We investigate the QCD magnetic susceptibility chi at the finite quark-chemical potential (mu>0) and at zero temperature (T=0) to explore the pattern of the magnetic phase transition of the QCD vacuum. For this purpose, we employ the nonlocal chiral quark model derived from the instanton vacuum in the presence of the chemical potential in the chiral limit. Focusing on the Nambu-Goldstone phase, we find that the magnetic susceptibility remains almost stable to mu~200 MeV, and falls down drastically until the the quark-chemical potential reaches the critical point mu_c~320 MeV. Then, the strength of the chi is reduced to be about a half of that at mu=0, and the first-order magnetic phase transition takes place, corresponding to the chiral restoration. From these observations, we conclude that the response of the QCD vacuum becomes weak and unstable to the external electromagnetic field near the critical point, in comparison to that for vacuum. It is also shown that the breakdown of Lorentz invariance for the magnetic susceptibility, caused by the finite chemical potential, turns out to be small.
Calculation of tensor susceptibility beyond rainbow-ladder approximation of Dyson-Schwinger equations approach
本文推广了[Y. M. Shi，K. P. Wu，W. M. Sun，H. S. Zong，J. L. Ping，Phys. Lett. B $\bf{639}$，248（2006）]的方法与采用Ball-Chiu（BC）顶点的方法相比。研究了夸克胶子顶点的修饰效应对张量真空磁化率的影响。结果表明，与彩虹梯近似值相比，在BC顶点近似下得到的张量真空磁化率降低了约10%。这说明在DS方法中计算张量真空磁化率时，夸克胶子顶点的修饰效应并不大。
We estimate here chiral susceptibility at finite temperature within the framework of the Nambu-Jona-Lasinio model (NJL) using the Wigner function approach. We also estimate it in the presence of chiral chemical potential ($μ_5$) as well as a non vanishing magnetic field ($B$). We use medium separation regularization scheme (MSS) to calculate the chiral condensate and corresponding susceptibility. It is observed that for a fixed value of chiral chemical potential ($μ_5$), transition temperature increases with the magnetic field. While for the fixed value of the magnetic field, transition temper…
We study the $θ$-vacuum of QCD using two-flavor chiral perturbation theory ($χ$PT) in the presence of a uniform, background magnetic field calculating the magnetic field-dependent free energy density, the topological density, the topological susceptibility and the fourth cumulant at one-loop order. We find that the topological susceptibility is enhanced by the magnetic field while the fourth topological cumulant is diminished at weak fields and enhanced at larger fields when $θ=0$. However, in the QCD vacuum with $θ\neq 0$, the topological susceptibility can be either monotonically enhanced or…
单重态耦合到瞬子真空中的拓扑电荷密度，导致瞬子和反瞬子在1/2 fm量级的距离上被屏蔽。稀瞬子系统表现为自由气体，而致密瞬子系统表现为等离子体。1 fm $^{-4}$的密度有利于自由气体行为。由于希格斯机制，$η$的质量很重（1100 MeV）。真空拓扑磁化率很小（0.07 fm $^{-4}$），与QCD沃德恒等式一致。在手征极限下，单重屏蔽消失，导致四维等离子体状态，其温度由九重衰变常数$f$（90 MeV）给出。相位是德拜屏蔽的。在物质的存在下，屏蔽被淬灭，并且可能发生Kosterlitz-numerless跃迁，这表明$U_A(1)$对称性的恢复。我们建议利用静态拓扑电荷相关器的空间渐近性和拓扑磁化率来研究有限温度QCD中$U_A(1)$恢复和手征恢复之间的相互作用。这些结果的相关性，在瞬子真空体热力学进行了讨论。
When thermal rate equations are derived for the evolution of slow variables, it is often practical to parametrize the right-hand side with chemical potentials. To close the system, the chemical potentials are subsequently re-expressed in terms of the slow variables, which involves the consideration of a "susceptibility". Here we study a non-relativistic situation in which chemical potentials are large compared with the temperature, as is relevant for late-time pair annihilations in dark matter freeze-out. An order-of-magnitude estimate and a lattice simulation are presented for a susceptibilit…
$S$-matrix calculation of $BQ$ correlation at finite baryon density
Fakulta jaderná a fyzikálně inženýrská, České vysoké učení technické v Praze（捷克布拉格捷克理工大学核与物理工程学院）；Institute of Theoretical Physics, University of Wrocław（弗罗茨瓦夫大学理论物理研究所）；Fakulta prírodných vied, Univerzita Mateja Bela（马特乌·贝拉大学自然科学学院）
We have computed the chiral susceptibility in quark-gluon plasma in presence of finite chemical potential and weak magnetic field within hard thermal loop approximation. First we construct the massive effective quark propagator in a thermomagnetic medium. Then we obtain completely analytic expression for the chiral susceptibility in weak magnetic field approximation. In the absence of magnetic field the thermal chiral susceptibility increases in presence of finite chemical potential. The effect of thermomagnetic correction is found to be very marginal as temperature is the dominant scale in we…
We investigate the rotating quark matter in the three-flavor Nambu and Jona-Lasinio (NJL) model. The chiral condensation, spin polarization and number susceptibility of the light and strange quarks are carefully studied at finite temperature without or with finite chemical potential in this model. We find that the rotation suppresses the chiral condensation and enhances the first-order quark spin polarization, however for the second-order quark spin polarization and quark number susceptibility the effect is complicated and interesting. When extending to the situation with finite chemical poten…
In this work, we compute the hard thermal loop pressure of quark-gluon plasma within strong magnetic field approximation at one-loop order. Magnetic field breaks the rotational symmetry of the system. As a result, the pressure of QGP becomes anisotropic and one finds two different pressures along the longitudinal (along the magnetic field direction) and transverse direction. Similarly, the second-order quark number susceptibility, which represents the fluctuation of the net quark number density, also becomes anisotropic. We compute the second order QNS of deconfined QCD matter in strong field …
We study the topological susceptibility and the fourth cumulant of the QCD vacuum in the presence of a uniform, background magnetic field in two-and-three flavor QCD finding novel, model-independent sum rules relating the shift in the topological susceptibility due to the background field to the shift in the quark condensates, and the shift in the fourth cumulant to the shifts in the quark condensates and susceptibilities
A thermodynamically consistent quasi-particle model without density-dependent infinity of the vacuum zero point energy
本文推广了J. Cao等人提出的改进的准粒子模型，[ Phys. Lett. B { \bf 711}，65（2012）]从有限温度和零化学势的情形推广到有限化学势和零温度的情形，并计算了零温度和高密度下（2+1）味量子色动力学（QCD）的物态方程。我们首先计算了有限温度和有限化学势下的配分函数，然后到极限$T=0$，得到了冷稠密QCD的物态方程，这对中子星的研究具有重要意义。利用该状态方程计算了零温有限化学势下的夸克数密度、能量密度、夸克数磁化率和声速，并与已有文献的相应结果进行了比较.
The Equation of State and Quark Number Susceptibility in Hard-Dense-Loop Approximation
基于[ H. S. Zong，W. M. Sun，Phys. Rev. \textbf{D 78}，054001（2008）]，我们在硬稠密圈（HDL）近似下计算了零温有限夸克化学势下QCD的物态方程。本文将HDL近似下的状态方程与Fraga、Pisarski和Schaffner-Bielich提出的QCD冷微扰状态方程作了比较。结果表明，HDL近似下的压强一般比微扰结果小。此外，我们还计算了有限温度和有限化学势下的夸克数磁化率（QNS），并将所得结果与文献中的相应结果进行了比较.
