ABSTRACT: Master equations are an excellent tool for understanding the behavior of quantum systems coupled to thermal baths, but they have their limitations. Real systems coupled to thermalizing many-body systems do not necessarily follow the simple dynamics of master equations. Here I will discuss a number of facts and questions about the behavior of open quantum systems beyond master equations, some of them based on recent work and some on work currently in progress. Among other things, I will discuss the relationship between Fermi's golden rule, the oscillator bath, and random matrix models, master equations for time-dependent systems, and the use of MPS methods for exact simulations of systems coupled to an oscillator bath.
TITLE: Exploring open quantum systems beyond master equations