Magnetic field-induced gluonic (inverse) catalysis and pressure (an)isotropy in QCD
Magnetic field-induced gluonic (inverse) catalysis and pressure (an)isotropy in QCD
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DOI：
10.1007/jhep04(2013)130
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发表时间：
2013-03
影响因子：
5.4
通讯作者：
Gunnar S. Bali;F. Bruckmann;G. Endrődi;F. Gruber;A. Schäfer
中科院分区：
文献类型：
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作者：
Gunnar S. Bali;F. Bruckmann;G. Endrődi;F. Gruber;A. Schäfer
我们研究了强外磁场对零和非零温度下QCD真空中胶子和费米子观测值的影响，通过N f= 1+ 1+ 1物理质量的交错夸克的晶格模拟。发现胶子作用密度在低温时发生磁催化，在接近和高于转变温度时发生反磁催化，类似于夸克凝聚。此外，胶子作用呈现出各向异性：平行于外场的色磁场增强，而该方向的色电场被抑制。我们证明了使用欧拉-海森堡有效作用得到了相同的层次。相反，拓扑电荷密度相关器不显示出显著的各向异性直至磁场eB≈1 GeV 2。此外，我们证明了即使在非零磁场下，如果通过在固定外场下对系统进行压缩来定义压力，则压力仍然是各向同性的。相反，如果在压缩过程中场的通量保持固定（这是在晶格模拟中实现的情况），则压力发展为各向异性。我们估计了夸克和胶子对这种各向异性的贡献，并将它们与QCD真空的磁化强度联系起来。在进行电荷重整化后，我们得到了磁化强度的估计，表明QCD是顺磁性的。
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.