Inhomogeneous phases in the quark-meson model with vacuum fluctuations
Inhomogeneous phases in the quark-meson model with vacuum fluctuations
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DOI：
10.1103/physrevd.90.014033
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发表时间：
2014-03
影响因子：
5
通讯作者：
S. Carignano;M. Buballa;B. Schaefer
中科院分区：
文献类型：
--
作者：
S. Carignano;M. Buballa;B. Schaefer
在双味夸克-介子模型中，研究了非消失化学势和温度下的非均匀手性对称性破缺相。通过考虑到夸克的狄拉克-海贡献，在标准平均场近似之外进行了分析。与忽略狄拉克海的情况相比，我们发现非均匀相缩小了，但总体上没有消失。Ginzburg-Landau分析表明，如果选择真空中sigma-介子质量与组成夸克质量之比为$m_\sigma/M = 2$，则非均匀相的Lifshitz点与三临界点重合，对应于Nambu- Jona-Lasinio模型中的固定质量比。然而，在目前的模型中，这个比率可以改变，从而提供了将两点分开的可能性。我们的数值计算证实了这一点，表明$m_\sigma$对非均匀相的大小有很强的敏感性。最后，我们揭示了模型相对于手性调制的大波数的一般不稳定性，这需要在目前的近似基础上进一步改进。
Inhomogeneous chiral-symmetry breaking phases at non-vanishing chemical potential and temperature are studied within a two-flavor quark-meson model in the chiral limit. The analysis is performed beyond the standard mean-field approximation by taking into account the Dirac-sea contributions of the quarks. Compared with the case where the Dirac sea is neglected, we find that the inhomogeneous phase shrinks, but in general does not disappear. It is shown within a Ginzburg-Landau analysis that the Lifshitz point of the inhomogeneous phase coincides with the tricritical point if the ratio between sigma-meson and constituent quark mass in vacuum is chosen to be $m_\sigma/M = 2$, corresponding to the fixed mass ratio in the Nambu--Jona-Lasinio model. In the present model, however, this ratio can be varied, offering the possibility to separate the two points. This is confirmed by our numerical calculations, which demonstrate a strong sensitivity of the size of the inhomogeneous phase on $m_\sigma$. Finally, we uncover a general instability of the model with respect to large wave numbers of the chiral modulations, which calls for further improvements beyond the present approximation.