Fluctuating vector mesons in analytically continued FRG flow equations

TL;DR

This paper investigates how vector and axial-vector meson fluctuations affect their spectral functions in hot and dense matter using analytically continued FRG equations, providing insights into QCD phase transitions.

Contribution

It introduces a method to incorporate vector meson fluctuations into the FRG framework and computes their spectral functions at finite temperature and density.

Findings

Vector meson fluctuations significantly influence spectral functions.

New contributions identified in the spectral functions due to meson fluctuations.

Implications for signals of QCD critical endpoint and chiral symmetry restoration.

Abstract

In this work we study contributions due to vector and axial-vector meson fluctuations to their in-medium spectral functions in an effective low-energy theory inspired by the gauged linear sigma model. In particular, we show how to describe these fluctuations in the effective theory by massive (axial-)vector fields in agreement with the known structure of analogous single-particle or resonance contributions to the corresponding conserved currents. The vector and axial-vector meson spectral functions are then computed by numerically solving the analytically continued functional renormalization group (aFRG) flow equations for their retarded two-point functions at finite temperature and density in the effective theory. We identify the new contributions that arise due to the (axial-)vector meson fluctuations, and assess their influence on possible signatures of a QCD critical endpoint and the restoration of chiral symmetry in thermal dilepton spectra.