# A Perturbative RS I Cosmological Phase Transition

## TL;DR

This paper explores a class of Randall-Sundrum models with a first order cosmological phase transition, analyzing their phenomenology and demonstrating a successful transition with a TeV-Planck hierarchy and a perturbative regime.

## Contribution

It introduces a specific class of soft-wall Randall-Sundrum models that realize a successful first order cosmological phase transition with a naturally light radion/dilaton.

## Key findings

- Successful first order phase transition in the models.
- Realization of a TeV-Planck hierarchy.
- Perturbative regime with N approximately 20.

## Abstract

We identify a class of Randall-Sundrum type models with a successful first order cosmological phase transition during which a 5D dual of approximate conformal symmetry is spontaneously broken. Our focus is on soft-wall models that naturally realize a light radion/dilaton and suppressed dynamical contribution to the cosmological constant. We discuss phenomenology of the phase transition after developing a theoretical and numerical analysis of these models both at zero and finite temperature. We demonstrate a model with a TeV-Planck hierarchy and with a successful cosmological phase transition where the UV value of the curvature corresponds, via AdS/CFT, to an $N$ of $20$, where 5D gravity is expected to be firmly in the perturbative regime.