球对称时空中的剪切粘性、弛豫和碰撞时间
Shear viscosity, relaxation and collision times in spherically symmetric spacetimes
摘要：
我们解释为剪切粘度的各向异性压力，出现在不均匀的球对称时空所描述的勒梅特-托尔曼-邦迪（LTB）度规在一个共同的框架。通过假设局部各向同性压力和能量密度满足一般的理想气体状态方程，我们将场方程简化为一组基于辅助准局部变量的演化方程。我们研究了从扩展的不可逆热力学的剪切粘度的传输方程，并使用数值解的演化方程，以获得完整的和“截断”的版本的弛豫时间。考虑到气体的冷暗物质WIMPS后，从宇宙流体解耦，我们表明，一般方程的弛豫时间定性类似于碰撞时间，而截断的版本是不足以描述过渡到平衡的瞬态现象。
英文摘要：
We interpret as shear viscosity the anisotropic pressure that emerges in inhomogeneous spherically symmetric spacetimes described by the Lemaitre-Tolman-Bondi (LTB) metric in a comoving frame. By assuming that local isotropic pressure and energy density satisfy a generic ideal gas equation of state, we reduce the field equations to a set of evolution equations based on auxiliary quasi-local variables. We examine the transport equation of shear viscosity from Extended Irreversible Thermodynamics and use a numerical solution of the evolution equations to obtain the relaxation times for the full and "truncated" versions. Considering a gas of cold dark matter WIMPS after its decoupling from the cosmic fluid, we show that the relaxation times for the general equation are qualitatively analogous to collision times, while the truncated version is inadequate to describe transient phenomena of transition to equilibrium.
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