Casimir Effect at Finite Temperature in the Presence of Compactified Universal Extra Dimensions

We analyse the Casimir effect for parallel plates at finite temperature in the presence of compactified universal extra dimensions and analytically show the thermal corrections to the effect in detail. The Casimir effect for different sizes of universal extra dimensions is investigated to test the five-dimensional Kaluza-Klein theory.     

Quantum Fluctuation in Mesoscopic Coupled LC Electric Circuits at Finite Temperature

We consider the quantization of two coupled LC circuits with mutual inductance at a finite temperature T.It is shown that the quantum mechanical zero-point fluctuations of currents in the two circuits both increase with upgoing T.Thermal field dynamics and Weyl-Wigner theorem are used in our calculation of ensemble everage of the observables.     

The Antiferromagnetic Correlations in the Half—Filled Double—Exchange Model at Finite Temperature

We extend a previous result of ours [G.S.Tian,Phys.Rev.B63 (2001) 224413] on the antiferromagnetic spin correlations in the half-filled Hubbard model at finite temperature to the double-exchange model.To overcome the mathematical difficulty cused by the S=3/2 localized spin freedom in this model,we apply both Zener‘s argument and the finite-temperature spin-reflection-positivity method to show rigorously that,at any temperature T,the spin correlations in the half-filled double-exchange model are predominantly antiferromagnetic.This conclusion is completely consistent with the experimental observations and the previous theoretical results by approximate methods.     

One ρ-Meson Exchange Potential at Finite Temperature

By means of the imaginary-time Green function method in finite-temperature field theory,one ρ-meson exchange potential at finite temperature is obtained.It is found that ρ-meson become lighter in terms of temperature increasing.The result is in good agreement with that obtained from scalling property of QCD.It is also found that temperature dependence of ρ-meson coupling constants is similar to that of,σ-meson coupling constants.     

Quantum Electrodynamics of Čerenkov Radiation at Finite Temperature

An exact, to order , study of erenkov radiation in QEDis carried out at finitetemperatures T 0 in isotropic homogeneous media for the first time. By avoidingthe method of combining denominators of Feynman propagators in parametricform, which has led to approximations in the past due to the complexity of theresulting integrals, we use instead a complex integration method and automaticallyevaluate the h ²²/E ²contribution to the quantum power spectrum and settle theambiguity associated with this term which has been known to exist at T = 0.We show that complex integration over a so-called pinching singularity actuallysimplifies the problem tremendously over the usual method of combining thedenominators of the propagators. In particular, the imaginary part of the electronself-energy satisfies the correct underlying boundary condition and no contactterm is needed in its evaluation. QED, unlike its classical counterpart, introducesautomatically a cutoff for higher frequencies, emphasizing the importance of thequantum treatment.     

Brownian Motion of a Charged Particle in Electromagnetic Fluctuations at Finite Temperature

The fluctuation-dissipation theorem is a central theorem in nonequilibrium statistical mechanics by which the evolution of velocity fluctuations of the Brownian particle under a fluctuating environment is intimately related to its dissipative behavior. This can be illuminated in particular by an example of Brownian motion in an ohmic environment where the dissipative effect can be accounted for by the first-order time derivative of the position. Here we explore the dynamics of the Brownian particle coupled to a supraohmic environment by considering the motion of a charged particle interacting with the electromagnetic fluctuations at finite temperature. We also derive particle’s equation of motion, the Langevin equation, by minimizing the corresponding stochastic effective action, which is obtained with the method of Feynman-Vernon influence functional. The fluctuation-dissipation theorem is established from first principles. The backreaction on the charge is known in terms of electromagnetic self-force given by a third-order time derivative of the position, leading to the supraohmic dynamics. This self-force can be argued to be insignificant throughout the evolution when the charge barely moves. The stochastic force arising from the supraohmic environment is found to have both positive and negative correlations, and it drives the charge into a fluctuating motion. Although positive force correlations give rise to the growth of the velocity dispersion initially, its growth slows down when correlation turns negative, and finally halts, thus leading to the saturation of the velocity dispersion. The saturation mechanism in a supraohmic environment is found to be distinctly different from that in an ohmic environment. The comparison is discussed.     

One η-Meson Exchange Potential of Nucleon-Nucleon at Finite Temperature

By means of the imaginary-time Green's function method,the temperature dependences of the η-meson and nucleon interaction coupling constant and one one η-meson exchange potential are discussed.We find that when temperature increases to 215MeV,the coupling constant approaches to zero and the one η-meson exchange potential of nucleon-nucleon disappears.     

Vextex Corrections and one σ Exchange Potential at Finite Temperature

By using the imaginary-time Green's function method in finite temperature field theory,we calculate the effects of the three-line vertex function on finite temperature one σ-meson exchange potential.It is found that the finite temperature coupling constant of the sigma-nucleon interaction decreases as the temperature increases,it approaches zero when temperature arrives at 210MeV.This result is quite similar to that the temperature dependence of coupling constant given by Nambu-Jona-Lasinia model at the quark level.     

Effect of σ*,φ Mesons on the Neutron Star Matter at Finite Temperature

Within the RMF approach, considering the contribution of σ*,φ mesons and baryon octet {n,p,Λ,Σ^－,Σ⁰,Σ⁺,Ξ^－,Ξ⁰}, some properties of neutron star matter have been investigated in the temperature region between 5—15MeV. It is found that when the contributions of σ*,φ mesons are included, (1) the critical baryon density decreases (but for the Λ hyperon, the effect is not obvious), but the number of hyperons increases; (2) the equation of state becomes soft at higher energy density; (3) the maximum mass decreases while the corresponding radius increases; (4) the central density, the central energy density, and the central pressure all become smaller. At T=5MeV and 10MeV and for Σ⁰,Ξ⁰,Σ⁺, the σ*,φ mesons make critical baryon density greatly decrease; but at T=15MeV, 20MeV, and 25MeV, the effect is not obvious. However, for Λ,Σ^－,Ξ^－ hyperons, at all the above temperatures, the effect is not obvious.     

Quantum Cosmology with a Complex φ4 Field at Finite Temperature

Quantum cosmology with a complex ⁴ fieldat finite temperature for the Vilenkin boundarycondition and the Hartle-Hawking boundary condition isstudied. The Euclidean region in minisuperspace isgenerally bounded by a closed curve. The wave function ofthe universe calculated in the WKB approximation cancross, through scattering or tunneling, from the initialclassically allowed region to the final classically allowed region. For a given value of scalarfield, the probability density for the Vilenkin boundarycondition is smallest at zero temperature, and whentemperature increases, the probability density rises remarkably. At the same time, the oppositeresults are given for Hartle-Hawking boundary condition.In addition, the classical trajectories of the universeare calculated in detail.     

Interacting Fermi Liquid in Two Dimensions¶at Finite Temperature.¶Part I: Convergent Attributions

Using the method of a continuous renormalization group around the Fermi surface, we prove that a two-dimensional interacting system of Fermions at low temperature T is a Fermi liquid in the domain , where K is some numerical constant. According to [S1], this means that it is analytic in the coupling constant λ, and that the first and second derivatives of the self energy obey uniform bounds in that range. This is also a step in the program of rigorous (non-perturbative) study of the BCS phase transition for many Fermion systems; it proves in particular that in dimension two the transition temperature (if any) must be non-perturbative in the coupling constant. The proof is organized into two parts: the present paper deals with the convergent contributions, and a companion paper (Part II) deals with the renormalization of dangerous two point subgraphs and achieves the proof. Received: 27 July 1999 / Accepted: 31 May 2000     

Soliton Solution of SU（3） Gauge Fields at Finite Temperature

Starting from a soliton model of SU（3） gauge fields, we investigate the behaviour of the model at finite temperature. it is found that colour confinement at zero temperature can be melted away under high temperatures.     

Controlling Sudden Birth and Sudden Death of Entanglement at Finite Temperature

The decoherence and the decay of quantum entanglement due to both population relaxation and thermal effects are investigated for the two qubits initially prepared in the extended Werner-like state by solving the Lindblad form of the master equation, where each qubit is interacting with an independent reservoir at finite temperature T. Entanglement sudden death (ESD) and entanglement sudden birth (ESB) are observed during the evolution process. We analyze in detail the effects of the mixedness, the degree of entanglement of the initial states and finite temperature on the time of entanglement sudden death and entanglement sudden birth. We also obtain an analytic formula for the steady state concurrence that shows its dependence on both the system parameters, the decoherence rate and finite temperature. These results arising from the combination of extended Werner-like initial state and independent thermal reservoirs suggest an approach to control the maximum possible concurrence even after the purity and finite temperature induce sudden birth, death and revival.     

The de Haas—van Alphen Oscillation in Two—Dimensional QED at Finite Temperature and Density

The de Haas-van Alphen oscillations in two-dimensional QED at finite temperature and density are investigated.It is shown that for a given particel density,besides the oscillation of magnetization,the chemical potential is also oscillating with the same period.Different from the earloier work (J.O.Andersen and T.Haugset,Phys.Rev.D51 (1995) 3073),the magnetization oscillations we studied have a correct nonrelativistic limit at zero temperature.     

To the question of electron angular distribution at Μ-meson decay

The paper describes the measurement of the angular distribution of electrons at the decay of-mesons in a longitudinal magnetic field. The results of measurement indicate that electrons are emitted with preference not only in the direction parallel to the spin orientation of -meson but also in the antiparallel direction in disagreement with the angular distribution predicted by theory.

---

-

- . , -, , , .

---

---

The authors thank N. V. Rabin for irradiating the nuclear emulsions, Prof. Dr. V. Petrílka and M. Suk for mediating relations with the Joint Institute of Nuclear Research in Dubna and Dr. J. Pernegr for valuable discussions and remarks. Thanks also go to H. Koutová and H. Slámová for carefully scanning the nuclear emulsions.     

Finite Temperature Schr?dinger Equation

We know Schr?dinger equation describes the dynamics of quantum systems, which don’t include temperature. In this paper, we propose finite temperature Schr?dinger equation, which can describe the quantum systems in an arbitrary temperature. When the temperature T=0, it become Shr?dinger equation.     

Marginal Distribution of Wigner Function in Mesoscopic RLC Circuit at Finite Temperature and Its Application

By means of the Weyl correspondence and Wigner theorem the marginal distribution of Wigner function in mesoscopic RLC circuit at finite temperature was discussed. Here we endow the Wigner function with a new physical meaning, i.e., its marginal distributions’ statistical average for q ²/(2C) and p ²/(2L) are the temperature-related energy stored in capacity and in inductance of the mesoscopic RLC circuit, respectively.     

Properties of theρ-meson in dense nuclear matter

The properties of-mesons in dense nuclear matter are studied in a model which satisfies unitarity and current conservation. The important coupling of the-meson to two pions as well as the strong mixing of pions and delta-nucleon-hole states in nuclear matter are included. The-meson self energy in nuclear matter is evaluated with in-medium pion propagators and the corresponding vertex corrections required by current conservation. We find that the-meson width grows drastically with increasing density while its mass remains almost unchanged.     

Equation of State of Asymmetric Nuclear Matter at Finite Temperature with a Three-body Force

In the present work, the equation of state of hot asymmetric nuclear matter nas Been investigated in the framework of the finite temperature Brueckner-Hartree-Fock (FTBHF) approach with a microscopic three-body force (TBF). The temperature dependence and the isospin dependence of the single particle properties, such as the proton and neutron single-particle potentials and effective masses have been studied. It is shown that the TBF gives a repulsive contribution to the proton or neutron single particle potential. The energy per nucleon versus asymmetry parameter is found to fulfill a parabolic relation as in the zero temperature case[I]. This means that the symmetry energy at finite temperature Esym can be extracted from‘ the energy difference between pure neutron matter and symmetric matter. The calculated symmetry energy is plotted in Fig.1. It