I. Cirac (Max Planck Institute, Garching
Electricfield correlation in quantum charged fluids coupled to the radiation field
SciTech Connect
Jancovici, B.
20061115
In a recent paper [S. El Boustani, P. R. Buenzli, and P. A. Martin, Phys. Rev. E 73, 036113 (2006)] about quantum charges in equilibrium with radiation, among other things the asymptotic form of the electricfield correlation has been obtained by a microscopic calculation. It has been found that this correlation has a longrange algebraic decay of the form 1/r{sup 3} (except in the classical limit). The macroscopic approach, in the Course of Theoretical Physics of Landau and Lifshitz, gives no such decay. In this Brief Report we revisit and complete the macroscopic approach of Landau and Lifshitz and suggest that, perhaps, the use of a classical electromagnetic field by El Boustani et al. was not justified.
Quantum field theory constrains traversable wormhole geometries
SciTech Connect
Ford, L.H. ; Roman, T.A. 
19960501
Recently a bound on negative energy densities in fourdimensional Minkowski spacetime was derived for a minimally coupled, quantized, massless, scalar field in an arbitrary quantum state. The bound has the form of an uncertaintyprincipletype constraint on the magnitude and duration of the negative energy density seen by a timelike geodesic observer. When spacetime is curved and/or has boundaries, we argue that the bound should hold in regions small compared to the minimum local characteristic radius of curvature or the distance to any boundaries, since spacetime can be considered approximately Minkowski on these scales. We apply the bound to the stressenergy of static traversable wormhole spacetimes. Our analysis implies that either the wormhole must be only a little larger than Planck size or that there is a large discrepancy in the length scales which characterize the wormhole. In the latter case, the negative energy must typically be concentrated in a thin band many orders of magnitude smaller than the throat size. These results would seem to make the existence of macroscopic traversable wormholes very improbable. {copyright} {ital 1996 The American Physical Society.}
Continuum regularization of quantum field theory
SciTech Connect
Bern, Z.
19860401
Possible nonperturbative continuum regularization schemes for quantum field theory are discussed which are based upon the Langevin equation of Parisi and Wu. Breit, Gupta and Zaks made the first proposal for new gauge invariant nonperturbative regularization. The scheme is based on smearing in the ''fifthtime'' of the Langevin equation. An analysis of their stochastic regularization scheme for the case of scalar electrodynamics with the standard covariant gauge fixing is given. Their scheme is shown to preserve the masslessness of the photon and the tensor structure of the photon vacuum polarization at the oneloop level. Although stochastic regularization is viable in oneloop electrodynamics, two difficulties arise which, in general, ruins the scheme. One problem is that the superficial quadratic divergences force a bottomless action for the noise. Another difficulty is that stochastic regularization by fifthtime smearing is incompatible with Zwanziger's gauge fixing, which is the only known nonperturbaive covariant gauge fixing for nonabelian gauge theories. Finally, a successful covariant derivative scheme is discussed which avoids the difficulties encountered with the earlier stochastic regularization by fifthtime smearing. For QCD the regularized formulation is manifestly Lorentz invariant, gauge invariant, ghost free and finite to all orders. A vanishing gluon mass is explicitly verified at one loop. The method is designed to respect relevant symmetries, and is expected to provide suitable regularization for any theory of interest. Hopefully, the scheme will lend itself to nonperturbative analysis. 44 refs., 16 figs.
Quantum analysis applied to thermo field dynamics on dissipative systems
SciTech Connect
Hashizume, Yoichiro; Okamura, Soichiro; Suzuki, Masuo
20150310
Thermo field dynamics is one of formulations useful to treat statistical mechanics in the scheme of field theory. In the present study, we discuss dissipative thermo field dynamics of quantum damped harmonic oscillators. To treat the effective renormalization of quantum dissipation, we use the SuzukiTakano approximation. Finally, we derive a dissipative von Neumann equation in the Lindbrad form. In the present treatment, we can easily obtain the initial damping shown previously by Kubo.
Monte Carlo fieldtheoretic simulations of a homopolymer blend
NASA Astrophysics Data System (ADS)
Spencer, Russell; Matsen, Mark
Fluctuation corrections to the macrophase segregation transition (MST) in a symmetric homopolymer blend are examined using Monte Carlo fieldtheoretic simulations (MCFTS). This technique involves treating interactions between unlike monomers using standard MonteCarlo techniques, while enforcing incompressibility as is done in meanfield theory. When using MCFTS, we need to account for a UV divergence. This is done by renormalizing the FloryHuggins interaction parameter to incorporate the divergent part of the Hamiltonian. We compare different ways of calculating this effective interaction parameter. Near the MST, the length scale of compositional fluctuations becomes large, however, the high computational requirements of MCFTS restrict us to small system sizes. We account for these finite size effects using the method of Binder cumulants, allowing us to locate the MST with high precision. We examine fluctuation corrections to the mean field MST, χN = 2 , as they vary with the invariant degree of polymerization, N =ρ2a6 N . These results are compared with particlebased simulations as well as analytical calculations using the renormalized one loop theory. This research was funded by the Center for Sustainable Polymers.
Theoretical and experimental examination of nearfield acoustic levitation.
PubMed
Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa
20020401
A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called nearfield acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 20572061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5kHz piston source with a 40mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense. PMID:12002842
Modern Quantum Field Theory II  Proceeeings of the International Colloquium
NASA Astrophysics Data System (ADS)
Das, S. R.; Mandal, G.; Mukhi, S.; Wadia, S. R.
19950801
The Table of Contents for the book is as follows: * Foreword * 1. Black Holes and Quantum Gravity * Quantum Black Holes and the Problem of Time * Black Hole Entropy and the Semiclassical Approximation * Entropy and Information Loss in Two Dimensions * Strings on a Cone and Black Hole Entropy (Abstract) * Boundary Dynamics, Black Holes and Spacetime Fluctuations in Dilation Gravity (Abstract) * Pair Creation of Black Holes (Abstract) * A Brief View of 2Dim. String Theory and Black Holes (Abstract) * 2. String Theory * NonAbelian Duality in WZW Models * Operators and Correlation Functions in c ≤ 1 String Theory * New Symmetries in String Theory * A Look at the Discretized Superstring Using Random Matrices * The Nested BRST Structure of WnSymmetries * LandauGinzburg Model for a Critical Topological String (Abstract) * On the Geometry of Wn Gravity (Abstract) * O(d, d) Tranformations, Marginal Deformations and the Coset Construction in WZNW Models (Abstract) * Nonperturbative Effects and Multicritical Behaviour of c = 1 Matrix Model (Abstract) * Singular Limits and String Solutions (Abstract) * BV Algebra on the Moduli Spaces of Riemann Surfaces and String Field Theory (Abstract) * 3. Condensed Matter and Statistical Mechanics * Stochastic Dynamics in a DepositionEvaporation Model on a Line * Models with InverseSquare Interactions: Conjectured Dynamical Correlation Functions of the CalogeroSutherland Model at Rational Couplings * Turbulence and Generic Scale Invariance * Singular Perturbation Approach to Phase Ordering Dynamics * Kinetics of DiffusionControlled and BallisticallyControlled Reactions * Field Theory of a Frustrated Heisenberg Spin Chain * FQHE Physics in Relativistic Field Theories * Importance of Initial Conditions in Determining the Dynamical Class of Cellular Automata (Abstract) * Do HardCore Bosons Exhibit Quantum Hall Effect? (Abstract) * Hysteresis in Ferromagnets * 4. Fundamental Aspects of Quantum Mechanics and Quantum Field Theory
Matter coupling to strong electromagnetic fields in twolevel quantum systems with broken inversion symmetry.
PubMed
Kibis, O V; Slepyan, G Ya; Maksimenko, S A; Hoffmann, A
20090116
We demonstrate theoretically the parametric oscillator behavior of a twolevel quantum system with broken inversion symmetry exposed to a strong electromagnetic field. A multitude of resonance frequencies and additional harmonics in the scattered light spectrum as well as an altered Rabi frequency are predicted to be inherent to such systems. In particular, dipole radiation at the Rabi frequency appears to be possible. Since the Rabi frequency is controlled by the strength of the coupling electromagnetic field, the effect can serve for the frequencytuned parametric amplification and generation of electromagnetic waves. Manifestation of the effect is discussed for IIInitride quantum dots with strong builtin electric field breaking the inversion symmetry. Terahertz emission from arrays of such quantum dots is shown to be experimentally observable. PMID:19257272
Theoretical analysis of magnetic field interactions with aortic blood flow
SciTech Connect
Kinouchi, Y.; Yamaguchi, H.; Tenforde, T.S.
19960401
The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete NavierStokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their fieldstrength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue.
Quantum gases. Observation of isolated monopoles in a quantum field.
PubMed
Ray, M W; Ruokokoski, E; Tiurev, K; Möttönen, M; Hall, D S
20150501
Topological defects play important roles throughout nature, appearing in contexts as diverse as cosmology, particle physics, superfluidity, liquid crystals, and metallurgy. Point defects can arise naturally as magnetic monopoles resulting from symmetry breaking in grand unified theories. We devised an experiment to create and detect quantum mechanical analogs of such monopoles in a spin1 BoseEinstein condensate. The defects, which were stable on the time scale of our experiments, were identified from spinresolved images of the condensate density profile that exhibit a characteristic dependence on the choice of quantization axis. Our observations lay the foundation for experimental studies of the dynamics and stability of topological point defects in quantum systems. PMID:25931553
Theoretical performance of solar cell based on minibands quantum dots
SciTech Connect
Aly, Abou ElMaaty M. Email: ashraf.nasr@gmail.com; Nasr, A. Email: ashraf.nasr@gmail.com
20140321
The tremendous amount of research in solar energy is directed toward intermediate band solar cell for its advantages compared with the conventional solar cell. The latter has lower efficiency because the photons have lower energy than the bandgap energy and cannot excite mobile carriers from the valence band to the conduction band. On the other hand, if mini intermediate band is introduced between the valence and conduction bands, then the smaller energy photons can be used to promote charge carriers transfer to the conduction band and thereby the total current increases while maintaining a large open circuit voltage. In this article, the influence of the new band on the power conversion efficiency for structure of quantum dots intermediate band solar cell is theoretically investigated and studied. The timeindependent Schrödinger equation is used to determine the optimum width and location of the intermediate band. Accordingly, achievement of a maximum efficiency by changing the width of quantum dots and barrier distances is studied. Theoretical determination of the power conversion efficiency under the two different ranges of QD width is presented. From the obtained results, the maximum power conversion efficiency is about 70.42%. It is carried out for simple cubic quantum dot crystal under fully concentrated light. It is strongly dependent on the width of quantum dots and barrier distances.

Charged and Electromagnetic Fields from Relativistic Quantum Geometry
NASA Astrophysics Data System (ADS)
Arcodía, Marcos; Bellini, Mauricio
20160601
In the Relativistic Quantum Geometry (RQG) formalism recently introduced, was explored the possibility that the variation of the tensor metric can be done in a Weylian integrable manifold using a geometric displacement, from a Riemannian to a Weylian integrable manifold, described by the dynamics of an auxiliary geometrical scalar field $\\theta$, in order that the Einstein tensor (and the Einstein equations) can be represented on a Weyllike manifold. In this framework we study jointly the dynamics of electromagnetic fields produced by quantum complex vector fields, which describes charges without charges. We demonstrate that complex fields act as a source of tetravector fields which describe an extended Maxwell dynamics.

Illustrating the quantum approach with an Earth magnetic field MRI
NASA Astrophysics Data System (ADS)
Pars Benli, Kami; Dillmann, Baudouin; Louelh, Ryma; PoirierQuinot, Marie; Darrasse, Luc
20150501
Teaching imaging of magnetic resonance (MR) today is still as challenging as it has always been, because it requires admitting that we cannot express fundamental questions of quantum mechanics with straightforward language or without using extensive theory. Here we allow students to face a real MR setup based on the Earth's magnetic field. We address the applied side of teaching MR using a device that is affordable and that proves to be sufficiently robust, at universities in Orsay, France, and San Sebastian, Spain, in experimental practicals at undergraduate and graduate levels. We specifically present some of the advantages of low field for measuring R2 relaxation rates, reaching a power of separation of 1.5 μmol on Mn(II) ions between two water bottles each of half a liter. Finally we propose key approaches for the lecturers to adopt when they are asked to pass from theoretical knowledge to teachable knowhow. The outcomes are fast calibration and the MR acquisition protocols, demonstrating the reproducibility of energy transfer during the saturation pulses, and the quantitative nature of MR, with water protons and a helium3 sample.

Finite fielddependent symmetries in perturbative quantum gravity
NASA Astrophysics Data System (ADS)
Upadhyay, Sudhaker
20140101
In this paper we discuss the absolutely anticommuting nilpotent symmetries for perturbative quantum gravity in general curved spacetime in linear and nonlinear gauges. Further, we analyze the finite fielddependent BRST (FFBRST) transformation for perturbative quantum gravity in general curved spacetime. The FFBRST transformation changes the gaugefixing 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 nonlinear CurciFerrari and Landau gauges of perturbative quantum gravity. The validity of the results is also established at quantum level using BatalinVilkovisky (BV) formulation.

Quantum Gravity from the Point of View of Locally Covariant Quantum Field Theory
NASA Astrophysics Data System (ADS)
Brunetti, Romeo; Fredenhagen, Klaus; Rejzner, Katarzyna
20160801
We construct perturbative quantum gravity in a generally covariant way. In particular our construction is background independent. It is based on the locally covariant approach to quantum field theory and the renormalized BatalinVilkovisky formalism. We do not touch the problem of nonrenormalizability and interpret the theory as an effective theory at large length scales.

Quantum entanglement of identical particles by standard informationtheoretic notions.
PubMed
Lo Franco, Rosario; Compagno, Giuseppe
20160101
Quantum entanglement of identical particles is essential in quantum information theory. Yet, its correct determination remains an open issue hindering the general understanding and exploitation of manyparticle systems. Operatorbased methods have been developed that attempt to overcome the issue. Here we introduce a statebased method which, as second quantization, does not label identical particles and presents conceptual and technical advances compared to the previous ones. It establishes the quantitative role played by arbitrary wave function overlaps, local measurements and particle nature (bosons or fermions) in assessing entanglement by notions commonly used in quantum information theory for distinguishable particles, like partial trace. Our approach furthermore shows that bringing identical particles into the same spatial location functions as an entangling gate, providing fundamental theoretical support to recent experimental observations with ultracold atoms. These results pave the way to set and interpret experiments for utilizing quantum correlations in realistic scenarios where overlap of particles can count, as in BoseEinstein condensates, quantum dots and biological molecular aggregates. PMID:26857475

Quantum entanglement of identical particles by standard informationtheoretic notions
NASA Astrophysics Data System (ADS)
Lo Franco, Rosario; Compagno, Giuseppe
20160201
Quantum entanglement of identical particles is essential in quantum information theory. Yet, its correct determination remains an open issue hindering the general understanding and exploitation of manyparticle systems. Operatorbased methods have been developed that attempt to overcome the issue. Here we introduce a statebased method which, as second quantization, does not label identical particles and presents conceptual and technical advances compared to the previous ones. It establishes the quantitative role played by arbitrary wave function overlaps, local measurements and particle nature (bosons or fermions) in assessing entanglement by notions commonly used in quantum information theory for distinguishable particles, like partial trace. Our approach furthermore shows that bringing identical particles into the same spatial location functions as an entangling gate, providing fundamental theoretical support to recent experimental observations with ultracold atoms. These results pave the way to set and interpret experiments for utilizing quantum correlations in realistic scenarios where overlap of particles can count, as in BoseEinstein condensates, quantum dots and biological molecular aggregates.

Quantum entanglement of identical particles by standard informationtheoretic notions
PubMed Central
Lo Franco, Rosario; Compagno, Giuseppe
20160101
Quantum entanglement of identical particles is essential in quantum information theory. Yet, its correct determination remains an open issue hindering the general understanding and exploitation of manyparticle systems. Operatorbased methods have been developed that attempt to overcome the issue. Here we introduce a statebased method which, as second quantization, does not label identical particles and presents conceptual and technical advances compared to the previous ones. It establishes the quantitative role played by arbitrary wave function overlaps, local measurements and particle nature (bosons or fermions) in assessing entanglement by notions commonly used in quantum information theory for distinguishable particles, like partial trace. Our approach furthermore shows that bringing identical particles into the same spatial location functions as an entangling gate, providing fundamental theoretical support to recent experimental observations with ultracold atoms. These results pave the way to set and interpret experiments for utilizing quantum correlations in realistic scenarios where overlap of particles can count, as in BoseEinstein condensates, quantum dots and biological molecular aggregates. PMID:26857475

Localization of firearm projectiles in the human body using a superconducting quantum interference device magnetometer: A theoretical study
NASA Astrophysics Data System (ADS)
Hall Barbosa, C.
20040601
A technique had been previously developed, based on magnetic field measurements using a superconducting quantum interference device sensor, to localize in three dimensions steel needles lost in the human body. In all six cases that were treated until now, the technique allowed easy surgical localization of the needles with high accuracy. The technique decreases, by a large factor, the surgery time for foreign body extraction, and also reduces the generally high odds of failure. The method is accurate, noninvasive, and innocuous, and with clear clinical importance. Despite the importance of needle localization, the most prevalent foreign body in the modern society is the firearm projectile (bullet), generally composed of lead, a paramagnetic material, thus not presenting a remanent magnetic field as steel needles do. On the other hand, since lead is a good conductor, eddy current detection techniques can be employed, by applying an alternating magnetic field with the aid of excitation coils. The primary field induces eddy currents on the lead, which in turn generate a secondary magnetic field that can be detected by a magnetometer, and give information about position and volume of the conducting foreign body. In this article we present a theoretical study for the development of a localization technique for lead bullets inside the human body. Initially, we present a model for the secondary magnetic field generated by the bullet, given a known applied field. After that, we study possible excitation systems, and propose a localization algorithm based on the detected magnetic field.

Quantum Mutual Entropy for a Multilevel Atom Interacting with a Cavity Field
NASA Astrophysics Data System (ADS)
AbdelAty, M.; Wahiddin, M. R. B.; Obada, A.S. F.
20070401
We derive an explicit formula for the quantum mutual entropy as a measure of the total correlations in a multilevel atom interacting with a cavity field. We describe its theoretical basis and discuss its practical relevance. The effect of the number of levels involved on the quantum mutual entropy is demonstrated via examples of three, four and fivelevel atom. Numerical calculations under current experimental conditions are performed and it is found that the number of levels present changes the general features of the correlations dramatically.

Quantum fields with noncommutative target spaces
NASA Astrophysics Data System (ADS)
Balachandran, A. P.; Queiroz, A. R.; Marques, A. M.; TeotonioSobrinho, P.
20080501
Quantum field theories (QFT’s) on noncommutative spacetimes are currently under intensive study. Usually such theories have world sheet noncommutativity. In the present work, instead, we study QFT’s with commutative world sheet and noncommutative target space. Such noncommutativity can be interpreted in terms of twisted statistics and is related to earlier work of Oeckl [R. Oeckl, Commun. Math. Phys. 217, 451 (2001).CMPHAY0010361610.1007/s002200100375], and others [A. P. Balachandran, G. Mangano, A. Pinzul, and S. Vaidya, Int. J. Mod. Phys. A 21, 3111 (2006)IMPAEF0217751X10.1142/S0217751X06031764; A. P. Balachandran, A. Pinzul, and B. A. Qureshi, Phys. Lett. B 634, 434 (2006)PYLBAJ0370269310.1016/j.physletb.2006.02.006; A. P. Balachandran, A. Pinzul, B. A. Qureshi, and S. Vaidya, arXiv:hepth/0608138; A. P. Balachandran, T. R. Govindarajan, G. Mangano, A. Pinzul, B. A. Qureshi, and S. Vaidya, Phys. Rev. D 75, 045009 (2007)PRVDAQ0556282110.1103/PhysRevD.75.045009; A. Pinzul, Int. J. Mod. Phys. A 20, 6268 (2005)IMPAEF0217751X10.1142/S0217751X05029290; G. Fiore and J. Wess, Phys. Rev. D 75, 105022 (2007)PRVDAQ0556282110.1103/PhysRevD.75.105022; Y. Sasai and N. Sasakura, Prog. Theor. Phys. 118, 785 (2007)PTPKAV0033068X10.1143/PTP.118.785]. The twisted spectra of their free Hamiltonians has been found earlier by Carmona et al. [J. M. Carmona, J. L. Cortes, J. Gamboa, and F. Mendez, Phys. Lett. B 565, 222 (2003)PYLBAJ0370269310.1016/S03702693(03)007287; J. M. Carmona, J. L. Cortes, J. Gamboa, and F. Mendez, J. High Energy Phys.JHEPFG10298479 03 (2003) 05810.1088/11266708/2003/03/058]. We review their derivation and then compute the partition function of one such typical theory. It leads to a deformed blackbody spectrum, which is analyzed in detail. The difference between the usual and the deformed blackbody spectrum appears in the region of high frequencies. Therefore we expect that the deformed blackbody radiation may potentially be used to compute a

The Physical Renormalization of Quantum Field Theories
SciTech Connect
Binger, Michael William.; /Stanford U., Phys. Dept. /SLAC
20070220
The profound revolutions in particle physics likely to emerge from current and future experiments motivates an improved understanding of the precise predictions of the Standard Model and new physics models. Higher order predictions in quantum field theories inevitably requires the renormalization procedure, which makes sensible predictions out of the naively divergent results of perturbation theory. Thus, a robust understanding of renormalization is crucial for identifying and interpreting the possible discovery of new physics. The results of this thesis represent a broad set of investigations in to the nature of renormalization. The author begins by motivating a more physical approach to renormalization based on gaugeinvariant Green's functions. The resulting effective charges are first applied to gauge coupling unification. This approach provides an elegant formalism for understanding all threshold corrections, and the gauge couplings unify in a more physical manner compared to the usual methods. Next, the gaugeinvariant threegluon vertex is studied in detail, revealing an interesting and rich structure. The effective coupling for the threegluon vertex, {alpha}(k{sub 1}{sup 2}, k{sub 2}{sup 2}, k{sub 3}{sup 2}), depends on three momentum scales and gives rise to an effective scale Q{sub eff}{sup 2}(k{sub 1}{sup 2}, k{sub 2}{sup 2}, k{sub 3}{sup 2}) which governs the (sometimes surprising) behavior of the vertex. The effects of nonzero internal masses are important and have a complicated threshold and pseudothreshold structure. The pinchtechnique effective charge is also calculated to twoloops and several applications are discussed. The Higgs boson mass in Split Supersymmetry is calculated to twoloops, including all oneloop threshold effects, leading to a downward shift in the Higgs mass of a few GeV. Finally, the author discusses some ideas regarding the overall structure of perturbation theory. This thesis lays the foundation for a comprehensive multi

BOOK REVIEW: Quantum Field Theory in a Nutshell (2nd edn) Quantum Field Theory in a Nutshell (2nd edn)
NASA Astrophysics Data System (ADS)
Peskin, Michael E.
20110401
Anthony Zee is not only a leading theoretical physicist but also an author of popular books on both physics and nonphysics topics. I recommend especially `Swallowing Clouds', on Chinese cooking and its folklore. Thus, it is not surprising that his textbook has a unique flavor. Derivations end, not with `QED' but with exclamation points. At the end of one argument, we read `Vive Cauchy!', in another `the theorem practically exudes generality'. This is quantum field theory taught at the knee of an eccentric uncle; one who loves the grandeur of his subject, has a keen eye for a slick argument, and is eager to share his repertoire of anecdotes about Feynman, Fermi, and all of his heroes. A onepage section entitled `Electric Charge' illustrates the depth and tone of the book. In the previous section, Zee has computed the Feynman diagram responsible for vacuum polarization, in which a photon converts briefly to a virtual electronpositron pair. In the first paragraph, he evaluates this expression, giving a concrete formula for the momentumdependence of the electric charge, an important effect of quantum field theory. Next, he dismisses other possible diagrams that could affect the value of the electric charge. Most authors would give an explicit argument that these diagrams cancel, but for Zee it is more important to make the point that this result is expected and, from the right point of view, obvious. Finally, he discusses the implications for the relative size of the charges of the electron and the proton. If the magnitudes of charges are affected by interactions, and the proton has strong interactions but the electron does not, can it make sense that the charges of the proton and the electron are exactly equal and opposite? The answer is yes, and also that this was the real point of the whole derivation. The book takes on the full range of topics covered in typical graduate course in quantum field theory, and many additional topics: magnetic monopoles, solitons

BOOK REVIEW: Quantum Field Theory in a Nutshell (2nd edn) Quantum Field Theory in a Nutshell (2nd edn)
NASA Astrophysics Data System (ADS)
Peskin, Michael E.
20110401
Anthony Zee is not only a leading theoretical physicist but also an author of popular books on both physics and nonphysics topics. I recommend especially `Swallowing Clouds', on Chinese cooking and its folklore. Thus, it is not surprising that his textbook has a unique flavor. Derivations end, not with `QED' but with exclamation points. At the end of one argument, we read `Vive Cauchy!', in another `the theorem practically exudes generality'. This is quantum field theory taught at the knee of an eccentric uncle; one who loves the grandeur of his subject, has a keen eye for a slick argument, and is eager to share his repertoire of anecdotes about Feynman, Fermi, and all of his heroes. A onepage section entitled `Electric Charge' illustrates the depth and tone of the book. In the previous section, Zee has computed the Feynman diagram responsible for vacuum polarization, in which a photon converts briefly to a virtual electronpositron pair. In the first paragraph, he evaluates this expression, giving a concrete formula for the momentumdependence of the electric charge, an important effect of quantum field theory. Next, he dismisses other possible diagrams that could affect the value of the electric charge. Most authors would give an explicit argument that these diagrams cancel, but for Zee it is more important to make the point that this result is expected and, from the right point of view, obvious. Finally, he discusses the implications for the relative size of the charges of the electron and the proton. If the magnitudes of charges are affected by interactions, and the proton has strong interactions but the electron does not, can it make sense that the charges of the proton and the electron are exactly equal and opposite? The answer is yes, and also that this was the real point of the whole derivation. The book takes on the full range of topics covered in typical graduate course in quantum field theory, and many additional topics: magnetic monopoles, solitons

Finite fielddependent symmetries in perturbative quantum gravity
SciTech Connect
Upadhyay, Sudhaker
20140115
In this paper we discuss the absolutely anticommuting nilpotent symmetries for perturbative quantum gravity in general curved spacetime in linear and nonlinear gauges. Further, we analyze the finite fielddependent BRST (FFBRST) transformation for perturbative quantum gravity in general curved spacetime. The FFBRST transformation changes the gaugefixing 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 nonlinear 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 antiBRST transformations are developed in linear and nonlinear gauges. •BRST transformation is generalized by making it finite and field dependent. •Connection between linear and nonlinear gauges is established. •Using BV formulation the results are established at quantum level also.

Quantum perceptron over a field and neural network architecture selection in a quantum computer.
PubMed
da Silva, Adenilton José; Ludermir, Teresa Bernarda; de Oliveira, Wilson Rosa
20160401
In this work, we propose a quantum neural network named quantum perceptron over a field (QPF). Quantum computers are not yet a reality and the models and algorithms proposed in this work cannot be simulated in actual (or classical) computers. QPF is a direct generalization of a classical perceptron and solves some drawbacks found in previous models of quantum perceptrons. We also present a learning algorithm named Superposition based Architecture Learning algorithm (SAL) that optimizes the neural network weights and architectures. SAL searches for the best architecture in a finite set of neural network architectures with linear time over the number of patterns in the training set. SAL is the first learning algorithm to determine neural network architectures in polynomial time. This speedup is obtained by the use of quantum parallelism and a nonlinear quantum operator. PMID:26878722

Quantum beats in the field ionization of Rydberg atoms in the presence of magnetic fields
NASA Astrophysics Data System (ADS)
Gregoric, Vincent C.; Hastings, Hannah; Carroll, Thomas J.; Noel, Michael W.
20160501
By exciting a coherent superposition and varying its phase evolution, quantum beats in the selective field ionization of Rydberg atoms have been observed. Here, we present a study exploring the effect of electric and magnetic fields on quantum beats. Beginning with a single excited state, a coherent superposition is created by a short electric field pulse in the presence of a static magnetic field. The resulting quantum beats are then observed in the field ionization spectrum. Additionally, millimeterwave spectroscopy is used to probe the state populations in this superposition. This work is supported by the National Science Foundation under Grants No. 1205895 and No. 1205897.

Classical and quantum mechanical motion in magnetic fields
NASA Astrophysics Data System (ADS)
Franklin, J.; Cole Newton, K.
20160401
We study the motion of a particle in a particular magnetic field configuration both classically and quantum mechanically. For fluxfree radially symmetric magnetic fields defined on circular regions, we establish that particle escape speeds depend, classically, on a gaugefixed magnetic vector potential, and we demonstrate some trajectories associated with this special type of magnetic field. Then we show that some of the geometric features of the classical trajectory (perpendicular exit from the field region, trapped and escape behavior) are reproduced quantum mechanically, using a numerical method that extends the normpreserving CrankNicolson method to problems involving magnetic fields. While there are similarities between the classical trajectory and the position expectation value of the quantummechanical solution, there are also differences, and we demonstrate some of these.

Classical and Quantum Mechanical Motion in Magnetic Fields
NASA Astrophysics Data System (ADS)
Newton, K. Cole; Franklin, Joel
20160301
We study the motion of a particle in a particular magnetic field configuration both classically and quantum mechanically. For fluxfree radially symmetric magnetic fields defined on circular regions, we establish that particle escape speeds depend, classically, on a gaugefixed magnetic vector potential, and demonstrate some trajectories associated with this special type of magnetic field. Then we show that some of the geometric features of the classical trajectory (perpendicular exit from the field region, trapped and escape behavior) are reproduced quantum mechanically using a numerical method that extends the normpreserving CrankNicolson method to problems involving magnetic fields. While there are similarities between the classical trajectory and the position expectation value of the quantum mechanical solution, there are also differences, and we demonstrate some of these.

Dirac fields in loop quantum gravity and big bang nucleosynthesis
SciTech Connect
Bojowald, Martin; Das, Rupam; Scherrer, Robert J.
20080415
Big bang nucleosynthesis requires a fine balance between equations of state for photons and relativistic fermions. Several corrections to equation of state parameters arise from classical and quantum physics, which are derived here from a canonical perspective. In particular, loop quantum gravity allows one to compute quantum gravity corrections for Maxwell and Dirac fields. Although the classical actions are very different, quantum corrections to the equation of state are remarkably similar. To lowest order, these corrections take the form of an overall expansiondependent multiplicative factor in the total density. We use these results, along with the predictions of big bang nucleosynthesis, to place bounds on these corrections and especially the patch size of discrete quantum gravity states.

QubitProgrammable Operations on Quantum Light Fields
PubMed Central
Barbieri, Marco; Spagnolo, Nicolò; Ferreyrol, Franck; Blandino, Rémi; Smith, Brian J.; TualleBrouri, Rosa
20150101
Engineering quantum operations is a crucial capability needed for developing quantum technologies and designing new fundamental physics tests. Here we propose a scheme for realising a controlled operation acting on a travelling continuousvariable quantum field, whose functioning is determined by a discrete input qubit. This opens a new avenue for exploiting advantages of both information encoding approaches. Furthermore, this approach allows for the program itself to be in a superposition of operations, and as a result it can be used within a quantum processor, where coherences must be maintained. Our study can find interest not only in general quantum state engineering and information protocols, but also details an interface between different physical platforms. Potential applications can be found in linking optical qubits to optical systems for which coupling is best described in terms of their continuous variables, such as optomechanical devices. PMID:26468614

Scattering bright solitons: Quantum versus meanfield behavior
NASA Astrophysics Data System (ADS)
Gertjerenken, Bettina; Billam, Thomas P.; Khaykovich, Lev; Weiss, Christoph
20120901
We investigate scattering bright solitons off a potential using both analytical and numerical methods. Our paper focuses on low kinetic energies for which differences between the meanfield description via the GrossPitaevskii equation (GPE) and the quantum behavior are particularly large. On the Nparticle quantum level, adding an additional harmonic confinement leads to a simple signature to distinguish quantum superpositions from statistical mixtures. While the nonlinear character of the GPE does not allow quantum superpositions, the splitting of GPE solitons takes place only partially. When the potential strength is increased, the fraction of the soliton which is transmitted or reflected jumps noncontinuously. We explain these jumps via energy conservation and interpret them as indications for quantum superpositions on the Nparticle level. On the GPE level, we also investigate the transition from this stepwise behavior to the continuous case.

QubitProgrammable Operations on Quantum Light Fields.
PubMed
Barbieri, Marco; Spagnolo, Nicolò; Ferreyrol, Franck; Blandino, Rémi; Smith, Brian J; TualleBrouri, Rosa
20150101
Engineering quantum operations is a crucial capability needed for developing quantum technologies and designing new fundamental physics tests. Here we propose a scheme for realising a controlled operation acting on a travelling continuousvariable quantum field, whose functioning is determined by a discrete input qubit. This opens a new avenue for exploiting advantages of both information encoding approaches. Furthermore, this approach allows for the program itself to be in a superposition of operations, and as a result it can be used within a quantum processor, where coherences must be maintained. Our study can find interest not only in general quantum state engineering and information protocols, but also details an interface between different physical platforms. Potential applications can be found in linking optical qubits to optical systems for which coupling is best described in terms of their continuous variables, such as optomechanical devices. PMID:26468614

QubitProgrammable Operations on Quantum Light Fields
NASA Astrophysics Data System (ADS)
Barbieri, Marco; Spagnolo, Nicolò; Ferreyrol, Franck; Blandino, Rémi; Smith, Brian J.; TualleBrouri, Rosa
20151001
Engineering quantum operations is a crucial capability needed for developing quantum technologies and designing new fundamental physics tests. Here we propose a scheme for realising a controlled operation acting on a travelling continuousvariable quantum field, whose functioning is determined by a discrete input qubit. This opens a new avenue for exploiting advantages of both information encoding approaches. Furthermore, this approach allows for the program itself to be in a superposition of operations, and as a result it can be used within a quantum processor, where coherences must be maintained. Our study can find interest not only in general quantum state engineering and information protocols, but also details an interface between different physical platforms. Potential applications can be found in linking optical qubits to optical systems for which coupling is best described in terms of their continuous variables, such as optomechanical devices.

Cosmology from group field theory formalism for quantum gravity.
PubMed
Gielen, Steffen; Oriti, Daniele; Sindoni, Lorenzo
20130719
We identify a class of condensate states in the group field theory (GFT) formulation of quantum gravity that can be interpreted as macroscopic homogeneous spatial geometries. We then extract the dynamics of such condensate states directly from the fundamental quantum GFT dynamics, following the procedure used in ordinary quantum fluids. The effective dynamics is a nonlinear and nonlocal extension of quantum cosmology. We also show that any GFT model with a kinetic term of Laplacian type gives rise, in a semiclassical (WKB) approximation and in the isotropic case, to a modified Friedmann equation. This is the first concrete, general procedure for extracting an effective cosmological dynamics directly from a fundamental theory of quantum geometry. PMID:23909305

Evolution of Quantum Fluctuations Near the Quantum Critical Point of the Transverse Field Ising Chain System CoNb2O6
NASA Astrophysics Data System (ADS)
Kinross, A. W.; Fu, M.; Munsie, T. J.; Dabkowska, H. A.; Luke, G. M.; Sachdev, Subir; Imai, T.
20140701
The transverse field Ising chain model is ideally suited for testing the fundamental ideas of quantum phase transitions because its wellknown T=0 ground state can be extrapolated to finite temperatures. Nonetheless, the lack of appropriate model materials hindered the past effort to test the theoretical predictions. Here, we map the evolution of quantum fluctuations in the transverse field Ising chain based on nuclear magnetic resonance measurements of CoNb2O6, and we demonstrate the finitetemperature effects on quantum criticality for the first time. From the temperature dependence of the Nb93 longitudinal relaxation rate 1/T1, we identify the renormalized classical, quantum critical, and quantum disordered scaling regimes in the temperature (T) vs transverse magnetic field (h ⊥) phase diagram. Precisely at the critical field h⊥c=5.25±0.15 T, we observe a powerlaw behavior, 1/T1˜T3/4, as predicted by quantum critical scaling. Our parameterfree comparison between the data and theory reveals that quantum fluctuations persist up to as high as T ˜0.4J, where the intrachain exchange interaction J is the only energy scale of the problem.

Quantum theory for plasmonassisted local field enhancement
NASA Astrophysics Data System (ADS)
Grigorenko, Ilya
20160101
We applied quantum theory for nonlocal response and plasmonassisted field enhancement near a small metallic nanoscale antenna in the limit of weak incoming fields. A simple asymmetric bioinspired design of the nanoantenna for polarizationresolved measurement is proposed. The spatial field intensity distribution was calculated for different field frequencies and polarizations. We have shown that the proposed design the antenna allows us to resolve the polarization of incoming photons.

Quantum theory for plasmonassisted local field enhancement
NASA Astrophysics Data System (ADS)
Grigorenko, Ilya
We applied quantum theory for nonlocal response and plasmonassisted field enhancement near a small metallic nanoscale antenna in the limit of weak incoming fields. A simple asymmetric bioinspired design of the nanoantenna for polarizationresolved measurement is proposed. The spatial field intensity distribution was calculated for different field frequencies and polarizations. We have shown that the proposed design the antenna allows us to resolve the polarization of incoming photons.

PREFACE: Particles and Fields: Classical and Quantum
NASA Astrophysics Data System (ADS)
Asorey, M.; ClementeGallardo, J.; Marmo, G.
20070701
This volume contains some of the contributions to the Conference Particles and Fields: Classical and Quantum, which was held at Jaca (Spain) in September 2006 to honour George Sudarshan on his 75th birthday. Former and current students, associates and friends came to Jaca to share a few wonderful days with George and his family and to present some contributions of their present work as influenced by George's impressive achievements. This book summarizes those scientific contributions which are presented as a modest homage to the master, collaborator and friend. At the social ceremonies various speakers were able to recall instances of his lifelong activity in India, the United States and Europe, adding colourful remarks on the friendly and intense atmosphere which surrounded those collaborations, some of which continued for several decades. This meeting would not have been possible without the financial support of several institutions. We are deeply indebted to Universidad de Zaragoza, Ministerio de Educación y Ciencia de España (CICYT), Departamento de Ciencia, Tecnología y Universidad del Gobierno de Aragón, Universitá di Napoli 'Federico II' and Istituto Nazionale di Fisica Nucleare. Finally, we would like to thank the participants, and particularly George's family, for their contribution to the wonderful atmosphere achieved during the Conference. We would like also to acknowledge the authors of the papers collected in the present volume, the members of the Scientific Committee for their guidance and support and the referees for their generous work. M Asorey, J ClementeGallardo and G Marmo The Local Organizing Committee George Sudarshan International Advisory Committee A. Ashtekhar (Pennsylvania State University, USA)  L. J. Boya (Universidad de Zaragoza, Spain)  I. Cirac (Max Planck Institute, Garching

Exact Green's function renormalization approach to spectral properties of open quantum systems driven by harmonically timedependent fields
NASA Astrophysics Data System (ADS)
Arrachea, Liliana
20070101
We present an efficient method and a fast algorithm to exactly calculate spectral functions and onebody observables of open quantum systems described by lattice Hamiltonians with harmonically timedependent terms and without manybody interactions. The theoretical treatment is based in Keldysh nonequilibrium Green’s function formalism. We illustrate the implementation of the technique in a paradigmatic model of a quantum pump driven by local fields oscillating in time with one and two harmonic components.

Aspects of nonlocality in quantum field theory, quantum gravity and cosmology
NASA Astrophysics Data System (ADS)
Barvinsky, A. O.
20150101
This paper contains a collection of essays on nonlocal phenomena in quantum field theory, gravity and cosmology. Mechanisms of nonlocal contributions to the quantum effective action are discussed within the covariant perturbation expansion in field strengths and spacetime curvatures. Euclidean version of the SchwingerKeldysh technique for quantum expectation values is presented as a special rule of obtaining the nonlocal effective equations of motion for the mean quantum field from the Euclidean effective action. This rule is applied to a new model of ghost free nonlocal cosmology which can generate the de Sitter (dS) cosmological evolution at an arbitrary value of Λ — a model of dark energy with the dynamical scale selected by a kind of a scaling symmetry breaking mechanism. This model is shown to interpolate between the superhorizon phase of a scalar mediated gravity and the short distance general relativistic limit in a special metric frame related by a nonlocal conformal transformation to the original metric.

Quantum de Finetti theorems and meanfield theory from quantum phase space representations
NASA Astrophysics Data System (ADS)
Trimborn, F.; Werner, R. F.; Witthaut, D.
20160401
We introduce the numberconserving quantum phase space description as a versatile tool to address fundamental aspects of quantum manybody systems. Using phase space methods we prove two alternative versions of the quantum de Finetti theorem for finitedimensional bosonic quantum systems, which states that a reduced density matrix of a manybody quantum state can be approximated by a convex combination of product states where the error is proportional to the inverse particle number. This theorem provides a formal justification for the meanfield description of manybody quantum systems, as it shows that quantum correlations can be neglected for the calculation of fewbody observables when the particle number is large. Furthermore we discuss methods to derive the exact evolution equations for quantum phase space distribution functions as well as upper and lower bounds for the ground state energy. As an important example, we consider the BoseHubbard model and show that the meanfield dynamics is given by a classical phase space flow equivalent to the discrete GrossPitaevskii equation.

Chameleon fields, wave function collapse and quantum gravity
NASA Astrophysics Data System (ADS)
Zanzi, A.
20150701
Chameleon fields are quantum (usually scalar) fields, with a densitydependent mass. In a highdensity environment, the mass of the chameleon is large. On the contrary, in a smalldensity environment (e.g. on cosmological distances), the chameleon is very light. A model where the collapse of the wave function is induced by chameleon fields is presented. During this analysis, a Chameleonic Equivalence Principle (CEP) will be formulated: in this model, quantum gravitation is equivalent to a conformal anomaly. Further research efforts are necessary to verify whether this proposal is compatible with phenomeno logical constraints.

Lecture Notes on Interacting Quantum Fields in de Sitter Space
NASA Astrophysics Data System (ADS)
Akhmedov, E. T.
20130901
We discuss peculiarities of quantum fields in de Sitter (dS) space on the example of the selfinteracting massive real scalar, minimally coupled to the gravity background. Nonconformal quantum field theories (QFTs) in dS space show very special infrared behavior, which is not shared by quantum fields neither in flat nor in antidS space: in dS space loops are not suppressed in comparison with tree level contributions because there are strong infrared corrections. That is true even for massive fields. Our main concern is the interrelation between these infrared effects, the invariance of the QFT under the dS isometry and the (in)stability of dS invariant states (and of dS space itself) under nonsymmetric perturbations.

Lecture Notes on Interacting Quantum Fields in de Sitter Space
NASA Astrophysics Data System (ADS)
Akhmedov, E. T.
20141001
We discuss peculiarities of quantum fields in de Sitter (dS) space on the example of the selfinteracting massive real scalar, minimally coupled to the gravity background. Nonconformal quantum field theories (QFTs) in dS space show very special infrared behavior, which is not shared by quantum fields neither in flat nor in antidS space: in dS space loops are not suppressed in comparison with tree level contributions because there are strong infrared corrections. That is true even for massive fields. Our main concern is the interrelation between these infrared effects, the invariance of the QFT under the dS isometry and the (in)stability of dS invariant states (and of dS space itself) under nonsymmetric perturbations.

Theoretical study of polarization insensitivity of carrierinduced refractive index change of multiple quantum well.
PubMed
Miao, Qingyuan; Zhou, Qunjie; Cui, Jun; He, PingAn; Huang, Dexiu
20141229
Characteristics of polarization insensitivity of carrierinduced refractive index change of 1.55 μm tensilestrained multiple quantum well (MQW) are theoretically investigated. A comprehensive MQW model is proposed to effectively extend the application range of previous models. The model considers the temperature variation as well as the nonuniform distribution of injected carrier in MQW. Tensilestrained MQW is expected to achieve polarization insensitivity of carrierinduced refractive index change over a wide wavelength range as temperature varies from 0°C to 40°C, while the magnitude of refractive index change keeps a large value (more than 3 × 10^{3}). And that the polarization insensitivity of refractive index change can maintain for a wide range of carrier concentration. Multiple quantum well with different material and structure parameters is anticipated to have the similar polarization insensitivity of refractive index change, which shows the design flexibility. PMID:25607157

A novel quantum field approach to photoexcited insulators
NASA Astrophysics Data System (ADS)
Klotins, E.
20160701
In order to predict optical properties of insulating materials under intensive laser excitation, we generalized methods of quantum electrodynamics, allowing us to simulate excitation of electrons and holes, interacting with each other and acoustic phonons. The prototypical model considers a twoband dielectric material characterized by the dispersion relations for electron and hole states. We developed a universal description of excited electrons, holes and acoustic phonons within joint quantum kinetics formalism. Illustrative solutions for the quasiparticle birthannihilation operators, applicable at short laser pulses at 0 K, are obtained by the transition from the macroscopic description to the quantum field formalism.

Quantum field between moving mirrors: A three dimensional example
NASA Technical Reports Server (NTRS)
Hacyan, S.; Jauregui, Roco; Villarreal, Carlos
19950101
The scalar quantum field uniformly moving plates in three dimensional space is studied. Field equations for Dirichlet boundary conditions are solved exactly. Comparison of the resulting wavefunctions with their instantaneous static counterpart is performed via Bogolubov coefficients. Unlike the one dimensional problem, 'particle' creation as well as squeezing may occur. The time dependent Casimir energy is also evaluated.

Quantum electrodynamics in finite volume and nonrelativistic effective field theories
NASA Astrophysics Data System (ADS)
Fodor, Z.; Hoelbling, C.; Katz, S. D.; Lellouch, L.; Portelli, A.; Szabo, K. K.; Toth, B. C.
20160401
Electromagnetic effects are increasingly being accounted for in lattice quantum chromodynamics computations. Because of their longrange nature, they lead to large finitesize effects over which it is important to gain analytical control. Nonrelativistic effective field theories provide an efficient tool to describe these effects. Here we argue that some care has to be taken when applying these methods to quantum electrodynamics in a finite volume.

BOOK REVIEW: Classical Solutions in Quantum Field Theory Classical Solutions in Quantum Field Theory
NASA Astrophysics Data System (ADS)
Mann, Robert
20130201
Quantum field theory has evolved from its early beginnings as a tool for understanding the interaction of light with matter into a rather formidable technical paradigm, one that has successfully provided the mathematical underpinnings of all nongravitational interactions. Over the eight decades since it was first contemplated the methods have become increasingly more streamlined and sophisticated, yielding new insights into our understanding of the subatomic world and our abilities to make clear and precise predictions. Some of the more elegant methods have to do with nonperturbative and semiclassical approaches to the subject. The chief players here are solitons, instantons, and anomalies. Over the past three decades there has been a steady rise in our understanding of these objects and of our ability to calculate their effects and implications for the rest of quantum field theory. This book is a welcome contribution to this subject. In 12 chapters it provides a clear synthesis of the key developments in these subjects at a level accessible to graduate students that have had an introductory course to quantum field theory. In the author's own words it provides both 'a survey and an overview of this field'. The first half of the book concentrates on solitonskinks, vortices, and magnetic monopolesand their implications for the subject. The reader is led first through the simplest models in one spatial dimension, into more sophisticated cases that required more advanced topological methods. The author does quite a nice job of introducing the various concepts as required, and beginning students should be able to get a good grasp of the subject directly from the text without having to first go through the primary literature. The middle part of the book deals with the implications of these solitons for both cosmology and for duality. While the cosmological discussion is quite nice, the discussion on BPS solitons, supersymmetry and duality is rather condensed. It is

Quantum simulation
NASA Astrophysics Data System (ADS)
Georgescu, I. M.; Ashhab, S.; Nori, Franco
20140101
Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensedmatter physics, highenergy physics, atomic physics, quantum chemistry, and cosmology. Quantum simulation could be implemented using quantum computers, but also with simpler, analog devices that would require less control, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar molecules, electrons in semiconductors, superconducting circuits, nuclear spins, and photons have been proposed as quantum simulators. This review outlines the main theoretical and experimental aspects of quantum simulation and emphasizes some of the challenges and promises of this fastgrowing field.

Theoretical and experimental studies of (In,Ga)As/GaP quantum dots
PubMed Central
20120101
(In,Ga)As/GaP(001) quantum dots (QDs) are grown by molecular beam epitaxy and studied both theoretically and experimentally. The electronic band structure is simulated using a combination of k·p and tightbinding models. These calculations predict an indirect to direct crossover with the In content and the size of the QDs. The optical properties are then studied in a lowIncontent range through photoluminescence and timeresolved photoluminescence experiments. It suggests the proximity of two optical transitions of indirect and direct types. PMID:23176537

Control of the entanglement between triple quantum dot molecule and its spontaneous emission fields via quantum entropy
NASA Astrophysics Data System (ADS)
Sahrai, M.; Arzhang, B.; Taherkhani, D.; Boroojerdi, V. Tahmoorian Askari
20150301
The time evolution of the quantum entropy in a coherently driven triple quantum dot molecule is investigated. The entanglement of the quantum dot molecule and its spontaneous emission field is coherently controlled by the gate voltage and the rate of an incoherent pump field. The degree of entanglement between a triple quantum dot molecule and its spontaneous emission fields is decreased by increasing the tunneling parameter.

Effect of magnetic field on electron spectrum and probabilities of intraband quantum transitions in spherical quantumdotquantumwell
NASA Astrophysics Data System (ADS)
Holovatsky, V.; Bernik, I.; Yakhnevych, M.
20160901
The effect of magnetic field on electron energy spectrum, wave functions and probabilities of intraband quantum transitions in multilayered spherical quantumdotquantumwell (QDQW) CdSe/ZnS/CdSe/ZnS is studied. Computations are performed in the framework of the effective mass approximation and rectangular potential barriers model. The wave functions are expanded over the complete basis of functions obtained as exact solutions of the Schrodinger equation for the electron in QDQW without the magnetic field. It is shown that magnetic field takes off the spectrum degeneration with respect to the magnetic quantum number and changes the localization of electron in the nanostructure. The field stronger effects on the sphericallysymmetric states, especially in the case of electron location in the outer potential well. The magnetic field changes more the radial distribution of probability of electron location in QDQW than the angular one. The oscillator strengths of intraband quantum transitions are calculated as functions of the magnetic field induction and their selection rules are established.

A combined experimental and theoretical quantum chemical studies on 4morpholinecarboxaldehyde
NASA Astrophysics Data System (ADS)
Arjunan, V.; Rani, T.; Santhanalakshmi, K.; Mohan, S.
20110901
Extensive spectroscopic investigations have been carried out by recording the Fourier transform infrared (FTIR) and FTRaman spectra and carrying out the theoretical quantum chemical studies on 4morpholinecarboxaldehyde (4MC). From the ab initio and DFT analysis using HF, B3LYP and B3PW91 methods with 631G(d,p) and 6311G++(d,p) basis sets the energies, structural, thermodynamical and vibrational characteristics of the compound were determined. The energy difference between the chair equatorial and chair axial conformers of 4MC have been calculated by density functional theory (DFT) method. The optimised geometrical parameters, theoretical wavenumbers and thermodynamic properties of the molecule were compared with the experimental values. The effect of carbonyl group on the characteristic frequencies of the morpholine ring has been analysed. The mixing of the fundamental modes with the help of potential energy distribution (PED) through normal coordinate analysis has been discussed.

IR photodetector based on rectangular quantum wire in magnetic field
SciTech Connect
Jha, Nandan
20140424
In this paper we study rectangular quantum wire based IR detector with magnetic field applied along the wires. The energy spectrum of a particle in rectangular box shows level repulsions and crossings when external magnetic field is applied. Due to this complex level dynamics, we can tune the spacing between any two levels by varying the magnetic field. This method allows user to change the detector parameters according to his/her requirements. In this paper, we numerically calculate the energy subband levels of the square quantum wire in constant magnetic field along the wire and quantify the possible operating wavelength range that can be obtained by varying the magnetic field. We also calculate the photon absorption probability at different magnetic fields and give the efficiency for different wavelengths if the transition is assumed between two lowest levels.

Lorentz symmetry breaking as a quantum field theory regulator
SciTech Connect
Visser, Matt
20090715
Perturbative expansions of quantum field theories typically lead to ultraviolet (shortdistance) divergences requiring regularization and renormalization. Many different regularization techniques have been developed over the years, but most regularizations require severe mutilation of the logical foundations of the theory. In contrast, breaking Lorentz invariance, while it is certainly a radical step, at least does not damage the logical foundations of the theory. I shall explore the features of a Lorentz symmetry breaking regulator in a simple polynomial scalar field theory and discuss its implications. In particular, I shall quantify just 'how much' Lorentz symmetry breaking is required to fully regulate the quantum theory and render it finite. This scalar field theory provides a simple way of understanding many of the key features of Horava's recent article [Phys. Rev. D 79, 084008 (2009)] on 3+1 dimensional quantum gravity.

Lorentz symmetry breaking as a quantum field theory regulator
NASA Astrophysics Data System (ADS)
Visser, Matt
20090701
Perturbative expansions of quantum field theories typically lead to ultraviolet (shortdistance) divergences requiring regularization and renormalization. Many different regularization techniques have been developed over the years, but most regularizations require severe mutilation of the logical foundations of the theory. In contrast, breaking Lorentz invariance, while it is certainly a radical step, at least does not damage the logical foundations of the theory. I shall explore the features of a Lorentz symmetry breaking regulator in a simple polynomial scalar field theory and discuss its implications. In particular, I shall quantify just “how much” Lorentz symmetry breaking is required to fully regulate the quantum theory and render it finite. This scalar field theory provides a simple way of understanding many of the key features of Hořava’s recent article [Phys. Rev. DPRVDAQ15507998 79, 084008 (2009)10.1103/PhysRevD.79.084008] on 3+1 dimensional quantum gravity.

Quantum capacitance oscillations in graphene under crossed magnetic and electric fields
NASA Astrophysics Data System (ADS)
Alisultanov, Z. Z.; Reis, M. S.
20160101
Quantum oscillations of metallic systems at low temperatures are one of the key rules to experimentally access their electronic properties, such as energy spectrum, scattering mechanisms, geometry of Fermi surface and many other features. The importance of these knowledge is enormous, since from these a thorough understanding of the anomalous Hall effect, thermopower and Nernst coefficients, just to name a few, is possible; and from those knowledge, plenty of applications arise as emerging technologies. In this direction, the present contribution focuses on a complete description of quantum capacitance oscillations of monolayer and bilayer graphene under crossed electric and magnetic fields, considering to this purpose the LifshitzOnsager quantization condition. We found a closed theoretical expression for the quantum capacitance and highlight their amplitude, period and phase —important parameters to access the electronic properties of graphene. These results open doors for further experimental studies.

Dynamical renormalization group approach to relaxation in quantum field theory
NASA Astrophysics Data System (ADS)
Boyanovsky, D.; de Vega, H. J.
20031001
The real time evolution and relaxation of expectation values of quantum fields and of quantum states are computed as initial value problems by implementing the dynamical renormalization group (DRG). Linear response is invoked to set up the renormalized initial value problem to study the dynamics of the expectation value of quantum fields. The perturbative solution of the equations of motion for the field expectation values of quantum fields as well as the evolution of quantum states features secular terms, namely terms that grow in time and invalidate the perturbative expansion for late times. The DRG provides a consistent framework to resum these secular terms and yields a uniform asymptotic expansion at long times. Several relevant cases are studied in detail, including those of threshold infrared divergences which appear in gauge theories at finite temperature and lead to anomalous relaxation. In these cases the DRG is shown to provide a resummation akin to BlochNordsieck but directly in real time and that goes beyond the scope of BlochNordsieck and Dyson resummations. The nature of the resummation program is discussed in several examples. The DRG provides a framework that is consistent, systematic, and easy to implement to study the nonequilibrium relaxational dynamics directly in real time that does not rely on the concept of quasiparticle widths.

Reality, Causality, and Probability, from Quantum Mechanics to Quantum Field Theory
NASA Astrophysics Data System (ADS)
Plotnitsky, Arkady
20151001
These three lectures consider the questions of reality, causality, and probability in quantum theory, from quantum mechanics to quantum field theory. They do so in part by exploring the ideas of the key founding figures of the theory, such N. Bohr, W. Heisenberg, E. Schrödinger, or P. A. M. Dirac. However, while my discussion of these figures aims to be faithful to their thinking and writings, and while these lectures are motivated by my belief in the helpfulness of their thinking for understanding and advancing quantum theory, this project is not driven by loyalty to their ideas. In part for that reason, these lectures also present different and even conflicting ways of thinking in quantum theory, such as that of Bohr or Heisenberg vs. that of Schrödinger. The lectures, most especially the third one, also consider new physical, mathematical, and philosophical complexities brought in by quantum field theory visàvis quantum mechanics. I close by briefly addressing some of the implications of the argument presented here for the current state of fundamental physics.

Plasma wave instability in a quantum field effect transistor with magnetic field effect
SciTech Connect
Zhang, LiPing; Xue, JuKui
20130815
The currentcarrying state of a nanometer Field Effect Transistor (FET) may become unstable against the generation of highfrequency plasma waves and lead to generation of terahertz radiation. In this paper, the influences of magnetic field, quantum effects, electron exchangecorrelation, and thermal motion of electrons on the instability of the plasma waves in a nanometer FET are reported. We find that, while the electron exchangecorrelation suppresses the radiation power, the magnetic field, the quantum effects, and the thermal motion of electrons can enhance the radiation power. The radiation frequency increases with quantum effects and thermal motion of electrons, but decreases with electron exchangecorrelation effect. Interestingly, we find that magnetic field can suppress the quantum effects and the thermal motion of electrons and the radiation frequency changes nonmonotonely with the magnetic field. These properties could make the nanometer FET advantageous for realization of practical terahertz oscillations.

Effects of a scalar scaling field on quantum mechanics
NASA Astrophysics Data System (ADS)
Benioff, Paul
20160701
This paper describes the effects of a complex scalar scaling field on quantum mechanics. The field origin is an extension of the gauge freedom for basis choice in gauge theories to the underlying scalar field. The extension is based on the idea that the value of a number at one space time point does not determine the value at another point. This, combined with the description of mathematical systems as structures of different types, results in the presence of separate number fields and vector spaces as structures, at different space time locations. Complex number structures and vector spaces at each location are scaled by a complex space time dependent scaling factor. The effect of this scaling factor on several physical and geometric quantities has been described in other work. Here the emphasis is on quantum mechanics of one and two particles, their states and properties. Multiparticle states are also briefly described. The effect shows as a complex, nonunitary, scalar field connection on a fiber bundle description of nonrelativistic quantum mechanics. The lack of physical evidence for the presence of this field so far means that the coupling constant of this field to fermions is very small. It also means that the gradient of the field must be very small in a local region of cosmological space and time. Outside this region, there are no restrictions on the field gradient.

Effects of a scalar scaling field on quantum mechanics
NASA Astrophysics Data System (ADS)
Benioff, Paul
20160401
This paper describes the effects of a complex scalar scaling field on quantum mechanics. The field origin is an extension of the gauge freedom for basis choice in gauge theories to the underlying scalar field. The extension is based on the idea that the value of a number at one space time point does not determine the value at another point. This, combined with the description of mathematical systems as structures of different types, results in the presence of separate number fields and vector spaces as structures, at different space time locations. Complex number structures and vector spaces at each location are scaled by a complex space time dependent scaling factor. The effect of this scaling factor on several physical and geometric quantities has been described in other work. Here the emphasis is on quantum mechanics of one and two particles, their states and properties. Multiparticle states are also briefly described. The effect shows as a complex, nonunitary, scalar field connection on a fiber bundle description of nonrelativistic quantum mechanics. The lack of physical evidence for the presence of this field so far means that the coupling constant of this field to fermions is very small. It also means that the gradient of the field must be very small in a local region of cosmological space and time. Outside this region, there are no restrictions on the field gradient.

Mirror moving in quantum vacuum of a massive scalar field
NASA Astrophysics Data System (ADS)
Wang, Qingdi; Unruh, William G.
20150901
We present a mirror model moving in the quantum vacuum of a massive scalar field and study its motion under infinitely fluctuating quantum vacuum stress. The model is similar to the one in [Q. Wang and W. G. Unruh, Motion of a mirror under infinitely fluctuating quantum vacuum stress Phys. Rev. D 89, 085009 (2014).], but this time there is no divergent effective mass to weaken the effect of divergent vacuum energy density. We show that this kind of weakening is not necessary. The vacuum friction and strong anticorrelation property of the quantum vacuum are enough to confine the mirror's position fluctuations. This is another example illustrating that while the actual value of the vacuum energy can be physically significant even for a nongravitational system, and that its infinite value makes sense, but that its physical effect can be small despite this infinity.

Ionisation of a quantum dot by electric fields
SciTech Connect
Eminov, P A; Gordeeva, S V
20120831
We have derived analytical formulas for differential and total ionisation probabilities of a twodimensional quantum dot by a constant electric field. In the adiabatic approximation, we have calculated the probability of this process in the field of a plane electromagnetic wave and in a superposition of constant and alternating electric fields. The imaginarytime method is used to obtain the momentum distribution of the ionisation probability of a bound system by an intense field generated by a superposition of parallel constant and alternating electric fields. The total probability of the process per unit time is calculated with exponential accuracy. The dependence of the results obtained on the characteristic parameters of the problem is investigated. (laser applications and other topics in quantum electronics)

Quantum field theory in spaces with closed timelike curves
NASA Astrophysics Data System (ADS)
Boulware, David G.
19921101
Gott spacetime has closed timelike curves, but no locally anomalous stress energy. A complete orthonormal set of eigenfunctions of the wave operator is found in the special case of a spacetime in which the total deficit angle is 2π. A scalar quantum field theory is constructed using these eigenfunctions. The resultant interacting quantum field theory is not unitary because the field operators can create real, onshell, particles in the noncausal region. These particles propagate for finite proper time accumulating an arbitrary phase before being annihilated at the same spacetime point as that at which they were created. As a result, the effective potential within the noncausal region is complex, and probability is not conserved. The stress tensor of the scalar field is evaluated in the neighborhood of the Cauchy horizon; in the case of a sufficiently small Compton wavelength of the field, the stress tensor is regular and cannot prevent the formation of the Cauchy horizon.

A molecularfield approximation for quantum crystals. Ph.D. Thesis; [considering ground state properties
NASA Technical Reports Server (NTRS)
Danilowicz, R.
19730101
Groundstate properties of quantum crystals have received considerable attention from both theorists and experimentalists. The theoretical results have varied widely with the Monte Carlo calculations being the most successful. The molecular field approximation yields groundstate properties which agree closely with the Monte Carlo results. This approach evaluates the dynamical behavior of each pair of molecules in the molecular field of the other N2 molecules. In addition to predicting groundstate properties that agree well with experiment, this approach yields data on the relative importance of interactions of different nearest neighbor pairs.

Quantum ring solitons and nonlocal effects in plasma wake field excitations
SciTech Connect
Fedele, R.; Tanjia, F.; De Nicola, S.; Jovanovic, D.; Shukla, P. K.
20121015
A theoretical investigation of the quantum transverse beam motion for a cold relativistic charged particle beam travelling in a cold, collisionless, strongly magnetized plasma is carried out. This is done by taking into account both the individual quantum nature of the beam particles (singleparticle uncertainty relations and spin) and the self consistent interaction generated by the plasma wake field excitation. By adopting a fluid model of a strongly magnetized plasma, the analysis is carried out in the overdense regime (dilute beams) and in the long beam limit. It is shown that the quantum description of the collective transverse beam dynamics is provided by a pair of coupled nonlinear governing equations. It comprises a Poissonlike equation for the plasma wake potential (driven by the beam density) and a 2D spinorial Schroedinger equation for the wave function, whose squared modulus is proportional to the beam density, that is obtained in the Hartree's mean field approximation, after disregarding the exchange interactions. The analysis of this pair of equations, which in general exhibits a strong nonlocal character, is carried out analytically as well as numerically in both the linear and the nonlinear regimes, showing the existence of the quantum beam vortices in the form of LaguerreGauss modes and ring envelope solitons, respectively. In particular, when the relation between the plasma wake field response and the beam probability density is strictly local, the pair of the governing equations is reduced to the 2D GrossPitaevskii equation that allows one to establish the conditions for the self focusing and collapse. These conditions include the quantum nature of the beam particles. Finally, when the relation between the plasma wake field response and the beam probability density is moderately nonlocal, the above pair of equations permits to follow the spatiotemporal evolution of a quantum ring envelope soliton. Such a structure exhibits small or violent

Toward a quantum theory of tachyon fields
NASA Astrophysics Data System (ADS)
Schwartz, Charles
20160301
We construct momentum space expansions for the wave functions that solve the KleinGordon and Dirac equations for tachyons, recognizing that the mass shell for such fields is very different from what we are used to for ordinary (slower than light) particles. We find that we can postulate commutation or anticommutation rules for the operators that lead to physically sensible results: causality, for tachyon fields, means that there is no connection between spacetime points separated by a timelike interval. Calculating the conserved charge and fourmomentum for these fields allows us to interpret the number operators for particles and antiparticles in a consistent manner; and we see that helicity plays a critical role for the spinor field. Some questions about Lorentz invariance are addressed and some remain unresolved; and we show how to handle the group representation for tachyon spinors.

Acceleration of adiabatic quantum dynamics in electromagnetic fields
SciTech Connect
Masuda, Shumpei; Nakamura, Katsuhiro
20111015
We show a method to accelerate quantum adiabatic dynamics of wave functions under electromagnetic field (EMF) by developing the preceding theory [Masuda and Nakamura, Proc. R. Soc. London Ser. A 466, 1135 (2010)]. Treating the orbital dynamics of a charged particle in EMF, we derive the driving field which accelerates quantum adiabatic dynamics in order to obtain the final adiabatic states in any desired short time. The scheme is consolidated by describing a way to overcome possible singularities in both the additional phase and driving potential due to nodes proper to wave functions under EMF. As explicit examples, we exhibit the fast forward of adiabatic squeezing and transport of excited Landau states with nonzero angular momentum, obtaining the result consistent with the transitionless quantum driving applied to the orbital dynamics in EMF.

A condensed matter field theory for quantum plasmonics
NASA Astrophysics Data System (ADS)
Ballout, Fouad; Hess, Ortwin
In recent years plasmonics has advanced to ever decreasing length scales reaching dimensions comparable to the de broglie wavelength of an electron, which has a manifest influence on the plasmon dispersion relation. The associated phenomenology lies beyond the reach of the classical drude free electron theory or its nonlocal extension and adequate models are needed to address the quantum matter aspects of lightmatter interaction that are responsible for plasmonicquantum size effects. We present on the basis of the jellium model a quantum field theory of surfaceplasmon polaritons in which they emerge as extended objects as a result of an inhomogeneous condensation of bosons around a topological singularity describing the surface. The benefit of this approach lies in relating the electromagnetic fields belonging to such a macroscopic quantum state with the surface topology and nonlocal responsefunction (expressed in terms of the retarded photon selfenergy) of the delimited electron gas sustaining that state.

Quantum synchrotron spectra from semirelativistic electrons in teragauss magnetic fields
NASA Technical Reports Server (NTRS)
Brainerd, J. J.
19870101
Synchrotron spectra are calculated from quantum electrodynamic transition rates for thermal and powerlaw electron distributions. It is shown that quantum effects appear in thermal spectra when the photon energy is greater than the electron temperature, and in powerlaw spectra when the electron energy in units of the electron rest mass times the magnetic field strength in units of the critical field strength is of order unity. These spectra are compared with spectra calculated from the ultrarelativistic approximation for synchrotron emission. It is found that the approximation for the powerlaw spectra is good, and the approximation for thermal spectra produces the shape of the spectrum accurately but fails to give the correct normalization. Single photon pair creation masks the quantum effects for powerlaw distributions, so only modifications to thermal spectra are important for gammaray bursts.

Orbital effect, subband depopulation, and conductance fluctuations in ballistic quantum dots under a tilted magnetic field
NASA Astrophysics Data System (ADS)
Gustin, C.; Faniel, S.; Hackens, B.; Melinte, S.; Shayegan, M.; Bayot, V.
20050401
Using twodimensional electron gases (2DEGs) confined to wide and narrow quantum wells, we study the magnetoconductance of ballistic quantum dots as a function of the well width and the tilt angle of the magnetic field B with respect to the 2DEG. Both the wide and narrow quantum well dots feature magnetoconductance fluctuations (MCFs) at intermediate tilt angles, due to the finite thickness of the electron layer and the fieldinduced orbital effect. As B approaches a strictly parallel configuration, a saturation of the MCFs’ spectral distribution is observed, combined with the persistence of a limited number of frequency components in the case of the narrow quantum well dot. It is found that the onset of saturation strongly depends on the width of the confining well. Using the results of selfconsistent PoissonSchrödinger simulations, the magnetoconductance is rescaled as a function of the Fermi level in the 2DEG. We perform a power spectrum analysis of the parallel fieldinduced MCFs in the energy space and find a good agreement with theoretical predictions.

Is there a weak mixed polarity background field? Theoretical arguments
NASA Technical Reports Server (NTRS)
Spruit, H. C.; Title, A. M.; Van Ballegooijen, A. A.
19870101
A number of processes associated with the formation of active regions produce 'Uloops': fluxtubes having two ends at the photosphere but otherwise still embedded in the convection zone. The mass trapped on the field lines of such loops makes them behave in a qualitatively different way from the 'omegaloops' that form active regions. It is shown that Uloops will disperse though the convection zone and form a weak (down to a few gauss) field that covers a significant fraction of the solar surface. This field is tentatively identified with the innernetwork fields observed at Kitt Peak and Big Bear. The process by which these fields escape through the surface is described; a remarkable property is that it can make active region fields apparently disappear in situ. The mixed polarity moving magnetic features near sunspots are interpreted as a locally intense form of this disappearance by escape of Uloops.

Generating functionals for quantum field theories with random potentials
NASA Astrophysics Data System (ADS)
Jain, Mudit; Vanchurin, Vitaly
20160101
We consider generating functionals for computing correlators in quantum field theories with random potentials. Examples of such theories include cosmological systems in context of the string theory landscape (e.g. cosmic inflation) or condensed matter systems with quenched disorder (e.g. spin glass). We use the socalled replica trick to define two different generating functionals for calculating correlators of the quantum fields averaged over a given distribution of random potentials. The first generating functional is appropriate for calculating averaged (inout) amplitudes and involves a single replica of fields, but the replica limit is taken to an (unphysical) negative one number of fields outside of the path integral. When the number of replicas is doubled the generating functional can also be used for calculating averaged probabilities (squared amplitudes) using the inin construction. The second generating functional involves an infinite number of replicas, but can be used for calculating both inout and inin correlators and the replica limits are taken to only a zero number of fields. We discuss the formalism in details for a single real scalar field, but the generalization to more fields or to different types of fields is straightforward. We work out three examples: one where the mass of scalar field is treated as a random variable and two where the functional form of interactions is random, one described by a Gaussian random field and the other by a Euclidean action in the field configuration space.

Effective field theory out of equilibrium: Brownian quantum fields
NASA Astrophysics Data System (ADS)
Boyanovsky, D.
20150601
The emergence of an effective field theory out of equilibrium is studied in the case in which a light field—the system—interacts with very heavy fields in a finite temperature bath. We obtain the reduced density matrix for the light field, its time evolution is determined by an effective action that includes the influence action from correlations of the heavy degrees of freedom. The nonequilibrium effective field theory yields a Langevin equation of motion for the light field in terms of dissipative and noise kernels that obey a generalized fluctuation dissipation relation. These are completely determined by the spectral density of the bath which is analyzed in detail for several cases. At T = 0 we elucidate the effect of thresholds in the renormalization aspects and the asymptotic emergence of a local effective field theory with unitary time evolution. At T\

Perturbative quantum gravity in double field theory
NASA Astrophysics Data System (ADS)
Boels, Rutger H.; Horst, Christoph
20160401
We study perturbative general relativity with a twoform 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 ghostlike 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 onshell recursion, we can show that most of the Ddimensional tree level Smatrix 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 offshell cancellations in the Feynman graphs. As a straightforward application of the developed technology double field theorylike expressions for four field string corrections are derived.

The successful merger of theoretical thermochemistry with fragmentbased methods in quantum chemistry.
PubMed
Ramabhadran, Raghunath O; Raghavachari, Krishnan
20141216
CONSPECTUS: Quantum chemistry and electronic structure theory have proven to be essential tools to the experimental chemist, in terms of both a priori predictions that pave the way for designing new experiments and rationalizing experimental observations a posteriori. Translating the wellestablished success of electronic structure theory in obtaining the structures and energies of small chemical systems to increasingly larger molecules is an exciting and ongoing central theme of research in quantum chemistry. However, the prohibitive computational scaling of highly accurate ab initio electronic structure methods poses a fundamental challenge to this research endeavor. This scenario necessitates an indirect fragmentbased approach wherein a large molecule is divided into small fragments and is subsequently reassembled to compute its energy accurately. In our quest to further reduce the computational expense associated with the fragmentbased methods and overall enhance the applicability of electronic structure methods to large molecules, we realized that the broad ideas involved in a different area, theoretical thermochemistry, are transferable to the area of fragmentbased methods. This Account focuses on the effective merger of these two disparate frontiers in quantum chemistry and how new concepts inspired by theoretical thermochemistry significantly reduce the total number of electronic structure calculations needed to be performed as part of a fragmentbased method without any appreciable loss of accuracy. Throughout, the generalized connectivity based hierarchy (CBH), which we developed to solve a longstanding problem in theoretical thermochemistry, serves as the linchpin in this merger. The accuracy of our method is based on two strong foundations: (a) the apt utilization of systematic and sophisticated errorcanceling schemes via CBH that result in an optimal cutting scheme at any given level of fragmentation and (b) the use of a less expensive second

Wavefunction dynamics in a quantumdot electron pump under a high magnetic field
NASA Astrophysics Data System (ADS)
Ryu, Sungguen; Kataoka, Masaya; Sim, HeungSun
20150301
A quantumdot electron pump, formed and operated by applying timedependent potential barriers to a two dimensional electron gas system, provides a promising redefinition of ampere. The pump operation consists of capturing an electron from a reservoir into a quantum dot and ejecting it to another reservoir. The capturing process has been theoretically understood by a semiclassical treatment of the tunneling between the dot and reservoir. But the dynamics of the wavefunction of the captured electron in the ejection process has not been theoretically addressed, although it is useful for enhancing pump accuracy and for utilizing the pump as a singleelectron source for mesoscopic quantum electron devices. We study the dynamics under a strong magnetic field that leads to magnetic confinement of the captured electron, which dominates over the electrostatic confinement of the dot. We find that the wave packet of the captured electron has the Gaussian form with the width determined by the strength of the magnetic field, and that the time evolution of the packet follows the classical drift motion, with maintaining the Gaussian form. We discuss the possible signatures of the wave packet dynamics in experiments.

Towards a quantum field theory of primitive string fields
SciTech Connect
Ruehl, W.
20121015
We denote generating functions of massless even higherspin fields 'primitive string fields' (PSF's). In an introduction we present the necessary definitions and derive propagators and currents of these PDF's on flat space. Their offshell cubic interaction can be derived after all offshell cubic interactions of triplets of higherspin fields have become known. Then we discuss fourpoint functions of any quartet of PSF's. In subsequent sections we exploit the fact that higherspin field theories in AdS{sub d+1} are determined by AdS/CFT correspondence from universality classes of critical systems in ddimensional flat spaces. The O(N) invariant sectors of the O(N) vector models for 1 {<=} N {<=}{infinity} play for us the role of 'standard models', for varying N, they contain, e.g., the Ising model for N = 1 and the spherical model for N = {infinity}. A formula for the masses squared that break gauge symmetry for these O(N) classes is presented for d = 3. For the PSF on AdS space it is shown that it can be derived by lifting the PSF on flat space by a simple kernel which contains the sum over all spins. Finally we use an algorithm to derive all symmetric tensor higherspin fields. They arise from monomials of scalar fields by derivation and selection of conformal (quasiprimary) fields. Typically one monomial produces a multiplet of spin s conformal higherspin fields for all s {>=} 4, they are distinguished by their anomalous dimensions (in CFT{sub 3}) or by theirmass (in AdS{sub 4}). We sum over these multiplets and the spins to obtain 'string type fields', one for each such monomial.

Theoretical investigation of hyperfine field parameters through mossbauer gamma ray
SciTech Connect
Ali, Sikander; Hashim, Mohd
20120605
When a Mossbauer gammaray emitting or absorbing nucleus is placed in a crystalline environment, the quadrupole moment of the nucleus interacts with the electric field gradient set up by the ligands around it. In the transition 7/2>{yields}5/2> twelve lines are obtained. Applying the multipole radiation field theory and density matrix formalism, the determinant of coherency matrix, intensity and degree of polarization have been calculated for each line.

A microscopic field theoretical approach for active systems
NASA Astrophysics Data System (ADS)
Alaimo, F.; Praetorius, S.; Voigt, A.
20160801
We consider a microscopic modeling approach for active systems. The approach extends the phase field crystal (PFC) model and allows us to describe generic properties of active systems within a continuum model. The approach is validated by reproducing results obtained with corresponding agentbased and microscopic phase field models. We consider binary collisions, collective motion and vortex formation. For larger numbers of particles we analyze the coarsening process in active crystals and identify giant number fluctuation in a cluster formation process.

Nonlinear Riccati equations as a unifying link between linear quantum mechanics and other fields of physics
NASA Astrophysics Data System (ADS)
Schuch, Dieter
20140401
Theoretical physics seems to be in a kind of schizophrenic state. Many phenomena in the observable macroscopic world obey nonlinear evolution equations, whereas the microscopic world is governed by quantum mechanics, a fundamental theory that is supposedly linear. In order to combine these two worlds in a common formalism, at least one of them must sacrifice one of its dogmas. I claim that linearity in quantum mechanics is not as essential as it apparently seems since quantum mechanics can be reformulated in terms of nonlinear Riccati equations. In a first step, it will be shown where complex Riccati equations appear in timedependent quantum mechanics and how they can be treated and compared with similar spacedependent Riccati equations in supersymmetric quantum mechanics. Furthermore, the timeindependent Schrödinger equation can also be rewritten as a complex Riccati equation. Finally, it will be shown that (real and complex) Riccati equations also appear in many other fields of physics, like statistical thermodynamics and cosmology.

Towards experimental quantumfield tomography with ultracold atoms
PubMed Central
Steffens, A.; Friesdorf, M.; Langen, T.; Rauer, B.; Schweigler, T.; Hübener, R.; Schmiedmayer, J.; Riofrío, C.A.; Eisert, J.
20150101
The experimental realization of largescale manybody systems in atomicoptical architectures has seen immense progress in recent years, rendering full tomography tools for state identification inefficient, especially for continuous systems. To work with these emerging physical platforms, new technologies for state identification are required. Here we present first steps towards efficient experimental quantumfield tomography. Our procedure is based on the continuous analogues of matrixproduct states, ubiquitous in condensedmatter theory. These states naturally incorporate the locality present in realistic physical settings and are thus prime candidates for describing the physics of locally interacting quantum fields. To experimentally demonstrate the power of our procedure, we quench a onedimensional Bose gas by a transversal split and use our method for a partial quantumfield reconstruction of the farfromequilibrium states of this system. We expect our technique to play an important role in future studies of continuous quantum manybody systems. PMID:26138511

Quantum Humor: The Playful Side of Physics at Bohr's Institute for Theoretical Physics
NASA Astrophysics Data System (ADS)
Halpern, Paul
20120901
From the 1930s to the 1950s, a period of pivotal developments in quantum, nuclear, and particle physics, physicists at Niels Bohr's Institute for Theoretical Physics in Copenhagen took time off from their research to write humorous articles, letters, and other works. Best known is the Blegdamsvej Faust, performed in April 1932 at the close of one of the Institute's annual conferences. I also focus on the Journal of Jocular Physics, a humorous tribute to Bohr published on the occasions of his 50th, 60th, and 70th birthdays in 1935, 1945, and 1955. Contributors included Léon Rosenfeld, Victor Weisskopf, George Gamow, Oskar Klein, and Hendrik Casimir. I examine their contributions along with letters and other writings to show that they offer a window into some issues in physics at the time, such as the interpretation of complementarity and the nature of the neutrino, as well as the politics of the period.

Quantum mechanical force field for water with explicit electronic polarization
SciTech Connect
Han, Jaebeom; Mazack, Michael J. M.; Zhang, Peng; Truhlar, Donald G.; Gao, Jiali
20130807
A quantum mechanical force field (QMFF) for water is described. Unlike traditional approaches that use quantum mechanical results and experimental data to parameterize empirical potential energy functions, the present QMFF uses a quantum mechanical framework to represent intramolecular and intermolecular interactions in an entire condensedphase system. In particular, the internal energy terms used in molecular mechanics are replaced by a quantum mechanical formalism that naturally includes electronic polarization due to intermolecular interactions and its effects on the force constants of the intramolecular force field. As a quantum mechanical force field, both intermolecular interactions and the Hamiltonian describing the individual molecular fragments can be parameterized to strive for accuracy and computational efficiency. In this work, we introduce a polarizable molecular orbital model Hamiltonian for water and for oxygen and hydrogencontaining compounds, whereas the electrostatic potential responsible for intermolecular interactions in the liquid and in solution is modeled by a threepoint charge representation that realistically reproduces the total molecular dipole moment and the local hybridization contributions. The present QMFF for water, which is called the XP3P (explicit polarization with threepointcharge potential) model, is suitable for modeling both gasphase clusters and liquid water. The paper demonstrates the performance of the XP3P model for water and proton clusters and the properties of the pure liquid from about 900 × 10{sup 6} selfconsistentfield calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as

Quantum mechanical force field for water with explicit electronic polarization
PubMed Central
Han, Jaebeom; Mazack, Michael J. M.; Zhang, Peng; Truhlar, Donald G.; Gao, Jiali
20130101
A quantum mechanical force field (QMFF) for water is described. Unlike traditional approaches that use quantum mechanical results and experimental data to parameterize empirical potential energy functions, the present QMFF uses a quantum mechanical framework to represent intramolecular and intermolecular interactions in an entire condensedphase system. In particular, the internal energy terms used in molecular mechanics are replaced by a quantum mechanical formalism that naturally includes electronic polarization due to intermolecular interactions and its effects on the force constants of the intramolecular force field. As a quantum mechanical force field, both intermolecular interactions and the Hamiltonian describing the individual molecular fragments can be parameterized to strive for accuracy and computational efficiency. In this work, we introduce a polarizable molecular orbital model Hamiltonian for water and for oxygen and hydrogencontaining compounds, whereas the electrostatic potential responsible for intermolecular interactions in the liquid and in solution is modeled by a threepoint charge representation that realistically reproduces the total molecular dipole moment and the local hybridization contributions. The present QMFF for water, which is called the XP3P (explicit polarization with threepointcharge potential) model, is suitable for modeling both gasphase clusters and liquid water. The paper demonstrates the performance of the XP3P model for water and proton clusters and the properties of the pure liquid from about 900 × 106 selfconsistentfield calculations on a periodic system consisting of 267 water molecules. The unusual dipole derivative behavior of water, which is incorrectly modeled in molecular mechanics, is naturally reproduced as a result of an electronic structural treatment of chemical bonding by XP3P. We anticipate that the XP3P model will be useful for studying proton transport in solution and solid phases as well as across

Quantum field theory for condensation of bosons and fermions
SciTech Connect
De Souza, Adriano N.; Filho, Victo S.
20130325
In this brief review, we describe the formalism of the quantum field theory for the analysis of the condensation phenomenon in bosonic systems, by considering the cases widely verified in laboratory of trapped gases as condensate states, either with attractive or with repulsive twobody interactions. We review the mathematical formulation of the quantum field theory for many particles in the meanfield approximation, by adopting contact interaction potential. We also describe the phenomenon of condensation in the case of fermions or the degenerate Fermi gas, also verified in laboratory in the crossover BECBCS limit. We explain that such a phenomenon, equivalent to the bosonic condensation, can only occur if we consider the coupling of particles in pairs behaving like bosons, as occurs in the case of Cooper's pairs in superconductivity.

Lorentz symmetric quantum field theory for symplectic fermions
SciTech Connect
Robinson, Dean J.; Kapit, Eliot; LeClair, Andre
20091115
A free quantum field theory with Lorentz symmetry is derived for spinhalf symplectic fermions in 2+1 dimensions. In particular, we show that fermionic spinhalf fields may be canonically quantized in a free theory with a KleinGordon Lagrangian. This theory is shown to have all the required properties of a consistent free quantum field theory, namely, causality, unitarity, adherence to the spinstatistics theorem, CPT symmetry, and the Hermiticity and positive definiteness of the Hamiltonian. The global symmetry of the free theory is Sp(4){approx_equal}SO(5). Possible interacting theories of both the pseudoHermitian and Hermitian variety are then examined briefly.

Quantum entanglement of local operators in conformal field theories.
PubMed
Nozaki, Masahiro; Numasawa, Tokiro; Takayanagi, Tadashi
20140321
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 EinsteinPodolskyRosen states. They agree with a heuristic picture of propagations of entangled particles. PMID:24702348

Reconstruction in quantum field theory with a fundamental length
SciTech Connect
Soloviev, M. A.
20100915
In this paper, we establish an analog of Wightman's reconstruction theorem for nonlocal quantum field theory with a fundamental length. In our setting, the Wightman generalized functions are defined on test functions analytic in a complex lneighborhood of the real space and are localizable at scales large compared to l. The causality condition is formulated as continuity of the field commutator in an appropriate topology associated with the light cone. We prove that the relevant function spaces are nuclear and derive the kernel theorems for the corresponding classes of multilinear functionals, which provides the basis for the reconstruction procedure. Special attention is given to the accurate determination of the domain of the reconstructed quantum fields in the Hilbert space of states. We show that the primitive common invariant domain must be suitably extended to implement the (quasi)localizability and causality conditions.

Democracy of internal symmetries in supersymmetrical quantum field theory
SciTech Connect
Lopuszanski, J.T.
19811201
The freedom of choice of some discrete and internal symmetries in the supersymmetric, massive, interacting quantum field theory is discussed. It is shown that the discrete symmetry consisting of changing the sign of some (not all) scalar fields is incompatible with the supersymmetric structure of the theory. It is further demonstrated that an internal symmetry which transforms only some of the fields of fixed spin leaving the other fields invariant and which acts nontrivially on the supercharges can not be admitted as a symmetry; although it can be a good internal symmetry in absence of supersymmetric covariance. Moreover, in case of a model consisting of scalar, spinor and vector fields even a symmetry which transforms all of the scalar (vector) fields leaving spinor and vector (scalar) fields unaffected is ruled out provided it acts nontrivially on some of the supercharges.

Theory of a quantum noncanonical field in curved spacetimes
SciTech Connect
Indurain, Javier; Liberati, Stefano
20090815
Much attention has been recently devoted to the possibility that quantum gravity effects could lead to departures from special relativity in the form of a deformed Poincare algebra. These proposals go generically under the name of doubly or deformed special relativity (DSR). In this article we further explore a recently proposed class of quantum field theories, involving noncanonically commuting complex scalar fields, which have been shown to entail a DSRlike symmetry. An open issue for such theories is whether the DSRlike symmetry has to be taken as a physically relevant symmetry, or if in fact the 'true' symmetries of the theory are just rotations and translations while boost invariance has to be considered broken. Here we analyze this issue by extending the known results to curved spacetime under both of the previous assumptions. We show that if the symmetry of the free theory is taken to be a DSRlike realization of the Poincare symmetry, then it is not possible to render such a symmetry a gauge symmetry of the curved physical spacetime. However, it is possible to introduce an auxiliary spacetime which allows one to describe the theory as a standard quantum field theory in curved spacetime. Alternatively, taking the point of view that the noncanonical commutation of the fields actually implies a breakdown of boost invariance, the physical spacetime manifold has to be foliated in surfaces of simultaneity, and the field theory can be coupled to gravity by making use of the ArnowittDeserMisner prescription.

Theoretical simulation of carrier capture and relaxation rates in quantumdot semiconductor optical amplifiers
SciTech Connect
Wu, Yunhu; Zhang, Guoping; Guo, Ling; Qi, Guoqun; Li, Xiaoming
20140614
Based on Auger scattering mechanism, carriercarrier scattering dynamics between the twodimensional carrier reservoir (also called wetting layer, i.e., WL) and the confined quantum dot ground and first excited state in quantumdot semiconductor optical amplifiers (QDSOAs) are investigated theoretically in this paper. The scattering rates for independent electron and hole densities are calculated. The results show an ultrafast carrier capture (relaxation) rate up to 1 ps{sup −1}, and there is a complex dependence of the Coulomb scattering rates on the WL electron and hole densities. In addition, due to the different effective mass and the level distribution, the scattering rates for electron and hole are very different. Finally, in order to provide a direction to control (increase or decrease) the input current in realistic QDSOA systems, a simple method is proposed to determine the trends of the carrier recovery rates with the WL carrier densities in the vicinity of the steadystate.

A theoretical and experimental study of λ>2 μm luminescence of quantum dots on InP substrate
NASA Astrophysics Data System (ADS)
Doré, F.; Even, J.; Cornet, C.; Schliwa, A.; Bertru, N.; Dehaese, O.; Alghoraibi, I.; Folliot, H.; Piron, R.; Le Corre, A.; Loualiche, S.
20070401
Theoretical and experimental studies of the electronic properties of InAs(Sb) quantum dots (QDs) grown by molecular beam epitaxy (MBE) on InP(100) substrate are presented. Eightband kṡp calculations including strain and piezoelectric effects are performed on InAs/InP(100) quantum dot (QD) structure to study the influence of the quantum dot height. Photoluminescence (PL) spectroscopy experiments show promising results. High arsine flow rate during the growth of InAs QDs makes possible long emission wavelength beyond 2 μm. Emission wavelength as long as 2.35 μm is observed with InAsSb QDs.

Electric field geometries dominate quantum transport coupling in silicon nanoring
SciTech Connect
Lee, TsungHan Email: sfhu.hu@gmail.com; Hu, ShuFen Email: sfhu.hu@gmail.com
20140328
Investigations on the relation between the geometries of silicon nanodevices and the quantum phenomenon they exhibit, such as the Aharonov–Bohm (AB) effect and the Coulomb blockade, were conducted. An arsenic doped silicon nanoring coupled with a nanowire by electron beam lithography was fabricated. At 1.47 K, Coulomb blockade oscillations were observed under modulation from the top gate voltage, and a periodic AB oscillation of ΔB = 0.178 T was estimated for a ring radius of 86 nm under a high sweeping magnetic field. Modulating the flat top gate and the pointed side gate was performed to cluster and separate the many electron quantum dots, which demonstrated that quantum confinement and interference effects coexisted in the doped silicon nanoring.

Faraday effect: A field theoretical point of view
NASA Astrophysics Data System (ADS)
Ganguly, Avijit K.; Konar, Sushan; Pal, Palash B.
19991101
We analyze the structure of the vacuum polarization tensor in the presence of a background electromagnetic field in a medium. We use various discrete symmetries and crossing symmetry to constrain the form factors obtained for the most general case. From these symmetry arguments, we show why the vacuum polarization tensor has to be even in the background field when there is no background medium. Taking then the background field to be purely magnetic, we evaluate the vacuum polarization to linear order in it. The result shows the phenomenon of Faraday rotation, i.e., the rotation of the plane of polarization of a plane polarized light passing through this background. We find that the usual expression for Faraday rotation, which is derived for a nondegenerate plasma in the nonrelativistic approximation, undergoes substantial modification if the background is degenerate and/or relativistic. We give explicit expressions for Faraday rotation in completely degenerate and ultrarelativistic media.

DC response of hot carriers under circularly polarized intense microwave fields and intense magnetic fields in quantum wells
SciTech Connect
Ishida, Norihisa
20131204
Hot carrier dynamics under intense microwave and crossed magnetic fields are investigated theoretically for the case that the dominant scattering process is inelastic collision, especially intersubband and intrasubband transition in Quantum wells. If the applied electric fields are circularly polarized, the equation of motion forms symmetric on the xy plane. But the carrier motions are complicated to accumulate because of acceleration and emission process. This situation makes possible to create a variation of the carrier motion, typically the carrier bunching is occurred. This state is a sort of population inversion. The DC response of this system attains strongly negative at appropriate field conditions. Through the simulation for the real case described below, it may include a type of induced emission.

Can fluctuations of classical random field produce quantum averages?
NASA Astrophysics Data System (ADS)
Khrennikov, Andrei
20090801
Albert Einstein did not believe in completeness of QM. He dreamed of creation of prequantum classical statistical mechanics such that QM will be reproduced as its approximation. He also dreamed of total exclusion of corpuscules from the future model. Reality of Einstein's dream was pure fields' reality. Recently I made his dream come true in the form of so called prequantum classical statistical field theory (PCSFT). In this approach quantum systems are described by classical random fields, e.g., electromagnetic field (instead of photon), electron field or neutron field. In this paper we generalize PCSFT to composite quantum system. It is well known that in QM, unlike classical mechanics, the state of a composite system is described by the tensor product of state spaces for its subsystems. In PCSFT one can still use Cartesian product, but state spaces are spaces of classical fields (not particles). In particular, entanglement is nothing else than correlation of classical random fields, cf. again Einstein. Thus entanglement was finally demystified.

Keldysh field theory for driven open quantum systems.
PubMed
Sieberer, L M; Buchhold, M; Diehl, S
20160901
Recent experimental developments in diverse areasranging from cold atomic gases to lightdriven semiconductors to microcavity arraysmove systems into the focus which are located on the interface of quantum optics, manybody physics and statistical mechanics. They share in common that coherent and drivendissipative quantum dynamics occur on an equal footing, creating genuine nonequilibrium scenarios without immediate counterpart in equilibrium condensed matter physics. This concerns both their nonthermal stationary states and their manybody time evolution. It is a challenge to theory to identify novel instances of universal emergent macroscopic phenomena, which are tied unambiguously and in an observable way to the microscopic drive conditions. In this review, we discuss some recent results in this direction. Moreover, we provide a systematic introduction to the open system Keldysh functional integral approach, which is the proper technical tool to accomplish a merger of quantum optics and manybody physics, and leverages the power of modern quantum field theory to driven open quantum systems. PMID:27482736

Keldysh field theory for driven open quantum systems
NASA Astrophysics Data System (ADS)
Sieberer, L. M.; Buchhold, M.; Diehl, S.
20160901
Recent experimental developments in diverse areas—ranging from cold atomic gases to lightdriven semiconductors to microcavity arrays—move systems into the focus which are located on the interface of quantum optics, manybody physics and statistical mechanics. They share in common that coherent and driven–dissipative quantum dynamics occur on an equal footing, creating genuine nonequilibrium scenarios without immediate counterpart in equilibrium condensed matter physics. This concerns both their nonthermal stationary states and their manybody time evolution. It is a challenge to theory to identify novel instances of universal emergent macroscopic phenomena, which are tied unambiguously and in an observable way to the microscopic drive conditions. In this review, we discuss some recent results in this direction. Moreover, we provide a systematic introduction to the open system Keldysh functional integral approach, which is the proper technical tool to accomplish a merger of quantum optics and manybody physics, and leverages the power of modern quantum field theory to driven open quantum systems.

On some theoretical problems of laser wakefield accelerators
NASA Astrophysics Data System (ADS)
Bulanov, S. V.; Esirkepov, T. Zh.; Hayashi, Y.; Kiriyama, H.; Koga, J. K.; Kotaki, H.; Mori, M.; Kando, M.
20160601
Enhancement of the quality of laser wakefield accelerated (LWFA) electron beams implies the improvement and controllability of the properties of the wake waves generated by ultrashort pulse lasers in underdense plasmas. In this work we present a compendium of useful formulas giving relations between the laser and plasma target parameters allowing one to obtain basic dependences, e.g. the energy scaling of the electrons accelerated by the wake field excited in inhomogeneous media including multistage LWFA accelerators. Consideration of the effects of using the chirped laser pulse driver allows us to find the regimes where the chirp enhances the wake field amplitude. We present an analysis of the threedimensional effects on the electron beam loading and on the unlimited LWFA acceleration in inhomogeneous plasmas. Using the conditions of electron trapping to the wakefield acceleration phase we analyse the multiequal stage and multiuneven stage LWFA configurations. In the first configuration the energy of fast electrons is a linear function of the number of stages, and in the second case, the accelerated electron energy grows exponentially with the number of stages. The results of the twodimensional particleincell simulations presented here show the high quality electron acceleration in the triple stage injectionacceleration configuration.

On some theoretical problems of laser wakefield accelerators
NASA Astrophysics Data System (ADS)
Bulanov, S. V.; Esirkepov, T. Zh.; Hayashi, Y.; Kiriyama, H.; Koga, J. K.; Kotaki, H.; Mori, M.; Kando, M.
20160601
> Enhancement of the quality of laser wakefield accelerated (LWFA) electron beams implies the improvement and controllability of the properties of the wake waves generated by ultrashort pulse lasers in underdense plasmas. In this work we present a compendium of useful formulas giving relations between the laser and plasma target parameters allowing one to obtain basic dependences, e.g. the energy scaling of the electrons accelerated by the wake field excited in inhomogeneous media including multistage LWFA accelerators. Consideration of the effects of using the chirped laser pulse driver allows us to find the regimes where the chirp enhances the wake field amplitude. We present an analysis of the threedimensional effects on the electron beam loading and on the unlimited LWFA acceleration in inhomogeneous plasmas. Using the conditions of electron trapping to the wakefield acceleration phase we analyse the multiequal stage and multiuneven stage LWFA configurations. In the first configuration the energy of fast electrons is a linear function of the number of stages, and in the second case, the accelerated electron energy grows exponentially with the number of stages. The results of the twodimensional particleincell simulations presented here show the high quality electron acceleration in the triple stage injectionacceleration configuration.

Cold atom simulation of interacting relativistic quantum field theories.
PubMed
Cirac, J Ignacio; Maraner, Paolo; Pachos, Jiannis K
20101101
We demonstrate that Dirac fermions selfinteracting or coupled to dynamic scalar fields can emerge in the low energy sector of designed bosonic and fermionic cold atom systems. We illustrate this with two examples defined in two spacetime dimensions. The first one is the selfinteracting Thirring model. The second one is a model of Dirac fermions coupled to a dynamic scalar field that gives rise to the GrossNeveu model. The proposed cold atom experiments can be used to probe spectral or correlation properties of interacting quantum field theories thereby presenting an alternative to lattice gauge theory simulations. PMID:21231152

Electric Fields in the 5/2 fractional quantum Hall effect
NASA Astrophysics Data System (ADS)
TylanTyler, Anthony; LyandaGeller, Yuli
The potential for nonAbelian quasiholes in the 5/2 fractional quantum Hall effect makes the state of interest theoretically and experimentally. The presence of such features in the ground state of the system would allow for the implementation of a topological quantum computation scheme. In order to probe the system for these features, a small measuring voltage, i.e. an electric field, is applied. In Corbino geometries, these electric fields are applied radially. This breaks the Galilean invariance, which in an infinite planar geometry allows us to transform to a moving frame of reference, eliminating the electric field. To study the effects of these fields, we carry out exact diagonalization calculations in a disk geometry. We find that application of small fields can lead to an improvement in the overlap with the MooreRead Pfaffian long before the state is destroyed by the field. Additionally, we find that the coherence length of quasiholes travelling along the edge of the sample increases significantly when compared to the case with no applied field. This research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award DESC0010544.

Spontaneous emission control of quantum dots embedded in photonic crystals: Effects of external fields and dimension
NASA Astrophysics Data System (ADS)
Vaseghi, B.; Hashemi, H.
20160601
In this paper simultaneous effects of external electric and magnetic fields and quantum confinement on the radiation properties of spherical quantum dot embedded in a photonic crystal are investigated. Under the influence of photonic bandgap, effects of external static fields and dot dimension on the amplitude and spectrum of different radiation fields emitted by the quantum dot are studied. Our results show the considerable effects of external fields and quantum confinement on the spontaneous emission of the system.

Multitime wave functions for quantum field theory
SciTech Connect
Petrat, Sören; Tumulka, Roderich
20140615
Multitime wave functions such as ϕ(t{sub 1},x{sub 1},…,t{sub N},x{sub N}) have one time variable t{sub j} for each particle. This type of wave function arises as a relativistic generalization of the wave function ψ(t,x{sub 1},…,x{sub N}) of nonrelativistic quantum mechanics. We show here how a quantum field theory can be formulated in terms of multitime wave functions. We mainly consider a particular quantum field theory that features particle creation and annihilation. Starting from the particle–position representation of state vectors in Fock space, we introduce multitime wave functions with a variable number of time variables, set up multitime evolution equations, and show that they are consistent. Moreover, we discuss the relation of the multitime wave function to two other representations, the Tomonaga–Schwinger representation and the Heisenberg picture in terms of operatorvalued fields on space–time. In a certain sense and under natural assumptions, we find that all three representations are equivalent; yet, we point out that the multitime formulation has several technical and conceptual advantages.  Highlights: •Multitime wave functions are manifestly Lorentzcovariant objects. •We develop consistent multitime equations with interaction for quantum field theory. •We discuss in detail a particular model with particle creation and annihilation. •We show how multitime wave functions are related to the Tomonaga–Schwinger approach. •We show that they have a simple representation in terms of operator valued fields.

Some theoretical and numerical results for delayed neural field equations
NASA Astrophysics Data System (ADS)
Faye, Grégory; Faugeras, Olivier
20100501
In this paper we study neural field models with delays which define a useful framework for modeling macroscopic parts of the cortex involving several populations of neurons. Nonlinear delayed integrodifferential equations describe the spatiotemporal behavior of these fields. Using methods from the theory of delay differential equations, we show the existence and uniqueness of a solution of these equations. A Lyapunov analysis gives us sufficient conditions for the solutions to be asymptotically stable. We also present a fairly detailed study of the numerical computation of these solutions. This is, to our knowledge, the first time that a serious analysis of the problem of the existence and uniqueness of a solution of these equations has been performed. Another original contribution of ours is the definition of a Lyapunov functional and the result of stability it implies. We illustrate our numerical schemes on a variety of examples that are relevant to modeling in neuroscience.

Perturbative quantum field theory in the framework of the fermionic projector
SciTech Connect
Finster, Felix
20140415
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.

Theoretical Aspects of Magnetic Fields for Gamma Ray Bursts
NASA Astrophysics Data System (ADS)
Hanami, Hitoshi
We propose magnetic cannon ball mechanism in which the collapse of a magnetosphere onto a black hole can generate strong outward Poynting flux which drives a baryonfree fireball called the magnetic cannon ball. In the early stage, the magnetic fields in the cannon ball can prepare the explanation for the cycrotoron absorptions observed by GINGA. The magnetic cannon ball can drive, in general, a relativistic outflow which interacts with the interstellar matter and forms a shock. The magnetic field in the shock approximately equal to 104 G can induce the synchrotron radiations with peaks at approximately equal to 10^2 keV observed. This magnetic field in the cannon ball can also confine the high energy protons (gamma_p > 30) which are required for delayed photons (>25 GeV) following a burst on 1994 February 17. Accretion induced collapse of a white dwarf of > 109 G, merger of a close binary and failed type Ib supernovae are possible scenarios even without the rotation of the central object. This mechanism works at the final phase of gravitational collapse even after a neutrino driven fireball proposed in most scenarios for gamma ray bursts. Twice bursts, which consist of primary neutrino driven fireball and secondary magnetic cannon ball can be induced sometime, can be explained in this model. It suggests that the magnetic cannon ball works some parts in multiple populations and delayed or multiple burst events. The final remnant in the model should be a black hole. It implies that any gamma ray bursts can have no optical counter part if they do not have a companion in a binary.

Clusterlike coordinates in supersymmetric quantum field theory
PubMed Central
Neitzke, Andrew
20140101
Recently it has become apparent that N=2 supersymmetric quantum field theory has something to do with cluster algebras. I review one aspect of the connection: supersymmetric quantum field theories have associated hyperkähler moduli spaces, and these moduli spaces carry a structure that looks like an extension of the notion of cluster variety. In particular, one encounters the usual variables and mutations of the cluster story, along with more exotic extra variables and generalized mutations. I focus on a class of examples where the underlying cluster varieties are moduli spaces of flat connections on surfaces, as considered by Fock and Goncharov [Fock V, Goncharov A (2006) Publ Math Inst Hautes Études Sci 103:1–211]. The work reviewed here is largely joint with Davide Gaiotto and Greg Moore. PMID:24982190

Geometric and Topological Methods for Quantum Field Theory
NASA Astrophysics Data System (ADS)
Cardona, Alexander; Contreras, Iván.; ReyesLega, Andrés. F.
20130501
Introduction; 1. A brief introduction to Dirac manifolds Henrique Bursztyn; 2. Differential geometry of holomorphic vector bundles on a curve Florent Schaffhauser; 3. Paths towards an extension of ChernWeil calculus to a class of infinite dimensional vector bundles Sylvie Paycha; 4. Introduction to Feynman integrals Stefan Weinzierl; 5. Iterated integrals in quantum field theory Francis Brown; 6. Geometric issues in quantum field theory and string theory Luis J. Boya; 7. Geometric aspects of the standard model and the mysteries of matter Florian Scheck; 8. Absence of singular continuous spectrum for some geometric Laplacians Leonardo A. Cano García; 9. Models for formal groupoids Iván Contreras; 10. Elliptic PDEs and smoothness of weakly Einstein metrics of Hölder regularity Andrés Vargas; 11. Regularized traces and the index formula for manifolds with boundary Alexander Cardona and César Del Corral; Index.

Quantum field theories on algebraic curves. I. Additive bosons
NASA Astrophysics Data System (ADS)
Takhtajan, Leon A.
20130401
Using Serre's adelic interpretation of cohomology, we develop a `differential and integral calculus' on an algebraic curve X over an algebraically closed field k of constants of characteristic zero, define algebraic analogues of additive multivalued functions on X and prove the corresponding generalized residue theorem. Using the representation theory of the global Heisenberg algebra and lattice Lie algebra, we formulate quantum field theories of additive and charged bosons on an algebraic curve X. These theories are naturally connected with the algebraic de Rham theorem. We prove that an extension of global symmetries (Witten's additive Ward identities) from the kvector space of rational functions on X to the vector space of additive multivalued functions uniquely determines these quantum theories of additive and charged bosons.

Enhanced current injection from a quantum well to a quantum dash in magnetic field
NASA Astrophysics Data System (ADS)
ParaviciniBagliani, Gian L.; Liverini, Valeria; Valmorra, Federico; Scalari, Giacomo; Gramm, Fabian; Faist, Jérôme
20140801
Resonant tunneling injection is a key ingredient in achieving population inversion in a putative quantum dot cascade laser. In a quantum dot based structure, such resonant current requires a matching of the wavefunction shape in kspace between the injector and the quantum dot. We show experimentally that the injection into an excited state of a dash structure can be enhanced tenfold by an inplane magnetic field that shifts the injector distribution in kspace. These experiments, performed on resonant tunneling diode structures, show unambiguously resonant tunneling into an ensemble of InAs dashes grown between two AlInAs barrier layers. They also show that interface roughness scattering can enhance the tunneling current.

Theoretical analysis of a cell's oscillations in an acoustic field
NASA Astrophysics Data System (ADS)
Allen, John S.; Zinin, Pavel
20050901
The analysis and deformation of an individual cell in a highfrequency acoustic field is of fundamental interest for a variety of applications such as ultrasound cell separation and drug delivery. The oscillations of biological cells in a sound field are investigated using a shell model for the cell following an approach developed previously [Zinin, Ultrasonics, 30, 2634 (1992)]. The model accounts for the three components which comprise the cell's motion: the internal fluid (cytoplasma), the cell membrane, and the surrounding fluid. The cell membrane whose thickness is small compared to the cell radius can be approximated as a thin elastic shell. The elastic properties of this shell together with the viscosities of the internal and external fluids determine the oscillations of the cell. The dipole oscillations of the cell depend on the surface area modulus and the maximum frequency for the relative change in cell area can be determined. Moreover, the higher order oscillations starting with the quadrupole oscillations are governed by the shell's shear modulus. Induced stresses in bacteria cell membranes in the vicinity of an oscillating bubble are investigated and cell rupture with respect to these stresses is analyzed.

BL Herculis stars  Theoretical models for field variables
NASA Technical Reports Server (NTRS)
Carson, R.; Stothers, R.
19820101
Type II Cepheids with periods between 1 and 3 days, commonly designated as Bl Herculis stars, have been modeled here with the aim of interpreting the wide variety of light curves observed among the field variables. Previously modeled globular cluster members are used as standard calibration objects. The major finding is that only a small range of luminosities is capable of generating a large variety of light curve types at a given period. For a mass of approximately 0.60 solar mass, the models are able to reproduce the observed mean luminosities, dispersion of mean luminosities, periods, light amplitudes, light asymmetries, and phases of secondary features in the light curves of known BL Her stars. It is possible that the metalrich variables (which are found only in the field) have luminosities lower than those of most metalpoor variables. The present revised mass for BL Her, a metalrich object, is not significantly different from the mean mass of the metalpoor variables.

A Theoretical Mechanism of Szilard Engine Function in Nucleic Acids and the Implications for Quantum Coherence in Biological Systems
SciTech Connect
Matthew Mihelic, F.
20101222
Nucleic acids theoretically possess a Szilard engine function that can convert the energy associated with the Shannon entropy of molecules for which they have coded recognition, into the useful work of geometric reconfiguration of the nucleic acid molecule. This function is logically reversible because its mechanism is literally and physically constructed out of the information necessary to reduce the Shannon entropy of such molecules, which means that this information exists on both sides of the theoretical engine, and because information is retained in the geometric degrees of freedom of the nucleic acid molecule, a quantum gate is formed through which multistate nucleic acid qubits can interact. Entangled biophotons emitted as a consequence of symmetry breaking nucleic acid Szilard engine (NASE) function can be used to coordinate relative positioning of different nucleic acid locations, both within and between cells, thus providing the potential for quantum coherence of an entire biological system. Theoretical implications of understanding biological systems as such 'quantum adaptive systems' include the potential for multiagent based quantum computing, and a better understanding of systemic pathologies such as cancer, as being related to a loss of systemic quantum coherence.

Magnetocaloric effect and magnetic cooling near a fieldinduced quantumcritical point
PubMed Central
Wolf, Bernd; Tsui, Yeekin; JaiswalNagar, Deepshikha; Tutsch, Ulrich; Honecker, Andreas; RemovićLanger, Katarina; Hofmann, Georg; Prokofiev, Andrey; Assmus, Wolf; Donath, Guido; Lang, Michael
20110101
The presence of a quantumcritical point (QCP) can significantly affect the thermodynamic properties of a material at finite temperatures T. This is reflected, e.g., in the entropy landscape S(T,r) in the vicinity of a QCP, yielding particularly strong variations for varying the tuning parameter r such as pressure or magnetic field B. Here we report on the determination of the critical enhancement of ∂S/∂B near a Binduced QCP via absolute measurements of the magnetocaloric effect (MCE), (∂T/∂B)S and demonstrate that the accumulation of entropy around the QCP can be used for efficient lowtemperature magnetic cooling. Our proof of principle is based on measurements and theoretical calculations of the MCE and the cooling performance for a Cu2+containing coordination polymer, which is a very good realization of a spin½ antiferromagnetic Heisenberg chain—one of the simplest quantumcritical systems.

Initial states in integrable quantum field theory quenches from an integral equation hierarchy
NASA Astrophysics Data System (ADS)
Horváth, D. X.; Sotiriadis, S.; Takács, G.
20160101
We consider the problem of determining the initial state of integrable quantum field theory quenches in terms of the postquench eigenstates. The corresponding overlaps are a fundamental input to most exact methods to treat integrable quantum quenches. We construct and examine an infinite integral equation hierarchy based on the form factor bootstrap, proposed earlier as a set of conditions determining the overlaps. Using quenches of the mass and interaction in SinhGordon theory as a concrete example, we present theoretical arguments that the state has the squeezed coherent form expected for integrable quenches, and supporting an Ansatz for the solution of the hierarchy. Moreover we also develop an iterative method to solve numerically the lowest equation of the hierarchy. The iterative solution along with extensive numerical checks performed using the next equation of the hierarchy provides a strong numerical evidence that the proposed Ansatz gives a very good approximation for the solution.

Horava—Lifshitz Type Quantum Field Theory and Hierarchy Problem
NASA Astrophysics Data System (ADS)
Wei, Chao
20160601
We study the Lifshitz type extension of the standard model (SM) at the UV, with dynamical critical exponent z = 3. One loop radiative corrections to the Higgs mass in such a model are calculated. Our result shows that, the Hierarchy problem, which has initiated many excellent extension of the minimal SM, may be weakened in the z = 3 Lifshitz type quantum field theory. Supported by the National Natural Science Foundation of China

Quantum field as a quantum cellular automaton: The Dirac free evolution in one dimension
SciTech Connect
Bisio, Alessandro; D’Ariano, Giacomo Mauro; Tosini, Alessandro
20150315
We present a quantum cellular automaton model in one spacedimension which has the Dirac equation as emergent. This model, a discretetime and causal unitary evolution of a lattice of quantum systems, is derived from the assumptions of homogeneity, parity and timereversal invariance. The comparison between the automaton and the Dirac evolutions is rigorously set as a discrimination problem between unitary channels. We derive an exact lower bound for the probability of error in the discrimination as an explicit function of the mass, the number and the momentum of the particles, and the duration of the evolution. Computing this bound with experimentally achievable values, we see that in that regime the QCA model cannot be discriminated from the usual Dirac evolution. Finally, we show that the evolution of oneparticle states with narrowband in momentum can be efficiently simulated by a dispersive differential equation for any regime. This analysis allows for a comparison with the dynamics of wavepackets as it is described by the usual Dirac equation. This paper is a first step in exploring the idea that quantum field theory could be grounded on a more fundamental quantum cellular automaton model and that physical dynamics could emerge from quantum information processing. In this framework, the discretization is a central ingredient and not only a tool for performing nonperturbative calculation as in lattice gauge theory. The automaton model, endowed with a precise notion of local observables and a full probabilistic interpretation, could lead to a coherent unification of a hypothetical discrete Planck scale with the usual Fermi scale of highenergy physics.  Highlights: • The free Dirac field in one space dimension as a quantum cellular automaton. • Large scale limit of the automaton and the emergence of the Dirac equation. • Dispersive differential equation for the evolution of smooth states on the automaton. • Optimal discrimination between the

The effect of gravitational tidal forces on renormalized quantum fields
NASA Astrophysics Data System (ADS)
Hollowood, Timothy J.; Shore, Graham M.
20120201
The effect of gravitational tidal forces on renormalized quantum fields propagating in curved spacetime is investigated and a generalisation of the optical theorem to curved spacetime is proved. In the case of QED, the interaction of tidal forces with the vacuum polarization cloud of virtual e + e  pairs dressing the renormalized photon has been shown to produce several novel phenomena. In particular, the photon field amplitude can locally increase as well as decrease, corresponding to a negative imaginary part of the refractive index, in apparent violation of unitarity and the optical theorem. Below threshold decays into e + e  pairs may also occur. In this paper, these issues are studied from the point of view of a nonequilibrium initialvalue problem, with the field evolution from an initial null surface being calculated for physically distinct initial conditions and for both scalar field theories and QED. It is shown how a generalised version of the optical theorem, valid in curved spacetime, allows a local increase in amplitude while maintaining consistency with unitarity. The picture emerges of the field being dressed and undressed as it propagates through curved spacetime, with the local gravitational tidal forces determining the degree of dressing and hence the amplitude of the renormalized quantum field. These effects are illustrated with many examples, including a description of the undressing of a photon in the vicinity of a black hole singularity.

Theoretical studies for experimental implementation of quantum computing with trapped ions
NASA Astrophysics Data System (ADS)
Yoshimura, Bryce T.
Certain quantum manybody physics problems, such as the transverse field Ising model are intractable on a classical computer, meaning that as the number of particles grows, or spins, the amount of memory and computational time required to solve the problem exactly increases faster than a polynomial behavior. However, quantum simulators are being developed to efficiently solve quantum problems that are intractable via conventional computing. Some of the most successful quantum simulators are based on ion traps. Their success depends on the ability to achieve long coherence time, precise spin control, and high fidelity in state preparation. In this work, I present calculations that characterizes the oblate Paul trap that creates twodimensional Coulomb crystals in a triangular lattice and phonon modes. We also calculate the spinspin Isinglike interaction that can be generated in the oblate Paul trap using the same techinques as the linear radiofrequency Paul trap. In addition, I discuss two possible challenges that arise in the Penning trap: the effects of defects ( namely when Be+ → BeH+) and the creation of a more uniform spinspin Isinglike interaction. We show that most properties are not significantly influenced by the appearance of defects, and that by adding two potentials to the Penning trap a more uniform spinspin Isinglike interaction can be achieved. Next, I discuss techniques tfor preparing the ground state of the Isinglike Hamiltonian. In particular, we explore the use of the bangbang protocol to prepare the ground state and compare optimized results to conventional adiabatic ramps ( the exponential and locally adiabatic ramp ). The bangbang optimization in general outperforms the exponential; however the locally adiabatic ramp consistently is somewhat better. However, compared to the locally adiabatic ramp, the bangbang optimization is simpler to implement, and it has the advantage of providingrovide a simple procedure for estimating the

Introduction to Nonequilibrium Statistical Mechanics with Quantum Field Theory
NASA Astrophysics Data System (ADS)
Kita, T.
20100401
In this article, we present a concise and selfcontained introduction to nonequilibrium statistical mechanics with quantum field theory by considering an ensemble of interacting identical bosons or fermions as an example. Readers are assumed to be familiar with the Matsubara formalism of equilibrium statistical mechanics such as Feynman diagrams, the proper selfenergy, and Dyson's equation. The aims are threefold: (i) to explain the fundamentals of nonequilibrium quantum field theory as simple as possible on the basis of the knowledge of the equilibrium counterpart; (ii) to elucidate the hierarchy in describing nonequilibrium systems from Dyson's equation on the Keldysh contour to the NavierStokes equation in fluid mechanics via quantum transport equations and the Boltzmann equation; (iii) to derive an expression of nonequilibrium entropy that evolves with time. In stage (i), we introduce nonequilibrium Green's function and the selfenergy uniquely on the roundtrip Keld ysh contour, thereby avoiding possible confusions that may arise from defining multiple Green's functions at the very beginning. We try to present the Feynman rules for the perturbation expansion as simple as possible. In particular, we focus on the selfconsistent perturbation expansion with the LuttingerWard thermodynamic functional, i.e., Baym's Phiderivable approximation, which has a crucial property for nonequilibrium systems of obeying various conservation laws automatically. We also show how the twoparticle correlations can be calculated within the Phiderivable approximation, i.e., an issue of how to handle the ``BogoliubovBornGreenKirkwoodYvons (BBGKY) hierarchy''. Aim (ii) is performed through successive reductions of relevant variables with the Wigner transformation, the gradient expansion based on the GroenewoldMoyal product, and Enskog's expansion from local equilibrium. This part may be helpful for convincing readers that nonequilibrium systems ca n be handled

Axiomatics of Galileoinvariant quantum field theory
SciTech Connect
Dadashev, L.A.
19860301
The aim of this paper is to construct the axiomatics of Galileoinvariant quantum field theory. The importance of this problem is demonstrated from various points of view: general properties that the fields and observables must satisfy are considered; Smatrix nontriviality of one such model is proved; and the differences from the relativistic case are discussed. The proposed system of axioms is in many respects analogous to Wightman axiomatics, but is less general. The main result is contained in theorems which describe the admissible set of initial fields and total Hamiltonians, i.e., precisely the two entities that completely determine interacting fields. The author considers fields that prove the independence of some axioms.

Theoretical Investigation of FieldLine Quality in a Driven Spheromak
SciTech Connect
Cohen, R H; Berj, H; Cohen, B I; Fowler, T K; Glasser, A H; Hooper, E B; Lo Destro, L L; Morse, E C; Pearlstein; Rognlien, T D; Ryutov, D D; Sovince, C R; Woodruff, S
20021007
Theoretical studies aimed at predicting and diagnosing fieldline quality in a spheromak are described. These include nonlinear 3D MHD simulations, stability studies, analyses of confinement in spheromaks dominated by either open (stochastic) field lines or approximate flux surfaces, and a theory of fast electrons as a probe of fieldline length.

Analysis of the influence of external magnetic field on transition matrix elements in quantum well and quantum cascade laser structures
NASA Astrophysics Data System (ADS)
Demić, Aleksandar; Radovanović, Jelena; Milanović, Vitomir
20160801
We present a method for modeling nonparabolicity effects (NPE) in quantum nanostructures in presence of external electric and magnetic field by using second order perturbation theory. The method is applied to analysis of quantum well structure and active region of a quantum cascade laser (QCL). This model will allow us to examine the influence of magnetic field on dipole matrix element in QCL structures, which will provide a better insight to how NPE can affect the gain of QCL structures.

Twisting all the way: From classical mechanics to quantum fields
SciTech Connect
Aschieri, Paolo
20080115
We discuss the effects that a noncommutative geometry induced by a Drinfeld twist has on physical theories. We systematically deform all products and symmetries of the theory. We discuss noncommutative classical mechanics, in particular its deformed Poisson bracket and hence time evolution and symmetries. The twisting is then extended to classical fields, and then to the main interest of this work: quantum fields. This leads to a geometric formulation of quantization on noncommutative spacetime, i.e., we establish a noncommutative correspondence principle from *Poisson brackets to * commutators. In particular commutation relations among creation and annihilation operators are deduced.

Quantum κdeformed differential geometry and field theory
NASA Astrophysics Data System (ADS)
Mercati, Flavio
20160301
I introduce in κMinkowski noncommutative spacetime the basic tools of quantum differential geometry, namely bicovariant differential calculus, Lie and inner derivatives, the integral, the Hodge∗ and the metric. I show the relevance of these tools for field theory with an application to complex scalar field, for which I am able to identify a vectorvalued fourform which generalizes the energymomentum tensor. Its closedness is proved, expressing in a covariant form the conservation of energymomentum.

Is the quantum Hall effect influenced by the gravitational field?
PubMed
Hehl, Friedrich W; Obukhov, Yuri N; Rosenow, Bernd
20040827
Most of the experiments on the quantum Hall effect (QHE) were made at approximately the same height above sea level. A future international comparison will determine whether the gravitational field g(x) influences the QHE. In the realm of (1+2)dimensional phenomenological macroscopic electrodynamics, the OhmHall law is metric independent ("topological"). This suggests that it does not couple to g(x). We corroborate this result by a microscopic calculation of the Hall conductance in the presence of a postNewtonian gravitational field. PMID:15447125

On refractive processes in strong laser field quantum electrodynamics
SciTech Connect
Di Piazza, A.
20131115
Refractive processes in strongfield QED are pure quantum processes, which involve only external photons and the background electromagnetic field. We show analytically that such processes occurring in a planewave field and involving external real photons are all characterized by a surprisingly modest net exchange of energy and momentum with the laser field, corresponding to a few laser photons, even in the limit of ultrarelativistic laser intensities. We obtain this result by a direct calculation of the transition matrix element of an arbitrary refractive QED process and accounting exactly for the background planewave field. A simple physical explanation of this modest net exchange of laser photons is provided, based on the fact that the laser field couples with the external photons only indirectly through virtual electron–positron pairs. For stronger and stronger laser fields, the pairs cover a shorter and shorter distance before they annihilate again, such that the laser can transfer to them an energy corresponding to only a few photons. These results can be relevant for the future experiments aiming to test strongfield QED at present and nextgeneration facilities.  Highlights: •Investigation of the oneloop amplitude of refractive QED processes in a laser field. •The amplitude is suppressed for a large number of netexchanged laser photons. •Suggestion for first observation of highnonlinear vacuum effects in a laser field.

Effect of a magnetic field on intersubband polaritons in a quantum well: strong to weak coupling conversion.
PubMed
Pervishko, A A; Kibis, O V; Shelykh, I A
20160801
We investigate theoretically the effect of a magnetic field on intersubband polaritons in an asymmetric quantum well placed inside an optical resonator. It is demonstrated that the fieldinduced diamagnetic shift of electron subbands in the well increases the broadening of optical lines corresponding to intersubband electron transitions. As a consequence, the magnetic field can switch the polariton system from the regime of strong lightmatter coupling to the regime of a weak one. This effect paves a way for the effective control of polaritonic devices with a magnetic field. PMID:27472627

Effect of a magnetic field on intersubband polaritons in a quantum well: strong to weak coupling conversion
NASA Astrophysics Data System (ADS)
Pervishko, A. A.; Kibis, O. V.; Shelykh, I. A.
20160801
We investigate theoretically the effect of a magnetic field on intersubband polaritons in an asymmetric quantum well placed inside an optical resonator. It is demonstrated that the fieldinduced diamagnetic shift of electron subbands in the well increases the broadening of optical lines corresponding to intersubband electron transitions. As a consequence, the magnetic field can switch the polariton system from the regime of strong lightmatter coupling to the regime of weak one. This effect paves a way to the effective control of polaritonic devices with a magnetic field.

Recent progress of quantum communication in China (Conference Presentation)
NASA Astrophysics Data System (ADS)
Zhang, Qiang
20160401
Quantum communication, based on the quantum physics, can provide information theoretical security. Building a global quantum network is one ultimate goal for the research of quantum information. Here, this talk will review the progress for quantum communication in China, including quantum key distribution over metropolitan area with untrustful relay, field test of quantum entanglement swapping over metropolitan network, the 2000 km quantum key distribution main trunk line, and satellite based quantum communication.

Identifying a cooperative control mechanism between an applied field and the environment of open quantum systems
NASA Astrophysics Data System (ADS)
Gao, Fang; ReydeCastro, Roberto; Wang, Yaoxiong; Rabitz, Herschel; Shuang, Feng
20160501
Many systems under control with an applied field also interact with the surrounding environment. Understanding the control mechanisms has remained a challenge, especially the role played by the interaction between the field and the environment. In order to address this need, here we expand the scope of the Hamiltonianencoding and observabledecoding (HEOD) technique. HEOD was originally introduced as a theoretical and experimental tool for revealing the mechanism induced by control fields in closed quantum systems. The results of opensystem HEOD analysis presented here provide quantitative mechanistic insights into the roles played by a Markovian environment. Two model open quantum systems are considered for illustration. In these systems, transitions are induced by either an applied field linked to a dipole operator or Lindblad operators coupled to the system. For modest control yields, the HEOD results clearly show distinct cooperation between the dynamics induced by the optimal field and the environment. Although the HEOD methodology introduced here is considered in simulations, it has an analogous direct experimental formulation, which we suggest may be applied to open systems in the laboratory to reveal mechanistic insights.

Quantum capacitance of an ultrathin topological insulator film in a magnetic field
PubMed Central
Tahir, M.; Sabeeh, K.; Schwingenschlögl, U.
20130101
We present a theoretical study of the quantum magnetocapacitance of an ultrathin topological insulator film in an external magnetic field. The study is undertaken to investigate the interplay of the Zeeman interaction with the hybridization between the upper and lower surfaces of the thin film. Determining the density of states, we find that the electronhole symmetry is broken when the Zeeman and hybridization energies are varied relative to each other. This leads to a change in the character of the magnetocapacitance at the charge neutrality point. We further show that in the presence of both Zeeman interaction and hybridization the magnetocapacitance exhibits beating at low and splitting of the Shubnikov de Haas oscillations at high perpendicular magnetic field. In addition, we address the crossover from perpendicular to parallel magnetic field and find consistency with recent experimental data. PMID:23405275

Effect of external electric field on the probability of optical transitions in InGaAs/GaAs quantum wells
SciTech Connect
Pikhtin, A. N. Komkov, O. S.; Bazarov, K. V.
20060515
The effect of external electric field on interband optical transitions in single In{sub x}Ga{sub 1x}As/GaAs quantum wells is studied by electroreflectance spectroscopy. A procedure is suggested for separating the contribution of particular exciton transitions to the complicated modulation spectrum. Nontrivial field dependences of the probability of optical transitions forbidden by the symmetry are observed experimentally. The data are compared with the corresponding theoretical dependences. The strength of the internal electric field in the region of the quantum well is determined from FrantzKeldysh's oscillations. Under certain electric fields, the probability of transitions forbidden with no field is higher than the probability of transitions allowed by the symmetry.

Prime Numbers, Quantum Field Theory and the Goldbach Conjecture
NASA Astrophysics Data System (ADS)
SanchisLozano, MiguelAngel; Barbero G., J. Fernando; NavarroSalas, José
20120901
Motivated by the Goldbach conjecture in number theory and the Abelian bosonization mechanism on a cylindrical twodimensional spacetime, we study the reconstruction of a real scalar field as a product of two real fermion (socalled prime) fields whose Fourier expansion exclusively contains prime modes. We undertake the canonical quantization of such prime fields and construct the corresponding Fock space by introducing creation operators bp\\dag — labeled by prime numbers p — acting on the vacuum. The analysis of our model, based on the standard rules of quantum field theory and the assumption of the Riemann hypothesis, allows us to prove that the theory is not renormalizable. We also comment on the potential consequences of this result concerning the validity or breakdown of the Goldbach conjecture for large integer numbers.

Quantum limit on time measurement in a gravitational field
NASA Astrophysics Data System (ADS)
Sinha, Supurna; Samuel, Joseph
20150101
Good clocks are of importance both to fundamental physics and for applications in astronomy, metrology and global positioning systems. In a recent technological breakthrough, researchers at NIST have been able to achieve a stability of one part in 1018 using an ytterbium clock. This naturally raises the question of whether there are fundamental limits to time keeping. In this article we point out that gravity and quantum mechanics set a fundamental limit on the fractional frequency uncertainty of clocks. This limit comes from a combination of the uncertainty relation, the gravitational redshift and the relativistic time dilation effect. For example, a single ion aluminium clock in a terrestrial gravitational field cannot achieve a fractional frequency uncertainty better than one part in 1022. This fundamental limit explores the interaction between gravity and quantum mechanics on a laboratory scale.

Locality and entanglement in bandlimited quantum field theory
NASA Astrophysics Data System (ADS)
Pye, Jason; Donnelly, William; Kempf, Achim
20151101
We consider a model for a Planckscale ultraviolet cutoff which is based on Shannon sampling. Shannon sampling originated in information theory, where it expresses the equivalence of continuous and discrete representations of information. When applied to quantum field theory, Shannon sampling expresses a hard ultraviolet cutoff in the form of a bandlimitation. This introduces nonlocality at the cutoff scale in a way that is more subtle than a simple discretization of space: quantum fields can then be represented as either living on continuous space or, entirely equivalently, as living on any one lattice whose average spacing is sufficiently small. We explicitly calculate vacuum entanglement entropies in 1 +1 dimensions and we find a transition between logarithmic and linear scaling of the entropy, which is the expected 1 +1 dimensional analog of the transition from an area to a volume law. We also use entanglement entropy and mutual information as measures to probe in detail the localizability of the field degrees of freedom. We find that, even though neither translation nor rotation invariance are broken, each field degree of freedom occupies an incompressible volume of space, indicating a finite information density.

Locality and entanglement in bandlimited quantum field theory
NASA Astrophysics Data System (ADS)
Pye, Jason; Donnelly, William; Kempf, Achim
We consider a model for a Planck scale ultraviolet cutoff which is based on Shannon sampling. Shannon sampling originated in information theory, where it expresses the equivalence of continuous and discrete representations of information. When applied to quantum field theory, Shannon sampling expresses a hard ultraviolet cutoff in the form of a bandlimitation. This introduces nonlocality at the cutoff scale in a way that is more subtle than a simple discretization of space: quantum fields can then be represented as either living on continuous space or, entirely equivalently, as living on any one lattice whose average spacing is sufficiently small. We explicitly calculate vacuum entanglement entropies in 1+1 dimensions and we find a transition between logarithmic and linear scaling of the entropy, which is the expected 1+1 dimensional analog of the transition from an area to a volume law. We also use entanglement entropy and mutual information as measures to probe in detail the localizability of the field degrees of freedom. We find that, even though neither translation nor rotation invariance are broken, each field degree of freedom occupies an incompressible volume of space, indicating a finite information density.

On the Mean Field and Classical Limits of Quantum Mechanics
NASA Astrophysics Data System (ADS)
Golse, François; Mouhot, Clément; Paul, Thierry
20160401
The main result in this paper is a new inequality bearing on solutions of the Nbody linear Schrödinger equation and of the mean field Hartree equation. This inequality implies that the mean field limit of the quantum mechanics of N identical particles is uniform in the classical limit and provides a quantitative estimate of the quality of the approximation. This result applies to the case of C 1,1 interaction potentials. The quantity measuring the approximation of the Nbody quantum dynamics by its mean field limit is analogous to the MongeKantorovich (or Wasserstein) distance with exponent 2. The inequality satisfied by this quantity is reminiscent of the work of Dobrushin on the mean field limit in classical mechanics [Func. Anal. Appl. 13, 115123, (1979)]. Our approach to this problem is based on a direct analysis of the Nparticle Liouville equation, and avoids using techniques based on the BBGKY hierarchy or on second quantization.

Pseudopotentialbased electron quantum transport: Theoretical formulation and application to nanometerscale silicon nanowire transistors
NASA Astrophysics Data System (ADS)
Fang, Jingtian; Vandenberghe, William G.; Fu, Bo; Fischetti, Massimo V.
20160101
We present a formalism to treat quantum electronic transport at the nanometer scale based on empirical pseudopotentials. This formalism offers explicit atomistic wavefunctions and an accurate band structure, enabling a detailed study of the characteristics of devices with a nanometerscale channel and body. Assuming externally applied potentials that change slowly along the electrontransport direction, we invoke the envelopewavefunction approximation to apply the open boundary conditions and to develop the transport equations. We construct the fullband open boundary conditions (selfenergies of device contacts) from the complex band structure of the contacts. We solve the transport equations and present the expressions required to calculate the device characteristics, such as device current and charge density. We apply this formalism to study ballistic transport in a gateallaround (GAA) silicon nanowire fieldeffect transistor with a bodysize of 0.39 nm, a gate length of 6.52 nm, and an effective oxide thickness of 0.43 nm. Simulation results show that this device exhibits a subthreshold slope (SS) of ˜66 mV/decade and a draininduced barrierlowering of ˜2.5 mV/V. Our theoretical calculations predict that lowdimensionality channels in a 3D GAA architecture are able to meet the performance requirements of future devices in terms of SS swing and electrostatic control.

Magnetooptical absorption in semiconducting spherical quantum dots: Influence of the dotsize, confining potential, and magnetic field
SciTech Connect
Kushwaha, Manvir S.
20141215
Semiconducting quantum dots – more fancifully dubbed artificial atoms – are quasizero dimensional, tiny, manmade systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement – or the lack of any degree of freedom for the electrons (and/or holes) – in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magnetooptical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of BohmPines’ randomphase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various singleparticle and manyparticle phenomena such as the FockDarwin spectrum; Fermi energy; magnetooptical transitions; probability distribution; and the magnetooptical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magneticfield and dotsize; and exhibits sawtoothlike oscillations at large values of field or dotsize. Unlike laterally confined quantum dots, both (upper and lower) magnetooptical transitions survive even in the extreme instances. However, the intraLandau level

Magnetooptical absorption in semiconducting spherical quantum dots: Influence of the dotsize, confining potential, and magnetic field
NASA Astrophysics Data System (ADS)
Kushwaha, Manvir S.
20141201
Semiconducting quantum dots  more fancifully dubbed artificial atoms  are quasizero dimensional, tiny, manmade systems with charge carriers completely confined in all three dimensions. The scientific quest behind the synthesis of quantum dots is to create and control future electronic and optical nanostructures engineered through tailoring size, shape, and composition. The complete confinement  or the lack of any degree of freedom for the electrons (and/or holes)  in quantum dots limits the exploration of spatially localized elementary excitations such as plasmons to direct rather than reciprocal space. Here we embark on a thorough investigation of the magnetooptical absorption in semiconducting spherical quantum dots characterized by a confining harmonic potential and an applied magnetic field in the symmetric gauge. This is done within the framework of BohmPines' randomphase approximation that enables us to derive and discuss the full Dyson equation that takes proper account of the Coulomb interactions. As an application of our theoretical strategy, we compute various singleparticle and manyparticle phenomena such as the FockDarwin spectrum; Fermi energy; magnetooptical transitions; probability distribution; and the magnetooptical absorption in the quantum dots. It is observed that the role of an applied magnetic field on the absorption spectrum is comparable to that of a confining potential. Increasing (decreasing) the strength of the magnetic field or the confining potential is found to be analogous to shrinking (expanding) the size of the quantum dots: resulting into a blue (red) shift in the absorption spectrum. The Fermi energy diminishes with both increasing magneticfield and dotsize; and exhibits sawtoothlike oscillations at large values of field or dotsize. Unlike laterally confined quantum dots, both (upper and lower) magnetooptical transitions survive even in the extreme instances. However, the intraLandau level transitions are seen

Photoluminescence of ndoped double quantum well—electron subbands under influence of inplane magnetic fields
NASA Astrophysics Data System (ADS)
Orlita, M.; Byszewski, M.; Döhler, G. H.; Grill, M.; Hlídek, P.; Malzer, S.; Zvára, M.
20060801
We report on photoluminescence (PL) measurements of a GaAs/AlGaAs double quantum well (DQW) in high magnetic fields. Measurements were carried out on a selectively contacted symmetric p δnDQW δnp structure, which allows a variation of the electron density in DQW by a pn bias and simultaneously a tilting of DQW, when a pp bias is applied. Attention was paid to phenomena in inplane magnetic fields, theoretically studied by Huang and Lyo (HL), [Phys. Rev. B 59, (1999) 7600]. In this paper, we compare our results for both symmetric and asymmetric DQWs with the theoretical model made by HL. Whereas the spectra from a symmetric DQW fully confirmed the theoretical predictions, the results gained from DQW with an electricfieldinduced asymmetry did not allow a proper study of anticipated effects. The reasons for that are discussed.

Tracing the interwell plasmon in a gridgated doublequantumwell fieldeffect transistor
NASA Astrophysics Data System (ADS)
Popov, Vyacheslav V.; Teperik, Tatiana V.; Zayko, Yuriy N.; Horing, Norman J. M.; Fateev, Denis V.
20050601
The terahertz (THz) absorption spectra of plasmon modes in a gridgated doublequantumwell (DQW) fieldeffect transistor (FET) structute is analyzed theoretically and numerically using the scattering matrix approach and is shown to faithfully reproduce strong resonant features of recent experimental observations of THz photoconductivity in such a structure. No traces ofthe interwell plasmon is found in THz absorption spectra.

Quantum processes in short and intensive electromagnetic fields
NASA Astrophysics Data System (ADS)
Titov, A. I.; Kämpfer, Burkhard; Hosaka, Atsushi; Takabe, Hideaki
20160501
This work provides an overview of our recent results in studying two most important and widely discussed quantum processes: electronpositron pairs production off a probe photon propagating through a polarized shortpulsed electromagnetic (e.g. laser) wave field or generalized BreitWheeler process, and a single a photon emission off an electron interacting with the laser pules, socalled nonlinear Compton scattering. We show that the probabilities of particle production in both processes are determined by interplay of two dynamical effects, where the first one is related to the shape and duration of the pulse and the second one is nonlinear dynamics of the interaction of charged fermions with a strong electromagnetic field. We elaborate suitable expressions for the production probabilities and cross sections, convenient for studying evolution of the plasma in presence of strong electromagnetic fields.

Dynamiclocalfield approximation for the quantum solids
NASA Technical Reports Server (NTRS)
Etters, R. D.; Danilowicz, R. L.
19740101
A localmolecularfield description for the groundstate properties of the quantum solids is presented. The dynamical behavior of atoms contributing to the local field, which acts on an arbitrary pair of test particles, is incorporated by decoupling the pair correlations between these field atoms. The energy, pressure, compressibility, singleparticledistribution function, and the rms atomic deviations about the equilibrium lattice sites are calculated for H2, He3, and He4 over the volume range from 5 to 24.5 cu cm/mole. The results are in close agreement with existing Monte Carlo calculations wherever comparisons are possible. At very high pressure, the results agree with simplified descriptions which depend on negligible overlap of the system wave function between neighboring lattice sites.

Quantum fields near phantomenergy ''sudden'' singularities
SciTech Connect
Calderon, Hector H.
20080815
This paper is committed to calculations near a type of future singularity driven by phantom energy. At the singularities considered, the scale factor remains finite but its derivative diverges. The general behavior of barotropic phantom energy producing this singularity is calculated under the assumption that near the singularity such fluid is the dominant contributor. We use the semiclassical formula for renormalized stress tensors of conformally invariant fields in conformally flat spacetimes and analyze the softening/enhancing of the singularity due to quantum vacuum contributions. This dynamical analysis is then compared to results from thermodynamical considerations. In both cases, the vacuum states of quantized scalar and spinor fields strengthen the accelerating expansion near the singularity whereas the vacuum states of vector fields weaken it.

Quantum entanglement in three accelerating qubits coupled to scalar fields
NASA Astrophysics Data System (ADS)
Dai, Yue; Shen, Zhejun; Shi, Yu
20160701
We consider quantum entanglement of three accelerating qubits, each of which is locally coupled with a real scalar field, without causal influence among the qubits or among the fields. The initial states are assumed to be the GHZ and W states, which are the two representative threepartite entangled states. For each initial state, we study how various kinds of entanglement depend on the accelerations of the three qubits. All kinds of entanglement eventually suddenly die if at least two of three qubits have large enough accelerations. This result implies the eventual sudden death of all kinds of entanglement among three particles coupled with scalar fields when they are sufficiently close to the horizon of a black hole.

Noncommutative Gravity and Quantum Field Theory on Noncommutative Curved Spacetimes
NASA Astrophysics Data System (ADS)
Schenkel, Alexander
20121001
The focus of this PhD thesis is on applications, new developments and extensions of the noncommutative gravity theory proposed by Julius Wess and his group. In part one we propose an extension of the usual symmetry reduction procedure to noncommutative gravity. We classify in the case of abelian Drinfel'd twists all consistent deformations of spatially flat FriedmannRobertsonWalker cosmologies and of the Schwarzschild black hole. The deformed symmetry structure allows us to obtain exact solutions of the noncommutative Einstein equations in many of our models. In part two we develop a new formalism for quantum field theory on noncommutative curved spacetimes by combining methods from the algebraic approach to quantum field theory with noncommutative differential geometry. We also study explicit examples of deformed wave operators and find that there can be noncommutative corrections even on the level of free field theories. The convergent deformation of simple toy models is investigated and it is found that these theories have an improved behaviour at short distances, i.e. in the ultraviolet. In part three we study homomorphisms between and connections on noncommutative vector bundles. We prove that all homomorphisms and connections of the deformed theory can be obtained by applying a quantization isomorphism to undeformed homomorphisms and connections. The extension of homomorphisms and connections to tensor products of bimodules is clarified. As a nontrivial application of the new mathematical formalism we extend our studies of exact noncommutative gravity solutions to more general deformations.

The Nature of Infinity in Quantum Field Calculations
NASA Astrophysics Data System (ADS)
Kriske, Richard
20110501
In many textbooks on Quantum Field Theory it has been noted that an infinity is taken a circle and the flux is calculated from the A field in that manner. There are of course many such examples of this sort of calculation using infinity as a circle. This author would like to point out that if the three dimensions of space are curved and the one dimension of time is not, in say a four space, infinity is the horizon, which is not a circle but rather a sphere; as long as spacetime is curved uniformly, smoothly and has positive curvature. This author believes the math may be in error, since maps of the CMBR seem to indicate a ``SwissCheese'' type of topology, wherein the Sphere at infinity (the Horizon of the Universe), has holes in it that can readily be seen. This author believes that these irregularities most certainly have a calculable effect on QED, QCD and Quantum Field Theory.

Quantum driven dissipative parametric oscillator in a blackbody radiation field
SciTech Connect
Pachón, Leonardo A.; Department of Chemistry and Center for Quantum Information and Quantum Control, Chemical Physics Theory Group, University of Toronto, Toronto, Ontario M5S 3H6 ; Brumer, Paul
20140115
We consider the general open system problem of a charged quantum oscillator confined in a harmonic trap, whose frequency can be arbitrarily modulated in time, that interacts with both an incoherent quantized (blackbody) radiation field and with an arbitrary coherent laser field. We assume that the oscillator is initially in thermodynamic equilibrium with its environment, a nonfactorized initial density matrix of the system and the environment, and that at t = 0 the modulation of the frequency, the coupling to the incoherent and the coherent radiation are switched on. The subsequent dynamics, induced by the presence of the blackbody radiation, the laser field, and the frequency modulation, is studied in the framework of the influence functional approach. This approach allows incorporating, in analytic closed formulae, the nonMarkovian character of the oscillatorenvironment interaction at any temperature as well the nonMarkovian character of the blackbody radiation and its zeropoint fluctuations. Expressions for the time evolution of the covariance matrix elements of the quantum fluctuations and the reduced densityoperator are obtained.

Gauge fields in graphene with nonuniform elastic deformations: A quantum field theory approach
NASA Astrophysics Data System (ADS)
Arias, Enrique; Hernández, Alexis R.; Lewenkopf, Caio
20151201
We investigate the lowenergy continuum limit theory for electrons in a graphene sheet under strain. We use the quantum field theory in curved spaces to analyze the effect of the system deformations into an effective gauge field. We study both inplane and outofplane deformations and obtain a closed expression for the effective gauge field due to arbitrary nonuniform sheet deformations. The obtained results reveal a remarkable relation between the localpseudomagnetic field and the Riemann curvature, so far overlooked.

On the grouptheoretic structure of a class of quantum dialogue protocols
NASA Astrophysics Data System (ADS)
Shukla, Chitra; Kothari, Vivek; Banerjee, Anindita; Pathak, Anirban
20130201
A sufficient condition for implementation of the quantum dialogue protocol is obtained and it is shown that the set of unitary operators used for the purpose must form a group under multiplication. A generalized protocol of quantum dialogue is obtained using the sufficient condition. Further, several examples of possible groups of unitary operators and quantum states that may be used for implementation of quantum dialogue are systematically generated. As examples, it is shown that GHZ state, GHZlike state, W state, 4 and 5qubit Cluster states, Ω state, Brown state, Q4 state and Q5 state can be used to implement quantum dialogue protocol. It is also shown that if a quantum system is found to be suitable for quantum dialogue then that can provide solution of the socialist millionaire problem too.

Quantum field as a quantum cellular automaton: The Dirac free evolution in one dimension
NASA Astrophysics Data System (ADS)
Bisio, Alessandro; D'Ariano, Giacomo Mauro; Tosini, Alessandro
20150301
We present a quantum cellular automaton model in one spacedimension which has the Dirac equation as emergent. This model, a discretetime and causal unitary evolution of a lattice of quantum systems, is derived from the assumptions of homogeneity, parity and timereversal invariance. The comparison between the automaton and the Dirac evolutions is rigorously set as a discrimination problem between unitary channels. We derive an exact lower bound for the probability of error in the discrimination as an explicit function of the mass, the number and the momentum of the particles, and the duration of the evolution. Computing this bound with experimentally achievable values, we see that in that regime the QCA model cannot be discriminated from the usual Dirac evolution. Finally, we show that the evolution of oneparticle states with narrowband in momentum can be efficiently simulated by a dispersive differential equation for any regime. This analysis allows for a comparison with the dynamics of wavepackets as it is described by the usual Dirac equation. This paper is a first step in exploring the idea that quantum field theory could be grounded on a more fundamental quantum cellular automaton model and that physical dynamics could emerge from quantum information processing. In this framework, the discretization is a central ingredient and not only a tool for performing nonperturbative calculation as in lattice gauge theory. The automaton model, endowed with a precise notion of local observables and a full probabilistic interpretation, could lead to a coherent unification of a hypothetical discrete Planck scale with the usual Fermi scale of highenergy physics.

Space–timebounded quantum fields for detection processes
PubMed Central
Aguayo, Fernando J.; Jaroszkiewicz, George
20140101
We discuss a quantum field detection model comprising two types of detection procedures: maximal detection, where the initial state of the system and detectors undergoes an irreversible evolution, and minimal detection, where the system–detector interaction consists of a small, reversible coupling and posterior maximal detection performed over the detector system. Combined, these detection procedures allow for a timedependent description of signalling experiments involving yes/no type of questions. A particular minimal detection model, stable in the presence of the vacuum, is presented and studied, successfully reproducing the localization of the state after a detection. PMID:24711717

Exact integrability in quantum field theory and statistical systems
SciTech Connect
Thacker, H.B.
19810401
The properties of exactly integrable twodimensional quantum systems are reviewed and discussed. The nature of exact integrability as a physical phenomenon and various aspects of the mathematical formalism are explored by discussing several examples, including detailed treatments of the nonlinear Schroedinger (deltafunction gas) model, the massive Thirring model, and the sixvertex (ice) model. The diagonalization of a Hamiltonian by Bethe's Ansatz is illustrated for the nonlinear Schroedinger model, and the integral equation method of Lieb for obtaining the spectrum of the manybody system from periodic boundary conditions is reviewed. Similar methods are applied to the massive Thirring model, where the fermionantifermion and boundstate spectrum are obtained explicitly by the integral equation method. After a brief review of the classical inverse scattering method, the quantum inverse method for the nonlinear Schroedinger model is introduced and shown to be an algebraization of the Bethe Ansatz technique. In the quantum inverse method, an auxiliary linear problem is used to define nonlocal operators which are functionals of the original local field on a fixedtime string of arbitrary length. The particular operators for which the string is infinitely long (free boundary conditions) or forms a closed loop around a cylinder (periodic boundary conditions) correspond to the quantized scattering data and have a special significance. One of them creates the Bethe eigenstates, while the other is the generating function for an infinite number of conservation laws. The analogous operators on a lattice are constructed for the symmetric sixvertex model, where the object which corresponds to a solution of the auxiliary linear problem is a string of vertices contracted over horizontal links (arrows). The relationship between the quantum inverse method and the transfer matrix formalism is exhibited.

Resource Letter QI1: Quantum Information
NASA Astrophysics Data System (ADS)
Strauch, Frederick W.
20160701
This Resource Letter surveys the history and modern developments in the field of quantum information. It is written to guide advanced undergraduates, beginning graduate students, and other new researchers to the theoretical and experimental aspects of this field. The topics covered include quantum states and processes, quantum coding and cryptography, quantum computation, the experimental implementation of quantum information processing, and the role of quantum information in the fundamental properties and foundations of physical theories.

A practical and theoretical definition of very small field size for radiotherapy output factor measurements
SciTech Connect
Charles, P. H. Crowe, S. B.; Langton, C. M.; Trapp, J. V.; CranmerSargison, G.; Thwaites, D. I.; Kairn, T.; Knight, R. T.; Kenny, J.
20140415
Purpose: This work introduces the concept of very small field size. Output factor (OPF) measurements at these field sizes require extremely careful experimental methodology including the measurement of dosimetric field size at the same time as each OPF measurement. Two quantifiable scientific definitions of the threshold of very small field size are presented. Methods: A practical definition was established by quantifying the effect that a 1 mm error in field size or detector position had on OPFs and setting acceptable uncertainties on OPF at 1%. Alternatively, for a theoretical definition of very small field size, the OPFs were separated into additional factors to investigate the specific effects of lateral electronic disequilibrium, photon scatter in the phantom, and source occlusion. The dominant effect was established and formed the basis of a theoretical definition of very small fields. Each factor was obtained using Monte Carlo simulations of a Varian iX linear accelerator for various square field sizes of side length from 4 to 100 mm, using a nominal photon energy of 6 MV. Results: According to the practical definition established in this project, field sizes ≤15 mm were considered to be very small for 6 MV beams for maximal field size uncertainties of 1 mm. If the acceptable uncertainty in the OPF was increased from 1.0% to 2.0%, or field size uncertainties are 0.5 mm, field sizes ≤12 mm were considered to be very small. Lateral electronic disequilibrium in the phantom was the dominant cause of change in OPF at very small field sizes. Thus the theoretical definition of very small field size coincided to the field size at which lateral electronic disequilibrium clearly caused a greater change in OPF than any other effects. This was found to occur at field sizes ≤12 mm. Source occlusion also caused a large change in OPF for field sizes ≤8 mm. Based on the results of this study, field sizes ≤12 mm were considered to be theoretically very small for 6

Giant effective mass deviations near the magnetic fieldinduced minigap in double quantum wells
SciTech Connect
Harff, N.E. ; Simmons, J.A.; Lyo, S.K.; Klem, J.F.; Goodnick, S.M.
19940901
The authors report major deviations in the electron effective mass m* near the partial energy gap, or minigap, formed in strongly coupled double quantum wells (QWs) by an anticrossing of the two QW dispersion curves. The anticrossing and minigap are induced by an inplane magnetic field B{sub {parallel}} and give rise to large distortions in the Fermi surface and density of states, including a Van Hove singularity. Sweeping B{sub {parallel}} moves the minigap through the Fermi level, with the upper and lower gap edges producing a sharp maximum and minimum in the lowtemperature inplane conductance, in agreement with theoretical calculations. The temperature dependence of Shubnikovde Haas (SdH) oscillations appearing in a tilted magnetic field yield a decreased m* {le} 1/3 m*{sub GaAs} near the upper gap edge, and indicate an increase in m* near the lower gap edge.

AbInitio Hamiltonian Approach to Light Nuclei And to Quantum Field Theory
SciTech Connect
Vary, J.P.; Honkanen, H.; Li, Jun; Maris, P.; Shirokov, A.M.; Brodsky, S.J.; Harindranath, A.; de Teramond, G.F.; Ng, E.G.; Yang, C.; Sosonkina, M.; /Ames Lab
20120622
Nuclear structure physics is on the threshold of confronting several longstanding problems such as the origin of shell structure from basic nucleonnucleon and threenucleon interactions. At the same time those interactions are being developed with increasing contact to QCD, the underlying theory of the strong interactions, using effective field theory. The motivation is clear  QCD offers the promise of great predictive power spanning phenomena on multiple scales from quarks and gluons to nuclear structure. However, new tools that involve nonperturbative methods are required to build bridges from one scale to the next. We present an overview of recent theoretical and computational progress with a Hamiltonian approach to build these bridges and provide illustrative results for the nuclear structure of light nuclei and quantum field theory.

Quantum Interference, Geometricphase Effects, and Semiclassical Transport in Quantum Hall Systems at Low Magnetic Fields
NASA Astrophysics Data System (ADS)
Huang, ChunFeng; Tsai, I.H.
It is wellestablished how the quantum interference induces strong localization leading to quantum Hall effect at high enough magnetic fields. Decreasing the magnetic fields, however, the localization strength can be reduced and the semiclassical magnetooscillations following Shubnikovde Haas formula appear in most quantum Hall systems. To understand the transport properties as the localization strength becomes weak, our team has investigated the magnetoresistance in some quantum Hall systems at low magnetic fields. Under the semiclassical transport, the crossing points in Hall plateaus showed Landauband quantization and microwaveinduced heating demonstrated the bandedge equivalence important to Landaulevel addition transformation. We note that such equivalence is consistent with the edge universality based on the random matrices of Wigner type, and the Landauband quantization can be explained by considering geometric phase effects. From our study, some quantum Hall features can survive as the semiclassical transport reveals the insufficient localization.

Theoretical calculation of zero field splitting parameters of Cr3+ doped ammonium oxalate monohydrate
NASA Astrophysics Data System (ADS)
Kripal, Ram; Yadav, Awadhesh Kumar
20150601
Zero field splitting parameters (ZFSPs) D and E of Cr3+ ion doped ammonium oxalate monohydrate (AOM) are calculated with formula using the superposition model. The theoretically calculated ZFSPs for Cr3+ in AOM crystal are compared with the experimental value obtained by electron paramagnetic resonance (EPR). Theoretical ZFSPs are in good agreement with the experimental ones. The energy band positions of optical absorption spectra of Cr3+ in AOM crystal calculated with CFA package are in good match with the experimental values.

Theoretical Study of AllElectrical Quantum Wire Valley Filters in Bilayer Graphene
NASA Astrophysics Data System (ADS)
Wu, YuShu; Lue, NingYuan; Chen, YenChun; Jiang, JiaHuei; Chou, MeiYin
Graphene electrons carry valley pseudospin, due to the double valley degeneracy in graphene band structure. In gapped graphene, the pseudospin is coupled to an inplane electric field, through the mechanism of valleyorbit interaction (VOI), Based on the VOI, a family of electricallycontrolled valleytronic devices have been proposed. Here, we report the theoretical study of a recently proposed valley filter consisting of a Q1D channel in bilayer graphene defined and controlled by electrical gates. We discuss two types of calculations  those of energy subband structure in the channel and electron transmission through a valley valve consisting of two proposed filters. For the former, we have developed a tight binding formulation in the continuum limit. For the latter, we employ the recursive Green's function method. Results from the calculations will be presented. Financial support by MoST, Taiwan, ROC is acknowledged.

Reconstruction of exciton wave functions of coupled quantum emitters including spin with ultrafast spectroscopy using localized nanooptical fields
NASA Astrophysics Data System (ADS)
Specht, Judith F.; Richter, Marten
20160401
Coulombinduced resonance energy transfer mechanisms between coupled nanostructures lead to the formation of new, delocalized exciton states. Their hybrid wave functions can be decomposed into the basis of local states of the uncoupled system by the use of coherent, spatially resolved spectroscopy. The suggested quantum state tomography protocol combines nanooptical fields with a fourwave mixing technique: At least one pulse of the pulse sequence is spatially localized at a specific quantum emitter. It was suggested to use nanoplasmonic structures together with pulseshaped fields for the localization. In this paper, the method is applied to a system of two coupled semiconductor quantum dots. The basic reconstruction concept first proposed in Richter et al. (Phys Rev B 86:085308, 2012) and Schlosser et al. (New J Phys 15:025004, 2013) is extended to the case of including different spin states of the excitons in the quantum dots. For this purpose, the theoretical scheme has to be modified and the localized fields need the ability to change their polarization. We show that the application of the developed reconstruction scheme to twodimensional spectra gives full access to the internal structure of the interacting quantum states.

New method of applying conformal group to quantum fields
NASA Astrophysics Data System (ADS)
Han, Lei; Wang, HaiJun
20150901
Most of previous work on applying the conformal group to quantum fields has emphasized its invariant aspects, whereas in this paper we find that the conformal group can give us running quantum fields, with some constants, vertex and Green functions running, compatible with the scaling properties of renormalization group method (RGM). We start with the renormalization group equation (RGE), in which the differential operator happens to be a generator of the conformal group, named dilatation operator. In addition we link the operator/spatial representation and unitary/spinor representation of the conformal group by inquiring a conformalinvariant interaction vertex mimicking the similar process of Lorentz transformation applied to Dirac equation. By this kind of application, we find out that quite a few interaction vertices are separately invariant under certain transformations (generators) of the conformal group. The significance of these transformations and vertices is explained. Using a particular generator of the conformal group, we suggest a new equation analogous to RGE which may lead a system to evolve from asymptotic regime to nonperturbative regime, in contrast to the effect of the conventional RGE from nonperturbative regime to asymptotic regime. Supported by NSFC (91227114)

Entertainment Computing, Social Transformation and the Quantum Field
NASA Astrophysics Data System (ADS)
Rauterberg, Matthias
The abstract should summaritinment computing is on its way getting an established academic discipline. The scope of entertainment computing is quite broad (see the scope of the international journal Entertainment Computing). One unifying idea in this diverse community of entertainment researchers and developers might be a normative position to enhance human living through social transformation. One possible option in this direction is a shared ‘conscious’ field. Several ideas about a new kind of field based on quantum effects are presented and discussed. Assuming that social transformation is based on a shared collective unconscious I propose designing entertainment technology for a new kind of user experience that can transform in a positive manner the individual unconscious and therefore the collective unconscious as well. Our ALICE project can be seen as a first attempt in this direction.

Effective field theory of quantum gravity coupled to scalar electrodynamics
NASA Astrophysics Data System (ADS)
Ibiapina Bevilaqua, L.; Lehum, A. C.; da Silva, A. J.
20160501
In this work, we use the framework of effective field theory to couple Einstein’s gravity to scalar electrodynamics and determine the renormalization of the model through the study of physical processes below Planck scale, a realm where quantum mechanics and general relativity are perfectly compatible. We consider the effective field theory up to dimension six operators, corresponding to processes involving onegraviton exchange. Studying the renormalization group functions, we see that the beta function of the electric charge is positive and possesses no contribution coming from gravitational interaction. Our result indicates that gravitational corrections do not alter the running behavior of the gauge coupling constants, even if massive particles are present.

Model for noncancellation of quantum electric field fluctuations
SciTech Connect
Parkinson, Victor; Ford, L. H.
20111215
A localized charged particle oscillating near a reflecting boundary is considered as a model for noncancellation of vacuum fluctuations. Although the mean velocity of the particle is sinusoidal, the velocity variance produced by vacuum fluctuations can either grow or decrease linearly in time, depending upon the product of the oscillation frequency and the distance to the boundary. This amounts to heating or cooling arising from noncancellation of electric field fluctuations, which are otherwise anticorrelated in time. Similar noncancellations arise in quantum field effects in timedependent curved spacetimes. We give some estimates of the magnitude of the effect, and discuss its potential observability. We also compare the effects of vacuum fluctuations with the shot noise due to emission of a finite number of photons. We find that the two effects can be comparable in magnitude, but have distinct characteristics, and hence could be distinguished in an experiment.

Quantum field theory for the threebody constrained lattice Bose gas. I. Formal developments
NASA Astrophysics Data System (ADS)
Diehl, S.; Baranov, M.; Daley, A. J.; Zoller, P.
20100801
We develop a quantum field theoretical framework to analytically study the threebody constrained BoseHubbard model beyond mean field and noninteracting spin wave approximations. It is based on an exact mapping of the constrained model to a theory with two coupled bosonic degrees of freedom with polynomial interactions, which have a natural interpretation as single particles and twoparticle states. The procedure can be seen as a proper quantization of the Gutzwiller mean field theory. The theory is conveniently evaluated in the framework of the quantum effective action, for which the usual symmetry principles are now supplemented with a “constraint principle” operative on short distances. We test the theory via investigation of scattering properties of few particles in the limit of vanishing density, and we address the complementary problem in the limit of maximum filling, where the lowlying excitations are holes and diholes on top of the constraintinduced insulator. This is the first of a sequence of two papers. The application of the formalism to the manybody problem, which can be realized with atoms in optical lattices with strong threebody loss, is performed in a related work [S. Diehl, M. Baranov, A. Daley, and P. Zoller, Phys. Rev. B 82, 064510 (2010)10.1103/PhysRevB.82.064510].

Quantum field theory for the threebody constrained lattice Bose gas. I. Formal developments
SciTech Connect
Diehl, S.; Daley, A. J.; Zoller, P.; Baranov, M.
20100801
We develop a quantum field theoretical framework to analytically study the threebody constrained BoseHubbard model beyond mean field and noninteracting spin wave approximations. It is based on an exact mapping of the constrained model to a theory with two coupled bosonic degrees of freedom with polynomial interactions, which have a natural interpretation as single particles and twoparticle states. The procedure can be seen as a proper quantization of the Gutzwiller mean field theory. The theory is conveniently evaluated in the framework of the quantum effective action, for which the usual symmetry principles are now supplemented with a ''constraint principle'' operative on short distances. We test the theory via investigation of scattering properties of few particles in the limit of vanishing density, and we address the complementary problem in the limit of maximum filling, where the lowlying excitations are holes and diholes on top of the constraintinduced insulator. This is the first of a sequence of two papers. The application of the formalism to the manybody problem, which can be realized with atoms in optical lattices with strong threebody loss, is performed in a related work [S. Diehl, M. Baranov, A. Daley, and P. Zoller, Phys. Rev. B 82, 064510 (2010)].

Quantum mechanical solver for confined heterostructure tunnel fieldeffect transistors
SciTech Connect
Verreck, Devin Groeseneken, Guido; Van de Put, Maarten; Sorée, Bart; Magnus, Wim; Verhulst, Anne S.; Collaert, Nadine; Thean, Aaron; Vandenberghe, William G.
20140207
Heterostructure tunnel fieldeffect transistors (HTFET) are promising candidates for lowpower applications in future technology nodes, as they are predicted to offer high oncurrents, combined with a sub60 mV/dec subthreshold swing. However, the effects of important quantum mechanical phenomena like size confinement at the heterojunction are not well understood, due to the theoretical and computational difficulties in modeling realistic heterostructures. We therefore present a ballistic quantum transport formalism, combining a novel envelope function approach for semiconductor heterostructures with the multiband quantum transmitting boundary method, which we extend to 2D potentials. We demonstrate an implementation of a 2band version of the formalism and apply it to study confinement in realistic heterostructure diodes and pnin HTFETs. For the diodes, both transmission probabilities and current densities are found to decrease with stronger confinement. For the pnin HTFETs, the improved gate control is found to counteract the deterioration due to confinement.

NonGaussian quantum states generation and robust quantum nonGaussianity via squeezing field
NASA Astrophysics Data System (ADS)
Tang, XuBing; Gao, Fang; Wang, YaoXiong; Kuang, Sen; Shuang, Feng
20150301
Recent studies show that quantum nonGaussian states or using nonGaussian operations can improve entanglement distillation, quantum swapping, teleportation, and cloning. In this work, employing a strategy of nonGaussian operations (namely subtracting and adding a single photon), we propose a scheme to generate nonGaussian quantum states named singlephotonadded and subtracted coherent (SPASC) superposition states by implementing Bell measurements, and then investigate the corresponding nonclassical features. By squeezed the input field, we demonstrate that robustness of nonGaussianity can be improved. Controllable phase space distribution offers the possibility to approximately generate a displaced coherent superposition states (DCSS). The fidelity can reach up to F ≥ 0.98 and F ≥ 0.90 for size of amplitude z = 1.53 and 2.36, respectively. Project supported by the National Natural Science Foundation of China (Grant Nos. 61203061 and 61074052), the Outstanding Young Talent Foundation of Anhui Province, China (Grant No. 2012SQRL040), and the Natural Science Foundation of Anhui Province, China (Grant No. KJ2012Z035).

PREFACE: Quantum Field Theory Under the Influence of External Conditions (QFEXT07)
NASA Astrophysics Data System (ADS)
Bordag, M.; Mostepanenko, V. M.
20080401
This special issue contains papers reflecting talks presented at the 8th Workshop on Quantum Field Theory Under the Influence of External Conditions (QFEXT07), held on 17 21 September 2007, at Leipzig University. This workshop gathered 108 physicists and mathematicians working on problems which are focused on the following topics: •Casimir and van der Waals forces—progress in theory and new experiments, applications at micro and nanoscale •Casimir effect—exact results, approximate methods and mathematical problems •Vacuum quantum effects in classical background fields—renormalization issues, singular backgrounds, applications to particle and high energy physics •Vacuum energy and gravity, vacuum energy in supersymmetric and noncommutative theories. This workshop is part of a series started in 1989 and 1992 in Leipzig by Dieter Robaschik, and continued in 1995, 1998 and 2001 in Leipzig by Michael Bordag. In 2003 this Workshop was organized by Kimball A Milton in Oklahoma, in 2005 by Emilio Elizalde in Barcelona and in 2007 it returned to Leipzig. The field of physics after which this series of workshops is named is remarkably broad. It stretches from experimental work on the measurement of dispersion forces between macroscopic bodies to quantum corrections in the presence of classical background fields. The underlying physical idea is that even in its ground state (vacuum) a quantum system responds to changes in its environment. The universality of this idea makes the field of its application so very broad. The most prominent manifestation of vacuum energy is the Casimir effect. This is, in its original formulation, the attraction between conducting planes due to the vacuum fluctuations of the electromagnetic field. In a sense, this is the longrange tail of the more general dispersion forces acting between macroscopic bodies. With the progress in nanotechnology, dispersion forces become of direct practical significance. On a more theoretical side

Quantum cryptography: Theoretical protocols for quantum key distribution and tests of selected commercial QKD systems in commercial fiber networks
NASA Astrophysics Data System (ADS)
Jacak, Monika; Jacak, Janusz; Jóźwiak, Piotr; Jóźwiak, Ireneusz
20160601
The overview of the current status of quantum cryptography is given in regard to quantum key distribution (QKD) protocols, implemented both on nonentangled and entangled flying qubits. Two commercial R&D platforms of QKD systems are described (the Clavis II platform by idQuantique implemented on nonentangled photons and the EPR S405 Quelle platform by AIT based on entangled photons) and tested for feasibility of their usage in commercial TELECOM fiber metropolitan networks. The comparison of systems efficiency, stability and resistivity against noise and hacker attacks is given with some suggestion toward system improvement, along with assessment of two models of QKD.

Theoretical investigation of zero field splitting parameter of Cr3+ doped diammonium hexaaqua magnesium sulfate
NASA Astrophysics Data System (ADS)
Kripal, Ram; Yadav, Awadhesh Kumar
20150101
The zero field splitting parameter D of Cr3+ doped diammonium hexaaqua magnesium sulfate (DHMS) are calculated with perturbation formula using crystal field (CF) parameters from superposition model. The theoretically calculated ZFS parameters for Cr3+ in DHMS single crystal are compared with the experimental value obtained by electron paramagnetic resonance (EPR). The theoretical ZFS parameter D is similar to that from experiment. The energy band positions of optical absorption spectra of Cr3+ doped DHMS single crystal are calculated with CFA package, which are in good match with experimental values.

Probing the effective nuclearspin magnetic field in a single quantum dot via full counting statistics
SciTech Connect
Xue, HaiBin; Nie, YiHang; Chen, Jingzhe; Ren, Wei
20150315
We study theoretically the full counting statistics of electron transport through a quantum dot weakly coupled to two ferromagnetic leads, in which an effective nuclearspin magnetic field originating from the configuration of nuclear spins is considered. We demonstrate that the quantum coherence between the two singlyoccupied eigenstates and the spin polarization of two ferromagnetic leads play an important role in the formation of superPoissonian noise. In particular, the orientation and magnitude of the effective field have a significant influence on the variations of the values of highorder cumulants, and the variations of the skewness and kurtosis values are more sensitive to the orientation and magnitude of the effective field than the shot noise. Thus, the highorder cumulants of transport current can be used to qualitatively extract information on the orientation and magnitude of the effective nuclearspin magnetic field in a single quantum dot.  Highlights: • The effective nuclearspin magnetic field gives rise to the offdiagonal elements of the reduced density matrix of single QD. • The offdiagonal elements of reduced density matrix of the QD have a significant impact on the highorder current cumulants. • The highorder current cumulants are sensitive to the orientation and magnitude of the effective nuclearspin magnetic field. • The FCS can be used to detect the orientation and magnitude of the effective nuclearspin magnetic field in a single QD.

Nonequilibrium entropy in classical and quantum field theory
NASA Astrophysics Data System (ADS)
Kandrup, Henry E.
19870601
This paper proposes a definition of nonequilibrium entropy appropriate for a bosonic classical or quantum field, viewed as a collection of oscillators with equations of motion which satisfy a Liouville theorem (as is guaranteed for a Hamiltonian system). This entropy S is constructed explicitly to provide a measure of correlations and, as such, is conserved absolutely in the absence of couplings between degrees of freedom. This means, e.g., that there can be no entropy generation for a sourcefree linear field in flat space, but that S need no longer be conserved in the presence of couplings induced by nonlinearities, material sources, or a nontrivial dynamical background spacetime. Moreover, through the introduction of a ``subdynamics,'' it is proved that, in the presence of such couplings, the entropy will satisfy an Htheorem inequality, at least in one particular limit. Specifically, if at some initial time t0 the field is free of any correlations, it then follows rigorously that, at time t0+Δt, the entropy will be increasing: dS/dt>0. Similar arguments demonstrate that this S is the only measure of ``entropy'' consistent mathematically with the subdynamics. It is argued that this entropy possesses an intrinsic physical meaning, this meaning being especially clear in the context of a quantum theory, where a direct connection exists between entropy generation and particle creation. Reasonable conjectures regarding the more general time dependence of the entropy, which parallel closely the conventional wisdom of particle mechanics, lead to an interpretation of S which corroborates one's naive intuition as to the behavior of an ``entropy.''

Mass Charge Interactions for Visualizing the Quantum Field
NASA Astrophysics Data System (ADS)
Baer, Wolfgang
Our goal is to integrate the objective and subjective aspects of our personal experience into a single complete theory of reality. To further this endeavor we replace elementary particles with elementary events as the building blocks of an event oriented description of that reality. The simplest event in such a conception is an adaptation of A. Wheeler's primitive explanatorymeasurement cycle between internal observations experienced by an observer and their assumed physical causes. We will show how internal forces between charge and mass are required to complete the cyclic sequence of activity. This new formulation of internal material is easier to visualize and map to cognitive experiences than current formulations of subatomic physics. In our formulation, called Cognitive Action Theory, such internal forces balance the external forces of gravityinertia and electricitymagnetism. They thereby accommodate outside influences by adjusting the internal structure of material from which all things are composed. Such accommodation is interpreted as the physical implementation of a model of the external physical world in the brain of a cognitive being or alternatively the response mechanism to external influences in the material of inanimate objects. We adopt the deBroglieBohm causal interpretation of QT to show that the nature of space in our model is mathematically equivalent to a field of clocks. Within this field small oscillations form deBroglie waves. This interpretation allows us to visualize the underlying structure of empty space with a chargemass separation field in equilibrium, and objects appearing in space with quantum wave disturbances to that equilibrium occurring inside material. Space is thereby associated with the internal structure of material and quantum mechanics is shown to be, paraphrasing Heisenberg, the physics of the material that knows the world.

Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction
PubMed Central
Müller, Knut; Krause, Florian F.; Béché, Armand; Schowalter, Marco; Galioit, Vincent; Löffler, Stefan; Verbeeck, Johan; Zweck, Josef; Schattschneider, Peter; Rosenauer, Andreas
20140101
By focusing electrons on probes with a diameter of 50 pm, aberrationcorrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a fieldinduced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented brightfield detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and highcontrast imaging of light atoms. PMID:25501385

Determining polarizable force fields with electrostatic potentials from quantum mechanical linear response theory.
PubMed
Wang, Hao; Yang, Weitao
20160614
We developed a new method to calculate the atomic polarizabilities by fitting to the electrostatic potentials (ESPs) obtained from quantum mechanical (QM) calculations within the linear response theory. This parallels the conventional approach of fitting atomic charges based on electrostatic potentials from the electron density. Our ESP fitting is combined with the induced dipole model under the perturbation of uniform external electric fields of all orientations. QM calculations for the linear response to the external electric fields are used as input, fully consistent with the induced dipole model, which itself is a linear response model. The orientation of the uniform external electric fields is integrated in all directions. The integration of orientation and QM linear response calculations together makes the fitting results independent of the orientations and magnitudes of the uniform external electric fields applied. Another advantage of our method is that QM calculation is only needed once, in contrast to the conventional approach, where many QM calculations are needed for many different applied electric fields. The molecular polarizabilities obtained from our method show comparable accuracy with those from fitting directly to the experimental or theoretical molecular polarizabilities. Since ESP is directly fitted, atomic polarizabilities obtained from our method are expected to reproduce the electrostatic interactions better. Our method was used to calculate both transferable atomic polarizabilities for polarizable molecular mechanics' force fields and nontransferable moleculespecific atomic polarizabilities. PMID:27305996

Field dependence of gaseousion mobility  Theoretical tests of approximate formulas.
NASA Technical Reports Server (NTRS)
Hahn, H.; Mason, E. A.
19720101
The approximate formulas considered include relations based on the Wannier freeflight theory, the Kihara mediumfield expansion, and the FrostPatterson interpolation formulas. A few accurate theoretical results are available for testing the foregoing formulas. Cases concerning high fields, intermediate fields, and resonant charge transfer are examined. It is found that of the formulas tested, the one based on the Wannier freeflight theory is the most flexible, since it can be used for all fields and all ionneutral force laws and mass ratios.

Trivial pursuits: studies in quantum field theory and squantum cosmology
SciTech Connect
Furlong, R.C.
19870101
The author show that the nonrelativistic limit of the lambdaphi/sup 4/ theory is trivial in 1 + 3 dimensions; the renormalized coupling constant vanishes and the S matrix reduces to the unit matrix. Our result is consistent with, though not sufficient to establish, the triviality of the Lorentzinvariant theory. A necessary condition for the existence of a consistent nontrivial continuum quantum field theory in d = 4 is the existence of an ultravioletstable fixed point of the GellMannLow renormalization group. Since others have shown (nonperturbatively) that the existence of just such a fixed point is sufficient to guarantee the triviality of the continuum massless WessZumino model, we conclude that this model cannot exist nontrivially in d = 4. The fact that most renormalization group blocking schemes include each site link in many block links can generate spurious interactions in the block system. A general method for avoiding this problem is formulated and applied to do a Monte Carlo renormalization group study of the SU(2)Higgs model in four dimensions with a check 2 scale factor. Finally starting from the D'Eath equation, the Dirac square root of the WheelerDe Witt equation, for N = 1 supergravity, we construct superminisuperspace models (and quasimodels) for supersymmetric quantum cosmology (squantum cosmology) compatibile with FriedmannRobertsonWalker (FRW) cosmologies.

Comparison of Boltzmann equations with quantum dynamics for scalar fields
SciTech Connect
Lindner, Manfred; Mueller, Markus Michael
20060615
Boltzmann equations are often used to study the thermal evolution of particle reaction networks. Prominent examples are the computation of the baryon asymmetry of the universe and the evolution of the quarkgluon plasma after relativistic heavy ion collisions. However, Boltzmann equations are only a classical approximation of the quantum thermalization process which is described by the socalled KadanoffBaym equations. This raises the question how reliable Boltzmann equations are as approximations to the full KadanoffBaym equations. Therefore, we present in this paper a detailed comparison between the KadanoffBaym and Boltzmann equations in the framework of a scalar {phi}{sup 4} quantum field theory in 3+1 spacetime dimensions. The obtained numerical solutions reveal significant discrepancies in the results predicted by both types of equations. Apart from quantitative discrepancies, on a qualitative level the universality respected by the KadanoffBaym equations is severely restricted in the case of Boltzmann equations. Furthermore, the KadanoffBaym equations strongly separate the time scales between kinetic and chemical equilibration. This separation of time scales is absent for the Boltzmann equation.

Universal behavior after a quantum quench in interacting field theories
NASA Astrophysics Data System (ADS)
Mitra, Aditi
The dynamics of an isolated quantum system represented by a field theory with O(N) symmetry, and in d>2 spatial dimensions, is investigated after a quantum quench from a disordered initial state to the critical point. A perturbative renormalizationgroup approach involving an expansion around d=4 is employed to study the timeevolution, and is supplemented by an exact solution of the HartreeFock equations in the largeN limit. The results show that the dynamics is characterized by a prethermal regime controlled by elastic dephasing where excitations propagate ballistically, and a light cone emerges in correlation functions in real space. The memory of the initial state, together with the absence of timescales at the critical point, gives rise to universal powerlaw aging which is characterized by a new nonequilibrium shorttime exponent. The dynamics of the entanglement following a quench is also explored, and reveals that while the time evolution of the entanglement entropy itself is not much different between a free bosonic theory and an interacting bosonic theory, the lowenergy entanglement spectrum on the other hand shows clear signature of the nonequilibrium shorttime exponent related to aging. This work was done in collaboration with Y. Lemonik (NYU), M. Tavora (NYU), A. Chiocchetta (SISSA), A. Maraga (SISSA), and A. Gambassi (SISSA). Supported by NSFDMR 1303177.

Twodimensional quantum walk under artificial magnetic field
NASA Astrophysics Data System (ADS)
Yalçınkaya, I.; Gedik, Z.
20151001
We introduce the Peierls substitution to a twodimensional discretetime quantum walk on a square lattice to examine the spreading dynamics and the coinposition entanglement in the presence of an artificial gauge field. We use the ratio of the magnetic flux through the unit cell to the flux quantum as a control parameter. For a given flux ratio, we obtain faster spreading for a small number of steps and the walker tends to be highly localized around the origin. Moreover, the spreading of the walk can be suppressed and decreased within a limited time interval for specific rational values of flux ratio. When the flux ratio is an irrational number, even for a large number of steps, the spreading exhibits diffusive behavior rather than the wellknown ballistic one as in the classical random walk and there is a significant probability of finding the walker at the origin. We also analyze the coinposition entanglement and show that the asymptotic behavior vanishes when the flux ratio is different from zero and the coinposition entanglement become nearly maximal in a periodic manner in a long time range.

Quantum Hall effect in fieldinduced spin density wave systems
NASA Astrophysics Data System (ADS)
Tevosyan, Kahren
The research work described in this thesis is motivated by recent theoretical and experimental studies of the Quantum Hall Effect (QHE) in the quasionedimensional conductors such as organic metals of the (TMTSF)sb2X family. These materials consist of weakly coupled parallel conducting chains that lie in the same plane. They exhibit very interesting behavior in the presence of a strong magnetic field which is perpendicular to the plane. At low temperatures a series of phase transitions from the metallic state to spin density wave states occur with increasing magnetic field. The latter are called the FieldInduced Spin Density Wave (FISDW) states. Within each FISDW phase, the value of the Hall resistance is quantized, signalling the presence of the Quantum Hall Effect. In contrast with the conventional QHE in isotropic twodimensional systems, finitewidth Landau bands appear naturally in the disorderfree (TMTSF)sb2X materials. In fact, the theory of the QHE in quasionedimensiona1 organic conductors has so far been developed without any consideration of the effect of the disorder required to broaden Landau bands in isotropic systems. Here we address for the first time the localization properties of the quantum states in FISDW Landau bands. We employ the Thouless approach which uses the sensitivity of the eigenvalues to the choice of boundary conditions to study localization. Our results show that the localization properties of the states are very different from those of the conventional QHE systems. We find that the Thouless numbers do not decrease exponentially with the system size, indicating that states are not localized on the scales we can study. Another aspect of the dissertation deals with the edge state picture of the QHE which states that gapless excitations localized at the system edge are present whenever the quantum Hall effect occurs. We examine these properties of edge states for the FISDW systems by performing computer simulations to model the

Effective field theory for quantum liquid in dwarf stars
SciTech Connect
Gabadadze, Gregory; Rosen, Rachel A. Email: rarosen@physik.su.se
20100401
An effective field theory approach is used to describe quantum matter at greaterthanatomic but lessthannuclear densities which are encountered in white dwarf stars. We focus on the density and temperature regime for which charged spin0 nuclei form an interacting charged BoseEinstein condensate, while the neutralizing electrons form a degenerate fermi gas. After a brief introductory review, we summarize distinctive properties of the charged condensate, such as a mass gap in the bosonic sector as well as gapless fermionic excitations. Charged impurities placed in the condensate are screened with great efficiency, greater than in an equivalent uncondensed plasma. We discuss a generalization of the Friedel potential which takes into account bosonic collective excitations in addition to the fermionic excitations. We argue that the charged condensate could exist in heliumcore white dwarf stars and discuss the evolution of these dwarfs. Condensation would lead to a significantly faster rate of cooling than that of carbon or oxygencore dwarfs with crystallized cores. This prediction can be tested observationally: signatures of charged condensation may have already been seen in the recently discovered sequence of heliumcore dwarfs in the nearby globular cluster NGC 6397. Sufficiently strong magnetic fields can penetrate the condensate within Abrikosovlike vortices. We find approximate analytic vortex solutions and calculate the values of the lower and upper critical magnetic fields at which vortices are formed and destroyed respectively. The lower critical field is within the range of fields observed in white dwarfs, but tends toward the higher end of this interval. This suggests that for a significant fraction of heliumcore dwarfs, magnetic fields are entirely expelled within the core.

Realtime quantum trajectories for classically allowed dynamics in strong laser fields
NASA Astrophysics Data System (ADS)
Plimak, L. I.; Ivanov, Misha Yu.
20151001
Both the physical picture of the dynamics of atoms and molecules in intense infrared fields and its theoretical description use the concept of electron trajectories. Here, we address a key question which arises in this context: Are distinctly quantum features of these trajectories, such as the complexvalued coordinates, physically relevant in the classically allowed region of phase space, and what is their origin? First, we argue that solutions of classical equations of motion can account for quantum effects. To this end, we construct an exact solution to the classical HamiltonJacobi equation which accounts for dynamics of the wave packet, and show that this solution is physically correct in the limit ?. Second, we show that imaginary components of classical trajectories are directly linked to the finite size of the initial wave packet in momentum space. This way, if the electronic wave packet produced by optical tunnelling in strong infrared fields is localised both in coordinate and momentum, its motion after tunnelling ipso facto cannot be described with purely classical trajectories  in contrast to popular models in the literature.

Cyclotron resonance in InAs/AlSb quantum wells in magnetic fields up to 45 T
SciTech Connect
Spirin, K. E. Krishtopenko, S. S.; Sadofyev, Yu. G.; Drachenko, O.; Helm, M.; Teppe, F.; Knap, W.; Gavrilenko, V. I.
20151215
Electron cyclotron resonance in InAs/AlSb heterostructures with quantum wells of various widths in pulsed magnetic fields up to 45 T are investigated. Our experimental cyclotron energies are in satisfactory agreement with the results of theoretical calculations performed using the eightband kp Hamiltonian. The shift of the cyclotron resonance (CR) line, which corresponds to the transition from the lowest Landau level to the low magneticfield region, is found upon varying the electron concentration due to the negative persistent photoconductivity effect. It is shown that the observed shift of the CR lines is associated with the finite width of the density of states at the Landau levels.

On EnergyMomentum Transfer of Quantum Fields
NASA Astrophysics Data System (ADS)
Herdegen, Andrzej
20141001
We prove the following theorem on bounded operators in quantum field theory: if , then , where D( x) is a function weakly decaying in spacelike directions, are creation/annihilation parts of an appropriate time derivative of B, G is any positive, bounded, nonincreasing function in , and is any finite complex Borel measure; creation/annihilation operators may be also replaced by with . We also use the notion of energymomentum scaling degree of B with respect to a submanifold (Steinmanntype, but in momentum space, and applied to the norm of an operator). These two tools are applied to the analysis of singularities of . We prove, among others, the following statement (modulo some more specific assumptions): outside p = 0 the only allowed contributions to this functional which are concentrated on a submanifold (including the trivial one—a single point) are Dirac measures on hypersurfaces (if the decay of D is not to slow).

Semianalytical quantum model for graphene fieldeffect transistors
SciTech Connect
Pugnaghi, Claudio; Grassi, Roberto Gnudi, Antonio; Di Lecce, Valerio; Gnani, Elena; Reggiani, Susanna; Baccarani, Giorgio
20140921
We develop a semianalytical model for monolayer graphene fieldeffect transistors in the ballistic limit. Two types of devices are considered: in the first device, the source and drain regions are doped by charge transfer with Schottky contacts, while, in the second device, the source and drain regions are doped electrostatically by a back gate. The model captures two important effects that influence the operation of both devices: (i) the finite density of states in the source and drain regions, which limits the number of states available for transport and can be responsible for negative output differential resistance effects, and (ii) quantum tunneling across the potential steps at the sourcechannel and drainchannel interfaces. By comparison with a selfconsistent nonequilibrium Green's function solver, we show that our model provides very accurate results for both types of devices, in the bias region of quasisaturation as well as in that of negative differential resistance.

Negativefrequency modes in quantum field theory
NASA Astrophysics Data System (ADS)
Dickinson, Robert; Forshaw, Jeff; Millington, Peter
20150701
We consider a departure from standard quantum field theory, constructed so as to permit momentum eigenstates of both positive and negative energy. The resulting theory is intriguing because it brings about the cancellation of leading ultraviolet divergences and the absence of a zeropoint energy. The theory gives rise to treelevel sourcetosource transition amplitudes that are manifestly causal and consistent with standard Smatrix elements. It also leads to the usual result for the oblique corrections to the standard electroweak theory. Remarkably, the latter agreement relies on the breakdown of naive perturbation theory due to resonance effects. It remains to be shown that there are no problems with perturbative unitarity.

Quantum field theory of van der Waals friction
SciTech Connect
Volokitin, A. I.; Persson, B. N. J.
20061115
van der Waals friction between two semiinfinite solids, and between a small neutral particle and semiinfinite solid is studied using thermal quantum field theory in the Matsubara formulation. We show that the friction to linear order in the sliding velocity can be obtained from the equilibrium Green functions and that our treatment can be extended for bodies with complex geometry. The calculated friction agrees with the friction obtained using a dynamical modification of the Lifshitz theory, which is based on the fluctuationdissipation theorem. We show that it should be possible to measure the van der Waals friction in noncontact friction experiment using stateoftheart equipment.

Matterenhanced transition probabilities in quantum field theory
SciTech Connect
Ishikawa, Kenzo Tobita, Yutaka
20140515
The relativistic quantum field theory is the unique theory that combines the relativity and quantum theory and is invariant under the Poincaré transformation. The ground state, vacuum, is singlet and one particle states are transformed as elements of irreducible representation of the group. The covariant one particles are momentum eigenstates expressed by plane waves and extended in space. Although the Smatrix defined with initial and final states of these states hold the symmetries and are applied to isolated states, outgoing states for the amplitude of the event that they are detected at a finitetime interval T in experiments are expressed by microscopic states that they interact with, and are surrounded by matters in detectors and are not plane waves. These matterinduced effects modify the probabilities observed in realistic situations. The transition amplitudes and probabilities of the events are studied with the Smatrix, S[T], that satisfies the boundary condition at T. Using S[T], the finitesize corrections of the form of 1/T are found. The corrections to Fermi’s golden rule become larger than the original values in some situations for light particles. They break Lorentz invariance even in high energy region of short de Broglie wave lengths.  Highlights: •Smatrix S[T] for the finitetime interval in relativistic field theory. •S[T] satisfies the boundary condition and gives correction of 1/T . •The large corrections for light particles breaks Lorentz invariance. •The corrections have implications to neutrino experiments.

Interlayer frictional drag in double quantum wells in perpendicular magnetic fields
NASA Astrophysics Data System (ADS)
Feng, Xiang Guang
Friction drag between isolated twodimensional electron gas (2DEG) layers is a relatively new experimental probe for the study of the interlayer interactions of twodimensional electron systems. By measuring drag as a function of various experimental parameters we can explore details of the electronelectron interactions and gain insight into the electronic states. As many new and interesting phenomena have been discovered for twodimensional electron gas systems in magnetic fields, beginning with the discovery of the quantum Halleffect, we were motivated to measure drag in magnetic fields perpendicular to the 2DEG. In our drag experiment in magnetic fields, we observed two unusual phenomena. First in intermediate field range, where the Landau level splitting is smaller than the thermal energy kT, we observed an unusual increase in drag in intermediate fields, which cannot be explained by current theory based on single particle scattering. We think the cause of this unusual increase is related to interlayer correlation induced by magnetic field. Secondly, in strong magnetic fields and unmatched layer densities, we observed negative drag peaks at certain field values, which have opposite polarity to the drag of electronelectron system at zero field. We argue that the negative drag reveals unusual dispersion of the electronic states near the Landau level, in which electrons show holelike behavior. We hope our work can inspire more studies, both theoretically and experimentally, on the two dimensional electron systems in magnetic field. The experiments discussed here were performed in Dr. Gramila's research group in the department of physics of Pennsylvania State University.

Notes on Translational and Rotational Properties of Tensor Fields in Relativistic Quantum Mechanics
NASA Astrophysics Data System (ADS)
Dvoeglazov, V. V.
Recently, several discussions on the possible observability of 4vector fields have been published in literature. Furthermore, several authors recently claimed existence of the helicity=0 fundamental field. We reexamine the theory of antisymmetric tensor fields and 4vector potentials. We study the massless limits. In fact, a theoretical motivation for this venture is the old papers of Ogievetskiĭ and Polubarinov, Hayashi, and Kalb and Ramond. Ogievetskiĭ and Polubarinov proposed the concept of the notoph, whose helicity properties are complementary to those of the photon. We analyze the quantum field theory with taking into account mass dimensions of the notoph and the photon. It appears to be possible to describe both photon and notoph degrees of freedom on the basis of the modified BargmannWigner formalism for the symmetric secondrank spinor. Next, we proceed to derive equations for the symmetric tensor of the second rank on the basis of the BargmannWigner formalism in a straightforward way. The symmetric multispinor of the fourth rank is used. Due to serious problems with the interpretation of the results obtained on using the standard procedure we generalize it and obtain the spin2 relativistic equations, which are consistent with the general relativity. Thus, in fact we deduced the gravitational field equations from relativistic quantum mechanics. The relations of this theory with the scalartensor theories of gravitation and f(R) are discussed. Particular attention has been paid to the correct definitions of the energymomentum tensor and other Nöther currents in the electromagnetic theory, the relativistic theory of gravitation, the general relativity, and their generalizations. We estimate possible interactions, fermionnotoph, gravitonnotoph, photonnotoph, and we conclude that they can probably be seen in experiments in the next few years.

Quantum corrections to the cosmological evolution of conformally coupled fields
SciTech Connect
Cembranos, Jose A.R.; Olive, Keith A.; Peloso, Marco; Uzan, JeanPhilippe Email: olive@physics.umn.edu Email: uzan@iap.fr
20090701
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 nonsingular 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.

Quantum field theories in spaces with neutral signatures
NASA Astrophysics Data System (ADS)
Pavšič, Matej
20130401
We point out that quantum field theories based on the concept of Clifford space and Clifford algebra valuedfields involve both positive and negative energies. This is a consequence of the indefinite signature (p, q) of the Clifford space. When the signature is neutral, p = q, then vacuum energy vanishes and there is no cosmological constant problem. A question of the stability of such theories in the presence of interactions arises. We investigate a toy model of the harmonic oscillator in the space M1,1. We have found that in the presence of certain interactions the amplitude of oscillations can remain finite. In general this is not the case and the amplitude grows to infinity, but only when the two frequencies are exactly the same. When they are even slightly different, the amplitude remains finite and the system is stable. We show how such oscillator comes from the Stueckelberg action in curved space, and how it can be generalized to field theories.

AAstacked bilayer graphene quantum dots in magnetic field
NASA Astrophysics Data System (ADS)
Belouad, Abdelhadi; Zahidi, Youness; Jellal, Ahmed
20160501
By applying the infinitemass boundary condition, we analytically calculate the confined states and the corresponding wave functions of AAstacked bilayer graphene (BLG) quantum dots (QDs) in the presence of an uniform magnetic field B. It is found that the energy spectrum shows two set of levels, which are the double copies of the energy spectrum for single layer graphene, shifted up–down by +γ and γ , respectively. However, the obtained spectrum exhibits different symmetries between the electron and hole states as well as the intervalley symmetries. It is noticed that, the applied magnetic field breaks all symmetries, except one related to the intervalley electron–hole symmetry, i.e. {E}{{e}}(τ ,m)={E}{{h}}(τ ,m). Two different regimes of confinement are found: the first one is due to the infinitemass barrier at weak B and the second is dominated by the magnetic field as long as B is large. We numerically investigated the basics features of the energy spectrum to show the main similarities and differences with respect to monolayer graphene, ABstacked BLG and semiconductor QDs. Dedicated to Professor Dr Hachim A Yamani on the occasion of his 70th birthday.

Bond breaking with auxiliaryfield quantum Monte Carlo.
PubMed
AlSaidi, W A; Zhang, Shiwei; Krakauer, Henry
20071014
Bond stretching mimics different levels of electron correlation and provides a challenging test bed for approximate manybody computational methods. Using the recently developed phaseless auxiliaryfield quantum Monte Carlo (AF QMC) method, we examine bond stretching in the wellstudied molecules BH and N(2) and in the H(50) chain. To control the sign/phase problem, the phaseless AF QMC method constrains the paths in the auxiliaryfield path integrals with an approximate phase condition that depends on a trial wave function. With single Slater determinants from unrestricted HartreeFock as trial wave function, the phaseless AF QMC method generally gives better overall accuracy and a more uniform behavior than the coupled cluster CCSD(T) method in mapping the potentialenergy curve. In both BH and N(2), we also study the use of multipledeterminant trial wave functions from multiconfiguration selfconsistentfield calculations. The increase in computational cost versus the gain in statistical and systematic accuracy are examined. With such trial wave functions, excellent results are obtained across the entire region between equilibrium and the dissociation limit. PMID:17935380

Auxiliaryfield quantum Monte Carlo calculations of the molybdenum dimer
NASA Astrophysics Data System (ADS)
Purwanto, Wirawan; Zhang, Shiwei; Krakauer, Henry
20160601
Chemical accuracy is difficult to achieve for systems with transition metal atoms. Third row transition metal atoms are particularly challenging due to strong electronelectron correlation in localized dorbitals. The Cr2 molecule is an outstanding example, which we previously treated with highly accurate auxiliaryfield quantum Monte Carlo (AFQMC) calculations [W. Purwanto et al., J. Chem. Phys. 142, 064302 (2015)]. Somewhat surprisingly, computational description of the isoelectronic Mo2 dimer has also, to date, been scattered and less than satisfactory. We present highlevel theoretical benchmarks of the Mo2 singlet ground state (X1Σg+) and first triplet excited state (a3Σu+), using the phaseless AFQMC calculations. Extrapolation to the complete basis set limit is performed. Excellent agreement with experimental spectroscopic constants is obtained. We also present a comparison of the correlation effects in Cr2 and Mo2.

Calculation of Zeeman splitting and Zeeman transition energies of spherical quantum dot in uniform magnetic field
NASA Astrophysics Data System (ADS)
Çakır, Bekir; Atav, Ülfet; Yakar, Yusuf; Özmen, Ayhan
20160801
In this study we report a detailed theoretical investigation of the effect of an external magnetic field on the 1s, 2p, 3d and 4fenergy states of a spherical quantum dot. We treat the contribution of the diamagnetic term as a perturbation and discuss the effect of the diamagnetic term on the 1s, 2p, 3d and 4fenergy states. We also have calculated the Zeeman transition energies between 2p → 1s and 3d → 2p states with m = 0, ±1 and 0, ±1, ±2 as a function of dot radius and the magnetic field strength. The results show that the magnetic field, impurity charge and dot radius have a strong influence on the energy states and the Zeeman transitions. It is found that the energies of the electronic states with m < 0 addition of the diamagnetic term firstly decrease toward a minimum, and then increase with the increasing magnetic field strength. We have seen that as magnetic field intensity is adjusted, frequency of the emitted light can be changed for Zeeman transitions.

Beyond the Plasma Analogy: Collective Field Theory for Quantum Hall States
NASA Astrophysics Data System (ADS)
Can, Tankut; Laskin, Michael; Wiegmann, Paul
We develop a quantum field theory of collective coordinates describing fractional quantum Hall (FQH) states. We show that the familiar properties of Laughlin states are captured by a Gaussian free field theory with a background charge. Gradient corrections to the Gaussian theory arise from ultraviolet regularization, and go beyond the celebrated plasma analogy. They give rise to a gravitational anomaly described by the Liouville theory of 2D quantum gravity. The field theory simplifies the computation of correlation functions in FQH states and makes manifest the effect of quantum anomalies. This talk is based on the preprint arXiv:1412.8716.

Control of the frozen geometric quantum correlation by applying the timedependent electromagnetic field
NASA Astrophysics Data System (ADS)
Wang, DongMei; Xu, JingBo; Yu, YouHong
20160401
We investigate how the timedependent electromagnetic field affects the sudden transitions of the geometric quantum correlation for two qubits each coupled to its own dissipative environment, and two qubits uniformly coupled to a common dissipative environment, respectively. It is shown that the sudden transitions of the geometric quantum correlation in both cases can be controlled by making use of timedependent electromagnetic field and, in addition, the frozen time during which the geometric quantum correlation remains constant can be lengthened.

A theoretical investigation of the sound radiation fields associated with a Bellmouth inlet
NASA Technical Reports Server (NTRS)
Meyer, W. L.; Zinn, B. T.
19830101
Analytical results are obtained by numerical integration of a cylindrically symmetric integral representation of the external solutions of the Helmholtz equation. The accuracy of this method is checked by comparisons of computed results with 'exact' solutions generated by the point source method. In all cases, the average error for the amplitude and phase of the points calculated in the field is found to be less than ten percent. Theoretical studies which model experiments run for the NASA Langely Bellmouth inlet configuration are presented and comparisons are made with the experimental results. In all cases very good agreement is obtained between the experimental and theoretically calculated values.

A theoretical investigation of the sound radiation fields associated with a Bellmouth inlet
NASA Astrophysics Data System (ADS)
Meyer, W. L.; Zinn, B. T.
19830401
Analytical results are obtained by numerical integration of a cylindrically symmetric integral representation of the external solutions of the Helmholtz equation. The accuracy of this method is checked by comparisons of computed results with 'exact' solutions generated by the point source method. In all cases, the average error for the amplitude and phase of the points calculated in the field is found to be less than ten percent. Theoretical studies which model experiments run for the NASA Langely Bellmouth inlet configuration are presented and comparisons are made with the experimental results. In all cases very good agreement is obtained between the experimental and theoretically calculated values.

States of maximum polarization for a quantum light field and states of a maximum sensitivity in quantum interferometry
NASA Astrophysics Data System (ADS)
Peřinová, Vlasta; Lukš, Antonín
20150601
The SU(2) group is used in two different fields of quantum optics, the quantum polarization and quantum interferometry. Quantum degrees of polarization may be based on distances of a polarization state from the set of unpolarized states. The maximum polarization is achieved in the case where the state is pure and then the distribution of the photonnumber sums is optimized. In quantum interferometry, the SU(2) intelligent states have also the property that the Fisher measure of information is equal to the inverse minimum detectable phase shift on the usual simplifying condition. Previously, the optimization of the Fisher information under a constraint was studied. Now, in the framework of constraint optimization, states similar to the SU(2) intelligent states are treated.

Evaporating quantum Lukewarm black holes final state from backreaction corrections of quantum scalar fields
NASA Astrophysics Data System (ADS)
Ghaffarnejad, H.; Neyad, H.; Mojahedi, M. A.
20130801
We obtain renormalized stress tensor of a massless, chargeless dynamical quantum scalar field, minimally coupled with a spherically symmetric static Lukewarm black hole. In two dimensional analog the minimal coupling reduces to the conformal coupling and the stress tensor is found to be determined by the nonlocal contribution of the anomalous trace and some additional parameters in close relation to the work presented by Christensen and Fulling. Lukewarm black holes are a special class of ReissnerNordströmde Sitter space times where its electric charge is equal to its mass. Having the obtained renormalized stress tensor we attempt to obtain a timeindependent solution of the well known metric back reaction equation. Mathematical derivations predict that the final state of an evaporating quantum Lukewarm black hole reduces to a remnant stable mini black hole with moved locations of the horizons. Namely the perturbed black hole (cosmological) horizon is compressed (extended) to scales which is smaller (larger) than the corresponding classical radius of the event horizons. Hence there is not obtained an deviation on the cosmic sensorship hypothesis.

On the Equivalence of Two Deformation Schemes in Quantum Field Theory
NASA Astrophysics Data System (ADS)
Lechner, Gandalf; Schlemmer, Jan; Tanimoto, Yoh
20130401
Two recent deformation schemes for quantum field theories on twodimensional Minkowski space, making use of deformed field operators and LongoWitten endomorphisms, respectively, are shown to be equivalent.

Elementary Theoretical Forms for the Spatial Power Spectrum of Earth's Crustal Magnetic Field
NASA Technical Reports Server (NTRS)
Voorhies, C.
19980101
The magnetic field produced by magnetization in Earth's crust and lithosphere can be distinguished from the field produced by electric currents in Earth's core because the spatial magnetic power spectrum of the crustal field differs from that of the core field. Theoretical forms for the spectrum of the crustal field are derived by treating each magnetic domain in the crust as the point source of a dipole field. The geologic nullhypothesis that such moments are uncorrelated is used to obtain the magnetic spectrum expected from a randomly magnetized, or unstructured, spherical crust of negligible thickness. This simplest spectral form is modified to allow for uniform crustal thickness, ellipsoidality, and the polarization of domains by an periodically reversing, geocentric axial dipole field from Earth's core. Such spectra are intended to describe the background crustal field. Magnetic anomalies due to correlated magnetization within coherent geologic structures may well be superimposed upon this background; yet representing each such anomaly with a single point dipole may lead to similar spectral forms. Results from attempts to fit these forms to observational spectra, determined via spherical harmonic analysis of MAGSAT data, are summarized in terms of amplitude, source depth, and misfit. Each theoretical spectrum reduces to a source factor multiplied by the usual exponential function of spherical harmonic degree n due to geometric attenuation with attitude above the source layer. The source factors always vary with n and are approximately proportional to n(exp 3) for degrees 12 through 120. The theoretical spectra are therefore not directly proportional to an exponential function of spherical harmonic degree n. There is no radius at which these spectra are flat, level, or otherwise independent of n.

Luminescence of double quantum wells subject to inplane magnetic fields
NASA Astrophysics Data System (ADS)
Orlita, M.; Grill, R.; Hlídek, P.; Zvára, M.; Döhler, G. H.; Malzer, S.; Byszewski, M.
20051001
We report on photoluminescence (PL) measurements of a symmetric GaAs/AlGaAs double quantum well (DQW) in high magnetic fields. For this study, a selectively contacted pδnDQWδnp structure was chosen, allowing an independent tuning of the electron density in the DQW and thus a creation of a twodimensional electron gas. Our attention was focused on phenomena in inplane magnetic fields, where the fieldinduced depopulation of the antibonding subband observable in the PL spectra as a socalled N type kink was predicted by Huang and Lyo (HL) [Phys. Rev. B 59, 7600 (1999)]. Whereas the equivalent behavior has been observed several times in the electric transport measurements and a proper theoretical description has been found, to the best of our knowledge, no PL experiment in a direct comparison with the theoretical model developed by HL has ever been published. We carried out a selfconsistent calculation based on their model and achieved a good agreement with our experimental results. Additionally, the influence of the excitonic interaction on the PL spectra, not taken into account by HL, is also discussed. This enables us to explain small deviations from the HL theory. The interpretation of the inplane magnetic field measurements is supported by the experiment with the magnetic field in the perpendicular orientation that allows a sufficiently accurate estimation of the electron density in the DQW. Distinctive renormalization effects of DQW subbands at various electron densities are also observed and discussed.

Effect of inplane magnetic field and applied strain in quantum spin Hall systems: Application to InAs/GaSb quantum wells
NASA Astrophysics Data System (ADS)
Hu, LunHui; Xu, DongHui; Zhang, FuChun; Zhou, Yi
20160801
Motivated by the recent discovery of quantized spin Hall effect in InAs/GaSb quantum wells [Du, Knez, Sullivan, and Du, Phys. Rev. Lett. 114, 096802 (2015), 10.1103/PhysRevLett.114.096802], we theoretically study the effects of inplane magnetic field and strain effect to the quantization of charge conductance by using LandauerB ütikker formalism. Our theory predicts a robustness of the conductance quantization against the inplane magnetic field up to a very high field of 20 T. We use a disordered hopping term to model the strain and show that the strain may help the quantization of the conductance. Relevance to the experiments will be discussed.

Higher orbital physics and artificial gauge fields with ultracold quantum gases
NASA Astrophysics Data System (ADS)
Sengstock, Klaus
20130301
Recently the physics of quantum gases in higher orbitals attracted a lot of attention, theoretically and experimentally. We report on studies of a new type of superfluid described by a complex order parameter, resulting from an interactioninduced hybridization of the two lowest orbitals for a binary spinmixture. As a main result we observe a quantum phase transition between the normal superfluid and this unconventional superfluid phase, where the local phase angle of the complex order parameter is continuously twisted between neighboring lattice sites. In addition we discuss new experimental work on the creation of artificial gauge potentials for neutral atoms in 1D and 2D lattices, which do not rely on the internal structure of the atoms. Via a timedependent driving of the optical lattice we have full control over amplitude and phase of the complex valued hopping parameters. In a 2D triangular lattice, we demonstrate the realization of gauge invariant staggered fluxes. Our system consists of an array of tubes filled with bosonic atoms having a welldefined local phase. The phase distribution obtained in presence of large amplitude staggered fluxes  where frustration plays a key role  obeys two fundamental symmetries, the discrete Ising symmetry (Z2) and a continuous global phase symmetry (U(1)). Via the full control of the staggered gauge fields, we are able to break the Ising symmetry on purpose which means lifting the degeneracy of the two possible Ising states, in analogy to a longitudinal homogenous magnetic field in the standard IsingSpin model. The measurements reveal ``textbook like'' magnetization curves with the well known dependence on both, the external magnetic field and the temperature. We observe a thermally driven phase transition from an ordered Ising (ferromagnetic) to an unordered (paramagnetic) state. Future directions to combine orbital physics and gauge fields will be discussed.

Dualities between semiclassical strings and quantum gauge field theories
NASA Astrophysics Data System (ADS)
Ouyang, Peter
In this thesis we study several examples of the correspondence between gauge field theories and string theories. A recurrent theme of these studies is that distinctively quantum mechanical behavior on the gauge theory side of the correspondence can have a classical or semiclassical description in terms of string calculations, as one might expect from general considerations of open/closed duality. We begin in Chapter 1 by reviewing the simplest duality, which relates Type IIB supergravity in AdS5 x S5 to N = 4 SU(N) gauge theory at large N. Working with this background spacetirne, we turn to a study of Dbrane probes with large quantum numbers in Chapter 2. We employ semiclassical methods to compute the excitation spectrum of these Dbranes, including corrections of order 1/N, which are related to loop effects in the dual field theory. In Chapter 3 we discuss the gauge/gravity duals with N = 1 supersymmetry which arise from placing Dbranes at a conifold singularity. The inclusion of fractional D3branes breaks conformal invariance, leading to a rich variety of phenomena in the gauge theory, among them chiral anomalies, a cascade of Seiberg dualities and confinement in the infrared. We pay particular attention to the chiral anomalies of the gauge theory and show that they can be described in terms of classical spontaneous symmetry breaking in the dual string theory. In accord with lowenergy confinement in the field theory, almost all of the moduli of the supergravity solution are fixed; we conclude Chapter 3 with some observations on the possibility of stabilizing the volume of the compact space in which the conifold is embedded. Finally, in Chapter 4 we study versions of the conifold theory with D7branes, which introduce fundamental matter into the gauge theory. By solving the classical supergravity equations of motion we identify a variant of the KlebanovStrassler duality cascade where the rate of the cascade decreases as the theory flows to low energies.

Opticalmodel potential in a relativistic quantum field model
NASA Astrophysics Data System (ADS)
Jaminon, M.; Mahaux, C.; Rochus, P.
19801101
The average nucleonnucleus potential at low and medium energy is investigated in the framework of a relativistic quantum field model. Using the same input parameters as Brockmann in his recent study of nuclear ground states, we calculate the selfconsistent relativistic Hartree potential at positive energy in the case of infinite nuclear matter and of 16O and 40Ca. This potential is the sum of a scalar operator and of the fourth component of a vector operator. We construct its Schrödingerequivalent potential by eliminating the small component of the Dirac spinor. The central part of this Schrödingerequivalent potential is in fair agreement with empirical values at low and intermediate energy. Particular attention is paid to the intermediate energy domain, in which the calculated potential is repulsive in the nuclear interior and attractive at the nuclear surface. This is in keeping with some empirical evidence and is similar to results found in the framework of the nonrelativistic BruecknerHartreeFock approximation. The spinorbit potential of the relativistic Hartree model is also in good agreement with empirical values. NUCLEAR REACTIONS Calculated average nuclear field of nuclear matter, 16O and 40Ca at positive energy from relativistic Hartree approximation.

P/NP, and the Quantum Field Computer
NASA Astrophysics Data System (ADS)
Freedman, Michael H.
19980101
The central problem is computer science is the conjecture that two complexity classes, P (polynomial time) and NP (nondeterministic polynomial timeroughly those decision problems for which a proposed solution can be checked in polynomial time), are distinct in the standard Turing model of computation: P neq NP. As a generality, we propose that each physical theory supports computational models whose power is limited by the physical theory. It is well known that classical physics supports a multitude of implementation of the Turning machine. NonAbelian topological quantum field theories exhibit the mathematical features necessary to support a model capable of solving all #P problems, a computationally intractable class, in polynomial time. Specifically, Witten [Witten, E. (1989) Commun. Math. Phys. 121, 351391] has identified expectation values in a certain SU(2)field theory with values of the Jones polynomial [Jones, V. (1985) Bull. Am. Math. Soc. 12, 103111] that are #Phard [Jaeger, F., Vertigen, D. & Welsh, D. (1990) Math. Proc. Comb. Philos. Soc. 108, 3553]. This suggests that some physical system whose effective Lagrangian contains a nonAbelian topological term might be manipulated to serve as an analog computer capable of solving NP or even #Phard problems in polynomial time. Defining such a system and addressing the accuracy issues inherent in preparation and measurement is a major unsolved problem.

Continuous variable methods in relativistic quantum information: characterization of quantum and classical correlations of scalar field modes in noninertial frames
NASA Astrophysics Data System (ADS)
Adesso, Gerardo; Ragy, Sammy; Girolami, Davide
20121101
We review a recently introduced unified approach to the analytical quantification of correlations in Gaussian states of bosonic scalar fields by means of Rényi2 entropy. This allows us to obtain handy formulae for classical, quantum, total correlations, as well as bipartite and multipartite entanglement. We apply our techniques to the study of correlations between two modes of a scalar field as described by observers in different states of motion. When one or both observers are in uniform acceleration, the quantum and classical correlations are degraded differently by the Unruh effect, depending on which mode is detected. Residual quantum correlations, in the form of quantum discord without entanglement, may survive in the limit of an infinitely accelerated observer Rob, provided they are revealed in a measurement performed by the inertial Alice.

Quantum Fields Obtained from Convoluted Generalized White Noise Never Have Positive Metric
NASA Astrophysics Data System (ADS)
Albeverio, Sergio; Gottschalk, Hanno
20160501
It is proven that the relativistic quantum fields obtained from analytic continuation of convoluted generalized (Lévy type) noise fields have positive metric, if and only if the noise is Gaussian. This follows as an easy observation from a criterion by Baumann, based on the Dell'AntonioRobinsonGreenberg theorem, for a relativistic quantum field in positive metric to be a free field.

Controlling the exciton energy of a nanowire quantum dot by strain fields
NASA Astrophysics Data System (ADS)
Chen, Yan; Zadeh, Iman Esmaeil; Jöns, Klaus D.; Fognini, Andreas; Reimer, Michael E.; Zhang, Jiaxiang; Dalacu, Dan; Poole, Philip J.; Ding, Fei; Zwiller, Val; Schmidt, Oliver G.
20160501
We present an experimental route to engineer the exciton energies of single quantum dots in nanowires. By integrating the nanowires onto a piezoelectric crystal, we controllably apply strain fields to the nanowire quantum dots. Consequently, the exciton energy of a single quantum dot in the nanowire is shifted by several meVs without degrading its optical intensity and singlephoton purity. Secondorder autocorrelation measurements are performed at different strain fields on the same nanowire quantum dot. The suppressed multiphoton events at zero time delay clearly verify that the quantum nature of singlephoton emission is well preserved under external strain fields. The work presented here could facilitate onchip optical quantum information processing with the nanowire based single photon emitters.

A multiplexed quantum memory.
PubMed
Lan, SY; Radnaev, A G; Collins, O A; Matsukevich, D N; Kennedy, T A; Kuzmich, A
20090801
A quantum repeater is a system for longdistance quantum communication that employs quantum memory elements to mitigate optical fiber transmission losses. The multiplexed quantum memory (O. A. Collins, S. D. Jenkins, A. Kuzmich, and T. A. B. Kennedy, Phys. Rev. Lett. 98, 060502 (2007)) has been shown theoretically to reduce quantum memory time requirements. We present an initial implementation of a multiplexed quantum memory element in a cold rubidium gas. We show that it is possible to create atomic excitations in arbitrary memory element pairs and demonstrate the violation of Bell's inequality for light fields generated during the write and read processes. PMID:19654771

Effects of Shannon entropy and electric field on polaron in RbCl triangular quantum dot
NASA Astrophysics Data System (ADS)
M, Tiotsop; A, J. Fotue; S, C. Kenfack; N, Issofa; H, Fotsin; L, C. Fai
20160401
In this paper, the time evolution of the quantum mechanical state of a polaron is examined using the Pekar type variational method on the condition of the electricLOphonon strongcoupling and polar angle in RbCl triangular quantum dot. We obtain the eigenenergies, and the eigenfunctions of the ground state, and the first excited state respectively. This system in a quantum dot can be treated as a twolevel quantum system qubit and the numerical calculations are performed. The effects of Shannon entropy and electric field on the polaron in the RbCl triangular quantum dot are also studied.

Fermionfermion scattering in quantum field theory with superconducting circuits.
PubMed
GarcíaÁlvarez, L; Casanova, J; Mezzacapo, A; Egusquiza, I L; Lamata, L; Romero, G; Solano, E
20150220
We propose an analogdigital quantum simulation of fermionfermion scattering mediated by a continuum of bosonic modes within a circuit quantum electrodynamics scenario. This quantum technology naturally provides strong coupling of superconducting qubits with a continuum of electromagnetic modes in an open transmission line. In this way, we propose qubits to efficiently simulate fermionic modes via digital techniques, while we consider the continuum complexity of an open transmission line to simulate the continuum complexity of bosonic modes in quantum field theories. Therefore, we believe that the complexitysimulatingcomplexity concept should become a leading paradigm in any effort towards scalable quantum simulations. PMID:25763944

Cardiovascular alterations in Macaca monkeys exposed to stationary magnetic fields: experimental observations and theoretical analysis
SciTech Connect
Tenforde, T.S.; Gaffey, C.T.; Moyer, B.R.; Budinger, T.F.
19830101
Simultaneous measurements were made of the electrocardiogram (ECG) and the intraarterial blood pressure of adult male Macaca monkeys during acute exposure to homogeneous stationary magnetic fields ranging in strength up to 1.5 tesla. An instantaneous, field strengthdependent increase in the ECG signal amplitude at the locus of the T wave was observed in fields greater than 0.1 tesla. The temporal sequence of this signal in the ECG record and its reversibility following termination of the magnetic field exposure are consistent with an earlier suggestion that it arises from a magnetically induced aortic blood flow potential superimposed on the native Twave signal. No measurable alterations in blood pressure resulted from exposure to fields up to 1.5 tesla. This experimental finding is in agreement with theoretical calculations of the magnetohydrodynamic effect on blood flow in the major arteries of the cardiovascular system. 27 references, 1 figure, 1 table.

Ballistic graphene nanoribbon metaloxidesemiconductor fieldeffect transistors: A full realspace quantum transport simulation
NASA Astrophysics Data System (ADS)
Liang, Gengchiau; Neophytou, Neophytos; Lundstrom, Mark S.; Nikonov, Dmitri E.
20070901
A realspace quantum transport simulator for graphene nanoribbon (GNR) metaloxidesemiconductor fieldeffect transistors (MOSFETs) has been developed and used to examine the ballistic performance of GNR MOSFETs. This study focuses on the impact of quantum effects on these devices and on the effect of different type of contacts. We found that twodimensional (2D) semiinfinite graphene contacts produce metalinducedgap states (MIGS) in the GNR channel. These states enhance quantum tunneling, particularly in short channel devices, they cause Fermi level pinning and degrade the device performance in both the ONstate and OFFstate. Devices with infinitely long contacts having the same width as the channel do not indicate MIGS. Even without MIGS quantum tunneling effects such as bandtoband tunneling still play an important role in the device characteristics and dominate the OFFstate current. This is accurately captured in our nonequilibrium Greens' function quantum simulations. We show that both narrow (1.4 nm width) and wider (1.8 nm width) GNRs with 12.5 nm channel length have the potential to outperform ultrascaled Si devices in terms of drive current capabilities and electrostatic control. Although their subthreshold swings under forward bias are better than in Si transistors, tunneling currents are important and prevent the achievement of the theoretical limit of 60 mV/dec.

Exchange interactions in CdMnTe/CdMgTe quantum wells under high magnetic fields
NASA Astrophysics Data System (ADS)
Yasuhira, T.; Uchida, K.; Matsuda, Y. H.; Miura, N.; Kuroda, S.; Takita, K.
20020301
The spd exchange interaction Jspd and the exchange interaction between the nearest neighbor Mn ions JNN were studied by magnetophotoluminescence spectra of excitons in CdMnTe/CdMgTe quantum wells in pulsed high magnetic fields up to 45 T. The magnitude of Jspd estimated from the observed Zeeman splitting was found to decrease as the quantum well width was decreased. The decrease is partly due to the penetration of the electron and the hole wave functions into the nonmagnetic CdMgTe barrier layers, and partly due to the kdependence of the exchange interaction. It was found that the latter effect is much larger than theoretically predicted. The observed features are well explained by a model assuming the interface disorder within some thickness near the interface. In contrast to Jspd, the nearest neighbor interaction JNN estimated from the steps in the photoluminescence peak was found to be independent of the well width.

Theoretical modeling of the plasmaassisted catalytic growth and field emission properties of graphene sheet
SciTech Connect
Sharma, Suresh C.; Gupta, Neha
20151215
A theoretical modeling for the catalystassisted growth of graphene sheet in the presence of plasma has been investigated. It is observed that the plasma parameters can strongly affect the growth and field emission properties of graphene sheet. The model developed accounts for the charging rate of the graphene sheet; number density of electrons, ions, and neutral atoms; various elementary processes on the surface of the catalyst nanoparticle; surface diffusion and accretion of ions; and formation of carbonclusters and large graphene islands. In our investigation, it is found that the thickness of the graphene sheet decreases with the plasma parameters, number density of hydrogen ions and RF power, and consequently, the field emission of electrons from the graphene sheet surface increases. The time evolution of the height of graphene sheet with ion density and sticking coefficient of carbon species has also been examined. Some of our theoretical results are in compliance with the experimental observations.

Classical and quantum Big Brake cosmology for scalar field and tachyonic models
SciTech Connect
Kamenshchik, A. Yu.; Manti, S.
20130221
We study a relation between the cosmological singularities in classical and quantum theory, comparing the classical and quantum dynamics in some models possessing the Big Brake singularity  the model based on a scalar field and two models based on a tachyonpseudotachyon field . It is shown that the effect of quantum avoidance is absent for the soft singularities of the Big Brake type while it is present for the Big Bang and Big Crunch singularities. Thus, there is some kind of a classical  quantum correspondence, because soft singularities are traversable in classical cosmology, while the strong Big Bang and Big Crunch singularities are not traversable.

Proposed Robust EntanglementBased Magnetic Field Sensor Beyond the Standard Quantum Limit
NASA Astrophysics Data System (ADS)
Tanaka, Tohru; Knott, Paul; Matsuzaki, Yuichiro; Dooley, Shane; Yamaguchi, Hiroshi; Munro, William J.; Saito, Shiro
20151001
Recently, there have been significant developments in entanglementbased quantum metrology. However, entanglement is fragile against experimental imperfections, and quantum sensing to beat the standard quantum limit in scaling has not yet been achieved in realistic systems. Here, we show that it is possible to overcome such restrictions so that one can sense a magnetic field with an accuracy beyond the standard quantum limit even under the effect of decoherence, by using a realistic entangled state that can be easily created even with current technology. Our scheme could pave the way for the realizations of practical entanglementbased magnetic field sensors.

Meanfield analysis of quantum annealing with XXtype terms
NASA Astrophysics Data System (ADS)
Nishimori, Hidetoshi
I analyze the role of XXtype terms in quantum annealing for a few meanfield systems including the Ising ferromagnet and the Hopfield model, both with manybody interactions. The XXtype terms are shown to be effective to remove firstorder quantum phase transitions, which exist in the conventional implementation of quantum annealing using only transverse fields. This means an exponential increase in efficiency, and is suggestive for the design of quantum annealers. I will discuss how and why this phenomenon emerges and what may happen on realistic finitedimensional lattices.

A new class of ensemble conserving algorithms for approximate quantum dynamics: Theoretical formulation and model problems
SciTech Connect
Smith, Kyle K. G.; Poulsen, Jens Aage Nyman, Gunnar; Rossky, Peter J.
20150628
We develop two classes of quasiclassical dynamics that are shown to conserve the initial quantum ensemble when used in combination with the FeynmanKleinert approximation of the density operator. These dynamics are used to improve the FeynmanKleinert implementation of the classical Wigner approximation for the evaluation of quantum time correlation functions known as FeynmanKleinert linearized pathintegral. As shown, both classes of dynamics are able to recover the exact classical and high temperature limits of the quantum time correlation function, while a subset is able to recover the exact harmonic limit. A comparison of the approximate quantum time correlation functions obtained from both classes of dynamics is made with the exact results for the challenging model problems of the quartic and doublewell potentials. It is found that these dynamics provide a great improvement over the classical Wigner approximation, in which purely classical dynamics are used. In a special case, our first method becomes identical to centroid molecular dynamics.

Concepts and their dynamics: a quantumtheoretic modeling of human thought.
PubMed
Aerts, Diederik; Gabora, Liane; Sozzo, Sandro
20131001
We analyze different aspects of our quantum modeling approach of human concepts and, more specifically, focus on the quantum effects of contextuality, interference, entanglement, and emergence, illustrating how each of them makes its appearance in specific situations of the dynamics of human concepts and their combinations. We point out the relation of our approach, which is based on an ontology of a concept as an entity in a state changing under influence of a context, with the main traditional concept theories, that is, prototype theory, exemplar theory, and theory theory. We ponder about the question why quantum theory performs so well in its modeling of human concepts, and we shed light on this question by analyzing the role of complex amplitudes, showing how they allow to describe interference in the statistics of measurement outcomes, while in the traditional theories statistics of outcomes originates in classical probability weights, without the possibility of interference. The relevance of complex numbers, the appearance of entanglement, and the role of Fock space in explaining contextual emergence, all as unique features of the quantum modeling, are explicitly revealed in this article by analyzing human concepts and their dynamics. PMID:24039114

Derivation of the Rules of Quantum Mechanics from InformationTheoretic Axioms
NASA Astrophysics Data System (ADS)
Fivel, Daniel I.
20120201
Conventional quantum mechanics with a complex Hilbert space and the Born Rule is derived from five axioms describing experimentally observable properties of probability distributions for the outcome of measurements. Axioms I, II, III are common to quantum mechanics and hidden variable theories. Axiom IV recognizes a phenomenon, first noted by von Neumann (in Mathematical Foundations of Quantum Mechanics, Princeton University Press, Princeton, 1955) and independently by Turing (Teuscher and Hofstadter, Alan Turing: Life and Legacy of a Great Thinker, Springer, Berlin, 2004), in which the increase in entropy resulting from a measurement is reduced by a suitable intermediate measurement. This is shown to be impossible for local hidden variable theories. Axiom IV, together with the first three, almost suffice to deduce the conventional rules but allow some exotic, alternatives such as real or quaternionic quantum mechanics. Axiom V recognizes a property of the distribution of outcomes of random measurements on qubits which holds only in the complex Hilbert space model. It is then shown that the five axioms also imply the conventional rules for any finite dimension.

The Impact of Quantum Theoretical Models of Consciousness on the Study of Education.
ERIC Educational Resources Information Center
Andris, James F.
This paper abstracts and discusses the approaches of five educational theorists who have used quantum theory as a model for educational phenomena, sets forth and uses metatheoretical criteria to evaluate the work of these theorists, and states guidelines for further work in this domain. The paper abstracts and discusses the works of the following…

Quantum Field Theories on the Lattice : Concepts behind their Numerical Simulations
NASA Astrophysics Data System (ADS)
Bietenholz, Wolfgang
20110901
We review the basic ideas behind numerical simulations of quantum field theory, which lead to nonperturbative results in particle physics. We first sketch the functional integral formulation of quantum mechanics, its transition to Euclidean time and the link to statistical mechanics. Then we proceed to quantum field theory in the lattice regularization, and its applications to scalar fields, gauge fields and fermions. In particular we address the treatment of chiral symmetry. At last we describe the formulation of lattice QCD and comment on simulations and results.

Formation of current filaments and magnetic field generation in a quantum currentcarrying plasma
SciTech Connect
Niknam, A. R.; Taghadosi, M. R.; Majedi, S.; Khorashadizadeh, S. M.
20130915
The nonlinear dynamics of filamentation instability and magnetic field in a currentcarrying plasma is investigated in the presence of quantum effects using the quantum hydrodynamic model. A new nonlinear partial differential equation is obtained for the spatiotemporal evolution of the magnetic field in the diffusion regime. This equation is solved by applying the Adomian decomposition method, and then the profiles of magnetic field and electron density are plotted. It is shown that the saturation time of filamentation instability increases and, consequently, the instability growth rate and the magnetic field amplitude decrease in the presence of quantum effects.

Dynamical gap generation in graphene nanoribbons: An effective relativistic field theoretical model
SciTech Connect
Chaves, A. J.; Paula, W. de; Frederico, T.; Lima, G. D.; Cordeiro, C. E.; Delfino, A.
20110415
We show that the assumption of a nontrivial zero band gap for a graphene sheet within an effective relativistic field theoretical model description of interacting Dirac electrons on the surface of graphene describes the experimental band gap of graphene nanoribbons for a wide range of widths. The graphene band gap is dynamically generated, corresponding to a nontrivial gapless solution, found in the limit of an infinitely wide graphene ribbon. The nanoribbon band gap is determined by the experimental graphene work function.

Spinglass behavior of Sn0.9Fe3.1N: An experimental and quantumtheoretical study
NASA Astrophysics Data System (ADS)
Scholz, Tanja; Dronskowski, Richard
20160501
Based on comprehensive experimental and quantumtheoretical investigations, we identify Sn0.9Fe3.1N as a canonical spin glass and the first ternary iron nitride with a frustrated spin ground state. Sn0.9Fe3.1N is the end member of the solid solution SnxFe4xN (0 < x ≤ 0.9) derived from ferromagnetic γ'Fe4N. Within the solid solution, the gradual incorporation of tin is accompanied by a drastic weakening of the ferromagnetic interactions. To explore the dilution of the ferromagnetic coupling, the highly tinsubstituted Sn0.9Fe3.1N has been magnetically reinvestigated. DC magnetometry reveals diverging susceptibilities for FC and ZFC measurements at low temperatures and an unsaturated hysteretic loop even at high magnetic fields. The temperature dependence of the real component of the AC susceptibility at different frequencies proves the spinglass transition with the characteristic parameters Tg = 12.83(6) K, τ* = 1011.8(2) s, zv = 5.6(1) and ΔTm/(Tm ṡ Δlgω) = 0.015. The timedependent response of the magnetic spins to the external field has been studied by extracting the distribution function of relaxation times g(τ, T) up to Tg from the complex plane of AC susceptibilities. The weakening of the ferromagnetic coupling by substituting tin into γ'Fe4N is explained by the Stoner criterion on the basis of electronic structure calculations and a quantumtheoretical bonding analysis.

Investigation of the interfacial tension of complex coacervates using fieldtheoretic simulations
SciTech Connect
Kumar, Rajeev
20120101
Complex coacervation, a liquidliquid phase separation that occurs when two oppositely charged polyelectrolytes are mixed in a solution, has the potential to be exploited for many emerging applications including wet adhesives and drug delivery vehicles. The ultralow interfacial tension of coacervate systems against water is critical for such applications, and it would be advantageous if molecular models could be used to characterize how various system properties (e.g., salt concentration) affect the interfacial tension. In this article we use fieldtheoretic simulations to characterize the interfacial tension between a complex coacervate and its supernatant. After demonstrating that our model is free of ultraviolet divergences (calculated properties converge as the collocation grid is refined), we develop two methods for calculating the interfacial tension from fieldtheoretic simulations. One method relies on the mechanical interpretation of the interfacial tension as the interfacial pressure, and the second method estimates the change in free energy as the area between the two phases is changed. These are the first calculations of the interfacial tension from full field theoretic simulation of which we are aware, and both the magnitude and scaling behaviors of our calculated interfacial tension agree with recent experiments.

Comparison of experimental and theoretical reaction rail currents, rail voltages, and airgap fields for the linear induction motor research vehicle
NASA Technical Reports Server (NTRS)
Elliott, D. G.
19770101
Measurements of reaction rail currents, reaction rail voltages, and airgap magnetic fields in tests of the Linear Induction Motor Research Vehicle (LIMRV) were compared with theoretical calculations from the mesh/matrix theory. It was found that the rail currents and magnetic fields predicted by the theory are within 20 percent of the measured currents and fields at most motor locations in most of the runs, but differ by as much as a factor of two in some cases. The most consistent difference is a higher experimental than theoretical magnetic field near the entrance of the motor and a lower experimental than theoretical magnetic field near the exit. The observed differences between the theoretical and experimental magnetic fields and currents do not account for the differences of as much as 26 percent between the theoretical and experimental thrusts.

Fieldtheoretic model of inhomogeneous supramolecular polymer networks and gels
NASA Astrophysics Data System (ADS)
Mohan, Aruna; Elliot, Richard; Fredrickson, Glenn H.
20101101
We present a fieldtheoretic model of the gelation transition in inhomogeneous reversibly bonding systems and demonstrate that our model reproduces the classical FloryStockmayer theory of gelation in the homogeneous limit. As an illustration of our model in the context of inhomogeneous gelation, we analyze the meanfield behavior of an equilibrium system of reacting trifunctional units in a good solvent confined within a slit bounded by parallel, repulsive walls. Our results indicate higher conversions and, consequently, higher concentrations of gel following the gelation transition near the center of the slit relative to the edges.

Fieldtheoretic model of inhomogeneous supramolecular polymer networks and gels.
PubMed
Mohan, Aruna; Elliot, Richard; Fredrickson, Glenn H
20101101
We present a fieldtheoretic model of the gelation transition in inhomogeneous reversibly bonding systems and demonstrate that our model reproduces the classical FloryStockmayer theory of gelation in the homogeneous limit. As an illustration of our model in the context of inhomogeneous gelation, we analyze the meanfield behavior of an equilibrium system of reacting trifunctional units in a good solvent confined within a slit bounded by parallel, repulsive walls. Our results indicate higher conversions and, consequently, higher concentrations of gel following the gelation transition near the center of the slit relative to the edges. PMID:21054065

Electric field driven fractal growth in polymer electrolyte composites: Experimental evidence of theoretical simulations
NASA Astrophysics Data System (ADS)
Dawar, Anit; Chandra, Amita
20121101
The influence of electric field on the diffusion limited aggregation has been observed experimentally. The observation provides experimental confirmation of the theoretical model proposed by ZhiJie Tan et al. [Phys. Lett. A 268 (2000) 112]. Most strikingly, a transition from a disordered ramified pattern to an ordered pattern (chainlike growth) has been observed. The growth is governed by diffusion, convection and migration in an electric field which give rise to the different patterns. This Letter can also be considered as an experimental evidence of computer simulated fractal growth given by Huang and Hibbert [Physica A 233 (1996) 888].

A theoretical study for parallel electric field in nonlinear magnetosonic waves in threecomponent plasmas
NASA Astrophysics Data System (ADS)
Toida, Mieko
20160701
The electric field parallel to the magnetic field in nonlinear magnetosonic waves in three component plasmas (twoionspecies plasma and electronpositronion plasma) is theoretically studied based on a threefluid model. In a twoionspecies plasma, a magnetosonic mode has two branches, highfrequency mode and lowfrequency mode. The parallel electric field E ∥ and its integral along the magnetic field, F =  ∫ E ∥ d s , in the two modes propagating quasiperpendicular to the magnetic field are derived as functions of the wave amplitude ɛ and the density ratio and cyclotron frequency ratio of the two ion species. The theory shows that the magnitude of F in the highfrequencymode pulse is much greater than that in the lowfrequencymode pulse. Theoretical expressions for E ∥ and F in nonlinear magnetosonic pulses in an electronpositronion plasma are also obtained under the assumption that the wave amplitudes are in the range of ( m e / m i ) 1 / 2 < ɛ < 1 , where m e / m i is the electron to ion mass ratio.

Accurate experimental and theoretical comparisons between superconductorinsulatorsuperconductor mixers showing weak and strong quantum effects
NASA Technical Reports Server (NTRS)
Mcgrath, W. R.; Richards, P. L.; Face, D. W.; Prober, D. E.; Lloyd, F. L.
19880101
A systematic study of the gain and noise in superconductorinsulatorsuperconductor mixers employing Ta based, Nb based, and Pballoy based tunnel junctions was made. These junctions displayed both weak and strong quantum effects at a signal frequency of 33 GHz. The effects of energy gap sharpness and subgap current were investigated and are quantitatively related to mixer performance. Detailed comparisons are made of the mixing results with the predictions of a threeport model approximation to the Tucker theory. Mixer performance was measured with a novel test apparatus which is accurate enough to allow for the first quantitative tests of theoretical noise predictions. It is found that the threeport model of the Tucker theory underestimates the mixer noise temperature by a factor of about 2 for all of the mixers. In addition, predicted values of available mixer gain are in reasonable agreement with experiment when quantum effects are weak. However, as quantum effects become strong, the predicted available gain diverges to infinity, which is in sharp contrast to the experimental results. Predictions of coupled gain do not always show such divergences.

An Interacting Gauge Field Theoretic Model for Hodge Theory: Basic Canonical Brackets
NASA Astrophysics Data System (ADS)
R., Kumar; Gupta, S.; R. P., Malik
20140601
We derive the basic canonical brackets amongst the creation and annihilation operators for a two (1 + 1)dimensional (2D) gauge held theoretic model of an interacting Hodge theory where a U(1) gauge field (Aμ) is coupled with the fermionic Dirac fields (ψ and bar psi). In this derivation, we exploit the spinstatistics theorem, normal ordering and the strength of the underlying six infinitesimal continuous symmetries (and the concept of their generators) that are present in the theory. We do not use the definition of the canonical conjugate momenta (corresponding to the basic fields of the theory) anywhere in our whole discussion. Thus, we conjecture that our present approach provides an alternative to the canonical method of quantization for a class of gauge field theories that are physical examples of Hodge theory where the continuous symmetries (and corresponding generators) provide the physical realizations of the de Rham cohomological operators of differential geometry at the algebraic level.

Dynamic Charge Carrier Trapping in Quantum Dot Field Effect Transistors.
PubMed
Zhang, Yingjie; Chen, Qian; Alivisatos, A Paul; Salmeron, Miquel
20150701
Noncrystalline semiconductor materials often exhibit hysteresis in charge transport measurements whose mechanism is largely unknown. Here we study the dynamics of charge injection and transport in PbS quantum dot (QD) monolayers in a field effect transistor (FET). Using Kelvin probe force microscopy, we measured the temporal response of the QDs as the channel material in a FET following step function changes of gate bias. The measurements reveal an exponential decay of mobile carrier density with time constants of 35 s for holes and ∼10 s for electrons. An Ohmic behavior, with uniform carrier density, was observed along the channel during the injection and transport processes. These slow, uniform carrier trapping processes are reversible, with time constants that depend critically on the gas environment. We propose that the underlying mechanism is some reversible electrochemical process involving dissociation and diffusion of water and/or oxygen related species. These trapping processes are dynamically activated by the injected charges, in contrast with static electronic traps whose presence is independent of the charge state. Understanding and controlling these processes is important for improving the performance of electronic, optoelectronic, and memory devices based on disordered semiconductors. PMID:26099508

Electromagnetic Form Factors of Hadrons in Quantum Field Theories
SciTech Connect
Dominguez, C. A.
20081013
In this talk, recent results are presented of calculations of electromagnetic form factors of hadrons in the framework of two quantum field theories (QFT), (a) DualLarge N{sub c} QCD (DualQCD{sub {infinity}}) for the pion, proton, and {delta}(1236), and (b) the KrollLeeZumino (KLZ) fully renormalizable Abelian QFT for the pion form factor. Both theories provide a QFT platform to improve on naive (treelevel) Vector Meson Dominance (VMD). DualQCD{sub {infinity}} provides a treelevel improvement by incorporating an infinite number of zerowidth resonances, which can be subsequently shifted from the real axis to account for the timelike behaviour of the form factors. The renormalizable KLZ model provides a QFT improvement of VMD in the framework of perturbation theory. Due to the relative mildness of the {rho}{pi}{pi} coupling, and the size of loop suppression factors, the perturbative expansion is well defined in spite of this being a strong coupling theory. Both approaches lead to considerable improvements of VMD predictions for electromagnetic form factors, in excellent agreement with data.

Spin operator and entanglement in quantum field theory
NASA Astrophysics Data System (ADS)
Fujikawa, Kazuo; Oh, C. H.; Zhang, Chengjie
20140701
Entanglement is studied in the framework of Dyson's Smatrix theory in relativistic quantum field theory, which leads to a natural definition of entangled states of a particleantiparticle pair and the spin operator from a Noether current. As an explicit example, the decay of a massive pseudoscalar particle into a pair of electron and positron is analyzed. Two spin operators are extracted from the Noether current. The Wigner spin operator characterizes spin states at the rest frame of each fermion and, although not measurable in the laboratory, gives rise to a straightforward generalization of lowenergy analysis of entanglement to the ultrarelativistic domain. In contrast, if one adopts a (modified) Dirac spin operator, the entanglement measured by spin correlation becomes maximal near the threshold of the decay, while the entanglement is replaced by the classical correlation for the ultrarelativistic electronpositron pair by analogy to the case of neutrinos, for which a hiddenvariables type of description is possible. Chiral symmetry differentiates the spin angular momentum and the magnetic moment. The use of weak interaction that can measure helicity is suggested in the analysis of entanglement at high energies instead of a SternGerlach apparatus, which is useless for the electron. A difference between the electron spin at high energies and the photon linear polarization is also noted. The Standard Model can describe all of the observable properties of leptons.

Quantum Chromodynamics  The Perfect YangMills Gauge Field Theory
NASA Astrophysics Data System (ADS)
Gross, David
David Gross: My talk today is about the most beautiful of all YangMills Theories (nonAbelian gauge theories), the theory of the strong nuclear interactions, Quantum Chromodynamics, QCD. We are celebrating 60 years of the publication of a remarkable paper which introduced the concept of nonAbelian local gauge symmetries, now called the YangMills theory, to physics. In the introduction to this paper it is noted that the usual principle of isotopic spin symmetry is not consistent with the concept of localized fields. This sentence has drawn attention over the years because the usual principle of isotopic spin symmetry is consistent, it is just not satisfactory. The authors, Yang and Mills, introduced a more satisfactory notion of local symmetry which did not require one to rotate (in isotopic spin space) the whole universe at once to achieve the symmetry transformation. Global symmetries are thus are similar to `action at a distance', whereas YangMills theory is manifestly local...

Transient quantum coherent response to a partially coherent radiation field
SciTech Connect
Sadeq, Zaheen S.; Brumer, Paul
20140221
The response of an arbitrary closed quantum system to a partially coherent electric field is investigated, with a focus on the transient coherences in the system. As a model we examine, both perturbatively and numerically, the coherences induced in a three level V system. Both rapid turnon and pulsed turnon effects are investigated. The effect of a long and incoherent pulse is also considered, demonstrating that during the pulse the system shows a coherent response which reduces after the pulse is over. Both the pulsed scenario and the thermally broadened CW case approach a mixed state in the long time limit, with rates dictated by the adjacent level spacings and the coherence time of the light, and via a mechanism that is distinctly different from traditional decoherence. These two excitation scenarios are also explored for a minimal “toy” model of the electronic levels in pigment protein complex PC645 by both a collisionally broadened CW laser and by a noisy pulse, where unexpectedly long transient coherence times are observed and explained. The significance of environmentally induced decoherence is noted.

Theoretical model of the electric field produced by charged particles in windblown sand flux
NASA Astrophysics Data System (ADS)
Zheng, Xiaojing; He, Lihong; Zhou, Youhe
20040801
Taking into account the coupled interactions among wind velocity, sand movement, and the electric field, we develop a general theoretical model for calculating the electric fields produced by charged sand particles in the three sand movement types, saltation, suspension and creep, quantifying the electric field of a point charge by Coulomb's law. The numerical results of the electric field are in good agreement with both the field data and the wind tunnel experimental results. The profile of the electric field intensity produced by charged particles in windblown sand flux is quantitatively analyzed in detail and compared with those generated by charged particles only in the saltation layer or in the creep layer. The results demonstrate that the profile of the electric field produced by charged particles in one sand movement type is different from that by those in other types and that the signs of the charge acquired by the particles also alter the features of the profile. Finally, the effects of the wind velocity and the charge of the windblown sand particles on the electric field intensity are discussed.

Ultrafast Modulation and Switching of QuantumWell Lasers using Terahertz Fields
NASA Technical Reports Server (NTRS)
Ning, CunZheng; Hughes, S.; Citrin, D.; Saini, Subhash (Technical Monitor)
19980101
Modulation and switching of semiconductor lasers are important for laserbased information technology. Typically the speed of modulation and switching is limited by interband processes such as stimulated and spontaneous recombinations which occur on a nanosecond time scale. This is why the diode laser modulation has been restricted to tens of GHz. Modulation at higher speed is highly desirable as the information technology enters into the socalled teraera. In this paper, we study the possibility of utilizing THzfieldinduced plasma heating to modulate quantumwell lasers. This is a timely study since, with the advancement of THz solidstate sources and freeelectron lasers, THz physics and related technology is currently coming out of its infancy. The investigation of interplaying THz and optical fields is also of intruiging fundamental interest. First, we introduce theoretical plasma heating results for the quantumwell optical amplifier in the presense of an intense halfcycle THz pulse. The heated carrier distributions are then utilized to calculate the THzpulseinduced change in refractive index and gain profile. Since the electronholeplasma is heated using intraband transitions, we circumvent the usual complications due to an overall change in density, and the nonlinear recovery is governed solely by the carrierLOphonon interactions, typically 5 ps for a complete recovery. This procedure implies THz and subTHz switching and recovery rates, respectively; using either gain modulation or index modulation. Plasma heating via steadystate THz fields is also studied. Finally, numerical simulation of a coupled set of equations to investigate the THz modulation based on a simplified model for quantumwell lasers is presented. Our results show that a semiconductor laser can be modulated at up to 1 THz with little distortion with a THz field amplitude at the order of a few kV/cm. Laser responses to a change in THz frequency will be shown. Constraints

Externalfield effect on quantum features of radiation emitted by a quantum well in a microcavity
SciTech Connect
Sete, Eyob A.; Das, Sumanta; Eleuch, H.
20110215
We consider a semiconductor quantum well in a microcavity driven by coherent light and coupled to a squeezed vacuum reservoir. By systematically solving the pertinent quantum Langevin equations in the strongcoupling and lowexcitation regimes, we study the effect of excitonphoton detuning, external coherent light, and the squeezed vacuum reservoir on vacuum Rabi splitting and on quantum statistical properties of the light emitted by the quantum well. We show that the excitonphoton detuning leads to a shift in polariton resonance frequencies and a decrease in fluorescence intensity. We also show that the fluorescent light exhibits quadrature squeezing, which predominately depends on the excitonphoton detuning and the degree of the squeezing of the input field.

Quantum field theory of gravity with spin and scaling gauge invariance and spacetime dynamics with quantum inflation
NASA Astrophysics Data System (ADS)
Wu, YueLiang
20160101
Treating the gravitational force on the same footing as the electroweak and strong forces, we present a quantum field theory of gravity based on spin and scaling gauge symmetries. A biframe spacetime is initiated to describe such a quantum gravity theory. The gravifield sided on both locally flat noncoordinate spacetime and globally flat Minkowski spacetime is an essential ingredient for gauging global spin and scaling symmetries. The locally flat gravifield spacetime spanned by the gravifield is associated with a noncommutative geometry characterized by a gaugetype field strength of the gravifield. A coordinateindependent and gaugeinvariant action for the quantum gravity is built in the gravifield basis. In the coordinate basis, we derive equations of motion for all quantum fields including the gravitational effect and obtain basic conservation laws for all symmetries. The equation of motion for the gravifield tensor is deduced in connection directly with the total energymomentum tensor. When the spin and scaling gauge symmetries are broken down to a background structure that possesses the global Lorentz and scaling symmetries, we obtain exact solutions by solving equations of motion for the background fields in a unitary basis. The massless graviton and massive spinon result as physical quantum degrees of freedom. The resulting Lorentzinvariant and conformally flat background gravifield spacetime is characterized by a cosmic vector with a nonzero cosmological mass scale. The evolving Universe is, in general, not isotropic in terms of conformal proper time. The conformal size of the Universe becomes singular at the cosmological horizon and turns out to be inflationary in light of cosmic proper time. A mechanism for quantum scalinon inflation is demonstrated such that it is the quantum effect that causes the breaking of global scaling symmetry and generates the inflation of the early Universe, which is ended when the evolving vacuum expectation value of the

Fieldwidened Michelson interferometer for spectral discrimination in highspectralresolution lidar: theoretical framework.
PubMed
Cheng, Zhongtao; Liu, Dong; Luo, Jing; Yang, Yongying; Zhou, Yudi; Zhang, Yupeng; Duan, Lulin; Su, Lin; Yang, Liming; Shen, Yibing; Wang, Kaiwei; Bai, Jian
20150501
A fieldwidened Michelson interferometer (FWMI) is developed to act as the spectral discriminator in highspectralresolution lidar (HSRL). This realization is motivated by the wideangle Michelson interferometer (WAMI) which has been used broadly in the atmospheric wind and temperature detection. This paper describes an independent theoretical framework about the application of the FWMI in HSRL for the first time. In the framework, the operation principles and application requirements of the FWMI are discussed in comparison with that of the WAMI. Theoretical foundations for designing this type of interferometer are introduced based on these comparisons. Moreover, a general performance estimation model for the FWMI is established, which can provide common guidelines for the performance budget and evaluation of the FWMI in the both design and operation stages. Examples incorporating many practical imperfections or conditions that may degrade the performance of the FWMI are given to illustrate the implementation of the modeling. This theoretical framework presents a complete and powerful tool for solving most of theoretical or engineering problems encountered in the FWMI application, including the designing, parameter calibration, prior performance budget, posterior performance estimation, and so on. It will be a valuable contribution to the lidar community to develop a new generation of HSRLs based on the FWMI spectroscopic filter. PMID:25969300

A theoretical study of soft mode behavior and ferroelectric phase transition in 18Oisotope exchanged SrTiO3: evidence of phase coexistence at the quantum critical point
NASA Astrophysics Data System (ADS)
Mkam Tchouobiap, S. E.
20140201
Motivated by recent experiments, the dynamics of the ferroelectric soft mode and the ferroelectric phase transition mechanism in 18O isotope exchanged systems SrTi(16O1x18Ox)3 (abbreviated as STO18x) are reinvestigated as a function of the 18O isotope exchange rate x, within a quasiharmonic model (QHM) for quantum ferroelectric modes in doubleMorse local potential with meanfield approximation interactions between modes. The approach was realized within the framework of the variational principle method at finite temperature through the quantum meanfield approximation and by taking into account the effect of isotope replacement through the predominant mass effect, the cell volume effect, homogeneity of the composition throughout the material and the concentrationdependent ferroelectric mode distortion effect. The dynamics of the lowestfrequency soft phonon mode clearly presents an increased softening phenomenon with increasing x and a complete one at the corresponding phase transition temperature Tc, demonstrating the perfect softmodetype quantum ferroelectric phase transition for x ⩾ xc. Also, a ferroelectricparaelectric phase coexistence state has been found near the quantum critical point xc and its origin is discussed. The ferroelectric phase transition mechanism is analyzed and its nature discussed, where a secondorder phase transition close to the tricritical point is predicted. In addition, the effect of quantum fluctuations on the soft mode dynamics is discussed which reveals its reduction with increasing x and the crossover of the soft mode dynamics from the quantum to the classic one at the full 18O exchange limit x = 1, for which the origin seems to lie in the new homogeneity associated with the direct reduction of quantum fluctuations effects on the soft mode behavior. Within the QHM, consistent agreement with some of the previous experimental results and theoretical predictions of quantum ferroelectricity throughout the full range of x are

Experimental and theoretical study on field emission properties of zinc oxide nanoparticles decorated carbon nanotubes
NASA Astrophysics Data System (ADS)
Li, Xin; Zhou, WeiMan; Liu, WeiHua; Wang, XiaoLi
20150501
Field emission properties of zinc oxide (ZnO) nanoparticles (NPs) decorated carbon nanotubes (CNTs) are investigated experimentally and theoretically. CNTs are in situ decorated with ZnO NPs during the growth process by chemical vapor deposition using a carbon source from the iron phthalocyanine pyrolysis. The experimental field emission test shows that the ZnO NP decoration significantly improves the emission current from 50 μA to 275 μA at 550 V and the reduced threshold voltage from 450 V to 350 V. The field emission mechanism of ZnO NPs on CNTs is theoretically studied by the density functional theory (DFT) combined with the PennPlummer method. The ZnO NPs reconstruct the ZnOCNT structure and pull down the surface barrier of the entire emitter system to 0.49 eV so as to reduce the threshold electric field. The simulation results suggest that the presence of ZnO NPs would increase the LDOS near the Fermi level and increase the emission current. The calculation results are consistent with the experiment results. Project supported by the National Natural Science Foundation of China (Grant Nos. 91123018, 61172040, and 61172041) and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2014JM7277).

Lead field theoretical approach in bioimpedance measurements: towards more controlled measurement sensitivity.
PubMed
Kauppinen, P K; Hyttinen, J A; Kööbi, T; Malmivuo, J
19990420
This study was conducted to demonstrate the potentiality of lead field theoretical approach in analyzing bioimpedance (BI) measurements. Anatomically accurate computer models and the lead field theory were used to develop BI measurement configurations capable of detecting more localized BI changes in the human body. The methods were applied to assess the measurement properties of conventional impedance cardiography (ICG) and such BI measurement configurations as can be derived using (i) the 12lead electrocardiography (ECG) and (ii) the international 1020 electroencephalography (EEG) electrode systems. Information as to how various electrode configurations are sensitive to detecting conductivity changes in different tissues and organs was thus obtained. Theoretical results with the 12lead system suggested that, compared to conventional ICGs, significantly more selective ICG configurations can be derived for cardiovascular structures. In addition to theoretical investigations, clinical test measurements were made with the 12lead system to establish whether characteristic waveforms are available. Sensitivity distributions obtained with the 1020 electrode system give promise of the possibility of monitoring noninvasively cerebrospinal fluid (CSF) impedance changes related to impending epileptic seizures. PMID:10372161

Ultrafast highfidelity initialization of a quantumdot spin qubit without magnetic fields
NASA Astrophysics Data System (ADS)
Mar, Jonathan D.; Baumberg, Jeremy J.; Xu, Xiulai; Irvine, Andrew C.; Williams, David A.
20141201
We demonstrate the initialization of a single quantumdot hole spin with high fidelity (lower bound >97 %), on picosecond time scales, and without the need for magnetic fields. Using the initialization scheme based on rapid electricfield ionization of a resonantly excited exciton, this is achieved by employing a selfassembled quantum dot with a low conductiontovalence band offset ratio, allowing control of the relative electron and hole tunneling rates over three orders of magnitude. This large difference in tunneling rates could permit spinstorage efficiencies >99.5 % by fastswitching to a low electricfield condition. Our results may provide a practical route towards ultrafast highfidelity initialization of individual quantumdot hole spins for the implementation of quantum error correction in a scalable spinbased quantum computer.

From classical mechanics with doubled degrees of freedom to quantum field theory for nonconservative systems
NASA Astrophysics Data System (ADS)
Kuwahara, Y.; Nakamura, Y.; Yamanaka, Y.
20131201
The 2×2matrix structure of Green's functions is a common feature for the realtime formalisms of quantum field theory under thermal situations, such as the closed time path formalism and Thermo Field Dynamics (TFD). It has been believed to originate from quantum nature. Recently, Galley has proposed the Hamilton's principle with initial data for nonconservative classical systems, doubling each degree of freedom [1]. We show that the Galley's Hamilton formalism can be extended to quantum field and that the resulting theory is naturally identical with nonequilibrium TFD.

Nearfield study of magnetooptical samples: theoretical comparison of transversal and polar effects
NASA Astrophysics Data System (ADS)
Van Labeke, Daniel; Vial, A.; Barchiesi, Dominique
19960901
The density of integration of magnetooptical devices is limited by diffraction of light. Recently some groups have proposed to use NearField Microscopy to overcome this limitation and some experiments have been performed both in transmission and reflection. In this paper we study theoretically magnetooptical effect in nearfield. We consider a magnetooptical sample with details smaller than the wavelength. This sample is modelled as a multilayer rough structure. At least one layer has magnetooptical properties. The corrugation at the interfaces are very small compared to the optical wavelength. We do not consider the writing problem and the experiment is only modelled in the reading mode. Moreover, the magnetic properties are considered in the saturation regime. For this study we use an extension of the method that we used to describe near field microscope with isotropic sample. The diffracted fields are determined in each layer by using a perturbative version of the Rayleigh method which leads to the resolution of a linear equation for each diffracted wave. The near field above the sample is thus obtained by summing all the diffracted waves. We consider two geometries for the magnetization: polar effect where the magnetization is perpendicular to the sample and transversal effect where it is in the plane. We compare nearfield images obtained in transmission and reflection by changing magnetization orientation. Comparisons with farfield results are also proposed.

Magnetic field dependence of a chargefrustrated state in a triangular triple quantum dot
NASA Astrophysics Data System (ADS)
Seo, M.; Chung, Y.
20131101
We studied the magnetic field dependence of a chargefrustrated state formed in a triangular triple quantum dot. Stability diagrams at various magnetic fields were measured by using twoterminal and threeterminal conductance measurement schemes. We found that the frustrated state broke down at an external magnetic field of around 0.1 T. This result is due to the confinement energy shifts in quantum dots under external magnetic fields. A similar breakdown of the frustrated state was observed when the confinement energy of a quantum dot was intentionally shifted by the plunger gate of the dot, which confirm the reason for the breakdown of the frustrated state under on applied magnetic field. Our measured stability diagrams differed depending on the measurement schemes, which could not be explained by the capacitive interaction model based on an independent particle picture. We believe that the discrepancy is related to the closed electron and hole trajectories inside a triple quantum dot.

Magnetoresistance and cyclotron mass in extremelycoupled double quantum wells under inplane magnetic fields
SciTech Connect
Blount, M.A.; Simmons, J.A.; Lyo, S.K.; Harff, N.E.; Weckwerth, M.V.
19971201
The authors experimentally investigate the transport properties of an extremelycoupled AlGaAs/GaAs double quantum well, subject to inplane magnetic fields (B{sub {parallel}}). The coupling of the double quantum well is sufficiently strong that the symmetricantisymmetric energy gap ({Delta}{sub SAS}) is larger than the Fermi energy (E{sub F}). Thus for all B{sub {parallel}} only the lower energy branch of the dispersion curve is occupied. In contrast to systems with weaker coupling such that {Delta}{sub SAS} < E{sub F} the authors find: (1) only a single feature, a maximum, in the inplane magnetoresistance, (2) a monotonic increase with B{sub {parallel}} in the cyclotron mass up to 2.2 times the bulk GaAs mass, and (3) an increasing Fermi surface orbit area with B{sub {parallel}}, in good agreement with theoretical predictions.

Finitetemperature scaling at the quantum critical point of the Ising chain in a transverse field
NASA Astrophysics Data System (ADS)
Haelg, Manuel; Huvonen, Dan; Guidi, Tatiana; QuinteroCastro, Diana Lucia; Boehm, Martin; Regnault, LouisPierre; Zheludev, Andrey
20150301
Inelastic neutron scattering is used to study the finitetemperature scaling behavior of spin correlations at the quantum critical point in an experimental realization of the onedimensional Ising model in a transverse field. The target compound is the wellcharacterized, anisotropic and bondalternating Heisenberg spin1 chain material NTENP. The validity and the limitations of the dynamic structure factor scaling are tested, discussed and compared to theoretical predictions. For this purpose neutron data have been collected on the threeaxes spectrometers IN14 at ILL and FLEXX at HZB as well as on the time of flight multichopper spectrometer LET at ISIS. In addition to the general statement about quantum criticality and universality, present study also reveals new insight into the properties of the spin chain compound NTENP in particular.

Fieldinduced periodic distortions in a nematic liquid crystal: deuterium NMR study and theoretical analysis.
PubMed
Sugimura, A; Zakharov, A V
20110801
The peculiarities in the dynamic of the director reorientation in a liquid crystal (LC) film under the influence of the electric E field directed at an angle α to the magnetic B field have been investigated both experimentally and theoretically. Timeresolved deuterium NMR spectroscopy is employed to investigate the fieldinduced director dynamics. Analysis of the experimental results, based on the predictions of hydrodynamic theory including both the director motion and fluid flow, provides an evidence for the appearance of the spatially periodic patterns in 4npentyl4'cyanobiphenyl LC film, at the angles α>60∘, in response to the suddenly applied E. These periodic distortions produce a lower effective rotational viscosity. This gives a faster response of the director rotation than for a uniform mode, as observed in our NMR experiment. PMID:21929001

Inferring electric fields and currents from ground magnetometer data  A test with theoretically derived inputs
NASA Technical Reports Server (NTRS)
Wolf, R. A.; Kamide, Y.
19830101
Advanced techniques considered by Kamide et al. (1981) seem to have the potential for providing observationbased high time resolution pictures of the global ionospheric current and electric field patterns for interesting events. However, a reliance on the proposed magnetograminversion schemes for the deduction of global ionospheric current and electric field patterns requires proof that reliable results are obtained. 'Theoretical' tests of the accuracy of the magnetogram inversion schemes have, therefore, been considered. The present investigation is concerned with a test, involving the developed KRM algorithm and the Rice Convection Model (RCM). The test was successful in the sense that there was overall agreement between electric fields and currents calculated by the RCM and KRM schemes.

Predicting excitonic gaps of semiconducting singlewalled carbon nanotubes from a field theoretic analysis
DOE PAGESBeta
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
20150217
We demonstrate that a nonperturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. Asmore » a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.« less

Predicting excitonic gaps of semiconducting singlewalled carbon nanotubes from a field theoretic analysis
NASA Astrophysics Data System (ADS)
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
20150201
We demonstrate that a nonperturbative framework for the treatment of the excitations of singlewalled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. We test this theory explicitly on the data reported by Dukovic et al. [Nano Lett. 5, 2314 (2005), 10.1021/nl0518122] and Sfeir et al. [Phys. Rev. B 82, 195424 (2010), 10.1103/PhysRevB.82.195424] and so demonstrate the method works over a wide range of reported excitonic spectra.

Predicting excitonic gaps of semiconducting singlewalled carbon nanotubes from a field theoretic analysis
SciTech Connect
Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.
20150217
We demonstrate that a nonperturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. As a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.

α∗cohomology, and classification of translationinvariant noncommutative quantum field theories
NASA Astrophysics Data System (ADS)
Varshovi, Amir Abbass
20140901
Translationinvariant ⋆ products are studied in the setting of α∗cohomology. It is explicitly shown that all quantum behaviors including Green's functions and the scattering matrix of translationinvariant noncommutative quantum field theories are thoroughly characterized by α∗cohomology classes of the star products.

On a derivation of the Boltzmann equation in Quantum Field Theory
NASA Astrophysics Data System (ADS)
Leiler, Gregor
The Boltzmann equation (BE) is a commonly used tool for the study of nonequilibrium many particle systems. It has been introduced in 1872 by Ludwig Boltzmann and has been widely generalized throughout the years. Today it is commonly used in physical applications, from the study of ordinary fluids to problems in particle Cosmology where Quantum Field Theoretical techniques are essential. Despite its numerous experimental successes, the conceptual basis of the BE is not entirely clear. For instance, it is well known that it is not a fundamental equation of physics like, say, the Heisenberg equation (HE). A natural question then arises whether it is possible to derive the BE from physical first principles, i.e. the Heisenberg equation in Quantum Field Theory. In this work we attempted to answer this question and succeeded in deriving the BE from the HE, thus further clarifying its conceptual status. In particular, the results we have obtained are as follows. Firstly, we establish the nonperturbative validity of what we call the "preBoltzmann equation". The crucial point here is that this latter equation is equivalent to the Heisenberg equation. Secondly, we proceed to consider various limits of the preBoltzmann equation, namly the "low density" and the "weak coupling" limits, to obtain two equations that can be considered as generalizations of the BE. These limits are always taken together with the "long time" limit, which allows us to interpret the BE as an appropriate long time limit of the HE. The generalization we obtain consists in additional "correction" terms to the usual Boltzmann collision factor, and can be associated to multiple particle scattering. Unlike the preBoltzmann equation, these latter results are only valid pertubatively. Finally, we briefly consider the possibility to extend these results beyond said limits and outline some important aspects in this case.

Theoretical study on electromagnetically induced transparency in molecular aggregate models using quantum Liouville equation method
SciTech Connect
Minami, Takuya; Nakano, Masayoshi
20150122
Electromagnetically induced transparency (EIT), which is known as an efficient control method of optical absorption property, is investigated using the polarizability spectra and population dynamics obtained by solving the quantum Liouville equation. In order to clarify the intermolecular interaction effect on EIT, we examine several molecular aggregate models composed of threestate monomers with the dipoledipole coupling. On the basis of the present results, we discuss the applicability of EIT in molecular aggregate systems to a new type of optical switch.

Theoretical and experimental investigation of the nonlinear dynamical trends of passively modelocked quantum dot lasers
NASA Astrophysics Data System (ADS)
Raghunathan, Ravi
In recent years, passively modelocked quantum dot lasers have shown great promise as compact, efficient and reliable pulsed sources of light for a range of precision and high performance applications, such as high bitrate optical communications, diverse waveform generation, metrology, and clock distribution in highperformance computing (HPC) processors. For such applications, stable optical pulses with short picosecond pulse durations and multigigahertz repetition rates are required. In addition, a low pulsetopulse timing jitter is also necessary to prevent errors arising from the ambiguity between neighboring pulses. In order to optimize pulse quality in terms of optical characteristics such as pulse shape and pulse train behavior, as well as RF characteristics such as phase noise and timing jitter, understanding the nonlinear output dynamics of such devices is of critical importance, not only to get a sense of the regimes of operation where device output might be stable or unstable, but also to gain insight into the parameters that influence the output characteristics the most, and how they can be accessed and exploited to optimize design and performance for next generation applications. In this dissertation, theoretical and experimental studies have been combined to investigate the dynamical trends of twosection passively modelocked quantum dot lasers. On the theoretical side, a novel numerical modeling scheme is presented as a powerful and versatile framework to study the nonlinear dynamics specific to a device, with devicespecific parameters extracted over a range of operating conditions. The practical utility of this scheme is then demonstrated, first, in an analytical capability to interpret and explain dynamical trends observed in experiment, and subsequently, as a predictive tool to guide experiment to operate in a desired dynamical regime. Modeling results are compared to experimental findings where possible. Finally, optical feedback from an

Particle creation in BoseEinstein condensates: Theoretical formulation based on conserving gapless meanfield theory
SciTech Connect
Kurita, Yasunari; Kobayashi, Michikazu; Ishihara, Hideki; Tsubota, Makoto
20101115
We formulate particlecreation phenomena in BoseEinstein condensates in terms of conserving gapless meanfield theory for weakly interacting Bose gases. The particlecreation spectrum is calculated by rediagonalizing the Bogoliubovde Gennes (BdG) Hamiltonian in meanfield theory. The conservation implies that quasiparticle creation is accompanied by quantum back reaction to the condensates. Particle creation in this meanfield theory is found to be equivalent to that in quantum field theory (QFT) in curved spacetime. An expression is obtained for an effective metric affected by quantum back reaction. The formula for the particlecreation spectrum obtained in terms of QFT in curved spacetime is shown to be the same as that given by rediagonalizing the BdG Hamiltonian.

Superfluorescence from photoexcited semiconductor quantum wells: Magnetic field, temperature, and excitation power dependence
NASA Astrophysics Data System (ADS)
Cong, Kankan; Wang, Yongrui; Kim, JiHee; Noe, G. Timothy; McGill, Stephen A.; Belyanin, Alexey; Kono, Junichiro
20150601
Superfluorescence (SF) is a manybody process in which a macroscopic polarization spontaneously builds up from an initially incoherent ensemble of excited dipoles and then cooperatively decays, producing a delayed pulse of coherent radiation. SF arising from electronhole recombination has recently been observed in In0.2Ga0.8As /GaAs quantum wells [G. T. Noe et al., Nature Phys. 8, 219 (2012), 10.1038/nphys2207 and J.H. Kim et al., Sci. Rep. 3, 3283 (2013), 10.1038/srep03283], but its observability conditions have not been fully established. Here, by performing magnetic field (B ), temperature (T ), and pump power (P ) dependent studies of SF intensity, linewidth, and delay time through timeintegrated and timeresolved magnetophotoluminescence spectroscopy, we have mapped out the B T P region in which SF is observable. In general, SF can be observed only at sufficiently low temperatures, sufficiently high magnetic fields, and sufficiently high laser powers with characteristic threshold behavior. We provide theoretical insights into these behaviors based primarily on considerations on how the growth rate of macroscopic coherence depends on these parameters. These results provide fundamental new insight into electronhole SF, highlighting the importance of Coulomb interactions among photogenerated carriers as well as various scattering processes that are absent in SF phenomena in atomic and molecular systems.

Evolution of quantum field, particle content, and classicality in the three stage universe
NASA Astrophysics Data System (ADS)
Singh, Suprit; Modak, Sujoy Kumar; Padmanabhan, T.
20131201
We study the evolution of a quantum scalar field in a toy universe which has three stages of evolution, viz., (i) an early (inflationary) de Sitter phase (ii) radiationdominated phase and (iii) latetime (cosmological constant dominated) de Sitter phase. Using the Schrödinger picture, the scalar field equations are solved separately for the three stages and matched at the transition points. The boundary conditions are chosen so that field modes in the early de Sitter evolves from the BunchDavies vacuum state. We determine the (timedependent) particle content of this quantum state for the entire evolution of the universe and describe the various features both numerically and analytically. We also describe the quantum to classical transition in terms of a classicality parameter which tracks the particle creation and its effect on phase space correlation of the quantum field.

On estimating perturbative coefficients in quantum field theory and statistical physics
SciTech Connect
Samuel, M.A. 
19940501
The authors present a method for estimating perturbative coefficients in quantum field theory and Statistical Physics. They are able to obtain reliable errorbars for each estimate. The results, in all cases, are excellent.

Classical geometrical interpretation of ghost fields and anomalies in YangMills theory and quantum gravity
SciTech Connect
ThierryMieg, J.
19850514
The reinterpretation of the BRS equations of Quantum Field Theory as the Maurer Cartan equation of a classical principal fiber bundle leads to a simple gauge invariant classification of the anomalies in Yang Mills theory and gravity.

Theoretical Studies of the Structure and Dynamics of Quantum Liquid Clusters
NASA Astrophysics Data System (ADS)
McMahon, Michele Ann
Quantum clusters of He and Hz are systems displaying both quantum and finitesize properties. Using variational and diffusion Monte Carlo, we investigate the energetics and structures of a variety of pure and doped clusters. First, we present results for the ground states of He _7 and (H_2)_{N } (N = 6, 7, 13 and 33). Both helium and hydrogen clusters are highly nonclassical, but, because of the weaker HeHe binding, H_{N} is more delocalized than (H_2)_ {N}. The He clusters are generally structureless spheres with highest particle density near the center. Although still spherical, (H_2)_{N} clusters show some internal structure with residual fivefold symmetry. We next study the rotational states of He_7 and (H_2) _7. As the angular momentum increases, these clusters evolve from spherical to toroidal. By L = 2 for He_7 and L = 6 for (H_2) _7, the clusters become metastable with respect to loss of one particle. The addition of a strongly binding dopant molecule, such as SF_6, induces structuring of the He density into solvation shells about the impurity. We demonstrate that SF_6 is located near the cluster center in He_{39,40 }. We study trial function bias and DMC convergence, showing that the amount of Monte Carlo sampling needed to converge the impurity location is much greater than for He. This distinction may explain discrepancies found in the literature. Our study of Cl_2He _{N} (N = 1, 6 and 20), contrasts isotropic and anisotropic treatments as well as the L = 0 and L = 2 rotational states. The inclusion of anisotropy lowers energies because of the gamma = pi/2 minimum in the Cl_2 He potential. rm Cl_2H_6 has a ring of helium density, about the ClCl bond, that is largely unchanged from the L = 0 to the L = 2 state. For rm Cl_2He_{20}, the helium density surrounds the central Cl_2 molecule, and both the He and Cl_2 densities delocalize under rotation. Investigation of energy transfer from an excited impurity to an embedding cluster sheds light on the

Origin of the ZeroField Splitting in Mononuclear Octahedral Mn(IV) Complexes: A Combined Experimental and Theoretical Investigation.
PubMed
Zlatar, Matija; Gruden, Maja; Vassilyeva, Olga Yu; Buvaylo, Elena A; Ponomarev, A N; Zvyagin, S A; Wosnitza, J; Krzystek, J; GarciaFernandez, Pablo; Duboc, Carole
20160201
The aim of this work was to determine and understand the origin of the electronic properties of Mn(IV) complexes, especially the zerofield splitting (ZFS), through a combined experimental and theoretical investigation on five wellcharacterized mononuclear octahedral Mn(IV) compounds, with various coordination spheres (N6, N3O3, N2O4 in both trans (transN2O4) and cis configurations (cisN2O4) and O4S2). Highfrequency and field EPR (HFEPR) spectroscopy has been applied to determine the ZFS parameters of two of these compounds, MnL(transN2O4) and MnL(O4S2). While at Xband EPR, the axialcomponent of the ZFS tensor, D, was estimated to be +0.47 cm(1) for MnL(O4S2), and a Dvalue of +2.289(5) cm(1) was determined by HFEPR, which is the largest Dmagnitude ever measured for a Mn(IV) complex. A moderate D value of 0.997(6) cm(1) has been found for MnL(transN2O4). Quantum chemical calculations based on two theoretical frameworks (the Density Functional Theory based on a coupled perturbed approach (CPDFT) and the hybrid LigandField DFT (LFDFT)) have been performed to define appropriate methodologies to calculate the ZFS tensor for Mn(IV) centers, to predict the orientation of the magnetic axes with respect to the molecular ones, and to define and quantify the physical origin of the different contributions to the ZFS. Except in the case of MnL(transN2O4), the experimental and calculated D values are in good agreement, and the sign of D is well predicted, LFDFT being more satisfactory than CPDFT. The calculations performed on MnL(cisN2O4) are consistent with the orientation of the principal anisotropic axis determined by singlecrystal EPR, validating the calculated ZFS tensor orientation. The different contributions to D were analyzed demonstrating that the dd transitions mainly govern D in Mn(IV) ion. However, a deep analysis evidences that many factors enter into the game, explaining why no obvious magnetostructural correlations can be drawn in this

Theoretical investigation of intramolecular vibrational energy redistribution in HFCO and DFCO induced by an external field.
PubMed
Pasin, Gauthier; Iung, Christophe; Gatti, Fabien; Richter, Falk; Léonard, Céline; Meyer, HansDieter
20081014
The present paper is devoted to a full quantum mechanical study of the intramolecular vibrational energy redistribution in HFCO and DFCO. In contrast to our previous studies [Pasin et al., J. Chem. Phys. 124, 194304 (2006) and 126, 024302 (2007)], the dynamics is now performed in the presence of an external timedependent field. This more closely reflects the experimental conditions. A sixdimensional dipole surface is computed. The multiconfiguration timedependent Hartree method is exploited to propagate the corresponding sixdimensional wave packets. Special emphasis is placed on the excitation of the outofplane bending vibration and on the dissociation of the molecule. In the case of DFCO, we predict that it is possible to excite the outofplane bending mode of vibration and to drive the dissociation to DF+CO with only one laser pulse with a fixed frequency and without excitation of an electronic state. PMID:19045144

Theoretical investigation of the behavior of CuSe2O5 compound in high magnetic fields
NASA Astrophysics Data System (ADS)
Saghafi, Z.; Jahangiri, J.; Mahdavifar, S.; Hadipour, H.; Farjami Shayesteh, S.
20160101
Based on the analytical and numerical approaches, we investigate thermodynamic properties of CuSe2O5 compound at high magnetic fields which is a candidate for the strong intrachain interaction in quasi onedimensional (1D) quantum magnets. Magnetic behavior of the system can be described by the 1D spin1/2 XXZ model in the presence of the DzyaloshinskiiMoriya (DM) interaction. Under these circumstances, there is one quantum critical field in this compound. Below the quantum critical field the spin chain system is in the gapless Luttinger liquid (LL) regime, whereas above it one observes a crossover to the gapped saturation magnetic phase. Indications on the thermodynamic curves confirm the occurrence of such a phase transition. The main characteristics of the LL phase are gapless and spinspin correlation functions decay algebraic. The effects of zerotemperature quantum phase transition are observed even at rather high temperatures in comparison with the counterpart compounds. In addition, we calculate the Wilson ratio in the model. The Wilson ratio at a fixed temperature remains almost independent of the field in the LL region. In the vicinity of the quantum critical field, the Wilson ratio increases and exhibits anomalous enhancement.

The effects of control field detuning on the modulation instability in a threelevel quantum well system
NASA Astrophysics Data System (ADS)
Borgohain, Nitu; Konar, S.
20160601
The paper presents a theoretical study of the modulation instability of a continuous or quasicontinuous optical probe in a three level quantum well system under electromagnetically induced transparency. The modulation instability is affected by the control field detuning, as well as evenorder dispersion and by the strength of Kerr (thirdorder) and quintic (fifthorder) nonlinearities. The fourthorder dispersion reduces the bandwidth over which modulation instability occurs, whereas the quintic nonlinearity saturates the growth of the modulation instability. Detuning the control field from resonance can significantly reduce the growth of the modulation instability at both low and high power levels. At low powers, the system becomes stable against modulation instability for small detuning of the control field and at high powers modulation instability disappears for larger detuning.

Effect of a lateral electric field on an offcenter single dopant confined in a thin quantum disk
NASA Astrophysics Data System (ADS)
Dujardin, F.; Oukerroum, A.; Feddi, E.; Bosch Bailach, J.; MartínezPastor, J.; Zazi, M.
20120201
The effect of a lateral electric field on a donor impurity confined in a thin quantum disk is studied theoretically in the framework of mass approximation and using the Ritz variational approach. We show that the binding energy depends on several parameters: the dot size, the position of the donor impurity, the lateral field strength, and its orientation relative to the axis containing the impurity. When the impurity is located at one edge and the electric field is oriented in the opposite direction, the binding energy is considerably reinforced due to the simultaneous additive effects of coulombic potential and electrostatic force. The competition between these effects modifies considerably the probability densities and allows a better comprehension of the binding energy variations. This interesting behavior can contribute to an better understanding of the experimental optical response.

Controllable optical steady behavior from nonradiative coherence in GaAs quantum well driven by a single elliptically polarized field
NASA Astrophysics Data System (ADS)
Zhu, Zhonghu; Chen, AiXi; Bai, Yanfeng; Yang, WenXing; Lee, RayKuang
20140501
In this paper, we analyze theoretically the optical steady behavior in GaAs quantum well structure which interacts with a single elliptically polarized field (EPF) and a πpolarized probe field. Due to the existence of the robust nonradiative coherence, we demonstrate that the controllable optical steady behavior including multistability (OM) and optical bistability (OB) can be obtained. More interestingly, our numerical results also illustrate that tuning the phase difference between two components of polarized electric field of the EPF can realize the conversion between OB and OM. Our results illustrate the potential to utilize the optical phase for developing the new alloptical switching devices, as well as a guidance in the design for possible experimental implementations.

Protecting quantum coherence of twolevel atoms from vacuum fluctuations of electromagnetic field
NASA Astrophysics Data System (ADS)
Liu, Xiaobao; Tian, Zehua; Wang, Jieci; Jing, Jiliang
20160301
In the framework of open quantum systems, we study the dynamics of a static polarizable twolevel atom interacting with a bath of fluctuating vacuum electromagnetic field and explore under which conditions the coherence of the open quantum system is unaffected by the environment. For both a singlequbit and twoqubit systems, we find that the quantum coherence cannot be protected from noise when the atom interacts with a nonboundary electromagnetic field. However, with the presence of a boundary, the dynamical conditions for the insusceptible of quantum coherence are fulfilled only when the atom is close to the boundary and is transversely polarizable. Otherwise, the quantum coherence can only be protected in some degree in other polarizable direction.

Ramsey's method of separated oscillating fields and its application to gravitationally induced quantum phase shifts
SciTech Connect
Abele, H.; Jenke, T.; Leeb, H.; Schmiedmayer, J.
20100315
We propose to apply Ramsey's method of separated oscillating fields to the spectroscopy of the quantum states in the gravity potential above a horizontal mirror. This method allows a precise measurement of quantum mechanical phaseshifts of a Schroedinger wave packet bouncing off a hard surface in the gravitational field of the Earth. Measurements with ultracold neutrons will offer a sensitivity to Newton's law or hypothetical shortranged interactions, which is about 21 orders of magnitude below the energy scale of electromagnetism.

Quantum cluster algorithm for frustrated Ising models in a transverse field
NASA Astrophysics Data System (ADS)
Biswas, Sounak; Rakala, Geet; Damle, Kedar
20160601
Working within the stochastic series expansion framework, we introduce and characterize a plaquettebased quantum cluster algorithm for quantum Monte Carlo simulations of transverse field Ising models with frustrated Ising exchange interactions. As a demonstration of the capabilities of this algorithm, we show that a relatively small ferromagnetic nextnearestneighbor coupling drives the transverse field Ising antiferromagnet on the triangular lattice from an antiferromagnetic threesublattice ordered state at low temperature to a ferrimagnetic threesublattice ordered state.

Simulations of magnetic field gradients due to micromagnets on a triple quantum dot circuit
NASA Astrophysics Data System (ADS)
PoulinLamarre, G.; BureauOxton, C.; Kam, A.; Zawadzki, P.; Studenikin, S.; Aers, G.; PioroLadrière, M.; Sachrajda, A. S.
20131201
To quantify the effects of local magnetic fields on triple quantum dots, the Heisenberg Hamiltonian has been diagonalized for three electrons coupled via the exchange interaction. In particular, we have investigated different geometries of micromagnets located on top of the triple dot in order to optimize the field gradient characteristics. In this paper, we focus on two geometries which are candidates for an addressable EDSR triple quantum dot device.

Simulations of magnetic field gradients due to micromagnets on a triple quantum dot circuit
SciTech Connect
PoulinLamarre, G.; BureauOxton, C.; Kam, A.; Zawadzki, P.; Aers, G.; Studenikin, S.; PioroLadrière, M.; Sachrajda, A. S.
20131204
To quantify the effects of local magnetic fields on triple quantum dots, the Heisenberg Hamiltonian has been diagonalized for three electrons coupled via the exchange interaction. In particular, we have investigated different geometries of micromagnets located on top of the triple dot in order to optimize the field gradient characteristics. In this paper, we focus on two geometries which are candidates for an addressable EDSR triple quantum dot device.

Theoretical study of lightemission properties of amorphous silicon quantum dots
NASA Astrophysics Data System (ADS)
Nishio, Kengo; Kōga, Junichiro; Yamaguchi, Toshio; Yonezawa, Fumiko
20030501
In order to clarify the mechanism of the photoluminescence (PL) from amorphous silicon quantum dots (aSi QDs), we calculate, in the tightbinding scheme, the emission spectra and the radiative recombination rate P of the direct bandtoband recombination process. For aSi QDs smaller than 2.4 nm in diameter, our calculations beautifully reproduce the peak energy EPL of the experimental PL peak [N.M. Park et al., Phys. Rev. Lett. 86, 1355 (2001)]. Our analysis also show that (i) the emission energy can be tuned into the visible range of light from red to blue by controlling the sizes of aSi QDs, and that (ii) P calculated for aSi QDs is higher by two to three orders of magnitude than that for crystalline Si QDs. From these results, we assert that aSi QDs are promising candidates for visible, tunable, and highperformance lightemitting devices.

Theoretical studies of excitons in type II CdSe/CdTe quantum dots
NASA Astrophysics Data System (ADS)
Miloszewski, Jacek M.; Tomić, Stanko; Binks, David
20140601
We present a method for calculating exciton and biexciton energies in typeII colloidal quantum dots. Our methodology is based on an 8band k · p Hamiltonian of the zinc blend structure, which incorporates the effects of spinorbit interaction, strain between the core and the shell and piezoelectric potentials. Exciton states are found using the configuration interaction (CI) method that explicitly includes the effects of Coulomb interaction, as well as exchange and correlation between manyelectron configurations. We pay particular attention to accurate modelling of the electrostatic interaction between quasiparticles. The model includes surface polarization and selfpolarization effects due to the large difference in dielectric constants at the boundary of the QD.

A theoretical analysis of the optical absorption properties in onedimensional InAs/GaAs quantum dot superlattices
SciTech Connect
Kotani, Teruhisa; Birner, Stefan; Lugli, Paolo; Hamaguchi, Chihiro
20140414
We present theoretical investigations of miniband structures and optical properties of InAs/GaAs onedimensional quantum dot superlattices (1DQDSLs). The calculation is based on the multiband k·p theory, including the conduction and valence band mixing effects, the strain effect, and the piezoelectric effect; all three effects have periodic boundary conditions. We find that both the electronic and optical properties of the 1DQDSLs show unique states which are different from those of well known single quantum dots (QDs) or quantum wires. We predict that the optical absorption spectra of the 1DQDSLs strongly depend on the interdot spacing because of the interdot carrier coupling and changing strain states, which strongly influence the conduction and valence band potentials. The interminiband transitions form the absorption bands. Those absorption bands can be tuned from almost continuous (closely stacked QD case) to spikelike shape (almost isolated QD case) by changing the interdot spacing. The polarization of the lowest absorption peak for the 1DQDSLs changes from being parallel to the stacking direction to being perpendicular to the stacking direction as the interdot spacing increases. In the case of closely stacked QDs, inplane anisotropy, especially [110] and [11{sup ¯}0] directions also depend on the interdot spacing. Our findings and predictions will provide an additional degree of freedom for the design of QDbased optoelectronic devices.

Theoretical investigation of single dopant in core/shell nanocrystal in magnetic field
NASA Astrophysics Data System (ADS)
Talbi, A.; Feddi, E.; Oukerroum, A.; Assaid, E.; Dujardin, F.; Addou, M.
20150901
The control of single dopant or "solitary dopant" in semiconductors constitute a challenge to achieve new range of tunable optoelectronic devices. Knowing that the properties of doped monocrystals are very sensitive to different external perturbations, the aim of this study is to understand the effect of a magnetic field on the ground state energy of an offcenter ionized donor in a core/shell quantum dot (CSQD). The binding energies with and without an applied magnetic field are determined by the Ritz variational method taking into account the electronimpurity correlation in the trial wave function deduced from the secondorder perturbation. It has been found that the external magnetic field affects strongly the binding energy, and its effect varies as a function of the core radius and the shell thickness. We have shown the existence of a threshold ratio (a / b) crit which represents the limit between the tridimensional and the spherical surface confinement. In addition our analysis demonstrates the important influence of the position of ionized donor in the shell material.

Dynamics of Crowd Behaviors: From Complex Plane to Quantum Random Fields
NASA Astrophysics Data System (ADS)
Ivancevic, Vladimir G.; Reid, Darryn J.
20151101
The following sections are included: * Complex Plane Dynamics of Crowds and Groups * Introduction * ComplexValued Dynamics of Crowd and Group Behaviors * Kähler Geometry of Crowd and Group Dynamics * Computer Simulations of Crowds and Croups Dynamics * Braids of Agents' Behaviors in the Complex Plane * HilbertSpace Control of Crowds and Groups Dynamics * Quantum Random Fields: A Unique Framework for Simulation, Optimization, Control and Learning * Introduction * Adaptive Quantum Oscillator * Optimization and Learning on Banach and Hilbert Spaces * Appendix * ComplexValued Image Processing * Linear Integral Equations * RiemannLiouville Fractional Calculus * Rigorous Geometric Quantization * Supervised MachineLearning Methods * FirstOrder Logic and Quantum Random Fields

EnvironmentAssisted Speedup of the Field Evolution in Cavity Quantum Electrodynamics
SciTech Connect
Cimmarusti, A. D.; Yan, Z.; Patterson, B. D.; Corcos, L. P.; Orozco, L. A.; Deffner, S.
20150611
We measure the quantum speed of the state evolution of the field in a weaklydriven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a preferential coupling to a tunable environment: the atoms. By controlling the environment, i.e., changing the number of atoms coupled to the optical cavity mode, an environment assisted speedup is realized: the quantum speed of the state repopulation in the optical cavity increases with the coupling strength between the optical cavity mode and this nonMarkovian environment (the number of atoms).

Monotonic convergent quantum optimal control method with exact equality constraints on the optimized control fields
NASA Astrophysics Data System (ADS)
Shu, ChuanCun; Ho, TakSan; Rabitz, Herschel
20160501
We present a monotonic convergent quantum optimal control method that can be utilized to optimize the control field while exactly enforcing multiple equality constraints for steering quantum systems from an initial state towards desired quantum states. For illustration, special consideration is given to finding optimal control fields with (i) exact zero area and (ii) exact zero area along with constant pulse fluence. The method combined with these two types of constraints is successfully employed to maximize the statetostate transition probability in a model vibrating diatomic molecule.

Quantum aspects of a moving magnetic quadrupole moment interacting with an electric field
SciTech Connect
Fonseca, I. C.; Bakke, K.
20150615
The quantum dynamics of a moving particle with a magnetic quadrupole moment that interacts with electric and magnetic fields is introduced. By dealing with the interaction between an electric field and the magnetic quadrupole moment, it is shown that an analogue of the Coulomb potential can be generated and bound state solutions can be obtained. Besides, the influence of the Coulombtype potential on the harmonic oscillator is investigated, where bound state solutions to both repulsive and attractive Coulombtype potentials are achieved and the arising of a quantum effect characterized by the dependence of the harmonic oscillator frequency on the quantum numbers of the system is discussed.

EnvironmentAssisted Speedup of the Field Evolution in Cavity Quantum Electrodynamics.
PubMed
Cimmarusti, A D; Yan, Z; Patterson, B D; Corcos, L P; Orozco, L A; Deffner, S
20150612
We measure the quantum speed of the state evolution of the field in a weakly driven optical cavity QED system. To this end, the mode of the electromagnetic field is considered as a quantum system of interest with a preferential coupling to a tunable environment: the atoms. By controlling the environment, i.e., changing the number of atoms coupled to the optical cavity mode, an environmentassisted speedup is realized: the quantum speed of the state repopulation in the optical cavity increases with the coupling strength between the optical cavity mode and this nonMarkovian environment (the number of atoms). PMID:26196802

Effect of transverse electric field and temperature on light absorption in GaAs/AlGaAs tunnelcoupled quantum wells
SciTech Connect
Firsov, D. A.; Vorobjev, L. E.; Vinnichenko, M. Ya. Balagula, R. M.; Kulagina, M. M.; Vasil’iev, A. P.
20151115
The photoluminescence and intersubband absorption spectra are studied in GaAs/AlGaAs tunnel coupled quantum well structures. The peak positions in the photoluminescence and absorption spectra are consistent with the theoretically calculated energies of optical carrier transitions. The effect of a transverse electric field and temperature on intersubband light absorption is studied. It is caused by electron redistribution between the sizequantization levels and a variation in the energy spectrum of quantum wells. The variation in the refractive index in the energy region of observed intersubband transitions is estimated using Kramers–Kronig relations.

Recent Developments in Fully Fluctuating FieldTheoretic Simulations of Polymer Melts and Solutions.
PubMed
Delaney, Kris T; Fredrickson, Glenn H
20160811
We review the latest developments in computational methods for direct simulation of fully fluctuating field theories of polymeric assemblies. In this context, we describe a newly developed theoretical and computational framework for accurately computing fluctuationcorrected phase diagrams of mesostructured polymer systems and report the first such complete phase diagram for a diblock copolymer melt. The method is based on complex Langevin sampling of a UV regularized fieldtheoretic model, with Helmholtz free energies computed using thermodynamic integration. UV regularization ensures that the free energies do not have an arbitrary reference; they can be compared between incommensurate phases, permitting for the first time the computation of orderorder transitions with fluctuation corrections. We further demonstrate that computed free energies are accurate in the disordered phase by comparison to perturbation theory on the oneloop level. Importantly, we note that our method uses no uncontrolled approximations beyond the initial definition of a coarsegrained molecular model for the polymer melt or solution. The method can be applied straightforwardly to melts and solutions containing multiple species with diverse polymer architectures. PMID:27414265

Theoretical analysis of the microwavedrill nearfield localized heating effect
NASA Astrophysics Data System (ADS)
Jerby, E.; Aktushev, O.; Dikhtyar, V.
20050201
The microwavedrill principle [Jerby et al., Science 298, 587 (2002)] is based on a localized hotspot effect induced by a nearfield coaxial applicator. The microwave drill melts the nonmetallic material locally and penetrates mechanically into it to shape the hole. This paper presents a theoretical analysis of the thermalrunaway effect induced in front of the microwave drill. The model couples the Maxwell's and heat equations including the material's temperaturedependent properties. A finitedifference timedomain algorithm is applied in a twotimescale numerical model. The simulation is demonstrated for mullite, and benchmarked in simplified cases. The results show a temperature rise of ˜103K/s up to 1300K within a hot spot confined to a ˜4mm width (˜0.1 wavelength). The inputport response to this nearfield effect is modeled by equivalent timevarying lumpedcircuit elements. Besides the physical insight, this theoretical study provides computational tools for design and analysis of microwave drills and for their realtime monitoring and adaptive impedance matching.

Regulation of cellular function via electromagnetic field frequency and extracellular environment: A theoretical experimental approach
NASA Astrophysics Data System (ADS)
Taghian, Toloo; Sheikh, Abdul; Narmoneva, Daria; Kogan, Andrei
20150301
Application of external electric field (EF) as a nonpharmacological, noninvasive tool to control cell function is of great therapeutic interest. We developed a theoreticalexperimental approach to investigate the biophysical mechanisms of EF interaction with cells in electrodefree physiologicallyrelevant configuration. Our numerical results demonstrated that EF frequency is the major parameter to control cell response to EF. Nonoscillating or lowfrequency EF leads to charge accumulation on the cell surface membrane that may mediate membrane initiated cell responses. In contrast, highfrequency EF penetrates the cell membrane and reaches cell cytoplasm, where it may directly activate intracellular responses. The theoretical predictions were confirmed in our experimental studies of the effects of applied EF on vascular cell function. Results show that nonoscillating EF increases vascular endothelial growth factor (VEGF) expression while field polarity controls cell adhesion rate. Highfrequency, but not low frequency, EF provides differential regulation of cytoplasmic focal adhesion kinase and VEGF expression depending on the substrate, with increased expression in cells cultured on RGDrich synthetic hydrogels, and decreased expression for matrigel culture. The authors acknowledge the financial support from the NSF (DMR1206784 & DMR0804199 to AK); the NIH (1R21 DK07881401A1 to DN) and the University of Cincinnati (Interdisciplinary Faculty Research Support Grant to DN and AK).

Mirrorfield entanglement in a microscopic model for quantum optomechanics
NASA Astrophysics Data System (ADS)
Sinha, Kanupriya; Lin, ShihYuin; Hu, B. L.
20150801
We use a microscopic model, the mirroroscillatorfield (MOF) model proposed by C. R. Galley, R. O. Behunin, and B. L. Hu [Phys. Rev. A 87, 043832 (2013), 10.1103/PhysRevA.87.043832], to describe the quantum entanglement between a mirror's centerofmass (c.m.) motion and a field. In contrast with the conventional approach where the mirrorfield entanglement is understood as arising from the radiation pressure of an optical field inducing the motion of the mirror's c.m., the MOF model incorporates the dynamics of the internal degrees of freedom of the mirror that couple to the optical field directly. The major advantage in this approach is that it provides a selfconsistent treatment of the three pertinent subsystems (the mirror's c.m. motion, its internal degrees of freedom, and the field) including their backactions on each other, thereby giving a more accurate account of the quantum correlations between the individual subsystems. The optical and the mechanical properties of a mirror arising from its dynamical interaction with a quantum field are obtained without imposing any boundary conditions on the field additionally, as is done in the conventional way. As one of the new physical features that arise from this selfconsistent treatment of the coupled optics and mechanics behavior we observe a coherent transfer of quantum correlations from the field to the mirror via its internal degrees of freedom. We find the quantum entanglement between the optical field and the mirror's centerofmass motion upon coarsegraining over the internal degree of freedom. Further, we show that in certain parameter regimes the mirrorfield entanglement is enhanced when the field interacts resonantly with the mirror's internal degree of freedom, a result which highlights the importance of including the internal structure of the mirror in quantum optomechanical considerations.

Topics in brane world and quantum field theory
NASA Astrophysics Data System (ADS)
Corradini, Olindo
In the first part of the thesis we study various issues in the Brane World scenario with particular emphasis on gravity and the cosmological constant problem. First, we study localization of gravity on smooth domainwall solutions of gravity coupled to a scalar field. In this context we discuss how the aforementioned localization is affected by including higher curvature terms in the theory, pointing out among other things that, general combinations of such terms lead to delocalization of gravity with the only exception of the GaussBonnet combination (and its higher dimensional counterparts). We then find a solitonic 3brane solution in 6D bulk in the EinsteinHilbertGaussBonnet theory of gravity. Near to the brane the metric is that for a product of the 4D flat Minkowski space with a 2D wedge whose deficit angle is proportional to the brane tension. Consistency tests imposed on such backgrounds appear to require the localized matter on the brane to be conformal. We then move onto infinite volume extra dimension Brane World scenarios where we study gravity in a codimension2 model, generalizing the work of Dvali, Gabadadze and Porrati to tensionful branes. We point out that, in the presence of the bulk GaussBonnet combination, the EinsteinHilbert term is induced on the brane already at the classical level. Consistency tests are presented here as well. To conclude we discuss, using String Theory, an interesting class of largeN gauge theories which have vanishing energy density even though these theories are noncovariant and nonsupersymmetric. In the second part of the thesis we study a formulation of Quantum Mechanical Path Integrals in curved space. Such Path Integrals present superficial divergences which need to be regulated. We perform a threeloop calculation in mode regularization as a nontrivial check of the noncovariant counterterms required by such scheme. We discover that dimensional regularization can be successfully adopted to evaluate the

Quantum rings of nonuniform thickness in magnetic field
SciTech Connect
RodríguezPrada, F. A.; García, L. F.; Mikhailov, I. D.
20140515
We consider a model of cratershaped quantum dot in form of a thin layer whose thickness linearly increases with the distance from the axis. We show that oneparticle wave equation for the electron confined in such structure can be completely separated in the adiabatic limit when the quantum dot thickness is much smaller than its lateral dimension. Analytical solutions found for this model has been used as base functions for analysing the effect of nonhomogeneity on the electronic spectrum in the framework of the exact diagonalization method.

Exact scattering matrix of graphs in magnetic field and quantum noise
SciTech Connect
Caudrelier, Vincent; Mintchev, Mihail; Ragoucy, Eric
20140815
We consider arbitrary quantum wire networks modelled by finite, noncompact, connected quantum graphs in the presence of an external magnetic field. We find a general formula for the total scattering matrix of the network in terms of its local scattering properties and its metric structure. This is applied to a quantum ring with N external edges. Connecting the external edges of the ring to heat reservoirs, we study the quantum transport on the graph in ambient magnetic field. We consider two types of dynamics on the ring: the free Schrödinger and the free massless Dirac equations. For each case, a detailed study of the thermal noise is performed analytically. Interestingly enough, in presence of a magnetic field, the standard linear JohnsonNyquist law for the low temperature behaviour of the thermal noise becomes nonlinear. The precise regime of validity of this effect is discussed and a typical signature of the underlying dynamics is observed.

Quantum nondemolition measurement of parity and generation of parity eigenstates in optical fields
SciTech Connect
Gerry, Christopher C.; Benmoussa, A.; Campos, R. A.
20051115
The parity of photonic number states is known to be an important observable for quantized electromagnetic fields with applications to quantum information processing and to Heisenberglimited measurement of phase shifts in quantum interferometry performed with maximally entangled states and with twin number states. In this paper we describe an approach to the quantum nondemolition measurement of parity for quantized optical fields. The method proposed involves the use of a crossKerr interaction where we assume a large Kerr nonlinearity is available through the techniques of electromagnetically induced transparency. Our proposed method does not require the measurement of photon number but rather measures parity directly. The method not only allows for the quantum nondemolition measurement of parity but also allows for the von Neumann projection of parity eigenstates from an arbitrary field state. The generation and detection of higherorder parity eigenstates is also discussed. Losses from dissipation and the effects of detector efficiency are considered.

Quantum dissonance induced by a thermal field and its dynamics in dissipative systems
NASA Astrophysics Data System (ADS)
Man, Z. X.; Xia, Y. J.; An, N. B.
20111001
In this paper, we study quantum correlation in separable systems termed quantum dissonance [K. Modi, T. Paterek, W. Son, V. Vedral, M. Williamson, Phys. Rev. Lett. 104, 080501 (2010)]. Firstly, we study the emergence of quantum dissonance between two atoms prepared in uncorrelated states and coupled to a singlemode thermal field. We show that even for situations when the thermal field cannot entangle the two atoms, it can nevertheless induce quantum dissonance between them. Then, we investigate the dynamics including the transfer in both Markovian and nonMarkovian regimes of quantum dissonance due to dissipation modeled by two independent subsystems each of which consists of a leaky cavity containing a twolevel atom and surrounded by a reservoir. The two subsystems possess some amount of atomic quantum dissonance at the beginning but do not interact with each other by any means later on. We show that the quantum dissonance can be transferred among the composite subsystems, but the way it evolves and is transferred may be very different compared to that of entanglement. Finally, we present an efficient method to refrain the unwanted transfer of quantum dissonance from interested systems to reservoirs.

Experimental and Theoretical Electron Density Analysis of Copper Pyrazine Nitrate QuasiLowDimensional Quantum Magnets.
PubMed
Dos Santos, Leonardo H R; Lanza, Arianna; Barton, Alyssa M; Brambleby, Jamie; Blackmore, William J A; Goddard, Paul A; Xiao, Fan; Williams, Robert C; Lancaster, Tom; Pratt, Francis L; Blundell, Stephen J; Singleton, John; Manson, Jamie L; Macchi, Piero
20160224
The accurate electron density distribution and magnetic properties of two metalorganic polymeric magnets, the quasionedimensional (1D) Cu(pyz)(NO3)2 and the quasitwodimensional (2D) [Cu(pyz)2(NO3)]NO3·H2O, have been investigated by highresolution singlecrystal Xray diffraction and density functional theory calculations on the whole periodic systems and on selected fragments. Topological analyses, based on quantum theory of atoms in molecules, enabled the characterization of possible magnetic exchange pathways and the establishment of relationships between the electron (charge and spin) densities and the exchangecoupling constants. In both compounds, the experimentally observed antiferromagnetic coupling can be quantitatively explained by the CuCu superexchange pathway mediated by the pyrazine bridging ligands, via a σtype interaction. From topological analyses of experimental chargedensity data, we show for the first time that the pyrazine tilt angle does not play a role in determining the strength of the magnetic interaction. Taken in combination with molecular orbital analysis and spin density calculations, we find a synergistic relationship between spin delocalization and spin polarization mechanisms and that both determine the bulk magnetic behavior of these Cu(II)pyz coordination polymers. PMID:26811927

A theoretical investigation of the influence of gold nanosphere size on the decay and energy transfer rates and efficiencies of quantum emitters
NASA Astrophysics Data System (ADS)
Marocico, Cristian A.; Zhang, Xia; Bradley, A. Louise
20160101
We present in this contribution a comprehensive investigation of the effect of the size of gold nanospheres on the decay and energy transfer rates of quantum systems placed close to these nanospheres. These phenomena have been investigated before, theoretically and experimentally, but no comprehensive study of the influence of the nanoparticle size on important dependences of the decay and energy transfer rates, such as the dependence on the donoracceptor spectral overlap and the relative positions of the donor, acceptor, and nanoparticle, exists. As such, different accounts of the energy transfer mechanism have been presented in the literature. We perform an investigation of the energy transfer mechanisms between emitters and gold nanospheres and between donoracceptor pairs in the presence of the gold nanospheres using a Green's tensor formalism, experimentally verified in our lab. We find that the energy transfer rate to small nanospheres is greatly enhanced, leading to a strong quenching of the emission of the emitter. When the nanosphere size is increased, it acts as an antenna, increasing the emission of the emitter. We also investigate the emission wavelength and intrinsic quantum yield dependence of the energy transfer to the nanosphere. As evidenced from the literature, the energy transfer process between the quantum system and the nanosphere can have a complicated distance dependence, with a r6 regime, characteristic of the Förster energy transfer mechanism, but also exhibiting other distance dependences. In the case of a donoracceptor pair of quantum systems in the presence of a gold nanosphere, when the donor couples strongly to the nanosphere, acting as an enhanced dipole; the donoracceptor energy transfer rate then follows a Förster trend, with an increased Förster radius. The coupling of the acceptor to the nanosphere has a different distance dependence. The angular dependence of the energy transfer efficiency between donor and acceptor

Wick rotation for quantum field theories on degenerate Moyal space(time)
SciTech Connect
Grosse, Harald; Lechner, Gandalf; Ludwig, Thomas; Verch, Rainer
20130215
In this paper the connection between quantum field theories on flat noncommutative space(times) in Euclidean and Lorentzian signature is studied for the case that time is still commutative. By making use of the algebraic framework of quantum field theory and an analytic continuation of the symmetry groups which are compatible with the structure of Moyal space, a general correspondence between field theories on Euclidean space satisfying a time zero condition and quantum field theories on Moyal Minkowski space is presented ('Wick rotation'). It is then shown that field theories transferred to Moyal space(time) by Rieffel deformation and warped convolution fit into this framework, and that the processes of Wick rotation and deformation commute.

Conformal fields and the quantum state of the universe
NASA Astrophysics Data System (ADS)
Kamenshchik, Alexander Y.
20120201
The creation of a quantum Universe is described by a density matrix which yields an ensemble of universes with the cosmological constant limited to a bounded range Λmin <= Λ <= Λmax. The domain Λ < Λmin is ruled out by a cosmological bootstrap requirement (the selfconsistent back reaction of hot matter). The upper cutoff results from the quantum effects of vacuum energy and the conformal anomaly mediated by a special ghostavoidance renormalization. The cutoff Λmax establishes a new quantum scale  the accumulation point of an infinite sequence of garlandtype instantons. The cosmological evolution starting with these initial conditions also have some new features: the stage of cosmic acceleration can be followed by a big boost singularity  a rapid growth up to infinity of the scale factor acceleration parameter. A correspondence between the 4dimensional modified quantum Freidmann equations and the Friedmann equations arising in the context of 5dimensional classical cosmological models was established.

Finite temperature quantum field theory in the functional Schroedinger picture
SciTech Connect
Lee, H. ); Na, K.; Yee, J.H. )
19950315
We calculate the finite temperature Gaussian effective potential of scalar [phi][sup 4] theory in the functional Schroedinger picture. Our method is the direct generalization of the variational method proposed by Eboli, Jackiw, and Pi for quantummechanical systems, and gives the same result as that of AmelinoCamelia and Pi who used the selfconsistent composite operator method.

Theoretical prediction of hydrogenbond basicity pKBHX using quantum chemical topology descriptors.
PubMed
Green, Anthony J; Popelier, Paul L A
20140224
Hydrogen bonding plays an important role in the interaction of biological molecules and their local environment. Hydrogenbond strengths have been described in terms of basicities by several different scales. The pKBHX scale has been developed with the interests of medicinal chemists in mind. The scale uses equilibrium constants of acid···base complexes to describe basicity and is therefore linked to Gibbs free energy. Site specific data for polyfunctional bases are also available. The pKBHX scale applies to all hydrogenbond donors (HBDs) where the HBD functional group is either OH, NH, or NH+. It has been found that pKBHX can be described in terms of a descriptor defined by quantum chemical topology, ΔE(H), which is the change in atomic energy of the hydrogen atom upon complexation. Essentially the computed energy of the HBD hydrogen atom correlates with a set of 41 HBAs for five common HBDs, water (r2=0.96), methanol (r2=0.95), 4fluorophenol (r2=0.91), serine (r2=0.93), and methylamine (r2=0.97). The connection between experiment and computation was strengthened with the finding that there is no relationship between ΔE(H) and pKBHX when hydrogen fluoride was used as the HBD. Using the methanol model, pKBHX predictions were made for an external set of bases yielding r2=0.90. Furthermore, the basicities of polyfunctional bases correlate with ΔE(H), giving r2=0.93. This model is promising for the future of computation in fragmentbased drug design. Not only has a model been established that links computation to experiment, but the model may also be extrapolated to predict external experimental pKBHX values. PMID:24460383

A Theoretical Method for Characterizing Nonlinear Effects in Paul Traps with Added Octopole Field.
PubMed
Xiong, Caiqiao; Zhou, Xiaoyu; Zhang, Ning; Zhan, Lingpeng; Chen, Yongtai; Chen, Suming; Nie, Zongxiu
20150801
In comparison with numerical methods, theoretical characterizations of ion motion in the nonlinear Paul traps always suffer from low accuracy and little applicability. To overcome the difficulties, the theoretical harmonic balance (HB) method was developed, and was validated by the numerical fourthorder RungeKutta (4th RK) method. Using the HB method, analytical ion trajectory and ion motion frequency in the superimposed octopole field, ε, were obtained by solving the nonlinear Mathieu equation (NME). The obtained accuracy of the HB method was comparable with that of the 4th RK method at the Mathieu parameter, q = 0.6, and the applicable q values could be extended to the entire first stability region with satisfactory accuracy. Two sorts of nonlinear effects of ion motion were studied, including ion frequency shift, Δβ, and ion amplitude variation, Δ(C(2n)/C0) (n ≠ 0). New phenomena regarding Δβ were observed, although extensive studies have been performed based on the pseudopotential well (PW) model. For instance, the Δβ at ε = 0.1 and ε = 0.1 were found to be different, but they were the same in the PW model. This is the first time the nonlinear effects regarding Δ(C(2n)/C0) (n ≠ 0) are studied, and the associated study has been a challenge for both theoretical and numerical methods. The nonlinear effects of Δ(C(2n)/C0) (n ≠ 0) and Δβ were found to share some similarities at q < 0.6: both of them were proportional to ε, and the square of the initial ion displacement, z(0)(2). PMID:25924875

Linear and nonlinear optical properties in an asymmetric double quantum well under intense laser field: Effects of applied electric and magnetic fields
NASA Astrophysics Data System (ADS)
Yesilgul, U.; Al, E. B.; MartínezOrozco, J. C.; Restrepo, R. L.; MoraRamos, M. E.; Duque, C. A.; Ungan, F.; Kasapoglu, E.
20160801
In the present study, the effects of electric and magnetic fields on the linear and thirdorder nonlinear optical absorption coefficients and relative change of the refractive index in asymmetric GaAs/GaAlAs double quantum wells under intense laser fields are theoretically investigated. The electric field is oriented along the growth direction of the heterostructure while the magnetic field is taken inplane. The intense laser field is linear polarization along the growth direction. Our calculations are made using the effectivemass approximation and the compact densitymatrix approach. Intense laser effects on the system are investigated with the use of the Floquet method with the consequent change in the confinement potential of heterostructures. Our results show that the increase of the electric and magnetic fields blueshifts the peak positions of the total absorption coefficient and of the total refractive index while the increase of the intense laser field firstly blueshifts the peak positions and later results in their redshifting.

Instantaneous spatially local projective measurements are consistent in a relativistic quantum field
SciTech Connect
Lin, ShihYuin
20121215
Suppose the postulate of measurement in quantum mechanics can be extended to quantum field theory; then a local projective measurement at some moment on an object locally coupled with a relativistic quantum field will result in a projection or collapse of the wavefunctional of the combined system defined on the whole timeslice associated with the very moment of the measurement, if the relevant degrees of freedom have nonzero correlations. This implies that the wavefunctionals in the same Hamiltonian system but defined in different reference frames would collapse on different timeslices passing through the same local event where the measurement was done. Are these postmeasurement states consistent with each other? We illustrate that the quantum states of the RaineSciamaGrove detectorfield system started with the same initial Gaussian state defined on the same initial timeslice, then collapsed by the measurements on the pointlike detectors on different timeslices in different frames, will evolve to the same state of the combined system up to a coordinate transformation when compared on the same final timeslice. Such consistency is guaranteed by the spatial locality of interactions and the general covariance in a relativistic system, together with the spatial locality of measurements and the linearity of quantum dynamics in its quantum theory.  Highlights: BlackRightPointingPointer Spatially local quantum measurements in detectorfield models are studied. BlackRightPointingPointer Local quantum measurement collapses the wavefunctional on the whole timeslice. BlackRightPointingPointer In different frames wavefunctionals of a field would collapse on different timeslices. BlackRightPointingPointer States collapsed by the same measurement will be consistent on the same final slice.

Ordinary versus PTsymmetric Φ³ quantum field theory
SciTech Connect
Bender, Carl M.; Branchina, Vincenzo; Messina, Emanuele
20120402
A quantummechanical theory is PTsymmetric if it is described by a Hamiltonian that commutes with PT, where the operator P performs space reflection and the operator T performs time reversal. A PTsymmetric Hamiltonian often has a parametric region of unbroken PT symmetry in which the energy eigenvalues are all real. There may also be a region of broken PT symmetry in which some of the eigenvalues are complex. These regions are separated by a phase transition that has been repeatedly observed in laboratory experiments. This paper focuses on the properties of a PTsymmetric igΦ³ quantum field theory. This quantum field theory is the analog of the PTsymmetric quantummechanical theory described by the Hamiltonian H=p²+ix³, whose eigenvalues have been rigorously shown to be all real. This paper compares the renormalization group properties of a conventional Hermitian gΦ³ quantum field theory with those of the PTsymmetric igΦ³ quantum field theory. It is shown that while the conventional gΦ³ theory in d=6 dimensions is asymptotically free, the igΦ³ theory is like a gΦ⁴ theory in d=4 dimensions; it is energetically stable, perturbatively renormalizable, and trivial.

Theoretical study of electromagnetic electron cyclotron waves in the presence of AC field in Uranian magnetosphere
NASA Astrophysics Data System (ADS)
Pandey, R. S.; Kaur, Rajbir
20151001
Electromagnetic electron cyclotron (EMEC) waves with temperature anisotropy in the magnetosphere of Uranus have been studied in present work. EMEC waves are investigated using method of characteristic solution by kinetic approach, in presence of AC field. In 1986, Voyager 2 encounter with Uranus revealed that magnetosphere of Uranus exhibit nonMaxwellian highenergy tail distribution. So, the dispersion relation, real frequency and growth rate are evaluated using Lorentzian Kappa distribution function. Effect of temperature anisotropy, AC frequency and number density of particles is found. The study is also extended to oblique propagation of EMEC waves in presence and absence of AC field. Through comprehensive mathematical analysis it is found that when EMEC wave propagates parallel to intrinsic magnetic field of Uranus, its growth is more enhanced than in case of oblique propagation. Results are also discussed in context to magnetosphere of Earth and also gives theoretical explanation to existence of high energetic particles observed by Voyager 2 in the magnetosphere of Uranus. The results can present a further insight into the nature of electroncyclotron instability condition for the whistler mode waves in the outer radiation belts of Uranus or other space plasmas.

Fieldtheoretic simulations of directed selfassembly in cylindrical confinement: placement and rectification aspects
NASA Astrophysics Data System (ADS)
Laachi, Nabil; Iwama, Tatsuhiro; Delaney, Kris T.; Kim, Bongkeun; Bristol, Robert; Shykind, David; Weinheimer, Corey J.; Fredrickson, Glenn H.
20140301
We have investigated the directed selfassembly (DSA) of cylinderforming block copolymers inside cylindrical guiding templates. To complement and corroborate our experimental study, we use fieldtheoretic simulations to examine the fluctuationsinduced variations in the size and position of the cylindrical microdomain that forms in the middle of the guiding hole. Our study goes beyond the usual meanfield approximation and selfconsistent field theory simulations (SCFT) and incorporates the effects of thermal fluctuations in the description of the selfassembly process using complex Langevin (CL) dynamics. In both our experimental and modeling efforts, we focus on minorblockattractive sidewalls and bottom substrates and neutral top surfaces and explore the properties of the formed cylinders, including fluctuations in the center position and the size of the domain, for various prepattern conditions. Our results indicate robust critical dimensions (CD) of the DSA cylinders relative to the incoming CD, with a sigma CD < 0.9nm. Likewise, we find that the DSA cylinders are accurately registered in the center of the guiding hole, with deviations in the holeinhole distance on the order of ≍ 0.71nm, translating to errors in the holetohole distance of ≍ 11.5nm.

Inclusion of persistence lengthbased secondary structure in replica field theoretic models of heteropolymer freezing
NASA Astrophysics Data System (ADS)
Weber, Jeffrey K.; Pande, Vijay S.
20130901
The protein folding problem has long represented a "holy grail" in statistical physics due to its physical complexity and its relevance to many human diseases. While past theoretical work has yielded apt descriptions of protein folding landscapes, recent largescale simulations have provided insights into protein folding that were impractical to obtain from early theories. In particular, the role that nonnative contacts play in protein folding, and their relation to the existence of misfolded, βsheet rich trap states on folding landscapes, has emerged as a topic of interest in the field. In this paper, we present a modified model of heteropolymer freezing that includes explicit secondary structural characteristics which allow observations of "intramolecular amyloid" states to be probed from a theoretical perspective. We introduce a variable persistence lengthbased energy penalty to a model Hamiltonian, and we illustrate how this modification alters the phase transitions present in the theory. We find, in particular, that inclusion of this variable persistence length increases both generic freezing and folding temperatures in the model, allowing both folding and glass transitions to occur in a more highly optimized fashion. We go on to discuss how these changes might relate to protein evolution, misfolding, and the emergence of intramolecular amyloid states.

Theoretical Investigation of Graphene Nanoribbon FieldEffect Transistors Designed for Digital Applications
NASA Astrophysics Data System (ADS)
Harada, Naoki; Sato, Shintaro; Yokoyama, Naoki
20130901
Nanometerscale, singlegate graphene nanoribbon Schottky barrier fieldeffect transistors (FETs) were theoretically investigated using selfconsistent atomistic simulation. The device geometry was determined by referring to the International Technology Roadmap for Semiconductors. The target performance levels were the requirements specified in the roadmap for 2024, particularly a maximum leakage current of 0.1 A/m, an oncurrent of 2017 A/m, and a delay time of 0.13 ps. The device conditions needed to meet these requirements were found to be a bandgap larger than 1.1 eV, a supply voltage of 0.6 V, and a gate length of 7 nm.

Constraints on field theoretical models for variation of the fine structure constant
NASA Astrophysics Data System (ADS)
Steinhardt, Charles L.
20050201
Recent theoretical ideas and observational claims suggest that the fine structure constant α may be variable. We examine a spectrum of models in which α is a function of a scalar field. Specifically, we consider three scenarios: oscillating α, monotonic time variation of α, and timeindependent α that is spatially varying. We examine the constraints imposed upon these theories by cosmological observations, particle detector experiments, and “fifth force” experiments. These constraints are very strong on models involving oscillation but cannot compete with bounds from the Oklo subnuclear reactor on models with monotonic timelike variation of α. One particular model with spatial variation is consistent with all current experimental and observational measurements, including those from two seemingly conflicting measurements of the fine structure constant using the many multiplet method on absorption lines.

Calculation of membrane bending rigidity using fieldtheoretic umbrella sampling.
PubMed
Smirnova, Y G; Müller, M
20151228
The freeenergy change of membrane shape transformations can be small, e.g., as in the case of membrane bending. Therefore, the calculation of the freeenergy difference between different membrane morphologies is a challenge. Here, we discuss a computational method  fieldtheoretic umbrella sampling  to compute the local chemical potential of a nonequilibrium configuration and illustrate how one can apply it to study freeenergy changes of membrane transformations using simulations. Specifically, the chemical potential profile of the bent membrane and the bending rigidity of membrane are calculated for a soft, coarsegrained amphiphile model and the MARTINI model of a dioleoylphosphatidylcholine (DOPC) membrane. PMID:26723640

Low field magnetoresistance in a 2D topological insulator based on wide HgTe quantum well.
PubMed
Olshanetsky, E B; Kvon, Z D; Gusev, G M; Mikhailov, N N; Dvoretsky, S A
20160901
Low field magnetoresistance is experimentally studied in a twodimensional topological insulator (TI) in both diffusive and quasiballistic samples fabricated on top of a wide (14 nm) HgTe quantum well. In all cases a pronounced quasilinear positive magnetoresistance is observed similar to that found previously in diffusive samples based on a narrow (8 nm) HgTe well. The experimental results are compared with the main existing theoretical models based on different types of disorder: sample edge roughness, nonmagnetic disorder in an otherwise coherent TI and metallic puddles due to locally trapped charges that act like local gate on the sample. The quasiballistic samples with resistance close to the expected quantized values also show a positive lowfield magnetoresistance but with a pronounced admixture of mesoscopic effects. PMID:27355623

Low field magnetoresistance in a 2D topological insulator based on wide HgTe quantum well
NASA Astrophysics Data System (ADS)
Olshanetsky, E. B.; Kvon, Z. D.; Gusev, G. M.; Mikhailov, N. N.; Dvoretsky, S. A.
20160901
Low field magnetoresistance is experimentally studied in a twodimensional topological insulator (TI) in both diffusive and quasiballistic samples fabricated on top of a wide (14 nm) HgTe quantum well. In all cases a pronounced quasilinear positive magnetoresistance is observed similar to that found previously in diffusive samples based on a narrow (8 nm) HgTe well. The experimental results are compared with the main existing theoretical models based on different types of disorder: sample edge roughness, nonmagnetic disorder in an otherwise coherent TI and metallic puddles due to locally trapped charges that act like local gate on the sample. The quasiballistic samples with resistance close to the expected quantized values also show a positive lowfield magnetoresistance but with a pronounced admixture of mesoscopic effects.

Real applications of quantum imaging
NASA Astrophysics Data System (ADS)
Genovese, Marco
20160701
In previous years the possibility of creating and manipulating quantum states of light has paved the way for the development of new technologies exploiting peculiar properties of quantum states, such as quantum information, quantum metrology and sensing, quantum imaging, etc. In particular quantum imaging addresses the possibility of overcoming limits of classical optics by using quantum resources such as entanglement or subPoissonian statistics. Albeit, quantum imaging is a more recent field than other quantum technologies, e.g. quantum information, it is now mature enough for application. Several different protocols have been proposed, some of them only theoretically, others with an experimental implementation and a few of them pointing to a clear application. Here we present a few of the most mature protocols ranging from ghost imaging to sub shot noise imaging and subRayleigh imaging.

On classical and quantum dynamics of tachyonlike fields and their cosmological implications
SciTech Connect
Dimitrijević, Dragoljub D. Djordjević, Goran S. Milošević, Milan; Vulcanov, Dumitru
20141124
We consider a class of tachyonlike potentials, motivated by string theory, Dbrane dynamics and inflation theory in the context of classical and quantum mechanics. A formalism for describing dynamics of tachyon fields in spatially homogenous and onedimensional  classical and quantum mechanical limit is proposed. A few models with concrete potentials are considered. Additionally, possibilities for padic and adelic generalization of these models are discussed. Classical actions and corresponding quantum propagators, in the Feynman path integral approach, are calculated in a form invariant on a change of the background number fields, i.e. on both archimedean and nonarchimedean spaces. Looking for a quantum origin of inflation, relevance of padic and adelic generalizations are briefly discussed.

Quantum Correlation of Two Entangled Atoms Interacting with the Binomial Optical Field
NASA Astrophysics Data System (ADS)
Liu, TangKun; Tao, Yu; Shan, ChuanJia; Liu, Jibing
20160501
Quantum correlations of two atoms in a system of two entangled atoms interacting with the binomial optical field are investigated. In eight different initial states of the two atoms, the influence of the strength of the dipoledipole interaction, probabilities of a the Bernoulli trial and particle number of the binomial optical field on the temporal evolution of the geometrical quantum discord between two atoms are discussed. The result shows that two atoms always exist the correlation for different parameters. In addition, when and only when the two atoms are initially in the maximally entangled state, the temporal evolution of geometrical quantum discord is not affected by the parameters, and always keep in the degree of geometrical quantum discord that is a fixed value.

Quantum tunneling from scalar fields in rotating black strings
NASA Astrophysics Data System (ADS)
Gohar, H.; Saifullah, K.
20130801
Using the HamiltonJacobi method of quantum tunneling and complex path integration, we study Hawking radiation of scalar particles from rotating black strings. We discuss tunneling of both charged and uncharged scalar particles from the event horizons. For this purpose, we use the KleinGordon equation and find the tunneling probability of outgoing scalar particles. The procedure gives Hawking temperature for rotating charged black strings as well.

Nonequilibrium GREEN’S Functions for HighField Quantum Transport Theory
NASA Astrophysics Data System (ADS)
Bertoncini, Rita
A formulation of the KadanoffBaymKeldysh theory of nonequilibrium quantum statistical mechanics is developed in order to describe nonperturbatively the effects of the electric field on electronphonon scattering in nondegenerate semiconductors. We derive an analytic, gaugeinvariant model for the spectral density of energy states that accounts for both intracollisional field effect and collisional broadening simultaneously. A kinetic equation for the quantum distribution function is derived and solved numerically. The nonlinear drift velocity versus applied field characteristics is also evaluated numerically. Many features of our nonlinear theory bear formal resemblance to linearresponse theory.

Construction and exact solution of a nonlinear quantum field model in quasihigher dimension
NASA Astrophysics Data System (ADS)
Kundu, Anjan
20151001
Nonperturbative exact solutions are allowed for quantum integrable models in one spacedimension. Going beyond this class we propose an alternative Lax matrix approach, exploiting the hidden multispacetime concept in integrable systems and construct a novel nonlinear Schrödinger quantum field model in quasitwo dimensions. An intriguing field commutator is discovered, confirming the integrability of the model and yielding its exact Bethe ansatz solution with rich scattering and boundstate properties. The universality of the scheme is expected to cover diverse models, opening up a new direction in the field.

Distance and coupling dependence of entanglement in the presence of a quantum field
NASA Astrophysics Data System (ADS)
Hsiang, J.T.; Hu, B. L.
20151201
We study the entanglement between two coupled detectors, the internal degrees of freedom of which are modeled by harmonic oscillators, interacting with a common quantum field, paying special attention to two less studied yet important features: finite separation and direct coupling. Distance dependence is essential in quantum teleportation and relativistic quantum information considerations. The presence of a quantum field as the environment accords an indirect interaction between the two oscillators at finite separation of a nonMarkovian nature which competes with the direct coupling between them. The interplay between these two factors results in a rich variety of interesting entanglement behaviors at late times. We show that the entanglement behavior reported in prior work assuming no separation between the detectors can at best be a transient effect at very short times and claims that such behaviors represent latetime entanglement are misplaced. Entanglement between the detectors with direct coupling enters in the consideration of macroscopic quantum phenomena and other frontline issues. We find that with direct coupling entanglement between the two detectors can sustain over a finite distance, in contrast to the no direct coupling case reported before, where entanglement cannot survive at a separation more than a few inverse highfrequency cutoff scales. This work provides a functional platform for systematic investigations into the entanglement behavior of continuous variable quantum systems, such as used in quantum electro and optomechanics.

Transient gainabsorption of the probe field in triple quantum dots coupled by double tunneling
NASA Astrophysics Data System (ADS)
Tian, SiCong; Zhang, XiaoJun; Wan, RenGang; Zhao, Shuai; Wu, Hao; Shu, ShiLi; Wang, LiJie; Tong, CunZhu
20160601
The transient gainabsorption property of the probe field in a linear triple quantum dots coupled by double tunneling is investigated. It is found that the additional tunneling can dramatically affect the transient behaviors under the transparency condition. The dependence of transient behaviors on other parameters, such as probe detuning, the pure dephasing decay rate of the quantum dots and the initial conditions of the population, are also discussed. The results can be explained by the properties of the dressed states generated by the additional tunneling. The scheme may have important application in quantum information network and communication.

Parallel magneticfieldinduced conductance fluctuations in one and twosubband ballistic quantum dots
NASA Astrophysics Data System (ADS)
Gustin, C.; Faniel, S.; Hackens, B.; Melinte, S.; Shayegan, M.; Bayot, V.
20031201
We report on conductance fluctuations of ballistic quantum dots in a strictly parallel magnetic field B. The quantum dots are patterned in twodimensional electron gases (2DEG’s), confined to 15 and 45nmthick GaAs quantum wells (QW) with one and two occupied subbands at B=0, respectively. For both dots we observe universal conductance fluctuations (UCF’s) and, in the case of the wide QW dot, a reduction in their amplitude at large B. Our data suggest that the finite thickness of the 2DEG and the orbital effect are responsible for the parallel Binduced UCF’s.

Group field theory as the second quantization of loop quantum gravity
NASA Astrophysics Data System (ADS)
Oriti, Daniele
20160401
We construct a second quantized reformulation of canonical loop quantum gravity (LQG) at both kinematical and dynamical level, in terms of a Fock space of spin networks, and show in full generality that it leads directly to the group field theory (GFT) formalism. In particular, we show the correspondence between canonical LQG dynamics and GFT dynamics leading to a specific GFT model from any definition of quantum canonical dynamics of spin networks. We exemplify the correspondence of dynamics in the specific example of 3d quantum gravity. The correspondence between canonical LQG and covariant spin foam models is obtained via the GFT definition of the latter.

Quantum teleportation of the angular spectrum of a singlephoton field
SciTech Connect
Walborn, S. P.; Ether, D. S.; Matos Filho, R. L. de; Zagury, N.
20070915
We propose a quantum teleportation scheme for the angular spectrum of a singlephoton field, which allows for the transmission of a large amount of information. Our proposal also provides a method to tune the frequencies of spatially entangled fields, which is useful for interactions with stationary qubits.

Relative unitary implementability of perturbed quantum field dynamics on deSitter space
NASA Astrophysics Data System (ADS)
Poon, Gary K.
In this article, we study the quantum dynamics of a KleinGordon field on deSitter space. We prove time evolution is not unitarily implementable. We also consider a KleinGordon field perturbed by a local potential V. In this case we prove that the deviation from the V = 0 dynamics is unitarily implementable.

Fault tolerant filtering and fault detection for quantum systems driven by fields in single photon states
NASA Astrophysics Data System (ADS)
Gao, Qing; Dong, Daoyi; Petersen, Ian R.; Rabitz, Herschel
20160601
The purpose of this paper is to solve the fault tolerant filtering and fault detection problem for a class of open quantum systems driven by a continuousmode bosonic input field in single photon states when the systems are subject to stochastic faults. Optimal estimates of both the system observables and the fault process are simultaneously calculated and characterized by a set of coupled recursive quantum stochastic differential equations.

Evidence for universal conductance fluctuations in an open quantum dot under a strictly parallel magnetic field
NASA Astrophysics Data System (ADS)
Gustin, C.; Faniel, S.; Hackens, B.; De Poortere, E. P.; Shayegan, M.; Bayot, V.
20030401
We investigate the transport properties of semiconductor ballistic cavities subject to a parallel magnetic field. Universal conductance fluctuations are observed on two GaAs/AlGaAs quantum well samples with one and two occupied carrier subbands, respectively. Large differences between the two open quantum dots in both the amplitude and frequency distribution of these fluctuations are analyzed in terms of electron orbital motion and magnetic subband depopulation.

Quantum statistical correlations in thermal field theories: Boundary effective theory
SciTech Connect
Bessa, A.; Brandt, F. T.; Carvalho, C. A. A. de; Fraga, E. S.
20100915
We show that the oneloop effective action at finite temperature for a scalar field with quartic interaction has the same renormalized expression as at zero temperature if written in terms of a certain classical field {phi}{sub c}, and if we trade free propagators at zero temperature for their finitetemperature counterparts. The result follows if we write the partition function as an integral over field eigenstates (boundary fields) of the density matrix element in the functional Schroedinger field representation, and perform a semiclassical expansion in two steps: first, we integrate around the saddle point for fixed boundary fields, which is the classical field {phi}{sub c}, a functional of the boundary fields; then, we perform a saddlepoint integration over the boundary fields, whose correlations characterize the thermal properties of the system. This procedure provides a dimensionally reduced effective theory for the thermal system. We calculate the twopoint correlation as an example.

Longitudinal wave function control in single quantum dots with an applied magnetic field
PubMed Central
Cao, Shuo; Tang, Jing; Gao, Yunan; Sun, Yue; Qiu, Kangsheng; Zhao, Yanhui; He, Min; Shi, JinAn; Gu, Lin; Williams, David A.; Sheng, Weidong; Jin, Kuijuan; Xu, Xiulai
20150101
Controlling singleparticle wave functions in single semiconductor quantum dots is in demand to implement solidstate quantum information processing and spintronics. Normally, particle wave functions can be tuned transversely by an perpendicular magnetic field. We report a longitudinal wave function control in single quantum dots with a magnetic field. For a pure InAs quantum dot with a shape of pyramid or truncated pyramid, the hole wave function always occupies the base because of the less confinement at base, which induces a permanent dipole oriented from base to apex. With applying magnetic field along the baseapex direction, the hole wave function shrinks in the base plane. Because of the linear changing of the confinement for hole wave function from base to apex, the center of effective mass moves up during shrinking process. Due to the uniform confine potential for electrons, the center of effective mass of electrons does not move much, which results in a permanent dipole moment change and an inverted electronhole alignment along the magnetic field direction. Manipulating the wave function longitudinally not only provides an alternative way to control the charge distribution with magnetic field but also a new method to tune electronhole interaction in single quantum dots. PMID:25624018

Theoretical model of the polarization Coulomb field scattering in strained AlGaN/AlN/GaN heterostructure fieldeffect transistors
SciTech Connect
Luan, Chongbiao; Lin, Zhaojun Zhao, Jingtao; Wang, Yutang; Lv, Yuanjie; Chen, Hong; Wang, Zhanguo
20140728
The theoretical model of the polarization Coulomb field scattering (PCF) caused by the polarization charge density variation at the AlGaN/AlN interface in strained AlGaN/AlN/GaN heterostructure fieldeffect transistors has been developed. And the theoretical values for the electron drift mobility, which were calculated using the Matthiessen's rule that includes PCF, piezoelectric scattering, polar opticalphonon scattering, and interface roughness scattering, are in good agreement with our experimental values. Therefore, the theoretical model for PCF has been confirmed.

Ordinary versus PTsymmetric Φ³ quantum field theory
DOE PAGESBeta
Bender, Carl M.; Branchina, Vincenzo; Messina, Emanuele
20120402
A quantummechanical theory is PTsymmetric if it is described by a Hamiltonian that commutes with PT, where the operator P performs space reflection and the operator T performs time reversal. A PTsymmetric Hamiltonian often has a parametric region of unbroken PT symmetry in which the energy eigenvalues are all real. There may also be a region of broken PT symmetry in which some of the eigenvalues are complex. These regions are separated by a phase transition that has been repeatedly observed in laboratory experiments. This paper focuses on the properties of a PTsymmetric igΦ³ quantum field theory. This quantum fieldmore » theory is the analog of the PTsymmetric quantummechanical theory described by the Hamiltonian H=p²+ix³, whose eigenvalues have been rigorously shown to be all real. This paper compares the renormalization group properties of a conventional Hermitian gΦ³ quantum field theory with those of the PTsymmetric igΦ³ quantum field theory. It is shown that while the conventional gΦ³ theory in d=6 dimensions is asymptotically free, the igΦ³ theory is like a gΦ⁴ theory in d=4 dimensions; it is energetically stable, perturbatively renormalizable, and trivial.« less

Theoretical study of the photodissociation of Li2+ in onecolor intense laser fields
NASA Astrophysics Data System (ADS)
Li, Yuanjun; Jiang, Wanyi; Khait, Yuriy G.; Hoffmann, Mark R.
20110501
A theoretical treatment of the photodissociation of the molecular ion Li2+ in onecolor intense laser fields, using the timedependent wave packet approach in a Floquet BornOppenheimer representation, is presented. Six electronic states 1,2 2Σg+, 1,2 2Σu+, 1 2Πg, and 1 2Πu are of relevance in this simulation and have been included. The dependences of the fragmental dissociation probabilities and kinetic energy release (KER) spectra on pulse width, peak intensity, polarization angle, wavelength, and initial vibrational level are analyzed to interpret the influence of control parameters of the external field. Three main dissociation channels, 1 2Σg+ (m = 1), 2 2Σg+ (m = 2), and 2 2Σu+ (m = 3), are seen to dominate the dissociation processes under a wide variety of laser conditions and give rise to well separated groups of KER features. Different dissociation mechanisms for the involved Floquet channels are discussed.

Mean field game theoretic approach for security in mobile adhoc networks
NASA Astrophysics Data System (ADS)
Wang, Yanwei; Tang, Helen; Yu, F. Richard; Huang, Minyi
20130501
Game theory can provide a useful tool to study the security problem in mobile ad hoc networks (MANETs). Most existing work on applying game theories to security only considers two players in the security game model: an attacker and a defender. While this assumption is valid for a network with centralized administration, it may not be realistic in MANETs, where centralized administration is not available. Consequently, each individual node in a MANET should be treated separately in the security game model. In this paper, using recent advances in mean field game theory, we propose a novel game theoretic approach for security in MANETs. Mean field game theory provides a powerful mathematical tool for problems with a large number of players. Since security defence mechanisms consume precious system resources (e.g., energy), the proposed scheme considers not only the security requirement of MANETs but also the system resources. In addition, each node only needs to know its own state information and the aggregate effect of the other nodes in the MANET. Therefore, the proposed scheme is a fully distributed scheme. Simulation results are presented to illustrate the effectiveness of the proposed scheme.
 