Light holographic dilatons near critical points

TL;DR

This paper explores how light dilaton particles emerge near critical points in holographic models of strongly coupled field theories, linking phase transitions and bound state spectra.

Contribution

It demonstrates the connection between dilaton emergence and critical phenomena in two classes of holographic models, including the calculation of fluctuation spectra near phase transitions.

Findings

Identification of a parametrically light scalar as a dilaton near second-order phase transitions.

Existence of a critical line of first-order phase transitions terminating at a critical point.

Correlation between complex fixed points, instabilities, and dilaton emergence.

Abstract

We investigate the relation between the emergence of a dilaton in gapped (confining) field theories, and the presence of either complex fixed points or instabilities in the strongly coupled dynamics in two classes of bottom-up holographic models. We demonstrate that in one of the two classes there is a critical line of first-order phase transitions (at zero temperature) that terminates at a critical point. We calculate the mass spectrum of fluctuations of the associated regular gravity backgrounds, which we interpret as bound states in the dual field theories. In proximity to the second-order phase transition, we find a parametrically light scalar state, and its composition leads us to identify it as a dilaton.