大Nc等价与有限重子密度下的符号问题
Large-Nc equivalence and the sign problem at finite baryon density
摘要：
具有有限重子化学势的QCD，尽管其重要性，但由于标准的格点量子色动力学模拟由于符号问题而不适用，因此没有得到很好的理解。虽然不受符号问题困扰的类QCD理论已经得到了深入的研究，但与有限重子化学势下的QCD的关系还不清楚。本文介绍了QCD与各种类QCD理论之间的大$N_c$等价性。这些等价性使我们对重子和同位旋化学势QCD、$SO(2N_c)$和$Sp(2N_c)$规范理论、伴随物质QCD和双色QCD有了统一的认识。特别是具有重子化学势的QCD是大的--在一定的参数范围内$N_c$等价于它的相位猝灭形式，这与重离子碰撞实验有关。所有先前研究相位效应的模拟结果证实，相位猝灭近似在Nc=3时已经定量良好;它是如此之好，以至于通常两个理论在误差范围内给出相同的值。因此，相位猝灭模拟是QCD临界点搜索的最佳策略。在小体积下，可以通过相位重新加权来研究微小的1/Nc效应;大Nc等效性保证了相位重新加权方法在不遭受重叠问题的情况下工作。
英文摘要：
QCD with a finite baryon chemical potential, despite its importance, is not well understood because the standard lattice QCD simulation is not applicable due to the sign problem. Although QCD-like theories which do not suffer from the sign problem have been studied intensively, relation to QCD with a finite baryon chemical potential was not clear. This paper introduces large-$N_c$ equivalences between QCD and various QCD-like theories. These equivalences lead us to a unified viewpoint for QCD with baryon and isospin chemical potentials, $SO(2N_c)$ and $Sp(2N_c)$ gauge theories, QCD with adjoint matters and two-color QCD. In particular QCD with the baryon chemical potential is large-$N_c$ equivalent to its phase quenched version in a certain parameter region, which is relevant for heavy ion collision experiments. All previous simulation results which study the effect of the phase confirm the phase quench approximation is quantitatively good already at Nc=3; it is so good that often two theories give the same value within error. Therefore the phase quenched simulation is the best strategy for the QCD critical point search. At small volume one can study a tiny 1/Nc effect by the phase reweighting; the large-Nc equivalence guarantees that the phase reweighing method works without suffering from the overlapping problem.
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。
