Spectral Functions from the Functional Renormalization Group

TL;DR

This paper develops a method within the Functional Renormalization Group framework to compute in-medium spectral functions, revealing chiral symmetry restoration effects and meson spectral behavior at finite temperature and density.

Contribution

It introduces a novel analytic continuation technique for spectral functions directly on the flow equations within the FRG framework, applied to quark-meson and gauged linear sigma models.

Findings

Spectral functions become degenerate at high temperatures due to chiral symmetry restoration.

The method successfully computes vector and axial-vector meson spectral functions.

Results show the behavior of pole masses and spectral degeneracy of mesons.

Abstract

We present results for in-medium spectral functions obtained within the Functional Renormalization Group framework. The analytic continuation from imaginary to real time is performed in a well-defined way on the level of the flow equations. Based on this recently developed method, results for the sigma and the pion spectral function for the quark-meson model are shown at finite temperature, finite quark-chemical potential and finite spatial momentum. It is shown how these spectral function become degenreate at high temperatures due to the restoration of chiral symmetry. In addition, results for vector- and axial-vector meson spectral functions are shown using a gauged linear sigma model with quarks. The degeneration of the $\rho$ and the $a_1$ spectral function as well as the behavior of their pole masses is discussed.