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arXiv 1303.3972hep-lathep-ph
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逆磁催化与Polyakov环

Inverse magnetic catalysis and the Polyakov loop

F. Bruckmann, G. Endrodi, T. G. Kovacs

摘要:

我们研究了外加磁场对QCD夸克凝聚影响的物理机制。两个竞争机制被确定,都依赖于磁场和低夸克模式之间的相互作用。在过渡区,与价夸克的耦合增强了凝聚,而与海夸克的相互作用抑制了凝聚。后一种“海洋效应”通过使波利亚科夫环有序化而起作用,从而减少了小狄拉克本征模和凝聚体的数量。它在转变温度附近是最有效的,其中波利雅科夫回路有效势是平坦的,并且通过磁场对其进行小的校正可以具有显著的效果。在临界温度附近,海的抑制作用抵消了价态的增强作用,导致凝聚态的净抑制,称为逆磁催化。我们支持这一物理图像的晶格模拟,包括连续外推的结果Polyakov环作为温度和磁场的函数。我们认为,考虑到增加的Polyakov环和它的相互作用与低的模式是必不可少的,以获得完整的物理图片,并应纳入有效的模型中描述的QCD在磁场的过渡区。

英文摘要:

We study the physical mechanism of how an external magnetic field influences the QCD quark condensate. Two competing mechanisms are identified, both relying on the interaction between the magnetic field and the low quark modes. While the coupling to valence quarks enhances the condensate, the interaction with sea quarks suppresses it in the transition region. The latter `sea effect' acts by ordering the Polyakov loop and, thereby, reduces the number of small Dirac eigenmodes and the condensate. It is most effective around the transition temperature, where the Polyakov loop effective potential is flat and a small correction to it by the magnetic field can have a significant effect. Around the critical temperature, the sea suppression overwhelms the valence enhancement, resulting in a net suppression of the condensate, named inverse magnetic catalysis. We support this physical picture by lattice simulations including continuum extrapolated results on the Polyakov loop as a function of temperature and magnetic field. We argue that taking into account the increase in the Polyakov loop and its interaction with the low-lying modes is essential to obtain the full physical picture, and should be incorporated in effective models for the description of QCD in magnetic fields in the transition region.

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