We show that the widely used relaxation time approximation to the relativistic Boltzmann equation contains basic flaws, being incompatible with micro- and macroscopic conservation laws if the relaxation time depends on energy or general matching conditions are applied. We propose a new approximation that fixes such fundamental issues and maintains the basic properties of the linearized Boltzmann collision operator. We show how this correction affects transport coefficients, such as the bulk viscosity and particle diffusion.

中文翻译：

---

相对论玻尔兹曼方程的新松弛时间近似

我们表明，广泛使用的相对论玻尔兹曼方程的弛豫时间近似包含基本缺陷，如果弛豫时间取决于能量或应用一般匹配条件，则与微观和宏观守恒定律不兼容。我们提出了一种新的近似方法，可以解决这些基本问题并保持线性化玻尔兹曼碰撞算子的基本属性。我们展示了这种校正如何影响传输系数，例如体积粘度和粒子扩散。