Search

In this paper, we use the self-consistent mean field approximation to study the Quantum Chromodynamics (QCD) phase transition. In the self-consistent mean field approximation of the Nambu–Jona-Lasinio (NJL) model, a parameter α is introduced, which reflects the weight of "direct" channel and the "exchange" channel and needs to be determined by experiments (as mentioned in a recent work [T. Zhao, W. Zheng, F. Wang, C.-M. Li, Y. Yan, Y.-F. Huang and H.-S. Zong, Phys. Rev. D100, 043018 (2019)], the results with α = 0. 9 are in good agreement with astronomical observation data on the latest binary neutron star merging. This indicates that the contribution of "exchange" channel should be considered, and α = 0. 9 is a possible choice). By comparing the results with different parameter α 's (α = 0 , α = 0. 5 and α = 0. 9), we study the influence of "exchange" channel on the behavior of the solutions of the quark gap equation and the critical point of chiral phase transition. Our results show that the second-order chiral phase turns to the crossover from the chiral limit to the non-chiral limit around μ = 3 6 0 MeV in the case of α = 0. 9. The difference of the quark mass with different α 's mainly occurs in the intermediate temperatures for the different fixed chemical potentials. At zero temperature and the chemical potential μ = 3 3 4 MeV there will be two solutions (including a meta-stable solution) of gap equation with α = 0 , and as α increases it will be only one solution left (the meta-stable solution will disappear until α = 0. 5). Besides, the discrepancy of the critical temperature (above which the pseudo-Wigner solution and negative Nambu solution will disappear) in the three cases of α = 0 , 0. 5 , 0. 9 will become large when the chemical potential increases. [ABSTRACT FROM AUTHOR]

We use the Skyrme Lagrangian with a finite pion mass term to study the stability of the skyrmion at finite isospin chemical potential μ I . It is found that there is a critical value μ I c ≃ 1 7 0  MeV, and there is no stable solution above the μ I c . We also explore the behavior of different skyrmion parameters as a function of μ I , in particular the isovector electric root-mean-square (rms) charge radius in this work. Then, using the Hamiltonian formulation, in terms of collective variables, we study the behavior of nucleons mass splitting at finite isospin chemical potential. We find the proton mass decreases and the neutron mass increases when μ I < μ I c . Finally, we also discuss the magnetic moments and the pion-nucleon sigma term σ as a function of isospin chemical potential for interest. [ABSTRACT FROM AUTHOR]

In this paper, chiral chemical potential μ 5 is introduced to investigate the QCD susceptibilities and chiral phase transition within the Polyakov-loop-extended Nambu–Jona-Lasinio models in the mean-field approximation. We concentrate on the effect of chiral chemical potential on the phase diagram and the QCD susceptibilities. Moreover, it is worth noting that chiral chemical potential has more and more prominent impact on the susceptibilities and the phase diagram with the decrease of temperature based on our results, which coincides with the prediction that the chiral symmetry is dynamically broken in the first-order phase transition region and gets partly restored in the crossover region. [ABSTRACT FROM AUTHOR]

Based on the two flavor Nambu–Jona-Lasinio (NJL) model with a proper time regularization, we used stationary wave condition (SWC) for the first time to study the influence of the finite volume effects on the chiral phase transition of quark matter at finite temperature. It is found that when the cubic volume size L is larger than L max SWC = 5 0 0  fm, the chiral quark condensate is indistinguishable from that at L = ∞. Here, it should be noted that 500 fm is far greater than the size of QGP produced at laboratory and the lattice QCD simulation space size. It is also much larger than the previous limit size L max APBC = 5 fm estimated by the commonly used anti-periodic boundary condition (APBC). We also found that when the space size L is less than L min SWC = 0. 2 5  fm, the spontaneous symmetry breaking concept is no longer valid. In addition, we first introduce the spatial susceptibility, and through the study of the spatial susceptibility, it was revealed for the first time that the chiral phase transition caused by the finite volume effects in the non-chiral limit is a crossover. [ABSTRACT FROM AUTHOR]

The contact plays an important role in the study of ultracold atoms. We determine the contact from the high-frequency asymptotic behavior of radio-frequency spectrum for a homogeneous Fermi gas at unitarity in the normal phase. The contact is obtained within the framework of the non-self-consistent T-matrix approximation with particle–hole fluctuation. [ABSTRACT FROM AUTHOR]

We compute the momentum distribution of a homogeneous Fermi gas at unitarity in the normal phase within the framework of the non-self-consistent T-matrix approximation with particle-hole fluctuation. From the large-momentum behavior of momentum distribution, we obtain the contact for the unitary Fermi gas. We also compare our results with experimental data and other theoretical predictions. [ABSTRACT FROM AUTHOR]

We calculate the pressure and entropy of a unitary Fermi gas based on universal relations combined with our previous prediction of energy which was calculated within the framework of the non-self-consistent T-matrix approximation with particle-hole fluctuation. The resulting entropy and pressure are compared with the experimental data and the theoretical results without induced interaction. For entropy, we find good agreement between our results with particle-hole fluctuation and the experimental measurements reported by ENS group and MIT experiment. For pressure, our results suffer from a systematic upshift compared to MIT data. [ABSTRACT FROM AUTHOR]

Based on the experimental observation that there is a coexisting region between the antiferromagnetic (AF) and d-wave superconducting ( dSC) phases, the influences of gauge boson mass m on chiral symmetry restoration and deconfinement phase transitions in QED are investigated simultaneously within a unified framework, i.e., Dyson-Schwinger equations. The results show that the chiral symmetry restoration phase transition in the presence of the gauge boson mass m is a typical second-order phase transition; the chiral symmetry restoration and deconfinement phase transitions are coincident; the critical number of fermion flavors N decreases as the gauge boson mass m increases, which implies that there exists a boundary that separates the N - m plane into chiral symmetry breaking/confinement region for ( N , m ) below the boundary and chiral symmetry restoration/deconfinement region for ( N , m ) above it. [ABSTRACT FROM AUTHOR]