Gravitational waves from a holographic phase transition

TL;DR

This paper models first order phase transitions in a holographic five-dimensional gravity setup, analyzing their characteristics and potential gravitational wave signals detectable by future space-based observatories.

Contribution

It constructs phase diagrams and maps key quantities of holographic phase transitions, linking theoretical parameters to observable gravitational wave signals.

Findings

First order phase transitions occur in specific parameter regions.

The transition strength parameter $\alpha$ ranges from 0.1 to 0.3.

Potential detectability of gravitational waves from TeV-scale hidden sector phase transitions at LISA and TianQin.

Abstract

We investigate first order phase transitions in a holographic setting of five-dimensional Einstein gravity coupled to a scalar field, constructing phase diagrams of the dual field theory at finite temperature. We scan over the two-dimensional parameter space of a simple bottom-up model and map out important quantities for the phase transition: the region where first order phase transitions take place; the latent heat, the transition strength parameter $\alpha$, and the stiffness. We find that $\alpha$ is generically in the range 0.1 to 0.3, and is strongly correlated with the stiffness (the square of the sound speed in a barotropic fluid). Using the LISA Cosmology Working Group gravitational wave power spectrum model corrected for kinetic energy suppression at large $\alpha$ and non-conformal stiffness, we outline the observational prospects at the future space-based detectors LISA and TianQin. A TeV-scale hidden sector with a phase transition described by the model could be observable at both detectors.