Conformal Phase Transitions at Weak and Strong Coupling

TL;DR

This paper investigates a phase transition in a supersymmetric gauge theory with defect fermions, using holographic methods to analyze the transition from a conformal phase to a massive phase at strong coupling.

Contribution

It provides a holographic analysis of a BKT-type phase transition in a defect gauge theory, including meson spectra and phase diagram at finite temperature and chemical potential.

Findings

Identification of a BKT-type phase transition at a critical coupling.

Calculation of meson masses across the phase transition.

Mapping of the phase diagram with temperature and chemical potential.

Abstract

D3 and D7-branes intersecting in 2+1 dimensions give rise at low energies to N=4 supersymmetric Yang-Mills theory coupled to defect fermions in the fundamental representation. This theory undergoes a BKT-type phase transition from a conformal phase to one in which the fermions acquire a non-zero mass when the 't Hooft coupling of the N=4 SYM exceeds a critical value. To study this transition, we continue the parameters of the model to a regime where a gravitational description is valid. We use it to calculate the masses of mesons and the phase diagram as a function of temperature and chemical potential. We also comment on the relation of our discussion to the transition from the non-abelian Coulomb phase to a confining one believed to occur in QCD at a critical number of flavors.