External Fields and Chiral Symmetry Breaking in the Sakai-Sugimoto Model

TL;DR

This paper uses the Sakai-Sugimoto holographic model to explore how external magnetic fields influence chiral symmetry breaking and phase transitions in a large N_c gauge theory, revealing magnetic catalysis and complex phase behavior.

Contribution

It demonstrates that external magnetic fields promote chiral symmetry breaking and alter the phase diagram, including the existence of a maximum critical temperature at high magnetic fields, extending previous holographic studies.

Findings

Magnetic field promotes chiral symmetry breaking.

External field increases the separation between deconfinement and chiral restoration temperatures.

Existence of a maximum critical temperature at high magnetic fields.

Abstract

Using the Sakai-Sugimoto model we study the effect of an external magnetic field on the dynamics of fundamental flavours in both the confined and deconfined phases of a large N_c gauge theory. We find that an external magnetic field promotes chiral symmetry breaking, consistent with the "magnetic catalysis" observed in the field theory literature, and seen in other studies using holographic duals. The external field increases the separation between the deconfinement temperature and the chiral symmetry restoring temperature. In the deconfined phase we investigate the temperature-magnetic field phase diagram and observe, for example, there exists a maximum critical temperature (at which symmetry is restored) for very large magnetic field. We find that this and certain other phenomena persist for the Sakai-Sugimoto type models with probe branes of diverse dimensions. We comment briefly on the dynamics in the presence of an external electric field.