Exploring perturbative conformal field theory in Mellin space
NASA Astrophysics Data System (ADS)
Nizami, Amin A.; Rudra, Arnab; Sarkar, Sourav; Verma, Mritunjay
2017-01-01
We explore the Mellin representation of correlation functions in conformal field theories in the weak coupling regime. We provide a complete proof for a set of Feynman rules to write the Mellin amplitude for a general tree level Feynman diagram involving only scalar operators. We find a factorised form involving beta functions associated to the propagators, similar to tree level Feynman rules in momentum space for ordinary QFTs. We also briefly consider the case where a generic scalar perturbation of the free CFT breaks conformal invariance. Mellin space still has some utility and one can consider non-conformal Mellin representations. In this context, we find that the beta function corresponding to conformal propagator uplifts to a hypergeometric function.
Large Spin Perturbation Theory for Conformal Field Theories
NASA Astrophysics Data System (ADS)
Alday, Luis F.
2017-09-01
We consider conformal field theories around points of large twist degeneracy. Examples of this are theories with weakly broken higher spin symmetry and perturbations around generalized free fields. At the degenerate point we introduce twist conformal blocks. These are eigenfunctions of certain quartic operators and encode the contribution, to a given four-point correlator, of the whole tower of intermediate operators with a given twist. As we perturb around the degenerate point, the twist degeneracy is lifted. In many situations this breaking is controlled by inverse powers of the spin. In such cases the twist conformal blocks can be decomposed into a sequence of functions which we systematically construct. Decomposing the four-point correlator in this basis turns crossing symmetry into an algebraic problem. Our method can be applied to a wide spectrum of conformal field theories in any number of dimensions and at any order in the breaking parameter. As an example, we compute the spectrum of various theories around generalized free fields.
NASA Astrophysics Data System (ADS)
Amoretti, Andrea; Magnoli, Nicodemo
2017-08-01
Statistical systems near a classical critical point have been intensively studied from both theoretical and experimental points of view. In particular, correlation functions are of relevance in comparing theoretical models with the experimental data of real systems. In order to compute physical quantities near a critical point, one needs to know the model at the critical (conformal) point. In this line, recent progress in the knowledge of conformal field theories, through the conformal bootstrap, gives the hope of getting some interesting results also outside of the critical point. In this paper, we will review and clarify how, starting from the knowledge of the critical correlators, one can calculate in a safe way their behavior outside the critical point. The approach illustrated requires the model to be just scale invariant at the critical point. We will clarify the method by applying it to different kind of perturbations of the 2D Ising model.
Integrable perturbations of conformal field theories and Yetter-Drinfeld modules
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.
Fermionic field perturbations of a three-dimensional Lifshitz black hole in conformal gravity
NASA Astrophysics Data System (ADS)
González, P. A.; Vásquez, Yerko; Villalobos, Ruth Noemí
2017-09-01
We study the propagation of massless fermionic fields in the background of a three-dimensional Lifshitz black hole, which is a solution of conformal gravity. The black-hole solution is characterized by a vanishing dynamical exponent. Then we compute analytically the quasinormal modes, the area spectrum, and the absorption cross section for fermionic fields. The analysis of the quasinormal modes shows that the fermionic perturbations are stable in this background. The area and entropy spectrum are evenly spaced. In the low frequency limit, it is observed that there is a range of values of the angular momentum of the mode that contributes to the absorption cross section, whereas it vanishes in the high frequency limit. In addition, by a suitable change of variables a gravitational soliton can also be obtained and the stability of the quasinormal modes are studied and ensured.
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.
Lin, Zhixiong; Van Gunsteren, Wilfred F; Liu, Haiyan
2011-07-30
The one-step free energy perturbation approach can be applied to obtain conformational state-specific free energy differences (FEDs) associated with changes in force field parameters, and thus offers the possibility to consider conformational equilibria during force field parameterization. In this work, using the alanine decapeptide in explicit water solution as a model, the α-helical and β-hairpin state-specific FEDs associated with force field changes between two widely used parameter sets of the GROMOS force field, namely, 43A1 and 53A6, were determined using one-step perturbation. The results mostly deviated by only 1 kJ mol(−1) in absolute or a few percent in relative values from thermodynamic integration results, suggesting that the convergence ranges of one-step perturbation were large enough to cover the substantial changes in nonbonded parameters between the two parameter sets. It was also found that one-step perturbation may give larger errors when the changes from the reference state include a large decrease in van der Waals radius, as indicated by the result for the β-hairpin state-specific free energy change going from 53A6 to 43A1. According to the free energy results, the α-helical state of the alanine decapeptide is destabilized by 15 kJ mol(−1), i.e., 1.5 kJ mol(−1) per residue, relative to the β-hairpin state when going from 43A1 to 53A6, in agreement with previous direct simulations in which native α-helices were often found to be unstable in simulations using 53A6, despite that the 53A6 parameters better reproduce a range of thermodynamic properties of small molecular systems. By applying one-step perturbation to analyze the effects of perturbing individual parameters, the differential stabilization of the two secondary structure states can be traced to the changes in van der Waals parameters, especially a van der Waals parameter involved in third-neighbor interactions. This study provides an example of the efficiency of one
Conformal invariant cosmological perturbations via the covariant approach
Li, Mingzhe; Mou, Yicen E-mail: moinch@mail.ustc.edu.cn
2015-10-01
It is known that some cosmological perturbations are conformal invariant. This facilitates the studies of perturbations within some gravitational theories alternative to general relativity, for example the scalar-tensor theory, because it is possible to do equivalent analysis in a certain frame in which the perturbation equations are simpler. In this paper we revisit the problem of conformal invariances of cosmological perturbations in terms of the covariant approach in which the perturbation variables have clear geometric and physical meanings. We show that with this approach the conformal invariant perturbations are easily identified.
Non-Gaussianity of scalar perturbations generated by conformal mechanisms
Libanov, M.; Mironov, S.; Rubakov, V.
2011-10-15
We consider theories which explain the flatness of the power spectrum of scalar perturbations in the Universe by conformal invariance, such as conformal rolling model and Galilean Genesis. We show that to the leading nonlinear order, perturbations in all models from this class behave in one and the same way, at least if the energy density of the relevant fields is small compared to the total energy density (spectator approximation). We then turn to the intrinsic non-Gaussianities in these models (as opposed to non-Gaussianities that may be generated during subsequent evolution). The intrinsic bispectrum vanishes, so we perform the complete calculation of the trispectrum and compare it with the trispectra of local forms in various limits. The most peculiar feature of our trispectrum is a (fairly mild) singularity in the limit where two momenta are equal in absolute value and opposite in direction (folded limit). Generically, the intrinsic non-Gaussianity can be of detectable size.
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.
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.
Scalar perturbations of nonsingular nonrotating black holes in conformal gravity
NASA Astrophysics Data System (ADS)
Toshmatov, Bobir; Bambi, Cosimo; Ahmedov, Bobomurat; Stuchlík, Zdeněk; Schee, Jan
2017-09-01
We study scalar and electromagnetic perturbations of a family of nonsingular nonrotating black hole spacetimes that are solutions in a large class of conformally invariant theories of gravity. The effective potential for scalar perturbations depends on the exact form of the scaling factor. Electromagnetic perturbations do not feel the scaling factor, and the corresponding quasinormal mode spectrum is the same as in the Schwarzschild metric. We find that these black hole metrics are stable under scalar and electromagnetic perturbations. Assuming that the quasinormal mode spectrum for scalar perturbations is not too different from that for gravitational perturbations, we can expect that the calculation of the quasinormal mode spectrum and the observation with gravitational wave detectors of quasinormal modes from astrophysical black holes can constrain the scaling factor and test these solutions.
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
Multi-field inflation and cosmological perturbations
NASA Astrophysics Data System (ADS)
Gong, Jinn-Ouk
We provide a concise review on multi-field inflation and cosmological perturbations. We discuss convenient and physically meaningful bases in terms of which perturbations can be systematically studied. We give formal accounts on the gauge fixing conditions and present the perturbation action in two gauges. We also briefly review nonlinear perturbations.
Algebraic orbifold conformal field theories
Xu, Feng
2000-01-01
The unitary rational orbifold conformal field theories in the algebraic quantum field theory and subfactor theory framework are formulated. Under general conditions, it is shown that the orbifold of a given unitary rational conformal field theory generates a unitary modular category. Many new unitary modular categories are obtained. It is also shown that the irreducible representations of orbifolds of rank one lattice vertex operator algebras give rise to unitary modular categories and determine the corresponding modular matrices, which has been conjectured for some time. PMID:11106383
Frequency Response of a Protein to Local Conformational Perturbations
Eren, Dilek; Alakent, Burak
2013-01-01
Signals created by local perturbations are known to propagate long distances through proteins via backbone connectivity and nonbonded interactions. In the current study, signal propagation from the flexible ligand binding loop to the rest of Protein Tyrosine Phosphatase 1B (PTP1B) was investigated using frequency response techniques. Using restrained Targeted Molecular Dynamics (TMD) potential on WPD and R loops, PTP1B was driven between its crystal structure conformations at different frequencies. Propagation of the local perturbation signal was manifested via peaks at the fundamental frequency and upper harmonics of 1/f distributed spectral density of atomic variables, such as Cα atoms, dihedral angles, or polar interaction distances. Frequency of perturbation was adjusted high enough (simulation length >∼10×period of a perturbation cycle) not to be clouded by random diffusional fluctuations, and low enough (<∼0.8 ns−1) not to attenuate the propagating signal and enhance the contribution of the side-chains to the dissipation of the signals. Employing Discrete Fourier Transform (DFT) to TMD simulation trajectories of 16 cycles of conformational transitions at periods of 1.2 to 5 ns yielded Cα displacements consistent with those obtained from crystal structures. Identification of the perturbed atomic variables by statistical t-tests on log-log scale spectral densities revealed the extent of signal propagation in PTP1B, while phase angles of the filtered trajectories at the fundamental frequency were used to cluster collectively fluctuating elements. Hydrophobic interactions were found to have a higher contribution to signal transduction between side-chains compared to the role of polar interactions. Most of in-phase fluctuating residues on the signaling pathway were found to have high identity among PTP domains, and located over a wide region of PTP1B including the allosteric site. Due to its simplicity and efficiency, the suggested technique may find wide
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.
Multi-field conformal cosmological attractors
Kallosh, Renata; Linde, Andrei E-mail: alinde@stanford.edu
2013-12-01
We describe a broad class of multi-field inflationary models with spontaneously broken conformal invariance. It generalizes the recently discovered class of cosmological attractors with a single inflaton field [1]. In the new multi-field theories, just as in the single-field models of [1], the moduli space has a boundary (Kähler cone) in terms of the original homogeneous conformal variables. Upon spontaneous breaking of the conformal invariance and switching to the Einstein frame, this boundary moves to infinity in terms of the canonically normalized inflaton field. This results in the exponential stretching and flattening of scalar potentials in the vicinity of the boundary of the moduli space, which makes even very steep potentials perfectly suitable for the slow-roll inflation. These theories, just like their single-field versions, typically lead to inflationary perturbations with n{sub s} = 1−2/N and r = 12/N{sup 2}, where N is the number of e-foldings.
Conformal FDTD modeling wake fields
Jurgens, T.; Harfoush, F.
1991-05-01
Many computer codes have been written to model wake fields. Here we describe the use of the Conformal Finite Difference Time Domain (CFDTD) method to model the wake fields generated by a rigid beam traveling through various accelerating structures. The non- cylindrical symmetry of some of the problems considered here requires the use of a three dimensional code. In traditional FDTD codes, curved surfaces are approximated by rectangular steps. The errors introduced in wake field calculations by such an approximation can be reduced by increasing the mesh size, therefore increasing the cost of computing. Another approach, validated here, deforms Ampere and Faraday contours near a media interface so as to conform to the interface. These improvements of the FDTD method result in better accuracy of the fields at asymptotically no computational cost. This method is also capable of modeling thin wires as found in beam profile monitors, and slots and cracks as found in resistive wall motions. 4 refs., 5 figs.
Inflation and deformation of conformal field theory
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.
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.
Perturbations of ultralight vector field dark matter
NASA Astrophysics Data System (ADS)
Cembranos, J. A. R.; Maroto, A. L.; Núñez Jareño, S. J.
2017-02-01
We study the dynamics of cosmological perturbations in models of dark matter based on ultralight coherent vector fields. Very much as for scalar field dark matter, we find two different regimes in the evolution: for modes with {k}^2≪ Hma, we have a particle-like behaviour indistinguishable from cold dark matter, whereas for modes with {k}^2≫ Hma, we get a wave-like behaviour in which the sound speed is non-vanishing and of order c s 2 ≃ k 2/ m 2 a 2. This implies that, also in these models, structure formation could be suppressed on small scales. However, unlike the scalar case, the fact that the background evolution contains a non-vanishing homogeneous vector field implies that, in general, the evolution of the three kinds of perturbations (scalar, vector and tensor) can no longer be decoupled at the linear level. More specifically, in the particle regime, the three types of perturbations are actually decoupled, whereas in the wave regime, the three vector field perturbations generate one scalar-tensor and two vector-tensor perturbations in the metric. Also in the wave regime, we find that a non-vanishing anisotropic stress is present in the perturbed energy-momentum tensor giving rise to a gravitational slip of order ( Φ - Ψ)/ Φ ˜ c s 2 . Moreover in this regime the amplitude of the tensor to scalar ratio of the scalar-tensor modes is also h/ Φ ˜ c s 2 . This implies that small-scale density perturbations are necessarily associated to the presence of gravity waves in this model. We compare their spectrum with the sensitivity of present and future gravity waves detectors.
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.
Conformal regularization of Einstein's field equations
NASA Astrophysics Data System (ADS)
Röhr, Niklas; Uggla, Claes
2005-09-01
To study asymptotic structures, we regularize Einstein's field equations by means of conformal transformations. The conformal factor is chosen so that it carries a dimensional scale that captures crucial asymptotic features. By choosing a conformal orthonormal frame, we obtain a coupled system of differential equations for a set of dimensionless variables, associated with the conformal dimensionless metric, where the variables describe ratios with respect to the chosen asymptotic scale structure. As examples, we describe some explicit choices of conformal factors and coordinates appropriate for the situation of a timelike congruence approaching a singularity. One choice is shown to just slightly modify the so-called Hubble-normalized approach, and one leads to dimensionless first-order symmetric hyperbolic equations. We also discuss differences and similarities with other conformal approaches in the literature, as regards, e.g., isotropic singularities.
Cauchy Conformal Fields in Dimensions {d > 2}
NASA Astrophysics Data System (ADS)
Friedan, Daniel; Keller, Christoph A.
2016-12-01
Holomorphic fields play an important role in 2d conformal field theory. We generalize them to {d > 2} by introducing the notion of Cauchy conformal fields, which satisfy a first order differential equation such that they are determined everywhere once we know their value on a codimension 1 surface. We classify all the unitary Cauchy fields. By analyzing the mode expansion on the unit sphere, we show that all unitary Cauchy fields are free in the sense that their correlation functions factorize on the 2-point function. We also discuss the possibility of non-unitary Cauchy fields and classify them in d = 3 and 4.
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.
Coadjoint orbits and conformal field theory
Taylor, IV, Washington
1993-08-01
This thesis is primarily a study of certain aspects of the geometric and algebraic structure of coadjoint orbit representations of infinite-dimensional Lie groups. The goal of this work is to use coadjoint orbit representations to construct conformal field theories, in a fashion analogous to the free-field constructions of conformal field theories. The new results which are presented in this thesis are as follows: First, an explicit set of formulae are derived giving an algebraic realization of coadjoint orbit representations in terms of differential operators acting on a polynomial Fock space. These representations are equivalent to dual Verma module representations. Next, intertwiners are explicitly constructed which allow the construction of resolutions for irreducible representations using these Fock space realizations. Finally, vertex operators between these irreducible representations are explicitly constructed as chain maps between the resolutions; these vertex operators allow the construction of rational conformal field theories according to an algebraic prescription.
Maverick Examples of Coset Conformal Field Theories
NASA Astrophysics Data System (ADS)
Dunbar, David C.; Joshi, Keith G.
We present coset conformal field theories whose spectrum is not determined by the identification current method. In these "Maverick" cosets there is a larger symmetry identifying primary fields than under the identification current. We find an A-D-E classification of these Mavericks.
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.
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.
Recent progress in irrational conformal field theory
Halpern, M.B.
1993-09-01
In this talk, I will review the foundations of irrational conformal field theory (ICFT), which includes rational conformal field theory as a small subspace. Highlights of the review include the Virasoro master equation, the Ward identities for the correlators of ICFT and solutions of the Ward identities. In particular, I will discuss the solutions for the correlators of the g/h coset construction and the correlators of the affine-Sugawara nests on g {contains} h{sub 1} {contains} {hor_ellipsis} {contains} h{sub n}. Finally, I will discuss the recent global solution for the correlators of all the ICFT`s in the master equation.
Ising (conformal) fields and cluster area measures
Camia, Federico; Newman, Charles M.
2009-01-01
We provide a representation for the scaling limit of the d = 2 critical Ising magnetization field as a (conformal) random field by using Schramm–Loewner Evolution clusters and associated renormalized area measures. The renormalized areas are from the scaling limit of the critical Fortuin–Kasteleyn clusters and the random field is a convergent sum of the area measures with random signs. Extensions to off-critical scaling limits, to d = 3, and to Potts models are also considered. PMID:19264967
Causality constraints in conformal field theory
Hartman, Thomas; Jain, Sachin; Kundu, Sandipan
2016-05-17
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. As a result, our analysis is restricted to scalar correlators, but we argue that similar methods should also impose nontrivial constraints on the interactions of spinning operators
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.
Adiabatic and isocurvature perturbation projections in multi-field inflation
Gordon, Chris; Saffin, Paul M. E-mail: Paul.Saffin@nottingham.ac.uk
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.
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.
Examples of Subfactors from Conformal Field Theory
NASA Astrophysics Data System (ADS)
Xu, Feng
2017-07-01
Conformal field theory (CFT) in two dimensions provides a rich source of subfactors. The fact that there are so many subfactors coming from CFT have led people to conjecture that perhaps all finite depth subfactors are related to CFT. In this paper we examine classes of subfactors from known CFT. In particular we identify the so called 3^{Z}_2× {Z}_2 subfactor with an intermediate subfactor from conformal inclusion, and construct new subfactors from recent work on holomorphic CFT with central charge 24.
Density Perturbations in the Universe from Massive Vector Fields
Dimopoulos, K.
2007-11-20
I discuss the possibility of using a massive vector field to generate the density perturbation in the Universe. I find that a scale-invariant superhorizon spectrum of vector field perturbations is possible to generate during inflation. The associated curvature perturbation is imprinted onto the Universe following the curvaton scenario. The mechanism does not generate a long-range anisotropy because an oscillating massive vector field behaves as a pressureless isotropic fluid.
Gravity duals for nonrelativistic conformal field theories.
Balasubramanian, Koushik; McGreevy, John
2008-08-08
We attempt to generalize the anti-de Sitter/conformal field theory correspondence to nonrelativistic conformal field theories which are invariant under Galilean transformations. Such systems govern ultracold atoms at unitarity, nucleon scattering in some channels, and, more generally, a family of universality classes of quantum critical behavior. We construct a family of metrics which realize these symmetries as isometries. They are solutions of gravity with a negative cosmological constant coupled to pressureless dust. We discuss realizations of the dust, which include a bulk superconductor. We develop the holographic dictionary and find two-point correlators of the correct form. A strange aspect of the correspondence is that the bulk geometry has two extra noncompact dimensions.
Scalar field perturbations in Hořava-Lifshitz cosmology
NASA Astrophysics Data System (ADS)
Wang, Anzhong; Wands, David; Maartens, Roy
2010-03-01
We study perturbations of a scalar field cosmology in Hořava-Lifshitz gravity, adopting the most general setup without detailed balance but with the projectability condition. We derive the generalized Klein-Gordon equation, which is sixth-order in spatial derivatives. Then we investigate scalar field perturbations coupled to gravity in a flat Friedmann-Robertson-Walker background. In the sub-horizon regime, the metric and scalar field modes have independent oscillations with different frequencies and phases except in particular cases. On super-horizon scales, the perturbations become adiabatic during slow-roll inflation driven by a single field, and the comoving curvature perturbation is constant.
Holographic applications of logarithmic conformal field theories
NASA Astrophysics Data System (ADS)
Grumiller, D.; Riedler, W.; Rosseel, J.; Zojer, T.
2013-12-01
We review the relations between Jordan cells in various branches of physics, ranging from quantum mechanics to massive gravity theories. Our main focus is on holographic correspondences between critically tuned gravity theories in anti-de Sitter space and logarithmic conformal field theories in various dimensions. We summarize the developments in the past five years, include some novel generalizations and provide an outlook on possible future developments.
Comments on conformal Killing vector fields and quantum field theory
Brown, M.R.; Ottewill, A.C.; Siklos, S.T.C.
1982-10-15
We give a comprehensive analysis of those vacuums for flat and conformally flat space-times which can be defined by timelike, hypersurface-orthogonal, conformal Killing vector fields. We obtain formulas for the difference in stress-energy density between any two such states and display the correspondence with the renormalized stress tensors. A brief discussion is given of the relevance of these results to quantum-mechanical measurements made by noninertial observers moving through flat space.
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
Causality constraints in conformal field theory
Hartman, Thomas; Jain, Sachin; Kundu, Sandipan
2016-05-17
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 knownmore » 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. As a result, our analysis is restricted to scalar correlators, but we argue that similar methods should also impose nontrivial constraints on the interactions of spinning operators« less
Characters for Coset Conformal Field Theories and Maverick Examples
NASA Astrophysics Data System (ADS)
Dunbar, David C.; Joshi, Keith G.
We present an example of a coset conformal field theory which cannot be described by the identification current method. To study such examples we determine formulae for the characters of coset conformal field theories.
Conformal field theory on affine Lie groups
Clubok, Kenneth Sherman
1996-04-01
Working directly on affine Lie groups, we construct several new formulations of the WZW model, the gauged WZW model, and the generic affine-Virasoro action. In one formulation each of these conformal field theories (CFTs) is expressed as a one-dimensional mechanical system whose variables are coordinates on the affine Lie group. When written in terms of the affine group element, this formulation exhibits a two-dimensional WZW term. In another formulation each CFT is written as a two-dimensional field theory, with a three- dimensional WZW term, whose fields are coordinates on the affine group. On the basis of these equivalent formulations, we develop a translation dictionary in which the new formulations on the affine Lie group are understood as mode formulations of the conventional formulations on the Lie group. Using this dictionary, we also express each CFT as a three-dimensional field theory on the Lie group with a four-dimensional WZW term. 36 refs.
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.
Plasma-satellite interaction driven magnetic field perturbations
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.
Scale invariance, conformality, and generalized free fields
Dymarsky, Anatoly; Farnsworth, Kara; Komargodski, Zohar; ...
2016-02-16
This paper addresses the question of whether there are 4D Lorentz invariant unitary quantum fi eld theories with scale invariance but not conformal invariance. We present an important loophole in the arguments of Luty-Polchinski-Rattazzi and Dymarsky-Komargodski-Schwimmer-Theisen that is the 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 unlessmore » 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). Finally, despite the invalidity of the general argument of FLP, some of the techniques turn out to be useful in the present context.« less
Scale invariance, conformality, and generalized free fields
Dymarsky, Anatoly; Farnsworth, Kara; Komargodski, Zohar; Luty, Markus A.; Prilepina, Valentina
2016-02-16
This paper addresses the question of whether there are 4D Lorentz invariant unitary quantum fi eld theories with scale invariance but not conformal invariance. We present an important loophole in the arguments of Luty-Polchinski-Rattazzi and Dymarsky-Komargodski-Schwimmer-Theisen that is the 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). Finally, despite the invalidity of the general argument of FLP, some of the techniques turn out to be useful in the present context.
Matrix product approximations to conformal field theories
NASA Astrophysics Data System (ADS)
König, Robert; Scholz, Volkher B.
2017-07-01
We establish rigorous error bounds for approximating correlation functions of conformal field theories (CFTs) by certain finite-dimensional tensor networks. For chiral CFTs, the approximation takes the form of a matrix product state. For full CFTs consisting of a chiral and an anti-chiral part, the approximation is given by a finitely correlated state. We show that the bond dimension scales polynomially in the inverse of the approximation error and sub-exponentially in inverse of the minimal distance between insertion points. We illustrate our findings using Wess-Zumino-Witten models, and show that there is a one-to-one correspondence between group-covariant MPS and our approximation.
Nonlinear gravity from entanglement in conformal field theories
NASA Astrophysics Data System (ADS)
Faulkner, Thomas; Haehl, Felix M.; Hijano, Eliot; Parrikar, Onkar; Rabideau, Charles; Van Raamsdonk, Mark
2017-08-01
In this paper, we demonstrate the emergence of nonlinear gravitational equations directly from the physics of a broad class of conformal field theories. We consider CFT excited states defined by adding sources for scalar primary or stress tensor operators to the Euclidean path integral defining the vacuum state. For these states, we show that up to second order in the sources, the entanglement entropy for all ball-shaped regions can always be represented geometrically (via the Ryu-Takayanagi formula) by an asymptotically AdS geometry. We show that such a geometry necessarily satisfies Einstein's equations perturbatively up to second order, with a stress energy tensor arising from matter fields associated with the sourced primary operators. We make no assumptions about AdS/CFT duality, so our work serves as both a consistency check for the AdS/CFT correspondence and a direct demonstration that spacetime and gravitational physics can emerge from the description of entanglement in conformal field theories.
Suppression of edge-localized modes by magnetic field perturbations
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.
Introduction to string theory and conformal field theory
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.
R{sup 2}-inflation with conformal SM Higgs field
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.
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.
Thermality of eigenstates in conformal field theories
NASA Astrophysics Data System (ADS)
Basu, Pallab; Das, Diptarka; Datta, Shouvik; Pal, Sridip
2017-08-01
The eigenstate thermalization hypothesis (ETH) provides a way to understand how an isolated quantum mechanical system can be approximated by a thermal density matrix. We find a class of operators in (1+1)-dimensional conformal field theories, consisting of quasiprimaries of the identity module, which satisfy the hypothesis only at the leading order in large central charge. In the context of subsystem ETH, this plays a role in the deviation of the reduced density matrices, corresponding to a finite energy density eigenstate from its hypothesized thermal approximation. The universal deviation in terms of the square of the trace-square distance goes as the eighth power of the subsystem fraction and is suppressed by powers of inverse central charge (c ). Furthermore, the nonuniversal deviations from subsystem ETH are found to be proportional to the heavy-light-heavy structure constants which are typically exponentially suppressed in √{h /c }, where h is the conformal scaling dimension of the finite energy density state. We also examine the effects of the leading finite-size corrections.
Takiff superalgebras and conformal field theory
NASA Astrophysics Data System (ADS)
Babichenko, Andrei; Ridout, David
2013-03-01
A class of non-semisimple extensions of Lie superalgebras is studied. They are obtained by adjoining to the superalgebra its adjoint representation as an Abelian ideal. When the superalgebra is of affine Kac-Moody type, a generalization of Sugawara’s construction is shown to give rise to a copy of the Virasoro algebra and so, presumably, to a conformal field theory. Evidence for this is detailed for the extension of the affinization of the superalgebra \\mathfrak {gl} ( 1 \\vert 1): its highest weight irreducible modules are classified using spectral flow, the irreducible supercharacters are computed and a continuum version of the Verlinde formula is verified to give non-negative integer structure coefficients. Interpreting these coefficients as those of the Grothendieck ring of fusion, partial results on the true fusion ring and its indecomposable structures are deduced.
Free □ k scalar conformal field theory
NASA Astrophysics Data System (ADS)
Brust, Christopher; Hinterbichler, Kurt
2017-02-01
We consider the generalizations of the free U( N ) and O( N ) scalar conformal field theories to actions with higher powers of the Laplacian □ k , in general dimension d. We study the spectra, Verma modules, anomalies and OPE of these theories. We argue that in certain d and k, the spectrum contains zero norm operators which are both primary and descendant, as well as extension operators which are neither primary nor descendant. In addition, we argue that in even dimensions d ≤ 2 k, there are well-defined operator algebras which are related to the □ k theories and are novel in that they have a finite number of single-trace states.
Cosmological perturbations from a spectator field during inflation
NASA Astrophysics Data System (ADS)
Wang, Lingfei; Mazumdar, Anupam
2013-05-01
In this paper we will discuss analytically the perturbations created from a slowly rolling subdominant spectator field which decays much before the end of inflation. The quantum fluctuations of such a spectator field can seed perturbations on very large scales and explain the temperature anisotropy in the cosmic microwave background radiation with moderate non-Gaussianity, provided the relevant modes leave the Hubble patch while the spectator is slowly rolling. Furthermore, the perturbations are purely adiabatic since the inflaton decay dominates and creates all the Standard Model degrees of freedom. We will provide two examples for the spectator field potential, one with a step function profile, and the other with an inflection point. In both the cases we will compute higher order curvature perturbations, i.e. local bispectrum and trispectrum, which can be constrained by the forthcoming Planck data.
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.
Internal magnetic field structure of perturbed tokamak equilibria
NASA Astrophysics Data System (ADS)
Park, Jong-Kyu; Menard, Jonathan; Boozer, Allen; Glasser, Alan
2006-10-01
The 3D magnetic field structure of perturbed tokamak equilibria is important for understanding phenomena such as error field correction and plasma flow damping. Perturbed quantities such as plasma displacement and magnetic field can be obtained by minimizing the total potential energy numerically using codes such as the DCON ideal stability code. For error field correction applications, initial work is focusing on determining which external magnetic perturbations tend to drive magnetic islands. Jumps on the rational surfaces in the radial derivative of the normal magnetic field perturbation give the singular currents that arise in an ideal plasma to prevent an island from opening[C. N"uhrenberg and A. H. Boozer, Phys. Plasmas 10, 2840 (2003)]. These currents serve as a measure of the tendency of a perturbation to open a magnetic island. Additionally as a first step benchmarking exercise, we compare the 3D structure of NSTX instabilities as predicted by the DCON and MARS-F codes in the absence of external error fields. Future applications include examining the interplay between external error fields, plasma rotation, and plasma resistivity using the MARS-F code.
Quantum spectral curve as a tool for a perturbative quantum field theory
NASA Astrophysics Data System (ADS)
Marboe, Christian; Volin, Dmytro
2015-10-01
An iterative procedure perturbatively solving the quantum spectral curve of planar N = 4 SYM for any operator in the sl(2) sector is presented. A Mathematica notebook executing this procedure is enclosed. The obtained results include 10-loop computations of the conformal dimensions of more than ten different operators. We prove that the conformal dimensions are always expressed, at any loop order, in terms of multiple zeta-values with coefficients from an algebraic number field determined by the one-loop Baxter equation. We observe that all the perturbative results that were computed explicitly are given in terms of a smaller algebra: single-valued multiple zeta-values times the algebraic numbers.
Joint development in perturbed stress fields near faults
NASA Astrophysics Data System (ADS)
Rawnsley, K. D.; Rives, T.; Petti, J.-P.; Hencher, S. R.; Lumsden, A. C.
1992-09-01
Field evidence is presented for complex spatial and temporal perturbations of an otherwise systematic joint pattern around faults from well exposed faulted rock platforms. Joints propagating in perturbed stress fields will curve to follow the directions of the stress field trajectories. A progressive change in joint direction is observed from unperturbed regions away from faults, to strongly perturbed zones adjacent to faults. This indicates that the joint pattern can reflect perturbations of the regional stress field around faults. In the examples, the stress field perturbations are probably due to points of high friction on the fault plane which concentrate stress and distort the stress field in the surrounding rock. The corresponding joints converge at these points and are sub-parallel to the fault along the remainder of the fault plane. The possibility that a fault plane acts as a free surface contained within an elastic body is considered. In this situation the fault plane induces a rotation of the principal stress axes to become either perpendicular or parallel to the fault. The free surface model seems to explain the metre-scale curvature of joints in the vicinity of existing joints, but at the kilometre scale of a large fault plane the model becomes unrealistic unless the fault is open at the Earth's surface. Two examples are investigated from the Lias of Great Britain; at Nash Point and Robin Hood's Bay. Both comprise sub-horizontal strata of relatively homogeneous lithology and bed thickness, which provide striking examples of joints developed near faults.
Conformational Mobility in Cytochrome P450 3A4 Explored by Pressure-Perturbation EPR Spectroscopy.
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.
Conformational Mobility in Cytochrome P450 3A4 Explored by Pressure-Perturbation EPR Spectroscopy
Davydov, Dmitri R.; Yang, Zhongyu; Davydova, Nadezhda; Halpert, James R.; Hubbell, Wayne L.
2016-01-01
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
Quasi-closed orbit in a harmonically perturbed magnetic field
Stupakov, G.V. )
1992-11-01
The paper generalizes a notion of the closed orbit for the case when the accelertor lattice is perturbed by a time-dependent harmonic dipole field. The problem is motivated by effects of current ripple in a proton accelerator. Our result allows to estimate the amplitude of the beam excursions as a function of the amplitude and the frequency of the perturbation. It predicts that the deviation of the beam increases as the frequency of the ripple approaches the sideband betatron frequency.
C-metric solution for conformal gravity with a conformally coupled scalar field
NASA Astrophysics Data System (ADS)
Meng, Kun; Zhao, Liu
2017-02-01
The C-metric solution of conformal gravity with a conformally coupled scalar field is presented. The solution belongs to the class of Petrov type D spacetimes and is conformal to the standard AdS C-metric appeared in vacuum Einstein gravity. For all parameter ranges, we identify some of the physically interesting static regions and the corresponding coordinate ranges. The solution may contain a black hole event horizon, an acceleration horizon, either of which may be cut by the conformal infinity or be hidden behind the conformal infinity. Since the model is conformally invariant, we also discussed the possible effects of the conformal gauge choices on the structure of the spacetime.
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.
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).
Compensation of Gradient-Induced Magnetic Field Perturbations
Nixon, Terence W.; McIntyre, Scott; Rothman, Douglas L.; de Graaf, Robin A.
2008-01-01
Pulsed magnetic field gradients are essential for MR imaging and localized spectroscopy applications. However, besides the desired linear field gradients, pulsed currents in a strong external magnetic field also generate unwanted effects like eddy currents, gradient coil vibrations and acoustic noise. While the temporal magnetic field perturbations associated with eddy currents lead to spectral line shape distortions and signal loss, the vibration-related modulations lead to anti-symmetrical sidebands of any large signal (i.e. water), thereby obliterating the signals from smaller signals (i.e. metabolites). Here the measurement, characterization and compensation of vibrations-related magnetic field perturbations is presented. Following a quantitative evaluation of the various temporal components of the main magnetic field, a digital B0 magnetic field waveform is generated which reduces all temporal variations of the main magnetic field to within the spectral noise level. PMID:18329304
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.
Finite field-dependent symmetries in perturbative quantum gravity
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.
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.
Trapped energetic ion dynamics affected by localized electric field perturbations
NASA Astrophysics Data System (ADS)
Nishimura, Seiya
2016-01-01
Trapped energetic ion orbits in helical systems are numerically simulated using the Lorentz model. Simulation results of precession drift frequencies of trapped energetic ions are benchmarked by those of analytic solutions. The effects of the electric field perturbation localized at the rational surface on trapped energetic ions are examined, where the perturbation has an arbitrary rotation frequency and an amplitude fixed in time. It is found that the trapped energetic ions resonantly interact with the perturbation, when the rotation frequency of the perturbation is comparable to the precession drift frequencies of trapped energetic ions. The simulation results are suggestive to a mechanism of the energetic-ion-induced interchange mode, which might be associated with the fishbone mode observed in helical systems.
Shape dependence of entanglement entropy in conformal field theories
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 R1,d−1R1,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 CT 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 σCT=π224σCT=π224 in d = 3 CFTs, and the holographic Mezei formula for entanglement entropy across deformed spheres.
Shape dependence of entanglement entropy in conformal field theories
Faulkner, Thomas; Leigh, Robert G.; Parrikar, Onkar
2016-04-14
Here, we study universal features in the shape dependence of entanglement entropy in the vacuum state of a conformal field theory (CFT) on R1,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 also show from a purely field theory calculation that the non-local part of the entanglement density in any CFT is universal, and proportionalmore » to the coefficient CT 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/CT=π2/24 in d = 3 CFTs, and the holographic Mezei formula for entanglement entropy across deformed spheres.« less
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.
Missile launch detection electric field perturbation experiment. Final report
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.
Waterfall field in hybrid inflation and curvature perturbation
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.
Flat connection, conformal field theory and quantum group
Kato, Mitsuhiro.
1989-07-01
General framework of linear first order differential equation for four-point conformal block is studied by using flat connection. Integrability and SL{sub 2} invariance restrict possible form of flat connection. Under a special ansatz classical Yang-Baxter equation appears as an integrability condition and the WZW model turns to be unique conformal field theory in that case. Monodromy property of conformal block can be easily determined by the flat connection. 11 refs.
Keep on moving: discovering and perturbing the conformational dynamics of enzymes.
Bhabha, Gira; Biel, Justin T; Fraser, James S
2015-02-17
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 such
Adiabatic regularization for gauge fields and the conformal anomaly
NASA Astrophysics Data System (ADS)
Chu, Chong-Sun; Koyama, Yoji
2017-03-01
Adiabatic regularization for quantum field theory in conformally flat spacetime is known for scalar and Dirac fermion fields. In this paper, we complete the construction by establishing the adiabatic regularization scheme for the gauge field. We show that the adiabatic expansion for the mode functions and the adiabatic vacuum can be defined in a similar way using Wentzel-Kramers-Brillouin-type (WKB-type) solutions as the scalar fields. As an application of the adiabatic method, we compute the trace of the energy momentum tensor and reproduce the known result for the conformal anomaly obtained by the other regularization methods. The availability of the adiabatic expansion scheme for the gauge field allows one to study various renormalized physical quantities of theories coupled to (non-Abelian) gauge fields in conformally flat spacetime, such as conformal supersymmetric Yang Mills, inflation, and cosmology.
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.
A note on φ-analytic conformal vector fields
NASA Astrophysics Data System (ADS)
Deshmukh, Sharief; Bin Turki, Nasser
2017-09-01
Taking clue from the analytic vector fields on a complex manifold, φ-analytic conformal vector fields are defined on a Riemannian manifold (Deshmukh and Al-Solamy in Colloq. Math. 112(1):157-161, 2008). In this paper, we use φ-analytic conformal vector fields to find new characterizations of the n-sphere Sn(c) and the Euclidean space (Rn,<,> ).
Equivalence of emergent de Sitter spaces from conformal field theory
Asplund, Curtis T.; Callebaut, Nele; Zukowski, Claire
2016-09-27
Recently, two groups have made distinct proposals for a de Sitter space that is emergent from conformal field theory (CFT). The first proposal is that, for two-dimensional holographic CFTs, the kinematic space of geodesics on a space-like slice of the asymptotically anti-de Sitter bulk is two-dimensional de Sitter space (dS_{2}), with a metric that can be derived from the entanglement entropy of intervals in the CFT. In the second proposal, de Sitter dynamics emerges naturally from the first law of entanglement entropy for perturbations around the vacuum state of CFTs. We provide support for the equivalence of these two emergent spacetimes in the vacuum case and beyond. In particular, we study the kinematic spaces of nontrivial solutions of 3d gravity, including the BTZ black string, BTZ black hole, and conical singularities. We argue that the resulting spaces are generically globally hyperbolic spacetimes that support dynamics given boundary conditions at future infinity. For the BTZ black string, corresponding to a thermal state of the CFT, we show that both prescriptions lead to an emergent hyperbolic patch of dS_{2}. As a result, we offer a general method for relating kinematic space and the auxiliary de Sitter space that is valid in the vacuum and thermal cases.
Equivalence of emergent de Sitter spaces from conformal field theory
Asplund, Curtis T.; Callebaut, Nele; Zukowski, Claire
2016-09-27
Recently, two groups have made distinct proposals for a de Sitter space that is emergent from conformal field theory (CFT). The first proposal is that, for two-dimensional holographic CFTs, the kinematic space of geodesics on a space-like slice of the asymptotically anti-de Sitter bulk is two-dimensional de Sitter space (dS2), with a metric that can be derived from the entanglement entropy of intervals in the CFT. In the second proposal, de Sitter dynamics emerges naturally from the first law of entanglement entropy for perturbations around the vacuum state of CFTs. We provide support for the equivalence of these two emergentmore » spacetimes in the vacuum case and beyond. In particular, we study the kinematic spaces of nontrivial solutions of 3d gravity, including the BTZ black string, BTZ black hole, and conical singularities. We argue that the resulting spaces are generically globally hyperbolic spacetimes that support dynamics given boundary conditions at future infinity. For the BTZ black string, corresponding to a thermal state of the CFT, we show that both prescriptions lead to an emergent hyperbolic patch of dS2. As a result, we offer a general method for relating kinematic space and the auxiliary de Sitter space that is valid in the vacuum and thermal cases.« less
Coupling structure of multi-field primordial perturbations
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.
Proton Radiography as an electromagnetic field and density perturbation diagnostic
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
Three level constraints on conformal field theories and string models
Lewellen, D.C.
1989-05-01
Simple tree level constraints for conformal field theories which follow from the requirement of crossing symmetry of four-point amplitudes are presented, and their utility for probing general properties of string models is briefly illustrated and discussed. 9 refs.
Mutual information after a local quench in conformal field theory
NASA Astrophysics Data System (ADS)
Asplund, Curtis T.; Bernamonti, Alice
2014-03-01
We compute the entanglement entropy and mutual information for two disjoint intervals in two-dimensional conformal field theories as a function of time after a local quench, using the replica trick and boundary conformal field theory. We obtain explicit formulas for the universal contributions, which are leading in the regimes of, for example, close or well-separated intervals of fixed length. The results are largely consistent with the quasiparticle picture, in which entanglement above that present in the ground state is carried by pairs of entangled freely propagating excitations. We also calculate the mutual information for two disjoint intervals in a proposed holographic local quench, whose holographic energy-momentum tensor matches the conformal field theory one. We find that the holographic mutual information shows qualitative differences from the conformal field theory results and we discuss possible interpretations of this.
Notes on the Verlinde formula in nonrational conformal field theories
Jego, Charles; Troost, Jan
2006-11-15
We review and extend evidence for the validity of a generalized Verlinde formula, in particular, nonrational conformal field theories. We identify a subset of representations of the chiral algebra in nonrational conformal field theories that give rise to an analogue of the relation between modular S-matrices and fusion coefficients in rational conformal field theories. To that end we review and extend the Cardy-type brane calculations in bosonic and supersymmetric Liouville theory (and its duals) as well as in H{sub 3}{sup +}. We analyze the three-point functions of Liouville theory and of H{sub 3}{sup +} in detail to directly identify the fusion coefficients from the operator product expansion. Moreover, we check the validity of a proposed generic formula for localized brane one-point functions in nonrational conformal field theories.
Bianchi type-I models with conformally invariant scalar field
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.
Entanglement entropy of non-unitary conformal field theory
NASA Astrophysics Data System (ADS)
Bianchini, D.; Castro-Alvaredo, O.; Doyon, B.; Levi, E.; Ravanini, F.
2015-01-01
Here we show that the Rényi entanglement entropy of a region of large size ℓ in a one-dimensional critical model whose ground state breaks conformal invariance (such as in those described by non-unitary conformal field theories), behaves as {{S}n}˜ \\frac{{{c}eff}(n+1)}{6n}log \\ell , where {{c}eff}=c-24Δ \\gt 0 is the effective central charge, c (which may be negative) is the central charge of the conformal field theory and Δ \
Primordial perturbations from dilaton-induced gauge fields
Choi, Kiwoon; Choi, Ki-Young; Kim, Hyungjin; Shin, Chang Sub E-mail: kiyoungchoi@kasi.re.kr E-mail: changsub@physics.rutgers.edu
2015-10-01
We study the primordial scalar and tensor perturbations in inflation scenario involving a spectator dilaton field. In our setup, the rolling spectator dilaton causes a tachyonic instability of gauge fields, leading to a copious production of gauge fields in the superhorizon regime, which generates additional scalar and tensor perturbations through gravitational interactions. Our prime concern is the possibility to enhance the tensor-to-scalar ratio r relative to the standard result, while satisfying the observational constraints. To this end, we allow the dilaton field to be stabilized before the end of inflation, but after the CMB scales exit the horizon. We show that for the inflaton slow roll parameter ε ∼> 10{sup −3}, the tensor-to-scalar ratio in our setup can be enhanced only by a factor of O(1) compared to the standard result. On the other hand, for smaller ε corresponding to a lower inflation energy scale, a much bigger enhancement can be achieved, so that our setup can give rise to an observably large r∼> 10{sup −2} even when ε|| 10{sup −3}. The tensor perturbation sourced by the spectator dilaton can have a strong scale dependence, and is generically red-tilted. We also discuss a specific model to realize our scenario, and identify the parameter region giving an observably large r for relatively low inflation energy scales.
A new generalized Wick theorem in conformal field theory
NASA Astrophysics Data System (ADS)
Takagi, T.
2017-08-01
We describe a new generalized Wick theorem for interacting fields in two-dimensional conformal field theory and briefly discuss its relation to the Borcherds identity and its derivation by an analytic method. We give examples of calculating operator product expansions using the generalized Wick theorem including fermionic fields.
On classification of extremal non-holomorphic conformal field theories
NASA Astrophysics Data System (ADS)
Tener, James E.; Wang, Zhenghan
2017-03-01
Rational chiral conformal field theories are organized according to their genus, which consists of a modular tensor category C and a central charge c. A long-term goal is to classify unitary rational conformal field theories based on a classification of unitary modular tensor categories. We conjecture that for any unitary modular tensor category C , there exists a unitary chiral conformal field theory V so that its modular tensor category {{C}V} is C . In this paper, we initiate a mathematical program in and around this conjecture. We define a class of extremal vertex operator algebras with minimal conformal dimensions as large as possible for their central charge, and non-trivial representation theory. We show that there are finitely many different characters of extremal vertex operator algebras V possessing at most three different irreducible modules. Moreover, we list all of the possible characters for such vertex operator algebras with c≤slant 48 .
Using Perturbation theory to reduce noise in diffusion tensor fields.
Bansal, Ravi; Staib, Lawrence H; Xu, Dongrong; Laine, Andrew F; Liu, Jun; Peterson, Bradley S
2009-08-01
We propose the use of Perturbation theory to reduce noise in Diffusion Tensor (DT) fields. Diffusion Tensor Imaging (DTI) encodes the diffusion of water molecules along different spatial directions in a positive definite, 3 x 3 symmetric tensor. Eigenvectors and eigenvalues of DTs allow the in vivo visualization and quantitative analysis of white matter fiber bundles across the brain. The validity and reliability of these analyses are limited, however, by the low spatial resolution and low Signal-to-Noise Ratio (SNR) in DTI datasets. Our procedures can be applied to improve the validity and reliability of these quantitative analyses by reducing noise in the tensor fields. We model a tensor field as a three-dimensional Markov Random Field and then compute the likelihood and the prior terms of this model using Perturbation theory. The prior term constrains the tensor field to be smooth, whereas the likelihood term constrains the smoothed tensor field to be similar to the original field. Thus, the proposed method generates a smoothed field that is close in structure to the original tensor field. We evaluate the performance of our method both visually and quantitatively using synthetic and real-world datasets. We quantitatively assess the performance of our method by computing the SNR for eigenvalues and the coherence measures for eigenvectors of DTs across tensor fields. In addition, we quantitatively compare the performance of our procedures with the performance of one method that uses a Riemannian distance to compute the similarity between two tensors, and with another method that reduces noise in tensor fields by anisotropically filtering the diffusion weighted images that are used to estimate diffusion tensors. These experiments demonstrate that our method significantly increases the coherence of the eigenvectors and the SNR of the eigenvalues, while simultaneously preserving the fine structure and boundaries between homogeneous regions, in the smoothed tensor
Magnetic field homogeneity perturbations in finite Halbach dipole magnets.
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.
Konik, R. M.; Palmai, T.; Takacs, G.; ...
2015-08-24
We study the SU(2)k Wess-Zumino-Novikov-Witten (WZNW) theory perturbed by the trace of the primary field in the adjoint representation, a theory governing the low-energy behaviour of a class of strongly correlated electronic systems. While the model is non-integrable, its dynamics can be investigated using the numerical technique of the truncated conformal spectrum approach combined with numerical and analytical renormalization groups (TCSA+RG). The numerical results so obtained provide support for a semiclassical analysis valid at k » 1. Namely, we find that the low energy behavior is sensitive to the sign of the coupling constant, λ. Moreover for λ > 0more » this behavior depends on whether k is even or odd. With k even, we find definitive evidence that the model at low energies is equivalent to the massive O(3) sigma model. For k odd, the numerical evidence is more equivocal, but we find indications that the low energy effective theory is critical.« less
Toroidal modeling of penetration of the resonant magnetic perturbation field
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.
Toroidal modeling of penetration of the resonant magnetic perturbation field
NASA Astrophysics Data System (ADS)
Liu, Yueqiang; Kirk, A.; Sun, Y.
2013-04-01
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.
Understanding conformal field theory through parafermions and Chern Simons theory
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.
Understanding conformal field theory through parafermions and Chern Simons theory
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.
Conformal field theory of Painlevé VI
NASA Astrophysics Data System (ADS)
Gamayun, O.; Iorgov, N.; Lisovyy, O.
2012-10-01
Generic Painlevé VI tau function τ ( t) can be interpreted as four-point correlator of primary fields of arbitrary dimensions in 2D CFT with c = 1. Using AGT combinatorial representation of conformal blocks and determining the corresponding structure constants, we obtain full and completely explicit expansion of τ ( t) near the singular points. After a check of this expansion, we discuss examples of conformal blocks arising from Riccati, Picard, Chazy and algebraic solutions of Painlevé VI.
Conformal field theories from deformations of theories with Wn symmetry
NASA Astrophysics Data System (ADS)
Babaro, Juan Pablo; Giribet, Gaston; Ranjbar, Arash
2016-10-01
We construct a set of nonrational conformal field theories that consist of deformations of Toda field theory for s l (n ). In addition to preserving conformal invariance, the theories may still exhibit a remnant infinite-dimensional affine symmetry. The case n =3 is used to illustrate this phenomenon, together with further deformations that yield enhanced Kac-Moody symmetry algebras. For generic n we compute N -point correlation functions on the Riemann sphere and show that these can be expressed in terms of s l (n ) Toda field theory ((N -2 )n +2 ) -point correlation functions.
Bi-conformal vector fields and their applications
NASA Astrophysics Data System (ADS)
García-Parrado, Alfonso; Senovilla, JosA~© M. M.
2004-04-01
We introduce a concept of bi-conformal transformation, as a generalization of conformal ones, by allowing two orthogonal parts of a manifold with metric g to be scaled by different conformal factors. In particular, we study their infinitesimal version, called bi-conformal vector fields. We show that these are characterized by the differential conditions {{\\pounds}_{{\\vec{{\\bm \\xi}}}}} {\\bf P}\\propto {\\bf P} and {{\\pounds}_{{\\vec{{\\bm \\xi}}}}} {\\bm \\Pi} \\propto {\\bm \\Pi} , where P and Π are orthogonal projectors (P + Π = g). Keeping P and Π fixed, the set of bi-conformal vector fields is a Lie algebra which can be finite or infinite dimensional according to the dimensionality of the projectors. We determine (i) when an infinite-dimensional case is feasible and its properties, and (ii) a normal system for the generators in the finite-dimensional case. Its integrability conditions are also analysed, which in particular provides the maximum number of linearly independent solutions. We identify the corresponding maximal spaces, and show a necessary geometric condition for a metric tensor to be a double-twisted product. More general 'breakable' spaces are briefly considered. Many known symmetries are included, such as conformal Killing vectors, Kerr Schild vector fields, kinematic self-similarity, causal symmetries and rigid motions.
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.
NASA Astrophysics Data System (ADS)
Chishtie, Farrukh Ahmed
Pade approximants (PA) have been widely applied in practically all areas of physics. This thesis focuses on developing PA as tools for both perturbative and non-perturbative quantum field theory (QFT). In perturbative QFT, we systematically estimate higher (unknown) loop terms via the asymptotic formula devised by Samuel et al. This algorithm, generally denoted as the asymptotic Pade approximation procedure (APAP), has greatly enhanced scope when it is applied to renormalization-group-(RG-) invariant quantities. A presently-unknown higher-loop quantity can then be matched with the approximant over the entire momentum region of phenomenological interest. Furthermore, the predicted value of the RG coefficients can be compared with the RG-accessible coefficients (at the higher-loop order), allowing a clearer indication of the accuracy of the predicted RG-inaccessible term. This methodology is applied to hadronic Higgs decay rates (H → bb¯ and H → gg, both within the Standard Model and its MSSM extension), Higgs-sector cross-sections ( W+LW- L→ZL ZL ), inclusive semileptonic b → u decays (leading to reduced theoretical uncertainties in the extraction of |Vub|), QCD (Quantum Chromodynamics) correlation functions (scalar-fermionic, scalar-gluonic and vector correlators) and the QCD static potential. APAP is also applied directly to RG beta- and gamma-functions in massive φ4 theory. In non-perturbative QFT we use Pade summation methods to probe the large coupling regions of QCD. In analysing all the possible Pade-approximants to truncated beta-function for QCD, we are able to probe the singularity structure corresponding to the all orders beta-function. Noting the consistent ordering of poles and roots for such approximants (regardless of the next unknown higher-loop contribution), we conclude that these approximants are free of defective (pole) behaviour and hence we can safely draw physical conclusions from them. QCD is shown to have a flavour threshold (6
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.
Generally covariant vs. gauge structure for conformal field theories
Campigotto, M.; Fatibene, L.
2015-11-15
We introduce the natural lift of spacetime diffeomorphisms for conformal gravity and discuss the physical equivalence between the natural and gauge natural structure of the theory. Accordingly, we argue that conformal transformations must be introduced as gauge transformations (affecting fields but not spacetime point) and then discuss special structures implied by the splitting of the conformal group. -- Highlights: •Both a natural and a gauge natural structure for conformal gravity are defined. •Global properties and natural lift of spacetime transformations are described. •The possible definitions of physical state are considered and discussed. •The gauge natural theory has less physical states than the corresponding natural one. •The dynamics forces to prefer the gauge natural structure over the natural one.
Conformal field theory, anomalies and superstrings
Baaquie, B.E.; Chew, C.H.; Oh, C.H.; Phua, K.K. . Dept. of Physics)
1988-01-01
This workshop was the first of a planned series of workshops on high energy physics. The emphasis that t was on the theoretical and mathematical of high energy physics; the next workshop to be held in Beijing in 1988 will have emphasis on the experimental and phenomenological aspects. The workshop was intended to introduce in a pedagogical manner the recent advances in superstrings, anomalies and field theory.
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.
Holographic Dual of a Boundary Conformal Field Theory
Takayanagi, Tadashi
2011-09-02
We propose a holographic dual of a conformal field theory defined on a manifold with boundaries, i.e., boundary conformal field theory (BCFT). Our new holography, which may be called anti-de Sitter BCFT, successfully calculates the boundary entropy or g function in two-dimensional BCFTs and it agrees with the finite part of the holographic entanglement entropy. Moreover, we can naturally derive a holographic g theorem. We also analyze the holographic dual of an interval at finite temperature and show that there is a first order phase transition.
Holographic dual of a boundary conformal field theory.
Takayanagi, Tadashi
2011-09-02
We propose a holographic dual of a conformal field theory defined on a manifold with boundaries, i.e., boundary conformal field theory (BCFT). Our new holography, which may be called anti-de Sitter BCFT, successfully calculates the boundary entropy or g function in two-dimensional BCFTs and it agrees with the finite part of the holographic entanglement entropy. Moreover, we can naturally derive a holographic g theorem. We also analyze the holographic dual of an interval at finite temperature and show that there is a first order phase transition.
Local conformational perturbations of the DNA molecule in the SG-model
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
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
Aspects of integrable and conformal field theories
NASA Astrophysics Data System (ADS)
Moriconi, Marco
1997-08-01
In this thesis we study integrable N = 1 supersymmetric theories in two dimensions that are described as deformations of certain superconformal field theories. These superconformal field theories are non-unitary minimal models of central charges given by cn = [- ]3n(4n + 3)/(2n + 2)/ (cn models) where n = 1,2,/.... These models are the supersymmetrization of the generalized Yang-Lee model and can be obtained as reductions of the supersymmetric sine-Gordon model at some specific values of the coupling constant. After an introduction where we review some of the main aspects of two-dimensional CFT and factorizable scattering we study the thermodynamics of the supersymmetric generalized Yang-Lee models and diagonalize the transfer matrix, obtaining the Thermodynamic Bethe Ansatz (TBA) equations. These equations allow us to compute the ground state energy for a system of N particles in a circle of radius R and we compare the results against the predictions from CFT. This check rules out the necessity of CDD factors and confirms the conjectured S-matrix. We prove a conjecture put forward by E. Melzer relating some TBA systems of N = 2 models and the ones we study. We study the supersymmetric generalized Yang-Lee models on a half-line and find their exact reflection matrix. We prove that the ratio of the amplitudes of reflection for bosons and fermions in the same super-multiplet is universal and extend these results to systems with topological charges. We also find the reflection matrices fur the breathers in the susy sine-Gordon model. Based on a semiclassical analysis we relate the reflection matrices to the actions that preserve integrability and supersymmetry proposed by Inami, Odake and Zhang.
Reconstruction of the Acoustic Field Using a Conformal Array
NASA Technical Reports Server (NTRS)
Valdivia, Nichlas P.; Williams, Earl G.; Klos, Jacob
2006-01-01
Near-field acoustical holography (NAH) requires the measurement of the near-field pressure field over a conformal and closed surface in order to recover the acoustic field on a nearby surface. We are interested in the reconstruction of the acoustic field over the fuselage of a Boeing 757 airplane when pressure data is available over an array of microphones that are conformal to the fuselage surface. In this case the strict NAH theory does not hold, but still there are techniques used to overcome this difficulty. The best known is patch NAH, which has been used for planar surfaces. In this work we will discuss two new techniques used for surfaces with an arbitrarily shape: patch inverse boundary element methods (IBEM) and patch equivalent sources method (ESM). We will discuss the theoretical justification of the method and show reconstructions for in-flight data taken inside a Boeing 757 airplane.
Operator Algebras and Noncommutative Geometric Aspects in Conformal Field Theory
NASA Astrophysics Data System (ADS)
Longo, Roberto
2010-03-01
The Operator Algebraic approach to Conformal Field Theory has been particularly fruitful in recent years (leading for example to the classification of all local conformal nets on the circle with central charge c < 1, jointly with Y. Kawahigashi). On the other hand the Operator Algebraic viewpoint offers a natural perspective for a Noncommutative Geometric context within Conformal Field Theory. One basic point here is to uncover the relevant structures. In this talk I will explain some of the basic steps in this "Noncommutative Geometrization program" up to the recent construction of a spectral triple associated with certain Ramond representations of the Supersymmetric Virasoro net. So Alain Connes framework enters into play. This is a joint work with S. Carpi, Y. Kawahigashi, and R. Hillier.
Signatures of core perturbations in geomagnetic field dynamics - preliminary results
NASA Astrophysics Data System (ADS)
Bury, Agata; Mizerski, Krzysztof
2017-04-01
Earth's magnetic field is continuously evolving in time. Research is carried out in order to understand it's characteristics and also to describe types of perturbations which can exist in the Earth's liquid core. The aim of this work is to analyze the geomagnetic ground observatory data for the occurrence of magnetohydrodynamic (MHD) waves described in literature traveling at the top of the Earth's liquid core. Hourly means data from 150 observatories collected from the World Data Center for Geomagnetism (WDC) were used in this work. Local topocentric magnetic field components: X (East), Y (North), Z (vertical), and also spherical coordinates: Br, Bθ, BΦ were analyzed. Hourly means were averaged to one day means and to one month means, missing values were interpolated by different methods. Fourier analysis and Empirical Mode Decomposition (EMD) method were applied to extract periods of oscillations visible in datasets. Similar analysis was also made for data generated from the IGRF12 model for comparison. The times associated with peaks within these data were identified for all components and plotted versus colatitude and longitude to find possible travelling perturbations. Possible candidates of MHD waves for future investigation will be presented.
Nonlinear superhorizon perturbations of non-canonical scalar field
Takamizu, Yu-ichi; Mukohyama, Shinji E-mail: shinji.mukohyama@ipmu.jp
2009-01-15
We develop a theory of non-linear cosmological perturbations at superhorizon scales for a scalar field with a Lagrangian of the form P(X,{phi}), where X = -{partial_derivative}{sup {mu}}{phi}{partial_derivative}{sub {mu}}{phi} and {phi} is the scalar field. We employ the ADM formalism and the spatial gradient expansion approach to obtain general solutions valid up to the second order in the gradient expansion. This formulation can be applied to, for example, DBI inflation models to investigate superhorizon evolution of non-Gaussianities. With slight modification, we also obtain general solutions valid up to the same order for a perfect fluid with a general equation of state P = P({rho})
The perturbative structure of spin glass field theory
NASA Astrophysics Data System (ADS)
Temesvári, T.
2014-03-01
Cubic replicated field theory is used to study the glassy phase of the short-range Ising spin glass just below the transition temperature, and for systems above, at, and slightly below the upper critical dimension six. The order parameter function is computed up to two-loop order. There are two, well-separated bands in the mass spectrum, just as in mean field theory. The small mass band acts as an infrared cutoff, whereas contributions from the large mass region can be computed perturbatively (d>6), or interpreted by the ɛ-expansion around the critical fixed point (d=6-ɛ). The one-loop calculation of the (momentum-dependent) longitudinal mass, and the whole replicon sector is also presented. The innocuous behavior of the replicon masses while crossing the upper critical dimension shows that the ultrametric replica symmetry broken phase remains stable below six dimensions.
Inflation and reheating in the Starobinsky model with conformal HiggsField
NASA Astrophysics Data System (ADS)
Gorbunov, D. S.; Tokareva, A. A.
2013-12-01
This is a talk presented by A.A. Tokareva at Baikal summer school on physics of elementary particles and astrophysics 2012. We studied the reheating after the Starobinsky inflation and have found that the main process is the inflaton decay to SM gauge fields due to the conformal anomaly. The reheating temperature is low leading to the possibility to detect the gravity wave signal from inflation and evaporation of structures formed after inflation in DECIGO and BBO experiments. Also we give predictions for the parameters of scalar perturbation spectrum at the next-to-leading order of slow roll and obtain a bound on the Higgs mass.
Introduction to conformal field theory and string theory
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.
Minisuperspaces with conformally and minimally coupled scalar fields
NASA Astrophysics Data System (ADS)
Page, Don N.
1991-12-01
One may perform a local field redefinition to transform between gravity minimally coupled to a free scalar field and gravity conformally coupled. However, the allowed field values differ in the two cases. For a minisuperspace consisting of a Friedman-Robertson-Walker geometry and a homogeneous scalar field, the conformal coupling allows a more general class of solutions of the Wheeler-DeWitt equation than does the minimal coupling. Nevertheless, there is a one-to-one correspondence between the bounded solutions in the two cases for k=1. This correspondence exploits an isomorphism between harmonic oscillator wavefunctions and solutions of the massive Klein-Gordon equation in the 1+1 dimensional Rindler wedge.
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.
Reheating dynamics affects non-perturbative decay of spectator fields
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.
On the mutual information in conformal field theory
NASA Astrophysics Data System (ADS)
Chen, Bin; Chen, Lin; Hao, Peng-xiang; Long, Jiang
2017-06-01
In this work, we study the universal behaviors in the mutual information of two disjoint spheres in a conformal field theory (CFT). By using the operator product expansion of the spherical twist operator in terms of the conformal family, we show that the large distance expansion of the mutual information can be cast in terms of the conformal blocks. We develop the 1 /n prescription to compute the coefficients before the conformal blocks. For a single conformal family, the leading nonvanishing contribution to the mutual information comes from the bilinear operators. We show that the coefficients of these operators take universal forms and such universal behavior persists in the bilinear operators with derivatives as well. Consequently the first few leading order contributions to the mutual information in CFT take universal forms. To illustrate our framework, we discuss the free scalars and free fermions in various dimensions. For the free scalars, we compute the mutual information to the next-to-leading order and find good agreement with the improved numerical lattice result. For the free fermion, we compute the leading order result, which is of universal form, and find the good match with the numerical study. Our formalism could be applied to any CFT potentially.
Conformal consistency relations for single-field inflation
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.
Quantum entanglement of local operators in conformal field theories.
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.
Quantum Entanglement of Local Operators in Conformal Field Theories
NASA Astrophysics Data System (ADS)
Nozaki, Masahiro; Numasawa, Tokiro; Takayanagi, Tadashi
2014-03-01
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.
NASA Astrophysics Data System (ADS)
Richmond, A. D.; Maute, A.
2003-04-01
The National Center for Atmospheric Research Thermosphere-Ionosphere-Electrodynamics General-Circulation Model calculates ionospheric and geomagnetic-field-aligned electric currents produced by ionospheric wind dynamo action, taking into account magnetospheric sources at high latitudes. The associated magnetic perturbations at the ground and at low-Earth-orbit (LEO) satellite altitudes are calculated by representing the height-integrated horizontal ionospheric current as a current sheet at 110 km, connected to geomagnetic-field-aligned currents flowing into and out of the top. The horizontal sheet current can be divided into two components: a divergence-free equivalent current which, together with the associated induced Earth currents, is responsible for all of the magnetic perturbations below the current sheet, and a divergent (but not irrotational) current that closes the field-aligned currents above. We call the combination of the field-aligned currents and their closing ionospheric currents the ``nonequivalent'' currents. By definition, these produce no magnetic effect at the ground, but they do produce important magnetic effects at LEO altitudes, generally dominating the component of LEO magnetic perturbations perpendicular to the main geomagnetic field. At high magnetic latitudes the nonequivalent LEO magnetic perturbations are largely toroidal, and are associated with the strong field-aligned currents that couple the ionosphere with the outer magnetosphere. At middle and low magnetic latitudes the nonequivalent LEO magnetic perturbations are largely associated with field-aligned currents that flow between the northern and southern hemispheres, and that can produce east-west perturbations of tens of nanoteslas.
Transverse Field Perturbation For PIP-II SRF Cavities
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.
Effects of high external electric fields on protein conformation
NASA Astrophysics Data System (ADS)
Pompa, Pier Paolo; Bramanti, Alessandro; Maruccio, Giuseppe; del Mercato, Loretta Laureana; Chiuri, Rocco; Cingolani, Roberto; Rinaldi, Ross
2005-06-01
Resistance of biomolecules to high electric fields is a main concern for nanobioelectronics/nanobiosensing applications, and it is also a relevant issue from a fundamental perspective, to understand the dielectric properties and structural dynamics of proteins. In nanoscale devices, biomolecules may experience electric fields as high as 107 V/m in order to elicit charge transport/transfer. Understanding the effects of such fields on their structural integrity is thus crucial to assess the reliability of biomolecular devices. In this study, we show experimental evidence for the retention of native-like fold pattern by proteins embedded in high electric fields. We have tested the metalloprotein azurin, deposited onto SiO2 substrates in air with proper electrode configuration, by applying high static electric fields (up to 106-107 V/m). The effects on the conformational properties of protein molecules have been determined by means of intrinsic fluorescence measurements. Experimental results indicate that no significant field-induced conformational alteration occurs. This behavior is also discussed and supported by theoretical predictions of the intrinsic intra-protein electric fields. As the general features of such inner fields are not peculiar of azurin, the conclusions presented here should have general validity.
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.
On principal admissible representations and conformal field theory
NASA Astrophysics Data System (ADS)
Mathieu, P.; Walton, M. A.
1999-08-01
The principal admissible representations of affine Kac-Moody algebras are studied, with a view to their use in conformal field theory. We discuss the generation of the set of principal admissible highest weights, concentrating mainly on Ar(1) at rational level k. A related algorithm is described that produces the Malikov-Feigen-Fuchs null vectors of these representations. With the principal admissible description of the highest weights, we are able to prove that field identifications (including maverick ones) lead to the canonical description of the primary fields of the nonunitary diagonal coset theories.
New proposal for a holographic boundary conformal field theory
NASA Astrophysics Data System (ADS)
Miao, Rong-Xin; Chu, Chong-Sun; Guo, Wu-Zhong
2017-08-01
We propose a new holographic dual of conformal field theory defined on a manifold with boundaries, i.e., boundary conformal field theory (BCFT). Our proposal can apply to general boundaries and agrees with Takayanagi [Phys. Rev. Lett. 107, 101602 (2011), 10.1103/PhysRevLett.107.101602] for the special case of a disk and half-plane. Using the new proposal of AdS /BCFT , we successfully obtain the expected boundary Weyl anomaly, and the obtained boundary central charges naturally satisfy a c-like theorem holographically. We also investigate the holographic entanglement entropy of BCFT and find that the minimal surface must be normal to the bulk spacetime boundaries when they intersect. Interestingly, the entanglement entropy depends on the boundary conditions of BCFT and the distance to the boundary. The entanglement wedge has an interesting phase transition that is important for the self-consistency of AdS /BCFT .
Algebras in tensor categories and coset conformal field theories
NASA Astrophysics Data System (ADS)
Fröhlich, J.; Fuchs, J.; Runkel, I.; Schweigert, C.
2004-06-01
The coset construction is the most important tool to construct rational conformal field theories with known chiral data. For some cosets at small level, so-called maverick cosets, the familiar analysis using selection and identification rules breaks down. Intriguingly, this phenomenon is linked to the existence of exceptional modular invariants. Recent progress in CFT, based on studying algebras in tensor categories, allows for a universal construction of the chiral data of coset theories which in particular also applies to maverick cosets.
Locality of Gravitational Systems from Entanglement of Conformal Field Theories.
Lin, Jennifer; Marcolli, Matilde; Ooguri, Hirosi; Stoica, Bogdan
2015-06-05
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.
Relating the archetypes of logarithmic conformal field theory
NASA Astrophysics Data System (ADS)
Creutzig, Thomas; Ridout, David
2013-07-01
Logarithmic conformal field theory is a rich and vibrant area of modern mathematical physics with well-known applications to both condensed matter theory and string theory. Our limited understanding of these theories is based upon detailed studies of various examples that one may regard as archetypal. These include the c=-2 triplet model, the Wess-Zumino-Witten model on SL(2;R) at level k=-1/2 >, and its supergroup analogue on GL(1|1). Here, the latter model is studied algebraically through representation theory, fusion and modular invariance, facilitating a subsequent investigation of its cosets and extended algebras. The results show that the archetypes of logarithmic conformal field theory are in fact all very closely related, as are many other examples including, in particular, the SL(2|1) models at levels 1 and -1/2 >. The conclusion is then that the archetypal examples of logarithmic conformal field theory are practically all the same, so we should not expect that their features are in any way generic. Further archetypal examples must be sought.
Parastatistics and conformal field theories in two dimensions
NASA Astrophysics Data System (ADS)
Mansouri, Freydoon; Wu, Xizeng
1989-04-01
The relation between parafermion field theories of order Q and the corresponding fermion field theories with SO(Q) symmetry is studied. It is shown that these theories are related but not identical. The explicit relation between the states and the observables of the two classes of theories are given without using the Klein transformations. The formalism is applied to the free conformally invariant parafermion theories in two dimensions. Their Virasoro algebra and SO(N) Kac-Moody algebra are given. The equivalence of their canonical form of the energy-momentum tensor with the Sugawara-Sommerfield form is also elucidated.
Conformal field theories with infinitely many conservation laws
NASA Astrophysics Data System (ADS)
Todorov, Ivan
2013-02-01
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), 10.1007/s00220-006-0182-2; e-print arXiv:math-ph/0604069v3; B. Bakalov, N. M. Nikolov, K.-H. Rehren, and I. Todorov, "Infinite dimensional Lie algebras in 4D conformal quantum field theory," J. Phys. A Math Theor. 41, 194002 (2008), 10.1088/1751-8113/41/19/194002; e-print arXiv:0711.0627v2 [hep-th
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.
Bootstrapping conformal field theories with the extremal functional method.
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.
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.
Magnetic field perturbation of neural recording and stimulating microelectrodes
NASA Astrophysics Data System (ADS)
Martinez-Santiesteban, Francisco M.; Swanson, Scott D.; Noll, Douglas C.; Anderson, David J.
2007-04-01
To improve the overall temporal and spatial resolution of brain mapping techniques, in animal models, some attempts have been reported to join electrophysiological methods with functional magnetic resonance imaging (fMRI). However, little attention has been paid to the image artefacts produced by the microelectrodes that compromise the anatomical or functional information of those studies. This work presents a group of simulations and MR images that show the limitations of wire microelectrodes and the potential advantages of silicon technology, in terms of image quality, in MRI environments. Magnetic field perturbations are calculated using a Fourier-based method for platinum (Pt) and tungsten (W) microwires as well as two different silicon technologies. We conclude that image artefacts produced by microelectrodes are highly dependent not only on the magnetic susceptibility of the materials used but also on the size, shape and orientation of the electrodes with respect to the main magnetic field. In addition silicon microelectrodes present better MRI characteristics than metallic microelectrodes. However, metallization layers added to silicon materials can adversely affect the quality of MR images. Therefore only those silicon microelectrodes that minimize the amount of metallic material can be considered MR-compatible and therefore suitable for possible simultaneous fMRI and electrophysiological studies. High resolution gradient echo images acquired at 2 T (TR/TE = 100/15 ms, voxel size = 100 × 100 × 100 µm3) of platinum-iridium (Pt-Ir, 90%-10%) and tungsten microwires show a complete signal loss that covers a volume significantly larger than the actual volume occupied by the microelectrodes: roughly 400 times larger for Pt-Ir and 180 for W, at the tip of the microelectrodes. Similar MR images of a single-shank silicon microelectrode only produce a partial volume effect on the voxels occupied by the probe with less than 50% of signal loss.
Static black hole solutions with a self-interacting conformally coupled scalar field
Dotti, Gustavo; Gleiser, Reinaldo J.; Martinez, Cristian
2008-05-15
We study static, spherically symmetric black hole solutions of the Einstein equations with a positive cosmological constant and a conformally coupled self-interacting scalar field. Exact solutions for this model found by Martinez, Troncoso, and Zanelli were subsequently shown to be unstable under linear gravitational perturbations, with modes that diverge arbitrarily fast. We find that the moduli space of static, spherically symmetric solutions that have a regular horizon--and satisfy the weak and dominant energy conditions outside the horizon--is a singular subset of a two-dimensional space parametrized by the horizon radius and the value of the scalar field at the horizon. The singularity of this space of solutions provides an explanation for the instability of the Martinez, Troncoso, and Zanelli spacetimes and leads to the conclusion that, if we include stability as a criterion, there are no physically acceptable black hole solutions for this system that contain a cosmological horizon in the exterior of its event horizon.
Conformal perturbation theory and higher spin entanglement entropy on the torus
NASA Astrophysics Data System (ADS)
Datta, Shouvik; David, Justin R.; Kumar, S. Prem
2015-04-01
We study the free fermion theory in 1+1 dimensions deformed by chemical potentials for holomorphic, conserved currents at finite temperature and on a spatial circle. For a spin-three chemical potential μ, the deformation is related at high temperatures to a higher spin black hole in hs[0] theory on AdS3 spacetime. We calculate the order μ 2 corrections to the single interval Rényi and entanglement entropies on the torus using the bosonized formulation. A consistent result, satisfying all checks, emerges upon carefully accounting for both perturbative and winding mode contributions in the bosonized language. The order μ 2 corrections involve integrals that are finite but potentially sensitive to contact term singularities. We propose and apply a prescription for defining such integrals which matches the Hamiltonian picture and passes several non-trivial checks for both thermal corrections and the Rényi entropies at this order. The thermal corrections are given by a weight six quasi-modular form, whilst the Rényi entropies are controlled by quasi-elliptic functions of the interval length with modular weight six. We also point out the well known connection between the perturbative expansion of the partition function in powers of the spin-three chemical potential and the Gross-Taylor genus expansion of large- N Yang-Mills theory on the torus. We note the absence of winding mode contributions in this connection, which suggests qualitatively different entanglement entropies for the two systems.
The Stochastic Elastica and Excluded-Volume Perturbations of DNA Conformational Ensembles
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
Excitation entanglement entropy in two dimensional conformal field theories
NASA Astrophysics Data System (ADS)
Sheikh-Jabbari, M. M.; Yavartanoo, H.
2016-12-01
We analyze how excitations affect the entanglement entropy for an arbitrary entangling interval in a 2d conformal field theory (CFT) using the holographic entanglement entropy techniques as well as direct CFT computations. We introduce the excitation entanglement entropy ΔhS , the difference between the entanglement entropy generic excitations and their arbitrary conformal descendants denoted through h . The excitation entanglement entropy, unlike the entanglement entropy, is a finite quantity (independent of the cutoff), and hence a good physical observable. We show that the excitation entanglement entropy for any given interval is uniquely specified by a local second order differential equation sourced by the one point function of the energy momentum tensor computed in the excited background state, and two boundary and smoothness conditions. We analyze low and high temperature behavior of the excitation entanglement entropy and show that ΔhS grows as a function of temperature. We prove an "integrated positivity" for the excitation entanglement entropy, that although ΔhS can be positive or negative, its average value is always positive. We also discuss the mutual and multipartite information and (strong) subadditivity inequality in the presence of generic excitations and their conformal descendants.
Effect of External Electric Field Stress on Gliadin Protein Conformation
Singh, Ashutosh; Munshi, Shirin; Raghavan, Vijaya
2013-01-01
A molecular dynamic (MD) modeling approach was applied to evaluate the effect of external electric field on gliadin protein structure and surface properties. Static electric field strengths of 0.001 V/nm and 0.002 V/nm induced conformational changes in the protein but had no significant effect on its surface properties. The study of hydrogen bond evolution during the course of simulation revealed that the root mean square deviation, radius of gyration and secondary structure formation, all depend significantly on the number hydrogen bonds formed. This study demonstrated that it is necessary to gain insight into protein dynamics under external electric field stress, in order to develop the novel food processing techniques that can be potentially used to reduce or eradicate food allergens. PMID:28250397
Non-conformal evolution of magnetic fields during reheating
Calzetta, Esteban; Kandus, Alejandra E-mail: kandus@uesc.br
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.
Non-equilibrium Thermodynamics and Conformal Field Theory
NASA Astrophysics Data System (ADS)
Hollands, Stefan; Longo, Roberto
2017-07-01
We present a model independent, operator algebraic approach to non-equilibrium quantum thermodynamics within the framework of two-dimensional Conformal Field Theory. Two infinite reservoirs in equilibrium at their own temperatures and chemical potentials are put in contact through a defect line, possibly by inserting a probe. As time evolves, the composite system then approaches a non-equilibrium steady state that we describe. In particular, we re-obtain recent formulas of Bernard and Doyon (Ann Henri Poincaré 16:113-161, 2015).
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
Yuzwa, Scott A; Cheung, Adrienne H; Okon, Mark; McIntosh, Lawrence P; Vocadlo, David J
2014-04-17
The aggregation of the microtubule-associated protein tau into paired helical filaments to form neurofibrillary tangles constitutes one of the pathological hallmarks of Alzheimer's disease. Tau is post-translationally modified by the addition of N-acetyl-D-glucosamine O-linked to several serine and threonine residues (O-GlcNAc). Previously, increased O-GlcNAcylation of tau has been shown to block the accumulation of tau aggregates within a tauopathy mouse model. Here we show that O-GlcNAc modification of full-length human tau impairs the rate and extent of its heparin-induced aggregation without perturbing its activity toward microtubule polymerization. O-GlcNAcylation, however, does not impact the "global-fold" of tau as measured by a Förster resonance energy transfer assay. Similarly, nuclear magnetic resonance studies demonstrated that O-GlcNAcylation only minimally perturbs the local structural and dynamic features of a tau fragment (residues 353-408) spanning the last microtubule binding repeat to the major GlcNAc-acceptor Ser400. These data indicate that the inhibitory effects of O-GlcNAc on tau aggregation may result from enhanced monomer solubility or the destabilization of fibrils or soluble aggregates, rather than by altering the conformational properties of the monomeric protein. This work further underscores the potential of targeting the O-GlcNAc pathway for potential Alzheimer's disease therapeutics. Copyright © 2014 Elsevier Ltd. All rights reserved.
Perturbative no-hair property of form fields for higher dimensional static black holes
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.
Diffusion and Signatures of Localization in Stochastic Conformal Field Theory
NASA Astrophysics Data System (ADS)
Bernard, Denis; Doyon, Benjamin
2017-09-01
We define a simple model of conformal field theory in random space-time environments, which we refer to as stochastic conformal field theory. This model accounts for the effects of dilute random impurities in strongly interacting critical many-body systems. On one hand, surprisingly, although impurities are separated by macroscopic distances, we find that the infinite-time steady state is factorized on microscopic lengths, a signature of the emergence of localization. The stationary state also displays vanishing energy current and strong uncorrelated spatial fluctuations of local observables. On the other hand, at finite times, the transient shows a crossover from ballistic to diffusive energy propagation. In this regime and a Markovian limit, concentrating on current-generating initial states with a temperature imbalance, we show that the energy current and density satisfy simple dissipative hydrodynamic equations. We describe the space-time scales at which nonequilibrium currents exist. We show that a light-cone effect subsists in the presence of impurities although a momentum burst propagates transiently on a diffusive scale only.
Positive energy conditions in 4D conformal field theory
Farnsworth, Kara; Luty, Markus A.; Prilepina, Valentina
2016-10-03
Here, we argue that all consistent 4D quantum field theories obey a spacetime-averaged weak energy inequality < T00 > ≥ –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 themore » “conformal collider” constraints of Hofman and Maldacena. 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.« less
Positive energy conditions in 4D conformal field theory
Farnsworth, Kara; Luty, Markus A.; Prilepina, Valentina
2016-10-03
Here, we argue that all consistent 4D quantum field theories obey a spacetime-averaged weak energy inequality < T^{00} > ≥ –C/L^{4}, 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. In _{3}D 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.
Spectral sum rules for conformal field theories in arbitrary dimensions
NASA Astrophysics Data System (ADS)
Chowdhury, Subham Dutta; David, Justin R.; Prakash, Shiroman
2017-07-01
We derive spectral sum rules in the shear channel for conformal field theories at finite temperature in general d ≥ 3 dimensions. The sum rules result from the OPE of the stress tensor at high frequency as well as the hydrodynamic behaviour of the theory at low frequencies. The sum rule states that a weighted integral of the spectral density over frequencies is proportional to the energy density of the theory. We show that the proportionality constant can be written in terms the Hofman-Maldacena variables t 2 , t 4 which determine the three point function of the stress tensor. For theories which admit a two derivative gravity dual this proportionality constant is given by d/2(d+1) . We then use causality constraints and obtain bounds on the sum rule which are valid in any conformal field theory. Finally we demonstrate that the high frequency behaviour of the spectral function in the vector and the tensor channel are also determined by the Hofman-Maldacena variables.
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.
Positive energy conditions in 4D conformal field theory
NASA Astrophysics Data System (ADS)
Farnsworth, Kara; Luty, Markus A.; Prilepina, Valentina
2016-10-01
We argue that all consistent 4D quantum field theories obey a spacetime-averaged weak energy inequality < T 00> ≥ - C/L 4, 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. 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.
Higher-rank supersymmetric models and topological conformal field theory
NASA Astrophysics Data System (ADS)
Kawai, Toshiya; Uchino, Taku; Yang, Sung-Kil
1993-03-01
In the first part of this paper we investigate the operator aspect of a higher-rank supersymmetric model which is introduced as a Lie theoretic extension of the N = 2 minimal model with the simplest case su(2) corresponding to the N = 2 minimal model. In particular we identify the analogs of chirality conditions and chiral ring. In the second part we construct a class of topological conformal field theories starting with this higher-rank supersymmetric model. We show the BRST-exactness of the twisted stress-energy tensor, find out physical observables and discuss how to make their correlation functions. It is emphasized that in the case of su(2) the topological field theory constructed in this paper is distinct from the one obtained by twisting the N = 2 minimal model through the usual procedure.
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.
Alien calculus and non perturbative effects in Quantum Field Theory
NASA Astrophysics Data System (ADS)
Bellon, Marc P.
2016-12-01
In many domains of physics, methods for dealing with non-perturbative aspects are required. Here, I want to argue that a good approach for this is to work on the Borel transforms of the quantities of interest, the singularities of which give non-perturbative contributions. These singularities in many cases can be largely determined by using the alien calculus developed by Jean Écalle. My main example will be the two point function of a massless theory given as a solution of a renormalization group equation.
NASA Astrophysics Data System (ADS)
Bershtein, Mikhail; Bonelli, Giulio; Ronzani, Massimiliano; Tanzini, Alessandro
2017-08-01
We show that equivariant Donaldson polynomials of compact toric surfaces can be calculated as residues of suitable combinations of Virasoro conformal blocks, by building on AGT correspondence between N = 2 supersymmetric gauge theories and two-dimensional conformal field theory.
Impact of resistive MHD plasma response on perturbation field sidebands
Orlov, D. M.; Evans, T. E.; Moyer, R. A.; ...
2016-06-03
Here, 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-resonantmore » 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. 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.« less
Impact of resistive MHD plasma response on perturbation field sidebands
Orlov, D. M.; Evans, T. E.; Moyer, R. A.; Lyons, B. C.; Ferraro, N. M.; Park, G-Y
2016-06-03
Here, single fluid linear simulations of a KSTAR RMP ELM suppressed discharge with the M3D-C^{1} 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. 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.
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.
Uncovering the structure of (super)conformal field theories
NASA Astrophysics Data System (ADS)
Liendo, Pedro
Conformal field theories (CFTs) are of central importance in modern theoretical physics, with applications that range from condensed matter physics to particle theory phenomenology. In this Ph.D. thesis we study CFTs from two somehow orthogonal (but complementary) points of view. In the first approach we concentrate our efforts in two specific examples: the Veneziano limit of N = 2 and N = 1 superconformal QCD. The addition of supersymmetry makes these theories amenable to analytical analysis. In particular, we use the correspondence between single trace operators and states of a spin chain to study the integrability properties of each theory. Our results indicate that these theories are not completely integrable, but they do contain some subsectors in which integrability might hold. In the second approach, we consider the so-called "bootstrap program'', which is the ambitious idea that the restrictions imposed by conformal symmetry (crossing symmetry in particular) are so powerful that starting from a few basic assumptions one should be able to fix the form of a theory. In this thesis we apply bootstrap techniques to CFTs in the presence of a boundary. We study two-point functions using analytical and numerical methods. One-loop results were re-obtained from crossing symmetry alone and a variety of numerical bounds for conformal dimensions of operators were obtained. These bounds are quite general and valid for any CFT in the presence of a boundary, in contrast to our first approach where a specific set of theories was studied. A natural continuation of this work is to apply bootstrap techniques to supersymmetric theories. Some preliminary results along these lines are presented.
NASA Astrophysics Data System (ADS)
Kim, Nakwoo
2015-03-01
We consider scalar fields which are coupled to Einstein gravity with a negative cosmological constant, and construct periodic solutions perturbatively. In particular, we study tachyonic scalar fields whose mass is at or above the Breitenlohner-Freedman bound in four, five, and seven spacetime dimensions. The critical amplitude of the leading order perturbation, for which the perturbative expansion breaks down, increases as we consider less massive fields. We present various examples including a model with a self-interacting scalar field which is derived from a consistent truncation of IIB supergravity.
Relative entanglement entropies in 1 + 1-dimensional conformal field theories
NASA Astrophysics Data System (ADS)
Ruggiero, Paola; Calabrese, Pasquale
2017-02-01
We study the relative entanglement entropies of one interval between excited states of a 1+1 dimensional conformal field theory (CFT). To compute the relative entropy S( ρ 1∥ ρ 0) between two given reduced density matrices ρ 1 and ρ 0 of a quantum field theory, we employ the replica trick which relies on the path integral representation of Tr( ρ 1 ρ 0 n - 1 ) and define a set of Rényi relative entropies S n ( ρ 1∥ ρ 0). We compute these quantities for integer values of the parameter n and derive via the replica limit the relative entropy between excited states generated by primary fields of a free massless bosonic field. In particular, we provide the relative entanglement entropy of the state described by the primary operator i∂ ϕ, both with respect to the ground state and to the state generated by chiral vertex operators. These predictions are tested against exact numerical calculations in the XX spin-chain finding perfect agreement.
Conformal Janus on Euclidean sphere
NASA Astrophysics Data System (ADS)
Bak, Dongsu; Gustavsson, Andreas; Rey, Soo-Jong
2016-12-01
We interpret Janus as an interface in a conformal field theory and study its properties. The Janus is created by an exactly marginal operator and we study its effect on the interface conformal field theory on the Janus. We do this by utilizing the AdS/CFT correspondence. We compute the interface free energy both from leading correction to the Euclidean action in the dual gravity description and from conformal perturbation theory in the conformal field theory. We find that the two results agree each other and that the interface free energy scales precisely as expected from the conformal invariance of the Janus interface.
Circular Wilson loops in defect conformal field theory
NASA Astrophysics Data System (ADS)
Aguilera-Damia, Jeremías; Correa, Diego H.; Giraldo-Rivera, Victor I.
2017-03-01
We study a D3-D5 system dual to a conformal field theory with a codimension-one defect that separates regions where the ranks of the gauge groups differ by k. With the help of this additional parameter, as observed by Nagasaki, Tanida and Yamaguchi, one can define a double scaling limit in which the quantum corrections are organized in powers of λ/k 2, which should allow to extrapolate results between weak and strong coupling regimes. In particular we consider a radius R circular Wilson loop placed at a distance L, whose internal space orientation is given by an angle χ. We compute its vacuum expectation value and show that, in the double scaling limit and for small χ and small L/R, weak coupling results can be extrapolated to the strong coupling limit.
The Shimura-Taniyama conjecture and conformal field theory
NASA Astrophysics Data System (ADS)
Schimmrigk, Rolf; Underwood, Sean
2003-11-01
The Shimura-Taniyama conjecture states that the Mellin transform of the Hasse-Weil L-function of any elliptic curve defined over the rational numbers is a modular form. Recent work of Wiles, Taylor-Wiles and Breuil-Conrad-Diamond-Taylor has provided a proof of this longstanding conjecture. Elliptic curves provide the simplest framework for a class of Calabi-Yau manifolds which have been conjectured to be exactly solvable. It is shown that the Hasse-Weil modular form determined by the arithmetic structure of the Fermat type elliptic curve is related in a natural way to a modular form arising from the character of a conformal field theory derived from an affine Kac-Moody algebra.
Entanglement Hamiltonians in two-dimensional conformal field theory
NASA Astrophysics Data System (ADS)
Cardy, John; Tonni, Erik
2016-12-01
We enumerate the cases in 2d conformal field theory where the logarithm of the reduced density matrix (the entanglement or modular Hamiltonian) may be written as an integral over the energy-momentum tensor times a local weight. These include known examples and new ones corresponding to the time-dependent scenarios of a global and local quench. In these latter cases the entanglement Hamiltonian depends on the momentum density as well as the energy density. In all cases the entanglement spectrum is that of the appropriate boundary CFT. We emphasize the role of boundary conditions at the entangling surface and the appearance of boundary entropies as universal O(1) terms in the entanglement entropy.
Energy flux positivity and unitarity in conformal field theories.
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 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.
Synchrotron radiation in strongly coupled conformal field theories
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.
Energy Flux Positivity and Unitarity in Conformal Field Theories
NASA Astrophysics Data System (ADS)
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.
Energy Flux Positivity and Unitarity in Conformal Field Theories
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.
The radial electric field as a measure for field penetration of resonant magnetic perturbations
Mordijck, Saskia; Moyer, Richard A.; Ferraro, Nathaniel M.; ...
2014-06-18
In this study, we introduce a new indirect method for identifying the radial extent of the stochastic layer due to applying resonant magnetic perturbations (RMPs) in H-mode plasmas by measuring the spin-up of the plasma near the separatrix. This spin-up is a predicted consequence of enhanced loss of electrons due to magnetic stochastization. We find that in DIII-D H-mode plasmas with n = 3 RMPs applied for edge localized mode (ELM) suppression, the stochastic layer is limited to the outer 5% region in normalized magnetic flux, ΨN. This is in contrast to vacuum modeling predictions where this layer can penetratemore » up to 20% in ΨN. Theoretical predictions of a stochastic red radial electric field, Er component exceed the experimental measurements by about a factor 3 close to the separatrix, suggesting that the outer region of the plasma is weakly stochastic. Linear response calculations with M3D-C1, a resistive two-fluid model, show that in this outer 5% region, plasma response often reduces the resonant magnetic field components by 67% or more in comparison with vacuum calculations. These results for DIII-D are in reasonable agreement with results from the MAST tokamak, where the magnetic field perturbation from vacuum field calculations needed to be reduced by 75% for agreement with experimental measurements of the x-point lobe structures.« less
The radial electric field as a measure for field penetration of resonant magnetic perturbations
Mordijck, Saskia; Moyer, Richard A.; Ferraro, Nathaniel M.; Wade, Mickey R.; Osborne, Thomas H.
2014-06-18
In this study, we introduce a new indirect method for identifying the radial extent of the stochastic layer due to applying resonant magnetic perturbations (RMPs) in H-mode plasmas by measuring the spin-up of the plasma near the separatrix. This spin-up is a predicted consequence of enhanced loss of electrons due to magnetic stochastization. We find that in DIII-D H-mode plasmas with n = 3 RMPs applied for edge localized mode (ELM) suppression, the stochastic layer is limited to the outer 5% region in normalized magnetic flux, Ψ_{N}. This is in contrast to vacuum modeling predictions where this layer can penetrate up to 20% in Ψ_{N}. Theoretical predictions of a stochastic red radial electric field, E_{r} component exceed the experimental measurements by about a factor 3 close to the separatrix, suggesting that the outer region of the plasma is weakly stochastic. Linear response calculations with M3D-C1, a resistive two-fluid model, show that in this outer 5% region, plasma response often reduces the resonant magnetic field components by 67% or more in comparison with vacuum calculations. These results for DIII-D are in reasonable agreement with results from the MAST tokamak, where the magnetic field perturbation from vacuum field calculations needed to be reduced by 75% for agreement with experimental measurements of the x-point lobe structures.
Apparatus and method for microwave processing of materials using field-perturbing tool
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.
Wang, Shaojie
2016-07-15
Anomalous current pinch, in addition to the anomalous diffusion due to stochastic magnetic perturbations, is theoretically found, which may qualitatively explain the recent DIII-D experiment on resonant magnetic field perturbation. The anomalous current pinch, which may resolve the long-standing issue of seed current in a fully bootstrapped tokamak, is also discussed for the electrostatic turbulence.
Quantum Hall physics: Hierarchies and conformal field theory techniques
NASA Astrophysics Data System (ADS)
Hansson, T. H.; Hermanns, M.; Simon, S. H.; Viefers, S. F.
2017-04-01
The fractional quantum Hall effect, being one of the most studied phenomena in condensed matter physics during the past 30 years, has generated many ground-breaking new ideas and concepts. Very early on it was realized that the zoo of emerging states of matter would need to be understood in a systematic manner. The first attempts to do this, by Haldane and Halperin, set an agenda for further work which has continued to this day. Since that time the idea of hierarchies of quasiparticles condensing to form new states has been a pillar of our understanding of fractional quantum Hall physics. In the 30 years that have passed since then, a number of new directions of thought have advanced our understanding of fractional quantum Hall states and have extended it in new and unexpected ways. Among these directions is the extensive use of topological quantum field theories and conformal field theories, the application of the ideas of composite bosons and fermions, and the study of non-Abelian quantum Hall liquids. This article aims to present a comprehensive overview of this field, including the most recent developments.
Quantum corrections to the cosmological evolution of conformally coupled fields
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.
𝜖-expansion in critical ϕ3-theory on real projective space from conformal field theory
NASA Astrophysics Data System (ADS)
Hasegawa, Chika; Nakayama, Yu
2017-03-01
We use a compatibility between the conformal symmetry and the equations of motion to solve the one-point function in the critical ϕ3-theory (a.k.a. the critical Lee-Yang model) on the d = 6 ‑ 𝜖 dimensional real projective space to the first nontrivial order in the 𝜖-expansion. It reproduces the conventional perturbation theory and agrees with the numerical conformal bootstrap result.
Tsuji, Motonori
2017-06-01
HX531, which contains a dibenzodiazepine skeleton, is one of the first retinoid X receptor (RXR) antagonists. Functioning via RXR-PPARγ heterodimer, this compound is receiving a lot of attention as a therapeutic drug candidate for diabetic disease controlling differentiation of adipose tissue. However, the active conformation of HX531 for RXRs is not well established. In the present study, quantum mechanics calculations and molecular mechanical docking simulations were carried out to precisely study the docking mode of HX531 with the human RXRα ligand-binding domain, as well as to provide a new approach to drug design using a structure-based perspective. It was suggested that HX531, which has the R configuration for the bent dibenzodiazepine plane together with the equatorial configuration for the N-methyl group attached to the nitrogen atom in the seven-membered diazepine ring, is a typical activation function-2 (AF-2) fixed motif perturbation type antagonist, which destabilizes the formation of AF-2 fixed motifs. On the other hand, the docking simulations supported the experimental result that LG100754 is an RXR homodimer antagonist and an RXR heterodimer agonist.
NASA Astrophysics Data System (ADS)
Tsuji, Motonori
2017-06-01
HX531, which contains a dibenzodiazepine skeleton, is one of the first retinoid X receptor (RXR) antagonists. Functioning via RXR-PPARγ heterodimer, this compound is receiving a lot of attention as a therapeutic drug candidate for diabetic disease controlling differentiation of adipose tissue. However, the active conformation of HX531 for RXRs is not well established. In the present study, quantum mechanics calculations and molecular mechanical docking simulations were carried out to precisely study the docking mode of HX531 with the human RXRα ligand-binding domain, as well as to provide a new approach to drug design using a structure-based perspective. It was suggested that HX531, which has the R configuration for the bent dibenzodiazepine plane together with the equatorial configuration for the N-methyl group attached to the nitrogen atom in the seven-membered diazepine ring, is a typical activation function-2 (AF-2) fixed motif perturbation type antagonist, which destabilizes the formation of AF-2 fixed motifs. On the other hand, the docking simulations supported the experimental result that LG100754 is an RXR homodimer antagonist and an RXR heterodimer agonist.
A Mechanism of ELM Mitigation by External Magnetic Field Perturbations
NASA Astrophysics Data System (ADS)
Singh, Raghvendra; Jhang, H.; Kim, J.-H.; Hahm, T. S.
2016-10-01
We study the impact of external magnetic perturbations (EMP) on the stability of ballooning mode (BM). We use: 1) the two-step process; 2) standard four wave interactions. In two-step process, we consider EMP are long wave-length perturbations interacting with short scale BM and generating side-bands of higher harmonics. This calculates contributions from all the high toroidal mode numbers. EMP can modify the dispersion characteristics of BM - the growth spectrum becomes broader in kBM space. The increase in high kBM can lead to the mitigation of an ELM crash by increasing turbulent transport. New nonlinear instability is also found even below the BM threshold at large EMP amplitude. In four wave interaction, EMP act like a short scale pump wave interacting with BM and creating two sidebands. The side-bands couple with the pump and produce the ponderomotive force, magnetic stress at BM frequency. EMP may enhance the BM instability threshold if RMP K->BM <=K->RMP and reduce the threshold if K->BM >K->RMP .
Conformation change of enzyme molecules in laser radiation field
NASA Astrophysics Data System (ADS)
Leshenyuk, N. S.; Prigun, M. V.; Apanasevitsh, E. E.; Kruglik, G. S.
2007-06-01
As a result of an analysis of macromolecules properties in the coherent optical radiation field and with allowance for the experimentally obtained unique data on the interaction of lazer radiation with biomolecules (dependence of the interaction efficiency on the coherence length, presence of the effect in the spectra region far from the absorption band), a mechanism of wave interaction is developed. Using this mathematical model, the calculations of a change in the macromolecules oscillatory energy in the coherent radiation field are performed. It is shown that the increase of macromolecules oscillatory energy depends strongly on the coherence length of radiation. On exposure to noncoherent radiation, the biomolecules oscillatory energy practically does not change, whereas on exposure to laser radiation (coherence length ~3 cm), energy of oscillations of atoms increases by an order of 2÷4, which results in a change in the conformation of biomolecules and activity of enzymes. Recently a lot of data are received concerning the change of lysosomal enzymes activity in blood plasma under action of laser radiation.
Scale anomalies, states, and rates in conformal field theory
NASA Astrophysics Data System (ADS)
Gillioz, Marc; Lu, Xiaochuan; Luty, Markus A.
2017-04-01
This paper presents two methods to compute scale anomaly coefficients in conformal field theories (CFTs), such as the c anomaly in four dimensions, in terms of the CFT data. We first use Euclidean position space to show that the anomaly coefficient of a four-point function can be computed in the form of an operator product expansion (OPE), namely a weighted sum of OPE coefficients squared. We compute the weights for scale anomalies associated with scalar operators and show that they are not positive. We then derive a different sum rule of the same form in Minkowski momentum space where the weights are positive. The positivity arises because the scale anomaly is the coefficient of a logarithm in the momentum space four-point function. This logarithm also determines the dispersive part, which is a positive sum over states by the optical theorem. The momentum space sum rule may be invalidated by UV and/or IR divergences, and we discuss the conditions under which these singularities are absent. We present a detailed discussion of the formalism required to compute the weights directly in Minkowski momentum space. A number of explicit checks are performed, including a complete example in an 8-dimensional free field theory.
Quantum revivals in conformal field theories in higher dimensions
NASA Astrophysics Data System (ADS)
Cardy, John
2016-10-01
We investigate the behavior of the return amplitude { F }(t)=| < {{\\Psi }}(0)| {{\\Psi }}(t)> | following a quantum quench in a conformal field theory (CFT) on a compact spatial manifold of dimension d-1 and linear size O(L), from a state | {{\\Psi }}(0)> of extensive energy with short-range correlations. After an initial gaussian decay { F }(t) reaches a plateau value related to the density of available states at the initial energy. However for d=3,4 this value is attained from below after a single oscillation. For a holographic CFT the plateau persists up to times at least O({σ }1/(d-1)L), where σ \\gg 1 is the dimensionless Stefan-Boltzmann constant. On the other hand for a free field theory on manifolds with high symmetry there are typically revivals at times t˜ {{integer}}× L. In particular, on a sphere {S}d-1 of circumference 2π L, there is an action of the modular group on { F }(t) implying structure near all rational values of t/L, similar to what happens for rational CFTs in d=2.
Gauge-invariant perturbations at second order: multiple scalar fields on large scales
NASA Astrophysics Data System (ADS)
Malik, Karim A.
2005-11-01
We derive the governing equations for multiple scalar fields minimally coupled to gravity in a flat Friedmann Robertson Walker background spacetime on large scales. We include scalar perturbations up to second order and write the equations in terms of physically transparent gauge-invariant variables at first and second order. This allows us to write the perturbed Klein Gordon equation at second order solely in terms of the field fluctuations on flat slices at first and second order.
Nonlinear Interaction of a Shock Wave with an Anisotropic Entropy Perturbation Field
NASA Astrophysics Data System (ADS)
Gorodnichev, K. E.; Kuratov, S. E.; Gorodnichev, E. E.
2017-01-01
The problem of the interaction of a shock wave with an anisotropic entropy perturbation field has been solved including second-order corrections to hydrodynamic quantities. It has been shown that nonlinear interactions between acoustic waves result in the localization of acoustic perturbations behind the shock front. This effect is observed when sound attenuation is absent in the linear approximation. The problem of the propagation of the shock wave in an incident sample, where the spatially anisotropic density perturbation field initially exists, has been numerically solved in application to the collision of two plates. Numerical calculations confirm the results of the theoretical analysis.
Perturbative unitarity of Lee-Wick quantum field theory
NASA Astrophysics Data System (ADS)
Anselmi, Damiano; Piva, Marco
2017-08-01
We study the perturbative unitarity of the Lee-Wick models, formulated as nonanalytically Wick rotated Euclidean theories. The complex energy plane is divided into disconnected regions and the values of a loop integral in the various regions are related to one another by a nonanalytic procedure. We show that the one-loop diagrams satisfy the expected, unitary cutting equations in each region: only the physical d.o.f. propagate through the cuts. The goal can be achieved by working in suitable subsets of each region and proving that the cutting equations can be analytically continued as a whole. We make explicit calculations in the cases of the bubble and triangle diagrams and address the generality of our approach. We also show that the same higher-derivative models violate unitarity if they are formulated directly in Minkowski spacetime.
Partition function of free conformal fields in 3-plet representation
NASA Astrophysics Data System (ADS)
Beccaria, Matteo; Tseytlin, Arkady A.
2017-05-01
Simplest examples of AdS/CFT duality correspond to free CFTs in d dimensions with fields in vector or adjoint representation of an internal symmetry group dual in the large N limit to a theory of massless or massless plus massive higher spins in AdS d+1. One may also study generalizations when conformal fields belong to higher dimensional representations, i.e. carry more than two internal symmetry indices. Here we consider the case of the 3-fundamental ("3-plet") representation. One motivation is a conjectured connection to multiple M5-brane theory: heuristic arguments suggest that it may be related to an (interacting) CFT of 6d (2,0) tensor multiplets in 3-plet representation of large N symmetry group that has an AdS7 dual. We compute the singlet partition function Z on S 1 × S d-1 for a free field in 3-plet representation of U( N) and analyse its novel large N behaviour. The large N limit of the low temperature expansion of Z which is convergent in the vector and adjoint cases here is only asymptotic, reflecting the much faster growth of the number of singlet operators with dimension, indicating a phase transition at very low temperature. Indeed, while the critical temperatures in the vector ( T c ˜ N γ , γ > 0) and adjoint ( T c ˜ 1) cases are finite, we find that in the 3-plet case T c ˜ (log N)-1, i.e. it approaches zero at large N. We discuss some details of large N solution for the eigenvalue distribution. Similar conclusions apply to higher p-plet representations of U( N) or O( N) and also to the free p-tensor theories invariant under [U( N)] p or [ O( N)] p with p ≥ 3.
Twisting perturbed parafermions
NASA Astrophysics Data System (ADS)
Belitsky, A. V.
2017-07-01
The near-collinear expansion of scattering amplitudes in maximally supersymmetric Yang-Mills theory at strong coupling is governed by the dynamics of stings propagating on the five sphere. The pentagon transitions in the operator product expansion which systematize the series get reformulated in terms of matrix elements of branch-point twist operators in the two-dimensional O(6) nonlinear sigma model. The facts that the latter is an asymptotically free field theory and that there exists no local realization of twist fields prevents one from explicit calculation of their scaling dimensions and operator product expansion coefficients. This complication is bypassed making use of the equivalence of the sigma model to the infinite-level limit of WZNW models perturbed by current-current interactions, such that one can use conformal symmetry and conformal perturbation theory for systematic calculations. Presently, to set up the formalism, we consider the O(3) sigma model which is reformulated as perturbed parafermions.
Perturbative quantum field theory in the framework of the fermionic projector
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.
Loops in AdS from conformal field theory
NASA Astrophysics Data System (ADS)
Aharony, Ofer; Alday, Luis F.; Bissi, Agnese; Perlmutter, Eric
2017-07-01
We propose and demonstrate a new use for conformal field theory (CFT) crossing equations in the context of AdS/CFT: the computation of loop amplitudes in AdS, dual to non-planar correlators in holographic CFTs. Loops in AdS are largely unexplored, mostly due to technical difficulties in direct calculations. We revisit this problem, and the dual 1 /N expansion of CFTs, in two independent ways. The first is to show how to explicitly solve the crossing equations to the first subleading order in 1 /N 2, given a leading order solution. This is done as a systematic expansion in inverse powers of the spin, to all orders. These expansions can be resummed, leading to the CFT data for finite values of the spin. Our second approach involves Mellin space. We show how the polar part of the four-point, loop-level Mellin amplitudes can be fully reconstructed from the leading-order data. The anomalous dimensions computed with both methods agree. In the case of ϕ 4 theory in AdS, our crossing solution reproduces a previous computation of the one-loop bubble diagram. We can go further, deriving the four-point scalar triangle diagram in AdS, which had never been computed. In the process, we show how to analytically derive anomalous dimensions from Mellin amplitudes with an infinite series of poles, and discuss applications to more complicated cases such as the N = 4 super-Yang-Mills theory.
Test of the Anti-de Sitter-Space/Conformal-Field-Theory Correspondence Using High-Spin Operators
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.
Non-perturbative methods in relativistic field theory
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.
Linear-scaling density matrix perturbation treatment of electric fields in solids.
Xiang, H J; Yang, Jinlong; Hou, J G; Zhu, Qingshi
2006-12-31
We develop a novel linear-scaling [O(N)] algorithm for calculating the optical dielectric constant and Born effective charge. Our method relies on the fact that only the sum of the nondiagonal parts of the electric field perturbation in solids contributes to the first-order derivative density matrix, which can then be obtained through the density-matrix perturbation method. The optical dielectric constant of amorphous SiO(2) is computed using a realistic model for the first time.
Effective field theory program for conformal quantum anomalies
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.
Noncommutative Geometry in M-Theory and Conformal Field Theory
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_{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_{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.
Indecomposability parameters in chiral logarithmic conformal field theory
NASA Astrophysics Data System (ADS)
Vasseur, Romain; Jacobsen, Jesper Lykke; Saleur, Hubert
2011-10-01
Work of the last few years has shown that the key algebraic features of Logarithmic Conformal Field Theories (LCFTs) are already present in some finite lattice systems (such as the XXZ spin-1/2 chain) before the continuum limit is taken. This has provided a very convenient way to analyze the structure of indecomposable Virasoro modules and to obtain fusion rules for a variety of models such as (boundary) percolation etc. LCFTs allow for additional quantum numbers describing the fine structure of the indecomposable modules, and generalizing the ' b-number' introduced initially by Gurarie for the c=0 case. The determination of these indecomposability parameters (or logarithmic couplings) has given rise to a lot of algebraic work, but their physical meaning has remained somewhat elusive. In a recent paper, a way to measure b for boundary percolation and polymers was proposed. We generalize this work here by devising a general strategy to compute matrix elements of Virasoro generators from the numerical analysis of lattice models and their continuum limit. The method is applied to XXZ spin-1/2 and spin-1 chains with open (free) boundary conditions. They are related to gl(n+m|m) and osp(n+2m|2m)-invariant superspin chains and to non-linear sigma models with supercoset target spaces. These models can also be formulated in terms of dense and dilute loop gas. We check the method in many cases where the results were already known analytically. Furthermore, we also confront our findings with a construction generalizing Gurarie's, where logarithms emerge naturally in operator product expansions to compensate for apparently divergent terms. This argument actually allows us to compute indecomposability parameters in any logarithmic theory. A central result of our study is the construction of a Kac table for the indecomposability parameters of the logarithmic minimal models LM(1,p) and LM(p,p+1).
Hamiltonian identification in presence of large control field perturbations
NASA Astrophysics Data System (ADS)
Fu, Ying; Rabitz, Herschel; Turinici, Gabriel
2016-12-01
Quantum system inversion concerns learning the characteristics of the underlying Hamiltonian by measuring suitable observables from the responses of the system’s interaction with members of a set of applied fields. Various aspects of inversion have been confirmed in theoretical, numerical and experimental works. Nevertheless, the presence of noise arising from the applied fields may contaminate the quality of the results. In this circumstance, the observables satisfy probability distributions, but often the noise statistics are unknown. Based on a proposed theoretical framework, we present a procedure to recover both the unknown parts of the Hamiltonian and the unknown noise distribution. The procedure is implemented numerically and seen to perform well for illustrative Gaussian, exponential and bi-modal noise distributions.
Holomorphic normal form of nonlinear perturbations of nilpotent vector fields
NASA Astrophysics Data System (ADS)
Stolovitch, Laurent; Verstringe, Freek
2016-07-01
We consider germs of holomorphic vector fields at a fixed point having a nilpotent linear part at that point, in dimension n ≥ 3. Based on Belitskii's work, we know that such a vector field is formally conjugate to a (formal) normal form. We give a condition on that normal form which ensures that the normalizing transformation is holomorphic at the fixed point.We shall show that this sufficient condition is a nilpotent version of Bruno's condition (A). In dimension 2, no condition is required since, according to Stróżyna-Żołladek, each such germ is holomorphically conjugate to a Takens normal form. Our proof is based on Newton's method and sl2(C)-representations.
NASA Astrophysics Data System (ADS)
Chung, Stephen-Wei
We first construct new parafermions in two-dimensional conformal field theory, generalizing the Z_ {L} parafermion theories from integer L to rational L. These non-unitary parafermions have some novel features: an infinite number of currents with negative conformal dimensions for most (if not all) of them. String functions of these new parafermion theories are calculated. We also construct new representations of N = 2 superconformal field theories, whose characters are obtained in terms of these new string functions. We then generalize Felder's BRST cohomology method to construct the characters and branching functions of the SU(2)_{L} times SU(2)_{K}/SU(2)_{K+L } coset theories, where one of the (K, L) is an integer. This method of obtaining the branching functions also serves as a check of our new Z_{L } parafermion theories. The next topic is the Lagrangian formulation of conformal field theory. We construct a chiral gauged WZW theory where the gauge fields are chiral and belong to the subgroups H_{L} and H_{R}, which can be different groups. This new construction is beyond the ordinary vector gauged WZW theory, whose gauge group H is a subgroup of both G_{L} and G _{R}. In the special case where H_{L} = H_{R}, the quantum theory of chiral gauged WZW theory is equivalent to that of the vector gauged WZW theory. It can be further shown that the chiral gauged WZW theory is equivalent to [ G_{L }/H_{L}] (z)otimes [ G_{R}/H_{R} ] (|{z}) coset models in conformal field theory. In the second half of this thesis, we construct topological lattice field theories in three dimensions. After defining a general class of local lattice field theories, we impose invariance under arbitrary topology-preserving deformations of the underlying lattice, which are generated by two local lattice moves. Invariant solutions are in one-to-one correspondence with Hopf algebras satisfying a certain constraint. As an example, we study in detail the topological lattice field theory
Local and Average Structures in Ferroelectrics under Perturbing Fields
NASA Astrophysics Data System (ADS)
Usher, Tedi-Marie
Ferroelectric and dielectric ceramics are used in a multitude of applications including sonar, micro-positioning, actuators, transducers, and capacitors. The most widely used compositions are lead (Pb)-based, however there is an ongoing effort to reduce lead-based materials in consumer applications. Many lead-free compositions are under investigation; some are already in production and others have been identified as suitable for certain applications. For any such material system, there is a need to thoroughly characterize the structure in order to develop robust structure-property relationships, particularly during in situ application of different stimuli (e.g. electric field and mechanical stress). This work investigates two lead-free material systems of interest, (1-x)Na1/2Bi1/2TiO3 - (x)BaTiO3 (NBT-xBT) and (1-x)BaTiO3 - (x)Bi(Zn1/2Ti1/2)O3 (BT-xBZT), as well as the constituent compounds Na1/2Bi1/2TiO3 and BaTiO3. Both systems exhibit compositional boundaries between unique phases exhibiting different functional properties. Advanced scattering techniques are used to characterize the atomic structures and how they change during in situ application of different stimuli. The long-range, average structures are probed using high-resolution X-ray diffraction (HRXRD) and neutron diffraction (ND) and local scale structures are probed using X-ray or neutron total scattering, which are converted to pair distribution functions (PDFs). First, two in situ ND experiments which investigate structural changes to NBT-xBT in response to uniaxial stresses and electric fields are presented. In response to stresses, different crystallographic directions strain differently. The elastic anisotropy, (i.e., the orientation-dependence of elastic stiffness) for the studied compositions is characterized. A general inverse relationship between elastic anisotropy and piezoelectric anisotropy is demonstrated for three common ferroelectric point groups. In response to electric fields
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.
Gravitational waves and scalar perturbations from spectator fields
Biagetti, Matteo; Dimastrogiovanni, Emanuela; Peloso, Marco; Fasiello, Matteo E-mail: emanuela1573@gmail.com E-mail: peloso@physics.umn.edu
2015-04-01
The most conventional mechanism for gravitational waves (gw) production during inflation is the amplification of vacuum metric fluctuations. In this case the gw production can be uniquely related to the inflationary expansion rate H. For example, a gw detection close to the present experimental limit (tensor-to-scalar ratio r ∼ 0.1) would indicate an inflationary expansion rate close to 10{sup 14} GeV. This conclusion, however, would be invalid if the observed gw originated from a different source. We construct and study one of the possible covariant formulations of the mechanism suggested in [1], where a spectator field σ with a sound speed c{sub s} || 1 acts as a source for gw during inflation. In our formulation σ is described by a so-called P(X) Lagrangian and a non-minimal coupling to gravity. This field interacts only gravitationally with the inflaton, which has a standard action. We compute the amount of scalar and tensor density fluctuations produced by σ and find that, in our realization, r is not enhanced with respect to the standard result but it is strongly sensitive to c{sub s}, thus breaking the direct r ↔ H connection.
Gravitational waves and scalar perturbations from spectator fields
NASA Astrophysics Data System (ADS)
Biagetti, Matteo; Dimastrogiovanni, Emanuela; Fasiello, Matteo; Peloso, Marco
2015-04-01
The most conventional mechanism for gravitational waves (gw) production during inflation is the amplification of vacuum metric fluctuations. In this case the gw production can be uniquely related to the inflationary expansion rate H. For example, a gw detection close to the present experimental limit (tensor-to-scalar ratio r ~ 0.1) would indicate an inflationary expansion rate close to 1014 GeV. This conclusion, however, would be invalid if the observed gw originated from a different source. We construct and study one of the possible covariant formulations of the mechanism suggested in [1], where a spectator field σ with a sound speed cs ll 1 acts as a source for gw during inflation. In our formulation σ is described by a so-called P(X) Lagrangian and a non-minimal coupling to gravity. This field interacts only gravitationally with the inflaton, which has a standard action. We compute the amount of scalar and tensor density fluctuations produced by σ and find that, in our realization, r is not enhanced with respect to the standard result but it is strongly sensitive to cs, thus breaking the direct r leftrightarrow H connection.
NASA Astrophysics Data System (ADS)
Kapranov, Sergey V.; Kouzaev, Guennadi A.
2013-06-01
The motion of a dipole in external electric fields is considered in the framework of nonlinear pendulum dynamics. A stochastic layer is formed near the separatrix of the dipole pendulum in a restoring static electric field under the periodic perturbation by plane-polarized electric fields. The width of the stochastic layer depends on the direction of the forcing field variation, and this width can be evaluated as a function of perturbation frequency, amplitude, and duration. A numerical simulation of the approximate stochastic layer width of a perturbed pendulum yields a multi-peak frequency spectrum. It is described well enough at high perturbation amplitudes by an analytical estimation based on the separatrix map with an introduced expression of the most effective perturbation phase. The difference in the fractal dimensions of the phase spaces calculated geometrically and using the time-delay reconstruction is attributed to the predominant development of periodic and chaotic orbits, respectively. The correlation of the stochastic layer width with the phase space fractal dimensions is discussed.
Correspondence between Asymptotically Flat Spacetimes and Nonrelativistic Conformal Field Theories
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.
Perturbations of slowly rotating black holes: Massive vector fields in the Kerr metric
NASA Astrophysics Data System (ADS)
Pani, Paolo; Cardoso, Vitor; Gualtieri, Leonardo; Berti, Emanuele; Ishibashi, Akihiro
2012-11-01
We discuss a general method to study linear perturbations of slowly rotating black holes which is valid for any perturbation field, and particularly advantageous when the field equations are not separable. As an illustration of the method we investigate massive vector (Proca) perturbations in the Kerr metric, which do not appear to be separable in the standard Teukolsky formalism. Working in a perturbative scheme, we discuss two important effects induced by rotation: a Zeeman-like shift of nonaxisymmetric quasinormal modes and bound states with different azimuthal number m, and the coupling between axial and polar modes with different multipolar index ℓ. We explicitly compute the perturbation equations up to second order in rotation, but in principle the method can be extended to any order. Working at first order in rotation we show that polar and axial Proca modes can be computed by solving two decoupled sets of equations, and we derive a single master equation describing axial perturbations of spin s=0 and s=±1. By extending the calculation to second order we can study the superradiant regime of Proca perturbations in a self-consistent way. For the first time we show that Proca fields around Kerr black holes exhibit a superradiant instability, which is significantly stronger than for massive scalar fields. Because of this instability, astrophysical observations of spinning black holes provide the tightest upper limit on the mass of the photon: mγ≲4×10-20eV under our most conservative assumptions. Spin measurements for the largest black holes could reduce this bound to mγ≲10-22eV or lower.
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.
Dynamics of Peccei-Quinn breaking field after inflation and axion isocurvature perturbations
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.
Dynamics of Peccei-Quinn breaking field after inflation and axion isocurvature perturbations
NASA Astrophysics Data System (ADS)
Harigaya, Keisuke; Ibe, Masahiro; Kawasaki, Masahiro; Yanagida, Tsutomu T.
2015-11-01
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.
Evolution of perturbations in distinct classes of canonical scalar field models of dark energy
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.
Thermalization and revivals after a quantum quench in conformal field theory.
Cardy, John
2014-06-06
We consider a quantum quench in a finite system of length L described by a 1+1-dimensional conformal field theory (CFT), of central charge c, from a state with finite energy density corresponding to an inverse temperature β≪L. For times t such that ℓ/2
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.
Non-Gaussianity at tree and one-loop levels from vector field perturbations
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.
Membrane potential perturbations induced in tissue cells by pulsed electric fields
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.
Virasoro conformal blocks and thermality from classical background fields
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
Virasoro conformal blocks and thermality from classical background fields
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 AdS_{3} , or equivalently, the eigenstate thermalization hypothesis for CFT_{2} at large central charge.
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.
NASA Astrophysics Data System (ADS)
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.
Sample-Induced RF Perturbations in High-Field, High-Resolution NMR Spectroscopy
NASA Astrophysics Data System (ADS)
Crozier, Stuart; Brereton, Ian M.; Zelaya, Fernando O.; Roffmann, Wolfgang U.; Doddrell, David M.
1997-05-01
Conducting dielectric samples are often used in high-resolution experiments at high field. It is shown that significant amplitude and phase distortions of the RF magnetic field may result from perturbations caused by such samples. Theoretical analyses demonstrate the spatial variation of the RF field amplitude and phase across the sample, and comparisons of the effect are made for a variety of sample properties and operating field strengths. Although the effect is highly nonlinear, it tends to increase with increasing field strength, permittivity, conductivity, and sample size. There are cases, however, in which increasing the conductivity of the sample improves the homogeneity of the amplitude of the RF field across the sample at the expense of distorted RF phase. It is important that the perturbation effects be calculated for the experimental conditions used, as they have the potential to reduce the signal-to-noise ratio of NMR experiments and may increase the generation of spurious coherences. The effect of RF-coil geometry on the coherences is also modeled, with the use of homogeneous resonators such as the birdcage design being preferred. Recommendations are made concerning methods of reducing sample-induced perturbations. Experimental high-field imaging and high-resolution studies demonstrate the effect.
Quasi-Exactly Quantal Problems:. One-Dimensional Analogue of Rational Conformal Field Theories
NASA Astrophysics Data System (ADS)
Morozov, A. Yu.; Perelomov, A. M.; Rosly, A. A.; Shifman, M. A.; Turbiner, A. V.
The class of quasi-exactly-solvable problems in ordinary quantum mechanics discovered recently shows remarkable parallels with rational two-dimensional conformal field theories. This fact suggests that investigation of the quasi-exactly-solvable models may shed light on rational conformal field theories. We discuss a relation between these two theoretical schemes and propose a mathematical formulation for the procedure of constructing quasi-exactly solvable systems. This discussion leads us to a kind of generalization of the Sugawara construction.
Conformal field theory as microscopic dynamics of incompressible Euler and Navier-Stokes equations.
Fouxon, Itzhak; Oz, Yaron
2008-12-31
We consider the hydrodynamics of relativistic conformal field theories at finite temperature. We show that the limit of slow motions of the ideal hydrodynamics leads to the nonrelativistic incompressible Euler equation. For viscous hydrodynamics we show that the limit of slow motions leads to the nonrelativistic incompressible Navier-Stokes equation. We explain the physical reasons for the reduction and discuss the implications. We propose that conformal field theories provide a fundamental microscopic viewpoint of the equations and the dynamics governed by them.
Conformal Field Theory as Microscopic Dynamics of Incompressible Euler and Navier-Stokes Equations
Fouxon, Itzhak; Oz, Yaron
2008-12-31
We consider the hydrodynamics of relativistic conformal field theories at finite temperature. We show that the limit of slow motions of the ideal hydrodynamics leads to the nonrelativistic incompressible Euler equation. For viscous hydrodynamics we show that the limit of slow motions leads to the nonrelativistic incompressible Navier-Stokes equation. We explain the physical reasons for the reduction and discuss the implications. We propose that conformal field theories provide a fundamental microscopic viewpoint of the equations and the dynamics governed by them.
Logarithmic conformal field theory, log-modular tensor categories and modular forms
NASA Astrophysics Data System (ADS)
Creutzig, Thomas; Gannon, Terry
2017-10-01
The two pillars of rational conformal field theory and rational vertex operator algebras are modularity of characters, and the interpretation of its category of modules as a modular tensor category. Overarching these pillars is the Verlinde formula. In this paper we consider the more general class of logarithmic conformal field theories and C 2-cofinite vertex operator algebras. We suggest logarithmic variants of those pillars and of Verlinde’s formula. We illustrate our ideas with the \
NASA Astrophysics Data System (ADS)
Auerbach, Jerome M.; L, L.; Eimerl, David; Milam, David; Milonni, Peter W.
1997-01-01
A theory is presented for the transfer of a perturbation of the electric field from the input to the output of a frequency converter. The transfer relationship for the field ripple is shown to depend on the plane-wave operating parameters of the converter. Predictions of the theory are shown to be in excellent agreement with full numerical simulations of doubling and tripling and experiments measuring ripple transfer in frequency doubling.
EFFECTS OF LARGE-SCALE NON-AXISYMMETRIC PERTURBATIONS IN THE MEAN-FIELD SOLAR DYNAMO
Pipin, V. V.; Kosovichev, A. G.
2015-11-10
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{sub ⊙} 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 R{sub m}. In the range of R{sub m} = 10{sup 4}–10{sup 6} 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.
Murguia, Gabriela; Moreno, Matias; Torres, Manuel
2009-04-20
A well known example in quantum electrodynamics (QED) shows that Coulomb scattering of unpolarized electrons, calculated to lowest order in perturbation theory, yields a results that exactly coincides (in the non-relativistic limit) with the Rutherford formula. We examine an analogous example, the classical and perturbative quantum scattering of an electron by a magnetic field confined in an infinite solenoid of finite radius. The results obtained for the classical and the quantum differential cross sections display marked differences. While this may not be a complete surprise, one should expect to recover the classical expression by applying the classical limit to the quantum result. This turn not to be the case. Surprisingly enough, it is shown that the classical result can not be recuperated even if higher order corrections are included. To recover the classic correspondence of the quantum scattering problem a suitable non-perturbative methodology should be applied.
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.
ON MULTIPLE RECONNECTION X-LINES AND TRIPOLAR PERTURBATIONS OF STRONG GUIDE MAGNETIC FIELDS
Eriksson, S.; Gosling, J. T.; Lapenta, G.; Newman, D. L.; Goldman, M. V.; Phan, T. D.; Lavraud, B.; Khotyaintsev, Yu. V.; Carr, C. M.; Markidis, S.
2015-05-20
We report new multi-spacecraft Cluster observations of tripolar guide magnetic field perturbations at a solar wind reconnection exhaust in the presence of a guide field B{sub M} {sub }which is almost four times as strong as the reversing field B{sub L}. The novel tripolar field consists of two narrow regions of depressed B{sub M}, with an observed 7%–14% ΔB{sub M} magnitude relative to the external field, which are found adjacent to a wide region of enhanced B{sub M} within the exhaust. A stronger reversing field is associated with each B{sub M} depression. A kinetic reconnection simulation for realistic solar wind conditions and the observed strong guide field reveals that tripolar magnetic fields preferentially form across current sheets in the presence of multiple X-lines as magnetic islands approach one another and merge into fewer and larger islands. The simulated ΔB{sub M}/ΔX{sub N} over the normal width ΔX{sub N} between a B{sub M} minimum and the edge of the external region agree with the normalized values observed by Cluster. We propose that a tripolar guide field perturbation may be used to identify candidate regions containing multiple X-lines and interacting magnetic islands at individual solar wind current sheets with a strong guide field.
Curvature perturbation spectrum in two-field inflation with a turning trajectory
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.
Retention of nativelike conformation by proteins embedded in high external electric fields
NASA Astrophysics Data System (ADS)
Pompa, P. P.; Bramanti, A.; Maruccio, G.; Cingolani, R.; De Rienzo, F.; Corni, S.; Di Felice, R.; Rinaldi, R.
2005-05-01
In this Communication, we show that proteins embedded in high external electric fields are capable of retaining a nativelike fold pattern. We have tested the metalloprotein azurin, immobilized onto SiO2 substrates in air with proper electrode configuration, by applying static fields up to 106-107V/m. The effects on the conformational properties of protein molecules have been determined by means of intrinsic fluorescence measurements. Experimental results indicate that no significant field-induced conformational alteration occurs. Such results are also discussed and supported by theoretical predictions of the inner protein fields.
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.
On the reach of perturbative methods for dark matter density fields
Baldauf, Tobias; Zaldarriaga, Matias; Schaan, Emmanuel E-mail: eschaan@astro.princeton.edu
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{sup −1} (k = 0.46 hMpc{sup −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 k{sup 4} as it does in the very low k regime. Thus, modeling this contribution might be challenging.
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.
Conformal universe as false vacuum decay
NASA Astrophysics Data System (ADS)
Libanov, M.; Rubakov, V.
2015-05-01
We point out that the (pseudo)conformal universe scenario may be realized as the decay of a conformally invariant, metastable vacuum, which proceeds via spontaneous nucleation and subsequent growth of a bubble of a putative new phase. We study perturbations about the bubble and show that their leading late-time properties coincide with those inherent in the original models with homogeneously rolling backgrounds. In particular, the perturbations of a spectator dimension-zero field have a flat power spectrum.
Thermal corrections to Rényi entropies for conformal field theories
NASA Astrophysics Data System (ADS)
Herzog, Christopher P.; Nian, Jun
2015-06-01
We compute thermal corrections to Rényi entropies of d dimensional conformal field theories on spheres. Consider the nth Rényi entropy for a cap of opening angle 2 θ on S d-1. From a Boltzmann sum decomposition and the operator-state correspondence, the leading correction is related to a certain two-point correlation function of the operator (not equal to the identity) with smallest scaling dimension. More specifically, via a conformal map, the correction can be expressed in terms of the two-point function on a certain conical space with opening angle 2 πn. In the case of free conformal field theories, this two-point function can be computed explicitly using the method of images. We perform the computation for the conformally coupled scalar. From the n → 1 limit of our results, we extract the leading thermal correction to the entanglement entropy, reproducing results of arXiv:1407.1358.
Chiral scale and conformal invariance in 2D quantum field theory.
Hofman, Diego M; Strominger, Andrew
2011-10-14
It is well known that a local, unitary Poincaré-invariant 2D quantum field theory with a global scaling symmetry and a discrete non-negative spectrum of scaling dimensions necessarily has both a left and a right local conformal symmetry. In this Letter, we consider a chiral situation beginning with only a left global scaling symmetry and do not assume Lorentz invariance. We find that a left conformal symmetry is still implied, while right translations are enhanced either to a right conformal symmetry or a left U(1) Kac-Moody symmetry.
Chiral Scale and Conformal Invariance in 2D Quantum Field Theory
NASA Astrophysics Data System (ADS)
Hofman, Diego M.; Strominger, Andrew
2011-10-01
It is well known that a local, unitary Poincaré-invariant 2D quantum field theory with a global scaling symmetry and a discrete non-negative spectrum of scaling dimensions necessarily has both a left and a right local conformal symmetry. In this Letter, we consider a chiral situation beginning with only a left global scaling symmetry and do not assume Lorentz invariance. We find that a left conformal symmetry is still implied, while right translations are enhanced either to a right conformal symmetry or a left U(1) Kac-Moody symmetry.
Anti-de Sitter-space/conformal-field-theory Casimir energy for rotating black holes.
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.
On the Stability of KMS States in Perturbative Algebraic Quantum Field Theories
NASA Astrophysics Data System (ADS)
Drago, Nicolò; Faldino, Federico; Pinamonti, Nicola
2017-08-01
We analyze the stability properties shown by KMS states for interacting massive scalar fields propagating over Minkowski spacetime, recently constructed in the framework of perturbative algebraic quantum field theories by Fredenhagen and Lindner (Commun Math Phys 332:895, 2014). In particular, we prove the validity of the return to equilibrium property when the interaction Lagrangian has compact spatial support. Surprisingly, this does not hold anymore, if the adiabatic limit is considered, namely when the interaction Lagrangian is invariant under spatial translations. Consequently, an equilibrium state under the adiabatic limit for a perturbative interacting theory evolved with the free dynamics does not converge anymore to the free equilibrium state. Actually, we show that its ergodic mean converges to a non-equilibrium steady state for the free theory.
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.
Mechanisms of Edge-Localized-Mode Mitigation by External-Magnetic-Field Perturbations
Tokar, M. Z.; Gupta, A.; Wolf, R. C.; Evans, T. E.; Singh, R.; Kaw, P.
2007-03-02
Particle and energy transport in the tokamak edge transport barrier is analyzed in the presence of magnetic field perturbations from external resonant coils. In recent experiments such coils have been verified as an effective tool for mitigation of the edge-localized modes of type I. The observed reduction of the density in plasmas of low collisionality is explained by the generation of charged particle flows along perturbed field lines. The increase of the electron and ion temperatures in the barrier is interpreted by the reduction of perpendicular neoclassical transport with decreasing density and nonlocality of parallel heat transport. The found modification of the pressure gradient implies the stabilization of ballooning-peeling MHD modes responsible for type I ELMs.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Shinohara, M.; Kikuchi, T.; Nozaki, K.; Yumoto, K.
2002-12-01
Ionospheric electric field perturbations associated with a sudden commencement at 1640 UT Apr. 6, 2000 were observed by the FM-CW HF radar at the dip equator station Cebu, Philippine. Ionograms were obtained from the FM-CW HF radar at intervals of 5 minutes. The zonal electric field can be estimated from the time variation of the height profile of ionograms. A sudden increase in the westward electric field of 1.6 mV/m was observed simultaneously with the sudden increases in the H component magnetic field of 250 and 110 nT at the dayside dip equatorial station Ancon, Peru and the dayside off dip equatorial station Eusebio, Brazil, respectively. The amplitude enhancement of the magnetic variation at the dip equator suggest that an eastward electric field was imposed at the dayside equatorial ionosphere. Both the dayside and nightside electric field perturbations show that the dawn to dusk electric field of DP(MI) was imposed globally on the equatorial ionosphere. The HF Doppler frequency shift was observed at the nightside low latitude station Sugadaira, Japan. From the frequency deviation, it is found that a westward electric field of 2.0 mV/m was suddenly imposed at the beginning of the sc. The amplitude of the westward electric field observed at the nightside equator is 0.8 times that at the nightside low latitude station. It can be caused by the geometrical attenuation [Kikuchi et al., 1978, Nature]. The direction of the zonal electric field observed at Cebu was reversed from westward to eastward and returned westward again. The electric field at Sugardaira shows similar temporal variations. These variations were well correlated with fluctuations of solar wind number density. The eastward electric field may be caused by the over shielding effect of the region 2 field-aligned current [Kikuchi et al., 2000, JGR]. Acknowledgement. The HF Doppler data was provided by Sugadaira Space Radio Observatory, Univ. Electro-Comm.
Neutron stars in a perturbative f(R) gravity model with strong magnetic fields
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.
Cavity perturbation by superconducting films in microwave magnetic and electric fields
NASA Astrophysics Data System (ADS)
Peligrad, D.-N.; Nebendahl, B.; Kessler, C.; Mehring, M.; DulčiĆ, A.; Požek, M.; Paar, D.
1998-11-01
Cavity perturbation by superconducting films is treated in an unified way for the sample positions in both magnetic and electric microwave fields. The role of demagnetizing and depolarizing effects in the boundary conditions of the fields is analyzed. The general solutions for the complex frequency shift are specified for the samples having slab geometry and the field being parallel to the plane of the sample. For electromagnetically thick samples, the shifts for samples placed in the magnetic and electric fields are found to have the same magnitude and temperature dependence, while for thin films dramatic differences are obtained. The magnitude of the shift is reduced in the magnetic and increased by orders of magnitude in the electric field. A remarkable feature in the temperature dependence of the real frequency shift in the electric field is obtained. Experiments are performed on an YBa2Cu3O7-δ thin film, and all the predictions of the theory are confirmed. It is also shown that microwave cavity perturbation and ac susceptibility measurements in a dc magnetic field can be covered by the same theory. Their profoundly different temperature dependence can be accounted for by their different frequencies.
NASA Astrophysics Data System (ADS)
Nandi, Debottam; Shankaranarayanan, S.
2016-10-01
In this work, we present a consistent Hamiltonian analysis of cosmological perturbations for generalized non-canonical scalar fields. In order to do so, we introduce a new phase-space variable that is uniquely defined for different non-canonical scalar fields. We also show that this is the simplest and efficient way of expressing the Hamiltonian. We extend the Hamiltonian approach of [1] to non-canonical scalar field and obtain an unique expression of speed of sound in terms of phase-space variable. In order to invert generalized phase-space Hamilton's equations to Euler-Lagrange equations of motion, we prescribe a general inversion formulae and show that our approach for non-canonical scalar field is consistent. We also obtain the third and fourth order interaction Hamiltonian for generalized non-canonical scalar fields and briefly discuss the extension of our method to generalized Galilean scalar fields.
NASA Astrophysics Data System (ADS)
Moen, Erick K.; Beier, Hope T.; Thompson, Gary L.; Roth, Caleb C.; Ibey, Bennett L.
2014-03-01
Nonlinear optical probes, especially those involving second harmonic generation (SHG), have proven useful as sensors for near-instantaneous detection of alterations to orientation or energetics within a substance. This has been exploited to some success for observing conformational changes in proteins. SHG probes, therefore, hold promise for reporting rapid and minute changes in lipid membranes. In this report, one of these probes is employed in this regard, using nanosecond electric pulses (nsEPs) as a vehicle for instigating subtle membrane perturbations. The result provides a useful tool and methodology for the observation of minute membrane perturbation, while also providing meaningful information on the phenomenon of electropermeabilization due to nsEP. The SHG probe Di- 4-ANEPPDHQ is used in conjunction with a tuned optical setup to demonstrate nanoporation preferential to one hemisphere, or pole, of the cell given a single square shaped pulse. The results also confirm a correlation of pulse width to the amount of poration. Furthermore, the polarity of this event and the membrane physics of both hemispheres, the poles facing either electrode, were tested using bipolar pulses consisting of two pulses of opposite polarity. The experiment corroborates findings by other researchers that these types of pulses are less effective in causing repairable damage to the lipid membrane of cells.
Motion of relativistic particles in axially symmetric and perturbed magnetic fields in a tokamak
de Rover, M.; Lopes Cardozo, N.J.; Montvai, A.
1996-12-01
An extensive comparison is given between an analytical theory for the computations of particle orbits of relativistic runaway electrons [M. de Rover {ital et} {ital al}., Phys. Plasmas {bold 3}, 4468 (1996)], and numerical simulations. A new numerical scheme is used for the computer simulations of guiding center orbits. Furthermore, simulations of the full particle motion, including the gyration are performed to check the guiding center approximation. The behavior of drift surfaces and particle orbits in axially symmetric magnetic fields, as predicted in the companion paper are confirmed. This includes the smaller minor radius of a drift surface compared to a magnetic flux surface with identical rotational transform, and the decrease of the minor radius of a drift surface with increasing particle energy. Magnetic islands and drift islands appear when the axial symmetry of the magnetic field is broken by harmonic perturbations. In the numerical simulations the amplitudes of the perturbations have been chosen to increase towards the plasma edge. The analytic theory gave predictions of the width of the drift islands that are in good agreement with the numerical simulations. When overlap of the magnetic perturbations introduces stochasticity, the Hamiltonian theory shows that drift islands can exist in the region of stochastic magnetic field lines, which is also confirmed by the numerical simulations. {copyright} {ital 1996 American Institute of Physics.}
NASA Astrophysics Data System (ADS)
Rebhan, Anton
1992-06-01
The dynamical equations for rotational (vector) perturbations of a Friedmann-Robertson-Walker universe containing a perfect fluid of massive matter and radiation together with relativistic collisionless matter are established. These equations have solutions which remain regular as the initial singularity is approached, in contrast to the purely perfect-fluid case, where small rotational perturbations cannot coexist with a Friedmann-type singularity due to the Helmholtz-Kelvin circulation theorem. With collisionless matter present (e.g., gravitons after the Planck era), this obstruction is circumvented, and solutions which exhibit a growing mode of vorticity on superhorizon scales are obtained. The anisotropies in the cosmic microwave background caused by these small vector perturbations are analyzed, and limits on admissible primordial vorticity are derived. In the radiation era, large-scale vorticity gives rise to large-scale primordial magnetic fields, which are shown potentially to have the right magnitude to act as seed fields for galactic dynamo action and thereby to explain the presently observed galactic magnetic fields.
Electric field manipulation in Al/CdTe/Pt detectors under optical perturbations
NASA Astrophysics Data System (ADS)
Turturici, A. A.; Franc, J.; Grill, R.; Dědič, V.; Abbene, L.; Principato, F.
2017-06-01
Al/CdTe/Pt detectors are very attractive devices for high-resolution X-ray spectroscopy, even though they suffer from polarization phenomena, which cause a progressive time degradation of the spectroscopic performance. In this work we investigated on the time dependence of the electric field of an Al/CdTe/Pt detector under optical perturbation by means of Pockels effect measurements. A tunable laser with wavelengths ranging within 700-1000 nm and a 940 nm light emitting diode (LED) were used. The measurements of both the electric field profile and the total current were used to better understand the effects of the optical perturbation on polarization phenomena. The results point out as the above band-gap light, due to the trapping of photo-generated holes at the anode (the Al/CdTe blocking contact), brings to a reduction of the negative space charge caused by the bias voltage (bias induced polarization) and the LED irradiation (radiation induced polarization). The reduction of the negative space charge ensures a quite stable and uniform electric field distribution, typically termed depolarization. Conversely, optical perturbation with sub-band-gap light enhances the polarization with the formation of two oppositely charged regions within the detector.
Konoplya, R. A.
2006-01-15
We consider the perturbations of the massive vector field around Schwarzschild, Schwarzschild-de Sitter, and Schwarzschild-anti-de Sitter black holes. Equations for a spherically symmetric massive vector perturbation can be reduced to a single wavelike equation. We have proved the stability against these perturbations and investigated the quasinormal spectrum. The quasinormal behavior for Schwarzschild black hole is quite unexpected: the fundamental mode and higher overtones show totally different dependence on the mass of the field m: as m is increasing, the damping rate of the fundamental mode is decreasing, what results in appearing of the infinitely long living modes, while, on the contrary, damping rate of all higher overtones are increasing, and their real oscillation frequencies gradually go to tiny values. Thereby, for all higher overtones, almost nonoscillatory, damping modes can exist. In the limit of asymptotically high damping, Re{omega} goes to ln3/(8{pi}M), while imaginary part shows equidistant behavior with spacing Im{omega}{sub n+1}-Im{omega}{sub n}=1/4M. In addition, we have found quasinormal spectrum of massive vector field for Schwarzschild-anti-de Sitter black hole.
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
Mirus, Kevin A.
1998-01-01
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.
Frequency characteristics and far-field effect of gravity perturbation before earthquake
NASA Astrophysics Data System (ADS)
Qiang, Jian-Ke; Lu, Kai; Zhang, Qian-Jiang; Man, Kai-Feng; Li, Jun-Ying; Mao, Xian-Cheng; Lai, Jian-Qing
2017-03-01
We used high-pass filtering and the Fourier transform to analyze tidal gravity data prior to five earthquakes from four superconducting gravity stations around the world. A stable gravitational perturbation signal is received within a few days before the earthquakes. The gravitational perturbation signal before the Wenchuan earthquake on May 12, 2008 has main frequency of 0.1-0.3 Hz, and the other four have frequency bands of 0.12-0.17 Hz and 0.06-0.085 Hz. For earthquakes in continental and oceanic plate fault zones, gravity anomalies often appear on the superconducting gravimeters away from the epicenter, whereas the stations near the epicenter record small or no anomalies. The results suggest that this kind of gravitational perturbation signals correlate with earthquake occurrence, making them potentially useful earthquake predictors. The far-field effect of the gravitational perturbation signals may reveal the interaction mechanisms of the Earth's tectonic plates. However, owing to the uneven distribution of gravity tide stations, the results need to be further confirmed in the future.
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.
Kim, Kimin; Ahn, J. -W.; Scotti, F.; ...
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
NASA Technical Reports Server (NTRS)
Fejer, B. G.; Spiro, R. W.; Wolf, R. A.; Foster, J. C.
1990-01-01
F-region incoherent scatter radar drift observations from Millstone Hill and Jicamarca, h-prime F observations from Huancayo, and high latitude ground-magnetometer measurements taken during the Sundial 1986 campaign are used to study the relationship between plasmaspheric electric field perturbations and high latitude currents during disturbed periods. The observations are in good agreement with numerical results from a Rice Covection Model run that involved a sharp increase in the polar cap potential drop followed by a subsequent decrease. The zonal disturbance electric field pattern is latitude independent, and the corresponding amplitudes change approximately as L exp n (where n is about 1.5). The meridional electric field patterns and amplitudes have larger latitudinal variations. The mid-, low, and equatorial electric fields from the Rice Convection Model are in good agreement with previous results from the semianalytic, Senior-Blanc (1987) model. Also discussed are three physical mechanisms (over-shielding, fossil winds, and magnetic reconfiguration) that contribute to the long lasting (1-2 h) equatorial zonal electric field perturbations associated with a sudden northward turning of the IMF. It is predicted that the penetration of high latitude electric fields to low latitudes should, in general, be closely related to the rate of motion of the shielding layer and the equatorward edge of the diffuse aurora.
Conformal blocks of chiral fields in {N}=2 SUSY CFT and affine Laumon spaces
NASA Astrophysics Data System (ADS)
Belavin, V.
2012-10-01
We consider the problem of computing {N}=2 superconformal block functions. We argue that the Kazama-Suzuki coset realization of {N}=2 superconformal algebra in terms of the affine widehat{sl}(2) algebra provides relations between {N}=2 and widehat{sl}(2) conformal blocks. We show that for {N}=2 chiral fields the corresponding sl(2) construction of the conformal blocks is based on the ordinary highest weight representation. We use an AGT-type correspondence to relate the four-point widehat{sl}(2) conformal block with Nekrasov's instanton partition functions of a four-dimensional {N}=2 SU(2) gauge theory in the presence of a surface operator. Since the previous relation proposed by Alday and Tachikawa requires some special modification of the conformal block function, we revisit this problem and find direct correspondence for the four-point conformal block. We thus find an explicit representation for the widehat{sl}(2) four-point conformal block and hence obtain an explicit combinatorial representation for the {N}=2 chiral four-point conformal block.
Wang, Zhiyong; Xu, Jinbo
2011-07-01
Accurate tertiary structures are very important for the functional study of non-coding RNA molecules. However, predicting RNA tertiary structures is extremely challenging, because of a large conformation space to be explored and lack of an accurate scoring function differentiating the native structure from decoys. The fragment-based conformation sampling method (e.g. FARNA) bears shortcomings that the limited size of a fragment library makes it infeasible to represent all possible conformations well. A recent dynamic Bayesian network method, BARNACLE, overcomes the issue of fragment assembly. In addition, neither of these methods makes use of sequence information in sampling conformations. Here, we present a new probabilistic graphical model, conditional random fields (CRFs), to model RNA sequence-structure relationship, which enables us to accurately estimate the probability of an RNA conformation from sequence. Coupled with a novel tree-guided sampling scheme, our CRF model is then applied to RNA conformation sampling. Experimental results show that our CRF method can model RNA sequence-structure relationship well and sequence information is important for conformation sampling. Our method, named as TreeFolder, generates a much higher percentage of native-like decoys than FARNA and BARNACLE, although we use the same simple energy function as BARNACLE. zywang@ttic.edu; j3xu@ttic.edu Supplementary data are available at Bioinformatics online.
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.
Next-Generation Force Fields from Symmetry-Adapted Perturbation Theory.
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.
NASA Astrophysics Data System (ADS)
Kim, Kimin; Jeon, Y. M.; Park, J.-K.; Ko, W. H.; In, Y.; Choe, W.; Kim, J.; Lee, S. G.; Yoon, S. W.; Kwak, J. G.; Oh, Y. K.
2017-03-01
The variation of a magnetic braking profile by non-axisymmetric magnetic fields has been experimentally demonstrated and numerically validated in the KSTAR tokamak. Two types of n = 2 non-resonant magnetic fields were applied by changing the relative phase of non-axisymmetric field coils. One is even parity, of which non-resonant fields deeply penetrate into the plasma core, and the other is odd parity localized at the plasma edge. The even and odd parity produced significantly different perturbed magnetic field structures, and thereby drove global and edge-dominant toroidal rotation damping, respectively. These distinct braking profiles are consistently reproduced by drift-kinetic particle simulations, indicating the possibility of the predictive utilization of non-resonant magnetic fields for rotation profile control.
Domain walls, fusion rules, and conformal field theory in the quantum Hall regime.
Ardonne, Eddy
2009-05-08
We provide a simple way to obtain the fusion rules associated with elementary quasiholes over quantum Hall wave functions, in terms of domain walls. The knowledge of the fusion rules is helpful in the identification of the underlying conformal field theory describing the wave functions. We show that, for a certain two-parameter family (k,r) of wave functions, the fusion rules are those of su(r)k. In addition, we give an explicit conformal field theory construction of these states, based on the Mk(k+1,k+r) "minimal" theories. For r=2, these states reduce to the Read-Rezayi states. The "Gaffnian" wave function is the prototypical example for r>2, in which case the conformal field theory is nonunitary.
Tzanov, Alexandar T; Cuendet, Michel A; Tuckerman, Mark E
2014-06-19
The quality of classical biomolecular simulations is inevitably limited by two problems: the accuracy of the force field used and the comprehensiveness of configuration space sampling. In this work we tackle the sampling problem by carrying out driven adiabatic free energy dynamics to obtain converged free energy surfaces of dipeptides in the gas phase and in solution using selected dihedral angles as collective variables. To calculate populations of conformational macrostates observed in experiment, we introduce a fuzzy clustering algorithm in collective-variable space, which delineates macrostates without prior definition of arbitrary boundaries. With this approach, we calculate the conformational preferences of small peptides with six biomolecular force fields chosen from among the most recent and widely used. We assess the accuracy of each force field against recently published Raman or IR-UV spectroscopy measurements of conformer populations for the dipeptides in solution or in the gas phase.
Modified Amber Force Field Correctly Models the Conformational Preference for Tandem GA pairs in RNA
2015-01-01
Molecular mechanics with all-atom models was used to understand the conformational preference of tandem guanine-adenine (GA) noncanonical pairs in RNA. These tandem GA pairs play important roles in determining stability, flexibility, and structural dynamics of RNA tertiary structures. Previous solution structures showed that these tandem GA pairs adopt either imino (cis Watson–Crick/Watson–Crick A-G) or sheared (trans Hoogsteen/sugar edge A-G) conformations depending on the sequence and orientation of the adjacent closing base pairs. The solution structures (GCGGACGC)2 [Biochemistry, 1996, 35, 9677–9689] and (GCGGAUGC)2 [Biochemistry, 2007, 46, 1511–1522] demonstrate imino and sheared conformations for the two central GA pairs, respectively. These systems were studied using molecular dynamics and free energy change calculations for conformational changes, using umbrella sampling. For the structures to maintain their native conformations during molecular dynamics simulations, a modification to the standard Amber ff10 force field was required, which allowed the amino group of guanine to leave the plane of the base [J. Chem. Theory Comput., 2009, 5, 2088–2100] and form out-of-plane hydrogen bonds with a cross-strand cytosine or uracil. The requirement for this modification suggests the importance of out-of-plane hydrogen bonds in stabilizing the native structures. Free energy change calculations for each sequence demonstrated the correct conformational preference when the force field modification was used, but the extent of the preference is underestimated. PMID:24803859
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.
On the reach of perturbative descriptions for dark matter displacement fields
Baldauf, Tobias; Zaldarriaga, Matias; Schaan, Emmanuel E-mail: eschaan@astro.princeton.edu
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{sup −1}Mpc at z = 0. Predicting the displacement power spectrum to higher accuracy or larger wavenumbers thus requires a model for the stochastic displacement.
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.
NASA Astrophysics Data System (ADS)
Gilmore, James Brian
2010-12-01
General Relativity is the standard framework by which all gravitational systems are analyzed in modern research, and it provides the theme for all the investigations in this thesis. Beyond this common platform, very different gravitating problems are examined here, and several analytical approaches are used to investigate these systems. Effective field theory, a methodological approach prominent in quantum field theory, plays an important role in the analysis of two of the problems in this thesis. In the first instance, an effective field theory for bound gravitational states is used to compute the interaction Lagrangian of a binary system at the second post-Newtonian order. A metric parametrization based on a temporal Kaluza-Klein decomposition is also used. In this effective field theory calculation, the post-Newtonian results for the equations of motion are elegantly reproduced. In the next problem considered, effective field theory is used to investigate the thermodynamics of compactified charged black holes. The relevant thermodynamic quantities are all computed to second order in the perturbation parameter and finite size effects are incorporated through higher order worldline operators. Complete agreement is found with an exact extremal black hole solution constructed with traditional General Relativistic methods. The results indicate that the addition of charge to a compactified black hole may delay the phase transition to a black string. Finally, the third problem examined here concerns the evolution of perturbations at the end of early universe inflation. General Relativity enters this problem through cosmological perturbation theory. It is shown that the coherent oscillations in the inflaton break down at the comoving post-inflationary horizon size, about 14 e-folds after the end of inflation. This is many e-folds before any known constraints, leading to possible implications for the matching problem of inflation, and the generation of stochastic
Second-Order Perturbation Theory for Generalized Active Space Self-Consistent-Field Wave Functions.
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.
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.,
NASA Astrophysics Data System (ADS)
Crop, F.; Reynaert, N.; Pittomvils, G.; Paelinck, L.; DeWagter, C.; Vakaet, L.; Thierens, H.
2009-05-01
The purpose of this study was the investigation of perturbation factors for microionization chambers in small field dosimetry and the influence of penumbra for different spot sizes. To this purpose, correlated sampling was implemented in the EGSnrc Monte Carlo (MC) user code cavity: CScavity. CScavity was first benchmarked against results in the literature for an NE2571 chamber. An efficiency increase of 17 was attained for the calculation of a realistic chamber perturbation factor in a water phantom. Calculations have been performed for microionization chambers of type PinPoint 31006 and PinPoint 31016 in full BEAMnrc linac simulations. Investigating the physical backgrounds of the differences for these small field settings, perturbation factors have been split up into (1) central electrode perturbation, (2) wall perturbation, (3) air-to-water perturbation (chamber volume air-to-water) and (4) water volume perturbation (water chamber volume to 1 mm3 voxel). The influence of different spot sizes, position in penumbra, measuring depth and detector geometry on these perturbation factors has been investigated, in a 0.8 × 0.8 cm2 field setting. pcel for the PP31006 steel electrode shows a variation of up to 1% in the lateral position, but only 0.4% for the PP31016 with an Al electrode. The air-to-water perturbation in the optimal scanning direction for both profiles and depth is most influenced by the radiation field, and only to a small extent the chamber geometry. The PP31016 geometry (shorter, larger radius) requires less total perturbation within the central axis of the field, but results in slightly larger variations off axis in the optimal scanning direction. Smaller spot sizes (0.6 mm FWHM) and sharper penumbras, compared to larger spot sizes (2 mm FWHM), result in larger perturbation starting in the penumbra. The longer geometries of the PP31006/14/15 exhibit in the non-optimal scanning direction large variations in total perturbation (ptot 1.201(4) (0.6 mm
Universality of sparse d > 2 conformal field theory at large N
NASA Astrophysics Data System (ADS)
Belin, Alexandre; de Boer, Jan; Kruthoff, Jorrit; Michel, Ben; Shaghoulian, Edgar; Shyani, Milind
2017-03-01
We derive necessary and sufficient conditions for large N conformal field theories to have a universal free energy and an extended range of validity of the higher-dimensional Cardy formula. These constraints are much tighter than in two dimensions and must be satisfied by any conformal field theory dual to Einstein gravity. We construct and analyze symmetric product orbifold theories on T^d and show that they only realize the necessary phase structure and extended range of validity if the seed theory is assumed to have a universal vacuum energy.
Rational Conformal Correlation Functions of Gauge-Invariant Local Fields in Four Dimensions
Nikolov, N.M.; Stanev, Ya.S.; Todorov, I.T.
2005-11-01
Global conformal invariance in Minkowski space and the Wightman axioms imply strong locality (Huygens principle) and rationality of correlation functions, thus providing an extension of the concept of a vertex algebra to higher (even) dimensions D. We (p)review current work on a model of a Hermitian scalar field L of scale dimension 4 (D = 4) which can be interpreted as the Lagrangian of a gauge field theory that generates the algebra of gauge-invariant local observables in a conformally invariant renormalization group fixed point.
Del Giudice, Rita; Arciello, Angela; Itri, Francesco; Merlino, Antonello; Monti, Maria; Buonanno, Martina; Penco, Amanda; Canetti, Diana; Petruk, Ganna; Monti, Simona Maria; Relini, Annalisa; Pucci, Piero; Piccoli, Renata; Monti, Daria Maria
2016-02-01
Amyloidoses are devastating diseases characterized by accumulation of misfolded proteins which aggregate in fibrils. Specific gene mutations in Apolipoprotein A I (ApoAI) are associated with systemic amyloidoses. Little is known on the effect of mutations on ApoAI structure and amyloid properties. Here we performed a physico-chemical characterization of L75P- and L174S-amyloidogenic ApoAI (AApoAI) variants to shed light on the effects of two single point mutations on protein stability, proteolytic susceptibility and aggregation propensity. Both variants are destabilized in their N-terminal region and generate fibrils with different morphological features. L75P-AApoAI is significantly altered in its conformation and compactness, whereas a more flexible and pronounced aggregation-competent state is associated to L174S-AApoAI. These observations point out how single point mutations in ApoAI gene evocate differences in the physico-chemical and conformational behavior of the corresponding protein variants, with the common feature of diverting ApoAI from its natural role towards a pathogenic pathway.
Primordial black holes from inflaton and spectator field perturbations in a matter-dominated era
NASA Astrophysics Data System (ADS)
Carr, Bernard; Tenkanen, Tommi; Vaskonen, Ville
2017-09-01
We study production of primordial black holes (PBHs) during an early matter-dominated phase. As a source of perturbations, we consider either an inflaton field with a running spectral index or a spectator field that has a blue spectrum and thus provides a significant contribution to PBH production at small scales. First, we identify the region of the parameter space where a significant fraction of the observed dark matter can be produced, taking into account all current PBH constraints. Then, we present constraints on the amplitude and spectral index of the spectator field as a function of the reheating temperature. We also derive constraints on the running of the inflaton spectral index, d n /d ln k ≲0.001 , which are comparable to those from the Planck satellite for a scenario where the spectator field is absent.
NASA Astrophysics Data System (ADS)
Bai, Xue; Liu, Yueqiang; Gao, Zhe
2017-10-01
Plasma response to the resonant magnetic perturbation (RMP) field is numerically investigated by an extended toroidal fluid model, which includes anisotropic thermal transport physics parallel and perpendicular to the total magnetic field. The thermal transport is found to be effective in eliminating the toroidal average curvature induced plasma screening (the so called Glasser-Green-Johnson, GGJ screening) in a slow toroidal flow regime, whilst having minor effect on modifying the conventional plasma screening regimes at faster flow. This physics effect of interaction between thermal transport and GGJ screening is attributed to the modification of the radial structure of the shielding current, which resulted from the plasma response to the applied field. The modification of the plasma response (shielding current, response field, plasma displacement, and the perturbed velocity) also has direct consequence on the toroidal torques produced by RMP. Modelling results show that thermal transport reduces the resonant electromagnetic torque as well as the torque associated with the Reynolds stress, but enhances the neoclassical toroidal viscous torque at slow plasma flow.
From charge motion in general magnetic fields to the non perturbative gyrokinetic equation
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.
On twistors and conformal field theories from six dimensions
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.
NASA Astrophysics Data System (ADS)
Hikage, Chiaki; Koyama, Kazuya; Heavens, Alan
2017-08-01
We compute the power spectrum at one-loop order in standard perturbation theory for the matter density field to which a standard Lagrangian baryonic acoustic oscillation (BAO) reconstruction technique is applied. The BAO reconstruction method corrects the bulk motion associated with the gravitational evolution using the inverse Zel'dovich approximation (ZA) for the smoothed density field. We find that the overall amplitude of one-loop contributions in the matter power spectrum substantially decreases after reconstruction. The reconstructed power spectrum thereby approaches the initial linear spectrum when the smoothed density field is close enough to linear, i.e., the smoothing scale Rs≳10 h-1 Mpc . On smaller Rs, however, the deviation from the linear spectrum becomes significant on large scales (k ≲Rs-1 ) due to the nonlinearity in the smoothed density field, and the reconstruction is inaccurate. Compared with N-body simulations, we show that the reconstructed power spectrum at one-loop order agrees with simulations better than the unreconstructed power spectrum. We also calculate the tree-level bispectrum in standard perturbation theory to investigate non-Gaussianity in the reconstructed matter density field. We show that the amplitude of the bispectrum significantly decreases for small k after reconstruction and that the tree-level bispectrum agrees well with N-body results in the weakly nonlinear regime.
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.
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.
Riemann correlator in de Sitter including loop corrections from conformal fields
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.
NASA Astrophysics Data System (ADS)
Fritz, Sean; Hernandez-Castillo, Alicia O.; Abeysekera, Chamara; Zwier, Timothy S.
2017-06-01
The 8-18 GHz conformer specific rotational spectrum of gauche- and anti-3-phenylpropionitrile (C6H5-CH2-CH2-CN) conformers has been recorded using the strong field coherence breaking (SFCB) technique [1] with a modified line picking scheme for multiple selective excitations (MSE). As the recombination product of benzyl and cyanomethyl resonance-stabilized radicals, 3-phenylpropionitrile is a likely component of the complex organics in Titan's atmosphere, motivating its structural characterization. Details of the modified line picking scheme, hyperfine constants and relative population ratios of the two conformers will be presented. [1] A.O Hernandez-Castillo, Chamara Abeysekera, Brian M. Hays, Timothy S. Zwier, "Broadband Multi-Resonant Strong Field Coherence Breaking as a Tool for Single Isomer Microwave Spectroscopy." J. Chem. Phys. 145, 114203 (2016).
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.
SL(2, z) Action on Three-Dimensional Conformal Field Theories with Abelian Symmetry
NASA Astrophysics Data System (ADS)
Witten, Edward
On the space of three-dimensional conformal field theories with U(1) symmetry and a chosen coupling to a background gauge field, there is a natural action of the group SL(2, Z). The generator S of SL(2, Z) acts by letting the background gauge field become dynamical, an operation considered recently by Kapustin and Strassler in explaining three-dimensional mirror symmetry. The other generator T acts by shifting the Chern-Simons coupling of the background field. This SL(2, Z) action in three dimensions is related by the AdS/CFT correspondence to SL(2, Z) duality of low energy U(1) gauge fields in four dimensions.
NASA Astrophysics Data System (ADS)
Askinazi, L. G.; Bulanin, V. V.; Kornev, V. A.; Krikunov, S. V.; Lebedev, S. V.; Tukachinsky, A. S.; Vildjunas, M. I.; Zhubr, N. A.
2011-03-01
The results of the experimental study of confinement mode bifurcation performed on the TUMAN-3M tokamak are reported. As a trigger of confinement mode switching, plasma current ramp-up/-down or magnetic compression/decompression is used. It is found that the possibility and direction of confinement mode switching are correlated not with plasma current profile perturbation (peaking or broadening) but with the sign of toroidal electric field perturbation. A model connecting confinement bifurcation and toroidal electric field perturbation through the perturbation of the radial electric field is used to describe the phenomena observed in all eight scenarios investigated. This model ascribes the radial electric field generation to the non-compensated Ware drift of banana electrons at the TUMAN-3M peripheral plasma, where \
Use of Earth’s Magnetic Field for Mitigating Gyroscope Errors Regardless of Magnetic Perturbation
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
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.
Use of Earth's magnetic field for mitigating gyroscope errors regardless of magnetic perturbation.
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.
Tumor Treating Fields Perturb the Localization of Septins and Cause Aberrant Mitotic Exit
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
Tumor treating fields perturb the localization of septins and cause aberrant mitotic exit.
Gera, Nidhi; Yang, Aaron; 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.
Entanglement scaling and spatial correlations of the transverse-field Ising model with perturbations
NASA Astrophysics Data System (ADS)
Cole, Richard; Pollmann, Frank; Betouras, Joseph J.
2017-06-01
We study numerically the entanglement entropy and spatial correlations of the one-dimensional transverse-field Ising model with three different perturbations. First, we focus on the out-of-equilibrium steady state with an energy current passing through the system. By employing a variety of matrix-product state based methods, we confirm the phase diagram and compute the entanglement entropy. Second, we consider a small perturbation that takes the system away from integrability and calculate the correlations, the central charge, and the entanglement entropy. Third, we consider periodically weakened bonds, exploring the phase diagram and entanglement properties first in the situation when the weak and strong bonds alternate (period two bonds) and then the general situation of a period of n bonds. In the latter case we find a critical weak bond that scales with the transverse field as Jc'/J =(h/J ) n , where J is the strength of the strong bond, J' is that of the weak bond, and h is the transverse field. We explicitly show that the energy current is not a conserved quantity in this case.
Garcia Aspeitia, Miguel A.; Matos, Tonatiuh; Rodriguez, Pablo A.; Magana, Juan Aldebaran
2010-07-12
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 V{sub {Phi}}= (1/2)m{sub {Phi}}{sup 2{Phi}2} 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 {Phi} and {Phi} of the inflation in the hidden brane.
Conformal Flow on S3 and Weak Field Integrability in AdS4
NASA Astrophysics Data System (ADS)
Bizoń, Piotr; Craps, Ben; Evnin, Oleg; Hunik, Dominika; Luyten, Vincent; Maliborski, Maciej
2017-08-01
We consider the conformally invariant cubic wave equation on the Einstein cylinder {\\mathbb{R} × \\mathbb{S}^3} for small rotationally symmetric initial data. This simple equation captures many key challenges of nonlinear wave dynamics in confining geometries, while a conformal transformation relates it to a self-interacting conformally coupled scalar in four-dimensional anti-de Sitter spacetime (AdS4) and connects it to various questions of AdS stability. We construct an effective infinite-dimensional time-averaged dynamical system accurately approximating the original equation in the weak field regime. It turns out that this effective system, which we call the conformal flow, exhibits some remarkable features, such as low-dimensional invariant subspaces, a wealth of stationary states (for which energy does not flow between the modes), as well as solutions with nontrivial exactly periodic energy flows. Based on these observations and close parallels to the cubic Szegő equation, which was shown by Gérard and Grellier to be Lax-integrable, it is tempting to conjecture that the conformal flow and the corresponding weak field dynamics in AdS4 are integrable as well.
Interaction of plasma rotation and resonant magnetic perturbation fields in tokamaks
NASA Astrophysics Data System (ADS)
Nicolai, A.; Daybelge, U.; Lehnen, M.; Tokar, M. Z.; Unterberg, B.; Yarim, C.; contributors, JET
2008-02-01
The interaction between plasma rotation and perturbation fields is described by the ambipolarity constraint and the parallel momentum balance, both emanating from the revisited neoclassical theory, and the electrodynamical screening of the resonant perturbation field at the singular surfaces. This screening depends mainly on the slip between the rotating plasma and the resonant field. The neoclassical theory, valid in the collision dominated regime and accounting for gyro-viscosity, includes arbitrary plasma cross-sections, anomalous viscosity, ponderomotive forces, neutral beam injection (NBI), pressure anisotropization and a momentum source due to ergodicity which has a considerable impact on the plasma rotation as demonstrated in TEXTOR. To estimate the influence of the perturbation coils on the plasma rotation, the radial magnetic field (proportional to the helical flux function) is Fourier analysed (using 'intrinsic' coordinates) and the total field is used for field line tracing thus obtaining the ponderomotive momentum input and the extension Δe of the ergodic layer at the edge. Both procedures account for the full plasma geometry. Δe is assumed to be independent of the rotational state because of the boundary condition Vt = 0. In a second step the obtained velocity profiles are used to compute the screening at the singular layers and thus the reduction of the island width due to plasma rotation. The main results can be summarized as follows. Using in the case of TEXTOR shot #94092 the diffusion coefficient DM = 2 × 10-6 m (typical for the 12/4 configuration) the observed increase in vt by Δvt ≈ 5 km s-1 can be reproduced. Inside the plasma the slip prevents any influence of the ponderomotive forces, thus yielding a constant increase in the vt(r)-profile by Δvt. Assuming in the case of the error field correction coils (n = 1) of JET the current Ihel = 30 kA and using for the plasma background the data of shot #67951 in the static case, an ergodized
Quasi-two-dimensional perturbations in duct flows under transverse magnetic field
NASA Astrophysics Data System (ADS)
Pothérat, A.
2007-07-01
Inspired by the experiment from Moresco and Alboussiere [J. Fluid Mech. 504, 167 (2004)], we study the stability of a flow of liquid metal in a rectangular, electrically insulating duct with a steady homogeneous magnetic field perpendicular to two of the walls. In this configuration, the Lorentz force tends to eliminate the velocity variations in the direction of the magnetic field. This leads to a quasi-two-dimensional base flow with Hartmann boundary layers near the walls perpendicular to the magnetic field, and so-called Shercliff layers in the vicinity of the walls parallel to the field. Also, the Lorentz force tends to strongly oppose the growth of perturbations with a dependence along the magnetic field direction. On these grounds, we represent the flow using the model from Sommeria and Moreau [J. Fluid Mech. 118, 507 (1982)], which essentially consists of two-dimensional (2D) motion equations with a linear friction term accounting for the effect of the Hartmann layers. The simplicity of this quasi-2D model makes it possible to study the stability and transient growth of quasi-two-dimensional perturbations over an extensive range of nondimensional parameters and reach the limit of high magnetic fields. In this asymptotic case, the Reynolds number based on the Shercliff layer thickness Re /H1/2 becomes the only relevant parameter. Tollmien-Schlichting waves are the most linearly unstable mode as for the Poiseuille flow, but for H≳42, a second unstable mode, symmetric about the duct axis, appears with a lower growth rate. We find that these layers are linearly unstable for Re /H1/2≳48350 and energetically stable for Re /H1/2≲65.32. Between these two bounds, some nonmodal quasi-two-dimensional perturbations undergo some significant transient growth (between two and seven times more than in the case of a purely 2D Poiseuille flow, and for much more subcritical values of Re). In the limit of a high magnetic field, the maximum gain Gmax associated with this
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.
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.
Determination of the conformal-field-theory central charge by the Wang-Landau algorithm
NASA Astrophysics Data System (ADS)
Belov, P. A.; Nazarov, A. A.; Sorokin, A. O.
2017-06-01
We present a simple method to estimate the central charge of the conformal field theory corresponding to a critical point of a two-dimensional lattice model from Monte Carlo simulations. The main idea is to use the Wang-Landau flat-histogram algorithm, which allows us to obtain the free energy of a lattice model on a torus as a function of torus radii. The central charge is calculated with good precision from a free-energy scaling at the critical point. We apply the method to the Ising, tricritical Ising (Blume-Capel), Potts, and site-diluted Ising models, and we also discuss an estimation of the conformal weights.
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.
Diagnosing Chaos Using Four-Point Functions in Two-Dimensional Conformal Field Theory.
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.
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.
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.
NASA Astrophysics Data System (ADS)
Antunes, V.; Novello, M.
2017-04-01
In the present work we revisit a model consisting of a scalar field with a quartic self-interaction potential non-minimally (conformally) coupled to gravity (Novello in Phys Lett 90A:347 1980). When the scalar field vacuum is in a broken symmetry state, an effective gravitational constant emerges which, in certain regimes, can lead to gravitational repulsive effects when only ordinary radiation is coupled to gravity. In this case, a bouncing universe is shown to be the only cosmological solution admissible by the field equations when the scalar field is in such broken symmetry state.
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.
Conformal Nets II: Conformal Blocks
NASA Astrophysics Data System (ADS)
Bartels, Arthur; Douglas, Christopher L.; Henriques, André
2017-08-01
Conformal nets provide a mathematical formalism for conformal field theory. Associated to a conformal net with finite index, we give a construction of the `bundle of conformal blocks', a representation of the mapping class groupoid of closed topological surfaces into the category of finite-dimensional projective Hilbert spaces. We also construct infinite-dimensional spaces of conformal blocks for topological surfaces with smooth boundary. We prove that the conformal blocks satisfy a factorization formula for gluing surfaces along circles, and an analogous formula for gluing surfaces along intervals. We use this interval factorization property to give a new proof of the modularity of the category of representations of a conformal net.
Conformal Nets II: Conformal Blocks
NASA Astrophysics Data System (ADS)
Bartels, Arthur; Douglas, Christopher L.; Henriques, André
2017-03-01
Conformal nets provide a mathematical formalism for conformal field theory. Associated to a conformal net with finite index, we give a construction of the `bundle of conformal blocks', a representation of the mapping class groupoid of closed topological surfaces into the category of finite-dimensional projective Hilbert spaces. We also construct infinite-dimensional spaces of conformal blocks for topological surfaces with smooth boundary. We prove that the conformal blocks satisfy a factorization formula for gluing surfaces along circles, and an analogous formula for gluing surfaces along intervals. We use this interval factorization property to give a new proof of the modularity of the category of representations of a conformal net.
NASA Astrophysics Data System (ADS)
Khan, Suhail; Hussain, Tahir; Khan, Gulzar Ali
The aim of this paper is to explore teleparallel conformal Killing vector fields (CKVFs) of locally rotationally symmetric (LRS) Bianchi type V spacetimes in the context of teleparallel gravity and compare the obtained results with those of general relativity (GR). The general solution of teleparallel conformal Killing's equations is found in terms of some unknown functions of t and x, along with a set of integrability conditions. The integrability conditions are solved in some particular cases to get the final form of teleparallel CKVFs. It is observed that the LRS Bianchi type V spacetimes admit proper teleparallel CKVF in only one case, while in remaining cases the teleparallel CKVFs reduce to teleparallel Killing vector fields (KVFs). Moreover, it is shown that the LRS Bianchi type V spacetimes do not admit any proper teleparallel homothetic vector field (HVF).
Rotation and radial electric field in the plasma edge with resonant magnetic perturbation at TEXTOR
NASA Astrophysics Data System (ADS)
Coenen, J. W.; Schmitz, O.; Unterberg, B.; Clever, M.; Jakubowski, M. A.; Samm, U.; Schweer, B.; Stoschus, H.; Tokar, M.; TEXTOR-Team
2011-06-01
In this paper the results of a systematic experimental assessment of the plasma edge rotation and radial electric field with application of resonant magnetic perturbation (RMP) are presented. The results are based on the radially resolved measurement of the poloidal (vpol) and toroidal (vtor) rotation. It is shown that the radial electric field Er can be deduced from the radial force balance when small amplitude resonant magnetic perturbations are applied to the plasma boundary (Br/Btor ~ 10-4). Both vpol and vtor spin-up in the ion-diamagnetic-drift and co-current direction, respectively, with increasing external perturbation field (Δvpol ~ 15 km s-1, Δvtor ~ 2-5 km s-1) yielding an increase in Er by ΔEr,max = 9 kV m-1. The toroidal rotation increases over the whole radius while the poloidal rotation shows distinct local features driving the evolution of the Er-profiles. Depending on the edge safety factor a local (at the q = 5/2 rational surface) increase in the shear rate ΩE×B (ΔΩq=5/2 = 1.4 × 105 s-1) or reduced shearing can occur. Increased shearing is correlated with an improved particle confinement with an increase in the particle confinement time by Δτp = +40%. Increasing the local resonant amplitude by 30% induces a reduced density level, the so-called RMP induced pump-out. At this confinement stage the shear rate decreases by 15% correlated with a significant drop in particle confinement (Δτp = -30%). Field line tracing in the vacuum approximation gives indications towards explaining the threshold behaviour connecting the shearing rate, confinement stages and magnetic topology to the amount of applied RMP. However, this basic approach does not account for plasma response and the results presented are linked in the discussion section to recent results on the link between rotation and plasma response as well as on the transport features of RMP.
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.
Covariant second-order perturbations in generalized two-field inflation
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.
Is the Conformational Ensemble of Alzheimer's Aβ10-40 Peptide Force Field Dependent?
Siwy, Christopher M; Lockhart, Christopher; Klimov, Dmitri K
2017-01-01
By applying REMD simulations we have performed comparative analysis of the conformational ensembles of amino-truncated Aβ10-40 peptide produced with five force fields, which combine four protein parameterizations (CHARMM36, CHARMM22*, CHARMM22/cmap, and OPLS-AA) and two water models (standard and modified TIP3P). Aβ10-40 conformations were analyzed by computing secondary structure, backbone fluctuations, tertiary interactions, and radius of gyration. We have also calculated Aβ10-40 3JHNHα-coupling and RDC constants and compared them with their experimental counterparts obtained for the full-length Aβ1-40 peptide. Our study led us to several conclusions. First, all force fields predict that Aβ adopts unfolded structure dominated by turn and random coil conformations. Second, specific TIP3P water model does not dramatically affect secondary or tertiary Aβ10-40 structure, albeit standard TIP3P model favors slightly more compact states. Third, although the secondary structures observed in CHARMM36 and CHARMM22/cmap simulations are qualitatively similar, their tertiary interactions show little consistency. Fourth, two force fields, OPLS-AA and CHARMM22* have unique features setting them apart from CHARMM36 or CHARMM22/cmap. OPLS-AA reveals moderate β-structure propensity coupled with extensive, but weak long-range tertiary interactions leading to Aβ collapsed conformations. CHARMM22* exhibits moderate helix propensity and generates multiple exceptionally stable long- and short-range interactions. Our investigation suggests that among all force fields CHARMM22* differs the most from CHARMM36. Fifth, the analysis of 3JHNHα-coupling and RDC constants based on CHARMM36 force field with standard TIP3P model led us to an unexpected finding that in silico Aβ10-40 and experimental Aβ1-40 constants are generally in better agreement than these quantities computed and measured for identical peptides, such as Aβ1-40 or Aβ1-42. This observation suggests that the
Is the Conformational Ensemble of Alzheimer’s Aβ10-40 Peptide Force Field Dependent?
Siwy, Christopher M.
2017-01-01
By applying REMD simulations we have performed comparative analysis of the conformational ensembles of amino-truncated Aβ10-40 peptide produced with five force fields, which combine four protein parameterizations (CHARMM36, CHARMM22*, CHARMM22/cmap, and OPLS-AA) and two water models (standard and modified TIP3P). Aβ10-40 conformations were analyzed by computing secondary structure, backbone fluctuations, tertiary interactions, and radius of gyration. We have also calculated Aβ10-40 3JHNHα-coupling and RDC constants and compared them with their experimental counterparts obtained for the full-length Aβ1-40 peptide. Our study led us to several conclusions. First, all force fields predict that Aβ adopts unfolded structure dominated by turn and random coil conformations. Second, specific TIP3P water model does not dramatically affect secondary or tertiary Aβ10-40 structure, albeit standard TIP3P model favors slightly more compact states. Third, although the secondary structures observed in CHARMM36 and CHARMM22/cmap simulations are qualitatively similar, their tertiary interactions show little consistency. Fourth, two force fields, OPLS-AA and CHARMM22* have unique features setting them apart from CHARMM36 or CHARMM22/cmap. OPLS-AA reveals moderate β-structure propensity coupled with extensive, but weak long-range tertiary interactions leading to Aβ collapsed conformations. CHARMM22* exhibits moderate helix propensity and generates multiple exceptionally stable long- and short-range interactions. Our investigation suggests that among all force fields CHARMM22* differs the most from CHARMM36. Fifth, the analysis of 3JHNHα-coupling and RDC constants based on CHARMM36 force field with standard TIP3P model led us to an unexpected finding that in silico Aβ10-40 and experimental Aβ1-40 constants are generally in better agreement than these quantities computed and measured for identical peptides, such as Aβ1-40 or Aβ1-42. This observation suggests that the
World sheet commuting {beta}{gamma} conformal field theory and nonrelativistic string theories
Kim, Bom Soo
2007-11-15
We construct a sigma model in two dimensions with Galilean symmetry in flat target space similar to the sigma model of the critical string theory with Lorentz symmetry in 10 flat spacetime dimensions. This is motivated by the works of Gomis and Ooguri [J. Math. Phys. (N.Y.) 42, 3127 (2001)] and Danielsson et al. [J. High Energy Phys. 10 (2000) 020; J. High Energy Phys. 03 (2001) 041.]. Our theory is much simpler than their theory and does not assume a compact coordinate. This nonrelativistic string theory has a bosonic matter {beta}{gamma} conformal field theory with the conformal weight of {beta} as 1. It is natural to identify time as a linear combination of {gamma} and {gamma} through an explicit realization of the Galilean boost symmetry. The angle between {gamma} and {gamma} parametrizes one parameter family of selection sectors. These selection sectors are responsible for having a nonrelativistic dispersion relation without a nontrivial topology in the nonrelativistic setup, which is one of the major differences from the previous works of Gomis and Ooguri and of Danielsson and co-workers. This simple theory is the nonrelativistic analogue of the critical string theory, and there are many different avenues ahead to be investigated. We mention a possible consistent generalization of this theory with different conformal weights for the {beta}{gamma} conformal field theory. We also mention supersymmetric generalizations of these theories.
Parameterization of OPLS-AA force field for the conformational analysis of macrocyclic polyketides.
Kahn, Kalju; Bruice, Thomas C
2002-07-30
The parameters for the OPLS-AA potential energy function have been extended to include some functional groups that are present in macrocyclic polyketides. Existing OPLS-AA torsional parameters for alkanes, alcohols, ethers, hemiacetals, esters, and ketoamides were improved based on MP2/aug-cc-pVTZ and MP2/aug-cc-pVDZ calculations. Nonbonded parameters for the sp(3) carbon and oxygen atoms were refined using Monte Carlo simulations of bulk liquids. The resulting force field predicts conformer energies and torsional barriers of alkanes, alcohols, ethers, and hemiacetals with an overall RMS deviation of 0.40 kcal/mol as compared to reference data. Densities of 19 bulk liquids are predicted with an average error of 1.1%, and heats of vaporization are reproduced within 2.4% of experimental values. The force field was used to perform conformational analysis of smaller analogs of the macrocyclic polyketide drug FK506. Structures that adopted low-energy conformations similar to that of bound FK506 were identified. The results show that a linker of four ketide units constitutes the shortest effector domain that allows binding of the ketide drugs to FKBP proteins. It is proposed that the exact chemical makeup of the effector domain has little influence on the conformational preference of tetraketides.
Asciutto, Eliana K; Gedeon, Patrick C; General, Ignacio J; Madura, Jeffry D
2016-08-25
The bacterial leucine transporter (LeuT), a close homologue of the eukaryote monoamine transporters (MATs), currently serves as a powerful template for computer simulations of MATs. Transport of the amino acid leucine through the membrane is made possible by the sodium electrochemical potential. Recent reports indicate that the substrate transport mechanism is based on structural changes such as hinge movements of key transmembrane domains. In order to further investigate the role of sodium ions in the uptake of leucine, here we present a Markov state model analysis of atomistic simulations of lipid embedded LeuT in different environments, generated by varying the presence of binding pocket sodium ions and substrate. Six metastable conformations are found, and structural differences between them along with transition probabilities are determined. We complete the analysis with the implementation of perturbation response scanning on our system, determining the most sensitive and influential regions of LeuT, in each environment. Our results show that the occupation of sites Na1 and Na2, along with the presence of the substrate, selectively influences the geometry of LeuT. In particular, the occupation of each site Na1/Na2 has strong effects (in terms of changes in influence and/or sensitivity, as compared to the case without ions) in specific regions of LeuT, and the effects are different for simultaneous occupation. Our results strengthen the rationale and provide a conformational mechanism for a putative transport mechanism in which Na2 is necessary, but may not be sufficient, to initiate and stabilize extracellular substrate access to the binding pocket.
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.
NASA Astrophysics Data System (ADS)
Cristofano, Gerardo; Maiella, Giuseppe; Marotta, Vincenzo
We extend the construction of the effective conformal field theory for the Jain hierarchical fillings proposed in Ref. 1 to the description of a quantum Hall fluid at nonstandard fillings ν =(m)/(pm+2). The chiral primary fields are found by using a procedure which induces twisted boundary conditions on the m scalar fields; they appear as composite operators of a charged and neutral component. The neutral modes describe parafermions and contribute to the ground state wave function with a generalized Pfaffian term. Correlators of Ne electrons in the presence of quasi-hole excitations are explicitly given for m=2.
[Research in two-dimensional critical phenomena and conformal field theory]. Final report
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)
Camilleri, Jérémy; Mazurier, Jocelyne; Franck, Denis; Dudouet, Philippe; Latorzeff, Igor; Franceries, Xavier
2016-01-01
This work presents an original algorithm that converts the signal of an electronic portal imaging device (EPID) into absorbed dose in water at the depth of maximum. The model includes a first image pre-processing step that accounts for the non-uniformity of the detector response but also for the perturbation of the signal due to backscatter radiation. Secondly, the image is converted into absorbed dose to water through a linear conversion function associated with a dose redistribution kernel. These two computation parameters were modelled by correlating the on-axis EPID signal with absorbed dose measurements obtained on square fields by using an ionization chamber placed in water at the depth of maximum dose. The accuracy of the algorithm was assessed by comparing the dose determined from the EPID signal with the dose derived by the treatment planning system (TPS) using the ϒ-index. These comparisons were performed on 8 conformal radiotherapy treatment fields (3DCRT) and 18 modulated fields (IMRT). For a dose difference and a distance-to-agreement set to 3% of the maximum dose and 2 mm respectively, the mean percentage of points with a ϒ-value less than or equal to 1 was 99.8% ± 0.1% for 3DCRT fields and 96.8% ± 2.7% for IMRT fields. Moreover, the mean gamma values were always less than 0.5 whatever the treatment technique. These results confirm that our algorithm is an accurate and suitable tool for clinical use in a context of IMRT quality assurance programmes. Copyright © 2015 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.
Impurity migration with RF sheath and ELMs perturbed electric field in tokamak
NASA Astrophysics Data System (ADS)
Gui, Bin; Xiao, Xiaotao; Tang, Tengfei; Xu, Xueqiao
2016-10-01
In radio frequency (RF) experiments, impurity generation and transport are important due to the phenomenon of RF enhanced impurity generation. In BOUT + + framework, the equilibrium radial electric field with RF sheath boundary condition on the limiter or the divertor surface is self-consistently calculated by using a two-field model. Based on this self-consistent calculation, it is found the positive radial electric field forms in the SOL region which qualitatively agrees with the experimental on the TEXTOR. The test particle module is developed in BOUT + + framework to simulate both turbulence and neoclassical physics in realistic geometry. Firstly, the drift orbit is calculated in cylinder coordinates due to singularity of x-point in flux coordinate. The turbulence transport of impurity generated from hot spot of RF limiter is simulated by random walk model. The numerical results show that less impurities will migrate into core and divertor region, more impurities migrate into nearby SOL boundary when turbulence transport enhanced. Then the effect of RF sheath potential on impurity migration will be simulated. Using the perturbed electric field from our BOUT + + nonlinear ELMs simulation, the transport of the impurities in different phase of ELMs are also discussed. USDOE by LLNL under DE-AC52-07NA27344.
Chaotic transport in Hamiltonian systems perturbed by a weak turbulent wave field
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.
From conformal field theory spectra to CMB multipoles in quantum gravity cosmology
Hamada, Ken-ji; Horata, Shinichi; Yukawa, Tetsuyuki
2010-04-15
We study the inflation process of the Universe based on the renormalizable quantum gravity formulated as a conformal field theory. We show that the power-law conformal field theory spectrum approaches that of the Harrison-Zel'dovich-Peebles-type as the amplitude of gravitational potential gradually reduces during the inflation. The non-Gaussanity parameter is preserved within an order of unity due to the diffeomorphism invariance. Sharp falloff of the angular power spectrum of cosmic microwave background at large scale is understood as a consequence of the existence of dynamical scale of the quantum gravity {Lambda}{sub QG}({approx_equal}10{sup 17} GeV). The angular power spectra are computed and compared with the WMAP5 and ACBAR data with a quality of {chi}{sup 2}/dof{approx_equal}1.1.
Anti-de Sitter Space from Optimization of Path Integrals in Conformal Field Theories
NASA Astrophysics Data System (ADS)
Caputa, Pawel; Kundu, Nilay; Miyaji, Masamichi; Takayanagi, Tadashi; Watanabe, Kento
2017-08-01
We introduce a new optimization procedure for Euclidean path integrals, which compute wave functionals in conformal field theories (CFTs). We optimize the background metric in the space on which the path integration is performed. Equivalently, this is interpreted as a position-dependent UV cutoff. For two-dimensional CFT vacua, we find the optimized metric is given by that of a hyperbolic space, and we interpret this as a continuous limit of the conjectured relation between tensor networks and Anti-de Sitter (AdS)/conformal field theory (CFT) correspondence. We confirm our procedure for excited states, the thermofield double state, the Sachdev-Ye-Kitaev model, and discuss its extension to higher-dimensional CFTs. We also show that when applied to reduced density matrices, it reproduces entanglement wedges and holographic entanglement entropy. We suggest that our optimization prescription is analogous to the estimation of computational complexity.
Yahia, Mouna Ben; Orhan, Emmanuelle; Beltrán, Armando; Masson, Olivier; Merle-Méjean, Thérèse; Mirgorodski, Andreï; Thomas, Philippe
2008-09-04
Density functional theory was used to estimate the third-order hypersusceptibility chi (3) of the alpha-TeO2 paratellurite (as a model structure for TeO2 glass) and the same value for alpha-SiO2 cristobalite (as a model structure for glassy silica). The attempt was made to gain a physical insight into the nature of the extraordinarily high hypersusceptibility of TeO2 glass. A finite field perturbation method implemented in the CRYSTAL code with the "sawtooth" approach was employed. The chi (3) values calculated for alpha-TeO2 were found to be of the same order as that measured for TeO2 glass and much higher than the values computed for alpha-SiO2 which, in turn, were close to that of glassy silica.
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.
Influence of Fock exchange in combined many-body perturbation and dynamical mean field theory
NASA Astrophysics Data System (ADS)
Ayral, Thomas; Biermann, Silke; Werner, Philipp; Boehnke, Lewin
2017-06-01
In electronic systems with long-range Coulomb interaction, the nonlocal Fock-exchange term has a band-widening effect. While this effect is included in combined many-body perturbation theory and dynamical mean field theory (DMFT) schemes, it is not taken into account in standard extended DMFT (EDMFT) calculations. Here, we include this instantaneous term in both approaches and investigate its effect on the phase diagram and dynamically screened interaction. We show that the largest deviations between previously presented EDMFT and G W +EDMFT results originate from the nonlocal Fock term, and that the quantitative differences are especially large in the strong-coupling limit. Furthermore, we show that the charge-ordering phase diagram obtained in G W +EDMFT methods for moderate interaction values is very similar to the one predicted by dual-boson methods that include the fermion-boson or four-point vertex.
Crossing symmetry and modular invariance in conformal field theory and S duality in gauge theory
Nanopoulos, Dimitri V.; Xie, Dan
2009-11-15
In this paper, we explore the relation between crossing symmetry and modular invariance in conformal field theory and S duality in gauge theory. It is shown that partition functions of different S dual theories of N=2 SU(2) gauge theory with four fundamentals can be derived from the crossing symmetry of the Liouville four-point function. We also show that the partition function of N=4 SU(2) gauge theory can be derived from the Liouville partition function on torus.
Viscous plasma evolution from gravity using anti-de sitter/conformal-field-theory correspondence.
Janik, Romuald A
2007-01-12
We analyze the anti-de Sitter/conformal-field-theory dual geometry of an expanding boost-invariant plasma. We show that the requirement of nonsingularity of the dual geometry for leading and subasymptotic times predicts, without any further assumptions about gauge theory dynamics, hydrodynamic expansion of the plasma with viscosity coefficient exactly matching the one obtained earlier in the static case by Policastro, Son, and Starinets.
1984-09-01
A conformal transformation formula using Riemann-Stieltjes integrals is derived for use with problems involving the interaction between a given finite-sized geometry and a known far field. The derivative of this transformation is non-singular in the domain considered and tends to one at infinity. A formula is derived for transformation from the unit circle to the exterior of an arbitrarily given continuous curve with bounded variation . A special case of the transformation is very similar
An advection-diffusion model for cross-field runaway electron transport in perturbed magnetic fields
NASA Astrophysics Data System (ADS)
Särkimäki, Konsta; Hirvijoki, Eero; Decker, Joan; Varje, Jari; Kurki-Suonio, Taina
2016-12-01
Disruption-generated runaway electrons (RE) present an outstanding issue for ITER. The predictive computational studies of RE generation rely on orbit-averaged computations and, as such, they lack the effects from the magnetic field stochasticity. Since stochasticity is naturally present in post-disruption plasma, and externally induced stochastization offers a prominent mechanism to mitigate RE avalanche, we present an advection-diffusion model that can be used to couple an orbit-following code to an orbit-averaged tool in order to capture the cross-field transport and to overcome the latter’s limitation. The transport coefficients are evaluated via a Monte Carlo method. We show that the diffusion coefficient differs significantly from the well-known Rechester-Rosenbluth result. We also demonstrate the importance of including the advection: it has a two-fold role both in modelling transport barriers created by magnetic islands and in amplifying losses in regions where the islands are not present.
Identification of transmissivity fields using a Bayesian strategy and perturbative approach
NASA Astrophysics Data System (ADS)
Zanini, Andrea; Tanda, Maria Giovanna; Woodbury, Allan D.
2017-10-01
The paper deals with the crucial problem of the groundwater parameter estimation that is the basis for efficient modeling and reclamation activities. A hierarchical Bayesian approach is developed: it uses the Akaike's Bayesian Information Criteria in order to estimate the hyperparameters (related to the covariance model chosen) and to quantify the unknown noise variance. The transmissivity identification proceeds in two steps: the first, called empirical Bayesian interpolation, uses Y* (Y = lnT) observations to interpolate Y values on a specified grid; the second, called empirical Bayesian update, improve the previous Y estimate through the addition of hydraulic head observations. The relationship between the head and the lnT has been linearized through a perturbative solution of the flow equation. In order to test the proposed approach, synthetic aquifers from literature have been considered. The aquifers in question contain a variety of boundary conditions (both Dirichelet and Neuman type) and scales of heterogeneities (σY2 = 1.0 and σY2 = 5.3). The estimated transmissivity fields were compared to the true one. The joint use of Y* and head measurements improves the estimation of Y considering both degrees of heterogeneity. Even if the variance of the strong transmissivity field can be considered high for the application of the perturbative approach, the results show the same order of approximation of the non-linear methods proposed in literature. The procedure allows to compute the posterior probability distribution of the target quantities and to quantify the uncertainty in the model prediction. Bayesian updating has advantages related both to the Monte-Carlo (MC) and non-MC approaches. In fact, as the MC methods, Bayesian updating allows computing the direct posterior probability distribution of the target quantities and as non-MC methods it has computational times in the order of seconds.
Massless conformal fields, AdS(d+1)/CFTd higher spin algebras and their deformations
Fernando, Sudarshan; Gunaydin, Murat
2016-02-04
Here, we extend our earlier work on the minimal unitary representation of SO(d, 2)and its deformations for d=4, 5and 6to arbitrary dimensions d. We show that there is a one-to-one correspondence between the minrep of SO(d, 2)and its deformations and massless conformal fields in Minkowskian spacetimes in ddimensions. The minrep describes a massless conformal scalar field, and its deformations describe massless conformal fields of higher spin. The generators of Joseph ideal vanish identically as operators for the quasiconformal realization of the minrep, and its enveloping algebra yields directly the standard bosonic AdS(d+1)/CFTd higher spin algebra. For deformed minreps the generatorsmore » of certain deformations of Joseph ideal vanish as operators and their enveloping algebras lead to deformations of the standard bosonic higher spin algebra. In odd dimensions there is a unique deformation of the higher spin algebra corresponding to the spinor singleton. In even dimensions one finds infinitely many deformations of the higher spin algebra labelled by the eigenvalues of Casimir operator of the little group SO(d–2)for massless representations.« less
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.
Tellgren, Erik I; Fliegl, Heike
2013-10-28
In the present study a non-perturbative approach to ab initio calculations of molecules in strong, linearly varying, magnetic fields is developed. The use of London atomic orbitals (LAOs) for non-uniform magnetic fields is discussed and the standard rationale of gauge-origin invariance is generalized to invariance under arbitrary constant shifts of the magnetic vector potential. Our approach is applied to study magnetically induced anapole moments (or toroidal moments) and the related anapole susceptibilities for a test set of chiral and nonchiral molecules. For the first time numerical anapole moments are accessible on an ab initio level of theory. Our results show that the use of London atomic orbitals dramatically improves the basis set convergence also for magnetic properties related to non-uniform magnetic fields, at the cost that the Hellmann-Feynman theorem does not apply for a finite LAO basis set. It is shown that the mixed anapole susceptibility can be related to chirality, since its trace vanishes for an achiral molecule.
NASA Astrophysics Data System (ADS)
Täuber, Uwe C.
2013-03-01
Field theory tools are applied to analytically study fluctuation and correlation effects in spatially extended stochastic predator-prey systems. In the mean-field rate equation approximation, the classic Lotka-Volterra model is characterized by neutral cycles in phase space, describing undamped oscillations for both predator and prey populations. In contrast, Monte Carlo simulations for stochastic two-species predator-prey reaction systems on regular lattices display complex spatio-temporal structures associated with persistent erratic population oscillations. The Doi-Peliti path integral representation of the master equation for stochastic particle interaction models is utilized to arrive at a field theory action for spatial Lotka-Volterra models in the continuum limit. In the species coexistence phase, a perturbation expansion with respect to the nonlinear predation rate is employed to demonstrate that spatial degrees of freedom and stochastic noise induce instabilities toward structure formation, and to compute the fluctuation corrections for the oscillation frequency and diffusion coefficient. The drastic downward renormalization of the frequency and the enhanced diffusivity are in excellent qualitative agreement with Monte Carlo simulation data.
Scale invariance vs conformal invariance
NASA Astrophysics Data System (ADS)
Nakayama, Yu
2015-03-01
In this review article, we discuss the distinction and possible equivalence between scale invariance and conformal invariance in relativistic quantum field theories. Under some technical assumptions, we can prove that scale invariant quantum field theories in d = 2 space-time dimensions necessarily possess the enhanced conformal symmetry. The use of the conformal symmetry is well appreciated in the literature, but the fact that all the scale invariant phenomena in d = 2 space-time dimensions enjoy the conformal property relies on the deep structure of the renormalization group. The outstanding question is whether this feature is specific to d = 2 space-time dimensions or it holds in higher dimensions, too. As of January 2014, our consensus is that there is no known example of scale invariant but non-conformal field theories in d = 4 space-time dimensions under the assumptions of (1) unitarity, (2) Poincaré invariance (causality), (3) discrete spectrum in scaling dimensions, (4) existence of scale current and (5) unbroken scale invariance in the vacuum. We have a perturbative proof of the enhancement of conformal invariance from scale invariance based on the higher dimensional analogue of Zamolodchikov's c-theorem, but the non-perturbative proof is yet to come. As a reference we have tried to collect as many interesting examples of scale invariance in relativistic quantum field theories as possible in this article. We give a complementary holographic argument based on the energy-condition of the gravitational system and the space-time diffeomorphism in order to support the claim of the symmetry enhancement. We believe that the possible enhancement of conformal invariance from scale invariance reveals the sublime nature of the renormalization group and space-time with holography. This review is based on a lecture note on scale invariance vs conformal invariance, on which the author gave lectures at Taiwan Central University for the 5th Taiwan School on Strings and
Pesendorfer, Mario B.; Gunhold, Tina; Schiel, Nicola; Souto, Antonio; Huber, Ludwig; Range, Friederike
2009-01-01
Background Social conformity is a cornerstone of human culture because it accelerates and maintains the spread of behaviour within a group. Few empirical studies have investigated the role of social conformity in the maintenance of traditions despite an increasing body of literature on the formation of behavioural patterns in non-human animals. The current report presents a field experiment with free-ranging marmosets (Callithrix jacchus) which investigated whether social conformity is necessary for the maintenance of behavioural patterns within groups or whether individual effects such as habit formation would suffice. Methods Using a two-action apparatus, we established alternative behavioural patterns in six family groups composed of 36 individuals. These groups experienced only one technique during a training phase and were thereafter tested with two techniques available. The monkeys reliably maintained the trained method over a period of three weeks, despite discovering the alternative technique. Three additional groups were given the same number of sessions, but those 21 individuals could freely choose the method to obtain a reward. In these control groups, an overall bias towards one of the two methods was observed, but animals with a different preference did not adjust towards the group norm. Thirteen of the fifteen animals that discovered both techniques remained with the action with which they were initially successful, independent of the group preference and the type of action (Binomial test: exp. proportion: 0.5, p<0.01). Conclusions The results indicate that the maintenance of behavioural patterns within groups 1) could be explained by the first rewarded manipulation and subsequent habit formation and 2) do not require social conformity as a mechanism. After an initial spread of a behaviour throughout a group, this mechanism may lead to a superficial appearance of conformity without the involvement of such a socially and cognitively complex mechanism
NASA Astrophysics Data System (ADS)
Ozgun, Ozlem; Kuzuoglu, Mustafa
2007-12-01
In the numerical solution of some boundary value problems by the finite element method (FEM), the unbounded domain must be truncated by an artificial absorbing boundary or layer to have a bounded computational domain. The perfectly matched layer (PML) approach is based on the truncation of the computational domain by a reflectionless artificial layer which absorbs outgoing waves regardless of their frequency and angle of incidence. In this paper, we present the near-field numerical performance analysis of our new PML approach, which we call as locally-conformal PML, using Monte Carlo simulations. The locally-conformal PML method is an easily implementable conformal PML implementation, to the problem of mesh truncation in the FEM. The most distinguished feature of the method is its simplicity and flexibility to design conformal PMLs over challenging geometries, especially those with curvature discontinuities, in a straightforward way without using artificial absorbers. The method is based on a special complex coordinate transformation which is 'locally-defined' for each point inside the PML region. The method can be implemented in an existing FEM software by just replacing the nodal coordinates inside the PML region by their complex counterparts obtained via complex coordinate transformation. We first introduce the analytical derivation of the locally-conformal PML method for the FEM solution of the two-dimensional scalar Helmholtz equation arising in the mathematical modeling of various steady-state (or, time-harmonic) wave phenomena. Then, we carry out its numerical performance analysis by means of some Monte Carlo simulations which consider both the problem of constructing the two-dimensional Green's function, and some specific cases of electromagnetic scattering.
Cosmological perturbations and the Weinberg theorem
Akhshik, Mohammad; Firouzjahi, Hassan; Jazayeri, Sadra E-mail: firouz@ipm.ir
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.
Perturbation theory, effective field theory, and oscillations in the power spectrum
Vlah, Zvonimir; Seljak, Uroš; Chu, Man Yat; Feng, Yu E-mail: useljak@berkeley.edu E-mail: yfeng1@berkeley.edu
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[−k{sup 2}Σ{sup 2}(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.
Force field-based conformational searches: efficiency and performance for peptide receptor complexes
NASA Astrophysics Data System (ADS)
Grebner, Christoph; Niebling, Stephan; Schmuck, Carsten; Schlücker, Sebastian; Engels, Bernd
2013-09-01
Conformational search using force field methods on complex biomolecular systems is a key factor in understanding molecular and structural properties. The reliability of such investigations strongly depends on the efficiency of the conformational search algorithm as well as the accuracy of the employed force field. In the present work we compared the performance of two different approaches: the Monte-Carlo multiple minimum/low mode sampling (MCMM/LM), in combination with the OPLS2005 (MCMM/LM//OPLS2005), and Tabu-Search combined with Basin Hopping (TS/BH), employing the original OPLS-AA implementation proposed by Jorgensen (TS/BH//OPLS-AA). We investigated their performance in locating energetically low-lying structures and the efficiency in scanning the conformational phase space of non-covalently bonded complexes. As test systems we employed complexes of the artificial peptide receptor CBS-KKF with four different tetrapeptide ligands. The reliability and the accuracy of both approaches were examined by re-optimising all low-energy structures employing density functional theory with empirical dispersion correction in combination with triple zeta basis sets. Solvent effects were mimicked by a continuum solvent model. In all the four-test systems, the TS/BH//OPLS-AA approach yielded structures that are much lower in energy after the DFT optimisation. Additionally, it provided many low-lying structures that were not identified by the MCMM/LM//OPLS2005 approach.
NASA Astrophysics Data System (ADS)
Nakayama, Yu
2017-02-01
We show that 11-dimensional supergravity in Euclidean signature admits an exact classical solution with isometry corresponding to a three-dimensional scale-invariant field theory without conformal invariance. We also construct the holographic renormalization group flow that connects the known UV conformal fixed point and the new scale-invariant but not conformal fixed point. In view of holography, the existence of such classical solutions suggests that the topologically twisted M2-brane gauge theory possesses a scale-invariant but not conformal phase.
Modelling of plasma response to 3D external magnetic field perturbations in EAST
NASA Astrophysics Data System (ADS)
Yang, Xu; Sun, Youwen; Liu, Yueqiang; Gu, Shuai; Liu, Yue; Wang, Huihui; Zhou, Lina; Guo, Wenfeng
2016-11-01
Sustained mitigation and/or suppression of type-I edge localized modes (ELMs) has been achieved in EAST high-confinement plasmas, utilizing the resonant magnetic perturbation (RMP) fields produced by two rows of magnetic coils located just inside the vacuum vessel. Systematic toroidal modelling of the plasma response to these RMP fields with various coil configurations (with dominant toroidal mode number n = 1, 2, 3, 4) in EAST is, for the first time, carried out by using the MARS-F code (Liu et al 2000 Phys. Plasmas 7 3681), with results reported here. In particular, the plasma response is computed with varying coil phasing (the toroidal phase difference of the coil currents) between the upper and lower rows of coils, from 0 to 360°. Four figures of merit, constructed based on the MARS-F computations, are used to determine the optimal coil phasing. The modelled results, taking into account the plasma response, agree well with the experimental observations in terms of the coil phasing for both the mitigated and the suppressed ELM cases in EAST experiments. This study provides a crucial confirmation of the role of the plasma edge peeling response in ELM control, complementing similar studies carried out for other tokamak devices.
NASA Astrophysics Data System (ADS)
Park, G.; Chang, C. S.; Joseph, I.; Moyer, R. A.
2010-10-01
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.
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.
Free energy of mean-field spin-glass models: Evolution operator and perturbation expansion
NASA Astrophysics Data System (ADS)
Janiš, V.; Kauch, A.; Klíč, A.
2013-02-01
The full mean-field solution of spin glass models with a continuous order-parameter function is not directly available and approximate schemes must be used to assess its properties. One of the authors recently proposed a representation of the free energy generating this solution via an evolution operator parametrized by attainable values of overlap of magnetizations between different states. Here, we introduce a perturbation expansion for the evolution operator that we use to derive all thermodynamic characteristics via the standard methods of statistical mechanics. We obtain a generic scheme for an approximate calculation of physical quantities of different mean-field spin-glass models at all temperatures. The small expansion parameter is a difference between the continuous order-parameter function and the corresponding order parameter from the solution with one level of replica-symmetry breaking. The first correction beyond the approximation with one level of replica-symmetry breaking is explicitly evaluated in the glassy phase of the Sherrington-Kirkpatrick model.
On gl2|2 with hat(2)k Current Superalgebra and Twisted Conformal Field Theory
NASA Astrophysics Data System (ADS)
Ding, Xiang-Mao; Wang, Gui-Dong; Wang, Shi-Kun
2007-01-01
Motivated by the recently discovered hidden symmetry of the type IIB Green-Schwarz superstring on certain background, the non-semisimple Kac-Moody twisted superalgebra gl2|2 with hat(2)k is investigated by means of the vector coherent state method and boson-fermion realization. The free field realization of the twisted current superalgebra at general level k is constructed. The corresponding Conformal Field Theory (CFT) has zero central charge. According to the classification theory, this CFT is a nonunitary field theory. After projecting out a U(1) factor and an outer automorphism operator, we get the free field representation of psl2|2 with hat(2)k, which is the algebra of gl2|2 with hat(2)k modulo the Bbb Z4-outer automorphism, the CFT has central charge -2.
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
Hansen, Halvor S; Hünenberger, Philippe H
2011-04-30
This article presents a reoptimization of the GROMOS 53A6 force field for hexopyranose-based carbohydrates (nearly equivalent to 45A4 for pure carbohydrate systems) into a new version 56A(CARBO) (nearly equivalent to 53A6 for non-carbohydrate systems). This reoptimization was found necessary to repair a number of shortcomings of the 53A6 (45A4) parameter set and to extend the scope of the force field to properties that had not been included previously into the parameterization procedure. The new 56A(CARBO) force field is characterized by: (i) the formulation of systematic build-up rules for the automatic generation of force-field topologies over a large class of compounds including (but not restricted to) unfunctionalized polyhexopyranoses with arbritrary connectivities; (ii) the systematic use of enhanced sampling methods for inclusion of experimental thermodynamic data concerning slow or unphysical processes into the parameterization procedure; and (iii) an extensive validation against available experimental data in solution and, to a limited extent, theoretical (quantum-mechanical) data in the gas phase. At present, the 56A(CARBO) force field is restricted to compounds of the elements C, O, and H presenting single bonds only, no oxygen functions other than alcohol, ether, hemiacetal, or acetal, and no cyclic segments other than six-membered rings (separated by at least one intermediate atom). After calibration, this force field is shown to reproduce well the relative free energies of ring conformers, anomers, epimers, hydroxymethyl rotamers, and glycosidic linkage conformers. As a result, the 56A(CARBO) force field should be suitable for: (i) the characterization of the dynamics of pyranose ring conformational transitions (in simulations on the microsecond timescale); (ii) the investigation of systems where alternative ring conformations become significantly populated; (iii) the investigation of anomerization or epimerization in terms of free-energy differences
Effect of strong electric field on the conformational integrity of insulin.
Wang, Xianwei; Li, Yongxiu; He, Xiao; Chen, Shude; Zhang, John Z H
2014-10-02
A series of molecular dynamics (MD) simulations up to 1 μs for bovine insulin monomer in different external electric fields were carried out to study the effect of external electric field on conformational integrity of insulin. Our results show that the secondary structure of insulin is kept intact under the external electric field strength below 0.15 V/nm, but disruption of secondary structure is observed at 0.25 V/nm or higher electric field strength. Although the starting time of secondary structure disruption of insulin is not clearly correlated with the strength of the external electric field ranging between 0.15 and 0.60 V/nm, long time MD simulations demonstrate that the cumulative effect of exposure time under the electric field is a major cause for the damage of insulin's secondary structure. In addition, the strength of the external electric field has a significant impact on the lifetime of hydrogen bonds when it is higher than 0.60 V/nm. The fast evolution of some hydrogen bonds of bovine insulin in the presence of the 1.0 V/nm electric field shows that different microwaves could either speed up protein folding or destroy the secondary structure of globular proteins deponding on the intensity of the external electric field.
Enhancement of helium exhaust by resonant magnetic perturbation fields at LHD and TEXTOR
NASA Astrophysics Data System (ADS)
Schmitz, O.; Ida, K.; Kobayashi, M.; Bader, A.; Brezinsek, S.; Evans, T. E.; Funaba, H.; Goto, M.; Mitarai, O.; Morisaki, T.; Motojima, G.; Nakamura, Y.; Narushima, Y.; Nicolai, D.; Samm, U.; Tanaka, H.; Yamada, H.; Yoshinuma, M.; Xu, Y.; TEXTOR, the; LHD Experiment Groups
2016-10-01
The ability to exhaust helium as the fusion born plasma impurity is a critical requirement for burning plasmas. We demonstrate in this paper that resonant magnetic perturbation (RMP) fields can be used to actively manipulate helium exhaust characteristics. We present results from puff/pump studies at TEXTOR as example for a tokamak with a pumped limiter and from the Large Helical Device (LHD) with the closed helical divertor as example for a heliotron/stellarator device. For LHD, the effective helium confinement time τ p,\\text{He}\\ast is a factor of 7-8 higher in the low and high density regimes explored when compared to TEXTOR discharges. This is attributed to ion root impurity transport which is one particular impurity transport regime assessed experimentally at LHD and which facilitates helium penetration to the plasma core. However, when an edge magnetic island is induced by externally applied RMP fields, τ p,\\text{He}\\ast is decreased by up to 30% and hence τ p,\\text{He}\\ast values closer to those of TEXTOR can be established. The combination of TEXTOR and LHD results suggest that a magnetic island induced by the RMP field in the plasma source region is an important ingredient for improving helium exhaust. The reduction in τ p,\\text{He}\\ast seen is caused by a combination of improved helium exhaust due to an enhanced coupling to the pumping systems, increased outward transport and a reduced fueling efficiency for the helium injected and recycling from the wall elements.
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.
NASA Astrophysics Data System (ADS)
Yu, Pei; Han, Maoan
2013-04-01
In this paper, we show that a Z2-equivariant 3rd-order Hamiltonian planar vector fields with 3rd-order symmetric perturbations can have at least 10 limit cycles. The method combines the general perturbation to the vector field and the perturbation to the Hamiltonian function. The Melnikov function is evaluated near the center of vector field, as well as near homoclinic and heteroclinic orbits.
Supersymmetric moose models: An extra dimension from a broken deformed conformal field theory
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.
Pressure and Compressibility of Conformal Field Theories from the AdS/CFT Correspondence
NASA Astrophysics Data System (ADS)
Dolan, Brian
2016-05-01
The equation of state associated with ${\\cal N}=4$ supersymmetric Yang-Mills in 4 dimensions, for $SU(N)$ in the large $N$ limit, is investigated using the AdS/CFT correspondence. An asymptotically AdS black-hole on the gravity side provides a thermal background for the Yang-Mills theory on the boundary in which the cosmological constant is equivalent to a volume. The thermodynamic variable conjugate to the cosmological constant is a pressure and the $P-V$ diagram is studied. It is known that there is a critical point where the heat capacity diverges and this is reflected in the isothermal compressibility. Critical exponents are derived and found to be mean field in the large $N$ limit. The same analysis applied to 3 and 6 dimensional conformal field theories again yields mean field exponents associated with the compressibility at the critical point.
Conformal field theory approach to Abelian and non-Abelian quantum Hall quasielectrons.
Hansson, T H; Hermanns, M; Regnault, N; Viefers, S
2009-04-24
The quasiparticles in quantum Hall liquids carry fractional charge and obey fractional quantum statistics. Of particular recent interest are those with non-Abelian statistics, since their braiding properties could, in principle, be used for robust coding of quantum information. There is already a good theoretical understanding of quasiholes in both Abelian and non-Abelian quantum Hall states. Here we develop conformal field theory methods that allow for an equally precise description of quasielectrons and explicitly construct two- and four-quasielectron excitations of the non-Abelian Moore-Read state.
Tests of conformal field theory at the Yang-Lee singularity
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.
Relative entropy of excited states in conformal field theories of arbitrary dimensions
NASA Astrophysics Data System (ADS)
Sárosi, Gábor; Ugajin, Tomonori
2017-02-01
Extending our previous work, we study the relative entropy between the reduced density matrices obtained from globally excited states in conformal field theories of arbitrary dimensions. We find a general formula in the small subsystem size limit. When one of the states is the vacuum of the CFT, our result matches with the holographic entanglement entropy computations in the corresponding bulk geometries, including AdS black branes. We also discuss the first asymmetric part of the relative entropy and comment on some implications of the results on the distinguishability of black hole microstates in AdS/CFT.
The fully packed loop model as a non-rational W 3 conformal field theory
NASA Astrophysics Data System (ADS)
Dupic, T.; Estienne, B.; Ikhlef, Y.
2016-12-01
The fully packed loop (FPL) model is a statistical model related to the integrable {{U}q}≤ft({{\\widehat{sl}}3}\\right) vertex model. In this paper we study the continuum limit of the FPL. With the appropriate weight of non-contractible loops, we give evidence of an extended W 3 symmetry in the continuum. The partition function on the torus is calculated exactly, yielding new modular invariants of W 3 characters. The full conformal field theory spectrum is obtained, and is found to be in excellent agreement with exact diagonalisation.
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.
NASA Astrophysics Data System (ADS)
Neogy, D.; Paul, P.; Chattopadhyay, K. N.; Bisui, D.
2002-07-01
Magnetic susceptibility measurements on single crystals of dysprosium trifluoromethanesulfonate (DyTFMS) have been carried out from 300 K down to 13 K. The hexagonal crystal structure of DyTFMS renders the crystal uniaxial with the Kramers ion Dy 3+ occupying a site of C 3h symmetry. The principal magnetic susceptibilities, observed by us and the Friedberg group, over the wide range 300 to ˜1.0 K find an excellent theoretical simulation by the crystal field perturbed J-mixed eigenvectors with due consideration of the intermediate coupling effects. No ordering effects were noticed down to ˜13 K indicating the interionic interaction to be predominantly of the dipolar type which is consistent with the discovery of a ferromagnetic transition at T˜0.111 K by the Friedberg group. The g-values derived from other sources are reasonably accounted for. The thermal behavior of quadrupole splitting and that of electronic and nuclear heat capacities is also worked out.
Renormalized parameters and perturbation theory in dynamical mean-field theory for the Hubbard model
NASA Astrophysics Data System (ADS)
Hewson, A. C.
2016-11-01
We calculate the renormalized parameters for the quasiparticles and their interactions for the Hubbard model in the paramagnetic phase as deduced from the low-energy Fermi-liquid fixed point using the results of a numerical renormalization-group calculation (NRG) and dynamical mean-field theory (DMFT). Even in the low-density limit there is significant renormalization of the local quasiparticle interaction U ˜, in agreement with estimates based on the two-particle scattering theory of J. Kanamori [Prog. Theor. Phys. 30, 275 (1963), 10.1143/PTP.30.275]. On the approach to the Mott transition we find a finite ratio for U ˜/D ˜ , where 2 D ˜ is the renormalized bandwidth, which is independent of whether the transition is approached by increasing the on-site interaction U or on increasing the density to half filling. The leading ω2 term in the self-energy and the local dynamical spin and charge susceptibilities are calculated within the renormalized perturbation theory (RPT) and compared with the results calculated directly from the NRG-DMFT. We also suggest, more generally from the DMFT, how an approximate expression for the q ,ω spin susceptibility χ (q ,ω ) can be derived from repeated quasiparticle scattering with a local renormalized scattering vertex.
NASA Astrophysics Data System (ADS)
Gabis, I. P.; Troshichev, O. A.
2000-06-01
Influence of short-term changes in solar activity on baric (pressure) field perturbations is studied using such characteristics as the Sazonov index (IS), describing the intensity of meridional transfer, the Blinova index (IB), describing the intensity of zonal transfer, and `vorticity area index' (VAI) describing the tropospheric cyclonic perturbations. The epoch superposition method is used to reveal effects of the solar central meridian (CM) passage of active regions, the Forbush decreases (FD) in galactic cosmic rays, and the solar proton (SP) events. The results of the analysis show that influence of short-term changes in the solar activity on baric field perturbations is the most evident in the stratosphere (30 mbar-level). The meridional circulation in case of the FD and SP events begin to increase about 5-7 days before the key date, reaches maximum nearby the key date and decays after the key date. The meridional circulation in case of the solar CM passage of active regions starts to increase after the key date and reaches the maximum by 5-6 days. Fluctuations of baric field within periods of 5-7 days typical of meridional and zonal transfers in troposphere (500 mbar-level) are evidently connected with internal dynamics of the atmosphere, not with the effects of solar activity. VAI characterizing cyclonic activity in the troposphere, shows the striking correspondence to changes of the meridional circulation in the stratosphere. Comparison of changes in the stratospheric perturbations with behavior of the UV irradiance in course of the FD and SP events show their full correspondence at the initial stage of these processes. The conclusion is made that growth of baric perturbations observed in the stratosphere in associations with the FD and SP events before the key date is caused by the solar UV irradiance increase, whereas decay of the baric perturbations after the key date is related to direct influence of the solar energetic corpuscular fluxes on the
Measurement of the effect of electric field on lipid ion channel conformation
Osman, P.D.; Cornell, B. CSIRO, North Ryde, New South Wales )
1992-01-01
This presentation reports on results from a new technique for measuring conformational changes by solid state NMR, in lipid membranes and membrane spanning ion channels, in response to the direct application of electrical field. An apparatus for applying biphasic electric field pulses of up to 20 MV/m to samples of aligned lipids held in an NMR probe, together with methods for the improvement of field homogeneity, will be described. In particular it has been found possible to obtain aligned lipid bilayers of very high impedance by substituting anhydrous glycerol for water. Measurements have been carried out on cholestric liquid crystals, on dilauryl phosphatidylcholine (DLPC) and dioleoyl phosphatidylethanolamine (DOPE) and on melittin in DLPC. The interaction of electric fields with aligned bilayers and powdered samples of DLPC and DOPE will be described, showing elongation of vesicles in response to the field and showing electric field induced Lalpha to powder to Hexll conversion in DOPE. The effect of electric fields on melittin incorporated into aligned lipid bilayers of DLPC will also be reported.
NASA Astrophysics Data System (ADS)
Abd El-Salam, F. A.; Abd El-Bar, S. E.; Rassem, M.
2017-05-01
In this work, the perturbations in all orbital elements due to the motion of the charged satellites in the Earth's magnetic field using Lagrange's planetary equations are solved exactly. The geomagnetic and electric force components in terms of orbital elements in full analytic expressions are derived. Lagrange's planetary equations after substitution with the considered perturbations in Keplerian orbital elements are obtained. To solve the problem in full analytical way, some integrals by Ahmed (Astron. J. 107, 1900 (1994)) are utilized. The time rate of change of all orbital elements of the spacecraft are integrated and represented in matrix notations.
NASA Astrophysics Data System (ADS)
Cho, Gil Young; Shiozaki, Ken; Ryu, Shinsei; Ludwig, Andreas W. W.
2017-07-01
Quantum phase transitions out of a symmetry-protected topological (SPT) phase in (1 + 1) dimensions into an adjacent, topologically distinct SPT phase protected by the same symmetry or a trivial gapped phase, are typically described by a conformal field theory (CFT). At the same time, the low-lying entanglement spectrum of a gapped phase close to such a quantum critical point is known (Cho et al arXiv:1603.04016), very generally, to be universal and described by (gapless) boundary conformal field theory. Using this connection we show that symmetry properties of the boundary conditions in boundary CFT can be used to characterize the symmetry-protected degeneracies of the entanglement spectrum, a hallmark of non-trivial symmetry-protected topological phases. Specifically, we show that the relevant boundary CFT is the orbifold of the quantum critical point with respect to the symmetry group defining the SPT, and that the boundary states of this orbifold carry a quantum anomaly that determines the topological class of the SPT. We illustrate this connection using various characteristic examples such as the time-reversal breaking ‘Kitaev chain’ superconductor (symmetry class D), the Haldane phase, and the {Z}8 classification of interacting topological superconductors in symmetry class BDI in (1 + 1) dimensions.
ff14IDPs force field improving the conformation sampling of intrinsically disordered proteins.
Song, Dong; Wang, Wei; Ye, Wei; Ji, Dingjue; Luo, Ray; Chen, Hai-Feng
2017-01-01
Intrinsically disordered proteins are proteins which lack of specific tertiary structure and unable to fold spontaneously without the partner binding. These intrinsically disordered proteins are found to associate with various diseases, such as diabetes, cancer, and neurodegenerative diseases. However, current widely used force fields, such as ff99SB, ff14SB, OPLS/AA, and Charmm27, are insufficient in sampling the conformational characters of intrinsically disordered proteins. In this study, the CMAP method was used to correct the φ/ψ distributions of disorder-promoting amino acids. The simulation results show that the force filed parameters (ff14IDPs) can improve the φ/ψ distributions of the disorder-promoting amino acids, with RMSD less than 0.10% relative to the benchmark data of intrinsically disordered proteins. Further test suggests that the calculated secondary chemical shifts under ff14IDPs are in quantitative agreement with the data of NMR experiment for five tested systems. In addition, the simulation results show that ff14IDPs can still be used to model structural proteins, such as tested lysozyme and ubiquitin, with better performance in coil regions than the original general Amber force field ff14SB. These findings confirm that the newly developed Amber ff14IDPs is a robust model for improving the conformation sampling of intrinsically disordered proteins.
Indicators of conformal field theory: Entanglement entropy and multiple-point correlators
NASA Astrophysics Data System (ADS)
Patil, Pranay; Tang, Ying; Katz, Emanuel; Sandvik, Anders W.
2017-07-01
The entanglement entropy (EE) of quantum systems is often used as a test of low-energy descriptions by conformal field theory (CFT). Here we point out that this is not a reliable indicator, as the EE often shows the same behavior even when a CFT description is not correct (as long as the system is asymptotically scale-invariant). We use constraints on the scaling dimension given by the CFT with SU(2) symmetry to provide alternative tests with two- and four-point correlation functions, showing examples for quantum spin models in 1+1 dimensions. In the case of a critical amplitude-product state expressed in the valence-bond basis (where the amplitudes decay as a power law of the bond length and the wave function is the product of all bond amplitudes), we show that even though the EE exhibits the expected CFT behavior, there is no CFT description of this state. We provide numerical tests of the behavior predicted by CFT for the correlation functions in the critical transverse-field Ising chain and the J -Q spin chain, where the conformal structure is well understood. That behavior is not reproduced in the amplitude-product state.
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.
Noether symmetries, energy-momentum tensors, and conformal invariance in classical field theory
Pons, Josep M.
2011-01-15
In the framework of classical field theory, we first review the Noether theory of symmetries, with simple rederivations of its essential results, with special emphasis given to the Noether identities for gauge theories. With this baggage on board, we next discuss in detail, for Poincare invariant theories in flat spacetime, the differences between the Belinfante energy-momentum tensor and a family of Hilbert energy-momentum tensors. All these tensors coincide on shell but they split their duties in the following sense: Belinfante's tensor is the one to use in order to obtain the generators of Poincare symmetries and it is a basic ingredient of the generators of other eventual spacetime symmetries which may happen to exist. Instead, Hilbert tensors are the means to test whether a theory contains other spacetime symmetries beyond Poincare. We discuss at length the case of scale and conformal symmetry, of which we give some examples. We show, for Poincare invariant Lagrangians, that the realization of scale invariance selects a unique Hilbert tensor which allows for an easy test as to whether conformal invariance is also realized. Finally we make some basic remarks on metric generally covariant theories and classical field theory in a fixed curved background.
NASA Astrophysics Data System (ADS)
Krizanac, M.; Vedmedenko, E. Y.; Wiesendanger, R.
2017-01-01
We present a perturbative approach for the resonant tunnel splittings of an arbitrary effective single spin system. The Hamiltonian of such a system contains a uniaxial anisotropy, a transversal magnetic field and a second-order transversal anisotropy. Further, we investigate the influence of the transversal magnetic field on the energy splittings for higher integer quantum spins and we introduce an exact formula, which defines values of the transversal magnetic field, the transversal anisotropy and the uniaxial anisotropy where the contribution of the transversal magnetic field to the energy splitting is at least equal to the contribution of the transversal anisotropy.
Strong-coupling perturbation theory for the two-dimensional Bose-Hubbard model in a magnetic field
NASA Astrophysics Data System (ADS)
Niemeyer, M.; Freericks, J. K.; Monien, H.
1999-07-01
The Bose-Hubbard model in an external magnetic field is investigated with strong-coupling perturbation theory. The lowest-order secular equation leads to the problem of a charged particle moving on a lattice in the presence of a magnetic field, which was first treated by Hofstadter. We present phase diagrams for the two-dimensional square and triangular lattices, showing a change in shape of the phase lobes away from the well-known power-law behavior in zero magnetic field. Some qualitative agreement with experimental work on Josephson-junction arrays is found for the insulating phase behavior at small fields.
Shape Dependence of Holographic Rényi Entropy in Conformal Field Theories.
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.
Zgarbová, Marie; Jurečka, Petr; Banáš, Pavel; Havrila, Marek; Šponer, Jiří; Otyepka, Michal
2017-03-23
The sugar-phosphate backbone of RNA can exist in diverse rotameric substates, giving RNA molecules enormous conformational variability. The most frequent noncanonical backbone conformation in RNA is α/γ = t/t, which is derived from the canonical backbone by a crankshaft motion and largely preserves the standard geometry of the RNA duplex. A similar conformation also exists in DNA, where it has been extensively studied and shown to be involved in DNA-protein interactions. However, the function of the α/γ = t/t conformation in RNA is poorly understood. Here, we present molecular dynamics simulations of several prototypical RNA structures obtained from X-ray and NMR experiments, including canonical and mismatched RNA duplexes, UUCG and GAGA tetraloops, Loop E, the sarcin-ricin loop, a parallel guanine quadruplex, and a viral pseudoknot. The stability of various noncanonical α/γ backbone conformations was analyzed with two AMBER force fields, ff99bsc0χOL3 and ff99bsc0χOL3 with the recent εζOL1 and βOL1 corrections for DNA. Although some α/γ substates were stable with seemingly well-described equilibria, many were unstable in our simulations. Notably, the most frequent noncanonical conformer α/γ = t/t was unstable in both tested force fields. Possible reasons for this instability are discussed. Our work reveals a potentially important artifact in RNA force fields and highlights a need for further force field refinement.
Jiang, Fan; Han, Wei; Wu, Yun-Dong
2013-03-14
The local conformational (φ, ψ, χ) preferences of amino acid residues remain an active research area, which are important for the development of protein force fields. In this perspective article, we first summarize spectroscopic studies of alanine-based short peptides in aqueous solution. While most studies indicate a preference for the P(II) conformation in the unfolded state over α and β conformations, significant variations are also observed. A statistical analysis from various coil libraries of high-resolution protein structures is then summarized, which gives a more coherent view of the local conformational features. The φ, ψ, χ distributions of the 20 amino acids have been obtained from a protein coil library, considering both backbone and side-chain conformational preferences. The intrinsic side-chain χ(1) rotamer preference and χ(1)-dependent Ramachandran plot can be generally understood by combining the interaction of the side-chain Cγ/Oγ atom with two neighboring backbone peptide groups. Current all-atom force fields such as AMBER ff99sb-ILDN, ff03 and OPLS-AA/L do not reproduce these distributions well. A method has been developed by combining the φ, ψ plot of alanine with the influence of side-chain χ(1) rotamers to derive the local conformational features of various amino acids. It has been further applied to improve the OPLS-AA force field. The modified force field (OPLS-AA/C) reproduces experimental (3)J coupling constants for various short peptides quite well. It also better reproduces the temperature-dependence of the helix-coil transition for alanine-based peptides. The new force field can fold a series of peptides and proteins with various secondary structures to their experimental structures. MD simulations of several globular proteins using the improved force field give significantly less deviation (RMSD) to experimental structures. The results indicate that the local conformational features from coil libraries are valuable for
Non-perturbative effects in quantum field theory: QCD, supersymmetric QCD and axions
NASA Astrophysics Data System (ADS)
Wu, Weitao
In the study of non-perturbative effects in four dimenstional non-Abelian gauge theories, instantons have played an important conceptual role. However, their role in the quantitative understanding these theories has remained obscure. In the first part of this thesis, we revisit the question of whether or not one can perform reliable semiclassical QCD computation at zero temperature. We study correlation functions with no perturbative contributions, and organize the problem by means of the operator product expansion, establishing a precise criterion for the validity of semiclassical calculation. For N f > Nc, a systematic computation is possible; for Nf < Nc, it is not. Nf = Nc is a borderline case. As an application, we describe a test of QCD lattice gauge theory computations in the chiral limit. Supersymmetry has provided a tool with which to obtain a range of exact results in field theory and string theory. Arguably the first inkling that one could obtain such results was the work of Novikov, Shifman, Vainshtein, and Zakharov (NSVZ). They argued for two exact results in gauge theories using instanton computation. First, that one could compute certain correlation functions exactly at weak coupling, and extend the results to strong coupling; second, that one could obtain exact expressions for beta-functions. However, each of these results raised questions. As methods exploiting systematic weak coupling expansions and holomorphy were developed, it became clear that the strong coupling instanton computation was incorrect. This in turn called the exact beta-function into question. In the second part of this thesis, we will provide resolutions to both of these questions. First, we explain why the instanton computation in the pure supersymmetric gauge theory is not reliable, even at short distances. The semiclassical expansion about the instanton is purely formal; if infrared divergences appear, they spoil arguments based on holomorphy. For the question of the NSVZbeta
NASA Astrophysics Data System (ADS)
Jin, W.; Ding, Y. H.; Rao, B.; Hu, Q. M.; Jin, X. S.; Wang, N. C.; Zhang, X. Q.; Wang, Z. J.; Y Chen, Z.; Zhuang, G.; the J-TEXT Team
2013-03-01
The plasma response to externally applied perturbation fields is investigated on the J-TEXT tokamak using a set of static resonant magnetic perturbation (SRMP) coils. Several different experimental results are obtained including partial or complete suppression of the existing m/n = 2/1 tearing mode, mode locking or non-uniform magnetohydrodynamic (MHD) oscillations. These results depend sensitively on the tearing mode frequency and the amplitude of the perturbation field. It is found that mode locking is most likely to happen at a lower rotation frequency (< ˜5 kHz) and the threshold for mode locking has a linear relation with MHD frequency. However, complete suppression of the tearing mode happens in a region where the MHD frequencies are higher (˜6 kHz). The experimental observations are explained by numerical simulations based on reduced MHD equations. The error field contributes to an offset between the mode-locking thresholds for the two opposite spatial phases of the SRMP, through which the intrinsic error field of J-TEXT can be estimated.
Active control of Type-I Edge-Localized Modes with n=1 Perturbation Fields in the JET Tokamak
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.
Rotating black hole in asymptotic de Sitter space: Perturbation of the space-time with spin fields
Khanal, U.
1983-09-15
The Newman-Penrose formalism is used to work with gravitational, electromagnetic, and Dirac field perturbations of the Kerr--de Sitter space. It is shown that the resulting equations are separable, and the radial parts (for the massless fields) combine into a master equation resembling that of Teukolsky. This master equation includes the Teukolsky equation and the equation arising from the de Sitter--Schwarzschild universe, and can be reduced to these cases under appropriate limiting conditions. Finally, the radial parts of the electromagnetic and neutrino fields are transformed to the form of the one-dimensional barrier-penetration equation.
Multipoint correlators of conformal field theories: implications for quantum critical transport
NASA Astrophysics Data System (ADS)
Strack, Philipp; Chowdhury, Debanjan; Raju, Suvrat; Sachdev, Subir; Singh, Ajay
2013-03-01
We relate three-point correlators between the stress-energy tensor and conserved currents of conformal field theories (CFTs) in 2+1 dimensions to observables of quantum critical transport. We first compute the correlators in the large-flavor-number expansion of conformal gauge theories and then do the computation using holography. In the holographic approach, the correlators are computed from an effective action on 3+1 dimensional anti-de Sitter space (AdS4), and depend upon the co-efficient, γ, of a four-derivative term in the action. We find a precise match between the CFT and the holographic results, thus fixing the values of γ. The CFTs of free fermions and bosons take the values γ = 1 / 12 , - 1 / 12 respectively, and so saturate the bound | γ | <= 1 / 12 obtained earlier from the holographic theory; the correlator of the conserved gauge flux of U(1) gauge theories takes intermediate values of γ. The value of γ also controls the frequency dependence of the conductivity, and other properties of quantum-critical transport at non-zero temperatures. Our results for the values of γ lead to an appealing physical interpretation of particle-like or vortex-like transport near quantum phase transitions of interest in condensed matter physics.
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. Copyright © 2014 Elsevier B.V. All rights reserved.
Conformally-invariant scalar field with trace-free energy-momentum tensor in Robertson-Walker models
NASA Astrophysics Data System (ADS)
Singh, N. I.; Singh, N. B.
1992-02-01
Exact solutions of Einstein's field equations for a conformally-invariant scalar field with trace-free energy-momentum tensor is presented for the Robertson-Walker models with K = + 1, - 1. The physical properties of the solution are also studied
Cola, Adriano; Farella, Isabella
2013-01-01
Schottky CdTe X-ray detectors exhibit excellent spectroscopic performance but suffer from instabilities. Hence it is of extreme relevance to investigate their electrical properties. A systematic study of the electric field distribution and the current flowing in such detectors under optical perturbations is presented here. The detector response is explored by varying experimental parameters, such as voltage, temperature, and radiation wavelength. The strongest perturbation is observed under 850 nm irradiation, bulk carrier recombination becoming effective there. Cathode and anode irradiations evidence the crucial role of the contacts, the cathode being Ohmic and the anode blocking. In particular, under irradiation of the cathode, charge injection occurs and peculiar kinks, typical of trap filling, are observed both in the current-voltage characteristic and during transients. The simultaneous access to the electric field and the current highlights the correlation between free and fixed charges, and unveils carrier transport/collection mechanisms otherwise hidden. PMID:23881140
Application of Fourth Order Vibrational Perturbation Theory with Analytic Hartree-Fock Force Fields
NASA Astrophysics Data System (ADS)
Gong, Justin Z.; Matthews, Devin A.; Stanton, John F.
2014-06-01
Fourth-Order Rayleigh-Schrodinger Perturbation Theory (VPT4) is applied to a series of small molecules. The quality of results have been shown to be heavily dependent on the quality of the quintic and sextic force constants used and that numerical sextic force constants converge poorly and are unreliable for VPT4. Using analytic Hartree-Fock force constants, it is shown that these analytic higher-order force constants are comparable to corresponding force constants from numerical calculations at a higher level of theory. Calculations show that analytic Hartree-Fock sextic force constants are reliable and can provide good results with Fourth-Order Rayleigh-Schrodinger Perturbation Theory.
NASA Astrophysics Data System (ADS)
Gurarie, V.; Ludwig, A. W. W.
We examine two-dimensional conformal field theories (CFTs) at central charge c = 0. These arise typically in the description of critical systems with quenched disorder, but also in other contexts including dilute self-avoiding polymers and percolation. We show that such CFTs must in general possess, in addition to their stress energy tensor T(z), an extra field whose holomorphic part, t(z), has conformal weight two. The singular part of the Operator Product Expansion (OPE) between T(z) and t(z) is uniquely fixed up to a single number b, defining a new `anomaly' which is a characteristic of any c = 0 CFT, and which may be used to distinguish between different such CFTs. The extra field t(z) is not primary (unless b = 0), and is a so-called `logarithmic operator' except in special cases which include affine (Kač-Moody) Lie-super current algebras. The number b controls the question of whether Virasoro null-vectors arising at certain conformal weights contained in the c = 0 Kač table may be set to zero or not, in these nonunitary theories. This has, in the familiar manner, implications on the existence of differential equations satisfied by conformal blocks involving primary operators with Kač-table dimensions. It is shown that c = 0 theories where t(z) is logarithmic, contain, besides T and t, additional fields with conformal weight two. If the latter are a fermionic pair, the OPEs between the holomorphic parts of all these conformal weight-two operators are automatically covariant under a global U(1|1) supersymmetry. A full extension of the Virasoro algebra by the Laurent modes of these extra conformal weight-two fields, including t(z), remains an interesting question for future work.
Spherically-Symmetric Gravitational Fields in Conformal Gravity and Their Sources
NASA Astrophysics Data System (ADS)
Verbin, Yosef; Brihaye, Yves
Conformal Gravity1 (CG) was proposed as a possible alternative to Einstein gravity ("GR"), which may supply the proper framework for a solution to some of the most annoying problems of theoretical physics like those of the cosmological constant, the dark matter and the dark energy. It is based on the Weyl tensor Cκλμν such that the gravitational Lagrangian and the field equations are {L}_g = - 1/2αC_{κ λ μ ν } C^{κ λ μ ν }quad ; quad W_{μ ν } = {α}/{2}T_{μ ν } (1) where α is a dimensionless positive parameter, Tμν is the energy-momentum tensor and Bach tensor Wμν replaces the Einstein tensor of GR…
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.
Numerical tests of conjectures of conformal field theory for three-dimensional systems
NASA Astrophysics Data System (ADS)
Weigel, Martin; Janke, Wolfhard
1998-11-01
The concept of conformal field theory provides a general classification of statistical systems on two-dimensional geometries at the point of a continuous phase transition. Considering the finite-size scaling of certain special observables, one thus obtains not only the critical exponents but even the corresponding amplitudes of the divergences analytically. A first numerical analysis brought up the question whether analogous results can be obtained for those systems on three-dimensional manifolds. Using Monte Carlo simulations based on the Wolff single-cluster update algorithm we investigate the scaling properties of O(n) symmetric classical spin models on a three-dimensional, hyper-cylindrical geometry with a toroidal cross-section considering both periodic and antiperiodic boundary conditions. Studying the correlation lengths of the Ising, the XY, and the Heisenberg model, we find strong evidence for a scaling relation analogous to the two-dimensional case, but in contrast here for the systems with antiperiodic boundary conditions.
Out-of-time-ordered correlators and purity in rational conformal field theories
NASA Astrophysics Data System (ADS)
Caputa, Paweł; Numasawa, Tokiro; Veliz-Osorio, Alvaro
2016-11-01
In this paper we investigate measures of chaos and entanglement in rational conformal field theories in 1 + 1 dimensions. First, we derive a formula for the late time value of the out-of-time-ordered correlators for this class of theories. Our universal result can be expressed as a particular combination of the modular S-matrix elements known as anyon monodromy scalar. Next, in the explicit setup of an SUN Wess-Zumino-Witten model, we compare the late time behavior of the out-of-time-ordered correlators and the purity. Interestingly, in the large-c limit, the purity grows logarithmically as in holographic theories; in contrast, the out-of-time-ordered correlators remain, in general, nonvanishing.
Kaiser, Nathan K; Bruce, James E
2005-09-15
Ion motion in Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is complex and the subject of ongoing theoretical and experimental studies. Two predominant pathways for the loss of ICR signals are thought to include damping of cyclotron motion, in which ions lose kinetic energy and radially damp toward the center of the ICR cell, and dephasing of ion coherence, in which ions of like cyclotron frequency become distributed out of phase at similar cyclotron radii. Both mechanisms result in the loss of induced ion image current in FTICR-MS measurements and are normally inseparable during time-domain signal analysis. For conventional ICR measurements which take advantage of ion ensembles, maximization of the ion population size and density can produce the desired effect of increasing phase coherence of ions during cyclotron motion. However, this approach also presents the risk of coalescence of ion packets of similar frequencies. In general, ICR researchers in the past have lacked the tools necessary to distinguish or independently control dephasing and damping mechanisms for ICR signal loss. Nonetheless, the ability to impart greater phase coherence of ions in ICR measurements will allow significant advances in FTICR-MS research by improving the current understanding of ICR signal loss contributions of dephasing and damping of ion ensembles, increasing overall time-domain signal length, and possibly, resulting in more routine ultrahigh resolution measurements. The results presented here demonstrate the ability to employ a high density electron beam to perturb electric fields within the ICR cell during detection of cyclotron motion, in an approach we call electron-promoted ion coherence (EPIC). As such, EPIC reduces ICR signal degradation through loss of phase coherence, and much longer time-domain signals can be obtained. Our results demonstrate that time-domain signals can be extended by more than a factor of 4 with the implementation of EPIC, as
J. M. Canik; Lore, J. D.; Ahn, J. -W.; ...
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
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.
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.
Spin pair geometry revealed by high-field DEER in the presence of conformational distributions
NASA Astrophysics Data System (ADS)
Polyhach, Ye.; Godt, A.; Bauer, C.; Jeschke, G.
2007-03-01
Orientation selection on two nitroxide-labelled shape-persistent molecules is demonstrated by high-field pulsed electron-electron double resonance experiments at a frequency of 95 GHz with a commercial spectrometer. The experiments are performed with fixed observer and pump frequencies by variation of the magnetic field, so that the variation of both the dipolar frequencies and the modulation depths can be analyzed. By applying the deadtime-free four-pulse double electron-electron resonance (DEER) sequence, the lineshapes of the dipolar spectra are obtained. In the investigated linear biradical and equilateral triradical the nitroxide labels undergo restricted dynamics, so that their relative orientations are not fixed, but are correlated to some extent. In this situation, the general dependence of the dipolar spectra on the observer field can be satisfyingly modelled by simple geometrical models that involve only one rotational degree of freedom for the biradical and two rotational degrees of freedom for the triradical. A somewhat better agreement of the dipolar lineshapes for the biradical is obtained by simulations based on a molecular dynamics trajectory. For the triradical, small but significant deviations of the lineshape are observed with both models, indicating that the technique can reveal deficiencies in modelling of the conformational ensemble of a macromolecule.
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.
Perturbations of black p-branes
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.
Field-Theoretical Approach to Many-Body Perturbation Theory: Combining MBPT and QED
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.
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.
NASA Astrophysics Data System (ADS)
Ito, T.; Toi, K.; Matsunaga, G.; Isobe, M.; Nagaoka, K.; Takeuchi, M.; Akiyama, T.; Matsuoka, K.; Minami, T.; Nishimura, S.; Okamura, S.; Shimizu, A.; Suzuki, C.; Yoshimura, Y.; Takahashi, C.; Chs Experimental Group
2009-09-01
Stable toroidicity-induced Alfvén 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 ρ >0.7 (ρ 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 ρ <0.4. The damping rate of these stable TAEs derived from plasma responses to applied perturbations is fairly large, that is, ˜9% to ˜12% of the angular eigenfrequency. This large damping rate is thought to be dominantly caused by continuum damping and radiative damping.
Lin, Zhixiong; Oostenbrink, Chris; van Gunsteren, Wilfred F
2014-03-01
The method of one-step perturbation can be used to predict from a single molecular dynamics simulation the values of observable quantities as functions of variations in the parameters of the Hamiltonian or biomolecular force field used in the simulation. The method is used to predict violations of nuclear overhauser effect (NOE) distance bounds measured in nuclear magnetic resonance (NMR) experiments by atom-atom distances of the NOE atom pairs when varying force-field parameters. Predictions of NOE distance bound violations between different versions of the GROMOS force field for a hexa-β-peptide in solution show that the technique works for rather large force-field parameter changes as well as for very different NOE bound violation patterns. The effect of changing individual force-field parameters on the NOE distance bound violations of the β-peptide and an α-peptide was investigated too. One-step perturbation, which in this case is equivalent to reweighting configurations, constitutes an efficient technique to predict many values of different quantities from a single conformational ensemble for a particular system, which makes it a powerful force-field development technique that easily reduces the number of required separate simulations by an order of magnitude.
Tian, Mei-ling; Fang, Ting; Du, Mu-ying; Zhang, Fu-sheng
2016-04-01
To explore an efficient, safe, and speedy application of pulsed electric field (PEF) technology for enzymatic modification, effects of PEF treatment on the enzymatic activity, property and kinetic parameters of α-amylase were investigated. Conformational transitions were also studied with the aid of circular dichroism (CD) and fluorescence spectra. The maximum enzymatic activity of α-amylase was obtained under 15 kV/cm electric field intensity and 100 mL/min flow velocity PEF treatment, in which the enzymatic activity increased by 22.13 ± 1.14% compared with control. The activation effect could last for 18 h at 4 °C. PEF treatment could widen the range of optimum temperature for α-amylase, however, it barely exerted any effect on the optimum pH. On the other hand, α-amylase treated by PEF showed an increase of Vmax, t1/2 and ΔG, whereas a decrease of Km and k were observed. Furthermore, it can be observed from fluorescence and CD spectra that PEF treatment had increased the number of amino acid residues, especially that of tryptophan, on α-amylase surface with enhanced α-helices by 34.76% and decreased random coil by 12.04% on α-amylase when compared with that of untreated. These changes in structure had positive effect on enhancing α-amylase activity and property.
Sine-square deformation of solvable spin chains and conformal field theories
NASA Astrophysics Data System (ADS)
Katsura, Hosho
2012-03-01
We study solvable spin chains, one-dimensional massless Dirac fermions and conformal field theories (CFTs) with sine-square deformation (SSD), in which the Hamiltonian density is modulated by the function f(x) = sin 2(πx/ℓ), where x is the position and ℓ is the length of the system. For the XY chain and the transverse field Ising chain at criticality, it is shown that the ground state of an open system with SSD is identical to that of a uniform chain with periodic boundary conditions. The same holds for the massless Dirac fermions with SSD, corresponding to the continuum limit of the gapless XY chain. For general CFTs, we find that the Hamiltonian of a system with SSD has an expression in terms of the generators of the Virasoro algebra. This allows us to show that the vacuum state is an exact eigenstate of the sine-square deformed Hamiltonian. Furthermore, for a restricted class of CFTs associated with affine Lie (Kac-Moody) algebras, including c = 1 Gaussian CFT, we prove that the vacuum is an exact ground state of the deformed Hamiltonian. This explains why the SSD has succeeded in suppressing boundary effects in one-dimensional critical systems, as observed in previous numerical studies.
A field-space conformal-solution method: Binary vapor-liquid phase behavior
NASA Astrophysics Data System (ADS)
Storvick, T. S.; Fox, J. R.
1990-01-01
The field-space conformal solution method provides an entirely new thermodynamic framework for the description of fluid mixtures in terms of the properties of a pure reference fluid. The utility and performance of the method are examined in the special case of vapor-liquid equilibrium correlation for simple mixtures. This is one of several cases in which field-space methods have numerical or theoretical advantages over methods presently used in mixture property correlation; only properties along the vapor pressure curve of the purefluid reference system are required for a complete description of the mixture phase behavior. Vapor-liquid equilibrium data for three binary hydrocarbon mixtures, n-butane + n-pentane, n-butane + n-hexane, and n-butane + n-octane, are correlated with a simple implementation of the method having two independent mixture parameters. Two pure-fluid equations of state, a Peng-Robinson equation and a 32-constant modified Benedict-Webb-Rubin equation, are tested as reference systems. The effects of differences in the quality of the reference system and of a range of mixture component size ratios are examined.
Energy flow and fluctuations in non-equilibrium conformal field theory on star graphs
NASA Astrophysics Data System (ADS)
Doyon, Benjamin; Hoogeveen, Marianne; Bernard, Denis
2014-03-01
We consider non-equilibrium quantum steady states in conformal field theory (CFT) on star-graph configurations, with a particular, simple connection condition at the vertex of the graph. These steady states occur after a large time as a result of initially thermalizing the legs of the graph at different temperatures, and carry energy flows. Using purely Virasoro algebraic calculations we evaluate the exact scaled cumulant generating function for these flows. We show that this function satisfies a generalization of the usual non-equilibrium fluctuation relations. This extends results by two of the authors to the case of more than two legs. It also provides an alternative derivation centered on Virasoro algebra operators rather than local fields, hence an alternative regularization scheme, thus confirming the validity and universality of the scaled cumulant generating function. Our derivation shows how the usual Virasoro algebra leads, in large volumes, to a continuous-index Virasoro algebra for which we develop diagrammatic principles, which may be of interest in other non-equilibrium contexts as well. Finally, our results shed light on the Poisson-process interpretation of the long-time energy transfer in CFT.
Puwal, Steffan; Roth, Bradley J; Basser, Peter J
2017-04-01
One goal of MRI is to determine the myelin water fraction in neural tissue. One approach is to measure the reduction in T2 * arising from microscopic perturbations in the magnetic field caused by heterogeneities in the magnetic susceptibility of myelin. In this paper, analytic expressions for the induced magnetic field distribution are derived within and around an axon, assuming that the myelin susceptibility is anisotropic. Previous models considered the susceptibility to be piecewise continuous, whereas this model considers a sinusoidally varying susceptibility. Many conclusions are common in both models. When the magnetic field is applied perpendicular to the axon, the magnetic field in the intraaxonal space is uniformly perturbed, the magnetic field in the myelin sheath oscillates between the lipid and water layers, and the magnetic field in the extracellular space just outside the myelin sheath is heterogeneous. These field heterogeneities cause the spins to dephase, shortening T2 *. When the magnetic field is applied along the axon, the field is homogeneous within water-filled regions, including between lipid layers. Therefore the spins do not dephase and the magnetic susceptibility has no effect on T2 *. Generally, the response of an axon is given as the superposition of these two contributions. The sinusoidal model uses a different set of approximations compared with the piecewise model, so their common predictions indicate that the models are not too sensitive to the details of the myelin-water distribution. Other predictions, such as the sensitivity to water diffusion between myelin and water layers, may highlight differences between the two approaches. Copyright © 2016 John Wiley & Sons, Ltd.
NASA Astrophysics Data System (ADS)
Awad, Mervat El-Sayed
1988-10-01
A special perturbation technique of Encke type associated with the Kustaanheimo-Stiefel (KS) regularized variables is developed for satellite motions in the earth's gravitational field with axial symmetry. Its computational algorithm is of recursive nature and could be applied to any perturbed conic motion, whatever the number of the zonal harmonic coefficients may be. Applications of the algorithm are also included.
NASA Astrophysics Data System (ADS)
Shinohara, Kouji; Suzuki, Yasuhiro; Kim, Junghee; Kim, Jun Young; Jeon, Young Mu; Bierwage, Andreas; Rhee, Tongnyeol
2016-11-01
The fast ion dynamics and the associated heat load on the plasma facing components in the KSTAR tokamak were investigated with the orbit following Monte-Carlo (OFMC) code in several magnetic field configurations and realistic wall geometry. In particular, attention was paid to the effect of resonant magnetic perturbation (RMP) fields. Both the vacuum field approximation as well as the self-consistent field that includes the response of a stationary plasma were considered. In both cases, the magnetic perturbation (MP) is dominated by the toroidal mode number n = 1, but otherwise its structure is strongly affected by the plasma response. The loss of fast ions increased significantly when the MP field was applied. Most loss particles hit the poloidal limiter structure around the outer mid-plane on the low field side, but the distribution of heat loads across the three limiters varied with the form of the MP. Short-timescale loss of supposedly well-confined co-passing fast ions was also observed. These losses started within a few poloidal transits after the fast ion was born deep inside the plasma on the high-field side of the magnetic axis. In the configuration studied, these losses are facilitated by the combination of two factors: (i) the large magnetic drift of fast ions across a wide range of magnetic surfaces due to a low plasma current, and (ii) resonant interactions between the fast ions and magnetic islands that were induced inside the plasma by the external RMP field. These effects are expected to play an important role in present-day tokamaks.
Izdebski, Marek
2006-11-10
An analytical approach is presented for studying the convergence of the general Jacobi method applied to diagonalizing the second-rank tensors that describe the optical properties of a medium subjected to an external field. This approach utilizes the fact that the components of such tensors are usually given in field-free principal axes as power series in the field strength, neglecting terms beyond a chosen power of the field. It is shown that for a biaxial or uniaxial medium, the finite number of iterations, which guarantees exact reduction of all the initial terms up to the required power in the series expansions of all off-diagonal elements, can always be found. Moreover, a fixed sequence of rotations in the Jacobi algorithm can be predicted. These findings allow one to derive analytical formulas in noniterative form for a given highest order of the effects being considered and also to optimize numerical iterative diagonalization procedures. Formulas for eigenvalues and eigenvectors applicable to biaxial and uniaxial mediums perturbed by the linear and quadratic effects are presented. Illustrations are given of the electro-optic and piezo-optic effects for the point group 3m. Conditions for biaxial and uniaxial perturbation of a uniaxial crystal are discussed.
NASA Astrophysics Data System (ADS)
Noda, Isao
2014-07-01
Noteworthy experimental practices, which are advancing forward the frontiers of the field of two-dimensional (2D) correlation spectroscopy, are reviewed with the focus on various perturbation methods currently practiced to induce spectral changes, pertinent examples of applications in various fields, and types of analytical probes employed. Types of perturbation methods found in the published literature are very diverse, encompassing both dynamic and static effects. Although a sizable portion of publications report the use of dynamic perturbatuions, much greater number of studies employ static effect, especially that of temperature. Fields of applications covered by the literature are also very broad, ranging from fundamental research to practical applications in a number of physical, chemical and biological systems, such as synthetic polymers, composites and biomolecules. Aside from IR spectroscopy, which is the most commonly used tool, many other analytical probes are used in 2D correlation analysis. The ever expanding trend in depth, breadth and versatility of 2D correlation spectroscopy techniques and their broad applications all point to the robust and healthy state of the field.
Zhang, Lanyue; Ding, Dandan; Yang, Desen; Wang, Jia; Shi, Jie
2017-01-01
Spherical microphone arrays have been paid increasing attention for their ability to locate a sound source with arbitrary incident angle in three-dimensional space. Low-frequency sound sources are usually located by using spherical near-field acoustic holography. The reconstruction surface and holography surface are conformal surfaces in the conventional sound field transformation based on generalized Fourier transform. When the sound source is on the cylindrical surface, it is difficult to locate by using spherical surface conformal transform. The non-conformal sound field transformation by making a transfer matrix based on spherical harmonic wave decomposition is proposed in this paper, which can achieve the transformation of a spherical surface into a cylindrical surface by using spherical array data. The theoretical expressions of the proposed method are deduced, and the performance of the method is simulated. Moreover, the experiment of sound source localization by using a spherical array with randomly and uniformly distributed elements is carried out. Results show that the non-conformal surface sound field transformation from a spherical surface to a cylindrical surface is realized by using the proposed method. The localization deviation is around 0.01 m, and the resolution is around 0.3 m. The application of the spherical array is extended, and the localization ability of the spherical array is improved. PMID:28489065
Zhang, Lanyue; Ding, Dandan; Yang, Desen; Wang, Jia; Shi, Jie
2017-05-10
Spherical microphone arrays have been paid increasing attention for their ability to locate a sound source with arbitrary incident angle in three-dimensional space. Low-frequency sound sources are usually located by using spherical near-field acoustic holography. The reconstruction surface and holography surface are conformal surfaces in the conventional sound field transformation based on generalized Fourier transform. When the sound source is on the cylindrical surface, it is difficult to locate by using spherical surface conformal transform. The non-conformal sound field transformation by making a transfer matrix based on spherical harmonic wave decomposition is proposed in this paper, which can achieve the transformation of a spherical surface into a cylindrical surface by using spherical array data. The theoretical expressions of the proposed method are deduced, and the performance of the method is simulated. Moreover, the experiment of sound source localization by using a spherical array with randomly and uniformly distributed elements is carried out. Results show that the non-conformal surface sound field transformation from a spherical surface to a cylindrical surface is realized by using the proposed method. The localization deviation is around 0.01 m, and the resolution is around 0.3 m. The application of the spherical array is extended, and the localization ability of the spherical array is improved.
Bi-local holography in the SYK model: Perturbations
Jevicki, Antal; Suzuki, Kenta
2016-11-08
We continue the study of the Sachdev-Ye-Kitaev model in the Large N limit. Following our formulation in terms of bi-local collective fields with dynamical reparametrization symmetry, we perform perturbative calculations around the conformal IR point. As a result, these are based on an ε expansion which allows for analytical evaluation of correlators and finite temperature quantities.
High-gradient operators in perturbed Wess-Zumino-Witten field theories in two dimensions
NASA Astrophysics Data System (ADS)
Ryu, S.; Mudry, C.; Ludwig, A. W. W.; Furusaki, A.
2010-11-01
Many classes of non-linear sigma models (NL σMs) are known to contain composite operators with an arbitrary number 2 s of derivatives ("high-gradient operators") which appear to become strongly relevant within renormalization group (RG) calculations at one (or fixed higher) loop order, when the number 2 s of derivatives becomes large. This occurs at many conventional fixed points of NL σMs which are perturbatively accessible within the usual ɛ-expansion in d=2+ɛ dimensions. Since such operators are not prohibited from occurring in the action, they appear to threaten the very existence of such fixed points. At the same time, for NL σMs describing metal-insulator transitions of Anderson localization in electronic conductors, the strong RG-relevance of these operators has been previously related to statistical properties of the conductance of samples of large finite size ("conductance fluctuations"). In this paper, we analyze this question, not for perturbative RG treatments of NL σMs, but for two-dimensional Wess-Zumino-Witten (WZW) models at level k, perturbatively in the current-current interaction of the Noether current ("non-Abelian Thirring/Gross-Neveu models"). WZW models are special ("Principal Chiral") NL σMs on a Lie Group G with a WZW term at level k. In these models the role of high-gradient operators is played by homogeneous polynomials of order 2 s in the Noether currents, whose scaling dimensions we analyze. For the Lie Supergroup G=GL(2N|2N) and k=1, this corresponds to time-reversal invariant problems of Anderson localization in the so-called chiral symmetry classes, and the strength of the current-current interaction, a measure of the strength of disorder, is known to be completely marginal (for any k). We find that all high-gradient (polynomial) operators are, to one loop order, irrelevant or relevant depending on the sign of that interaction.
NASA Astrophysics Data System (ADS)
Thode, Aaron
2004-06-01
Semianalytic expressions are derived for the first-order derivative of a pressure field in a laterally homogeneous waveguide, with respect to an arbitrary three-dimensional refractive index perturbation in either the water column or ocean bottom. These expressions for the ``environmental derivative,'' derived using an adjoint method, require a three-dimensional spatial correlation between two Green's functions, weighted by an environmental parameter basis function, with the Green's functions expressed in terms of normal modes. When a particular set of orthogonal spatial basis functions is chosen, the three-dimensional spatial integral can be converted into a set of one-dimensional integrations over depth and azimuth. The use of the orthogonal basis permits environmental derivatives to be computed for an arbitrary sound-speed perturbation. To illustrate the formulas, a simple sensitivity study is presented that explores under what circumstances three-dimensional plane-wave and cylindrical perturbations produce non-negligible horizontal refraction effects, for a fixed source/receiver geometry. Other potential applications of these formulas include benchmarking three-dimensional propagation codes, and computing Cramer-Rao bounds for three-dimensional environmental parameter estimates, including internal wave components.
NASA Astrophysics Data System (ADS)
Singh, R.; Jhang, Hogun; Kim, Juhyung
2017-01-01
We study the impact of external magnetic perturbations on the stability of ballooning modes. A unique feature of our analysis is the two-step parametric process [Chaturvedi and Kaw, J. Geophys. Res. 81, 3257 (1976)], which enables us to calculate contributions from all the modes with high toroidal mode numbers. The analysis shows that the externally applied magnetic field perturbations can modify the linear dispersion characteristics of the ballooning mode. Specifically, the growth rate spectrum of the ballooning modes becomes broader in poloidal wavenumber (kθ) space, implying the generation of high-k fluctuations. The increase of high-k fluctuations (micro-turbulence) can lead to the mitigation of an edge localized mode crash by increasing turbulent transport in the pedestal. In addition to this, a new nonlinear instability is found even below the threshold of the ballooning mode instability when the amplitude of magnetic perturbation is sufficiently large (i.e., δB /B0≥1.0 ×10-4 ). A discussion is given of the implication of this new finding.
Bouchami, Jihene; Paranjape, M. B.
2008-08-15
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).] that the conformal symmetry could be quarantined to a sterile sector of the theory by choosing an appropriate field redefinition.
Theoretical model of gravitational perturbation of current collector axisymmetric flow field
NASA Astrophysics Data System (ADS)
Walker, John S.; Brown, Samuel H.; Sondergaard, Neal A.
1990-05-01
Some designs of liquid-metal current collectors in homopolar motors and generators are essentially rotating liquid-metal fluids in cylindrical channels with free surfaces and will, at critical rotational speeds, become unstable. An investigation at David Taylor Research Center is being performed to understand the role of gravity in modifying this ejection instability. Some gravitational effects can be theoretically treated by perturbation techniques on the axisymmetric base flow of the liquid metal. This leads to a modification of previously calculated critical-current-collector ejection values neglecting gravity effects. The purpose of this paper is to document the derivation of the mathematical model which determines the perturbation of the liquid-metal base flow due to gravitational effects. Since gravity is a small force compared with the centrifugal effects, the base flow solutions can be expanded in inverse powers of the Froude number and modified liquid-flow profiles can be determined as a function of the azimuthal angle. This model will be used in later work to theoretically study the effects of gravity on the ejection point of the current collector.
Theoretical model of gravitational perturbation of current collector axisymmetric flow field
NASA Astrophysics Data System (ADS)
Walker, John S.; Brown, Samuel H.; Sondergaard, Neal A.
1989-03-01
Some designs of liquid metal collectors in homopolar motors and generators are essentially rotating liquid metal fluids in cylindrical channels with free surfaces and will, at critical rotational speeds, become unstable. The role of gravity in modifying this ejection instability is investigated. Some gravitational effects can be theoretically treated by perturbation techniques on the axisymmetric base flow of the liquid metal. This leads to a modification of previously calculated critical current collector ejection values neglecting gravity effects. The derivation of the mathematical model which determines the perturbation of the liquid metal base flow due to gravitational effects is documented. Since gravity is a small force compared with the centrifugal effects, the base flow solutions can be expanded in inverse powers of the Froude number and modified liquid flow profiles can be determined as a function of the azimuthal angle. This model will be used in later work to theoretically study the effects of gravity on the ejection point of the current collector. A rederivation of the hydrodynamic instability threshold of a liquid metal current collector is presented.
Ramakrishnan, Raghunathan; Carrington, Tucker
2014-02-05
We have computed vibrational energy levels of difluorodioxirane (CF2O2). For the potential, a Taylor expansion in normal coordinates is used. The CCSD(T) and MP2 methods and correlation consistent basis sets of quadruple-zeta quality are used to determine the force constants. The vibrational Schrödinger equation was solved using both a variational method and second order perturbation theory. The Watson kinetic energy operator and a discrete variable representation were used with the DEWE (E. Mátyus, G. Czakó, B.T. Sutcliffe and A.G. Császár, J. Chem. Phys. 127 (2007) 084102) computer program to do the variational calculations. For the variational calculations, the average absolute deviation of fundamentals, with respect to experimental values, is less than 3 cm(-1). Perturbative results are almost as good. About 300 vibrational levels were computed. (16)O→(18)O isotopic shifts have also been calculated variationally for the lowest 75 vibrational energy levels and are compared to experimental results. Copyright © 2012 Elsevier B.V. All rights reserved.
Universal boundary entropies in conformal field theory: A quantum Monte Carlo study
NASA Astrophysics Data System (ADS)
Tang, Wei; Chen, Lei; Li, Wei; Xie, X. C.; Tu, Hong-Hao; Wang, Lei
2017-09-01
Recently, entropy corrections on nonorientable manifolds such as the Klein bottle are proposed as a universal characterization of critical systems with an emergent conformal field theory (CFT). We show that entropy correction on the Klein bottle can be interpreted as a boundary effect via transforming the Klein bottle into an orientable manifold with nonlocal boundary interactions. The interpretation reveals the conceptual connection of the Klein bottle entropy with the celebrated Affleck-Ludwig entropy in boundary CFT. We propose a generic scheme to extract these universal boundary entropies from quantum Monte Carlo calculation of partition function ratios in lattice models. Our numerical results on the Affleck-Ludwig entropy and Klein bottle entropy for the q -state quantum Potts chains with q =2 ,3 show excellent agreement with the CFT predictions. For the quantum Potts chain with q =4 , the Klein bottle entropy slightly deviates from the CFT prediction, which is possibly due to marginally irrelevant terms in the low-energy effective theory.
NASA Astrophysics Data System (ADS)
Dubail, J.; Santachiara, R.; Emig, T.
2017-03-01
Systems as diverse as binary mixtures and inclusions in biological membranes, and many more, can be described effectively by interacting spins. When the critical fluctuations in these systems are constrained by boundary conditions, critical Casimir forces (CCF) emerge. Here we analyze CCF between boundaries with alternating boundary conditions in two dimensions, employing conformal field theory (CFT). After presenting the concept of boundary changing operators, we specifically consider two different boundary configurations for a strip of critical Ising spins: (I) alternating equi-sized domains of up and down spins on both sides of the strip, with a possible lateral shift, and (II) alternating domains of up and down spins of different size on one side and homogeneously fixed spins on the other side of the strip. Asymptotic results for the CCF at small and large distances are derived. We introduce a novel modified Szegö formula for determinants of real antisymmetric block Toeplitz matrices to obtain the exact CCF and the corresponding scaling functions at all distances. We demonstrate the existence of a surface renormalization group flow between universal force amplitudes of different magnitude and sign. The Casimir force can vanish at a stable equilibrium position that can be controlled by parameters of the boundary conditions. Lateral Casimir forces assume a universal simple cosine form at large separations.
Parent Hamiltonians for lattice Halperin states from free-boson conformal field theories
NASA Astrophysics Data System (ADS)
Hackenbroich, Anna; Tu, Hong-Hao
2017-03-01
We introduce a family of many-body quantum states that describe interacting spin one-half hard-core particles with bosonic or fermionic statistics on arbitrary one- and two-dimensional lattices. The wave functions at lattice filling fraction ν = 2 / (2 m + 1) are derived from deformations of the Wess-Zumino-Witten model su (3)1 and are related to the (m + 1 , m + 1 , m) Halperin fractional quantum Hall states. We derive long-range SU(2) invariant parent Hamiltonians for these states which in two dimensions are chiral t-J-V models with additional three-body interaction terms. In one dimension we obtain a generalisation to open chains of a periodic inverse-square t-J-V model proposed in [25]. We observe that the gapless low-energy spectrum of this model and its open-boundary generalisation can be described by rapidity sets with the same generalised Pauli exclusion principle. A two-component compactified free boson conformal field theory is identified as the low-energy effective theory for the periodic inverse-square t-J-V model.
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.
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].
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.
Spectrum of the Wilson-Fisher conformal field theory on the torus
NASA Astrophysics Data System (ADS)
Whitsitt, Seth; Schuler, Michael; Henry, Louis-Paul; Läuchli, Andreas M.; Sachdev, Subir
2017-07-01
We study the finite-size spectrum of the O(N )-symmetric Wilson-Fisher conformal field theory (CFT) on the (d =2 )-spatial-dimension torus using the expansion in ɛ =3 -d . This is done by deriving a set of universal effective Hamiltonians describing fluctuations of the zero-momentum modes. The effective Hamiltonians take the form of N -dimensional quantum anharmonic oscillators, which are shown to be strongly coupled at the critical point for small ɛ . The low-energy spectrum is solved numerically for N =1 ,2 ,3 ,4 . Using exact diagonalization, we also numerically study explicit lattice models known to be in the O(2) and O(3) universality class, obtaining estimates of the low-lying critical spectrum. The analytic and numerical results show excellent agreement and the critical low-energy torus spectra are qualitatively different among the studied CFTs, identifying them as a useful fingerprint for detecting the universality class of a quantum critical point.
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. Copyright © 2014 Elsevier Ltd. All rights reserved.
NASA Astrophysics Data System (ADS)
Xiong, Ying; Chen, Lunjin; Xie, Lun; Fu, Suiyan; Xia, Zhiyang; Pu, Zuyin
2017-05-01
Dayside modulated relativistic electron's butterfly pitch angle distributions (PADs) from ˜200 keV to 2.6 MeV were observed by Van Allen Probe B at L = 5.3 on 15 November 2013. They were associated with localized magnetic dip driven by hot ring current ion (60-100 keV proton and 60-200 keV helium and oxygen) injections. We reproduce the electron's butterfly PADs at satellite's location using test particle simulation. The simulation results illustrate that a negative radial flux gradient contributes primarily to the formation of the modulated electron's butterfly PADs through inward transport due to the inductive electric field, while deceleration due to the inductive electric field and pitch angle change also makes in part contribution. We suggest that localized magnetic field perturbation, which is a frequent phenomenon in the magnetosphere during magnetic disturbances, is of great importance for creating electron's butterfly PADs in the Earth's radiation belts.
NASA Astrophysics Data System (ADS)
Xiong, Ying; Chen, Lunjin; Xie, Lun; Fu, Suiyan; Pu, Zuyin
2017-04-01
Dayside modulated relativistic electron's butterfly pitch angle distributions (PADs) from 200 keV to 2.6 MeV was observed by Van Allen Probe-B at L = 5.3 on November 15, 2013. They were associated with localized magnetic dip driven by hot ring current ion (60-100 keV protons and 60-200 keV oxygen) injections. We reproduce the electron's butterfly PADs at satellite's location using test particle simulation. The simulation results illustrate that negative radial flux gradient contributes primarily to the formation of the modulated electron's butterfly PADs through inward transport due to the inductive electric field, while deceleration due to the inductive electric field and pitch angle change make in part contribution. We suggest that localized magnetic field perturbation, which is a frequent phenomenon in the magnetosphere during magnetic disturbances, is of great importance for creating electron's butterfly PADs in the Earth's radiation belts.
NASA Astrophysics Data System (ADS)
Gillin, W. P.; Zhang, Sijie; Rolfe, N. J.; Desai, P.; Shakya, P.; Drew, A. J.; Kreouzis, T.
2010-11-01
The perturbation of the current transport in aluminum tris(8-hydroxyquinoline) (Alq3) -based organic light emitting diodes has been investigated as a function of magnetic field. The change in current, or organic magnetoresistance, with applied field has been fitted using two Lorentzian functions corresponding to polaron trapping by triplets and the interaction between polarons and triplets as suggested in the triplet polaron interaction model. The model has been applied to a number of devices with Alq3 thicknesses from 50 to 90 nm and with two different cathodes. In all cases the data could be fitted using just these two processes, the prefactors for which were found to scale linearly with the triplet population over 6 orders of magnitude. This work demonstrates that the magnitude and shape of the organic magnetoresistance can be predicted and illustrates the importance of magnetic field measurements as a tool for understanding the processes affecting current transport in organic devices.
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
2016-04-07
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.
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
2016-01-01
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 chromophore 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 is temporally and spatially related with 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 photoactive yellow protein by employing its E46Q mutant, 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 intermeidates and reveals that the smaller structural change in E46Q-PYP than in wt-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 wt-PYP. This finding provides a direct evidence of how the environmental change in the vicinity of the chromophore alters the conformational change of the entire protein matrix. PMID:26960811
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.
Kong, Liguo; Valeev, Edward F
2010-11-07
To reduce the basis set incompleteness of the complete-active-space self-consistent field (CASSCF) wave function and energy we develop a second-order perturbation correction due to single excitations to complete set of unoccupied states. Other than the one- and two-electron integrals, only one- and two-particle reduced density matrices are required to compute the correction, denoted as [2](S). Benchmark calculations on prototypical ground-state bond-breaking problems show that only the aug-cc-pVXZ basis is needed with the [2](S) correction to match the accuracy of CASSCF energies of the aug-cc-pV(X+1)Z quality.
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.
Series of (2+1)-dimensional stable self-dual interacting conformal field theories
NASA Astrophysics Data System (ADS)
Cheng, Meng; Xu, Cenke
2016-12-01
Using the duality between seemingly different (2+1)-dimensional [(2 +1 )d ] conformal field theories (CFT) proposed recently [D. T. Son, Phys. Rev. X 5, 031027 (2015), 10.1103/PhysRevX.5.031027; M. A. Metlitski and A. Vishwanath, Phys. Rev. B 93, 245151 (2016), 10.1103/PhysRevB.93.245151; C. Wang and T. Senthil, Phys. Rev. X 6, 011034 (2015), 10.1103/PhysRevX.6.011034; C. Wang and T. Senthil, Phys. Rev. X 5, 041031 (2015), 10.1103/PhysRevX.5.041031; C. Wang and T. Senthil, Phys. Rev. B 93, 085110 (2016), 10.1103/PhysRevB.93.085110; C. Xu and Y.-Z. You, Phys. Rev. B 92, 220416 (2015), 10.1103/PhysRevB.92.220416; D. F. Mross et al., Phys. Rev. Lett. 117, 016802 (2016), 10.1103/PhysRevLett.117.016802; A. Karch and D. Tong, arXiv:1606.01893; N. Seiberg et al., arXiv:1606.01989; P.-S. Hsin and N. Seiberg, arXiv:1607.07457], we study a series of (2 +1 )d stable self-dual interacting CFTs. These CFTs can be realized (for instance) on the boundary of the 3 d bosonic topological insulator protected by U(1) and time-reversal symmetry (T ), and they remain stable as long as these symmetries are preserved. When realized as a boundary system, these CFTs can be driven into anomalous fractional quantum Hall states once T is broken. We demonstrate that the newly proposed dualities allow us to study these CFTs quantitatively through a controlled calculation, without relying on a large flavor number of matter fields. We also propose a numerical test for our results, which would provide strong evidence for the originally proposed duality between Dirac fermion and QED.
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
NASA Astrophysics Data System (ADS)
Frauendiener, Jörg
2004-12-01
The notion of conformal infinity has a long history within the research in Einstein's theory of gravity. Today, "conformal infinity" is related to almost all other branches of research in general relativity, from quantisation procedures to abstract mathematical issues to numerical applications. This review article attempts to show how this concept gradually and inevitably evolved from physical issues, namely the need to understand gravitational radiation and isolated systems within the theory of gravitation, and how it lends itself very naturally to the solution of radiation problems in numerical relativity. The fundamental concept of null-infinity is introduced. Friedrich's regular conformal field equations are presented and various initial value problems for them are discussed. Finally, it is shown that the conformal field equations provide a very powerful method within numerical relativity to study global problems such as gravitational wave propagation and detection.
NASA Technical Reports Server (NTRS)
Ulaby, F. T.; Kouyate, F.; Fung, A. K.
1981-01-01
A backscatter model for a randomly perturbed periodic surface has been developed to explain backscatter measurements from a bare soil surface with row structure. It is assumed that the row-direction effect can be included by integrating the scattering coefficient due to the random roughness component over the underlying periodic component of the soil surface. It is found that the row-direction effect is strongly dependent upon the rate of change of this scattering coefficient with the local angle, and that the maximum difference between looking parallel and perpendicular to the row direction occurs around an incidence angle whose tangent is equal to the slope of the periodic surface at the inflection point.
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.
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.
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.
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.
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.
Cosmological magnetic field: a fossil of density perturbations in the early universe.
Ichiki, Kiyotomo; Takahashi, Keitaro; Ohno, Hiroshi; Hanayama, Hidekazu; Sugiyama, Naoshi
2006-02-10
The origin of the substantial magnetic fields that are found in galaxies and on even larger scales, such as in clusters of galaxies, is yet unclear. If the second-order couplings between photons and electrons are considered, then cosmological density fluctuations, which explain the large-scale structure of the universe, can also produce magnetic fields on cosmological scales before the epoch of recombination. By evaluating the power spectrum of these cosmological magnetic fields on a range of scales, we show here that magnetic fields of 10(-18.1) gauss are generated at a 1-megaparsec scale and can be even stronger at smaller scales (10(-14.1) gauss at 10 kiloparsecs). These fields are large enough to seed magnetic fields in galaxies and may therefore have affected primordial star formation in the early universe.
Character relations and replication identities in 2d Conformal Field Theory
NASA Astrophysics Data System (ADS)
Bantay, P.
2016-10-01
We study replication identities satisfied by conformal characters of a 2D CFT, providing a natural framework for a physics interpretation of the famous Hauptmodul property of Monstrous Moonshine, and illustrate the underlying ideas in simple cases.
Destruction of Invariant Surfaces and Magnetic Coordinates for Perturbed Magnetic Fields
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.
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.
NASA Astrophysics Data System (ADS)
Punjabi, Alkesh; Ali, Halima
2013-10-01
The symplectic mathematical maps in natural canonical coordinates for forward and backward integration of magnetic field lines in the DIII-D tokamak [Luxon, J.L.; Davis, L.E. Fusion Technol. 1985, 8, 441] are used to calculate the magnetic footprints and their associated parameters on the inboard and outboard collector plates from the low mn magnetic perturbation with and without internal topological noise and magnetic field errors. The Grad-Shafranov solver equilibrium fit (EFIT) results from the experimental data for the DIII-D shot 115467 at 3000 ms [Lao, L.; St John, H.; Peng, Q.; Ferron, J.; Strait, E.; Taylor, T.; Meyer, W.; Zhang, C.; You, K. Fusion Sci. Technol. 2005, 48, 968] is used to construct an analytic expression for the equilibrium Hamiltonian function for the field line trajectories. The equilibrium Hamiltonian accurately represents the magnetic geometry of the DIII-D. The inboard and outboard footprints consist of a single toroidally winding stripe. Noise and error fields do not change the topology of the footprints, and have a marginal effect on the size of the footprint. Noise and error fields reduce the fraction of poloidal flux connecting the plates, and at the same time enhance the connection length. Noise and error fields reduce the safety factor. Backward trajectories starting close to the X-point have high safety factor. The new approach of symplectic mathematical maps in natural canonical coordinates can give an accurate and realistic picture of footprint reflecting the unique magnetic geometry of device in physical space.
Most Typical 1∶2 Resonant Perturbation of the Hydrogen Atom by Weak Electric and Magnetic Fields
NASA Astrophysics Data System (ADS)
Efstathiou, K.; Lukina, O. V.; Sadovskií, D. A.
2008-12-01
We study a perturbation of the hydrogen atom by small homogeneous static electric and magnetic fields in a specific mutual alignment with angle approximately π/3 which results in the 1∶2 resonance of the linearized Keplerian n-shell approximation. The bifurcation diagram of the classical integrable approximation has for most such field configurations the same typical structure that we describe. The structure of the corresponding quantum energy spectrum, which we describe in detail, is in certain ways an analogue of the well-known degeneracy found by Herrick [Phys. Rev. A 26, 323 (1982)PLRAAN1050-294710.1103/PhysRevA.26.323] for the quadratic Zeeman effect.
Ansarihadipour, Hadi; Bayatiani, Mohamadreza
2016-01-01
Background Electromagnetic fields (EMF) are associated with oxidative stress, which is in turn associated with reactive oxygen species (ROS), anemia, and hypoxia. Objectives This study focused on the synergistic effects of lead ions and EMF on oxidative modifications in hemoglobin (Hb) and plasma proteins. Patients and Methods In this experimental study, the blood samples were obtained from age- and sex-matched healthy subjects at Arak University of Medical Sciences, Arak, Iran. The collected bloods were prepared as 55 samples and then divided into different groups for incubating with 0 to 100 uM of lead ions in 2 mT and 50 Hz of EMF for 120 minutes. The carbonyl group was determined to be an oxidative biomarker in plasma proteins. The ferric reducing ability of plasma (FRAP) was considered to be an antioxidant power of human plasma. The conformational changes in hemoglobin, met-Hb, and hemichrome were considered to be oxidative markers in red blood cells. To predict the factors affecting the oxyHb, the artificial neural network (MLP: 11,2,2,1) in SPSS software was applied. Results The test subjects showed increased concentrations of metHb (1.8 ± 0.19 vs. 1.36 ± 0.25) and hemichrome (6.01 ± 0.57) in relation to the control subjects. The decreased absorbance at 340 nm (0.88 ± 0.09 vs. 1.07 ± 0.08) demonstrated the reduced interaction between the globin chain and the heme ring. The decreased absorbance at 420 nm (Soret band) (2.96 ± 0.13) and the increased absorbance at 630 nm (0.07 ± 0.002 vs. 0.064 ± 0.005) indicated the conversion of oxyHb to metHb, which confirmed the oxidative damage to the erythrocytes. The linear regression analysis showed significant positive correlations between lead concentration and the percentage of plasma carbonyl content (R2 = 0.96), the relation of plasma carbonyl content to Hb absorbance at 630 nm (R2 = 0.97), and the relation of plasma carbonyl content to metHb concentration (R2 = 0.95) after 120 minutes incubation with lead
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.
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)
NASA Astrophysics Data System (ADS)
Zakharov, F. N.; Akulinichev, Yu. P.; Anikin, A. S.
2017-07-01
A new method is proposed to calculate the mean level of an electromagnetic field propagating along sea paths, based on a numerical solution of the parabolic equation. A way of taking the influence of waviness of the sea surface on the mean level of the field strength of the radio field is proposed. This method is based on the method of conformal mapping of a curvilinear coordinate system above the uneven sea surface onto a Cartesian coordinate system above the sea surface. A comparison with computer simulations obtained using the Monte Carlo method is carried out.
NASA Astrophysics Data System (ADS)
Yamazaki, K.; Kawahata, K.; Ando, R.; Matsuoka, K.; Hirokura, S.; Kitagawa, S.; Mohri, A.; Tanahashi, S.; Taniguchi, Y.; Toi, K.
1986-09-01
Disruptive behavior of magnetic field configuration leading to tokamak major disruption is found to be controlled by a mild mini-disruption which is induced by the compact external modular multipole-field coils with m=3/n=2 dominant helical field component in the JIPP T-IIU tokamak. This mini-disruption ergodizes the m=2/n=1 magnetic island quickly but mildly and then prevents the profile of electron temperature from flattening. This quick profile-reorganization is effective to avoid the two-step disruption (pre- and major disruptions) responsible for the catastrophic current termination.
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.
NASA Astrophysics Data System (ADS)
Du, Xinyu; Zhao, Chunlin; Zhang, Jinxi; Ren, Kailiang
2016-10-01
In this investigation, the chain conformation transformation of the piezoelectric polymer of a poly(L-Lactic Acid) (PLLA) film was analyzed under an electric field for the first time using infrared spectroscopy. It is revealed that the piezoelectric shear mode coefficient d14 (˜10 pC/N) of a stretched α form PLLA film mainly comes from the rotation of C O dipoles inside the polymer main chain. The reorientation of the dipoles causes the deformation of the crystal structure, which corresponds to a shear mode strain macroscopically in the PLLA film along a 45° direction to the polymer length. The back-bone of the molecular chain keeps its own conformation of a 103 helix under an external field up to 100 MV/m.
2005-08-01
that compared to customized electron bolu s radiotherapy for post-mastectomy irradiation, ECT with multi-energy, multi-segmente d treatment fields has...PTV dos e homogeneity was quite good . Use of the treatment plan modification techniques improved dose sparin g for the non-target portion of the...phantom . For the patient treatment plans, the algorithm provided acceptable results for PTV conformality and dose homogeneity, in comparison to the bolus
Effect of Externally Applied Perturbation Fields on Alfvénic MHD Activity in the NSTX Tokamak
NASA Astrophysics Data System (ADS)
Bortolon, Alessandro
2014-10-01
Observations from NSTX demonstrate that externally applied magnetic perturbations (MP) can alter the dynamic of beam driven Alfvén modes. Bursting Global Alfvén Eigenmodes (GAE, n = 7-9, 400-700 kHz) respond to pulses of static n = 3 fields (δB/B ~ 0.01 at the plasma edge) reducing mode amplitude, bursting period and frequency sweep by a factor of 2-3 [Bortolon et al., Phys. Rev. Lett. 110, 265008 (2013)]. Similar MP attenuate the amplitude of continuous Toroidal Alfvén Eigenmodes (TAE, n = 2-3, 50-90 kHz). Calculations of the perturbed beam-ion distribution function, considering MP from ideal or resistive plasma response, confirm an enhanced fast-ion transport consistent with a reduced drive for the GAE. At the same time, MP can also affect the Alfvén stability by altering the structure of Alfvén continua through modification of the kinetic profiles or introducing toroidal coupling as result of the broken axisymmetry. Computations of the n = 2 Alfvén continuum for NSTX equilibria with n = 3 MP show strong modification of the TAE continuum near the plasma edge, where coupling between n = 2 and n = 5 continuum modes reduces the gap, providing an additional damping for TAE modes extending in this region. DOE Contracts No. DE-FG02-06ER54867, DE-AC02-09CH11466.
Investigations of flow field perturbations induced on slotted transonic-tunnel walls
NASA Technical Reports Server (NTRS)
Wu, J. M.; Collins, F. G.
1984-01-01
The free-stream interference caused by the flow through the slotted walls of the test sections of transonic wind tunnels has continuously a problem in transonic tunnel testing. The adaptive-wall transonic tunnel is designed to actively control the near-wall boundary conditions by sucking or blowing through the wall. In order to make the adaptive-wall concept work, parameters for computational boundary conditions must be known. These parameters must be measured with sufficient accuracy to allow numerical convergence of the flow field computations and must be measured in an inviscid region away from the model that is placed inside the wind tunnel. The near-wall flow field was mapped in detail using a five-port cone probe that was traversed in a plane transverse to the free-stream flow. The initial experiments were made using a single slot and recent measurements used multiple slots, all with the tunnel empty. The projection of the flow field velocity vectors on the transverse plane revealed the presence of a vortex-like flow with vorticity in the free stream. The current research involves the measurement of the flow field above a multislotted system with segmented plenums behind it, in which the flow is controlled through several plenums simultaneously. This system would be used to control a three-dimensional flow field.
Interaction of the Barbero-Immirzi field with matter and pseudoscalar perturbations
NASA Astrophysics Data System (ADS)
Mercuri, Simone; Taveras, Victor
2009-11-01
In loop quantum gravity the classical point of departure is the Einstein-Hilbert action modified by the addition of the so-called Holst term. Classically, this term does not affect the equations of motion, but it induces a well-known quantization ambiguity in the quantum theory, parametrized by the Barbero-Immirzi parameter. Recently, it has been suggested to promote the Barbero-Immirzi parameter to a field. The resulting theory, obtainable starting from the usual Holst action, is general relativity coupled to a pseudoscalar field. However, this theory turns out to have an unconventional kinetic term for the Barbero-Immirzi field and a rather unnatural coupling with fermions. The main goal of this work is twofold: First, to propose a further generalization of the Holst action, which yields a theory of gravity and matter with a more natural coupling to the Barbero-Immirzi field; second, to study the possible implications for cosmology correlated to the existence of this new pseudoscalar field.
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.
Shivakumar, Devleena; Williams, Joshua; Wu, Yujie; Damm, Wolfgang; Shelley, John; Sherman, Woody
2010-05-11
The accurate prediction of protein-ligand binding free energies is a primary objective in computer-aided drug design. The solvation free energy of a small molecule provides a surrogate to the desolvation of the ligand in the thermodynamic process of protein-ligand binding. Here, we use explicit solvent molecular dynamics free energy perturbation to predict the absolute solvation free energies of a set of 239 small molecules, spanning diverse chemical functional groups commonly found in drugs and drug-like molecules. We also compare the performance of absolute solvation free energies obtained using the OPLS_2005 force field with two other commonly used small molecule force fields-general AMBER force field (GAFF) with AM1-BCC charges and CHARMm-MSI with CHelpG charges. Using the OPLS_2005 force field, we obtain high correlation with experimental solvation free energies (R(2) = 0.94) and low average unsigned errors for a majority of the functional groups compared to AM1-BCC/GAFF or CHelpG/CHARMm-MSI. However, OPLS_2005 has errors of over 1.3 kcal/mol for certain classes of polar compounds. We show that predictions on these compound classes can be improved by using a semiempirical charge assignment method with an implicit bond charge correction.
Perturbative Approaching for Boson Fields' System in a Lewis-Papapetrou Space-Time
Murariu, G.; Dariescu, M. A.; Dariescu, C.
2010-08-04
In this paper the first order solutions of a Klein--Gordon--Maxwell--Einstein coupled system equations were derived for boson fields in a Lewis Papapetrou space time. The results expand the previous static solutions obtained in literature. A main goal is represented by the symbolic script built for such approach.
Zhang, Zhongqiang; Yang, Xiu; Lin, Guang
2016-04-14
Sensor placement at the extrema of Proper Orthogonal Decomposition (POD) is efficient and leads to accurate reconstruction of the wind field from a limited number of measure- ments. In this paper we extend this approach of sensor placement and take into account measurement errors and detect possible malfunctioning sensors. We use the 48 hourly spa- tial wind field simulation data sets simulated using the Weather Research an Forecasting (WRF) model applied to the Maine Bay to evaluate the performances of our methods. Specifically, we use an exclusion disk strategy to distribute sensors when the extrema of POD modes are close. It turns out that this strategy can also reduce the error of recon- struction from noise measurements. Also, by a cross-validation technique, we successfully locate the malfunctioning sensors.
Zhang, Zhongqiang; Yang, Xiu; Lin, Guang
2016-04-14
Sensor placement at the extrema of Proper Orthogonal Decomposition (POD) is efficient and leads to accurate reconstruction of the wind field from a limited number of measure- ments. In this paper we extend this approach of sensor placement and take into account measurement errors and detect possible malfunctioning sensors. We use the 48 hourly spa- tial wind field simulation data sets simulated using the Weather Research an Forecasting (WRF) model applied to the Maine Bay to evaluate the performances of our methods. Specifically, we use an exclusion disk strategy to distribute sensors when the extrema of POD modes are close.more » It turns out that this strategy can also reduce the error of recon- struction from noise measurements. Also, by a cross-validation technique, we successfully locate the malfunctioning sensors.« less
1990-07-01
conformation of bacteriorhodopsin and of alamethicin incorporated in lipid bilayers was obtained from the change in the measured circular dichroism (CD... bacteriorhodopsin and of alamethicin. changed with the applied membrane potential. However. in the case of bacteriorhodopsin which was fully embedded In thie
On the field description of conformal Galilean particle with intrinsic rotations
Kireev, A.N.; Takahashi, Y. . Theoretical Physics Inst.)
1992-05-30
This paper reports that a fiber-preserving realization of conformal extension of the Galilei algebra is found in the presence of intrinsic rotations. The Lagrangian density and the conservation laws of a non-relativistic spinning particles are constructed explicitly.
NASA Astrophysics Data System (ADS)
Rajabpour, M. A.
2016-12-01
We calculate formation probabilities of the ground state of the finite size quantum critical chains using conformal field theory (CFT) techniques. In particular, we calculate the formation probability of one interval in the finite open chain and also formation probability of two disjoint intervals in a finite periodic system. The presented formulas can be also interpreted as the Casimir energy of needles in particular geometries. We numerically check the validity of the exact CFT results in the case of the transverse field Ising chain.
Evangelina, Figueroa M.; Gabriel, Resendiz G.; Miguel, Perez P.
2008-08-11
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.
NASA Astrophysics Data System (ADS)
Friis-Christensen, E.; Finlay, C. C.; Hesse, M.; Laundal, K. M.
2017-02-01
In the day-side sunlit polar ionosphere the varying and IMF dependent convection creates strong ionospheric currents even during quiet geomagnetic conditions. Observations during such times are often excluded when using satellite data to model the internal geomagnetic main field. Observations from the night-side or local winter during quiet conditions are, however, also influenced by variations in the IMF. In this paper we briefly review the large scale features of the ionospheric currents in the polar regions with emphasis on the current distribution during undisturbed conditions. We examine the distribution of scalar measurements of the magnetic field intensity minus predictions from a geomagnetic field model. These `residuals' fall into two main categories. One category is consistently distributed according to the well-known ionospheric plasma convection and its associated Birkeland currents. The other category represent contributions caused by geomagnetic activity related to the substorm current wedge around local magnetic midnight. A new observation is a strong IMF By control of the residuals in the midnight sector indicating larger ionospheric currents in the substorm current wedge in the northern polar region for By > 0 and correspondingly in the southern hemisphere for By < 0.
NASA Astrophysics Data System (ADS)
Friis-Christensen, E.; Finlay, C. C.; Hesse, M.; Laundal, K. M.
2017-03-01
In the day-side sunlit polar ionosphere the varying and IMF dependent convection creates strong ionospheric currents even during quiet geomagnetic conditions. Observations during such times are often excluded when using satellite data to model the internal geomagnetic main field. Observations from the night-side or local winter during quiet conditions are, however, also influenced by variations in the IMF. In this paper we briefly review the large scale features of the ionospheric currents in the polar regions with emphasis on the current distribution during undisturbed conditions. We examine the distribution of scalar measurements of the magnetic field intensity minus predictions from a geomagnetic field model. These `residuals' fall into two main categories. One category is consistently distributed according to the well-known ionospheric plasma convection and its associated Birkeland currents. The other category represent contributions caused by geomagnetic activity related to the substorm current wedge around local magnetic midnight. A new observation is a strong IMF By control of the residuals in the midnight sector indicating larger ionospheric currents in the substorm current wedge in the northern polar region for By > 0 and correspondingly in the southern hemisphere for By < 0.
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.
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.
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.
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.
Fröb, Markus B.; Verdaguer, Enric E-mail: enric.verdaguer@ub.edu
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.
NASA Astrophysics Data System (ADS)
Paech, Martin; Apel, Walter; Kalinowski, Eva; Jeckelmann, Eric
2014-12-01
We present a large-scale combinatorial-diagrammatic computation of high-order contributions to the strong-coupling Kato-Takahashi perturbation series for the Hubbard model in high dimensions. The ground-state energy of the Mott-insulating phase is determined exactly up to the 15th order in 1 /U . The perturbation expansion is extrapolated to infinite order and the critical behavior is determined using the Domb-Sykes method. We compare the perturbative results with two dynamical mean-field theory (DMFT) calculations using a quantum Monte Carlo method and a density-matrix renormalization group method as impurity solvers. The comparison demonstrates the excellent agreement and accuracy of both extrapolated strong-coupling perturbation theory and quantum Monte Carlo based DMFT, even close to the critical coupling where the Mott insulator becomes unstable.
Scalar field-perfect fluid correspondence and non-linear perturbation equations
Mainini, Roberto
2008-07-15
The properties of dynamical dark energy (DE) and, in particular, the possibility that it can form or contribute to stable inhomogeneities have been widely debated in recent literature, and also in association with a possible coupling between DE and dark matter (DM). In order to clarify this issue, in this paper we present a general framework for the study of the non-linear phases of structure formation, showing the equivalence of two possible descriptions of DE: a scalar field {phi} self-interacting through a potential V ({phi}) and a perfect fluid with an assigned negative equation of state w(a). This enables us to show that, in the presence of coupling, the mass of DE quanta may increase where large DM condensations are present, with the result that also DE may be involved in the clustering process.
Harper, Sandra L; Sriswasdi, Sira; Tang, Hsin-Yao; Gaetani, Massimiliano; Gallagher, Patrick G; Speicher, David W
2013-10-24
Hereditary elliptocytosis (HE) and hereditary pyropoikilocytosis (HPP) are common disorders of erythrocyte shape primarily because of mutations in spectrin. The most common HE/HPP mutations are located distant from the critical αβ-spectrin tetramerization site, yet still interfere with formation of spectrin tetramers and destabilize the membrane by unknown mechanisms. To address this question, we studied the common HE-associated mutation, αL260P, in the context of a fully functional mini-spectrin. The mutation exhibited wild-type tetramer binding in univalent binding assays, but reduced binding affinity in bivalent-binding assays. Biophysical analyses demonstrated the mutation-containing domain was only modestly structurally destabilized and helical content was not significantly changed. Gel filtration analysis of the αL260P mini-spectrin indicated more compact structures for dimers and tetramers compared with wild-type. Chemical crosslinking showed structural changes in the mutant mini-spectrin dimer were primarily restricted to the vicinity of the αL260P mutation and indicated large conformational rearrangements of this region. These data indicate the mutation increased the stability of the closed dimer state, thereby reducing tetramer assembly and resulting in membrane destabilization. These results reveal a novel mechanism of erythrocyte membrane destabilization that could contribute to development of therapeutic interventions for mutations in membrane proteins containing spectrin-type domains associated with inherited disease.
de la Rica, Roberto; Baldi, Antonio; Fernández-Sánchez, César; Matsui, Hiroshi
2009-05-15
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 x 10(2) cfu/mL and an incubation time of only 1 h. The CMOS compatible fabrication process of the chip along with the label-free, reagent-less 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.
NASA Technical Reports Server (NTRS)
Slavin, J. A.; Hesse, M.; Owen, C. J.; Taguchi, S.; Fairfield, D. H.; Lepping, R. P.; Kokubun, S.; Mukai, T.; Lui, A. T. Y.; Anderson, R. R.
1999-01-01
This study examines a unique data set returned by IMP8 and Geotail on January 29, 1995 during a substorm which resulted in the ejection of a plasmoid. The two spacecraft (s/c) were situated in the north lobe of the tail and both observed a traveling compression region (TCR). From single s/c observations only the length of the plasmoid in X and an estimate of its height in Z can be determined. However, we show that dual s/c measurements of TCRs can be used to model all three dimensions of the underlying plasmoid and to estimate of its rate of expansion or contraction. For this event plasmoid dimensions of Delta(X) approximates 18, Delta(Y) approximates 30, and Delta(Z) approximates 10 R(sub e) are inferred from the IMP8 and Geotail lobe magnetic field measurements. The earthward end of the plasmoid was inferred to be near the mean location of the near-earth neutral line, X approximates -26 R(sub e). Its center was underneath IMP 8 at X approximates -34 R(sub e) and its tailward end appeared to be near X approximates -44 R(sub e). Furthermore, a factor of approximately 2 increase in the amplitude of the TCR occurred in the 1.5 min it took to move from IMP 8 to Geotail. Modeled using conservation of the magnetic flux, this increase in lobe compression implies that the underlying plasmoid was expanding at a rate of approximately 140 km/s. Such an expansion is comparable to recently reported V(sub y) speeds in "young" plasmoids in this region of the tail. Finally, the Geotail measurements indicate that a reconfiguration of the lobe magnetic field closely followed the ejection of the plasmoid which moved magnetic flux tubes into the wake behind the plasmoid where they would convect into the near-earth neutral line and reconnect.
NASA Astrophysics Data System (ADS)
Martin, E. H.; Caughman, J. B. O.; Klepper, C. C.; Goniche, M.; Isler, R. C.; Hillairet, J.; Bottereau, C.
2015-12-01
The physics of wave heating and current drive processes in the bulk hot plasma are generally well identified. However, details of the wave-plasma interaction in the cold plasma edge are still not fully understood. In this paper a spectroscopic technique allowing for measurements of the electric field driving wave-plasma interactions in the edge region for LH current drive and ICRH systems will be discussed. Experimental results obtained in Tore Supra near the LH C3 antenna and in the magnetized capacitively coupled RF sheath from an experiment designed to mimic the ICRF near-field are presented. In conclusion, future plans to implement a laser-based spectroscopic technique to acquire the high resolution measurements needed for model validation is discussed.
Eikonalization of conformal blocks
Fitzpatrick, A. Liam; Kaplan, Jared; Walters, Matthew T.; ...
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
Eikonalization of conformal blocks
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