Spectral functions from the functional renormalization group at finite temperature and density

TL;DR

This paper introduces a non-perturbative functional renormalization group method to compute real-time spectral functions at finite temperature and density, demonstrated on the quark-meson model near the critical endpoint.

Contribution

A new thermodynamically consistent truncation scheme for flow equations enabling the calculation of spectral functions within the FRG framework at finite temperature and density.

Findings

Successfully computed mesonic spectral functions at various temperatures and chemical potentials.

Demonstrated the method's effectiveness near the critical endpoint in the phase diagram.

Provided a viable approach for real-time quantity calculations in non-perturbative regimes.

Abstract

We present a viable method to obtain real-time quantities such as spectral functions or transport coefficients at finite temperature and density within a non-perturbative Functional Renormalization Group approach. Our method is based on a thermodynamically consistent truncation of the flow equations for 2-point functions with analytically continued frequency components in the originally Euclidean external momenta. We demonstrate its feasibility by calculating the mesonic spectral functions in the quark-meson model at different temperatures and quark chemical potentials, in particular around the critical endpoint in the phase diagram of the model.