Fermion spectral function in hot strongly interacting matter from the functional renormalization group

TL;DR

This paper calculates the fermion spectral function at finite temperature using the functional renormalization group in a quark-meson model, revealing multi-peak structures and a temperature-dependent soft-mode.

Contribution

First calculation of fermion spectral function at finite temperature in a quark-meson model using FRG with self-consistent truncation.

Findings

Multi-peak structure indicating Landau damping

Identification of a fermion soft-mode approaching zero as temperature increases

Comparison of two truncation methods showing different spectral features

Abstract

We present the first calculation of fermion spectral function at finite temperature in quark-meson model in the framework of the functional renormalization group (FRG). We compare the results in two truncations, after first evolving flow equation of effective potential, we investigate the spectral function either by taking the IR values as input to calculate one-loop self-energy or by taking the scale-dependent values as input to evolve the flow equation of the fermion two-point function. The latter one is a self-consistent procedure in the framework of FRG. In both truncations, we find a multi-peak structure in the spectral function, indicating quark collective excitations realized in terms of the Landau damping. However, in contrast to fermion zero-mode in the one-loop truncation, we find a fermion soft-mode in the self-consistent truncation, which approaches the zero-mode as temperature increases.