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arXiv 1202.0732hep-thgr-qc
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N维热平坦空间中应力-能量张量关联函数的广义Zeta函数方法

Stress-energy Tensor Correlators in N-dim Hot Flat Spaces via the Generalized Zeta-Function Method

H. T. Cho, B. L. Hu

摘要:

利用广义zeta函数方法计算了平坦$N$维时空中无质量最小耦合标量场关于有限温度量子态$T$的两个不同时空点$x, x'$上的应力-能量双张量的期望值.这些关联函数,也被称为噪声核,给出了量子场的能量和动量密度的涨落,这对于研究某些时空或量子态中的负能量密度的物理效应是必不可少的。它们也是随机引力中爱因斯坦-朗之万方程的来源,人们可以解决时空泡沫中的度量波动动力学。就构成而言,这些关联函数比驱动半经典引力中的半经典爱因斯坦方程的应力-能量张量的平均值(真空和热期望)高一级(在相关性- BBGKY或Schwinger-Dyson -层次的意义上)。在低温下,首阶温度依赖性类似于$T^{N}$,而在高温下,它们具有$T^{2}$依赖性,子首项被$e^{-T}$指数抑制。我们还讨论了在$x'\rightarrow x$重合极限下,无质量共形量子场的奇异行为。

英文摘要:

We calculate the expectation values of the stress-energy bitensor defined at two different spacetime points $x, x'$ of a massless, minimally coupled scalar field with respect to a quantum state at finite temperature $T$ in a flat $N$-dimensional spacetime by means of the generalized zeta-function method. These correlators, also known as the noise kernels, give the fluctuations of energy and momentum density of a quantum field which are essential for the investigation of the physical effects of negative energy density in certain spacetimes or quantum states. They also act as the sources of the Einstein-Langevin equations in stochastic gravity which one can solve for the dynamics of metric fluctuations as in spacetime foams. In terms of constitutions these correlators are one rung above (in the sense of the correlation -- BBGKY or Schwinger-Dyson -- hierarchies) the mean (vacuum and thermal expectation) values of the stress-energy tensor which drive the semiclassical Einstein equation in semiclassical gravity. The low and the high temperature expansions of these correlators are also given here: At low temperatures, the leading order temperature dependence goes like $T^{N}$ while at high temperatures they have a $T^{2}$ dependence with the subleading terms exponentially suppressed by $e^{-T}$. We also discuss the singular behaviors of the correlators in the $x'\rightarrow x$ coincident limit as was done before for massless conformal quantum fields.

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