Holographic vector mesons from spectral functions at finite baryon or isospin density

TL;DR

This paper uses gauge/gravity duality to analyze spectral functions of vector mesons at finite baryon and isospin densities, revealing meson mass spectra, phase transitions, and isospin splitting effects.

Contribution

It provides a detailed holographic analysis of vector meson spectral functions at finite density, including meson mass behavior, phase transition characteristics, and isospin effects.

Findings

Resonance frequencies have a minimum at a finite quark mass.

Peaks move to larger frequencies and narrow with increasing quark mass/temperature ratio.

Spectral functions show resonance peak splitting under isospin chemical potential.

Abstract

We consider gauge/gravity duality with flavor for the finite-temperature field theory dual of the AdS-Schwarzschild black hole background with embedded D7-brane probes. In particular, we investigate spectral functions at finite baryon density in the black hole phase. We determine the resonance frequencies corresponding to meson-mass peaks as function of the quark mass over temperature ratio. We find that these frequencies have a minimum for a finite value of the quark mass. If the quotient of quark mass and temperature is increased further, the peaks move to larger frequencies. At the same time the peaks narrow, in agreement with the formation of nearly stable vector meson states which exactly reproduce the meson mass spectrum found at zero temperature. We also calculate the diffusion coefficient, which has finite value for all quark mass to temperature ratios, and exhibits a first-order phase transition. Finally we consider an isospin chemical potential and find that the spectral functions display a resonance peak splitting, similar to the isospin meson mass splitting observed in effective QCD models.