标题： 磁场背景下的有限密度QCD相变 显示英文标题

标题： Finite-density QCD transition in magnetic field background

摘要： 使用具有物理夸克质量的格点QCD数值模拟，我们揭示了磁场背景对有限温度QCD中手征和禁闭交叉的影响，在低重子密度下。在没有热力学奇点的情况下，我们将这些转变与近似序参数的拐点相对应：归一化的轻夸克凝聚和重整化的Polyakov环。我们表明，在“温度-化学势”平面上，手征转变温度的二次曲率对背景磁场强度的依赖性较弱。在弱磁场下，手征交叉的热宽度随着重子物质密度的增加而变窄，这可能表明接近真实的热力学相变。值得注意的是，在$eB_{\mathrm{fl}} \simeq 0.6\,\mathrm{GeV}^2$处，手征热宽度的曲率改变了符号，因此在翻转点$B > B_{\mathrm{fl}}$以上，随着重子密度的增加，手征宽度变得更宽。大约在同一强度的磁场下，手征和禁闭交叉在$T \approx 140\,\mathrm{MeV}$处合并在一起。概述了“温度-化学势-磁场”参数空间中的相图，并探讨了单个夸克的熵和单个夸克的磁化率。手征热宽度的曲率使我们能够估计零磁场下手征临界端点的大致位置：$(T_c^{\text{CEP}}, \mu_B^{\text{CEP}})= (100(25)\, \text{MeV},\ 800(140)\,\text{MeV})$。 显示英文摘要

摘要： Using numerical simulations of lattice QCD with physical quark masses, we reveal the influence of magnetic-field background on chiral and deconfinement crossovers in finite-temperature QCD at low baryonic density. In the absence of thermodynamic singularity, we identify these transitions with inflection points of the approximate order parameters: normalized light-quark condensate and renormalized Polyakov loop, respectively. We show that the quadratic curvature of the chiral transition temperature in the ``temperature--chemical potential'' plane depends rather weakly on the strength of the background magnetic field. At weak magnetic fields, the thermal width of the chiral crossover gets narrower as the density of the baryon matter increases, possibly indicating a proximity to a real thermodynamic phase transition. Remarkably, the curvature of the chiral thermal width flips its sign at $eB_{\mathrm{fl}} \simeq 0.6\,\mathrm{GeV}^2$, so that above the flipping point $B > B_{\mathrm{fl}}$, the chiral width gets wider as the baryon density increases. Approximately at the same strength of magnetic field, the chiral and deconfining crossovers merge together at $T \approx 140\,\mathrm{MeV}$. The phase diagram in the parameter space ``temperature-chemical potential-magnetic field'' is outlined, and single-quark entropy and single-quark magnetization are explored. The curvature of the chiral thermal width allows us to estimate an approximate position of the chiral critical endpoint at zero magnetic field: $(T_c^{\text{CEP}}, \mu_B^{\text{CEP}})= (100(25)\, \text{MeV},\ 800(140)\,\text{MeV})$.