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arXiv 1404.6409hep-phhep-thnucl-th
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基于量子Dirac哈密顿量和在壳层有效场论的手征输运方程

Chiral transport equation from the quantum Dirac Hamiltonian and the on-shell effective field theory

Cristina Manuel, Juan M. Torres-Rincon

摘要:

通过对量子狄拉克哈密顿量进行半经典的Foldy-Wouthuysen对角化,导出了无质量费米子和反费米子的相对论手征输运方程。贝里连接自然出现在对角化过程中,以修改费米子在电磁场中的经典运动方程。我们还看到,费米子和反费米子色散关系在普朗克常量的一阶上被Berry曲率修正,正如Son和Yamamoto以前对消失温度的特殊情况导出的那样。我们的方法不需要知道系统的状态,因此它也可以在高温下应用。我们提供了支持我们的结果的另一种计算使用的有效场论的费米子和反费米子:壳层上的有效场论。在这种形式主义中,离壳费米子模式被整合出来,产生一个有效的拉格朗日准壳费米子/反费米子。首阶色散关系与半经典对角化结果完全一致。从输运方程,我们明确地表明,轴向和规范异常是如何不修改在有限的温度和密度,尽管纳入新的色散关系到分布函数。

英文摘要:

We derive the relativistic chiral transport equation for massless fermions and antifermions by performing a semiclassical Foldy-Wouthuysen diagonalization of the quantum Dirac Hamiltonian. The Berry connection naturally emerges in the diagonalization process to modify the classical equations of motion of a fermion in an electromagnetic field. We also see that the fermion and antifermion dispersion relations are corrected at first order in the Planck constant by the Berry curvature, as previously derived by Son and Yamamoto for the particular case of vanishing temperature. Our approach does not require knowledge of the state of the system, and thus it can also be applied at high temperature. We provide support for our result by an alternative computation using an effective field theory for fermions and antifermions: the on-shell effective field theory. In this formalism, the off-shell fermionic modes are integrated out to generate an effective Lagrangian for the quasi-on-shell fermions/antifermions. The dispersion relation at leading order exactly matches the result from the semiclassical diagonalization. From the transport equation, we explicitly show how the axial and gauge anomalies are not modified at finite temperature and density despite the incorporation of the new dispersion relation into the distribution function.

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