the code NEO-2 [W. Kernbichler et al., Plasma Fusion Res. 3, S1061 (2008).] has been developed and benchmarked against a few analytical and numerical models. Results from NEO-2 stay in good agreement with results from these models in their pertinent range of validity.

  20. Spontaneous breaking of conformal invariance, solitons, and gravitational waves in theories of conformally invariant gravitation

    NASA Astrophysics Data System (ADS)

    Bouchami, Jihène; Paranjape, M. B.

    2008-08-01

    We study conformal gravity as an alternative theory of gravitation. For conformal gravity to be phenomenologically viable requires that the conformal symmetry is not manifest at the energy scales of the other known physical forces. Hence we are required to find a mechanism for the spontaneous breaking of conformal invariance. In this paper we study the possibility that conformal invariance is spontaneously broken due to interactions with conformally coupled matter fields. The vacuum of the theory admits conformally noninvariant solutions corresponding to maximally symmetric space-times and variants thereof. These are either de Sitter space-time or anti-de Sitter space-time in the full four space-time dimensions and we find new solutions corresponding to maximal symmetry restricted to a lower dimensional subspace. We also consider normalizable, linearized gravitational perturbations around the anti-de Sitter background. We show to second order, that these gravitational fluctuations carry zero energy momentum. Finally we also show the possibility of domain wall solitons interpolating between the ground states of spontaneously broken conformal symmetry that we have found. These solitons necessarily require the vanishing of the scalar field. This offers a way of eschewing the recent suggestion and its consequences [E. Flanagan, Phys. Rev. D 74, 023002 (2006).PRVDAQ0556-282110.1103/PhysRevD.74.023002] that the conformal symmetry could be quarantined to a sterile sector of the theory by choosing an appropriate field redefinition.

  1. Perturbations of black p-branes

    SciTech Connect

    Abdalla, Elcio; Fernandez Piedra, Owen Pavel; Oliveira, Jeferson de; Molina, C.

    2010-03-15

    We consider black p-brane solutions of the low-energy string action, computing scalar perturbations. Using standard methods, we derive the wave equations obeyed by the perturbations and treat them analytically and numerically. We have found that tensorial perturbations obtained via a gauge-invariant formalism leads to the same results as scalar perturbations. No instability has been found. Asymptotically, these solutions typically reduce to a AdS{sub (p+2)}xS{sup (8-p)} space which, in the framework of Maldacena's conjecture, can be regarded as a gravitational dual to a conformal field theory defined in a (p+1)-dimensional flat space-time. The results presented open the possibility of a better understanding the AdS/CFT correspondence, as originally formulated in terms of the relation among brane structures and gauge theories.

  2. Effect of local perturbations of the geomagnetic field on cosmic ray cutoff rigidities at Jungfraujoch and Kiel

    SciTech Connect

    Flueckiger, E.O.; Smart, D.F.; Shea, M.A.

    1983-09-01

    We have investigated the effect of local perturbations of the geomagnetic field on the vertical cosmic ray cutoff rigidities at Jungfraujoch and Kiel as representative mid-latitude neutron monitor stations. The main, effective, and Stoermer vertical cutoff rigidities and their changes were determined by utilizing the trajectory-tracing technique in a magnetic field which is modeled as a simple dipole field to which the disturbance field is superposed. It was found that the cosmic ray cutoff rigidities are most sensitive to variations of the z component of the geomagnetic field at geomagnetic latitudes -20/sup 0/<..lambda..<+30/sup 0/ and at longitudes within 90/sup 0/ to the east of these northern hemisphere stations. Furthermore, cutoff rigidity variations at Kiel are predominantly due to changes of the geomagnetic field within geocentric distances 2.5R/sub E/perturbations is given explicitly. The results are discussed with respect to the theory by Treiman (1953) describing the effect of a ring current on cosmic ray cutoff rigidities. It is also shown that for the analysis of the characteristic properties of the correlation between cutoff rigidity variations and specific geomagnetic perturbations the rigidity corresponding to the first ''discontinuity band'' of the rigidity spectrum is an extremely useful parameter.

  3. Conformational properties, torsional potential, and vibrational force field for methacryloyl fluoride - An ab initio investigation

    NASA Technical Reports Server (NTRS)

    Laskowski, B. C.; Jaffe, R. L.; Komornicki, A.

    1985-01-01

    The structure, torsional potentials, vibrational spectra, and harmonic force fields for s-cis and s-trans isomers of methacryloyl fluoride are examined to understand the conformational properties of the molecules and their relationship to macroscopic polymer properties. The structure is found to be in good agreement with experiment. It is shown by calculations that the energy difference between the cis and the transisomers is less than 1 kcal/mol at both the split valence and the split valence polarized levels, with the trans form favored. Analysis of the torsional potentials indicates that a rigid rotor model provides a reasonable description of the motion of the COF group in the molecule. The torsional barrier to interconvert the s-trans to the s-cis form is found to be 7.0 kcal/mol. A fit of the data to a three-term Fourier series shows that it is possible to reproduce the experimentally derived barrier, even though a direct determination indicates that the barrier is higher.

  4. Constraining conformal field theories with a higher spin symmetry in d > 3 dimensions

    NASA Astrophysics Data System (ADS)

    Alba, Vasyl; Diab, Kenan

    2016-03-01

    We study unitary conformal field theories with a unique stress tensor and at least one higher-spin conserved current in d > 3 dimensions. We prove that every such theory contains an infinite number of higher-spin conserved currents of arbitrarily high spin, and that Ward identities generated by the conserved charges of these currents imply that the correlators of the stress tensor and the conserved currents of the theory must coincide with one of the following three possibilities: a) a theory of n free bosons (for some integer n), b) a theory of n free fermions, or c) a theory of nd-2/2 -forms. For d even, all three structures exist, but for d odd, it may be the case that the third structure (c) does not; if it does exist, it is unclear what theory, if any, realizes it. This is a generalization of the result proved in three dimensions by Maldacena and Zhiboedov [1]. This paper supersedes the previous paper by the authors [2].

  5. Combined probes of X-ray scattering and optical spectroscopy reveal how global conformational change is temporally and spatially linked to local structural perturbation in photoactive yellow protein.

    PubMed

    Kim, Tae Wu; Yang, Cheolhee; Kim, Youngmin; Kim, Jong Goo; Kim, Jeongho; Jung, Yang Ouk; Jun, Sunhong; Lee, Sang Jin; Park, Sungjun; Kosheleva, Irina; Henning, Robert; van Thor, Jasper J; Ihee, Hyotcherl

    2016-03-23

    Real-time probing of structural transitions of a photoactive protein is challenging owing to the lack of a universal time-resolved technique that can probe the changes in both global conformation and light-absorbing chromophores of the protein. In this work, we combine time-resolved X-ray solution scattering (TRXSS) and transient absorption (TA) spectroscopy to investigate how the global conformational changes involved in the photoinduced signal transduction of photoactive yellow protein (PYP) is temporally and spatially related to the local structural change around the light-absorbing chromophore. In particular, we examine the role of internal proton transfer in developing a signaling state of PYP by employing its E46Q mutant (E46Q-PYP), where the internal proton transfer is inhibited by the replacement of a proton donor. The comparison of TRXSS and TA spectroscopy data directly reveals that the global conformational change of the protein, which is probed by TRXSS, is temporally delayed by tens of microseconds from the local structural change of the chromophore, which is probed by TA spectroscopy. The molecular shape of the signaling state reconstructed from the TRXSS curves directly visualizes the three-dimensional conformations of protein intermediates and reveals that the smaller structural change in E46Q-PYP than in wild-type PYP suggested by previous studies is manifested in terms of much smaller protrusion, confirming that the signaling state of E46Q-PYP is only partially developed compared with that of wild-type PYP. This finding provides direct evidence of how the environmental change in the vicinity of the chromophore alters the conformational change of the entire protein matrix. PMID:26960811

  6. Three-Dimensional Dose Optimization for Noncoplanar Treatment Planning with Conformal Fields.

    NASA Astrophysics Data System (ADS)

    Ma, Ying-Chang L.

    1990-01-01

    Recent advances in imaging techniques, especially three dimensional reconstruction of CT images, have made precision tumor localization feasible. These imaging techniques along with developments in computer controlled radiation treatment machines have provided an important thrust in developing better techniques for cancer treatment. This often requires a complex noncoplanar beam arrangements and elaborate treatment planning, which, unfortunately, are time consuming, costly and dependent on operator expertise and experience. A reliable operator-independent dose optimization tool is therefore desirable, especially for 3D treatment planning. In this dissertation, several approaches (linear programming, quadratic programming, and direct search methods) of computer optimization using various criteria including least sire fitting on the 90% isodose to target periphery, dose uniformity, and integral dose are presented. All of these methods are subject to restrictions on the upper limit of the dose to critical organs. In the quadratic programming approach, Kuhn-Tucker theory was employed to convert the quadratic problem into one which permits application of the very powerful, revised simplex method. Several examples are used to analyze the effectiveness of these dose optimization approaches. The studies show that the quadratic programming approach with the criteria of least square fitting and critical organ constraints is superior in efficiency for dose optimization in 3D treatment planning, particularly for cases with a large number of beams. Use of least square fitting allows one to deduce optimized plans for irregularly shaped targets by employing a multi-isocentric technique. Our studies also illustrate the advantages of using irregular conformal fields, optimized beam energy, and noncoplanar beam arrangements in contrast to the conventional treatment which uses a symmetrical rectangular collimator, fixed beam energy, and coplanar beam arrangements. Optimized plans can

  7. Field-Theoretical Approach to Many-Body Perturbation Theory: Combining MBPT and QED

    SciTech Connect

    Lindgren, Ingvar; Salomonson, Sten; Hedendahl, Daniel

    2007-12-26

    Many-Body Perturbation Theory (MBPT) is today highly developed. The electron correlation of atomic and molecular systems can be evaluated to essentially all orders of perturbation theory--also relativistically (RMBPT)--by means of techniques of Coupled-Cluster type. When high accuracy is needed, effects beyond RMBPT will enter, i.e., effects of retarded Breit interaction and of radiative effects (Lamb shift), effects normally referred to as QED effects. These effects can be evaluated by means of special techniques, like S-matrix formulation, which cannot simultaneously treat electron correlation. It would for many applications be desirable to have access to a numerical technique, where effects of electron correlation and of QED could be treated on the same footing. Such a technique is presently being developed and gradually implemented at our laboratory. Some numerical results will be given.

  8. Collapse of small-scale density perturbations during preheating in single field inflation

    SciTech Connect

    Jedamzik, Karsten; Lemoine, Martin; Martin, Jérôme E-mail: lemoine@iap.fr

    2010-09-01

    After cosmic inflation and before the transition to radiation domination, the cosmic energy density may have been dominated during an extended period by an oscillating massive scalar condensate. We show that during this period, sub-Hubble scale perturbations are subject to a metric preheating instability in the narrow resonance regime. We analyze in detail both, quadratic and quartic potentials. The instability leads to the growth of density perturbations which in many cases become non-linear already before the beginning of a radiation dominated Universe. This is particularly the case when requiring a phenomenologically preferred low reheat temperature. These early structures may lead to the emission of gravitational waves and the production of primordial black holes.

  9. Excitation of stable Alfven eigenmodes by application of alternating magnetic field perturbations in the Compact Helical System

    SciTech Connect

    Ito, T.; Toi, K.; Isobe, M.; Nagaoka, K.; Takeuchi, M.; Akiyama, T.; Matsuoka, K.; Minami, T.; Nishimura, S.; Okamura, S.; Shimizu, A.; Suzuki, C.; Yoshimura, Y.; Takahashi, C.; Matsunaga, G.

    2009-09-15

    Stable toroidicity-induced Alfven eigenmodes (TAEs) with low toroidal mode number (n=1 and n=2) were excited by application of alternating magnetic field perturbations generated with a set of electrodes inserted into the edge region of neutral beam injection heated plasmas on the Compact Helical System [K. Nishimura, K. Matsuoka, M. Fujiwara et al., Fusion Technol. 17, 86 (1990)]. The gap locations of TAEs excited by the electrodes are in the plasma peripheral region of {rho}>0.7 ({rho} is the normalized minor radius) where energetic ion drive is negligibly small, while some AEs are excited by energetic ions in the plasma core region of {rho}<0.4. The damping rate of these stable TAEs derived from plasma responses to applied perturbations is fairly large, that is, {approx}9% to {approx}12% of the angular eigenfrequency. This large damping rate is thought to be dominantly caused by continuum damping and radiative damping.

  10. Research in string theory and two dimensional conformal field theory: Progress report for period April 1, 1988--March 31, 1989

    SciTech Connect

    Friedan, D.H.; Martinec, E.J.; Shenker, S.H.

    1988-12-01

    The present contract supported work by Daniel H. Frieden, Emil J, Martinec and Stephen H. Shenker (principal investigators), Research Associates, and graduate students in theoretical physics at the University of Chicago. Research has been conducted in areas of string theory and two dimensional conformal and superconformal field theory. The ultimate objectives have been: to expose the fundamental structure of string theory so as to eventually make possible effective nonperturbative calculations and thus a comparison of sting theory with experiment, the complete classification of all two dimensional conformal and superconformal field theories thus giving a complete description of all classical ground states of string and of all possible two (and 1 + 1) dimensional critical phenomena, and the development of methods to describe, construct and solve two dimensional field theories. Work has also been done on skyrmion and strong interaction physics.

  11. Lars Onsager Prize Talk: 1+1d conformal field theories as natural languages for asymptotically large-scale quantum computing

    NASA Astrophysics Data System (ADS)

    Friedan, Daniel

    2010-03-01

    An abstract argument is offered that the ideal physical systems for asymptotically large-scale quantum computers are near-critical quantum circuits, critical in the bulk, whose bulk universality classes are described by 1+1d conformal field theories. One in particular -- the Monster conformal field theory -- is especially ideal, because all of its bulk couplings are irrelevant.

  12. Perturbation Theory at Eight Loops: Novel Structures and the Breakdown of Manifest Conformality in N =4 Supersymmetric Yang-Mills Theory

    NASA Astrophysics Data System (ADS)

    Bourjaily, Jacob L.; Heslop, Paul; Tran, Vuong-Viet

    2016-05-01

    We use the soft-collinear bootstrap to construct the 8-loop integrand for the 4-point amplitude and 4-stress-tensor correlation function in planar maximally supersymmetric Yang-Mills theory. Both have a unique representation in terms of planar, conformal integrands grouped according to a hidden symmetry discovered for correlation functions. The answer we find exposes a fundamental tension between manifest locality and planarity with manifest conformality not seen at lower loops. For the first time, the integrand must include terms that are finite even on-shell and terms that are divergent even off-shell (so-called pseudoconformal integrals). We describe these novelties and their consequences in this Letter, and we make the full correlator and amplitude available as part of the Supplemental Material.

  13. Perturbation Theory at Eight Loops: Novel Structures and the Breakdown of Manifest Conformality in N=4 Supersymmetric Yang-Mills Theory.

    PubMed

    Bourjaily, Jacob L; Heslop, Paul; Tran, Vuong-Viet

    2016-05-13

    We use the soft-collinear bootstrap to construct the 8-loop integrand for the 4-point amplitude and 4-stress-tensor correlation function in planar maximally supersymmetric Yang-Mills theory. Both have a unique representation in terms of planar, conformal integrands grouped according to a hidden symmetry discovered for correlation functions. The answer we find exposes a fundamental tension between manifest locality and planarity with manifest conformality not seen at lower loops. For the first time, the integrand must include terms that are finite even on-shell and terms that are divergent even off-shell (so-called pseudoconformal integrals). We describe these novelties and their consequences in this Letter, and we make the full correlator and amplitude available as part of the Supplemental Material. PMID:27232016

  14. The light asymptotic limit of conformal blocks in Toda field theory

    NASA Astrophysics Data System (ADS)

    Poghosyan, Hasmik; Poghossian, Rubik; Sarkissian, Gor

    2016-05-01

    We compute the light asymptotic limit of A n-1 Toda conformal blocks by using the AGT correspondence. We show that for certain class of CFT blocks the corresponding Nekrasov partition functions in this limit are simplified drastically being represented as a sum of a restricted class of Young diagrams. In the particular case of A 2 Toda we also compute the corresponding conformal blocks using conventional CFT techniques finding a perfect agreement with the results obtained from the Nekrasov partition functions.

  15. Short-ranged interaction effects on Z2 topological phase transitions: The perturbative mean-field method

    NASA Astrophysics Data System (ADS)

    Lai, Hsin-Hua; Hung, Hsiang-Hsuan

    2015-02-01

    Time-reversal symmetric topological insulator (TI) is a novel state of matter that a bulk-insulating state carries dissipationless spin transport along the surfaces, embedded by the Z2 topological invariant. In the noninteracting limit, this exotic state has been intensively studied and explored with realistic systems, such as HgTe/(Hg, Cd)Te quantum wells. On the other hand, electronic correlation plays a significant role in many solid-state systems, which further influences topological properties and triggers topological phase transitions. Yet an interacting TI is still an elusive subject and most related analyses rely on the mean-field approximation and numerical simulations. Among the approaches, the mean-field approximation fails to predict the topological phase transition, in particular at intermediate interaction strength without spontaneously breaking symmetry. In this paper, we develop an analytical approach based on a combined perturbative and self-consistent mean-field treatment of interactions that is capable of capturing topological phase transitions beyond either method when used independently. As an illustration of the method, we study the effects of short-ranged interactions on the Z2 TI phase, also known as the quantum spin Hall (QSH) phase, in three generalized versions of the Kane-Mele (KM) model at half-filling on the honeycomb lattice. The results are in excellent agreement with quantum Monte Carlo (QMC) calculations on the same model and cannot be reproduced by either a perturbative treatment or a self-consistent mean-field treatment of the interactions. Our analytical approach helps to clarify how the symmetries of the one-body terms of the Hamiltonian determine whether interactions tend to stabilize or destabilize a topological phase. Moreover, our method should be applicable to a wide class of models where topological transitions due to interactions are in principle possible, but are not correctly predicted by either perturbative or self

  16. Hot conformal gauge theories

    NASA Astrophysics Data System (ADS)

    Mojaza, Matin; Pica, Claudio; Sannino, Francesco

    2010-12-01

    We compute the nonzero temperature free energy up to the order g6ln⁡(1/g) in the coupling constant for vectorlike SU(N) gauge theories featuring matter transforming according to different representations of the underlying gauge group. The number of matter fields, i.e. flavors, is arranged in such a way that the theory develops a perturbative stable infrared fixed point at zero temperature. Because of large distance conformality we trade the coupling constant with its fixed point value and define a reduced free energy which depends only on the number of flavors, colors, and matter representation. We show that the reduced free energy changes sign, at the second, fifth, and sixth order in the coupling, when decreasing the number of flavors from the upper end of the conformal window. If the change in sign is interpreted as a signal of an instability of the system then we infer a critical number of flavors. Surprisingly this number, if computed to the order g2, agrees with previous predictions for the lower boundary of the conformal window for nonsupersymmetric gauge theories. The higher order results tend to predict a higher number of critical flavors. These are universal properties, i.e. they are independent of the specific matter representation.

  17. Local conformal-invariance of the wave equation for finite-component fields. I. The conditions for invariance, and fully-reducible fields

    NASA Astrophysics Data System (ADS)

    Bracken, A. J.; Jessup, Barry

    1982-10-01

    The conditions for local conformal-invariance of the wave equation are obtained for finite-component fields, of Types Ia and Ib [in the terminology of Mack and Salam, Ann. Phys. 53, 174 (1969).] These conditions generate a set of locally invariant free massless field equations and restrict the relevant representation of the Lie algebra [(k4⊕d)⊕sl(2,C)] in the index space of the field to belong to a certain class. Those fully-reducible representations which are in this class are described in full. The corresponding Type Ia field equations include only the massless scalar field equation, neutrino equations, Maxwell's equations, and the Bargmann-Wigner equations for massless fields of arbitrary helicity, and no others. In particular, it is confirmed [Bracken, Lett. Nuovo Cimento 2, 574 (1971)] that not all Poincaré-invariant sets of massless Type Ia field equations are conformal-invariant, contrary to some often-quoted results of McLennan [Nuovo Cimento 3, 1360 (1956)], which are shown to be invalid. It is also shown that in the case of a potential, the wave equation is never conformal-invariant in the strong sense (excluding gauge transformations).

  18. Effective field theory, three-loop perturbative expansion, and their experimental implications in graphene many-body effects

    NASA Astrophysics Data System (ADS)

    Barnes, Edwin; Hwang, E. H.; Throckmorton, R. E.; Das Sarma, S.

    2014-06-01

    Many-body electron-electron interaction effects are theoretically considered in monolayer graphene from a continuum effective field-theoretic perspective by going beyond the standard leading-order single-loop perturbative renormalization group (RG) analysis. Given that the effective (bare) coupling constant (i.e., the fine structure constant) in graphene is of order unity, which is neither small to justify a perturbative expansion nor large enough for strong-coupling theories to be applicable, the problem is a difficult one, with some similarity to (2+1)-dimensional strong-coupling quantum electrodynamics (QED). In this work, we take a systematic and comprehensive analytical approach in theoretically studying graphene many-body effects, primarily at the Dirac point (i.e., in undoped, intrinsic graphene), by going up to three loops in the diagrammatic expansion to both ascertain the validity of a perturbative expansion in the coupling constant and to develop a RG theory that can be used to estimate the actual quantitative renormalization effect to higher-order accuracy. Electron-electron interactions are expected to play an important role in intrinsic graphene due to the absence of screening at the Dirac (charge neutrality) point, potentially leading to strong deviations from the Fermi-liquid description around the charge neutrality point where the graphene Fermi velocity should manifest an ultraviolet logarithmic divergence because of the linear band dispersion. While no direct signatures for non-Fermi-liquid behavior at the Dirac point have yet been observed experimentally, there is ample evidence for the interaction-induced renormalization of the graphene velocity as the Dirac point is approached by lowering the carrier density. We provide a critical comparison between theory and experiment, using both higher-order diagrammatic and random phase approximation (i.e., infinite-order bubble diagrams) calculations, emphasizing future directions for a deeper

  19. Rotation dependence of a phase delay between plasma edge electron density and temperature fields due to a fast rotating, resonant magnetic perturbation field

    SciTech Connect

    Stoschus, H.; Schmitz, O.; Frerichs, H.; Unterberg, B.; Abdullaev, S. S.; Clever, M.; Coenen, J. W.; Kruezi, U.; Schega, D.; Samm, U.; Jakubowski, M. W.

    2010-06-15

    Measurements of the plasma edge electron density n{sub e} and temperature T{sub e} fields during application of a fast rotating, resonant magnetic perturbation (RMP) field show a characteristic modulation of both, n{sub e} and T{sub e} coherent to the rotation frequency of the RMP field. A phase delay PHI between the n{sub e}(t) and T{sub e}(t) waveforms is observed and it is demonstrated that this phase delay PHI is a function of the radius with PHI(r) depending on the relative rotation of the RMP field and the toroidal plasma rotation. This provides for the first time direct experimental evidence for a rotation dependent damping of the external RMP field in the edge layer of a resistive high-temperature plasma which breaks down at low rotation and high resonant field amplitudes.

  20. Conformational and Dynamic Properties of Poly(ethylene oxide) in an Ionic Liquid: Development and Implementation of a First-Principles Force Field.

    PubMed

    McDaniel, Jesse G; Choi, Eunsong; Son, Chang-Yun; Schmidt, J R; Yethiraj, Arun

    2016-01-14

    The conformational properties of polymers in ionic liquids are of fundamental interest but not well understood. Atomistic and coarse-grained molecular models predict qualitatively different results for the scaling of chain size with molecular weight, and experiments on dilute solutions are not available. In this work, we develop a first-principles force field for poly(ethylene oxide) (PEO) in the ionic liquid 1-butyl 3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) using symmetry adapted perturbation theory (SAPT). At temperatures above 400 K, simulations employing both the SAPT and OPLS-AA force fields predict that PEO displays ideal chain behavior, in contrast to previous simulations at lower temperature. We therefore argue that the system shows a transition from extended to more compact configurations as the temperature is increased from room temperature to the experimental lower critical solution temperature. Although polarization is shown to be important, its implicit inclusion in the OPLS-AA force is sufficient to describe the structure and energetics of the mixture. The simulations emphasize the difference between ionic liquids from typical solvents for polymers. PMID:26690901

  1. [Research in two-dimensional critical phenomena and conformal field theory]. [Rutgers, The State Univ. , New Brunswick, New Jersey

    SciTech Connect

    Not Available

    1990-01-01

    A very theoretical description is given of research in two- dimensional critical phenomena and conformal field theory. Major progress is reported in the field of fluctuating two-dimensional surfaces. A discretized representation of fluctuating geometry is used where surfaces are represented by triangulations; continuum surfaces are recovered by taking the size of the triangles to zero. One of the central goals of the theory of critical phenomena is to find all possible universality classes of n-dimensional critical phenomena; this goal has been translated into the problem of clasifying all possible scale-invariant euclidean quantum field theories. (RWR)

  2. Analysis of the dynamic response of a supersonic inlet to flow-field perturbations upstream of the normal shock

    NASA Technical Reports Server (NTRS)

    Cole, G. L.; Willoh, R. G.

    1975-01-01

    A linearized mathematical analysis is presented for determining the response of normal shock position and subsonic duct pressures to flow-field perturbations upstream of the normal shock in mixed-compression supersonic inlets. The inlet duct cross-sectional area variation is approximated by constant-area sections; this approximation results in one-dimensional wave equations. A movable normal shock separates the supersonic and subsonic flow regions, and a choked exit is assumed for the inlet exit condition. The analysis leads to a closed-form matrix solution for the shock position and pressure transfer functions. Analytical frequency response results are compared with experimental data and a method of characteristics solution.

  3. Te inclusion-induced electrical field perturbation in CdZnTe single crystals revealed by Kelvin probe force microscopy.

    PubMed

    Gu, Yaxu; Jie, Wanqi; Li, Linglong; Xu, Yadong; Yang, Yaodong; Ren, Jie; Zha, Gangqiang; Wang, Tao; Xu, Lingyan; He, Yihui; Xi, Shouzhi

    2016-09-01

    To understand the effects of tellurium (Te) inclusions on the device performance of CdZnTe radiation detectors, the perturbation of the electrical field in and around Te inclusions was studied in CdZnTe single crystals via Kelvin probe force microscopy (KPFM). Te inclusions were proved to act as lower potential centers with respect to surrounding CdZnTe matrix. Based on the KPFM results, the energy band diagram at the Te/CdZnTe interface was established, and the bias-dependent effects of Te inclusion on carrier transportation is discussed. PMID:27376976

  4. Hydrogen bond perturbation in hen egg white lysozyme by external electromagnetic fields: A nonequilibrium molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Solomentsev, Gleb Y.; English, Niall J.; Mooney, Damian A.

    2010-12-01

    Nonequilibrium molecular dynamics simulations of a charge-neutral mutant of hen egg white lysozyme have been performed at 300 K and 1 bar in the presence of external microwave fields (2.45 to 100 GHz) of an rms electric field intensity of 0.05 V Å-1. A systematic study was carried out of the distributions of persistence times and energies of each intraprotein hydrogen bond in between breakage and reformation, in addition to overall persistence over 20 ns simulations, vis-à-vis equilibrium, zero-field conditions. It was found that localized translational motion for formally charged residues led to greater disruption of associated hydrogen bonds, although induced rotational motion of strongly dipolar residues also led to a degree of hydrogen bond perturbation. These effects were most apparent in the solvent exposed exterior of hen egg white lysozyme, in which the intraprotein hydrogen bonds tend to be weaker.

  5. Tuning the DNA Conformational Perturbations Induced by Cytotoxic Platinum-Acridine Bisintercalators: Effect of Metal cis/trans Isomerism and DNA Threading Groups

    PubMed Central

    Choudhury, Jayati Roy; Guddneppanavar, Rajsekhar; Saluta, Gilda; Kucera, Gregory L.; Bierbach, Ulrich

    2009-01-01

    Four highly charged, water soluble platinum-acridine bisintercalating agents have been synthesized. Depending on the cis/trans isomerism of the metal and the nature of the acridine side chains, bisintercalation induces/stabilizes the classical Watson-Crick B-form or a non-B-form. Circular dichroism spectra and chemical footprinting experiments suggest that compound 4, the most active derivative in HL-60 cells, produces a structurally severely perturbed DNA with features of a Hoogsteen base-paired biopolymer. PMID:18457380

  6. SU-E-P-34: Dose Perturbation Caused by Sun Nuclear QED Diode When Used for Very Small Electron Fields

    SciTech Connect

    Klash, S; Steinman, J; Stanley, T

    2015-06-15

    Purpose: Diodes are utilized by radiotherapy departments to help verify that treatment fields are being delivered correctly to the patient. Some treatment fields utilize electron beams along with a cerrobend cutout to shape the beam to the area to be treated. Cerrobend cutouts can sometimes be very small < 2×2-cm2. Some published work has addressed diode perturbation for cutout sizes down to 1.5-cm, this work addresses the diode perturbation of the Sun Nuclear QEDTM diode for cutouts as small as 0.5-cm in diameter. Methods: Measurements were taken with an A16 Exradin micro-chamber in Solid Water to 100-cm SSD. Dmax was determined for each cutout using various amounts of Solid Water in 1–2 mm increments to account for the dmax shifting in small fields. The diode was placed on top of the solid water to 100-cm SSD in the center of the cutout. Measurements were taken with no diode for comparison. The cutouts ranged in diameter from 0.5-cm to 5.0-cm and included the open 6×6 insert. Measurements were made for energies 6, 9, 12, 15,&18 MeV. Results: For 6 MeV, the percent dose reduction from the diode in the cutout field compared to the field without the diode ranged from 35% to 25% as a function of cutout size. For higher energies, this percentage decreased and generally was 25% to 15%. It was observed that dmax shifts significantly upstream for very small cutouts (<2-cm diameter) to less than 1 cm for all energies. Conclusion: The presence of diodes in small electron fields is enough to cause significant dose perturbation to the target volume. It is recommended that diodes for very small electron fields be used sparingly or possibly with a dose correction per treatment fraction(s), if the total projected delivered dose is going to be significantly different from that prescribed by the physician.

  7. Modeling of divertor particle and heat loads during application of resonant magnetic perturbation fields for ELM control in ITER

    NASA Astrophysics Data System (ADS)

    Schmitz, O.; Becoulet, M.; Cahyna, P.; Evans, T. E.; Feng, Y.; Frerichs, H.; Kirschner, A.; Kukushkin, A.; Laengner, R.; Lunt, T.; Loarte, A.; Pitts, R.; Reiser, D.; Reiter, D.; Saibene, G.; Samm, U.

    2013-07-01

    First results from three-dimensional modeling of the divertor heat and particle flux pattern during application of resonant magnetic perturbation fields as ELM control scheme in ITER with the EMC3-Eirene fluid plasma and kinetic neutral transport code are discussed. The formation of a helical magnetic footprint breaks the toroidal symmetry of the heat and particle fluxes. Expansion of the flux pattern as far as 60 cm away from the unperturbed strike line is seen with vacuum RMP fields, resulting in a preferable heat flux spreading. Inclusion of plasma response reduces the radial extension of the heat and particle fluxes and results in a heat flux peaking closer to the unperturbed level. A strong reduction of the particle confinement is found. 3D flow channels are identified as a consistent reason due to direct parallel outflow from inside of the separatrix. Their radial inward expansion and hence the level of particle pump out is shown to be dependent on the perturbation level.

  8. n-body problem in general relativity up to the second post-Newtonian order from perturbative field theory

    SciTech Connect

    Chu Yizen

    2009-02-15

    Motivated by experimental probes of general relativity, we adopt methods from perturbative (quantum) field theory to compute, up to certain integrals, the effective Lagrangian for its n-body problem. Perturbation theory is performed about a background Minkowski space-time to O[(v/c){sup 4}] beyond Newtonian gravity, where v is the typical speed of these n particles in their center of energy frame. For the specific case of the 2-body problem, the major efforts underway to measure gravitational waves produced by inspiraling compact astrophysical binaries require their gravitational interactions to be computed beyond the currently known O[(v/c){sup 7}]. We argue that such higher order post-Newtonian calculations must be automated for these field theoretic methods to be applied successfully to achieve this goal. In view of this, we outline an algorithm that would in principle generate the relevant Feynman diagrams to an arbitrary order in v/c and take steps to develop the necessary software. The Feynman diagrams contributing to the n-body effective action at O[(v/c){sup 6}] beyond Newton are derived.

  9. Theory and simulation of quasilinear transport from external magnetic field perturbations in a DIII-D plasma

    NASA Astrophysics Data System (ADS)

    Waltz, R. E.; Ferraro, N. M.

    2015-04-01

    The linear response profiles for the 3D perturbed magnetic fields, currents, ion velocities, plasma density, pressures, and electric potential from low-n external resonant magnetic field perturbations (RMPs) are obtained from the collisional two-fluid M3D-C1 code [N. M. Ferraro and S. C. Jardin, J. Comput. Phys. 228, 7742 (2009)]. A newly developed post-processing RMPtran code computes the resulting quasilinear E×B and magnetic (J×B) radial transport flows with respect to the unperturbed flux surfaces in all channels. RMPtran simulations focus on ion (center of mass) particle and transient non-ambipolar current flows, as well as the toroidal angular momentum flow. The paper attempts to delineate the RMP transport mechanisms that might be responsible for the RMP density pump-out seen in DIII-D [M. A. Mahdavi and J. L. Luxon, Fusion Sci. Technol. 48, 2 (2005)]. Experimentally, the starting high toroidal rotation does not brake to a significantly lower rotation after the pump-out suggesting that convective and E×B transport mechanisms dominate. The direct J×B torque from the transient non-ambipolar radial current expected to accelerate plasma rotation is shown to cancel much of the Maxwell stress J×B torque expected to brake the plasma rotation. The dominant E×B Reynolds stress accelerates rotation at the top of the pedestal while braking rotation further down the pedestal.

  10. Destruction of Invariant Surfaces and Magnetic Coordinates for Perturbed Magnetic Fields

    SciTech Connect

    S.R. Hudson

    2003-11-20

    Straight-field-line coordinates are constructed for nearly integrable magnetic fields. The coordinates are based on the robust, noble-irrational rotational-transform surfaces, whose existence is determined by an application of Greene's residue criterion. A simple method to locate these surfaces is described. Sequences of surfaces with rotational-transform converging to low order rationals maximize the region of straight-field-line coordinates.

  11. Dosimetric Verification and Validation of Conformal and IMRT Treatments Fields with an Ionization Chamber 2D-Array

    NASA Astrophysics Data System (ADS)

    Evangelina, Figueroa M.; Gabriel, Reséndiz G.; Miguel, Pérez P.

    2008-08-01

    A three-dimensional treatment planning system requires comparisons of calculated and measured dose distributions. It is necessary to confirm by means of patient specific QA that the dose distributions are correctly calculated, and that the patient data is correctly transferred to and delivered by the treatment machine. We used an analysis software for bi-dimensional dosimetric verification of conformal treatment and IMRT fields using as objective criterion the gamma index. An ionization chamber bi-dimensional array was used for absolute dose measurement in the complete field area.

  12. Conformal bootstrap in embedding space

    NASA Astrophysics Data System (ADS)

    Fortin, Jean-François; Skiba, Witold

    2016-05-01

    It is shown how to obtain conformal blocks from embedding space with the help of the operator product expansion. The minimal conformal block originates from scalar exchange in a four-point correlation function of four scalars. All remaining conformal blocks are simple derivatives of the minimal conformal block. With the help of the orthogonality properties of the conformal blocks, the analytic conformal bootstrap can be implemented directly in embedding space, leading to a Jacobi-like definition of conformal field theories.

  13. Eikonalization of conformal blocks

    SciTech Connect

    Fitzpatrick, A. Liam; Kaplan, Jared; Walters, Matthew T.; Wang, Junpu

    2015-09-03

    Classical field configurations such as the Coulomb potential and Schwarzschild solution are built from the t-channel exchange of many light degrees of freedom. We study the CFT analog of this phenomenon, which we term the 'eikonalization' of conformal blocks. We show that when an operator T appears in the OPE Ο(x)Ο(0), then the large spin Fock space states [TT···T] also appear in this OPE with a computable coefficient. The sum over the exchange of these Fock space states in an correlator build the classical 'T field' in the dual AdS description. In some limits the sum of all Fock space exchanges can be represented as the exponential of a single T exchange in the 4-pt correlator of O. Our results should be useful for systematizing 1/ℓ perturbation theory in general CFTs and simplifying the computation of large spin OPE coefficients. As examples we obtain the leading log ℓ dependence of Fock space conformal block coefficients, and we directly compute the OPE coefficients of the simplest ‘triple-trace’ operators.

  14. Eikonalization of conformal blocks

    DOE PAGESBeta

    Fitzpatrick, A. Liam; Kaplan, Jared; Walters, Matthew T.; Wang, Junpu

    2015-09-03

    Classical field configurations such as the Coulomb potential and Schwarzschild solution are built from the t-channel exchange of many light degrees of freedom. We study the CFT analog of this phenomenon, which we term the 'eikonalization' of conformal blocks. We show that when an operator T appears in the OPE Ο(x)Ο(0), then the large spin Fock space states [TT···T]ℓ also appear in this OPE with a computable coefficient. The sum over the exchange of these Fock space states in an correlator build the classical 'T field' in the dual AdS description. In some limits the sum of all Fock spacemore » exchanges can be represented as the exponential of a single T exchange in the 4-pt correlator of O. Our results should be useful for systematizing 1/ℓ perturbation theory in general CFTs and simplifying the computation of large spin OPE coefficients. As examples we obtain the leading log ℓ dependence of Fock space conformal block coefficients, and we directly compute the OPE coefficients of the simplest ‘triple-trace’ operators.« less

  15. Conformal weights of charged Rényi entropy twist operators for free scalar fields in arbitrary dimensions

    NASA Astrophysics Data System (ADS)

    Dowker, J. S.

    2016-04-01

    I compute the conformal weights of the twist operators of free scalar fields for charged Rényi entropy in both odd and even dimensions. Explicit expressions can be found, in odd dimensions as a function of the chemical potential in the absence of a conical singularity and thence by images for all integer coverings. This method, developed some time ago, is equivalent, in results, to the replica technique. A review is given. The same method applies for even dimensions but a general form is more immediately available. For no chemical potential, the closed form in the covering order is written in an alternative way related to old trigonometric sums. Some derivatives are obtained. An analytical proof is given of a conjecture made by Bueno, Myers and Witczak-Krempa regarding the relation between the conformal weights and a corner coefficient (a universal quantity) in the Rényi entropy.

  16. Quantum corrections to the gravitational potentials of a point source due to conformal fields in de Sitter

    NASA Astrophysics Data System (ADS)

    Fröb, Markus B.; Verdaguer, Enric

    2016-03-01

    We derive the leading quantum corrections to the gravitational potentials in a de Sitter background, due to the vacuum polarization from loops of conformal fields. Our results are valid for arbitrary conformal theories, even strongly interacting ones, and are expressed using the coefficients b and b' appearing in the trace anomaly. Apart from the de Sitter generalization of the known flat-space results, we find two additional contributions: one which depends on the finite coefficients of terms quadratic in the curvature appearing in the renormalized effective action, and one which grows logarithmically with physical distance. While the first contribution corresponds to a rescaling of the effective mass, the second contribution leads to a faster fall-off of the Newton potential at large distances, and is potentially measurable.

  17. Perturbative approach to the problem of particle production in electric field on de Sitter universe

    NASA Astrophysics Data System (ADS)

    Crucean, Cosmin; Băloi, Mihaela-Andreea

    2016-04-01

    In this paper, we study the problem of scalar particle production in external electric field in de Sitter geometry. The total probability is calculated using the previously obtained result in [M. A. Băloi, Mod. Phys. Lett. A 29, 1450138 (2014)] for transition amplitude in external electric field on de Sitter space. Then we make a graphical study of the total probability in terms of the ratio mass of the particle/expansion factor. Our results show that the probability depend on the direction in which the particles are emitted and that the probability becomes maximum when particles are emitted on the direction of the electric field. In the Minkowski limit, we obtain that the probability is vanishing.

  18. Resonant features of energy and particle transport during application of resonant magnetic perturbation fields at TEXTOR and DIII-D

    SciTech Connect

    Schmitz, O.; Evans, T. E.; Fenstermacher, M. E.; Lehnen, M.; Stoschus, H.

    2012-01-01

    In this paper, results of a direct comparison of TEXTOR and DIII-D experiments with resonant magnetic perturbation (RMP) fields are presented. This comparison of resistive L-mode plasmas at TEXTOR with highly conductive H-mode plasmas at DIII-D is useful to identify generic physics mechanisms during application of RMP fields with a strong field line pitch angle alignment in the plasma edge. A reduction in the pedestal electron pressure p(e) with increasing extension of the vacuum modelled stochastic layer and p(e) recovery with decreasing layer width is found caused by a q(95) resonant reduction in the edge (0.8 < Psi(N) < 0.95) electron temperature T-e(q(95)) on both devices. For RMP edge-localized mode (ELM) suppressed H-mode plasmas at DIII-D, the gradients del T-e and nominal values of T-e are reduced in this edge region while increasing in the pedestal (0.95 < Psi(N) < 1.0) with RMP field applied and both are highly dependent on q(95). In contrast, an increase in the central ion temperature with strong steepening of the ion temperature profile at mid-radius is found-again being highly dependent on q(95). However, these resonant thermal transport effects are only seen in high triangularity plasmas revealing a strong shape dependence of the thermal transport. In contrast to the highly q(95) dependent thermal transport features, the reduction of n(e)-known as density pump out-shows a much weaker dependence on q(95). We show the potential to reduce the RMP induced particle pump out by fine tuning of the RMP spectral properties. At low resonant field amplitudes enhanced particle confinement is seen in high-field side limited L-mode discharges on both devices while higher resonant field amplitudes yield particle pumps out.

  19. Non perturbative approach for a polar and polarizable linear molecule in an inhomogeneous electric field: Application to molecular beam deviation experiments

    NASA Astrophysics Data System (ADS)

    Benichou, E.; Allouche, A. R.; Antoine, R.; Aubert-Frecon, M.; Bourgoin, M.; Broyer, M.; Dugourd, Ph.; Hadinger, G.; Rayane, D.

    A non perturbative approach is used to solve the problem of a rigid linear molecule with both a permanent dipole moment and a static dipole polarizability, in a static electric field. Eigenenergies are obtained and compared to perturbative low field and high field approximations. Analytical expressions for the orientation parameters and for the gradient of the energy are given. This non perturbative approach is applied to the simulation of beam deviation experiments in strong electric field. Results of simulations are given for inhomogeneous alkali dimers. For LiNa, the simulations are compared to experimental data. For LiK, deviation profiles have been simulated in order to prepare future experiments on this molecule.

  20. Study of the phase structure of Abelian field theories through non-lattice, non-perturbative calculations

    SciTech Connect

    Karanikas, A.I.; Ktorides, C.N.; Mavromatos, N.E.

    1986-12-01

    A recently proposed approach to gauge field theories, by which one formulates them non-locally and subsequently approaches locality arbitrarily close, is applied to U(1) gauge theories. We test the possibility that the aformentioned methodology might introduce a measure in the functional integral which supports non-perturbative calculations in the continuum. In particular, we are able to carry relevant calculations pertaining to the expectation value of the Wilson's loop operator in 3+1, 2+1 and 1+1 dimensions. The results are similar to ones obtained through the lattice regularization of R(1) gauge theory, with the important difference that in our case they refer to continuum U(1) gauge theory, as a function of the bare coupling constant. We further solidify the validity of our approach by conducting a calculation referring to the 2-dimensional scalar Heisenberg model, remaining always in the continuum. copyright 1986 Academic Press, Inc.

  1. Constraints on perturbative RG flows in six dimensions

    NASA Astrophysics Data System (ADS)

    Stergiou, Andreas; Stone, David; Vitale, Lorenzo G.

    2016-08-01

    When conformal field theories (CFTs) are perturbed by marginally relevant deformations, renormalization group (RG) flows ensue that can be studied with perturbative methods, at least as long as they remain close to the original CFT. In this work we study such RG flows in the vicinity of six-dimensional unitary CFTs. Neglecting effects of scalar operators of dimension two and four, we use Weyl consistency conditions to prove the a-theorem in perturbation theory, and establish that scale implies conformal invariance. We identify a quantity that monotonically decreases in the flow to the infrared due to unitarity, showing that it does not agree with the one studied recently in the literature on the six-dimensional ϕ 3 theory.

  2. Can we derive the current density from three point LEO measurements of the magnetic field perturbations?

    NASA Astrophysics Data System (ADS)

    Gjerloev, J. W.; Potter, M.; Muhleisen, M.; Friel, M. M.; Martin, P.; Le, G.; Stolle, C.; Luhr, H.

    2014-12-01

    In this paper, we perform critical test of the well-known curlometer technique. The curlometer technique allows a derivation of the current density using measurements of the magnetic field at spatially separated points. At LEO altitudes this generally three dimensionally problem is simplified to a two dimensions by the fact that the current is almost solely flowing along the magnetic field lines. Strictly speaking the current density is derived from integration around a closed loop but in the curlometer technique this integration is simplified to a summation over just three points. In this paper we present a critical analysis of when and to what extend this approximation is valid. We show some simple theoretical considerations, results from a series of simulations, and finally apply the knowledge to ESA SWARM measurements.

  3. Meso-beta scale perturbations of the wind field by thunderstorm cells

    NASA Technical Reports Server (NTRS)

    Ulanski, S. L.; Heymsfield, G. M.

    1986-01-01

    Data from the high density storm-scale rawinsonde network of the Severe Environmental Storms and Mesoscale Experiment revealed temporal and spatial changes in the divergence fields of the troposphere in response to severe storm evolution on May 2, 1979; these changes were detectable on the meso-beta scale. This unique set of data was subsequently used to study the evolution of the wind, divergence and vertical motion fields in the presence of intense convection. Mid- and upper-tropospheric divergence was superimposed over low-level convergence. The divergence, which has a maximum value of .0004/s, occurred 75 to 100 km upwind as well as over the tornadic cells. To the south of the storm cells, the kinematic pattern was in reverse, upper level convergence was superimposed over low-level divergence. A vertical motion doublet was found to ascend over the squall line and descend about 70 km south of the squall line. It is suggested that the following effects are accountable for the nature of the kinematic fields: (1) blocking of tropospheric environmental flow by the storm cells, (2) anvil outflows, particularly from the tornadic cells, and (3) divergence from the exit region of the jet stream.

  4. A STUDY OF THE EDGE FIELD EFFECT USING MAFIA SIMULATIONS CONFORMAL MAPPING

    SciTech Connect

    ZHAO,Y.

    1999-10-01

    It was found that the measured Q value of a tape resonator has a large difference with that calculated with MAFIA. This difference is recognized to be mainly due to the error in the simulation, which is unable to handle a sharp edge. This note addresses the 2-dimensional MAFIA simulation and conformal mapping. It shows the error could be as high as 60 %. Reasonable caution should be exercised in the use of MAFIA, and other codes as well, in calculating Q value if a sharp edge exists in the problem.

  5. Large-scale magnetic field perturbation arising from the 18 May 1980 eruption from Mount St. Helens, Washington

    USGS Publications Warehouse

    Mueller, R.J.; Johnston, M.J.S.

    1989-01-01

    A traveling magnetic field disturbance generated by the 18 may 1980 eruption of Mount St. Helens at 1532 UT was detected on an 800-km linear array of recording magnetometers installed along the San Andreas fault system in California, from San Francisco to the Salton Sea. Arrival times of the disturbance field, from the most northern of these 24 magnetometers (996 km south of the volcano) to the most southern (1493 km S23?? E), are consistent with the generation of a traveling ionospheric disturbance stimulated by the blast pressure wave in the atmosphere. The first arrivals at the north and the south ends of the array occurred at 26 and 48 min, respectively, after the initial eruption. Apparent average wave velocity through the array is 309 ?? 14 m s-1 but may have approached 600 m s-1 close to the volcano. The horizontal phase and the group velocity of ??? 300 m s-1 at periods of 70-80 min, and the attenuation with distance, strongly suggest that the magnetic field perturbations at distances of 1000-1500 km are caused by gravity mode acoustic-gravity waves propagating at F-region heights in the ionosphere. ?? 1989.

  6. Numerical study of induced current perturbations in the vicinity of excitable cells exposed to extremely low frequency magnetic fields

    NASA Astrophysics Data System (ADS)

    Hassan, Noha; Chatterjee, Indira; Publicover, Nelson G.; Craviso, Gale L.

    2003-10-01

    Realistic three-dimensional cell morphologies were modelled to determine the current density induced in excitable cell culture preparations exposed to 60 Hz magnetic fields and to identify important factors that can influence the responses of cells to these fields. Cell morphologies representing single spherical adrenal chromaffin cells, single elongated smooth muscle cells and chromaffin cell aggregates in a Petri dish containing culture medium were modelled using the finite element method. The computations for a spherical cell revealed alterations in the magnitude and spatial distribution of the induced current density in the immediate vicinity of the cell. Maxima occurred at the equatorial sides and minima at the poles. Proximity of cells to each other as well as cell aggregate shape, size and orientation with respect to the induced current influenced the magnitude and spatial distribution of the induced current density. For an elongated cell, effects on the induced current density were highly dependent on cell orientation with respect to the direction of the induced current. These results provide novel insights into the perturbations in induced current that occur in excitable cell culture preparations and lay a foundation for understanding the mechanisms of interaction with extremely low frequency magnetic fields at the tissue level.

  7. Two substorm studies of relations between westward electric fields in the outer plasmasphere, auroral activity, and geomagnetic perturbations

    NASA Technical Reports Server (NTRS)

    Carpenter, D. L.; Akasofu, S.

    1972-01-01

    Temporal variations of the westward component of the magnetospheric convection electric field in the outer plasmasphere were compared to auroral activity near L = 7, and to variations in the geomagnetic field at middle and high latitudes. The substorms occurred on July 29, 1965 near 0530 UT and on August 20, 1965 near 0730 UT. The results on westward electric field E(w) were obtained by the whistler method using data from Eights, Antarctica (L is approximately 4). All sky camera records were obtained from Byrd, Antarctica, (L is approximately 7), located within about 1 hour of Eights in magnetic local time. It was found that E(w) within the outer plasmasphere increased rapidly to substorm levels about the time of auroral expansion at nearby longitudes. This behavior is shown to differ from results on E(w) from balloons, which show E(w) reaching enhanced levels prior to the expansion. A close temporal relation was found between the rapid, substorm associated increases in E(w) and a well known type of nightside geomagnetic perturbation. Particularly well defined was the correlation of E(w) rise and a large deviation of the D component at middle latitudes.

  8. Helical modulation of the electrostatic plasma potential due to edge magnetic islands induced by resonant magnetic perturbation fields at TEXTOR

    SciTech Connect

    Ciaccio, G. Spizzo, G.; Schmitz, O. Frerichs, H.; Abdullaev, S. S.; Evans, T. E.; White, R. B.

    2015-10-15

    The electrostatic response of the edge plasma to a magnetic island induced by resonant magnetic perturbations to the plasma edge of the circular limiter tokamak TEXTOR is analyzed. Measurements of plasma potential are interpreted by simulations with the Hamiltonian guiding center code ORBIT. We find a strong correlation between the magnetic field topology and the poloidal modulation of the measured plasma potential. The ion and electron drifts yield a predominantly electron driven radial diffusion when approaching the island X-point while ion diffusivities are generally an order of magnitude smaller. This causes a strong radial electric field structure pointing outward from the island O-point. The good agreement found between measured and modeled plasma potential connected to the enhanced radial particle diffusivities supports that a magnetic island in the edge of a tokamak plasma can act as convective cell. We show in detail that the particular, non-ambipolar drifts of electrons and ions in a 3D magnetic topology account for these effects. An analytical model for the plasma potential is implemented in the code ORBIT, and analyses of ion and electron radial diffusion show that both ion- and electron-dominated transport regimes can exist, which are known as ion and electron root solutions in stellarators. This finding and comparison with reversed field pinch studies and stellarator literature suggest that the role of magnetic islands as convective cells and hence as major radial particle transport drivers could be a generic mechanism in 3D plasma boundary layers.

  9. The pseudo-conformal universe: scale invariance from spontaneous breaking of conformal symmetry

    SciTech Connect

    Hinterbichler, Kurt; Khoury, Justin E-mail: jkhoury@sas.upenn.edu

    2012-04-01

    We present a novel theory of the very early universe which addresses the traditional horizon and flatness problems of big bang cosmology and predicts a scale invariant spectrum of perturbations. Unlike inflation, this scenario requires no exponential accelerated expansion of space-time. Instead, the early universe is described by a conformal field theory minimally coupled to gravity. The conformal fields develop a time-dependent expectation value which breaks the flat space so(4,2) conformal symmetry down to so(4,1), the symmetries of de Sitter, giving perturbations a scale invariant spectrum. The solution is an attractor, at least in the case of a single time-dependent field. Meanwhile, the metric background remains approximately flat but slowly contracts, which makes the universe increasingly flat, homogeneous and isotropic, akin to the smoothing mechanism of ekpyrotic cosmology. Our scenario is very general, requiring only a conformal field theory capable of developing the appropriate time-dependent expectation values, and encompasses existing incarnations of this idea, specifically the U(1) model of Rubakov and the Galileon Genesis scenario. Its essential features depend only on the symmetry breaking pattern and not on the details of the underlying lagrangian. It makes generic observational predictions that make it potentially distinguishable from standard inflation, in particular significant non-gaussianities and the absence of primordial gravitational waves.

  10. A coarse-grained generalized second law for holographic conformal field theories

    NASA Astrophysics Data System (ADS)

    Bunting, William; Fu, Zicao; Marolf, Donald

    2016-03-01

    We consider the universal sector of a d\\gt 2 dimensional large-N strongly interacting holographic CFT on a black hole spacetime background B. When our CFT d is coupled to dynamical Einstein-Hilbert gravity with Newton constant G d , the combined system can be shown to satisfy a version of the thermodynamic generalized second law (GSL) at leading order in G d . The quantity {S}{CFT}+\\frac{A({H}B,{perturbed})}{4{G}d} is non-decreasing, where A({H}B,{perturbed}) is the (time-dependent) area of the new event horizon in the coupled theory. Our S CFT is the notion of (coarse-grained) CFT entropy outside the black hole given by causal holographic information—a quantity in turn defined in the AdS{}d+1 dual by the renormalized area {A}{ren}({H}{{bulk}}) of a corresponding bulk causal horizon. A corollary is that the fine-grained GSL must hold for finite processes taken as a whole, though local decreases of the fine-grained generalized entropy are not obviously forbidden. Another corollary, given by setting {G}d=0, states that no finite process taken as a whole can increase the renormalized free energy F={E}{out}-{{TS}}{CFT}-{{Ω }}J, with T,{{Ω }} constants set by {H}B. This latter corollary constitutes a 2nd law for appropriate non-compact AdS event horizons.

  11. Perturbations of near-horizon geometries and instabilities of Myers-Perry black holes

    SciTech Connect

    Durkee, Mark N.; Reall, Harvey S.

    2011-05-15

    It is shown that the equations governing linearized gravitational (or electromagnetic) perturbations of the near-horizon geometry of any known extreme vacuum black hole (allowing for a cosmological constant) can be Kaluza-Klein reduced to give the equation of motion of a charged scalar field in AdS{sub 2} with an electric field. One can define an effective Breitenloehner-Freedman bound for such a field. We conjecture that if a perturbation preserves certain symmetries then a violation of this bound should imply an instability of the full black hole solution. Evidence in favor of this conjecture is provided by the extreme Kerr solution and extreme cohomogeneity-1 Myers-Perry solution. In the latter case, we predict an instability in seven or more dimensions and, in five dimensions, we present results for operator conformal weights assuming the existence of a conformal field theory dual. We sketch a proof of our conjecture for scalar field perturbations.

  12. Selective Detection of Live Pathogens via Surface-Confined Electric Field Perturbation on Interdigitated Silicon Transducers

    PubMed Central

    de la Rica, Roberto; Baldi, Antonio; Fernández-Sánchez, César; Matsui, Hiroshi

    2010-01-01

    Detection of physical changes of cells is emerging as a new diagnostic approach to determine their phenotypical features. One of such changes is related to their viability; live (viable) cells are more voluminous than the dead ones, and monitoring this parameter in tissue cells becomes essential in fields such as drug discovery and hazard evaluation. In the area of pathogen detection, an analytical system capable of specifically detecting viable cells with the simple sample preparation and detection process would be highly desirable since live microorganisms can rapidly increase their numbers even at extremely low concentration and become a severe health risk. However, current sensing strategies cannot clearly determine the viability of cells, and hence they are susceptible to false-positive signals from harmless dead pathogens. Here we developed a robust electronic immunoassay that uses a pair of polycrystalline silicon interdigitated electrodes for the rapid detection of pathogens with high specificity for live cells. After bacterial cells were specifically anchored to the surface of the antibody-modified electrode, the characteristic geometry of the transducer enables the selective detection of viable cells with a limit of detection of 3 × 102 cfu/mL and an incubation time of only 1 h. The CMOS compatible fabrication process of the chip along with the label-free, reagentless electronic detection and the easy electrode regeneration to recycle for another impedance measurement make this approach an excellent candidate for oncoming economical in-field viable-cell detection systems, fully integrable with sophisticated signal processing circuits. PMID:19334738

  13. PAC (perturbed angular correlation) perturbation factor for spin 5/2 nuclei subject to a rapidly fluctuation EFC (electric field gradient)

    SciTech Connect

    Evenson, W.E. . Dept. of Physics and Astronomy); McKale, A.G.; Su, H.T.; Gardner, J.A. . Dept. of Physics)

    1990-01-01

    We report numerical computations of the PAC perturbation factor G{sub 2}(t) for spin 5/2 nuclei subject to a static EFG symmetric about the z-axis and an additional axially-symmetric EFG hose symmetry axis fluctuates randomly among the x,y,z directions. For sufficiently large fluctuation rates, the numerical results are described by the expression for the static interaction alone with the addition of relaxation terms. Results of applying this model to {sup 111}Cd TDPAC measurements on tetragonal ZrO{sub 2} are described briefly. The model allows one to evaluate the probability that oxygen vacancies are trapped, the energy of association of vacancy-metal pairs, and the vacancy activation energy of motion. 4 refs., 3 figs.

  14. Improved Field Emission Algorithms for Modeling Field Emission Devices Using a Conformal Finite-Difference Time-Domain Particle-in-Cell Method

    NASA Astrophysics Data System (ADS)

    Lin, M. C.; Loverich, J.; Stoltz, P. H.; Nieter, C.

    2013-10-01

    This work introduces a conformal finite difference time domain (CFDTD) particle-in-cell (PIC) method with an improved field emission algorithm to accurately and efficiently study field emission devices. The CFDTD method is based on the Dey-Mittra algorithm or cut-cell algorithm, as implemented in the Vorpal code. For the field emission algorithm, we employ the elliptic function v(y) found by Forbes and a new fitting function t(y)2 for the Fowler-Nordheim (FN) equation. With these improved correction factors, field emission of electrons from a cathode surface is much closer to the prediction of the exact FN formula derived by Murphy and Good. This work was supported in part by both the U.S. Department of Defense under Grant No. FA9451-07-C-0025 and the U.S. Department of Energy under Grant No. DE-SC0004436.

  15. Six-dimensional supergravity on S3 x AdS3 and 2d conformal field theory

    SciTech Connect

    de Boer, Jan

    1998-06-20

    In this paper we study the relation between six-dimensional supergravity compactified on S{sup 3} x AdS{sub 3} and certain two-dimensional conformal field theories. We compute the Kaluza-Klein spectrum of supergravity using representation theory; these methods are quite general and can also be applied to other compactifications involving anti-de Sitter spaces. A detailed comparison between the spectrum of the two-dimensional conformal field theory and supergravity is made, and we find complete agreement. This applies even at the level of certain non-chiral primaries, and we propose a resolution to the puzzle of the missing states recently raised by Vafa. As a further illustration of the method the Kaluza-Klein spectra of F-theory on M{sup 6} x S{sup 3} x AdS{sub 3} and of M-theory on M{sup 6} x S{sup 2} x AdS{sub 3} are computed, with M{sup 6} some Calabi-Yau manifold.

  16. The Plasma and Field Perturbation Around a Charged Dust Cloud in the Solar Wind

    NASA Astrophysics Data System (ADS)

    Jia, Y. D.; Russell, C. T.; Lai, H.; Wei, H.

    2014-12-01

    When asteroids and meteoroids collide at their typical speeds of 20km/s at 1AU, they can totally disrupt each other if their mass ratios are within a factor of 106. The resulting charged dust and gas can be picked up by the solar wind, resulting in a large magnetic structure containing over 106kg of mass, accelerated to almost the solar wind speed. This dust is invisible to our Earth-based detectors as are the impactors and targets but they can be detected by our interplanetary spacecraft and they do create ground-level magnetospheric disturbances when they impact the Earth. Moreover we can identify the parent bodies for these impacting bolides by determining which asteroids cross the ecliptic plane along the path of these disturbances carried by the solar wind. Hence, these structures can be used in a planetary defense strategy. Since they have a very practical application we need to understand their formation and evolution better. We apply our multi-fluid code to model this interaction, to show how the field is affected by charged dust. We assume a cloud of charged dust moving close to the solar wind speed, but a small velocity difference exists between the dust and ions. Gravity pulls horizontally opposite to the solar wind plasma, maintaining the concentration of dust cloud.

  17. Conformal Locoregional Breast Irradiation with an Oblique Parasternal Photon Field Technique

    SciTech Connect

    Erven, Katrien; Petillion, Saskia; Weltens, Caroline; Van den Heuvel, Frank; Defraene, Gilles; Van Limbergen, Erik; Van den Bogaert, Walter

    2011-04-01

    We evaluated an isocentric technique for conformal irradiation of the breast, internal mammary, and medial supra-clavicular lymph nodes (IM-MS LN) using the oblique parasternal photon (OPP) technique. For 20 breast cancer patients, the OPP technique was compared with a conventional mixed-beam technique (2D) and a conformal partly wide tangential (PWT) technique, using dose-volume histogram analysis and normal tissue complication probabilities (NTCPs). The 3D techniques resulted in a better target coverage and homogeneity than did the 2D technique. The homogeneity index for the IM-MS PTV increased from 0.57 for 2D to 0.90 for PWT and 0.91 for OPP (both p < 0.001). The OPP technique was able to reduce the volume of heart receiving more than 30 Gy (V{sub 30}), the cardiac NTCP, and the volume of contralateral breast receiving 5 Gy (V{sub 5}) compared with the PWT plans (all p < 0.05). There is no significant difference in mean lung dose or lung NTCP between both 3D techniques. Compared with the PWT technique, the volume of lung receiving more than 20 Gy (V{sub 20}) was increased with the OPP technique, whereas the volume of lung receiving more than 40 Gy (V{sub 40}) was decreased (both p < 0.05). Compared with the PWT technique, the OPP technique can reduce doses to the contralateral breast and heart at the expense of an increased lung V{sub 20}.

  18. Some data about the relationship between ths human state and external perturbations of geomagnetic field

    NASA Astrophysics Data System (ADS)

    Dimitrova, S.; Stoilova, I.; Yanev, T.

    The influence of solar activity changes and related to them geomagnetic field variations on human health is confirmed in a lot of publications but the investigations in this area are still sporadic and incomplete because of the fact that it is difficult to separate the geomagnetic influence from the environmental factor complex, which influence the human life activity. That is why we have studied the influence of changes in geomagnetic activity on human physiological, psycho-physiological parameters and behavioural reactions. In this article we looked for influence of changes in GMA on the systolic and diastolic blood pressure and pulse-rate. We examined 54 volunteers. 26 persons of them had some cardio-vascular or blood pressure disturbances. The registrations were performed every day at one and the same time for each person during the period 1.10 - 10.11.2001. Four-way analysis of variance (MANOVA method) with factors: GMA, day, sex and cardiovascular pathology was performed. GMA was divided into four levels according to the Kp- and Ap-index values. The days examined were divided into six levels in relation to the day with increased GMA. Factor "cardiovascular pathology" was divided into two levels: healthy subjects and subjects that had some cardio -vascular or blood pressure disturbances. When we employed four-way analysis of variance, the influence of some of the factors on the physiological parameters examined turned out to be statistically significant at p<0.05. Our investigations indicate that most of the persons examined irrespectively to their status could be sensitive to the geomagnetic disturbances.

  19. Effect of resonant magnetic perturbations on three dimensional equilibria in the Madison Symmetric Torus reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Munaretto, S.; Chapman, B. E.; Nornberg, M. D.; Boguski, J.; DuBois, A. M.; Almagri, A. F.; Sarff, J. S.

    2016-05-01

    The orientation of 3D equilibria in the Madison Symmetric Torus (MST) [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch can now be controlled with a resonant magnetic perturbation (RMP). Absent the RMP, the orientation of the stationary 3D equilibrium varies from shot to shot in a semi-random manner, making its diagnosis difficult. Produced with a poloidal array of saddle coils at the vertical insulated cut in MST's thick conducting shell, an m = 1 RMP with an amplitude br/B ˜ 10% forces the 3D structure into any desired orientation relative to MST's diagnostics. This control has led to improved diagnosis, revealing enhancements in both the central electron temperature and density. With sufficient amplitude, the RMP also inhibits the generation of high-energy (>20 keV) electrons, which otherwise emerge due to a reduction in magnetic stochasticity in the core. Field line tracing reveals that the RMP reintroduces stochasticity to the core. A m = 3 RMP of similar amplitude has little effect on the magnetic topology or the high-energy electrons.

  20. Realization of a quantum gate using gravitational search algorithm by perturbing three-dimensional harmonic oscillator with an electromagnetic field

    NASA Astrophysics Data System (ADS)

    Sharma, Navneet; Rawat, Tarun Kumar; Parthasarathy, Harish; Gautam, Kumar

    2016-06-01

    The aim of this paper is to design a current source obtained as a representation of p information symbols \\{I_k\\} so that the electromagnetic (EM) field generated interacts with a quantum atomic system producing after a fixed duration T a unitary gate U( T) that is as close as possible to a given unitary gate U_g. The design procedure involves calculating the EM field produced by \\{I_k\\} and hence the perturbing Hamiltonian produced by \\{I_k\\} finally resulting in the evolution operator produced by \\{I_k\\} up to cubic order based on the Dyson series expansion. The gate error energy is thus obtained as a cubic polynomial in \\{I_k\\} which is minimized using gravitational search algorithm. The signal to noise ratio (SNR) in the designed gate is higher as compared to that using quadratic Dyson series expansion. The SNR is calculated as the ratio of the Frobenius norm square of the desired gate to that of the desired gate error.

  1. Realization of a quantum gate using gravitational search algorithm by perturbing three-dimensional harmonic oscillator with an electromagnetic field

    NASA Astrophysics Data System (ADS)

    Sharma, Navneet; Rawat, Tarun Kumar; Parthasarathy, Harish; Gautam, Kumar

    2016-03-01

    The aim of this paper is to design a current source obtained as a representation of p information symbols {I_k} so that the electromagnetic (EM) field generated interacts with a quantum atomic system producing after a fixed duration T a unitary gate U(T) that is as close as possible to a given unitary gate U_g . The design procedure involves calculating the EM field produced by {I_k} and hence the perturbing Hamiltonian produced by {I_k} finally resulting in the evolution operator produced by {I_k} up to cubic order based on the Dyson series expansion. The gate error energy is thus obtained as a cubic polynomial in {I_k} which is minimized using gravitational search algorithm. The signal to noise ratio (SNR) in the designed gate is higher as compared to that using quadratic Dyson series expansion. The SNR is calculated as the ratio of the Frobenius norm square of the desired gate to that of the desired gate error.

  2. Resonant features of energy and particle transport during application of resonant magnetic perturbation fields at TEXTOR and DIII-D

    NASA Astrophysics Data System (ADS)

    Schmitz, O.; Evans, T. E.; Fenstermacher, M. E.; Lehnen, M.; Stoschus, H.; Unterberg, E. A.; Coenen, J. W.; Frerichs, H.; Jakubowski, M. W.; Laengner, R.; Lasnier, C. L.; Mordijck, S.; Moyer, R. A.; Osborne, T. H.; Reimerdes, H.; Reiter, D.; Samm, U.; Unterberg, B.; DIII-D, the; TEXTOR Teams

    2012-04-01

    In this paper, results of a direct comparison of TEXTOR and DIII-D experiments with resonant magnetic perturbation (RMP) fields are presented. This comparison of resistive L-mode plasmas at TEXTOR with highly conductive H-mode plasmas at DIII-D is useful to identify generic physics mechanisms during application of RMP fields with a strong field line pitch angle alignment in the plasma edge. A reduction in the pedestal electron pressure pe with increasing extension of the vacuum modelled stochastic layer and pe recovery with decreasing layer width is found caused by a q95 resonant reduction in the edge (0.8 < ΨN < 0.95) electron temperature Te(q95) on both devices. For RMP edge-localized mode (ELM) suppressed H-mode plasmas at DIII-D, the gradients ∇Te and nominal values of Te are reduced in this edge region while increasing in the pedestal (0.95 < ΨN < 1.0) with RMP field applied and both are highly dependent on q95. In contrast, an increase in the central ion temperature with strong steepening of the ion temperature profile at mid-radius is found—again being highly dependent on q95. However, these resonant thermal transport effects are only seen in high triangularity plasmas revealing a strong shape dependence of the thermal transport. In contrast to the highly q95 dependent thermal transport features, the reduction of ne—known as density pump out—shows a much weaker dependence on q95. We show the potential to reduce the RMP induced particle pump out by fine tuning of the RMP spectral properties. At low resonant field amplitudes enhanced particle confinement is seen in high-field side limited L-mode discharges on both devices while higher resonant field amplitudes yield particle pumps out. This is the paper of the IAEA contribution by Schmitz O. et al 2010 Key results from the DIII-D/TEXTOR Collaboration on the Physics of Stochastic Boundaries projected to ELM control at ITER, EXD/P3-30.

  3. The generalized Erlangen program and setting a geometry for four- dimensional conformal fields

    SciTech Connect

    Ne`eman, Y. |; Hehl, F.W.; Mielke, E.W.

    1993-10-22

    This is the text of a talk at the International Symposium on ``Mathematical Physics towards the XXI Century`` held in March 1993 at Beersheva, Israel. In the first part we attempt to summarize XXth Century Physics, in the light of Kelvin`s 1900 speech ``Dark Clouds over XIXth Century Physics.`` Contrary to what is usually said, Kelvin predicted that the ``clouds`` (relativity and quantum mechanics) would revolutionize physics and that one hundred years might be needed to harmonize them with classical physics. Quantum Gravity can be considered as a leftover from Kelvin`s program -- so are the problems with the interpretation of quantum mechanics. At the end of the XXth Century, the Standard Model is the new panoramic synthesis, drawn in gauge-geometric lines -- realizing the Erlangen program beyond F. Klein`s expectations. The hierarchy problem and the smallness of the cosmological constant are our ``clouds``, generations and the Higgs sector are to us what radioactivity was in 1900. In the second part we describe Metric-Affine spacetimes. We construct the Noether machinery and provide expressions for the conserved energy and hypermomentum. Superimposing conformal invariance over the affine structure induces the Virasoro-like infinite constraining algebra of diffeomorphisms, applied with constant parameters and opening the possibility of a 4DCFT, similar to 2DCFT.

  4. DBI realizations of the pseudo-conformal universe and Galilean Genesis scenarios

    SciTech Connect

    Hinterbichler, Kurt; Joyce, Austin; Khoury, Justin; Miller, Godfrey E.J. E-mail: joyceau@sas.upenn.edu E-mail: godfreym@sas.upenn.edu

    2012-12-01

    The pseudo-conformal universe is an alternative to inflation in which the early universe is described by a conformal field theory on approximately flat space-time. The fields develop time-dependent expectation values, spontaneously breaking the conformal symmetries to a de Sitter subalgebra, and fields of conformal weight zero acquire a scale invariant spectrum of perturbations. In this paper, we show that the pseudo-conformal scenario can be naturally realized within theories that would ordinarily be of interest for DBI inflation, such as the world-volume theory of a probe brane in an AdS bulk space-time. In this approach, the weight zero spectator field can be associated with a geometric flat direction in the bulk, and its scale invariance is protected by a shift symmetry.

  5. Flexible Near-Field Nanopatterning with Ultrathin, Conformal Phase Masks on Nonplanar Substrates for Biomimetic Hierarchical Photonic Structures.

    PubMed

    Kwon, Young Woo; Park, Junyong; Kim, Taehoon; Kang, Seok Hee; Kim, Hyowook; Shin, Jonghwa; Jeon, Seokwoo; Hong, Suck Won

    2016-04-26

    Multilevel hierarchical platforms that combine nano- and microstructures have been intensively explored to mimic superior properties found in nature. However, unless directly replicated from biological samples, desirable multiscale structures have been challenging to efficiently produce to date. Departing from conventional wafer-based technology, new and efficient techniques suitable for fabricating bioinspired structures are highly desired to produce three-dimensional architectures even on nonplanar substrates. Here, we report a facile approach to realize functional nanostructures on uneven microstructured platforms via scalable optical fabrication techniques. The ultrathin form (∼3 μm) of a phase grating composed of poly(vinyl alcohol) makes the material physically flexible and enables full-conformal contact with rough surfaces. The near-field optical effect can be identically generated on highly curved surfaces as a result of superior conformality. Densely packed nanodots with submicron periodicity are uniformly formed on microlens arrays with a radius of curvature that is as low as ∼28 μm. Increasing the size of the gratings causes the production area to be successfully expanded by up to 16 in(2). The "nano-on-micro" structures mimicking real compound eyes are transferred to flexible and stretchable substrates by sequential imprinting, facilitating multifunctional optical films applicable to antireflective diffusers for large-area sheet-illumination displays. PMID:26981613

  6. Non-perturbative corrections to the one-loop free energy induced by a massive scalar field on a stationary slowly varying in space gravitational background

    NASA Astrophysics Data System (ADS)

    Kalinichenko, Igor; Kazinski, Peter

    2014-08-01

    The explicit expressions for the one-loop non-perturbative corrections to the gravitational effective action induced by a scalar field on a stationary gravitational background are obtained both at zero and finite temperatures. The perturbative and non-perturbative contributions to the one-loop effective action are explicitly separated. It is proved that, after a suitable renormalization, the perturbative part of the effective action at zero temperature can be expressed in a covariant form solely in terms of the metric and its derivatives. This part coincides with the known large mass expansion of the one-loop effective action. The non-perturbative part of the renormalized one-loop effective action at zero temperature is proved to depend explicitly on the Killing vector defining the vacuum state of quantum fields. This part cannot be expressed in a covariant way through the metric and its derivatives alone. The implications of this result for the structure and symmetries of the effective action for gravity are discussed.

  7. A Novel Approach to Remove Undesired Field Perturbation Effects on Measurements Made in an Antenna Measurement Range

    NASA Astrophysics Data System (ADS)

    Goodman, Scott Alan

    Antenna measurements performed in an indoor measurement range are often impacted by the presence of stray signals within the measurement zone (or quiet zone, QZ). The stray signals may change the location of peaks and nulls or simply change the gain levels in multiple azimuth or elevation angles of the radiation characteristics of the antenna under test (AUT).Using a least squares approach with unknown coefficients and well-defined plane wave basis functions, the probed fields are used to calculate a global plane wave spectra (PWS) for the range. A second matrix equation is then solved using the PWS coefficients to remove the stray signal perturbation effects from a contaminated measurement and calculate the true far-zone radiation pattern. Simulated results are presented for two-dimensional scalar and vector examples, followed by a fully three-dimensional simulation of a realistic range measurement. It was found, and is shown here, that while success was demonstrated in the 2D simulations, numerical instabilities of the mathematical models used in the 3D case led to a breakdown in the model and when more than one plane wave is present. The excellent results in 2D indicate that there is no fundamental deficiency of the method, but the posedness of the 3D problem needs a more thorough investigation.

  8. A compact digital time differential perturbed angular correlation-spectrometer using field programmable gate arrays and various timestamp algorithms.

    PubMed

    Jäger, Markus; Iwig, Kornelius; Butz, Tilman

    2011-06-01

    A user-friendly fully digital time differential perturbed angular correlation (TDPAC)-spectrometer with six detectors and fast digitizers using field programmable gate arrays (FPGA) is described and performance data are given. The new spectrometer has an online data analysis feature, a compact size, and a time resolution such as conventional analog spectrometers. Its calculation intensive part was implemented inside the digitizer. This gives the possibility to change parameters (energy windows, constant fraction trigger delay) and see their influence immediately in the γ-γ correlation diagrams. Tests were performed which showed that the time resolution using a (60)Co source with energy window set at 1.17 MeV and 1.33 MeV is 265 ps with LaBr(3)(Ce) scintillators and 254 ps with BaF(2) scintillators. A true constant fraction algorithm turned out to be slightly better than the constant fraction of amplitude method. The spectrometer performance was tested with a TDPAC measurement using a (44)Ti in rutile source and a positron lifetime measurement using (22)Na. The maximum possible data rate of the spectrometer is 1.1 × 10(6) γ quanta per detector and second. PMID:21721728

  9. A compact digital time differential perturbed angular correlation-spectrometer using field programmable gate arrays and various timestamp algorithms

    SciTech Connect

    Jaeger, Markus; Butz, Tilman; Iwig, Kornelius

    2011-06-15

    A user-friendly fully digital time differential perturbed angular correlation (TDPAC)-spectrometer with six detectors and fast digitizers using field programmable gate arrays (FPGA) is described and performance data are given. The new spectrometer has an online data analysis feature, a compact size, and a time resolution such as conventional analog spectrometers. Its calculation intensive part was implemented inside the digitizer. This gives the possibility to change parameters (energy windows, constant fraction trigger delay) and see their influence immediately in the {gamma}-{gamma} correlation diagrams. Tests were performed which showed that the time resolution using a {sup 60}Co source with energy window set at 1.17 MeV and 1.33 MeV is 265 ps with LaBr{sub 3}(Ce) scintillators and 254 ps with BaF{sub 2} scintillators. A true constant fraction algorithm turned out to be slightly better than the constant fraction of amplitude method. The spectrometer performance was tested with a TDPAC measurement using a {sup 44}Ti in rutile source and a positron lifetime measurement using {sup 22}Na. The maximum possible data rate of the spectrometer is 1.1 x 10{sup 6} {gamma} quanta per detector and second.

  10. Toward a Physically Motivated Force Field: Hydrogen Bond Directionality from a Symmetry-Adapted Perturbation Theory Perspective.

    PubMed

    Tafipolsky, Maxim; Ansorg, Kay

    2016-03-01

    It is argued here that the functional forms adopted in almost all popular force fields are too restrictive to allow for accurate and physics-based parametrization. Some important modifications are suggested based on symmetry-adapted intermolecular perturbation theory, which directly separates the intermolecular interaction energy into four physically interpretable components: electrostatics, exchange-repulsion, dispersion, and induction. The exact electrostatic energy is approximated as a sum of the short-range contribution (due to charge density penetration effects), included explicitly, and the long-range part (via distributed atomic multipoles), whereas the induction energy is evaluated by means of the distributed induced damped point dipole model. The dispersion energy is fitted to a simple analytical function and the exchange-repulsion contribution is approximated by the overlap of the valence-only electron charge densities of monomers. The water dimer is used to illustrate the approach and to discuss its potential and possible improvements. Analysis of the four main contributions to the binding energy allows for a deeper understanding of the hydrogen bond directionality. It is found that a notorious geometrical preference in the water dimer results mainly from large polarization contributions, including induction and dispersion. PMID:26820162

  11. Pions are neither perturbative nor nonperturbative: Wilsonian renormalization-group analysis of nuclear effective field theory including pions

    SciTech Connect

    Harada, Koji; Kubo, Hirofumi; Yamamoto, Yuki

    2011-03-15

    Nuclear effective field theory (NEFT) including pions in the two-nucleon sector is examined from the Wilsonian renormalization group point of view. The pion exchange is cut off at the floating cutoff scale, {Lambda}, with the short-distance part being represented as contact interactions in accordance with the general principle of renormalization. We derive the nonperturbative renormalization group equations in the leading order of the nonrelativistic approximation in the operator space up to including O(p{sup 2}), and find the nontrivial fixed points in the {sup 1}S{sub 0} and {sup 3}S{sub 1}-{sup 3}D{sub 1} channels which are identified with those in the pionless NEFT. The scaling dimensions, which determine the power counting, of the contact interactions at the nontrivial fixed points are also identified with those in the pionless NEFT. We emphasize the importance of the separation of the pion exchange into the short-distance and the long-distance parts, since a part of the former is nonperturbative while the latter is perturbative.

  12. Minimizing the 1/r(2) perturbation for ideal fluence detectors in small source γ-irradiation fields.

    PubMed

    Bielajew, Alex F

    2014-08-21

    A technique for analyzing the effect of the geometrical shape of a source or a detector, using a quadrupole expansion, is described herein. It is shown that this method may be exploited to predict, optimize the geometry of a source, or a measurement device, and nearly eliminate, the departure from the 1/r(2) fall-off characteristic due to irradiation from small sources. We have investigated several simple shapes that have a vanishing Q2 quadrupole moment: a right circular cylinder with a diameter to depth ratio of √[2], a cone with a radius to height ratio of unity, and an oblate ellipsoid with a diameter to depth ratio of √[3/2]. These ideal shapes produce optimally small departures in a 1/r(2) field, nearly mimicking a point-like detector. We have also found a rotationally symmetric shape, intermediate to the other three, that has additionally, a vanishing Q4, the hexadecapole moment. This geometry further improves the 1/r(2)-perturbation characteristics and has an additional free parameter that may be adjusted to model the ideal cylinder, cone or oblate spheroid. PMID:25054611

  13. A compact digital time differential perturbed angular correlation-spectrometer using field programmable gate arrays and various timestamp algorithms

    NASA Astrophysics Data System (ADS)

    Jäger, Markus; Iwig, Kornelius; Butz, Tilman

    2011-06-01

    A user-friendly fully digital time differential perturbed angular correlation (TDPAC)-spectrometer with six detectors and fast digitizers using field programmable gate arrays (FPGA) is described and performance data are given. The new spectrometer has an online data analysis feature, a compact size, and a time resolution such as conventional analog spectrometers. Its calculation intensive part was implemented inside the digitizer. This gives the possibility to change parameters (energy windows, constant fraction trigger delay) and see their influence immediately in the γ-γ correlation diagrams. Tests were performed which showed that the time resolution using a 60Co source with energy window set at 1.17 MeV and 1.33 MeV is 265 ps with LaBr3(Ce) scintillators and 254 ps with BaF2 scintillators. A true constant fraction algorithm turned out to be slightly better than the constant fraction of amplitude method. The spectrometer performance was tested with a TDPAC measurement using a 44Ti in rutile source and a positron lifetime measurement using 22Na. The maximum possible data rate of the spectrometer is 1.1 × 106 γ quanta per detector and second.

  14. Revisiting metric perturbations in tensor-vector-scalar theory

    NASA Astrophysics Data System (ADS)

    Feix, Martin

    2016-05-01

    I revisit cosmological perturbations in Bekenstein's tensor-vector-scalar theory (TeVeS). Considering only scalar modes in the conformal Newtonian gauge, the extra degrees of freedom are expressed in a way suitable for studying modifications at the level of the metric potentials. Assuming a universe in the matter-dominated phase, I discuss the mechanism responsible for boosting structure growth and confirm the vector field as its key ingredient. Using a semianalytic approach, I further characterize the evolution of density perturbations and the potentials on sub- and superhorizon scales.

  15. Joints at high angles to normal fault strike: an explanation using 3-D numerical models of fault-perturbed stress fields

    NASA Astrophysics Data System (ADS)

    Kattenhorn, Simon A.; Aydin, Atilla; Pollard, David D.

    2000-01-01

    Structural methods based on homogeneous stress states predict that joints growing in an extending crust form with strike orientations identical to normal faults. However, we document a field example where the strikes of genetically related normal faults and joints are almost mutually perpendicular. Field relationships allowed us to constrain the fracture sequence and tectonic environment for fault and joint growth. We hypothesize that fault slip can perturb the surrounding stress field in a manner that controls the orientations of induced secondary structures. Numerical models were used to examine the stress field around normal faults, taking into consideration the effects of 3-D fault shape, geometrical arrangement of overlapping faults, and a range of stress states. The calculated perturbed stress fields around model normal faults indicate that it is possible for joints to form at high angles to fault strike. Such joint growth may occur at the lateral tips of an isolated fault, but is most likely in a relay zone between overlapping faults. However, the angle between joints and faults is also influenced by the remote stress state, and is particularly sensitive to the ratio of fault-parallel to fault-perpendicular stress. As this ratio increases, joints can propagate away from faults at increasingly higher angles to fault strike. We conclude that the combined remote stress state and perturbed local stress field associated with overlapping fault geometries resulted in joint growth at high angles to normal fault strike at a field location in Arches National Park, Utah.

  16. Frame independent cosmological perturbations

    SciTech Connect

    Prokopec, Tomislav; Weenink, Jan E-mail: j.g.weenink@uu.nl

    2013-09-01

    We compute the third order gauge invariant action for scalar-graviton interactions in the Jordan frame. We demonstrate that the gauge invariant action for scalar and tensor perturbations on one physical hypersurface only differs from that on another physical hypersurface via terms proportional to the equation of motion and boundary terms, such that the evolution of non-Gaussianity may be called unique. Moreover, we demonstrate that the gauge invariant curvature perturbation and graviton on uniform field hypersurfaces in the Jordan frame are equal to their counterparts in the Einstein frame. These frame independent perturbations are therefore particularly useful in relating results in different frames at the perturbative level. On the other hand, the field perturbation and graviton on uniform curvature hypersurfaces in the Jordan and Einstein frame are non-linearly related, as are their corresponding actions and n-point functions.

  17. Euclidean time formulation for the superstring ensembles: Perturbative canonical ensemble with Neveu-Schwarz B -field backgrounds

    NASA Astrophysics Data System (ADS)

    Chaudhuri, Shyamoli

    2014-12-01

    We derive the Euclidean time formulation for the equilibrium canonical ensemble of the type IIA and type IIB superstrings, and the spin(32 )/Z2 heterotic string. We compactify on R8×T2 , and twist by the Neveu-Schwarz sector antisymmetric 2-form B -field potential, spontaneously breaking supersymmetry at low temperatures, while preserving the tachyon-free low-energy gravitational field theory limit. We verify that the super partners of the massless dilaton-graviton multiplet obtain a mass which is linear in the temperature. In addition, we show that the free energy for the superstring canonical ensemble at weak coupling is always strongly convergent in the ultraviolet, high-temperature, regime dominated by the highest mass level number states. We derive the precise form of the exponential suppression as a linear power of the mass level, which erases the exponential Hagedorn growth of the degeneracies as the square root of mass level number. Finally, we close a gap in previous research giving an unambiguous derivation of the normalization of the one-loop vacuum energy density of the spin(32 )/Z2 perturbative heterotic string theory. Invoking the O(32) type IB-heterotic strong-weak duality, we match the normalization of the one loop vacuum energy densities of the T -dual O(32) type IA open and closed string with that of the spin(32 )/Z2 heterotic string on R9×S1 , for values of the compactification radius, R[O (32 )] , RIB≫ α'1 /2 , with RIA<α'1 /2 . We show that the type IA thermal solitonic winding spectrum is a simple model for finite temperature pure QCD, transitioning above the critical duality phase transformation temperature to the deconfined ensemble of thermally excited IB gluons.

  18. Monte Carlo simulations of patient dose perturbations in rotational-type radiotherapy due to a transverse magnetic field: A tomotherapy investigation

    SciTech Connect

    Yang, Y. M.; Geurts, M.; Smilowitz, J. B.; Bednarz, B. P.; Sterpin, E.

    2015-02-15

    Purpose: Several groups are exploring the integration of magnetic resonance (MR) image guidance with radiotherapy to reduce tumor position uncertainty during photon radiotherapy. The therapeutic gain from reducing tumor position uncertainty using intrafraction MR imaging during radiotherapy could be partially offset if the negative effects of magnetic field-induced dose perturbations are not appreciated or accounted for. The authors hypothesize that a more rotationally symmetric modality such as helical tomotherapy will permit a systematic mediation of these dose perturbations. This investigation offers a unique look at the dose perturbations due to homogeneous transverse magnetic field during the delivery of Tomotherapy{sup ®} Treatment System plans under varying degrees of rotational beamlet symmetry. Methods: The authors accurately reproduced treatment plan beamlet and patient configurations using the Monte Carlo code GEANT4. This code has a thoroughly benchmarked electromagnetic particle transport physics package well-suited for the radiotherapy energy regime. The three approved clinical treatment plans for this study were for a prostate, head and neck, and lung treatment. The dose heterogeneity index metric was used to quantify the effect of the dose perturbations to the target volumes. Results: The authors demonstrate the ability to reproduce the clinical dose–volume histograms (DVH) to within 4% dose agreement at each DVH point for the target volumes and most planning structures, and therefore, are able to confidently examine the effects of transverse magnetic fields on the plans. The authors investigated field strengths of 0.35, 0.7, 1, 1.5, and 3 T. Changes to the dose heterogeneity index of 0.1% were seen in the prostate and head and neck case, reflecting negligible dose perturbations to the target volumes, a change from 5.5% to 20.1% was observed with the lung case. Conclusions: This study demonstrated that the effect of external magnetic fields can

  19. Monte Carlo simulations of patient dose perturbations in rotational-type radiotherapy due to a transverse magnetic field: A tomotherapy investigation

    PubMed Central

    Yang, Y. M.; Geurts, M.; Smilowitz, J. B.; Sterpin, E.; Bednarz, B. P.

    2015-01-01

    Purpose: Several groups are exploring the integration of magnetic resonance (MR) image guidance with radiotherapy to reduce tumor position uncertainty during photon radiotherapy. The therapeutic gain from reducing tumor position uncertainty using intrafraction MR imaging during radiotherapy could be partially offset if the negative effects of magnetic field-induced dose perturbations are not appreciated or accounted for. The authors hypothesize that a more rotationally symmetric modality such as helical tomotherapy will permit a systematic mediation of these dose perturbations. This investigation offers a unique look at the dose perturbations due to homogeneous transverse magnetic field during the delivery of Tomotherapy® Treatment System plans under varying degrees of rotational beamlet symmetry. Methods: The authors accurately reproduced treatment plan beamlet and patient configurations using the Monte Carlo code geant4. This code has a thoroughly benchmarked electromagnetic particle transport physics package well-suited for the radiotherapy energy regime. The three approved clinical treatment plans for this study were for a prostate, head and neck, and lung treatment. The dose heterogeneity index metric was used to quantify the effect of the dose perturbations to the target volumes. Results: The authors demonstrate the ability to reproduce the clinical dose–volume histograms (DVH) to within 4% dose agreement at each DVH point for the target volumes and most planning structures, and therefore, are able to confidently examine the effects of transverse magnetic fields on the plans. The authors investigated field strengths of 0.35, 0.7, 1, 1.5, and 3 T. Changes to the dose heterogeneity index of 0.1% were seen in the prostate and head and neck case, reflecting negligible dose perturbations to the target volumes, a change from 5.5% to 20.1% was observed with the lung case. Conclusions: This study demonstrated that the effect of external magnetic fields can be

  20. From monolayer to multilayer N-channel polymeric field-effect transistors with precise conformational order.

    PubMed

    Fabiano, Simone; Musumeci, Chiara; Chen, Zhihua; Scandurra, Antonino; Wang, He; Loo, Yueh-Lin; Facchetti, Antonio; Pignataro, Bruno

    2012-02-14

    Monolayer field-effect transistors based on a high-mobility n-type polymer are demonstrated. The accurate control of the long-range order by Langmuir-Schäfer (LS) deposition yields dense polymer packing exhibiting good injection properties, relevant current on/off ratio and carrier mobility in a staggered configuration. Layer-by-layer LS film transistors of increasing thickness are fabricated and their performance compared to those of spin-coated films. PMID:22250060

  1. Electron contamination and build-up doses in conformal radiotherapy fields.

    PubMed

    Hounsell, A R; Wilkinson, J M

    1999-01-01

    The dose in the build-up region depends upon the primary photon beam, backscattered radiation from the patient and contamination radiation from outside the patient. In this paper, a model based on measured data is proposed which allows the build-up dose for arbitrarily shaped treatment fields to be determined. The dose in the build-up region is assumed to comprise a primary photon component and a contamination component that is a function of the field size and shape. This contamination component, for modelling purposes, is subdivided into contributions that correspond to elements of 1 cm by 1 cm cross-sectional area at the plane of the isocentre. The magnitude of these components has been obtained by fitting measured data to an exponential function. The exponent was found to vary linearly with depth for energies between 4 MV and 20 MV. The coefficient decreased linearly with depth at 4, 6 and 8 MV, but exhibited a broad build-up region at 20 MV. The primary component, in the build-up region, could be approximated by a 100 - (100 - PSD) e(-mu d) function, where PSD is the primary surface dose. The values obtained during the fitting procedure were used to calculate dose in the build-up region for arbitrarily shaped fields. Good agreement was found in each case. PMID:10071874

  2. Temperature dependence of electric field gradient in LaCoO3 perovskite investigated by perturbed angular correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Junqueira, Astrogildo C.; Carbonari, Artur W.; Saxena, Rajendra N.; Mestnik-Filho, José; Dogra, Rakesh

    2005-11-01

    The time differential perturbed angular correlation (TDPAC) technique was used to study the temperature dependence of electric field gradient (EFG) in LaCoO3 perovskite using {}^{111}\\mathrm {In}\\rightarrow {}^{111}\\mathrm {Cd} and {}^{181}\\mathrm {Hf} \\rightarrow {}^{181}\\mathrm {Ta} nuclear probes. The radioactive parent nuclei 111In and 181Hf were introduced into the oxide lattice through a chemical process during sample preparation and were found to occupy only the Co sites in LaCoO3. The PAC measurements with 111Cd and 181Ta probes were made in the temperature range of 4.2-1146 K and 4.2-1004 K, respectively. No long-range magnetic order was observed up to 4.2 K. The EFGs at 111Cd and 181Ta show very similar temperature dependences. They increase slowly between 4.2 and about 77 K and then decrease almost linearly with increasing temperature until about 500-600 K, where a broad peak-like structure is observed, followed by linear decrease at still higher temperatures. These discontinuities at about 77 K and 500-600 K have been interpreted as thermally activated spin state transitions from the low-spin (t2g6eg0) ground state configuration to the intermediate-spin (t2g5eg1) state and from the intermediate-spin to the high-spin (t2g4eg2) state of the Co3+ ion, confirming previous observation in other recent studies. An indication of a Jahn-Teller distortion, which stabilizes the intermediate-spin state with orbital ordering, is also pointed out.

  3. Higher Spin Interactions from Conformal Field Theory: The Complete Cubic Couplings

    NASA Astrophysics Data System (ADS)

    Sleight, Charlotte; Taronna, Massimo

    2016-05-01

    In this Letter we provide a complete holographic reconstruction of the cubic couplings in the minimal bosonic higher spin theory in (d +1 )-dimensional anti- de Sitter space. For this purpose, we also determine the operator-product expansion coefficients of all single-trace conserved currents in the d -dimensional free scalar O (N ) vector model, and we compute the tree-level three-point Witten diagram amplitudes for a generic cubic interaction of higher spin gauge fields in the metriclike formulation.

  4. Higher Spin Interactions from Conformal Field Theory: The Complete Cubic Couplings.

    PubMed

    Sleight, Charlotte; Taronna, Massimo

    2016-05-01

    In this Letter we provide a complete holographic reconstruction of the cubic couplings in the minimal bosonic higher spin theory in (d+1)-dimensional anti- de Sitter space. For this purpose, we also determine the operator-product expansion coefficients of all single-trace conserved currents in the d-dimensional free scalar O(N) vector model, and we compute the tree-level three-point Witten diagram amplitudes for a generic cubic interaction of higher spin gauge fields in the metriclike formulation. PMID:27203314

  5. Fisher–Hartwig determinants, conformal field theory and universality in generalised XX models

    NASA Astrophysics Data System (ADS)

    Hutchinson, J.; Jones, N. G.

    2016-07-01

    We discuss certain quadratic models of spinless fermions on a 1D lattice, and their corresponding spin chains. These were studied by Keating and Mezzadri in the context of their relation to the Haar measures of the classical compact groups. We show how these models correspond to translation invariant models on an infinite or semi-infinite chain, which in the simplest case reduce to the familiar XX model. We give physical context to mathematical results for the entanglement entropy, and calculate the spin–spin correlation functions using the Fisher–Hartwig conjecture. These calculations rigorously demonstrate universality in classes of these models. We show that these are in agreement with field theoretic and renormalization group arguments that we provide.

  6. Conformal dilaton gravity: Classical noninvariance gives rise to quantum invariance

    NASA Astrophysics Data System (ADS)

    Álvarez, Enrique; González-Martín, Sergio; Martín, Carmelo P.

    2016-03-01

    When quantizing conformal dilaton gravity, there is a conformal anomaly which starts at two-loop order. This anomaly stems from evanescent operators on the divergent parts of the effective action. The general form of the finite counterterm, which is necessary in order to insure cancellation of the Weyl anomaly to every order in perturbation theory, has been determined using only conformal invariance. Those finite counterterms do not have any inverse power of any mass scale in front of them (precisely because of conformal invariance), and then they are not negligible in the low-energy deep infrared limit. The general form of the ensuing modifications to the scalar field equation of motion has been determined, and some physical consequences have been extracted.

  7. A VLT VIMOS integral-field spectroscopic study of perturbed blue compact galaxies: UM 420 and UM 462

    NASA Astrophysics Data System (ADS)

    James, B. L.; Tsamis, Y. G.; Barlow, M. J.

    2010-01-01

    We report on optical integral-field spectroscopy of two unrelated blue compact galaxies mapped with the 13× 13 arcsec2 Visible Multi-Object Spectrograph integral field unit at a resolution of 0.33× 0.33 arcsec2. Continuum and background subtracted emission line maps in the light of [OIII] λ5007, Hα and [NII] λ6584 are presented. Both galaxies display signs of ongoing perturbation and/or interaction. UM 420 is resolved for the first time to be a merging system composed of two starbursting components with an `arm-like' structure associated with the largest component. UM 462 which is a disrupted system of irregular morphology is resolved into at least four starbursting regions. Maps of the Hα radial velocity and full width at half-maximum are discussed. No underlying broad-line region was detected from either galaxy as the emission lines are well fitted with single Gaussian profiles only. Electron temperatures and densities as well as the abundances of helium, oxygen, nitrogen and sulphur were computed from spectra integrated over the whole galaxies and for each area of recent star formation. Maps of the O/H ratio are presented: these galaxies show oxygen abundances that are ~20 per cent solar. No evidence of substantial abundance variations across the galaxies that would point to significant nitrogen or oxygen self-enrichment is found (<~0.2 dex limit). Contrary to previous observations, this analysis does not support the classification of these blue compact dwarf galaxies as Wolf-Rayet galaxies as the characteristic broad-emission-line features have not been detected in our spectra. Baldwin-Phillips-Terlevich emission-line-ratio diagrams which were constructed on a pixel-by-pixel basis indicate that the optical spectra of these systems are predominantly excited by stellar photoionization. Based on observations collected at the European Southern Observatory (ESO), Chile, under programmes 078.B-0353(B, E). E-mail: bj@star.ucl.ac.uk

  8. The conformational state of polyphenol oxidase from field bean (Dolichos lablab) upon SDS and acid-pH activation.

    PubMed

    Kanade, Santosh R; Paul, Beena; Rao, A G Appu; Gowda, Lalitha R

    2006-05-01

    Field bean (Dolichos lablab) contains a single isoform of PPO (polyphenol oxidase)--a type III copper protein that catalyses the o-hydroxylation of monophenols and oxidation of o-diphenols using molecular oxygen--and is a homotetramer with a molecular mass of 120 kDa. The enzyme is activated manyfold either in the presence of the anionic detergent SDS below its critical micellar concentration or on exposure to acid-pH. The enhancement of kcat upon activation is accompanied by a marked shift in the pH optimum for the oxidation of t-butyl catechol from 4.5 to 6.0, an increased sensitivity to tropolone, altered susceptibility to proteolytic degradation and decreased thermostability. The Stokes radius of the native enzyme is found to increase from 49.1+/-2 to 75.9+/-0.6 A (1 A=0.1 nm). The activation by SDS and acid-pH results in a localized conformational change that is anchored around the catalytic site of PPO that alters the microenvironment of an essential glutamic residue. Chemical modification of field bean and sweet potato PPO with 1-ethyl-3-(3-dimethylaminopropyl)carbodi-imide followed by kinetic analysis leads to the conclusion that both the enzymes possess a core carboxylate essential to activity. This enhanced catalytic efficiency of PPO, considered as an inducible defence oxidative enzyme, is vital to the physiological defence strategy adapted by plants to insect herbivory and pathogen attack. PMID:16393141

  9. Exposures involving perturbations of the EM field have non-linear effects on radiation response and can alter the expression of radiation induced bystander effects

    NASA Astrophysics Data System (ADS)

    Mothersill, Carmel; Seymour, Colin

    2012-07-01

    Our recent data suggest there is a physical component to the bystander signal induced by radiation exposure and that alternative medicine techniques such as Reiki and acupuncture or exposures to weak EM fields alter the response of cells to direct irradiation and either altered bystander signal production or altered the response of cells receiving bystander signals. Our proposed mechanism to explain these findings is that perturbation of electromagnetic (EM) fields is central to the induction of low radiation dose responses especially non-targeted bystander effects. In this presentation we review the alternative medicine data and other data sets from our laboratory which test our hypothesis that perturbation of bio-fields will modulate radiation response in the low dose region. The other data sets include exposure to MRI, shielding using lead and or Faraday cages, the use of physical barriers to bystander signal transmission and the use of membrane channel blockers. The data taken together strongly suggest that EM field perturbation can modulate low dose response and that in fact the EM field rather than the targeted deposition of ionizing energy in the DNA may be the key determinant of dose response in a cell or organism The results also lead us to suspect that at least when chemical transmission is blocked, bystander signals can be transmitted by other means. Our recent experiments suggest light signals and volatiles are not likely. We conclude that alternative medicine and other techniques involving electromagnetic perturbations can modify the response of cells to low doses of ionizing radiation and can induce bystander effects similar to those seen in medium transfer experiments. In addition to the obvious implications for mechanistic studies of low dose effects, this could perhaps provide a novel target to exploit in space radiation protection and in optimizing therapeutic gain during radiotherapy.

  10. Tokamak plasma high field side response to an n = 3 magnetic perturbation: a comparison of 3D equilibrium solutions from seven different codes

    NASA Astrophysics Data System (ADS)

    Reiman, A.; Ferraro, N. M.; Turnbull, A.; Park, J. K.; Cerfon, A.; Evans, T. E.; Lanctot, M. J.; Lazarus, E. A.; Liu, Y.; McFadden, G.; Monticello, D.; Suzuki, Y.

    2015-06-01

    In comparing equilibrium solutions for a DIII-D shot that is amenable to analysis by both stellarator and tokamak three-dimensional (3D) equilibrium codes, a significant disagreement has been seen between solutions of the VMEC stellarator equilibrium code and solutions of tokamak perturbative 3D equilibrium codes. The source of that disagreement has been investigated, and that investigation has led to new insights into the domain of validity of the different equilibrium calculations, and to a finding that the manner in which localized screening currents at low order rational surfaces are handled can affect global properties of the equilibrium solution. The perturbative treatment has been found to break down at surprisingly small perturbation amplitudes due to overlap of the calculated perturbed flux surfaces, and that treatment is not valid in the pedestal region of the DIII-D shot studied. The perturbative treatment is valid, however, further into the interior of the plasma, and flux surface overlap does not account for the disagreement investigated here. Calculated equilibrium solutions for simple model cases and comparison of the 3D equilibrium solutions with those of other codes indicate that the disagreement arises from a difference in handling of localized currents at low order rational surfaces, with such currents being absent in VMEC and present in the perturbative codes. The significant differences in the global equilibrium solutions associated with the presence or absence of very localized screening currents at rational surfaces suggests that it may be possible to extract information about localized currents from appropriate measurements of global equilibrium plasma properties. That would require improved diagnostic capability on the high field side of the tokamak plasma, a region difficult to access with diagnostics.

  11. LINEAR INVERSION OF TRANSMITTED ACOUSTIC WAVE FIELDS FOR THREE-DIMENSIONAL MODULUS AND DENSITY PERTURBATIONS USING A BORN-TYPE APPROXIMATION.

    USGS Publications Warehouse

    Stauber, Douglas A.

    1985-01-01

    A Born approximation is used to linearize the relationship, in the horizontal-wavenumber and frequency domains, between lateral perturbations of modulus and density in a layered half-space and the acoustic wave field observed at the surface when a plane wave is incident from below. The resulting equations can be used to perform a linear inversion of observed acoustic wave fields to obtain lateral perturbations in modulus and density. Since modulus and density effects are separated, gravity observations can be included in the inversion procedure without any assumptions about the relationship between density and acoustic velocity. Tests with synthetic data sets reveal that the inversion method gives useful results when the spatial scales of the inhomogeneities are smaller than several acoustic wavelengths. Refs.

  12. Conformal frame dependence of inflation

    NASA Astrophysics Data System (ADS)

    Domènech, Guillem; Sasaki, Misao

    2015-04-01

    Physical equivalence between different conformal frames in scalar-tensor theory of gravity is a known fact. However, assuming that matter minimally couples to the metric of a particular frame, which we call the matter Jordan frame, the matter point of view of the universe may vary from frame to frame. Thus, there is a clear distinction between gravitational sector (curvature and scalar field) and matter sector. In this paper, focusing on a simple power-law inflation model in the Einstein frame, two examples are considered; a super-inflationary and a bouncing universe Jordan frames. Then we consider a spectator curvaton minimally coupled to a Jordan frame, and compute its contribution to the curvature perturbation power spectrum. In these specific examples, we find a blue tilt at short scales for the super-inflationary case, and a blue tilt at large scales for the bouncing case.

  13. Galilean conformal electrodynamics

    NASA Astrophysics Data System (ADS)

    Bagchi, Arjun; Basu, Rudranil; Mehra, Aditya

    2014-11-01

    Maxwell's Electrodynamics admits two distinct Galilean limits called the Electric and Magnetic limits. We show that the equations of motion in both these limits are invariant under the Galilean Conformal Algebra in D = 4, thereby exhibiting non-relativistic conformal symmetries. Remarkably, the symmetries are infinite dimensional and thus Galilean Electrodynamics give us the first example of an infinitely extended Galilean Conformal Field Theory in D > 2. We examine details of the theory by looking at purely non-relativistic conformal methods and also use input from the limit of the relativistic theory.

  14. Effect of n = 3 perturbation field amplitudes below the ELM triggering threshold on edge and SOL transport in NSTX

    SciTech Connect

    J. M. Canik; Lore, J. D.; Ahn, J. -W.; Bortolon, A.; Fredrickson, E. D.; Jaworski, M. A.; Kramer, G. J.; Maingi, R.; McLean, A. G.; Scotti, F.; Soukhanovskii, V. A.; Tritz, K.

    2013-01-12

    Here, the pulsed application of n = 3 magnetic perturbation fields with amplitudes below that which triggers ELMs results in distinct, transient responses observable on several edge and divertor diagnostics in NSTX. We refer to these responses as Sub-Threshold Edge Perturbations (STEPs). An analysis of edge measurements suggests that STEPs result in increased transport in the plasma edge and scrape-off layer, which leads to augmentation of the intrinsic strike point splitting due to error fields, i.e., an intensification of the helical divertor footprint flux pattern. These effects are much smaller in magnitude than those of triggered ELMs, and are observed for the duration of the field perturbation measured internal to the vacuum vessel. In addition, STEPs are correlated with changes to the MHD activity, along with transient reductions in the neutron production rate. Ideally the STEPs could be used to provide density control and prevent impurity accumulation, in the same manner that on-demand ELM triggering is used on NSTX, without the impulsive divertor fluxes and potential for damage to plasma facing components associated with ELMs.

  15. Hamilton/Jacobi perturbation methods applied to the rotational motion of a rigid body in a gravitational field

    NASA Technical Reports Server (NTRS)

    Fitzpatrick, P. M.; Harmon, G. R.; Liu, J. J. F.; Cochran, J. E.

    1974-01-01

    The formalism for studying perturbations of a triaxial rigid body within the Hamilton-Jacobi framework is developed. The motion of a triaxial artificial earth satellite about its center of mass is studied. Variables are found which permit separation, and the Euler angles and associated conjugate momenta are obtained as functions of canonical constants and time.

  16. Analytical method for perturbed frozen orbit around an asteroid in highly inhomogeneous gravitational fields: a first approach

    NASA Astrophysics Data System (ADS)

    Ceccaroni, Marta; Biscani, Francesco; Biggs, James

    2014-01-01

    This article provides a method for finding initial conditions for perturbed frozen orbits around inhomogeneous fast rotating asteroids. These orbits can be used as reference trajectories in missions that require close inspection of any rigid body. The generalized perturbative procedure followed exploits the analytical methods of relegation of the argument of node and Delaunay normalisation to arbitrary order. These analytical methods are extremely powerful but highly computational. The gravitational potential of the heterogeneous body is firstly stated, in polar-nodal coordinates, which takes into account the coefficients of the spherical harmonics up to an arbitrary order. Through the relegation of the argument of node and the Delaunay normalization, a series of canonical transformations of coordinates is found, which reduces the Hamiltonian describing the system to a integrable, two degrees of freedom Hamiltonian plus a truncated reminder of higher order. Setting eccentricity, argument of pericenter and inclination of the orbit of the truncated system to be constant, initial conditions are found, which evolve into frozen orbits for the truncated system. Using the same initial conditions yields perturbed frozen orbits for the full system, whose perturbation decreases with the consideration of arbitrary homologic equations in the relegation and normalization procedures. Such procedure can be automated for the first homologic equation up to the consideration of any arbitrary number of spherical harmonics coefficients. The project has been developed in collaboration with the European Space Agency (ESA).

  17. Plasma Density and Electro-Magnetic Field Perturbations Hf-Induced in the Outer Ionosphere: Review of Experimental Results

    NASA Astrophysics Data System (ADS)

    Frolov, Vladimir; Rauch, Jean-Louis; Parrot, Michel; Rapoport, Victor; Shorokhova, Elena

    In the report we consider features of plasma density and electro-magnetic field perturbations induced in the Earth’s outer ionosphere by modification of F _{2} region by O-mode powerful HF radio waves radiated by the SURA heating facility. Experiments presented were carried out in 2005 - 2010. Plasma density perturbations were detected at altitudes of about of 700 km by instruments onboard the French DEMETER satellite when it intersected the disturbed magnetic flux tube. The formation of artificial HF-induced plasma density ducts in the outer ionosphere is a central discovery, which was made during the SURA-DEMETER experiments [1,2]. Analysis of experimental data available makes it possible to formulate ducts features and point out the conditions under which the formation of such ducts takes place. 1. Under night conditions ducts are characterized by the increased plasma density in the range from 20% to 80% relatively to its background value. As this takes place, the excess in the plasma ion component is due to O (+) ions dominating at altitudes of about 700 km, whereas the densities of lower mass H (+) and He ({+) } ions typically decrease by a percentage amount that is much more the relative increase in the density of O (+) ions. The duct formation was never observed under daytime conditions. According to [3] the HF-induced ducts were observed by ionosphere pumping in morning and evening hours but in these cases their intensity was no more than a few percentages. 2. The size of the ducts along the satellite orbits is of about 80 - 100 km. It is a reason why such ducts can be observed only if the minimal distance between the satellite and the center of the heated flux tube is less than 50 km. 3. The formation of ducts is observed only if the effective radiated power is more than 40 MW. For the SURA facility, to heat the ionosphere at higher efficiency due to the “magnetic-zenith effect”, the HF beam is often inclined by 12 - 16(°) southward. 4. The pump

  18. Three-dimensional simulation and analysis of heat transfer and flow field in micro-floating zone of LHPG with asymmetrical perturbation

    NASA Astrophysics Data System (ADS)

    Chen, Peng-Yi; Huang, En-Ping; Lo, Chia-Yao

    2012-12-01

    Under symmetrical conditions, the micro-floating zone of a laser-heated pedestal growth (LHPG) system displays a symmetrical double eddy flow field distribution. However, as the perturbation increases, the double eddy flow field distribution changes from symmetry to tilt, resulting in unstable flow field vibration. This study investigated the influence of the molten zone on the shape (at vapor-liquid and solid-liquid interfaces) and flow field distribution resulting from tilting the CO2 laser heating ring and the gravity field. This tilt is caused by spatial perturbations resulting from mounting the source rod and seed on pedestals with an alignment that slightly deviates from the growth axis of the LHPG system. The feasibility of growing crystal fibers using the micro-floating zone of the LHPG in the horizontal plane was further investigated. After selecting YAG as the growth material, we evaluated various reduction ratios, source rod scales, surface tensions, and thermocapillary coefficients for the two types of perturbation. Deviation in the laser heating ring significantly influenced the solid-liquid interface and the symmetry of the flow field in the molten zone. However, as long as the laser heating ring remained close to symmetrical, the influence on the molten zone of the larger deviation in the gravity field was limited. Therefore, growing crystal fibers using the micro-floating zone of the LHPG system in the horizontal plane is possible for materials that possess the correct physical properties at appropriate source rod scales. The three-dimensional simulation of this asymmetry includes the effects of the diameter reduction ratio and laser heating, and also modifies Lan's thermocapillary floating numerical model. The modified model calculates the physical grid through a non-orthogonal body-fitting grid transformation using the control-volume finite-difference method. To enhance the simulation and represent the physical system more accurately, we compared

  19. Time evolutions of scalar field perturbations in D-dimensional Reissner-Nordström Anti-de Sitter black holes

    NASA Astrophysics Data System (ADS)

    Li, Ran; Zhang, Hongbao; Zhao, Junkun

    2016-07-01

    Reissner-Nordström Anti-de Sitter (RNAdS) black holes are unstable against the charged scalar field perturbations due to the well-known superradiance phenomenon. We present the time domain analysis of charged scalar field perturbations in the RNAdS black hole background in general dimensions. We show that the instabilities of charged scalar field can be explicitly illustrated from the time profiles of evolving scalar field. By using the Prony method to fit the time evolution data, we confirm the mode that dominates the long time behavior of scalar field is in accordance with the quasinormal mode from the frequency domain analysis. The superradiance origin of the instability can also be demonstrated by comparing the real part of the dominant mode with the superradiant condition of charged scalar field. It is shown that all the unstable modes are superradiant, which is consistent with the analytical result in the frequency domain analysis. Furthermore, we also confirm there exists the rapid exponential growing modes in the RNAdS case, which makes the RNAdS black hole a good test ground to investigate the nonlinear evolution of superradiant instability.

  20. The conformational state of polyphenol oxidase from field bean (Dolichos lablab) upon SDS and acid-pH activation

    PubMed Central

    Kanade, Santosh R.; Paul, Beena; Rao, A. G. Appu; Gowda, Lalitha R.

    2006-01-01

    Field bean (Dolichos lablab) contains a single isoform of PPO (polyphenol oxidase) – a type III copper protein that catalyses the o-hydroxylation of monophenols and oxidation of o-diphenols using molecular oxygen – and is a homotetramer with a molecular mass of 120 kDa. The enzyme is activated manyfold either in the presence of the anionic detergent SDS below its critical micellar concentration or on exposure to acid-pH. The enhancement of kcat upon activation is accompanied by a marked shift in the pH optimum for the oxidation of t-butyl catechol from 4.5 to 6.0, an increased sensitivity to tropolone, altered susceptibility to proteolytic degradation and decreased thermostability. The Stokes radius of the native enzyme is found to increase from 49.1±2 to 75.9±0.6 Å (1 Å=0.1 nm). The activation by SDS and acid-pH results in a localized conformational change that is anchored around the catalytic site of PPO that alters the microenvironment of an essential glutamic residue. Chemical modification of field bean and sweet potato PPO with 1-ethyl-3-(3-dimethylaminopropyl)carbodi-imide followed by kinetic analysis leads to the conclusion that both the enzymes possess a core carboxylate essential to activity. This enhanced catalytic efficiency of PPO, considered as an inducible defence oxidative enzyme, is vital to the physiological defence strategy adapted by plants to insect herbivory and pathogen attack. PMID:16393141

  1. SU-E-T-242: Monte Carlo Simulations Used to Test the Perturbation of a Reference Ion Chamber Prototype Used for Small Fields

    SciTech Connect

    Vazquez Quino, L; Calvo, O; Huerta, C; DeWeese, M

    2014-06-01

    Purpose: To study the perturbation due to the use of a novel Reference Ion Chamber designed to measure small field dosimetry (KermaX Plus C by IBA). Methods: Using the Phase-space files for TrueBeam photon beams available by Varian in IAEA-compliant format for 6 and 15 MV. Monte Carlo simulations were performed using BEAMnrc and DOSXYZnrc to investigate the perturbation introduced by a reference chamber into the PDDs and profiles measured in water tank. Field sizes ranging from 1×1, 2×2,3×3, 5×5 cm2 were simulated for both energies with and without a 0.5 mm foil of Aluminum which is equivalent to the attenuation equivalent of the reference chamber specifications in a water phantom of 30×30×30 cm3 and a pixel resolution of 2 mm. The PDDs, profiles, and gamma analysis of the simulations were performed as well as a energy spectrum analysis of the phase-space files generated during the simulation. Results: Examination of the energy spectrum analysis performed shown a very small increment of the energy spectrum at the build-up region but no difference is appreciated after dmax. The PDD, profiles and gamma analysis had shown a very good agreement among the simulations with and without the Al foil, with a gamma analysis with a criterion of 2% and 2mm resulting in 99.9% of the points passing this criterion. Conclusion: This work indicates the potential benefits of using the KermaX Plus C as reference chamber in the measurement of PDD and Profiles for small fields since the perturbation due to in the presence of the chamber the perturbation is minimal and the chamber can be considered transparent to the photon beam.

  2. Dosimetric Comparison Between Intensity-Modulated with Coplanar Field and 3D Conformal Radiotherapy with Noncoplanar Field for Postocular Invasion Tumor

    SciTech Connect

    Tu Wenyong; Liu Lu Zeng Jun; Yin Weidong; Li Yun

    2010-07-01

    This study presents a dosimetric optimization effort aiming to compare noncoplanar field (NCF) on 3 dimensions conformal radiotherapy (3D-CRT) and coplanar field (CF) on intensity-modulated radiotherapy (IMRT) planning for postocular invasion tumor. We performed a planning study on the computed tomography data of 8 consecutive patients with localized postocular invasion tumor. Four fields NCF 3D-CRT in the transverse plane with gantry angles of 0-10 deg., 30-45 deg., 240-270 deg., and 310-335 deg. degrees were isocentered at the center of gravity of the target volume. The geometry of the beams was determined by beam's eye view. The same constraints were prepared with between CF IMRT optimization and NCF 3D-CRT treatment. The maximum point doses (D max) for the different optic pathway structures (OPS) with NCF 3D-CRT treatment should differ in no more than 3% from those with the NCF IMRT plan. Dose-volume histograms (DVHs) were obtained for all targets and organ at risk (OAR) with both treatment techniques. Plans with NCF 3D-CRT and CF IMRT constraints on target dose in homogeneity were computed, as well as the conformity index (CI) and homogeneity index (HI) in the target volume. The PTV coverage was optimal with both NCF 3D-CRT and CF IMRT plans in the 8 tumor sites. No difference was noted between the two techniques for the average D{sub max} and D{sub min} dose. NCF 3D-CRT and CF IMRT will yield similar results on CI. However, HI was a significant difference between NCF 3D-CRT and CF IMRT plan (p < 0.001). Physical endpoints for target showed the mean target dose to be low in the CF IMRT plan, caused by a large target dose in homogeneity (p < 0.001). The impact of NCF 3D-CRT versus CF IMRT set-up is very slight. NCF3D-CRT is one of the treatment options for postocular invasion tumor. However, constraints for OARs are needed.

  3. Entanglement temperature and perturbed AdS3 geometry

    NASA Astrophysics Data System (ADS)

    Levine, G. C.; Caravan, B.

    2016-06-01

    Generalizing the first law of thermodynamics, the increase in entropy density δ S (x ) of a conformal field theory (CFT) is proportional to the increase in energy density, δ E (x ) , of a subsystem divided by a spatially dependent entanglement temperature, TE(x ) , a fixed parameter determined by the geometry of the subsystem, crossing over to thermodynamic temperature at high temperatures. In this paper we derive a generalization of the thermodynamic Clausius relation, showing that deformations of the CFT by marginal operators are associated with spatial temperature variations, δ TE(x ) , and spatial energy correlations play the role of specific heat. Using AdS/CFT duality we develop a relationship between a perturbation in the local entanglement temperature of the CFT and the perturbation of the bulk AdS metric. In two dimensions, we demonstrate a method through which direct diagonalizations of the boundary quantum theory may be used to construct geometric perturbations of AdS3 .

  4. A study on quantitative analysis of field size and dose by using gating system in 4D conformal radiation treatment

    NASA Astrophysics Data System (ADS)

    Ji, Youn-Sang; Dong, Kyung-Rae; Kim, Chang-Bok; Chung, Woon-Kwan; Cho, Jae-Hwan; Lee, Hae-Kag

    2012-10-01

    This study evaluated the gating-based 4-D conformal radiation therapy (4D-CT) treatment planning by a comparison with the common 3-D conformal radiation therapy (3D-CT) treatment planning and examined the change in treatment field size and dose to the tumors and adjacent normal tissues because an unnecessary dose is also included in the 3-D treatment planning for the radiation treatment of tumors in the chest and abdomen. The 3D-CT and gating-based 4D-CT images were obtained from patients who had undergone radiation treatment for chest and abdomen tumors in the oncology department. After establishing a treatment plan, the CT treatment and planning system were used to measure the change in field size for analysis. A dose volume histogram (DVH) was used to calculate the appropriate dose to planning target volume (PTV) tumors and adjacent normal tissue. The difference in the treatment volume of the chest was 0.6 and 0.83 cm on the X- and Y-axis, respectively, for the gross tumor volume (GTV). Accordingly, the values in the 4D-CT treatment planning were smaller and the dose was more concentrated by 2.7% and 0.9% on the GTV and clinical target volume (CTV), respectively. The normal tissues in the surrounding normal tissues were reduced by 3.0%, 7.2%, 0.4%, 1.7%, 2.6% and 0.2% in the bronchus, chest wall, esophagus, heart, lung and spinal cord, respectively. The difference in the treatment volume of the abdomen was 0.72 cm on the X-axis and 0.51 cm on the Y-axis for the GTV; and 1.06 cm on the X-axis and 1.85 cm on the Y-axis for the PTV. Therefore, the values in the 4D-CT treatment planning were smaller. The dose was concentrated by 6.8% and 4.3% on the GTV and PTV, respectively, whereas the adjacent normal tissues in the cord, Lt. kidney, Rt. kidney, small bowels and whole liver were reduced by 3.2%, 4.2%, 1.5%, 6.2% and 12.7%, respectively. The treatment field size was smaller in volume in the case of the 4D-CT treatment planning. In the DVH, the 4D-CT treatment

  5. Integrable perturbed magnetic fields in toroidal geometry: An exact analytical flux surface label for large aspect ratio

    SciTech Connect

    Kallinikos, N.; Isliker, H.; Vlahos, L.; Meletlidou, E.

    2014-06-15

    An analytical description of magnetic islands is presented for the typical case of a single perturbation mode introduced to tokamak plasma equilibrium in the large aspect ratio approximation. Following the Hamiltonian structure directly in terms of toroidal coordinates, the well known integrability of this system is exploited, laying out a precise and practical way for determining the island topology features, as required in various applications, through an analytical and exact flux surface label.

  6. Influence of Critical Current Density on Guidance Force Decay of HTS Bulk Exposed to AC Magnetic Field Perturbation in a Maglev Vehicle System

    NASA Astrophysics Data System (ADS)

    Longcai, Zhang; Jianguo, Kong

    2012-07-01

    Superconducting maglev vehicle is one of the most promising applications of HTS bulks. In such a system, the HTS bulks are always exposed to AC external magnetic field, which is generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, we studied the guidance force decay of the YBCO bulk over the NdFdB guideway used in the High-temperature superconducting maglev vehicle system with the application of the AC external magnetic field, and calculated the guidance force decay as a function of time based on an analytic model. In this paper, we investigated the influence of the critical current density on the guidance force decay of HTS bulk exposed to AC field perturbation in the maglev vehicle system and try to adopt a method to suppress the decay. From the results, it was found that the guidance force decay rate was higher for the bulk with lower critical current density. Therefore, we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by improving critical current density of the bulk.

  7. On the control of magnetic perturbing field onboard landers: the Magnetometer Protection program for the ESA ExoMars/Humboldt MSMO magnetometer experiment

    NASA Astrophysics Data System (ADS)

    Menvielle, M.; Primdahl, F.; Brauer, P.; Falkenberg, T. V.; Jensen, P. A.; Merayo, J. M.; Vennerstrom, S.

    2009-04-01

    Magnetic field observations at a planetary surface have a wide potential of scientific applications, ranging from processes in the dynamic interaction between the planet environment and the solar wind, to determining the structure and thermal evolution of the interior of the planet as well as characterizing its sub-surface. Magnetic fields are generated by electric currents in the planetary space environment, induced currents in the planetary interior and possibly remanent magnetism. In consequence, hardly any other single physical quantity can be used in such a variety of studies related to planetary research. The major difficulty in implementing a magnetometer experiment onboard a lander is to achieve at acceptable costs a good Magnetometer Protection, namely to control the perturbing magnetic field generated by the lander during operations at the planetary surface, so as to achieve the least magnetic contamination of the magnetometer data by lander generated magnetic perturbations, and thus the best possible magnetic signal to magnetic noise ratio, thus ensuring the best possible magnetometer experiment science return. The purpose of this talk is to show that simple and non-expensive solutions enable one to limit the intensity of lander generated perturbing magnetic fields to levels that are compliant with the science based measurement requirements. The presented solutions are based upon ‘best effort' to being critically concerned with magnetic noise reduction, with emphasis on good and simple engineering techniques enabling minimization of and control over the magnetic perturbations at the magnetometer sensor during the surface operations phase. The presentation deals with the case history of the ongoing preparation of the MSMO magnetometer experiment, which is part the Humboldt scientific payload in the frame of the ESA ExoMars mission. Experience from previous missions constitutes the background for the MSMO Magnetometer Protection strategy. DC and AC

  8. Ground state of two-dimensional quantum-dot helium in zero magnetic field: Perturbation, diagonalization, and variational theory

    NASA Astrophysics Data System (ADS)

    Ciftja, Orion; Kumar, A. Anil

    2004-11-01

    We study the ground-state properties of two-dimensional quantum-dot helium in zero external magnetic field (a system of two interacting electrons in a two-dimensional parabolic confinement potential) by using perturbation and variational theory. We introduce a family of ground-state trial wave functions with one, two, and three variational parameters. We compare the perturbation and variational energies with numerically exact diagonalization results and earlier unrestricted Hartree-Fock studies. We find that the three-parameter variational wave function is an excellent representation of the true ground state and argue on how to generalize such a wave function for larger quantum dots with arbitrary numbers of electrons.

  9. Molecular dynamic simulations of environment and sequence dependent DNA conformations: the development of the BMS nucleic acid force field and comparison with experimental results.

    PubMed

    Langley, D R

    1998-12-01

    Molecular dynamic (MD) simulations using the BMS nucleic acid force field produce environment and sequence dependent DNA conformations that closely mimic experimentally derived structures. The parameters were initially developed to reproduce the potential energy surface, as defined by quantum mechanics, for a set of small molecules that can be used as the building blocks for nucleic acid macromolecules (dimethyl phosphate, cyclopentane, tetrahydrofuran, etc.). Then the dihedral parameters were fine tuned using a series of condensed phase MD simulations of DNA and RNA (in zero added salt, 4M NaCl, and 75% ethanol solutions). In the tuning process the free energy surface for each dihedral was derived from the MD ensemble and fitted to the conformational distributions and populations observed in 87 A- and B-DNA x-ray and 17 B-DNA NMR structures. Over 41 nanoseconds of MD simulations are presented which demonstrate that the force field is capable of producing stable trajectories, in the correct environments, of A-DNA, double stranded A-form RNA, B-DNA, Z-DNA, and a netropsin-DNA complex that closely reproduce the experimentally determined and/or canonical DNA conformations. Frequently the MD averaged structure is closer to the experimentally determined structure than to the canonical DNA conformation. MD simulations of A- to B- and B- to A-DNA transitions are also shown. A-DNA simulations in a low salt environment cleanly convert into the B-DNA conformation and converge into the RMS space sampled by a low salt simulation of the same sequence starting from B-DNA. In MD simulations using the BMS force field the B-form of d(GGGCCC)2 in a 75% ethanol solution converts into the A-form. Using the same methodology, parameters, and conditions the A-form of d(AAATTT)2 correctly converts into the B-DNA conformation. These studies demonstrate that the force field is capable of reproducing both environment and sequence dependent DNA structures. The 41 nanoseconds (nsec) of MD

  10. Conformal invariance, dark energy, and CMB non-gaussianity

    NASA Astrophysics Data System (ADS)

    Antoniadis, Ignatios; Mazur, Pawel O.; Mottola, Emil

    2012-09-01

    In addition to simple scale invariance, a universe dominated by dark energy naturally gives rise to correlation functions possessing full conformal invariance. This is due to the mathematical isomorphism between the conformal group of certain three dimensional slices of de Sitter space and the de Sitter isometry group SO(4,1). In the standard homogeneous, isotropic cosmological model in which primordial density perturbations are generated during a long vacuum energy dominated de Sitter phase, the embedding of flat spatial Bbb R3 sections in de Sitter space induces a conformal invariant perturbation spectrum and definite prediction for the shape of the non-Gaussian CMB bispectrum. In the case in which the density fluctuations are generated instead on the de Sitter horizon, conformal invariance of the Bbb S2 horizon embedding implies a different but also quite definite prediction for the angular correlations of CMB non-Gaussianity on the sky. Each of these forms for the bispectrum is intrinsic to the symmetries of de Sitter space, and in that sense, independent of specific model assumptions. Each is different from the predictions of single field slow roll inflation models, which rely on the breaking of de Sitter invariance. We propose a quantum origin for the CMB fluctuations in the scalar gravitational sector from the conformal anomaly that could give rise to these non-Gaussianities without a slow roll inflaton field, and argue that conformal invariance also leads to the expectation for the relation nS-1 = nT between the spectral indices of the scalar and tensor power spectrum. Confirmation of this prediction or detection of non-Gaussian correlations in the CMB of one of the bispectral shape functions predicted by conformal invariance can be used both to establish the physical origins of primordial density fluctuations, and distinguish between different dynamical models of cosmological vacuum dark energy.

  11. Conformal invariance, dark energy, and CMB non-gaussianity

    SciTech Connect

    Antoniadis, Ignatios; Mazur, Pawel O.; Mottola, Emil E-mail: mazur@physics.sc.edu

    2012-09-01

    In addition to simple scale invariance, a universe dominated by dark energy naturally gives rise to correlation functions possessing full conformal invariance. This is due to the mathematical isomorphism between the conformal group of certain three dimensional slices of de Sitter space and the de Sitter isometry group SO(4,1). In the standard homogeneous, isotropic cosmological model in which primordial density perturbations are generated during a long vacuum energy dominated de Sitter phase, the embedding of flat spatial R{sup 3} sections in de Sitter space induces a conformal invariant perturbation spectrum and definite prediction for the shape of the non-Gaussian CMB bispectrum. In the case in which the density fluctuations are generated instead on the de Sitter horizon, conformal invariance of the S{sup 2} horizon embedding implies a different but also quite definite prediction for the angular correlations of CMB non-Gaussianity on the sky. Each of these forms for the bispectrum is intrinsic to the symmetries of de Sitter space, and in that sense, independent of specific model assumptions. Each is different from the predictions of single field slow roll inflation models, which rely on the breaking of de Sitter invariance. We propose a quantum origin for the CMB fluctuations in the scalar gravitational sector from the conformal anomaly that could give rise to these non-Gaussianities without a slow roll inflaton field, and argue that conformal invariance also leads to the expectation for the relation n{sub S}−1 = n{sub T} between the spectral indices of the scalar and tensor power spectrum. Confirmation of this prediction or detection of non-Gaussian correlations in the CMB of one of the bispectral shape functions predicted by conformal invariance can be used both to establish the physical origins of primordial density fluctuations, and distinguish between different dynamical models of cosmological vacuum dark energy.

  12. ELECTROMAGNETISM, OPTICS, ACOUSTICS, HEAT TRANSFER, CLASSICAL MECHANICS, AND FLUID DYNAMICS: Local Control of Two-Photon Absorption in a Six-Level Atomic System by Using a Coherent Perturbation Field

    NASA Astrophysics Data System (ADS)

    Jia, Wen-Zhi; Wang, Shun-Jin

    2009-11-01

    If a coherent perturbation field is used to couple the excited level of the coupling transition in the five-level K-type atom with another higher excited level, the two-photon electromagnetically induced transparency can be locally modulated by altering the parameters of the additional perturbation field. With different detunings of the coherent perturbation field, the absorption peak or transparency window with sharp and high-contrast spectral feature can be generated in the two-photon absorption spectrum. The physical interpretation of these phenomena is given in terms of the dressed states.

  13. Studies on the response of resistive-wall modes to applied magnetic perturbations in the EXTRAP T2R reversed field pinch

    SciTech Connect

    Gregoratto, D.; Drake, J.R.; Yadikin, D.; Liu, Y.Q.; Paccagnella, R.; Brunsell, P.R.; Bolzonella, T.; Marchiori, G.; Cecconello, M.

    2005-09-15

    Arrays of magnetic coils and sensors in the EXTRAP T2R [P. R. Brunsell et al., Plasma Phys. Controlled Fusion 43 1457 (2001)] reversed-field pinch have been used to investigate the plasma response to an applied resonant magnetic perturbation in the range of the resistive-wall modes (RWMs). Measured RWM growth rates agree with predictions of a cylindrical ideal-plasma model. The linear growth of low-n marginally stable RWMs is related to the so-called resonant-field amplification due to a dominant |n|=2 machine error field of about 2 G. The dynamics of the m=1 RWMs interacting with the applied field produced by the coils can be accurately described by a two-pole system. Estimated poles and residues are given with sufficient accuracy by the cylindrical model with a thin continuous wall.

  14. High-Performance Stable Field Emission with Ultralow Turn on Voltage from rGO Conformal Coated TiO2 Nanotubes 3D Arrays.

    PubMed

    Agrawal, Yogyata; Kedawat, Garima; Kumar, Pawan; Dwivedi, Jaya; Singh, V N; Gupta, R K; Gupta, Bipin Kumar

    2015-01-01

    A facile method to produce conformal coated reduced graphene oxide (rGO) on vertically aligned titanium oxide (TiO2) nanotubes three dimensional (3D) arrays (NTAs) is demonstrated for enhanced field emission display applications. These engineered nano arrays exhibit efficient electron field emission properties such as high field emission current density (80 mA/cm(2)), low turn-on field (1.0 V/μm) and field enhancement factor (6000) with high emission current stability. Moreover, these enhancements observed in nano arrays attribute to the contribution of low work function with non-rectifying barriers, which allow an easy injection of electrons from the conduction band of TiO2 into the Fermi level of reduced graphene oxide under external electric field. The obtained results are extremely advantageous for its potential application in field emission devices. PMID:26152895

  15. High-Performance Stable Field Emission with Ultralow Turn on Voltage from rGO Conformal Coated TiO2 Nanotubes 3D Arrays

    PubMed Central

    Agrawal, Yogyata; Kedawat, Garima; Kumar, Pawan; Dwivedi, Jaya; Singh, V. N.; Gupta, R. K.; Gupta, Bipin Kumar

    2015-01-01

    A facile method to produce conformal coated reduced graphene oxide (rGO) on vertically aligned titanium oxide (TiO2) nanotubes three dimensional (3D) arrays (NTAs) is demonstrated for enhanced field emission display applications. These engineered nano arrays exhibit efficient electron field emission properties such as high field emission current density (80 mA/cm2), low turn-on field (1.0 V/μm) and field enhancement factor (6000) with high emission current stability. Moreover, these enhancements observed in nano arrays attribute to the contribution of low work function with non-rectifying barriers, which allow an easy injection of electrons from the conduction band of TiO2 into the Fermi level of reduced graphene oxide under external electric field. The obtained results are extremely advantageous for its potential application in field emission devices. PMID:26152895

  16. Motion in a central field in the presence of a constant perturbing acceleration in a co-moving coordinate system

    NASA Astrophysics Data System (ADS)

    Sannikova, T. N.; Kholshevnikov, K. V.

    2015-08-01

    The motion of a point mass under the action of a gravitational force toward a central body and a perturbing acceleration P is considered. The magnitude of P is taken to be small compared to the main gravitational acceleration due to the central body, and the direction of P to be constant in a standard astronomical coordinate system with its origin at the central body and axes directed along the radius vector, the transversal, and the binormal. Consideration of a constant vector perturbing acceleration simplifies averaging of the Euler equations for the motion in osculating elements, making it straightforward to obtain evolutionary differential equations of motion in the mean elements, as was done earlier in a first small-parameter approximation. This paper is devoted to integration of the mean equations. The system is integratable by quadratures if at least one component of the perturbing acceleration is zero, and also if the orbit is initially circular. Moreover, all the quadratures can be expressed in terms of elementary functions and elliptical integrals of the first kind in Jacobi form. If all three components of P are non-zero, this problem reduces to a system of two first-order differential equations, which are apparently not integrable. Possible applications include the motion of natural and artificial satellites taking into account light pressure, the motion of a spacecraft with low thrust, and the motion of an asteroid subject to a thrust from an engine mounted on it or to a gravitational tractor designed, for example, to avoid a collision with Earth.

  17. Conformal anomaly actions for dilaton interactions

    NASA Astrophysics Data System (ADS)

    Delle Rose, Luigi; Marzo, Carlo; Serino, Mirko

    2014-11-01

    We discuss, in conformally invariant field theories such as QCD with massless fermions, a possible link between the perturbative signature of the conformal anomaly, in the form of anomaly poles of the 1-particle irreducible effective action, and its descrip- tion in terms of Wess-Zumino actions with a dilaton. The two descriptions are expected to capture the UV and IR behaviour of the conformal anomaly, in terms of fundamental and effective degrees of freedom respectively, with the dilaton effective state appearing in a nonlinear realization. As in the chiral case, conformal anomalies seem to be related to the appearance of these effective interactions in the 1PI action in all the gauge-invariant sectors of the Standard Model. We show that, as a consequence of the underlying anomalous symmetry, the infinite hierarchy of recurrence relations involving self-interactions of the dilaton is entirely determined only by the first four of them. This relation can be generalized to any even space-time dimension.

  18. PERTURBING LIGNIFICATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Perturbing lignification is possible in multiple and diverse ways. Without obvious growth/development phenotypes, transgenic angiosperms can have lignin levels reduced to half the normal level, can have compositions ranging from very high-guaiacyl/low-syringyl to almost totally syringyl, and can eve...

  19. The Use of Perturbation with Monte Carlo Simulation Approach to Estimate the Reliability of the Space Shuttle Field Joints

    NASA Astrophysics Data System (ADS)

    Jenab, Karoush; Nicoll, Thomas

    2015-11-01

    The space shuttle Challenger disaster was brought on by a faulty design and a misunderstanding of reliability. The purpose of this article is to illuminate some shortcomings in the design and interpretations of the systems reliability. It will be shown that the evidence was in place, waiting for discovery long before the disaster, and the tools been available to better evaluate the reliability of the shuttle, the disaster may have never taken place. One such tool that will be discussed is the use of model perturbation with Monte Carlo simulation analysis to yield a better understanding of the structural physics that were at play during the disaster.

  20. Uniqueness of the gauge invariant action for cosmological perturbations

    SciTech Connect

    Prokopec, Tomislav; Weenink, Jan E-mail: j.g.weenink@uu.nl

    2012-12-01

    In second order perturbation theory different definitions are known of gauge invariant perturbations in single field inflationary models. Consequently the corresponding gauge invariant cubic actions do not have the same form. Here we show that the cubic action for one choice of gauge invariant variables is unique in the following sense: the action for any other, non-linearly related variable can be brought to the same bulk action, plus additional boundary terms. These boundary terms correspond to the choice of hypersurface and generate extra, disconnected contributions to the bispectrum. We also discuss uniqueness of the action with respect to conformal frames. When expressed in terms of the gauge invariant curvature perturbation on uniform field hypersurfaces the action for cosmological perturbations has a unique form, independent of the original Einstein or Jordan frame. Crucial is that the gauge invariant comoving curvature perturbation is frame independent, which makes it extremely helpful in showing the quantum equivalence of the two frames, and therefore in calculating quantum effects in nonminimally coupled theories such as Higgs inflation.

  1. Field theoretical Lie symmetry analysis: The Möbius group, exact solutions of conformal autonomous systems, and predictive model-building

    NASA Astrophysics Data System (ADS)

    Christodoulides, Kyriakos

    2014-07-01

    We study single and coupled first-order differential equations (ODEs) that admit symmetries with tangent vector fields, which satisfy the N-dimensional Cauchy-Riemann equations. In the two-dimensional case, classes of first-order ODEs which are invariant under Möbius transformations are explored. In the N dimensional case we outline a symmetry analysis method for constructing exact solutions for conformal autonomous systems. A very important aspect of this work is that we propose to extend the traditional technical usage of Lie groups to one that could provide testable predictions and guidelines for model-building and model-validation. The Lie symmetries in this paper are constrained and classified by field theoretical considerations and their phenomenological implications. Our results indicate that conformal transformations are appropriate for elucidating a variety of linear and nonlinear systems which could be used for, or inspire, future applications. The presentation is pragmatic and it is addressed to a wide audience.

  2. Perturbation method for the second-order nonlinear effect of focused acoustic field around a scatterer in an ideal fluid.

    PubMed

    Liu, Gang; Jayathilake, Pahala Gedara; Khoo, Boo Cheong

    2014-02-01

    Two nonlinear models are proposed to investigate the focused acoustic waves that the nonlinear effects will be important inside the liquid around the scatterer. Firstly, the one dimensional solutions for the widely used Westervelt equation with different coordinates are obtained based on the perturbation method with the second order nonlinear terms. Then, by introducing the small parameter (Mach number), a dimensionless formulation and asymptotic perturbation expansion via the compressible potential flow theory is applied. This model permits the decoupling between the velocity potential and enthalpy to second order, with the first potential solutions satisfying the linear wave equation (Helmholtz equation), whereas the second order solutions are associated with the linear non-homogeneous equation. Based on the model, the local nonlinear effects of focused acoustic waves on certain volume are studied in which the findings may have important implications for bubble cavitation/initiation via focused ultrasound called HIFU (High Intensity Focused Ultrasound). The calculated results show that for the domain encompassing less than ten times the radius away from the center of the scatterer, the non-linear effect exerts a significant influence on the focused high intensity acoustic wave. Moreover, at the comparatively higher frequencies, for the model of spherical wave, a lower Mach number may result in stronger nonlinear effects. PMID:24070825

  3. Time-differential perturbed angular correlation study of the electric field gradient in Ti2Rh MoSi2-type compound

    NASA Astrophysics Data System (ADS)

    Wodniecki, P.; Kulińska, A.; Wodniecka, B.

    The electric field gradient (EFG) at the 181Hf→181Ta site in Ti2Rh C11 b -type compound was measured as a function of temperature using time-differential perturbed angular correlation (TDPAC) technique. The room temperature results show one EFG with the parameters of: ν Q =336(1) MHz→V zz =5.9×1017 V cm-2, η=0.1. Very week linear temperature dependence of this EFG was measured with the slope of 3.6 (2)×10-5 K-1. The results are compared with those for other isostructural compounds.

  4. Time-differential perturbed angular correlation study of the electric field gradient in Ti2Rh MoSi2-type compound

    NASA Astrophysics Data System (ADS)

    Wodniecki, P.; Kulińska, A.; Wodniecka, B.

    2007-06-01

    The electric field gradient (EFG) at the 181Hf→181Ta site in Ti2Rh C11 b -type compound was measured as a function of temperature using time-differential perturbed angular correlation (TDPAC) technique. The room temperature results show one EFG with the parameters of: ν Q = 336(1) MHz→V zz =5.9 × 1017 V cm - 2, η = 0.1. Very week linear temperature dependence of this EFG was measured with the slope of 3.6 (2) × 10 - 5 K - 1. The results are compared with those for other isostructural compounds.

  5. Local probe studies of Fe hyperfine field in CaFe2As2 by time differential perturbed angular distribution (TDPAD) spectroscopy and ab initio methods

    NASA Astrophysics Data System (ADS)

    Mohanta, S. K.; Mishra, S. N.; Davane, S. M.; Kumar, Neeraj; Thamizhavel, A.; Layek, S.; Hossain, Z.; Srivastava, S. K.

    2013-03-01

    Applying the γ-ray perturbed angular distribution technique we have measured the magnetic hyperfine field and spin relaxation time of recoil implanted 54Fe in single and polycrystalline CaFe2As2 over the temperature range 20-360 K, encompassing both tetragonal and orthorhombic structural phases of the material. The magnetic response of Fe in the high temperature tetragonal phase (T ⩾ 180 K), show Curie-Weiss type local susceptibility and Korringa like spin relaxation, reflecting the presence of localized moment on Fe. In the orthorhombic phase, the spin rotation spectra of 54Fe show two magnetic hyperfine field components, both exhibiting quasi two dimensional magnetic ordering. The experimentally measured hyperfine field and Fe moment show good agreement with results obtained from ab initio calculations performed within the frame work of local spin density approximation (LSDA).

  6. Cosmological Perturbations

    NASA Astrophysics Data System (ADS)

    Lesgourges, J.

    2013-08-01

    We present a self-contained summary of the theory of linear cosmological perturbations. We emphasize the effect of the six parameters of the minimal cosmological model, first, on the spectrum of Cosmic Microwave Background temperature anisotropies, and second, on the linear matter power spectrum. We briefly review at the end the possible impact of a few non-minimal dark matter and dark energy models.

  7. Toroidal modelling of resonant magnetic perturbations response in ASDEX-Upgrade: coupling between field pitch aligned response and kink amplification

    NASA Astrophysics Data System (ADS)

    Ryan, D. A.; Liu, Y. Q.; Kirk, A.; Suttrop, W.; Dudson, B.; Dunne, M.; Fischer, R.; Fuchs, J. C.; Garcia-Munoz, M.; Kurzan, B.; Piovesan, P.; Reinke, M.; Willensdorfer, M.; the ASDEX-Upgrade Team; the EUROfusion MST1 Team

    2015-09-01

    Using the MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), the single fluid resistive MHD plasma response to applied n   =   2 resonant magnetic perturbations is computed, for a plasma discharge in the ASDEX-Upgrade tokamak. The computation predicts strong kink amplification, as previously predicted in DIII-D (Haskey et al 2014 Plasma Phys. Control. Fusion 56 035005), which is strongly dependent on the toroidal phase shift between the upper and lower coils, Δ {φ\\text{ul}} . In particular, edge localised low n peeling modes with poloidal mode numbers just above pitch resonance—a subset of the kink response—are amplified. The robustness of the amplified peeling response with respect to truncation of the X point is investigated, by recomputing the plasma response for a range of edge geometries. It is found that the computed peeling response, when plotted against the safety factor, is not sensitive to the numerical truncation near the X point. It is also predicted that near the plasma edge where resistivity is large, the pitch aligned components are finite and also strongly dependent on Δ {φ\\text{ul}} . A previous proposal that the amplified peeling response may indirectly drive the pitch aligned components by spectral proximity (Lanctot et al 2013 Nucl. Fusion 53 083019), is investigated by numerically applying magnetic perturbations of a single poloidal harmonic, as a boundary condition at the plasma edge. It is found that poloidal harmonic coupling causes harmonics to couple to and drive harmonics directly beneath them spectrally, and also that the pitch aligned components can be driven by this mechanism. This suggests that it is quite possible that the amplified low n peeling response can drive the pitch aligned components when it is strongly amplified, which would alter the coil configuration for optimum plasma stochastization, with implications for ELM control by RMPs.

  8. Canonical density matrix perturbation theory.

    PubMed

    Niklasson, Anders M N; Cawkwell, M J; Rubensson, Emanuel H; Rudberg, Elias

    2015-12-01

    Density matrix perturbation theory [Niklasson and Challacombe, Phys. Rev. Lett. 92, 193001 (2004)] is generalized to canonical (NVT) free-energy ensembles in tight-binding, Hartree-Fock, or Kohn-Sham density-functional theory. The canonical density matrix perturbation theory can be used to calculate temperature-dependent response properties from the coupled perturbed self-consistent field equations as in density-functional perturbation theory. The method is well suited to take advantage of sparse matrix algebra to achieve linear scaling complexity in the computational cost as a function of system size for sufficiently large nonmetallic materials and metals at high temperatures. PMID:26764847

  9. Solar wind variations as a source of short-term magnetic field perturbations in the dayside magnetosphere.

    NASA Astrophysics Data System (ADS)

    Sibeck, D. G.; Borodkova, N. L.; Zastenker, G. N.

    1996-06-01

    Short variations (about several minutes) in the dayside magnetospheric magnetic field measured by the GOES-5 and GOES-6 geosynchronous satellites were compared with simultaneous observations of the solar wind plasma and magnetic field aboard the Prognoz-10 and IMP-8 satellites. The results indicate that more than half of the events were caused by dynamic pressure variations in the solar wind. A considerable portion of the events can be associated with fluctuations in the orientation of the interplanetary magnetic field, influencing the foreshock plasma pressure.

  10. Na,K-ATPase as A Brownian Motor: Electric Field-InducedConformational Fluctuation Leads to Uphill Pumping of Cation inthe Absence of ATP.

    PubMed

    Tsong, Tian Yow

    2002-06-01

    Na,K-ATPase uses chemical bond energy of ATP to pump K(+) into, andNa(+) out of a cell. Both are uphill transports. During the catalyticcycle the enzyme alternates between two conformational states, E(1) andE(2). This communication describes an experiment, which employs electricfield to drive oscillation or fluctuation of enzyme conformation betweenthe E(1) and the E(2) states. It is shown that the field-inducedconformational oscillation or fluctuation leads to uphill pumping of thecation by the enzyme without consumption of ATP. Biochemical specificityof the catalysis is preserved. Data indicate that Na,K-ATPase can harvestenergy from the applied electric field to perform chemical work, and aratchet mechanism is inherent in this energy transduction process. ATheory of Electroconformational Coupling (TEC) that embodies essentialfeatures of the Brownian Ratchet successfully simulates the field-frequencyand field-amplitude optima and other features of the ion pumping activity.A four-state TEC motor can achieve high efficiency of the energytransduction, asymptotically reaching 100% under the optimal condition.Pumping by ion rectification fails to reach high efficiency. The TECconcept is also mused to understand other biological motors and engines. PMID:23345777

  11. Aspects of perturbative unitarity

    NASA Astrophysics Data System (ADS)

    Anselmi, Damiano

    2016-07-01

    We reconsider perturbative unitarity in quantum field theory and upgrade several arguments and results. The minimum assumptions that lead to the largest time equation, the cutting equations and the unitarity equation are identified. Using this knowledge and a special gauge, we give a new, simpler proof of perturbative unitarity in gauge theories and generalize it to quantum gravity, in four and higher dimensions. The special gauge interpolates between the Feynman gauge and the Coulomb gauge without double poles. When the Coulomb limit is approached, the unphysical particles drop out of the cuts and the cutting equations are consistently projected onto the physical subspace. The proof does not extend to nonlocal quantum field theories of gauge fields and gravity, whose unitarity remains uncertain.

  12. Two-dimensional copolymers and multifractality: comparing perturbative expansions, Monte Carlo simulations, and exact results.

    PubMed

    von Ferber, C; Holovatch, Yu

    2002-04-01

    We analyze the scaling laws for a set of two different species of long flexible polymer chains joined together at one of their extremities (copolymer stars) in space dimension D=2. We use a formerly constructed field-theoretic description and compare our perturbative results for the scaling exponents with recent conjectures for exact conformal scaling dimensions derived by a conformal invariance technique in the context of D=2 quantum gravity. A simple Monte Carlo simulation brings about reasonable agreement with both approaches. We analyze the remarkable multifractal properties of the spectrum of scaling exponents. PMID:12005898

  13. Conformational sampling techniques.

    PubMed

    Hatfield, Marcus P D; Lovas, Sándor

    2014-01-01

    The potential energy hyper-surface of a protein relates the potential energy of the protein to its conformational space. This surface is useful in determining the native conformation of a protein or in examining a statistical-mechanical ensemble of structures (canonical ensemble). In determining the potential energy hyper-surface of a protein three aspects must be considered; reducing the degrees of freedom, a method to determine the energy of each conformation and a method to sample the conformational space. For reducing the degrees of freedom the choice of solvent, coarse graining, constraining degrees of freedom and periodic boundary conditions are discussed. The use of quantum mechanics versus molecular mechanics and the choice of force fields are also discussed, as well as the sampling of the conformational space through deterministic and heuristic approaches. Deterministic methods include knowledge-based statistical methods, rotamer libraries, homology modeling, the build-up method, self-consistent electrostatic field, deformation methods, tree-based elimination and eigenvector following routines. The heuristic methods include Monte Carlo chain growing, energy minimizations, metropolis monte carlo and molecular dynamics. In addition, various methods to enhance the conformational search including the deformation or smoothing of the surface, scaling of system parameters, and multi copy searching are also discussed. PMID:23947647

  14. Ion velocity distributions in the presence of cylindrically symmetric electric field perturbations: the collision-free case

    NASA Astrophysics Data System (ADS)

    Ma, John Zhen Guo; Ma, John Zhen Guo; St-Maurice, Jean-Pierre

    Because of the strong ambient magnetic field, particularly at ionospheric altitudes, the auroral regions are flush with cylindrical structures covering an impressive range of scales which include lower hybrid cavities on decameter scales, auroral rays on km scales and vortices on tens to hundreds of km scales. In addition, a plethora of in-situ magnetic field and electric field observations and groundbased radar observations strongly suggests that very large parallel current densities are triggered in the upper ionosphere. These observations and just simple geometric considerations have motivated us to study the ion velocity distributions that would accompany strong perpendicular electric fields in a cylindrically symmetric geometry. The applications of the work have to do with the transport coefficients in such regions as well as with local instrumental observations of distribution functions with particle detectors. We have evolved a kinetic theoretical framework in which we have obtained analytical solutions for a number of important limits. We have also developed a semi-numerical method by which to obtain the ion velocity distribution under more general conditions for which analytical solutions are not possible. Our presentation will focus strongly on collision-free results, which stem from the following assumptions: (1) a perpendicular electric field is introduced initially on a time scale that is fast compared to the local ion gyrofrequency (but slow compared to electron plasma and gyrofrequencies); (2) the ion collision frequency is much smaller than the ion gyrofrequency, so that we can calculate meaningful collisionfree solutions. We will present analytical solutions for the distribution functions and their velocity moments inside regions for which the electric field can be assumed to increase linearly with distance from the axis of the cylindrical region, this for a number of initial cylindrically symmetric density distributions. We will also present our

  15. Optical and physical characterization of a local evanescent array coupled biosensor: Use of evanescent field perturbations for multianalyte sensing

    PubMed Central

    Stephens, Matthew D.; Yuan, Guangwei; Lear, Kevin L.; Dandy, David S.

    2010-01-01

    The evanescent field surrounding the core of an optical waveguide is very sensitive to refractive index changes near the core. This sensitivity can be exploited to form the basis for a quantitative sensor with high specificity and sensitivity. Selective probe molecules may be attached to the surface of a waveguide core and the evanescent field locally monitored as target analytes are introduced to the system. In this study, probe/analyte regions were simulated using lithographically patterned organic films with thicknesses of 60 nm and 130 nm. The evanescent field strength was measured quantitatively using near field scanning optical microscopy (NSOM). The presence of the organic material on the waveguide caused up to a 70% change in the intensity of the evanescent field over the patterned region and the excitation of a weakly bound higher order mode. The waveguide core and surrounding cladding were numerically simulated using the beam propagation method and these predictions are in quantitative agreement with the experimental results obtained using NSOM. PMID:20436955

  16. Electron-impact elastic scattering of helium in the presence of a laser field: non perturbative approach

    NASA Astrophysics Data System (ADS)

    Makhoute, A.; Agueny, H.; Dubois, A.; Ajana, I.; Taoutioui, A.

    2016-04-01

    We report a detailed analysis of electron-helium scattering in the presence of a laser field; focusing on the elastic process of helium atoms from the ground state 11 S. The process under investigation is dealt with a nonperturbative approach using the Volkov wave function to describe the incident and scattered electrons, while the laser-target interaction is treated by using the Floquet method. The interaction of the incident electron with the atomic target is treated within the first Born approximation. Our results are perfectly consistent with the experimental data of DeHarak et al and with the Kroll-Watson approximation results for both one and two photon emission. We have investigated the effect of nonresonant and near resonant laser field on the electron-helium elastic collision process. It was found that the differential cross section is sensitive to the intensity and the frequency of the laser field. In the case of a non resonant laser field, dressing effects are important at small scattering angles. For a near-resonant laser photon energy, those effects are strongly reduced in the forward direction.

  17. Comparison of three different methods of perturbing the potential vorticity field in mesoscale forecasts of Mediterranean heavy precipitation events: PV-gradient, PV-adjoint and PV-satellite

    NASA Astrophysics Data System (ADS)

    Vich, M.; Romero, R.; Richard, E.; Arbogast, P.; Maynard, K.

    2010-09-01

    Heavy precipitation events occur regularly in the western Mediterranean region. These events often have a high impact on the society due to economic and personal losses. The improvement of the mesoscale numerical forecasts of these events can be used to prevent or minimize their impact on the society. In previous studies, two ensemble prediction systems (EPSs) based on perturbing the model initial and boundary conditions were developed and tested for a collection of high-impact MEDEX cyclonic episodes. These EPSs perturb the initial and boundary potential vorticity (PV) field through a PV inversion algorithm. This technique ensures modifications of all the meteorological fields without compromising the mass-wind balance. One EPS introduces the perturbations along the zones of the three-dimensional PV structure presenting the local most intense values and gradients of the field (a semi-objective choice, PV-gradient), while the other perturbs the PV field over the MM5 adjoint model calculated sensitivity zones (an objective method, PV-adjoint). The PV perturbations are set from a PV error climatology (PVEC) that characterizes typical PV errors in the ECMWF forecasts, both in intensity and displacement. This intensity and displacement perturbation of the PV field is chosen randomly, while its location is given by the perturbation zones defined in each ensemble generation method. Encouraged by the good results obtained by these two EPSs that perturb the PV field, a new approach based on a manual perturbation of the PV field has been tested and compared with the previous results. This technique uses the satellite water vapor (WV) observations to guide the correction of initial PV structures. The correction of the PV field intents to improve the match between the PV distribution and the WV image, taking advantage of the relation between dark and bright features of WV images and PV anomalies, under some assumptions. Afterwards, the PV inversion algorithm is applied to run

  18. Quantizing Open Spin Chains with Variable Length and Giant Gravitons in the Anti-de Sitter-Space/Conformal Field-Theory Correspondence

    SciTech Connect

    Berenstein, David; Correa, Diego H.; Vazquez, Samuel E.

    2005-11-04

    We study an XXX open spin chain with variable number of sites, where the variability is introduced only at the boundaries. This model arises naturally in the study of giant gravitons in the anti-de Sitter-space/conformal field-theory correspondence. We show how to quantize the spin chain by mapping its states to a bosonic lattice of finite length with sources and sinks of particles at the boundaries. Using coherent states, we show how the Hamiltonian for the bosonic lattice gives the correct description of semiclassical open strings ending on giant gravitons.

  19. Conformal superalgebras via tractor calculus

    NASA Astrophysics Data System (ADS)

    Lischewski, Andree

    2015-01-01

    We use the manifestly conformally invariant description of a Lorentzian conformal structure in terms of a parabolic Cartan geometry in order to introduce a superalgebra structure on the space of twistor spinors and normal conformal vector fields formulated in purely algebraic terms on parallel sections in tractor bundles. Via a fixed metric in the conformal class, one reproduces a conformal superalgebra structure that has been considered in the literature before. The tractor approach, however, makes clear that the failure of this object to be a Lie superalgebra in certain cases is due to purely algebraic identities on the spinor module and to special properties of the conformal holonomy representation. Moreover, it naturally generalizes to higher signatures. This yields new formulas for constructing new twistor spinors and higher order normal conformal Killing forms out of existing ones, generalizing the well-known spinorial Lie derivative. Moreover, we derive restrictions on the possible dimension of the space of twistor spinors in any metric signature.

  20. Higgs critical exponents and conformal bootstrap in four dimensions

    NASA Astrophysics Data System (ADS)

    Antipin, Oleg; Mølgaard, Esben; Sannino, Francesco

    2015-06-01

    We investigate relevant properties of composite operators emerging in non-supersymmetric, four-dimensional gauge-Yukawa theories with interacting conformal fixed points within a precise framework. The theories investigated in this work are structurally similar to the standard model of particle interactions, but differ by developing perturbative interacting fixed points. We investigate the physical properties of the singlet and the adjoint composite operators quadratic in the Higgs field, and discover, via a direct computation, that the singlet anomalous dimension is substantially larger than the adjoint one. The numerical bootstrap results are, when possible, compared to our precise findings associated to the four dimensional conformal field theoretical results. To accomplish this, it was necessary to calculate explicitly the crossing symmetry relations for the global symmetry group SU( N ) × SU( N ).

  1. Community-wide Validation of Geospace Model Ground Magnetic Field Perturbation Predictions to Support Model Transition to Operations

    NASA Technical Reports Server (NTRS)

    Pulkkinen, A.; Rastaetter, L.; Kuznetsova, M.; Singer, H.; Balch, C.; Weimer, D.; Toth, G.; Ridley, A.; Gombosi, T.; Wiltberger, M.; Raeder, J.; Weigel, R.

    2013-01-01

    In this paper we continue the community-wide rigorous modern space weather model validation efforts carried out within GEM, CEDAR and SHINE programs. In this particular effort, in coordination among the Community Coordinated Modeling Center (CCMC), NOAA Space Weather Prediction Center (SWPC), modelers, and science community, we focus on studying the models' capability to reproduce observed ground magnetic field fluctuations, which are closely related to geomagnetically induced current phenomenon. One of the primary motivations of the work is to support NOAA SWPC in their selection of the next numerical model that will be transitioned into operations. Six geomagnetic events and 12 geomagnetic observatories were selected for validation.While modeled and observed magnetic field time series are available for all 12 stations, the primary metrics analysis is based on six stations that were selected to represent the high-latitude and mid-latitude locations. Events-based analysis and the corresponding contingency tables were built for each event and each station. The elements in the contingency table were then used to calculate Probability of Detection (POD), Probability of False Detection (POFD) and Heidke Skill Score (HSS) for rigorous quantification of the models' performance. In this paper the summary results of the metrics analyses are reported in terms of POD, POFD and HSS. More detailed analyses can be carried out using the event by event contingency tables provided as an online appendix. An online interface built at CCMC and described in the supporting information is also available for more detailed time series analyses.

  2. Killing and conformal Killing tensors

    NASA Astrophysics Data System (ADS)

    Heil, Konstantin; Moroianu, Andrei; Semmelmann, Uwe

    2016-08-01

    We introduce an appropriate formalism in order to study conformal Killing (symmetric) tensors on Riemannian manifolds. We reprove in a simple way some known results in the field and obtain several new results, like the classification of conformal Killing 2-tensors on Riemannian products of compact manifolds, Weitzenböck formulas leading to non-existence results, and construct various examples of manifolds with conformal Killing tensors.

  3. Molecular mechanics conformational analysis of tylosin

    NASA Astrophysics Data System (ADS)

    Ivanov, Petko M.

    1998-01-01

    The conformations of the 16-membered macrolide antibiotic tylosin were studied with molecular mechanics (AMBER∗ force field) including modelling of the effect of the solvent on the conformational preferences (GB/SA). A Monte Carlo conformational search procedure was used for finding the most probable low-energy conformations. The present study provides complementary data to recently reported analysis of the conformations of tylosin based on NMR techniques. A search for the low-energy conformations of protynolide, a 16-membered lactone containing the same aglycone as tylosin, was also carried out, and the results were compared with the observed conformation in the crystal as well as with the most probable conformations of the macrocyclic ring of tylosin. The dependence of the results on force field was also studied by utilizing the MM3 force field. Some particular conformations were computed with the semiempirical molecular orbital methods AM1 and PM3.

  4. Causal compensated perturbations in cosmology

    NASA Technical Reports Server (NTRS)

    Veeraraghavan, Shoba; Stebbins, Albert

    1990-01-01

    A theoretical framework is developed to calculate linear perturbations in the gravitational and matter fields which arise causally in response to the presence of stiff matter sources in a FRW cosmology. It is shown that, in order to satisfy energy and momentum conservation, the gravitational fields of the source must be compensated by perturbations in the matter and gravitational fields, and the role of such compensation in containing the initial inhomogeneities in their subsequent evolution is discussed. A complete formal solution is derived in terms of Green functions for the perturbations produced by an arbitrary source in a flat universe containing cold dark matter. Approximate Green function solutions are derived for the late-time density perturbations and late-time gravitational waves in a universe containing a radiation fluid. A cosmological energy-momentum pseudotensor is defined to clarify the nature of energy and momentum conservation in the expanding universe.

  5. Perturbative fragmentation

    SciTech Connect

    Kopeliovich, B. Z.; Pirner, H.-J.; Potashnikova, I. K.; Schmidt, Ivan; Tarasov, A. V.

    2008-03-01

    The Berger model of perturbative fragmentation of quarks to pions is improved by providing an absolute normalization and keeping all terms in a (1-z) expansion, which makes the calculation valid at all values of fractional pion momentum z. We also replace the nonrelativistic wave function of a loosely bound pion by the more realistic procedure of projecting to the light-cone pion wave function, which in turn is taken from well known models. The full calculation does not confirm the (1-z){sup 2} behavior of the fragmentation function (FF) predicted in [E. L. Berger, Z. Phys. C 4, 289 (1980); Phys. Lett. 89B, 241 (1980] for z>0.5, and only works at very large z>0.95, where it is in reasonable agreement with phenomenological FFs. Otherwise, we observe quite a different z-dependence which grossly underestimates data at smaller z. The disagreement is reduced after the addition of pions from decays of light vector mesons, but still remains considerable. The process dependent higher twist terms are also calculated exactly and found to be important at large z and/or p{sub T}.

  6. Investigations of ultrafast ligand rebinding to heme and heme proteins using temperature and strong magnetic field perturbations

    NASA Astrophysics Data System (ADS)

    Zhang, Zhenyu

    This thesis is written to summarize investigations of the mechanisms that underlie the kinetics of diatomic ligand rebinding to the iron atom of the heme group, which is chelated inside heme proteins. The family of heme proteins is a major object of studies for several branches of scientific research activity. Understanding the ligand binding mechanisms and pathways is one of the major goals for biophysics. My interests mainly focus on the physics of this ligand binding process. Therefore, to investigate the problem, isolated from the influence of the protein matrix, Fe-protophorphyrin IX is chosen as the prototype system in my studies. Myoglobin, the most extensively and intensively studied protein, is another ideal system that allows coupling the protein polypeptide matrix into the investigation. A technique to synchro-lock two laser pulse trains electronically is applied to our pump-probe spectroscopic studies. Based on this technique, a two color, fs/ps pump-probe system is developed which extends the temporal window for our investigation to 13ns and fills a gap existing in previous pump-probe investigations. In order to apply this newly-developed pump-probe laser system to implement systematic studies on the kinetics of diatomic ligand (NO, CO, O2) rebinding to heme and heme proteins, several experimental setups are utilized. In Chapter 1, the essential background knowledge, which helps to understand the iron-ligand interaction, is briefly described. In Chapter 2, in addition to a description of the preparation protocols of protein samples and details of the method for data analysis, three home-made setups are described, which include: a picosecond laser regenerative amplifier, a pump-probe application along the bore (2-inch in diameter) of a superconducting magnet and a temperature-controllable cryostat for spinning sample cell. Chapter 3 presents high magnetic field studies of several heme-ligand or protein-ligand systems. Pump-probe spectroscopy is used to

  7. Impact of 2′-hydroxyl sampling on the conformational properties of RNA: Update of the CHARMM all-atom additive force field for RNA

    PubMed Central

    Denning, Elizabeth J.; Priyakumar, U. Deva; Nilsson, Lennart; MacKerell, Alexander D.

    2011-01-01

    Here, we present an update of the CHARMM27 all-atom additive force field for nucleic acids that improves the treatment of RNA molecules. The original CHARMM27 force field parameters exhibit enhanced Watson-Crick (WC) base pair opening which is not consistent with experiment while analysis of MD simulations show the 2′-hydroxyl moiety to almost exclusively sample the O3′ orientation. Quantum mechanical studies of RNA related model compounds indicate the energy minimum associated with the O3′ orientation to be too favorable, consistent with the MD results. Optimization of the dihedral parameters dictating the energy of the 2′-hydroxyl proton targeting the QM data yielded several parameter sets, which sample both the base and O3′ orientations of the 2′-hydroxyl to varying degrees. Selection of the final dihedral parameters was based on reproduction of hydration behavior as related to a survey of crystallographic data and better agreement with experimental NMR J-coupling values. Application of the model, designated CHARMM36, to a collection of canonical and non-canonical RNA molecules reveals overall improved agreement with a range of experimental observables as compared to CHARMM27. The results also indicate the sensitivity of the conformational heterogeneity of RNA to the orientation of the 2′-hydroxyl moiety and support a model whereby the 2′-hydroxyl can enhance the probability of conformational transitions in RNA. PMID:21469161

  8. Exact chiral spin liquids and mean-field perturbations of gamma matrix models on the ruby lattice

    NASA Astrophysics Data System (ADS)

    Whitsitt, Seth; Chua, Victor; Fiete, Gregory A.

    2012-11-01

    We theoretically studied an exactly solvable gamma matrix generalization of the Kitaev spin model on the ruby lattice, which is a honeycomb lattice with ‘expanded’ vertices and links. We find that this model displays an exceptionally rich phase diagram that includes (i) gapless phases with stable spin Fermi surfaces, (ii) gapless phases with low-energy Dirac cones and quadratic band touching points and (iii) gapped phases with finite Chern numbers possessing the values ±4,±3,±2 and ±1. The model is then generalized to include Ising-like interactions that break the exact solvability of the model in a controlled manner. When these terms are dominant, they lead to a trivial Ising ordered phase which is shown to be adiabatically connected to a large coupling limit of the exactly solvable phase. In the limit where these interactions are weak, we treat them within mean-field theory and present the resulting phase diagrams. We discuss the nature of the transitions between various phases. Our results show the richness of possible ground states in closely related magnetic systems.

  9. The slow expansion with nonminimal derivative coupling and its conformal dual

    NASA Astrophysics Data System (ADS)

    Cai, Yong; Piao, Yun-Song

    2016-03-01

    We show that the primordial gravitational wave with scale-invariant spectrum might emerge from a nearly Minkowski space, in which the gravity is asymptotic-past free. We illustrate it with a model, in which the derivative of background scalar field nonminimally couples to gravity. We also show that since here the tensor perturbation is dominated by its growing mode, mathematically our slowly expanding background is conformally dual to the matter contraction, but there is no the anisotropy problem.

  10. Killing Initial Data on spacelike conformal boundaries

    NASA Astrophysics Data System (ADS)

    Paetz, Tim-Torben

    2016-08-01

    We analyze Killing Initial Data on Cauchy surfaces in conformally rescaled vacuum space-times satisfying Friedrich's conformal field equations. As an application, we derive the KID equations on a spacelike ℐ-.

  11. Electric field gradients at 181Ta probe in ZrNi: Results from perturbed angular correlation and first-principles calculations

    NASA Astrophysics Data System (ADS)

    Dey, C. C.; Das, Rakesh; Srivastava, S. K.

    2015-07-01

    Results of temperature dependent perturbed angular correlation (PAC) measurements in the equiatomic ZrNi alloy have been reported for the first time using 181Hf probe. At room temperature, values of quadrupole frequency and asymmetry parameter for the major component (~80%) are found to be ωQ=26.8(4) Mrad/s, and η=0.413(7). The resulting electric field gradient comes out to be Vzz=2.99 ×1017 V/cm2 and this corresponds to the probe nuclei occupying the regular substitutional Zr sites. In ZrNi system, no magnetic interaction is observed down to 77 K indicating absence of any magnetism in this material. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies on an inactive but similarly prepared sample confirm the dominant presence of the orthorhombic ZrNi phase in the sample. A complementary density functional theory (DFT) calculation results in Vzz=-2.35×1017 V/cm2, η=0.46 at the 181Ta probe impurity site and zero magnetic moment on each atomic site, in close agreement with the experimental results. Furthermore, it is found that electric field gradient for the regular component follows a T3/2 temperature dependence between 77 and 353 K, beyond which it varies linearly with temperature.

  12. Dynamical screening effects in correlated electron materials-a progress report on combined many-body perturbation and dynamical mean field theory: 'GW + DMFT'.

    PubMed

    Biermann, Silke

    2014-04-30

    We give a summary of recent progress in the field of electronic structure calculations for materials with strong electronic Coulomb correlations. The discussion focuses on developments beyond the by now well established combination of density functional and dynamical mean field theory dubbed 'LDA + DMFT'. It is organized around the description of dynamical screening effects in the solid. Indeed, screening in the solid gives rise to dynamical local Coulomb interactions U(ω) (Aryasetiawan et al 2004 Phys. Rev. B 70 195104), and this frequency dependence leads to effects that cannot be neglected in a truly first principles description. We review the recently introduced extension of LDA + DMFT to dynamical local Coulomb interactions 'LDA + U(ω) + DMFT' (Casula et al 2012 Phys. Rev. B 85 035115, Werner et al 2012 Nature Phys. 1745-2481). A reliable description of dynamical screening effects is also a central ingredient of the 'GW + DMFT' scheme (Biermann et al 2003 Phys. Rev. Lett. 90 086402), a combination of many-body perturbation theory in Hedin's GW approximation and dynamical mean field theory. Recently, the first GW + DMFT calculations including dynamical screening effects for real materials have been achieved, with applications to SrV O3 (Tomczak et al 2012 Europhys. Lett. 100 67001, Tomczak et al Phys. Rev. B submitted (available electronically as arXiv:1312.7546)) and adatom systems on surfaces (Hansmann et al 2013 Phys. Rev. Lett. 110 166401). We review these and comment on further perspectives in the field. This review is an attempt to put elements of the original works into the broad perspective of the development of truly first principles techniques for correlated electron materials. PMID:24722486

  13. Extended conformal algebras

    NASA Astrophysics Data System (ADS)

    Bouwknegt, Peter

    1988-06-01

    We investigate extensions of the Virasoro algebra by a single primary field of integer or halfinteger conformal dimension Δ. We argue that for vanishing structure constant CΔΔΔ, the extended conformal algebra can only be associative for a generic c-value if Δ=1/2, 1, 3/2, 2 or 3. For the other Δ<=5 we compute the finite set of allowed c-values and identify the rational solutions. The case CΔΔΔ≠0 is also briefly discussed. I would like to thank Kareljan Schoutens for discussions and Sander Bais for a careful reading of the manuscript.

  14. Charged conformal Killing spinors

    SciTech Connect

    Lischewski, Andree

    2015-01-15

    We study the twistor equation on pseudo-Riemannian Spin{sup c}-manifolds whose solutions we call charged conformal Killing spinors (CCKSs). We derive several integrability conditions for the existence of CCKS and study their relations to spinor bilinears. A construction principle for Lorentzian manifolds admitting CCKS with nontrivial charge starting from CR-geometry is presented. We obtain a partial classification result in the Lorentzian case under the additional assumption that the associated Dirac current is normal conformal and complete the classification of manifolds admitting CCKS in all dimensions and signatures ≤5 which has recently been initiated in the study of supersymmetric field theories on curved space.

  15. Topology and perturbation theory

    NASA Astrophysics Data System (ADS)

    Manjavidze, J.

    2000-08-01

    This paper contains description of the fields nonlinear modes successive quantization scheme. It is shown that the path integrals for absorption part of amplitudes are defined on the Dirac (δ-like) functional measure. This permits arbitrary transformation of the functional integral variables. New form of the perturbation theory achieved by mapping the quantum dynamics in the space WG of the (action, angle)-type collective variables. It is shown that the transformed perturbation theory contributions are accumulated exactly on the boundary ∂WG. Abilities of the developed formalism are illustrated by the Coulomb problem. This model is solved in the WC=(angle, angular momentum, Runge-Lentz vector) space and the reason of its exact integrability is emptiness of ∂WC.

  16. Cosmological perturbations during radion stabilization

    NASA Astrophysics Data System (ADS)

    Ashcroft, P. R.; van de Bruck, C.; Davis, A.-C.

    2005-01-01

    We consider the evolution of cosmological perturbations during radion stabilization, which we assume to happen after a period of inflation in the early universe. Concentrating on the Randall-Sundrum brane world scenario, we find that, if matter is present both on the positive and negative tension branes, the coupling of the radion to matter fields could have significant impact on the evolution of the curvature perturbation and on the production of entropy perturbations. We investigate both the case of a long-lived and a short-lived radion and outline similarities and differences to the curvaton scenario.

  17. A conformal truncation framework for infinite-volume dynamics

    NASA Astrophysics Data System (ADS)

    Katz, Emanuel; Khandker, Zuhair U.; Walters, Matthew T.

    2016-07-01

    We present a new framework for studying conformal field theories deformed by one or more relevant operators. The original CFT is described in infinite volume using a basis of states with definite momentum, P , and conformal Casimir, C. The relevant deformation is then considered using lightcone quantization, with the resulting Hamiltonian expressed in terms of this CFT basis. Truncating to states with C ≤ C_{max } , one can numerically find the resulting spectrum, as well as other dynamical quantities, such as spectral densities of operators. This method requires the introduction of an appropriate regulator, which can be chosen to preserve the conformal structure of the basis. We check this framework in three dimensions for various perturbative deformations of a free scalar CFT, and for the case of a free O( N ) CFT deformed by a mass term and a non-perturbative quartic interaction at large- N . In all cases, the truncation scheme correctly reproduces known analytic results. We also discuss a general procedure for generating a basis of Casimir eigenstates for a free CFT in any number of dimensions.

  18. CONSTRAINTS ON SCALAR AND TENSOR PERTURBATIONS IN PHENOMENOLOGICAL AND TWO-FIELD INFLATION MODELS: BAYESIAN EVIDENCES FOR PRIMORDIAL ISOCURVATURE AND TENSOR MODES

    SciTech Connect

    Vaeliviita, Jussi; Savelainen, Matti; Talvitie, Marianne; Kurki-Suonio, Hannu; Rusak, Stanislav

    2012-07-10

    We constrain cosmological models where the primordial perturbations have an adiabatic and a (possibly correlated) cold dark matter (CDM) or baryon isocurvature component. We use both a phenomenological approach, where the power spectra of primordial perturbations are parameterized with amplitudes and spectral indices, and a slow-roll two-field inflation approach where slow-roll parameters are used as primary parameters, determining the spectral indices and the tensor-to-scalar ratio. In the phenomenological case, with CMB data, the upper limit to the CDM isocurvature fraction is {alpha} < 6.4% at k = 0.002 Mpc{sup -1} and 15.4% at k = 0.01 Mpc{sup -1}. The non-adiabatic contribution to the CMB temperature variance is -0.030 < {alpha}{sub T} < 0.049 at the 95% confidence level. Including the supernova (SN) (or large-scale structure) data, these limits become {alpha} < 7.0%, 13.7%, and -0.048 < {alpha}{sub T} < 0.042 (or {alpha} < 10.2%, 16.0%, and -0.071 < {alpha}{sub T} < 0.024). The CMB constraint on the tensor-to-scalar ratio, r < 0.26 at k = 0.01 Mpc{sup -1}, is not affected by the non-adiabatic modes. In the slow-roll two-field inflation approach, the spectral indices are constrained close to 1. This leads to tighter limits on the isocurvature fraction; with the CMB data {alpha} < 2.6% at k = 0.01 Mpc{sup -1}, but the constraint on {alpha}{sub T} is not much affected, -0.058 < {alpha}{sub T} < 0.045. Including SN (or LSS) data, these limits become {alpha} < 3.2% and -0.056 < {alpha}{sub T} < 0.030 (or {alpha} < 3.4% and -0.063 < {alpha}{sub T} < -0.008). In addition to the generally correlated models, we study also special cases where the adiabatic and isocurvature modes are uncorrelated or fully (anti)correlated. We calculate Bayesian evidences (model probabilities) in 21 different non-adiabatic cases and compare them to the corresponding adiabatic models, and find that in all cases the data support the pure adiabatic model.

  19. A Comparison of Out-of-Field Dose and Its Constituent Components for Intensity-Modulated Radiation Therapy Versus Conformal Radiation Therapy: Implications for Carcinogenesis

    SciTech Connect

    Ruben, Jeremy D.; Lancaster, Craig M.; Jones, Phillip; Smith, Ryan L.

    2011-12-01

    Purpose: To investigate differences in scatter and leakage between 6-MV intensity-modulated radiation therapy (IMRT) and three-dimensional conformal radiation therapy (3DCRT); to describe the relative contributions of internal patient scatter, collimator scatter, and head leakage; and to discuss implications for second cancer induction. Methods and Materials: Dose was measured at increasing distances from the field edge in a water bath with a sloping wall (1) under full scatter conditions, (2) with the field edge abutting but outside the bath to prevent internal (water) scatter, and (3) with the beam aperture plugged to reflect leakage only. Results: Internal patient scatter from IMRT is 11% lower than 3DCRT, but collimator scatter and head leakage are five and three times higher, respectively. Ultimately, total scattered dose is 80% higher with IMRT; however this difference is small in absolute terms, being 0.14% of prescribed dose. Secondary dose from 3DCRT is mostly due to internal patient scatter, which contributes 70% of the total and predominates until 25 cm from the field edge. For IMRT, however, machine scatter/leakage is the dominant source, contributing 65% of the secondary dose. Internal scatter predominates for just the first 10 cm from field edge, collimator scatter for the next 10 cm, and head leakage thereafter. Conclusions: Out-of-field dose is 80% higher with IMRT, but differences are tiny in absolute terms. Reductions in internal patient scatter with IMRT are outweighed by increased machine scatter and leakage, at least for small fields. Reductions from IMRT in dose to tissues within the portals and in internal scatter, which predominates close to the field edge, means that calculations based solely on dose to distant tissues may overestimate carcinogenic risks.

  20. Refinement of the AMBER Force Field for Nucleic Acids: Improving the Description of α/γ Conformers

    PubMed Central

    Pérez, Alberto; Marchán, Iván; Svozil, Daniel; Sponer, Jiri; Cheatham, Thomas E.; Laughton, Charles A.; Orozco, Modesto

    2007-01-01

    We present here the parmbsc0 force field, a refinement of the AMBER parm99 force field, where emphasis has been made on the correct representation of the α/γ concerted rotation in nucleic acids (NAs). The modified force field corrects overpopulations of the α/γ = (g+,t) backbone that were seen in long (more than 10 ns) simulations with previous AMBER parameter sets (parm94-99). The force field has been derived by fitting to high-level quantum mechanical data and verified by comparison with very high-level quantum mechanical calculations and by a very extensive comparison between simulations and experimental data. The set of validation simulations includes two of the longest trajectories published to date for the DNA duplex (200 ns each) and the largest variety of NA structures studied to date (15 different NA families and 97 individual structures). The total simulation time used to validate the force field includes near 1 μs of state-of-the-art molecular dynamics simulations in aqueous solution. PMID:17351000

  1. Di-Jet Conical Correlations Associated with Heavy Quark Jets in anti-de Sitter Space/Conformal Field Theory Correspondence

    SciTech Connect

    Noronha, Jorge; Gyulassy, Miklos; Torrieri, Giorgio

    2009-03-13

    We show that far zone Mach and diffusion wake 'holograms' produced by supersonic strings in anti-de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict N{sub c}{yields}{infinity} supergravity limit if Cooper-Frye hadronization is assumed. However, a special nonequilibrium 'neck' zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the velocity of associated identified heavy quark jets at the BNL Relativistic Heavy Ion Collider and CERN LHC will provide a direct test of the nonperturbative dynamics involved in the coupling between jets and the strongly coupled quark-gluon plasma implied by AdS/CFT correspondence.

  2. Di-jet conical correlations associated with heavy quark jets in anti-de sitter space/conformal field theory correspondence.

    PubMed

    Noronha, Jorge; Gyulassy, Miklos; Torrieri, Giorgio

    2009-03-13

    We show that far zone Mach and diffusion wake "holograms" produced by supersonic strings in anti-de Sitter space/conformal field theory (AdS/CFT) correspondence do not lead to observable conical angular correlations in the strict N_{c}-->infinity supergravity limit if Cooper-Frye hadronization is assumed. However, a special nonequilibrium "neck" zone near the jet is shown to produce an apparent sonic boom azimuthal angle distribution that is roughly independent of the heavy quark's velocity. Our results indicate that a measurement of the dependence of the away-side correlations on the velocity of associated identified heavy quark jets at the BNL Relativistic Heavy Ion Collider and CERN LHC will provide a direct test of the nonperturbative dynamics involved in the coupling between jets and the strongly coupled quark-gluon plasma implied by AdS/CFT correspondence. PMID:19392107

  3. Detachment stabilization with n/m=1/1 resonant magnetic perturbation field applied to the stochastic magnetic boundary of the Large Helical Device

    SciTech Connect

    Kobayashi, M.; Masuzaki, S.; Yamada, I.; Tamura, N.; Sato, K.; Goto, M.; Narushima, Y.; Akiyama, T.; Miyazawa, J.; Shoji, M.; Morita, S.; Peterson, B. J.; Funaba, H.; Ohyabu, N.; Narihara, K.; Morisaki, T.; Yamada, H.; Komori, A.; Feng, Y.; Reiter, D.

    2010-05-15

    It is found that the remnant island structure created by n/m=1/1 resonant magnetic perturbation field in the stochastic magnetic boundary of the Large Helical Device (LHD) [A. Komori et al., Nucl. Fusion 49, 104015 (2009)] has a stabilizing effect on formation of radiating plasma, realizing stably sustained divertor detachment operation with the core plasma being unaffected. The data from the several diagnostics, (profiles of electron temperature and density, radiation and temporal evolution of divertor particle flux) indicate selective cooling around X-point of the island and thus peaked radiation there, which is stabilized outside of the last closed flux surface throughout the detachment phase. The vacuum ultraviolet spectroscopy measurements of high Z impurity (iron) emission shows significant decrease during the detachment, indicating core plasma decontamination. The results from the three-dimensional (3D) edge transport code, edge Monte Carlo 3D (EMC3) [Y. Feng et al., Contrib. Plasma Phys. 44, 57 (2004)]-EIRENE [D. Reiter et al., Fusion Sci. Technol. 47, 172 (2005)] show similar tendency in the radiation pattern. The island size and its radial location are varied to investigate the magnetic topology effects on the detachment control. The divertor particle flux and neutral pressure exhibit intermittent oscillation as well as modification of recycling pattern during the detachment, which are found to reflect the island structure.

  4. Conformational properties of bottle-brush polymers

    NASA Astrophysics Data System (ADS)

    Denesyuk, N. A.

    2003-05-01

    General and renormalized perturbation theories are used to study the conformational properties of a bottle-brush molecule, composed of multiarmed polymer stars grafted regularly onto a flexible backbone. The end-to-end distances of the backbone and of an arm of the middle star are calculated within the first order of perturbation theory. For the high grafting densities of stars, the calculated expressions are generalized with the help of the scaling arguments to give the equivalent power laws. According to these laws, the molecule may adopt a sequence of three different conformations (star-rod-coil) as the length of the backbone grows.

  5. Conformational properties of bottle-brush polymers.

    PubMed

    Denesyuk, N A

    2003-05-01

    General and renormalized perturbation theories are used to study the conformational properties of a bottle-brush molecule, composed of multiarmed polymer stars grafted regularly onto a flexible backbone. The end-to-end distances of the backbone and of an arm of the middle star are calculated within the first order of perturbation theory. For the high grafting densities of stars, the calculated expressions are generalized with the help of the scaling arguments to give the equivalent power laws. According to these laws, the molecule may adopt a sequence of three different conformations (star-rod-coil) as the length of the backbone grows. PMID:12786171

  6. Entanglement entropy after a partial projective measurement in 1  +  1 dimensional conformal field theories: exact results

    NASA Astrophysics Data System (ADS)

    Rajabpour, M. A.

    2016-06-01

    We calculate analytically the Rényi bipartite entanglement entropy {{S}α} of the ground state of 1  +  1 dimensional conformal field theories (CFT) after performing a projective measurement in part of the system. We show that the entanglement entropy in this setup is dependent on the central charge and the operator content of the system. When the measurement region A separates the two parts B and \\bar{B} , the entanglement entropy between B and \\bar{B} decreases like a power-law with respect to the characteristic distance between the two regions with an exponent which is dependent on the rank α of the Rényi entanglement entropy and the smallest scaling dimension present in the system. We check our findings by making numerical calculations on the Klein–Gordon field theory (coupled harmonic oscillators) after fixing the position (partial measurement) of some of the oscillators. We also comment on the post-measurement entanglement entropy in the massive quantum field theories.

  7. Discrete reductive perturbation technique

    SciTech Connect

    Levi, Decio; Petrera, Matteo

    2006-04-15

    We expand a partial difference equation (P{delta}E) on multiple lattices and obtain the P{delta}E which governs its far field behavior. The perturbative-reductive approach is here performed on well-known nonlinear P{delta}Es, both integrable and nonintegrable. We study the cases of the lattice modified Korteweg-de Vries (mKdV) equation, the Hietarinta equation, the lattice Volterra-Kac-Van Moerbeke equation and a nonintegrable lattice KdV equation. Such reductions allow us to obtain many new P{delta}Es of the nonlinear Schroedinger type.

  8. Baryon chiral perturbation theory

    NASA Astrophysics Data System (ADS)

    Scherer, S.

    2012-03-01

    We provide a short introduction to the one-nucleon sector of chiral perturbation theory and address the issue of power counting and renormalization. We discuss the infrared regularization and the extended on-mass-shell scheme. Both allow for the inclusion of further degrees of freedom beyond pions and nucleons and the application to higher-loop calculations. As applications we consider the chiral expansion of the nucleon mass to order Script O(q6) and the inclusion of vector and axial-vector mesons in the calculation of nucleon form factors. Finally, we address the complex-mass scheme for describing unstable particles in effective field theory.

  9. Implementation of a DOD ELAP Conforming Quality System at a FUSRAP Site Field Temporary Radiological Screening Laboratory - 13500

    SciTech Connect

    Winters, M.S.; McElheny, G.; Houston, L.M.; Masset, M.R.; Spector, H.L.

    2013-07-01

    A case study is presented on specific program elements that supported the transition of a temporary field radiological screening lab to an accredited operation capable of meeting client quality objectives for definitive results data. The temporary field lab is located at the Formerly Utilized Sites Remedial Action Program Linde Site in Tonawanda, NY. The site is undergoing remediation under the direction of the United States Army Corps of Engineers - Buffalo District, with Cabrera Services Inc. as the remediation contractor and operator of the on-site lab. Analysis methods employed in the on-site lab include gross counting of alpha and beta particle activity on swipes and air filters and gamma spectroscopy of soils and other solid samples. A discussion of key program elements and lessons learned may help other organizations considering pursuit of accreditation for on-site screening laboratories. (authors)

  10. PACSAB: Coarse-Grained Force Field for the Study of Protein-Protein Interactions and Conformational Sampling in Multiprotein Systems.

    PubMed

    Emperador, Agustí; Sfriso, Pedro; Villarreal, Marcos Ariel; Gelpí, Josep Lluis; Orozco, Modesto

    2015-12-01

    Molecular dynamics simulations of proteins are usually performed on a single molecule, and coarse-grained protein models are calibrated using single-molecule simulations, therefore ignoring intermolecular interactions. We present here a new coarse-grained force field for the study of many protein systems. The force field, which is implemented in the context of the discrete molecular dynamics algorithm, is able to reproduce the properties of folded and unfolded proteins, in both isolation, complexed forming well-defined quaternary structures, or aggregated, thanks to its proper evaluation of protein-protein interactions. The accuracy and computational efficiency of the method makes it a universal tool for the study of the structure, dynamics, and association/dissociation of proteins. PMID:26597989

  11. Nonlocal gravity: Conformally flat spacetimes

    NASA Astrophysics Data System (ADS)

    Bini, Donato; Mashhoon, Bahram

    2016-04-01

    The field equations of the recent nonlocal generalization of Einstein’s theory of gravitation are presented in a form that is reminiscent of general relativity. The implications of the nonlocal field equations are studied in the case of conformally flat spacetimes. Even in this simple case, the field equations are intractable. Therefore, to gain insight into the nature of these equations, we investigate the structure of nonlocal gravity (NLG) in 2D spacetimes. While any smooth 2D spacetime is conformally flat and satisfies Einstein’s field equations, only a subset containing either a Killing vector or a homothetic Killing vector can satisfy the field equations of NLG.

  12. Physics-based potentials for the coupling between backbone- and side-chain-local conformational states in the united residue (UNRES) force field for protein simulations

    PubMed Central

    Sieradzan, Adam K.; Krupa, Paweł; Scheraga, Harold A.; Liwo, Adam; Czaplewski, Cezary

    2015-01-01

    The UNited RESidue (UNRES) model of polypeptide chains is a coarse-grained model in which each amino-acid residue is reduced to two interaction sites, namely a united peptide group (p) located halfway between the two neighboring α-carbon atoms (Cαs), which serve only as geometrical points, and a united side chain (SC) attached to the respective Cα. Owing to this simplification, millisecond Molecular Dynamics simulations of large systems can be performed. While UNRES predicts overall folds well, it reproduces the details of local chain conformation with lower accuracy. Recently, we implemented new knowledge-based torsional potentials (Krupa et. al. J. Chem. Theory Comput., 2013, 9, 4620–4632) that depend on the virtual-bond dihedral angles involving side chains: Cα ⋯ Cα ⋯ Cα ⋯ SC (τ(1)), SC ⋯ Cα ⋯ Cα ⋯ Cα (τ(2)), and SC ⋯ Cα ⋯ Cα ⋯ SC (τ(3)) in the UNRES force field. These potentials resulted in significant improvement of the simulated structures, especially in the loop regions. In this work, we introduce the physics-based counterparts of these potentials, which we derived from the all-atom energy surfaces of terminally-blocked amino-acid residues by Boltzmann integration over the angles λ(1) and λ(2) for rotation about the Cα ⋯ Cα virtual-bond angles and over the side-chain angles χ. The energy surfaces were, in turn, calculated by using the semiempirical AM1 method of molecular quantum mechanics. Entropy contribution was evaluated with use of the harmonic approximation from Hessian matrices. One-dimensional Fourier series in the respective virtual-bond-dihedral angles were fitted to the calculated potentials, and these expressions have been implemented in the UNRES force field. Basic calibration of the UNRES force field with the new potentials was carried out with eight training proteins, by selecting the optimal weight of the new energy terms and reducing the weight of the regular torsional terms. The force field was

  13. Isocurvature perturbations in extra radiation

    SciTech Connect

    Kawasaki, Masahiro; Miyamoto, Koichi; Nakayama, Kazunori; Sekiguchi, Toyokazu E-mail: miyamone@icrr.u-tokyo.ac.jp E-mail: oyokazu.sekiguchi@nagoya-u.jp

    2012-02-01

    Recent cosmological observations, including measurements of the CMB anisotropy and the primordial helium abundance, indicate the existence of an extra radiation component in the Universe beyond the standard three neutrino species. In this paper we explore the possibility that the extra radiation has isocurvatrue fluctuations. A general formalism to evaluate isocurvature perturbations in the extra radiation is provided in the mixed inflaton-curvaton system, where the extra radiation is produced by the decay of both scalar fields. We also derive constraints on the abundance of the extra radiation and the amount of its isocurvature perturbation. Current observational data favors the existence of an extra radiation component, but does not indicate its having isocurvature perturbation. These constraints are applied to some particle physics motivated models. If future observations detect isocurvature perturbations in the extra radiation, it will give us a hint to the origin of the extra radiation.

  14. Leaf growth is conformal.

    PubMed

    Alim, Karen; Armon, Shahaf; Shraiman, Boris I; Boudaoud, Arezki

    2016-01-01

    Growth pattern dynamics lie at the heart of morphogenesis. Here, we investigate the growth of plant leaves. We compute the conformal transformation that maps the contour of a leaf at a given stage onto the contour of the same leaf at a later stage. Based on the mapping we predict the local displacement field in the leaf blade and find it to agree with the experimentally measured displacement field to 92%. This approach is applicable to any two-dimensional system with locally isotropic growth, enabling the deduction of the whole growth field just from observation of the tissue contour. PMID:27597439

  15. Vacuum Averages of the Energy-Momentum Tensor of a Scalar Field in Homogeneous Spaces with a Conformal Metric

    NASA Astrophysics Data System (ADS)

    Breev, A. I.; Kozlov, A. V.

    2016-01-01

    Within the framework of the method of orbits, expressions have been obtained for the vacuum averages of the energy-momentum tensor of a scalar field with an arbitrary coupling constant in a spacetime with a nonstationary metric of Robertson-Walker type, where space is a homogeneous Riemannian manifold. It is shown that the vacuum averages of the energy-momentum tensor are determined by the complete set of solutions of the reduced equation with a smaller number of independent variables and with algebraic characteristics of homogeneous space.

  16. Self-consistent field/density functional study of conformational properties of polymers at interfaces: role of intramolecular interactions.

    PubMed

    Bryk, Paweł; Macdowell, Luis G

    2008-09-14

    We study the properties of athermal polymers at hard walls using two different versions of self-consistent field theory (SCFT). We calculate the segment density profiles, center of mass profiles, bond orientation vector profiles, and end-to-end vector distributions and compare with grand canonical Monte Carlo simulations. Using the same excess free energy prescription for both theories, we investigate the role of the excluded volume intramolecular interactions on these properties, show the relation between SCFT and density functional theory, and discuss several numerical implementations of the SCFT method. The phantom chain model gives Gaussian chain statistics independent of the conditions. Including the full intramolecular potential leads to an improved description of the low density regime but it does not produce any significant improvement in the semidiluted and concentrated regimes. We show that a viable compromise is achieved by using the effective field resulting from the phantom chain model and by calculating single chain properties using the full intramolecular potential. PMID:19044937

  17. Conformal data from finite entanglement scaling

    NASA Astrophysics Data System (ADS)

    Stojevic, Vid; Haegeman, Jutho; McCulloch, I. P.; Tagliacozzo, Luca; Verstraete, Frank

    2015-01-01

    In this paper, we apply the formalism of translation invariant (continuous) matrix product states in the thermodynamic limit to (1 +1 ) -dimensional critical models. Finite bond dimension bounds the entanglement entropy and introduces an effective finite correlation length, so that the state is perturbed away from criticality. The assumption that the scaling hypothesis holds for this kind of perturbation is known in the literature as finite entanglement scaling. We provide further evidence for the validity of finite entanglement scaling and based on this formulate a scaling algorithm to estimate the central charge and critical exponents of the conformally invariant field theories describing the critical models under investigation. The algorithm is applied to three exemplary models; the cMPS version to the nonrelativistic Lieb-Liniger model and the relativistic massless boson, and MPS version to the one-dimensional quantum Ising model at the critical point. Another new aspect to our approach is that we directly use the (c)MPS induced correlation length rather than the bond dimension as scaling parameter. This choice is motivated by several theoretical arguments as well as by the remarkable accuracy of our results.

  18. Generating scale-invariant tensor perturbations in the non-inflationary universe

    NASA Astrophysics Data System (ADS)

    Li, Mingzhe

    2014-09-01

    It is believed that the recent detection of large tensor perturbations strongly favors the inflation scenario in the early universe. This common sense depends on the assumption that Einstein's general relativity is valid at the early universe. In this paper we show that nearly scale-invariant primordial tensor perturbations can be generated during a contracting phase before the radiation dominated epoch if the theory of gravity is modified by the scalar-tensor theory at that time. The scale-invariance protects the tensor perturbations from suppressing at large scales and they may have significant amplitudes to fit BICEP2's result. We construct a model to achieve this purpose and show that the universe can bounce to the hot big bang after long time contraction, and at almost the same time the theory of gravity approaches to general relativity through stabilizing the scalar field. Theoretically, such models are dual to inflation models if we change to the frame in which the theory of gravity is general relativity. Dual models are related by the conformal transformations. With this study we reinforce the point that only the conformal invariant quantities such as the scalar and tensor perturbations are physical. How did the background evolve before the radiation time depends on the frame and has no physical meaning. It is impossible to distinguish different pictures by later time cosmological probes.

  19. Finite element modelling of stress field perturbations and interseismic crustal deformation in the Val d'Agri region, southern Apennines, Italy

    NASA Astrophysics Data System (ADS)

    Candela, Stefania; Mazzoli, Stefano; Megna, Antonella; Santini, Stefano

    2015-08-01

    The Val d'Agri area provides the opportunity to analyse active structures in a seismic region for which a large amount of subsurface data is available. This area, which was struck in 1857 by one of the most destructive earthquakes in Italy (MW = 7.03), represents a unique natural laboratory to gain new insights into geometry, modes and rates of faulting controlling crustal deformation in an actively extending orogen. In this study, a crustal geological section through the southern Apennines is discretized into a finite element model (FEM). We present a 2D elastoplastic FEM that reproduces stress perturbations and strain field around the Val d'Agri active fault system. The influence of fault strand activity on interseismic crustal deformation is tested by a series of computer models, whose predictions are compared with the horizontal velocity components of continuous GPS sites in the region and with stress directions and geological data. The best fit with available geological and geophysical constraints is obtained with a 300 km long, 29 km deep model formed by a multilayer including three components having different rheological characteristics and including several shallow, locked fault segments, which branch into a freely slipping major basement fault at depth. Finite element modelling provides new insights into the controversial and widely debated active tectonic setting of the study area, pointing out the fundamental role played by a structural reactivation process involving inherited, long-lived, mature fault systems at depth. Our FEM, reconciling apparently contrasting geological and geophysical constraints from the study area, points to maximum stress build up and strain accumulation at a depth of 15 ± 5 km. Such a depth range is suggested as the most likely one for the nucleation of large events such as the 1857 Val d'Agri earthquake.

  20. 10. Exploring the Conformal Constraint Equations

    NASA Astrophysics Data System (ADS)

    Butscher, Adrian

    One method of studying the asymptotic structure of spacetime is to apply Penrose's conformal rescaling technique. In this setting, the rescaled Einstein equations for the metric and the conformal factor in the unphysical spacetime degenerate where the conformal factor vanishes, namely at the boundary representing null infinity. This problem can be avoided by means of a technique of H. Friedrich, which replaces the Einstein equations in the unphysical spacetime by an equivalent system of equations which is regular at the boundary. The initial value problem for these equations produces a system of constraint equations known as the conformal constraint equations. This work describes some of the properties of the conformal constraint equations and develops a perturbative method of generating solutions near Euclidean space under certain simplifying assumptions.

  1. Playing the Field(s): An Exploration of Change, Conformity and Conflict in Girls' Understandings of Gendered Physicality in Physical Education

    ERIC Educational Resources Information Center

    Hills, Laura A.

    2006-01-01

    This paper draws on data from a year-long ethnographic study of a group of 12- to 13-year-old girls that explored the processes through which they negotiated gendered physicality within the context of physical education. Bourdieu's concepts of habitus and social fields and McNay's extension of his work underpin a discussion of three contexts where…

  2. Field-theoretical description of deep inelastic scattering

    SciTech Connect

    Geyer, B.; Robaschik, D.; Wieczorek, E.

    1980-01-01

    The most important theoretical notions concerning deep inelastic scattering are reviewed. Topics discussed are the model-independent approach, which is based on the general principles of quantum field theory, the application of quantum chromodynamics to deep inelastic scattering, approaches based on the quark--parton model, the light cone algebra, and conformal invariance, and also investigations in the framework of perturbation theory.

  3. Non-perturbative approach for curvature perturbations in stochastic δ N formalism

    SciTech Connect

    Fujita, Tomohiro; Kawasaki, Masahiro; Tada, Yuichiro E-mail: kawasaki@icrr.u-tokyo.ac.jp

    2014-10-01

    In our previous paper [1], we have proposed a new algorithm to calculate the power spectrum of the curvature perturbations generated in inflationary universe with use of the stochastic approach. Since this algorithm does not need the perturbative expansion with respect to the inflaton fields on super-horizon scale, it works even in highly stochastic cases. For example, when the curvature perturbations are very large or the non-Gaussianities of the curvature perturbations are sizable, the perturbative expansion may break down but our algorithm enables to calculate the curvature perturbations. We apply it to two well-known inflation models, chaotic and hybrid inflation, in this paper. Especially for hybrid inflation, while the potential is very flat around the critical point and the standard perturbative computation is problematic, we successfully calculate the curvature perturbations.

  4. Monitoring Conformational Changes in the Receptor Tyrosine Kinase EGFR.

    PubMed

    Becker, Christian; Öcal, Sinan; Nguyen, Hoang D; Phan, Trang; Keul, Marina; Simard, Jeffrey R; Rauh, Daniel

    2016-06-01

    The receptor tyrosine kinase EGFR is regulated by complex conformational changes, and this conformational control is disturbed in certain types of cancer. Many ligands are known to bind EGFR in its active conformation, thereby preventing ATP from binding. Only a few ligands are known to stabilize EGFR in its inactive conformation, thus providing novel strategies for perturbing EGFR activity. We report a direct binding assay that enables the identification of novel ligands that bind to and stabilize the inactive conformation of EGFR. PMID:26991964

  5. The periodic sℓ(2|1) alternating spin chain and its continuum limit as a bulk logarithmic conformal field theory at c = 0

    NASA Astrophysics Data System (ADS)

    Gainutdinov, A. M.; Read, N.; Saleur, H.; Vasseur, R.

    2015-05-01

    The periodic sℓ(2|1) alternating spin chain encodes (some of) the properties of hulls of percolation clusters, and is described in the continuum limit by a logarithmic conformal field theory (LCFT) at central charge c = 0. This theory corresponds to the strong coupling regime of a sigma model on the complex projective superspace CP 1|1 = U(2|1) /(U(1) × U(1|1)), and the spectrum of critical exponents can be obtained exactly. In this paper we push the analysis further, and determine the main representation theoretic (logarithmic) features of this continuum limit by extending to the periodic case the approach of [1] [N. Read and H. Saleur, Nucl. Phys. B 777 (2007) 316]. We first focus on determining the representation theory of the finite size spin chain with respect to the algebra of local energy densities provided by a representation of the affine Temperley-Lieb algebra at fugacity one. We then analyze how these algebraic properties carry over to the continuum limit to deduce the structure of the space of states as a representation over the product of left and right Virasoro algebras. Our main result is the full structure of the vacuum module of the theory, which exhibits Jordan cells of arbitrary rank for the Hamiltonian.

  6. Potential of discrete Gaussian edge feathering method for improving abutment dosimetry in eMLC-delivered segmented-field electron conformal therapy

    SciTech Connect

    Eley, John G.; Hogstrom, Kenneth R.; Matthews, Kenneth L.; Parker, Brent C.; Price, Michael J.

    2011-12-15

    Purpose: The purpose of this work was to investigate the potential of discrete Gaussian edge feathering of the higher energy electron fields for improving abutment dosimetry in the planning volume when using an electron multileaf collimator (eMLC) to deliver segmented-field electron conformal therapy (ECT). Methods: A discrete (five-step) Gaussian edge spread function was used to match dose penumbras of differing beam energies (6-20 MeV) at a specified depth in a water phantom. Software was developed to define the leaf eMLC positions of an eMLC that most closely fit each electron field shape. The effect of 1D edge feathering of the higher energy field on dose homogeneity was computed and measured for segmented-field ECT treatment plans for three 2D PTVs in a water phantom, i.e., depth from the water surface to the distal PTV surface varied as a function of the x-axis (parallel to leaf motion) and remained constant along the y-axis (perpendicular to leaf motion). Additionally, the effect of 2D edge feathering was computed and measured for one radially symmetric, 3D PTV in a water phantom, i.e., depth from the water surface to the distal PTV surface varied as a function of both axes. For the 3D PTV, the feathering scheme was evaluated for 0.1-1.0-cm leaf widths. Dose calculations were performed using the pencil beam dose algorithm in the Pinnacle{sup 3} treatment planning system. Dose verification measurements were made using a prototype eMLC (1-cm leaf width). Results: 1D discrete Gaussian edge feathering reduced the standard deviation of dose in the 2D PTVs by 34, 34, and 39%. In the 3D PTV, the broad leaf width (1 cm) of the eMLC hindered the 2D application of the feathering solution to the 3D PTV, and the standard deviation of dose increased by 10%. However, 2D discrete Gaussian edge feathering with simulated eMLC leaf widths of 0.1-0.5 cm reduced the standard deviation of dose in the 3D PTV by 33-28%, respectively. Conclusions: A five-step discrete Gaussian edge

  7. Dosimetric Comparison of Involved-Field Three-Dimensional Conformal Photon Radiotherapy and Breast-Sparing Proton Therapy for the Treatment of Hodgkin's Lymphoma in Female Pediatric Patients

    SciTech Connect

    Andolino, David L.; Hoene, Ted; Xiao, Lu; Buchsbaum, Jeffrey; Chang, Andrew L.

    2011-11-15

    Purpose: To assess the potential reduction in breast dose for young girls with Hodgkin's lymphoma (HL) treated with breast-sparing proton therapy (BS-PT) as compared with three-dimensional conformal involved-field photon radiotherapy (3D-CRT). Methods and Materials: The Clarian Health Cancer Registry was queried for female pediatric patients with the diagnosis of HL who received radiotherapy at the Indiana University Simon Cancer Center during 2006-2009. The original CT simulation images were obtained, and 3D-CRT and BS-PT plans delivering 21 Gy or cobalt gray equivalent (CGE) in 14 fractions were created for each patient. Dose-volume histogram data were collected for both 3D-CRT and BS-PT plans and compared by paired t test for correlated samples. Results: The cancer registry provided 10 female patients with Ann Arbor Stage II HL, aged 10-18 years at the time of treatment. Both mean and maximum breast dose were significantly less with BS-PT compared with 3D-CRT: 0.95 CGE vs. 4.70 Gy (p < 0.001) and 21.07 CGE vs. 23.11 Gy (p < 0.001), respectively. The volume of breast receiving 1.0 Gy/CGE and 5.0 Gy/CGE was also significantly less with BS-PT, 194 cm{sup 3} and 93 cm{sup 3}, respectively, compared with 790 cm{sup 3} and 360 cm{sup 3} with 3D-CRT (p = 0.009, 0.013). Conclusion: Breast-sparing proton therapy has the potential to reduce unnecessary breast dose in young girls with HL by as much as 80% relative to involved-field 3D-CRT.

  8. Attitudinal Conformity and Anonymity

    ERIC Educational Resources Information Center

    Tyson, Herbert; Kaplowitz, Stan

    1977-01-01

    Tested college students for conformity when conditions contributing to conformity were absent. Found that social pressures (responding in public, being surveyed by fellow group members) are necessary to produce conformity. (RL)

  9. Computing model independent perturbations in dark energy and modified gravity

    SciTech Connect

    Battye, Richard A.; Pearson, Jonathan A. E-mail: jonathan.pearson@durham.ac.uk

    2014-03-01

    We present a methodology for computing model independent perturbations in dark energy and modified gravity. This is done from the Lagrangian for perturbations, by showing how field content, symmetries, and physical principles are often sufficient ingredients for closing the set of perturbed fluid equations. The fluid equations close once ''equations of state for perturbations'' are identified: these are linear combinations of fluid and metric perturbations which construct gauge invariant entropy and anisotropic stress perturbations for broad classes of theories. Our main results are the proof of the equation of state for perturbations presented in a previous paper, and the development of the required calculational tools.

  10. Parsimony in Protein Conformational Change

    PubMed Central

    Chapman, Brynmor K.; Davulcu, Omar; Skalicky, Jack J.; Brüschweiler, Rafael P.; Chapman, Michael S.

    2015-01-01

    Summary Protein conformational change is analyzed by finding the minimalist backbone torsion angle rotations that superpose crystal structures within experimental error. Of several approaches to enforcing parsimony during flexible least-squares superposition, an ℓ1-norm restraint provided greatest consistency with independent indications of flexibility from NMR relaxation dispersion and chemical shift perturbation in arginine kinase, and four previously studied systems. Crystallographic cross-validation shows that the dihedral parameterization describes conformational change more accurately than rigid-group approaches. The rotations that superpose the principal elements of structure constitute a small fraction of the raw (φ, ψ)-differences that also reflect local conformation and experimental error. Substantial long-range displacements can be mediated by modest dihedral rotations, accommodated even within α-helices and β-sheets without disruption of hydrogen bonding at the hinges. Consistency between ligand-associated and intrinsic motions (in the unliganded state) implies that induced changes tend to follow low-barrier paths between conformational sub-states that are in intrinsic dynamic equilibrium. PMID:26095029

  11. Conformations of organophosphine oxides

    DOE PAGESBeta

    De Silva, Nuwan; Zahariev, Federico; Hay, Benjamin P.; Gordon, Mark S.; Windus, Theresa L.

    2015-07-17

    The conformations of a series of organophosphine oxides, OP(CH3)2R, where R = methyl, ethyl, isopropyl, tert-butyl, vinyl, and phenyl, are predicted using the MP2/cc-pVTZ level of theory. Comparison of potential energy surfaces for rotation about P–C bonds with crystal structure data reveals a strong correlation between predicted location and energetics of minima and histograms of dihedral angle distributions observed in the solid state. In addition, the most stable conformers are those that minimize the extent of steric repulsion between adjacent rotor substituents, and the torsional barriers tend to increase with the steric bulk of the rotating alkyl group. MM3 forcemore » field parameters were adjusted to fit the MP2 results, providing a fast and accurate model for predicting organophosphine oxides shapes—an essential part of understanding the chemistry of these compounds. As a result, the predictive power of the modified MM3 model was tested against MP2/cc-pVTZ conformations for triethylphosphine oxide, OP(CH2CH3)3, and triphenylphosphine oxide, OP(Ph)3.« less

  12. Conformations of organophosphine oxides

    SciTech Connect

    De Silva, Nuwan; Zahariev, Federico; Hay, Benjamin P.; Gordon, Mark S.; Windus, Theresa L.

    2015-07-17

    The conformations of a series of organophosphine oxides, OP(CH3)2R, where R = methyl, ethyl, isopropyl, tert-butyl, vinyl, and phenyl, are predicted using the MP2/cc-pVTZ level of theory. Comparison of potential energy surfaces for rotation about P–C bonds with crystal structure data reveals a strong correlation between predicted location and energetics of minima and histograms of dihedral angle distributions observed in the solid state. In addition, the most stable conformers are those that minimize the extent of steric repulsion between adjacent rotor substituents, and the torsional barriers tend to increase with the steric bulk of the rotating alkyl group. MM3 force field parameters were adjusted to fit the MP2 results, providing a fast and accurate model for predicting organophosphine oxides shapes—an essential part of understanding the chemistry of these compounds. As a result, the predictive power of the modified MM3 model was tested against MP2/cc-pVTZ conformations for triethylphosphine oxide, OP(CH2CH3)3, and triphenylphosphine oxide, OP(Ph)3.

  13. Density perturbation theory

    SciTech Connect

    Palenik, Mark C.; Dunlap, Brett I.

    2015-07-28

    Despite the fundamental importance of electron density in density functional theory, perturbations are still usually dealt with using Hartree-Fock-like orbital equations known as coupled-perturbed Kohn-Sham (CPKS). As an alternative, we develop a perturbation theory that solves for the perturbed density directly, removing the need for CPKS. This replaces CPKS with a true Hohenberg-Kohn density perturbation theory. In CPKS, the perturbed density is found in the basis of products of occupied and virtual orbitals, which becomes ever more over-complete as the size of the orbital basis set increases. In our method, the perturbation to the density is expanded in terms of a series of density basis functions and found directly. It is possible to solve for the density in such a way that it makes the total energy stationary even if the density basis is incomplete.

  14. Microwave spectra and conformational studies of ethylamine from temperature dependent Raman spectra of xenon solutions and ab initio calculations

    NASA Astrophysics Data System (ADS)

    Darkhalil, Ikhlas D.; Nagels, Nick; Herrebout, Wouter A.; van der Veken, Benjamin J.; Gurusinghe, Ranil M.; Tubergen, Michael J.; Durig, James R.

    2014-06-01

    FT-microwave spectroscopy was carried out where the trans conformer was identified to be the most stable conformer. Variable temperature (-60 to -100 °C) studies of the Raman spectra (4000-50 cm-1) of ethylamine, CH3CH2NH2 dissolved in liquefied xenon have been carried out. From these data both conformers have been identified and their relative stabilities obtained. The enthalpy difference has been determined to be 62 ± 6 cm-1 (0.746 ± 0.072 kJ mol-1) with the trans conformer the more stable form. The percentage of the gauche conformer is estimated to be 60% at ambient temperature. The conformational stabilities have been predicted from ab initio calculations with the Møller-Plesset perturbation method to the second order (MP2(full)) and the fourth order (MP4(SDTQ)) as well as with density functional theory by the B3LYP method by utilizing a variety of basis sets. Vibrational assignments have been made for the observed bands which have been predicted by MP2(full)/6-31G(d) ab initio calculations which includes harmonic force fields, frequencies, infrared intensities, Raman activities and depolarization ratios for both conformers. The results are discussed and compared to the corresponding properties of some similar molecule.

  15. The molecular structure, conformation, potential to internal rotation and force field of 2,2,2-trifluoroacetamide as studied by gas electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Gundersen, Snefrid; Samdal, Svein; Seip, Ragnhild; Shorokhov, Dmitry J.; Strand, Tor G.

    1998-04-01

    2,2,2-Trifluoroacetamide (TFA) has been studied by electron diffraction (ED), ab initio Hartree-Fock (HF), density functional theory (DFT), and MP2 calculations. The calculations give one conformation with one of the CF bonds anti to the CO bond and a planar NH 2 group, except for MP2/6-311 + + G∗∗, which predicts a slightly pyramidale NH 2 group. A molecular force field has been determined, and the fundamental frequencies have tentatively been assigned. The refined structural parameters were determined using constrained ED, i.e. ab initio results are included as constraints in the analysis. The structural parameters are: rg(N-H 4) = 1.040(4), rg(CO) = 1.211(2), rg(C-N) = 1.362(4), rg = 1.562(1), rg(C-F 7) = 1.347(1), ∠ αOCN = 126.5(2), ∠ αCCN = 116.3(4), ∠ αCCF 7 = 111.9(1), and ∠ αCNH 4 = 118.5(11). Bond distances are in Å and bond angles in degrees. Uncertainties are one standard deviation from least squares refinement using a diagonal weight matrix and inclusion of the uncertainty in the electron wavelength. The structural parameters have been compared with related amides. The Fourier coefficients V3 and V6 in the potential to internal rotation of the CF 3 group, V(α) = 1/2∗V 3∗(1 - cos(3∗α)) + 1/2∗V 6∗(1 - cos(6∗α)) , are determined to be 2.7(4) and - 0.7(3) kJ/mol, respectively. The syn barrier is experimentally determined to be 2.6(4) kJ/mol, which is in good agreeent with theoretical calculations.

  16. Assessment of Extended-Field Radiotherapy for Stage IIIC Endometrial Cancer Using Three-Dimensional Conformal Radiotherapy, Intensity-Modulated Radiotherapy, and Helical Tomotherapy

    SciTech Connect

    Lian Jidong Mackenzie, Marc; Joseph, Kurian; Pervez, Nadeem; Dundas, George; Urtasun, Raul; Pearcey, Robert

    2008-03-01

    Purpose: To perform a dosimetric comparison of three-dimensional conformal radiotherapy (3D-CRT), intensity-modulated radiotherapy (IMRT), and helical tomotherapy (HT) plans for pelvic and para-aortic RT in postoperative endometrial cancer patients; and to evaluate the integral dose (ID) received by critical structures within the radiation fields. Methods and Materials: We selected 10 patients with Stage IIIC endometrial cancer. For each patient, three plans were created with 3D-CRT, IMRT, and HT. The IMRT and HT plans were both optimized to keep the mean dose to the planning target volume (PTV) the same as that with 3D-CRT. The dosimetry and ID for the critical structures were compared. A paired two-tailed Student t test was used for data analysis. Results: Compared with the 3D-CRT plans, the IMRT plans resulted in lower IDs in the organs at risk (OARs), ranging from -3.49% to -17.59%. The HT plans showed a similar result except that the ID for the bowel increased 0.27%. The IMRT and HT plans both increased the IDs to normal tissue (see and text for definition), pelvic bone, and spine (range, 3.31-19.7%). The IMRT and HT dosimetry showed superior PTV coverage and better OAR sparing than the 3D-CRT dosimetry. Compared directly with IMRT, HT showed similar PTV coverage, lower Ids, and a decreased dose to most OARs. Conclusion: Intensity-modulated RT and HT appear to achieve excellent PTV coverage and better sparing of OARs, but at the expense of increased IDs to normal tissue and skeleton. HT allows for additional improvement in dosimetry and sparing of most OARs.

  17. The molecular structures, conformations and force fields of bis(chloroimino)butanedinitrile as studied by gas-phase electron diffraction and quantum chemical calculations

    NASA Astrophysics Data System (ADS)

    Thomassen, H.; Gundersen, S.; Samdal, S.

    2009-06-01

    Quantum chemical calculations using levels up to MP2(Full)/aug-cc-pVTZ have been applied. B3LYP calculations using the 6-31G* basis set reveal that there are four conformations of bis(chloroimino)butanedinitrile. The planar anti-ZZ conformer with C2h symmetry is the most stable conformer. The non-planar EE conformer with C2 symmetry, the non-planar EZ conformer with C1 symmetry and the non-planar ZZ conformer with C2 symmetry are 16.8, 22.7, 27.2 kJ/mol, respectively, less stable than the planar anti-ZZ conformer according toB3LYP/6-31G* calculations. Calculated frequencies for the planar anti-ZZ conformer have been compared with observed frequencies, and some reassignments have been proposed. Several models have been used in the gas-phase electron diffraction analysis. The most reliable results are expected to be obtained using a dynamic model where the large amplitude motion is simulated by a harmonic angular motion using a Gaussian distribution about the central C sbnd C bond. Only the planar anti-ZZ conformer was used in the final refinements due to the high energy difference to the other conformers. The most important bond distances ( ra, Ångstrom) and bond angles (∠ α, degrees) are [GED/MP2(Full)/aug-cc-pVTZ]: rC 1sbnd C 2 = [1.509(15), 1.460], rC 2 = N 3 = [1.295(6), 1.292], rN 3sbnd Cl 5 = [1.706(5), 1.696], rC 2sbnd C 7 = [1.434(11), 1.421], rC 7tbnd N 9 = [1.165(4), 1.170], ∠C 1sbnd C 2dbnd N 3 = [114.5(11), 115.6], ∠C 2dbnd N 3sbnd Cl 5 = [115.0(4), 115.0], ∠C 1sbnd C 2sbnd C 7 = [118.8(8), 118.5], ∠C 2sbnd C 7tbnd N 9 = [178.2(15), 177.4]. The dihedral angle N 3C 2C 7N 9 is 0°, i.e. the cyano groups are bended towards the Cl atom. Error estimates from electron diffraction are given as: σr = 2.5[σ lsq2 + (0.001r) 2] ½ for bond distances and σ∠ = 2.5σ lsq for bond angles.

  18. Automated Lattice Perturbation Theory

    SciTech Connect

    Monahan, Christopher

    2014-11-01

    I review recent developments in automated lattice perturbation theory. Starting with an overview of lattice perturbation theory, I focus on the three automation packages currently "on the market": HiPPy/HPsrc, Pastor and PhySyCAl. I highlight some recent applications of these methods, particularly in B physics. In the final section I briefly discuss the related, but distinct, approach of numerical stochastic perturbation theory.

  19. Calculating nonadiabatic pressure perturbations during multifield inflation

    NASA Astrophysics Data System (ADS)

    Huston, Ian; Christopherson, Adam J.

    2012-03-01

    Isocurvature perturbations naturally occur in models of inflation consisting of more than one scalar field. In this paper, we calculate the spectrum of isocurvature perturbations generated at the end of inflation for three different inflationary models consisting of two canonical scalar fields. The amount of nonadiabatic pressure present at the end of inflation can have observational consequences through the generation of vorticity and subsequently the sourcing of B-mode polarization. We compare two different definitions of isocurvature perturbations and show how these quantities evolve in different ways during inflation. Our results are calculated using the open source Pyflation numerical package which is available to download.

  20. Conformal symmetry and differential regularization of the three-gluon vertex

    NASA Astrophysics Data System (ADS)

    Freedman, Daniel Z.; Grignani, Gianluca; Johnson, Kenneth; Rius, Nuria

    1992-08-01

    The conformal symmetry of the QCD Lagrangian for massless quarks is broken both by renormalization effects and the gauge fixing procedure. Renormalized primitive divergent amplitudes have the property that their form away from the overall coincident point singularity is fully determined by the bare Lagrangian, and scale dependence is restricted to δ-functions at the singularity. If gauge fixing could be ignored, one would expect these amplitudes to be conformal invariant for non-coincident points. We find that the one-loop three-gluon vertex function Г μvp(x, y, z) is conformal invariant in this sense, if calculated in the background field formalism using the Feynman gauge for internal gluons. It is not vet clear why the expected breaking due to gauge fixing is absent. The conformal property implies that the gluon, ghost, and quark loop contributions to Г μvp are each purely numerical combinations of two universal conformal tensors Dμvp( x, y, z) and Cμvp( x, y, z) whose explicit form is given in the text. Only Dμvp has an ultraviolet divergence, although Cμvp requires a careful definition to resolve the expected ambiguity of a formally linearly divergent quantity. Regularization is straightforward and leads to a renormalized vertex function which satisfies the required Ward identity, and from which the beta function is easily obtained. Exact conformal invariance is broken in higher-loop orders, but we outline a speculative scenario in which the perturbative structure of the vertex function is determined from a conformal invariant primitive core by interplay of the renormalization group equation and Ward identities. Other results which are relevant to the conformal property include the following: (1) An analytic calculation shows that the linear deviation from the Feynman gauge is not conformal invariant, and a separate computation using symbolic manipulation confirms that among Dμbμ background gauges, only the Feynman gauge is conformal invariant. (2