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arXiv 0902.1611hep-thcond-mat.otherhep-latphysics.flu-dyn
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随机搅拌流的规范固定、BRS不变性和沃德恒等式

Gauge fixing, BRS invariance and Ward identities for randomly stirred flows

Arjun Berera, David Hochberg

摘要:

纳维-斯托克斯方程的伽利略不变性被证明类似于量子场论中常见的全局规范对称性。这种对称性导致了在随机搅拌流体的路径积分方法中无限多个惯性参考系的多重计数。这个问题通过固定量规来解决,即,挑出一个参考系。规范固定理论有一个潜在的BRS对称性,它导致了与精确逆响应和顶点函数相关的沃德恒等式。伽利略不变性作为一个规范对称性的识别进行了详细的探讨,为不同的规范选择,并进行严格的审查的离散化版本的理论。纳维-斯托克斯方程在任意直线坐标系加速度下也是不变的,称为扩展伽利略不变性(EGI)。我们规范固定这种扩展的对称性,并推导出广义沃德恒等式,遵循规范固定理论的BRS不变性。这个新的沃德恒等式在零加速度极限下简化为标准恒等式。这种规范固定的方法明确地表明,伽利略不变性和EGI约束只有零模式的顶点,但没有更高的波数模式。

英文摘要:

The Galilean invariance of the Navier-Stokes equation is shown to be akin to a global gauge symmetry familiar from quantum field theory. This symmetry leads to a multiple counting of infinitely many inertial reference frames in the path integral approach to randomly stirred fluids. This problem is solved by fixing the gauge, i.e., singling out one reference frame. The gauge fixed theory has an underlying Becchi-Rouet-Stora (BRS) symmetry which leads to the Ward identity relating the exact inverse response and vertex functions. This identification of Galilean invariance as a gauge symmetry is explored in detail, for different gauge choices and by performing a rigorous examination of a discretized version of the theory. The Navier-Stokes equation is also invariant under arbitrary rectilinear frame accelerations, known as extended Galilean invariance (EGI). We gauge fix this extended symmetry and derive the generalized Ward identity that follows from the BRS invariance of the gauge-fixed theory. This new Ward identity reduces to the standard one in the limit of zero acceleration. This gauge-fixing approach unambiguously shows that Galilean invariance and EGI constrain only the zero mode of the vertex but none of the higher wavenumber modes.

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