On the symmetry improved CJT formalism in the O(4)O(4) linear sigma model

By using the symmetry improved CJT effective formalism developed by Pilaftsis and Teresi, the chiral phase transition is reconsidered in the framework of the $O(4)$ linear sigma model in chiral limit. Our results confirm the restorations of the second-order phase transition and the Goldstone theorem in the Hartree approximation. Finally, we explicitly calculate the effective potentials via the order parameter for various temperatures and address advantages of the present method in comparison with the $O(N)$ model in large-$N$ approximation.Comment: 11 pages, 3 figures, corrected typos and added references, Accepted for publication in Nuclear Physics

Nontopological Soliton in the Polyakov Quark Meson Model

Within a mean field approximation, we study a nontopological soliton solution of the Polyakov quark-meson model in the presence of a fermionic vacuum term with two flavors at finite temperature and density. The profile of the effective potential exhibits a stable soliton solution below a critical temperature $T\leq T_{\chi}^c$ for both the crossover and the first-order phase transitions, and these solutions are calculated here with appropriate boundary conditions. However, it is found that only if $T\leq T^c_d$,the energy of the soliton $M_N$ is less than the energy of the three free constituent quarks $3M_q$. As $T> T^c_d$, there is an instant delocalization phase transition from hadron matter to quark matter. The phase diagram together with the location of a critical end point (CEP) has been obtained in $T$ and $\mu$ plane. We notice that two critical temperatures always satisfy $T^c_d\leq T_{\chi}^c$. Finally, we present and compare the result of thermodynamic pressure at zero chemical potential with lattice data.Comment: 17 pages, 9 figures, Accepted for publication in Physical Review C. arXiv admin note: text overlap with arXiv:1301.622

Domain Wall in the Linear Sigma Model

We discuss the role of the axial $U(1)_A$ symmetry in the chiral phase transition using the $U(N_f)_R\times U(N_f)_L$ linear sigma model with two massless quark flavors. We expect that above a certain temperature the axial $U(1)_A$ symmetry will be effectively restored as well as $SU(N_f)_R\times SU(N_f)_L$. Then we can construct a string-like static solution the $\eta$ string and a kink-like classical solution the domain wall during the chiral phase transition. We give out the possible signals for detecting the domain wall in ultrarelativistic heavy-ion collisions.Comment: 4 page

On geometric and algebraic transience for discrete-time Markov chains

General characterizations of ergodic Markov chains have been developed in considerable detail. In this paper, we study the transience for discrete-time Markov chains on general state spaces, including the geometric transience and algebraic transience. Criteria are presented through establishing the drift condition and considering the first return time. As an application, we give explicit criteria for the random walk on the half line and the skip-free chain on nonnegative integers.Comment: 31 page

Pion String evolving in a thermal bath

By using the symmetry improved CJT effective formalism, we study a pion string of the $O(4)$ linear sigma model at finite temperature in chiral limit. In terms of the Kibble-Zurek mechanism we reconsider the production and evolution of the pion string in a thermal bath. Finally, we estimate the pion string density and its possible signal during the chiral phase transition.Comment: 13 pages, 3 figures,Accepted for publication in Physical Review D. arXiv admin note: text overlap with arXiv:1310.1600 by other author

Nucleon Properties in the Polyakov Quark Meson Model

We study the nucleon as a nontopological soliton in a quark medium as well as in a nucleon medium in terms of the Polyakov quark meson (PQM) model with two flavors at finite temperature and density. The constituent quark masses evolving with the temperature at various baryon chemical potentials are calculated and the equations of motion are solved according to the proper boundary conditions. The PQM model predicts an increasing size of the nucleon and a reduction of the nucleon mass in both hot environment. However, the phase structure is different from each other in quark and nucleon mediums. There is a crossover in the low-density region and a first-order phase transition in the high-density region in quark medium, whereas there exists a crossover characterized by the overlap of the nucleons in nucleon medium.Comment: 14 pages, 7 figures, Accepted for publication in Physical Review

Discord and entanglement in non-Markovian environments at finite temperature

The dynamics evolutions of discord and entanglement of two atoms in two independent Lorentzian reservoirs at zero or finite temperature have been investigated by using the time-convolutionless master-equation method. Our results show that, when both the non-Markovian effect and the detuning are present simultaneously, due to the memory and feedback effect of the non-Markovian reservoirs, the discord and the entanglement can be effectively protected even at nonzero temperature by increasing the non-Markovian effect and the detuning. The discord and the entanglement have different robustness for different initial states and their robustness may changes under certain conditions. Nonzero temperature can accelerate the decays of discord and entanglement and induce the entanglement sudden death.Comment: 13 pages, 6 figure

Squeezing of light field in a dissipative Jaynes-Cummings model

Based on the time-convolutionless master-equation approach, we investigate squeezing of light field in a dissipative Jaynes-Cummings model. The results show that squeezing light can be generated when the atom transits to a ground state from an excited state, and then a collapse-revival phenomenon will occur in the squeezing of light field due to atom-cavity coupling. Enhancing the atom-cavity coupling can increase the frequency of the collapse-revival of squeezing. The stronger the non-Markovian effect is, the more obvious the collapse-revival phenomenon is. The oscillatory frequency of the squeezing is dependents on the resonant frequency of the atom-cavity

Chiral soliton model at finite temperature and density

In mean field approximation, we study a chiral soliton of the linear sigma model with two flavors at finite temperature and density. The stable soliton solutions are calculated with some appropriate boundary conditions. Energy and radius of the soliton are determined in a hot medium of constituent quarks. It is found that for $T<T_c$, the energy of the soliton $E^*$ is less than the energy of three constituent quarks $3M_q$, but with the increasing of temperature, the difference between $E^*$ and $3M_q$ becomes smaller and smaller, once $T>T_c$, there is a sharp delocalization phase transition from hadron matter to quark matter coincident with the restoration of chiral symmetry. In the transition region, the thermodynamic properties show large discontinuities which is an indication for a first-order phase transition.Comment: 14 pages, 7 figures, version accepted for publication in Physical Review

Analytical solution and entanglement swapping of a double Jaynes-Cummings model in non-Markovian environments

Analytical solution and entanglement swapping of a double Jaynes-Cummings model in non-Markovian environments are investigated by the timeconvolutionless master equation method. We obtain the analytical solution of this model and discuss in detail the influence of atom-cavity coupling, non-Markovian effect and initial state purity on entanglement dynamics. The results show that, in the non-Markovian environments, the entanglement between two cavities can be swapped to other bipartite subsystems by interaction between an atom and its own cavity. Due to the dissipation of environment, the entanglements of all bipartite subsystems will eventually decay to zero when the atom couples weakly to its cavity and the non-Markovian effect is also weak. All bipartite subsystems can tend to steady entanglement states if and only if there is the strong atom-cavity coupling or the strong non-Markovian effect. The steady state of the subsystem composed of an atom and its own cavity is independent on the purity but the steady states of other bipartite subsystems are dependent on the purity.Comment: 14 pages, 9 figures