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Far-from-equilibrium kinetic dynamics ofλϕ4theory in an expanding universe
Physical Review D ( IF 5 ) Pub Date : 2022-09-27 , DOI: 10.1103/physrevd.106.056024
Nicki Mullins, Gabriel S. Denicol, Jorge Noronha

We investigate the far-from-equilibrium behavior of the Boltzmann equation for a gas of massless scalar field particles with quartic (tree level) self-interactions (λϕ4) in Friedmann-Lemaitre-Robertson-Walker spacetime. Using a new covariant generating function for the moments of the Boltzmann distribution function, we analytically determine a subset of the spectrum and the corresponding eigenfunctions of the linearized Boltzmann collision operator. We show how the covariant generating function can be also used to find the exact equations for the moments in the full nonlinear regime. Different than the case of a ultrarelativistic gas of hard spheres (where the total cross section is constant), for λϕ4 the fact that the cross section decreases with energy implies that moments of arbitrarily high order directly couple to low order moments. Numerical solutions for the scalar field case are presented and compared to those found for a gas of hard spheres.

中文翻译:

膨胀宇宙中λφ4理论的远非平衡动力学

我们研究了具有四次(树级)自相互作用的无质量标量场粒子气体的玻尔兹曼方程的远离平衡行为(λφ4) 在弗里德曼-勒梅特-罗伯逊-沃克时空。使用玻尔兹曼分布函数矩的新协变生成函数,我们分析确定了谱的子集和线性化玻尔兹曼碰撞算子的相应特征函数。我们展示了如何使用协变生成函数来找到完全非线性状态下矩的精确方程。与硬球体的超相对论气体的情况不同(其中总横截面是恒定的),对于λφ4横截面随能量减小的事实意味着任意高阶矩直接耦合到低阶矩。给出了标量场情况的数值解,并将其与硬球气体的数值解进行了比较。
更新日期:2022-09-27
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