Boltzmann方程Gubser解的有效域研究
Investigating the domain of validity of the Gubser solution to the Boltzmann equation
摘要：
我们研究了一个粒子分布函数的演化，它精确地解决了在弛豫时间近似下的相对论性玻尔兹曼方程，同时进行方位对称的横向和助推不变的纵向膨胀的共形系统。我们表明，对于任意值的剪切粘度熵密度比，分布函数可以成为负的在某些运动区域的可用相空间取决于边界条件。对于热平衡初始条件，我们数值确定了相空间中的物理边界，其中分布函数总是正定的。这个特定的精确解的正性的要求限制了它的有效域，它对它的适用性施加了物理约束。
英文摘要：
We study the evolution of the one particle distribution function that solves exactly the relativistic Boltzmann equation within the relaxation time approximation for a conformal system undergoing simultaneously azimuthally symmetric transverse and boost-invariant longitudinal expansion. We show, for arbitrary values of the shear viscosity to entropy density ratio, that the distribution function can become negative in certain kinematic regions of the available phase space depending on the boundary conditions. For thermal equilibrium initial conditions, we determine numerically the physical boundary in phase space where the distribution function is always positive definite. The requirement of positivity of this particular exact solution restricts its domain of validity, and it imposes physical constraints on its applicability.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
