论文标题
基准测试宇宙主方程
Benchmarking the cosmological master equations
论文作者
论文摘要
主方程通常用于宇宙学中，以模拟额外的自由度的影响，即“环境”，对给定的“系统”。但是，它们依赖于在宇宙学中不一定满足的假设，在宇宙学中，环境可能不足，背景是动态的。在这项工作中，我们将主方程式程序应用于完全可以解决的模型，该模型由两个线性耦合的标量字段组成，这些标量字段在宇宙学背景下演变。光场扮演系统的角色，重场是环境。通过将精确解决方案与主方程的输出进行比较，我们可以批判性地评估其性能。我们发现主方程表现出一组“虚假”术语，这些术语明确取决于初始条件，并且由于在动态背景上工作而产生的术语。尽管它们以理论的扰动限制取消（即，在互动强度的领先命令下），但它们会破坏重新召集。但是，当删除这些术语时，主方程式表现出色，可以重现功率谱和光场的折叠量，即使在强烈的校正状态下也是如此。我们得出的结论是，即使系统远非马尔可夫限制，主人方程式也能够执行延迟重新调整，但如果削弱了伪造的贡献。
Master equations are commonly employed in cosmology to model the effect of additional degrees of freedom, treated as an "environment", onto a given "system". However, they rely on assumptions that are not necessarily satisfied in cosmology, where the environment may be out of equilibrium and the background is dynamical. In this work, we apply the master-equation program to a model that is exactly solvable, and which consists of two linearly coupled scalar fields evolving on a cosmological background. The light field plays the role of the system and the heavy field is the environment. By comparing the exact solution to the output of the master equation, we can critically assess its performance. We find that the master equation exhibits a set of "spurious" terms that explicitly depend on the initial conditions, and which arise as a consequence of working on a dynamical background. Although they cancel out in the perturbative limit of the theory (i.e. at leading orders in the interaction strength), they spoil resummation. However, when those terms are removed, the master equation performs impressively well to reproduce the power spectra and the amount of the decoherence of the light field, even in the strongly decohered regime. We conclude that master equations are able to perform late-time resummation, even though the system is far from the Markovian limit, provided spurious contributions are suppressed.
