Spectral function and quasi-particle damping of interacting bosons in two dimensions

TL;DR

This paper uses the functional renormalization group to analyze the spectral properties and damping of quasi-particles in a two-dimensional interacting Bose gas, overcoming infrared divergence issues and aligning with exact identities.

Contribution

It introduces a divergence-free RG approach that accurately captures the infrared behavior and spectral features of 2D Bose gases, consistent with the Nepomnyashchy identity.

Findings

Correct infrared behavior of propagators recovered

Explicit spectral line-shape results obtained

Quasi-particle dispersion and damping characterized

Abstract

We employ the functional renormalization group to study dynamical properties of the two-dimensional Bose gas. Our approach is free of infrared divergences, which plague the usual diagrammatic approaches, and is consistent with the exact Nepomnyashchy identity, which states that the anomalous self-energy vanishes at zero frequency and momentum. We recover the correct infrared behavior of the propagators and present explicit results for the spectral line-shape, from which we extract the quasi-particle dispersion and damping.