Spectral Functions in V-QCD with Matter: Masses, Susceptibilities, Diffusion and Conductivity

TL;DR

This paper uses a holographic V-QCD model to analyze spectral functions, masses, susceptibilities, diffusion, and conductivity across phase transitions in a large-Nc and Nf QCD-like theory.

Contribution

It provides a detailed holographic study of spectral functions and transport properties across deconfinement and chiral restoration transitions in V-QCD.

Findings

Pole masses survive deconfinement but dissolve in chiral restoration phase.

Flavor electric conductivities sharply increase at the transition.

Flavor susceptibility aligns with bulk thermodynamics predictions.

Abstract

We consider a holographic model of QCD in the Veneziano limit of a large number of colors $N_c$ and flavors $N_f$ but fixed $x=N_f/N_c$ (V-QCD). The model exhibits a first order deconfined but chirally broken transition, followed by a second order chirally restored transition in the $\mu-T$ plane for a range of plausible holographic parameters. We study the quasi-normal mode spectrum, and derive the pertinent vector and axial spectral functions across the transition regions. The pole masses, susceptibilities, diffusion constants and electric conductivity are also discussed. In particular, the pole masses are found to survive the deconfining transition, to quickly dissolve in the the chirally restored phase by developing substantial widths. The flavor electric conductivities arise sharply in the transition region. The flavor susceptibility is shown to be consistent with the one derived from bulk thermodynamics.