磁场诱导的QCD中的胶子（逆）催化和压力（an）各向同性
Magnetic field-induced gluonic (inverse) catalysis and pressure (an)isotropy in QCD
摘要：
利用格点模拟方法，研究了零温和非零温下强外磁场对QCD真空中胶子和费米子观测量的影响.胶子作用量密度在低温下经历磁催化，在相变温度附近和之上经历逆磁催化，类似于夸克凝聚。此外，胶子作用产生了各向异性：平行于外场的色磁场增强，而在这个方向上的色电场被抑制。我们证明了相同的层次结构，得到使用欧拉-海森堡有效作用。相反，拓扑电荷密度相关器在磁场eB~1 GeV ^2范围内没有显示出明显的各向异性。此外，我们表明，即使非零磁场的压力保持各向同性，如果它是通过在固定的外部磁场的系统的压缩定义。相反，如果在压缩过程中场的通量保持固定--这是晶格模拟中实现的情况--压力会产生各向异性。我们估计夸克和胶子的贡献，这种各向异性，并将它们与QCD真空的磁化。在进行电荷重整化后，我们得到了磁化强度的估计，这表明QCD是顺磁性的。
英文摘要：
We study the influence of strong external magnetic fields on gluonic and fermionic observables in the QCD vacuum at zero and nonzero temperatures, via lattice simulations with N_f=1+1+1 staggered quarks of physical masses. The gluonic action density is found to undergo magnetic catalysis at low temperatures and inverse magnetic catalysis near and above the transition temperature, similar to the quark condensate. Moreover, the gluonic action develops an anisotropy: the chromo-magnetic field parallel to the external field is enhanced, while the chromo-electric field in this direction is suppressed. We demonstrate that the same hierarchy is obtained using the Euler-Heisenberg effective action. Conversely, the topological charge density correlator does not reveal a significant anisotropy up to magnetic fields eB~1 GeV^2. Furthermore, we show that the pressure remains isotropic even for nonzero magnetic fields, if it is defined through a compression of the system at fixed external field. In contrast, if the flux of the field is kept fixed during the compression -- which is the situation realized in the lattice simulation -- the pressure develops an anisotropy. We estimate the quark and gluonic contributions to this anisotropy, and relate them to the magnetization of the QCD vacuum. After performing electric charge renormalization, we obtain an estimate for the magnetization, which indicates that QCD is paramagnetic.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
