Lowering Critical Temperature in the Extended Quark Sigma Model at Finite Temperature

A phase transition, a critical temperature, and meson masses are studied in the extended quark sigma model, in which the effective mesonic potential is extended to include eighth-order mesonic interactions. The second derivative of the effective mesonic potential is applied to calculate the effective sigma and pion masses as functions of temperature. We find that the critical temperature assumes a lower value in comparison with that of original quark sigma model. A comparison with recent calculations of lattice QCD is introduced. The behavior of the phase transition remains unchanged when the higher-order mesonic interactions are included. We find that the spontaneous symmetry-breaking condition is necessary to satisfy the Goldstone theorem at low temperatures.     

Quark and Gluon Condensates at Finite Temperatures by the Linear Sigma Model Approach

Based on a linear sigma model, we discuss the mixing between a quark condensate and a gluon condensate. It is shown that the linear sigma model will not be self-consistent if we switch off the mixing coupling between glueball and chiral fields. By introducing a proper mixing coupling, we realize the second-order phase transitions of chiral symmetry restoration and deconfinement. We further show that the critical temperature of chirM symmetry restoration could not be larger than the temperature of deconfinement phase transition in all possible parameter spaces of our model.     

Bose-Einstein Condensation in Linear Sigma Model at Hartree Approximation

The BEG of charged pions is investigated in the framework of O（4） linear sigma model. By using Cornwall- Jackiw-Tomboufis formalism, we have derived the gap equations for the effective masses of the mesons at finite temperature and finite isospin density. The critical temperature and phase diagram of BEG are discussed in the non-chiral limit at Hartree approximation.     

CP Violation in the Linear Sigma Model

Motivated by the possibility of the formation of CP-odd domains in heavy ion collisions, we investigate the effects of CP violation on the chiral transition within the linear sigma model with two flavors of quarks. We also study how the CP-odd system is affected by the presence of a strong magnetic field, that is presumably generated in a non-central heavy ion collision. We find that both ingredients play an important role, influencing drastically the nature of the phase transition and the critical temperature.     

Sigma Meson Production in Nuclear Reactions

The sigma meson production in p ＋ ^12C and p A- ^40Ca reactions at the incident energy Ep = 1.5 GeV is investigated within the Quantum Molecular Dynamics model. The simulation results indicate a distinctive A dependence of the sigma production, that is, the increase of A is followed by an increase of the production cross sections. We find that the σ meson production in proton-induced reactions is strongly medium-dependent, and the produced σ mesons decaying in a denser medium experience a stronger mass shift towards lower masses. This mass shift is an experimentally accessible observable in the final state pion pairs, which do not suffer from reabsorption by the surrounding nucleons. It is pointed out that the ratio of measured sigma cross sections as a function of the sigma invariant-mass from various reactions is a good probe to explore the existence of the σ meson in a dense nuclear environment.     

Meson Effects on the Chiral Condensate at Finite Density

Meson corrections on the chiral condensate up to next-to-leading order in a 1/Nc expansion at finite densityare investigated in the NJL model with explicit chiral symmetry breaking. Compared with mean-field results, the chiralphase transition is still of the first order while the properties near the critical density for chiral phase transition are foundto change significantly.     

Phase Structure of the Semi-Classical Linear Sigma Model

In order to establish a quantitative framework for assessing the reliability of dynamical simulations of DCC phenomena with the semi-classical mean-field treatment of the linear model, we determine and discuss the phase structure implied by this approximate treatment. While the results appear to be physically reasonable for realistic scenarios, where the pion mass and the volume are finite, the approximate treatment might be less appropriate for idealized scenarios involving small masses and large volumes.     

Some Properties of πr Meson in Nuclear Matter with Finite Density

In the GCM we study some properties of π meson as the Goldstone bosons in a nuclear matter with finitedensity. Using the effective action in a nuclear matter, we calculate the decay constant and π mass as functions of thechemical potential. The relation between the chemical potential and the density of a nuclear matter is firstly given here.We find that fπ and mπ monotonously decrease as nuclear matter density increases. The result is consistent with theusual assumption that the chiral symmetry is gradually restored as the density of a nuclear matter increases.     

Properties of Proton Transfer in Hydrogen-Bonded Systems at Finite Temperature

The properties of proton transfer along hydrogen-bonded molecular systems are studied at finite temperature. The dynamic equations of the proton transport along the systems are obtained by using a completely quantummechanics method. From the dynamic equations and its soliton solutions we find out specific heat arising from the motionof solitons in the systems with finite temperature and the critical temperature of the soliton in the protein molecules,which is about 318 K. This shows that we can continuously study some biological phenomena in the living systems bythis model.     

Dirac Equation at Finite Temperature

In this paper, we propose finite temperature Dirac equation, which can describe the quantum systems in an arbitrary temperature for a relativistic particle of spin-1/2. When the temperature T=0, it become Dirac equation. With the equation, we can study the relativistic quantum systems in an arbitrary temperature.     

First-Principles Investigation of Mechanical and Thermodynamic Properties of Nickel Silicides at Finite Temperature

First-principles calculations are performed to investigate lattice parameters, elastic constants and 3D directional Young’s modulus E of nickel silicides (i.e., β-Ni₃Si, δ-Ni₂Si, θ-Ni₂Si, ε-NiSi, and θ-Ni₂Si), and thermodynamic properties, such as the Debye temperature, heat capacity, volumetric thermal expansion coefficient, at finite temperature are also explored in combination with the quasi-harmonic Debye model. The calculated results are in a good agreement with available experimental and theoretical values. The five compounds demonstrate elastic anisotropy. The dependence on the direction of stiffness is the greatest for δ-Ni₂Si and θ-Ni₂Si, when the stress is applied, while that for β-Ni₃Si is minimal. The bulk modulus B reduces with increasing temperature, implying that the resistance to volume deformation will weaken with temperature, and the capacity gradually descend for the compound sequence of β-Ni₃Si > δ-Ni₂Si > θ-Ni₂Si > ε-NiSi > θ-Ni₂Si. The temperature dependence of the Debye temperature ΘD is related to the change of lattice parameters, and ΘD gradually decreases for the compound sequence of ε-NiSi > β-Ni₃Si > δ-Ni₂Si > θ-Ni₂Si > θ-Ni₂Si. The volumetric thermal expansion coefficient αV, isochoric heat capacity and isobaric heat capacity C _p of nickel silicides are proportional to T³ at low temperature, subsequently, αV and C _p show modest linear change at high temperature, whereas C_v obeys the Dulong-Petit limit. In addition, β-Ni₃Si has the largest capability to store or release heat at high temperature. From the perspective of solid state physics, the thermodynamic properties at finite temperature can be used to guide further experimental works and design of novel nickel–silicon alloys.

     

Effects of Composite Pions on the Chiral Condensate within the PNJL Model at Finite Temperature

We investigate the effect of composite pions on the behaviour of the chiral condensate at finite temperature within the Polyakov-loop improved NJL model. To this end we treat quark-antiquark correlations in the pion channel (bound states and scattering continuum) within a Beth–Uhlenbeck approach that uses medium-dependent phase shifts. A striking medium effect is the Mott transition which occurs when the binding energy vanishes and the discrete pion bound state merges the continuum. This transition is triggered by the lowering of the continuum edge due to the chiral restoration transition. This in turn also entails a modification of the Polyakov-loop so that the SU(3) center symmetry gets broken at finite temperature and dynamical quarks (and gluons) appear in the system, taking over the role of the dominant degrees of freedom from the pions. At low temperatures our model reproduces the chiral perturbation theory result for the chiral condensate while at high temperatures the PNJL model result is recovered. The new aspect of the current work is a consistent treatment of the chiral restoration transition region within the Beth–Uhlenbeck approach on the basis of mesonic phase shifts for the treatment of the correlations.     

Non-relativistic Quantum Theory at Finite Temperature

We propose the non-relativistic finite temperature quantum wave equations for a single particle and multiple particles. We give the relation between energy eigenvalues, eigenfunctions, transition frequency and temperature, and obtain some results: (1) when the degeneracies of two energy levels are same, the transition frequency between the two energy levels is unchanged when the temperature is changed. (2) When the degeneracies of two energy levels are different, the variance of transition frequency at two energy levels is direct proportion to temperature difference.     

Gravitational Casimir Effect at Finite Temperature

The energy-momentum tensor for the gravitoelectromagnetism-(GEM) theory in the real-time finite temperature field theory formalism is presented. Expressions for the Casimir energy and pressure at zero and finite temperature are obtained. An analysis of the Casimir effect for the GEM field is developed.     

The Hierarchy Principle and the Large Mass Limit of the Linear Sigma Model

In perturbation theory we study the matching in four dimensions between the linear sigma model in the large mass limit and the renormalized nonlinear sigma model in the recently proposed flat connection formalism. We consider both the chiral limit and the strong coupling limit of the linear sigma model. Our formalism extends to Green functions with an arbitrary number of pion legs, at one loop level, on the basis of the hierarchy as an efficient unifying principle that governs both limits. While the chiral limit is straightforward, the matching in the strong coupling limit requires careful use of the normalization conditions of the linear theory, in order to exploit the functional equation and the complete set of local solutions of its linearized form.     

用Weyl-Wigner理论研究有限温度下介观电路的量子特性

利用相于热态表象理论,研究有限温度下RLC电路的Wigner函数及量子涨落.借助于Weyl-Wigner理论讨论了介观RLC电路Wigner函数的边缘分布.结果表明:Wigner函数边缘分布的统计平均正好是储存在介观RLC电路中电容和电感上的能量.