Hierarchy of double-time correlations

TL;DR

This paper extends the hierarchy of correlations method to double-time correlators, enabling the study of non-equilibrium phenomena, light cones, Green functions, and finite temperature effects in strongly interacting quantum many-body systems.

Contribution

The authors generalize the hierarchy of correlations to include double-time correlators, broadening its applicability to dynamic and thermal properties of quantum systems.

Findings

Enables analysis of effective light cones in quantum systems

Allows incorporation of finite initial temperatures

Provides a new tool for studying non-equilibrium dynamics

Abstract

The hierarchy of correlations is an analytical approximation method which allows us to study non-equilibrium phenomena in strongly interacting quantum many-body systems on lattices in higher dimensions. So far, this method was restricted to equal-time correlators $\langle\hat A_\mu(t)\hat B_\nu(t)\rangle$. In this work, we generalize this method to double-time correlators $\langle\hat A_\mu(t)\hat B_\nu(t')\rangle$, which allows us to study effective light cones and Green functions and to incorporate finite initial temperatures.