# Phase transition and gravitational wave phenomenology of scalar conformal extensions of the Standard Model

## TL;DR

This paper studies how scalar conformal extensions of the Standard Model can produce strong first-order phase transitions and detectable gravitational wave signals, emphasizing the importance of model complexity.

## Contribution

It analyzes phase transition dynamics and gravitational wave signals in scalar conformal extensions, highlighting the limitations of minimal models and the potential of next-to-minimal models.

## Key findings

- Minimal models struggle with phase transition dynamics due to thermal corrections.
- Next-to-minimal models achieve correct electroweak symmetry breaking.
- Next-to-minimal models predict strong gravitational wave signals.

## Abstract

Thermal corrections in classically conformal models typically induce a strong first-order electroweak phase transition, thereby resulting in a stochastic gravitational wave background that could be detectable at gravitational wave observatories. After reviewing the basics of classically conformal scenarios, in this paper we investigate the phase transition dynamics in a thermal environment and the related gravitational wave phenomenology within the framework of scalar conformal extensions of the Standard Model. We find that minimal extensions involving only one additional scalar field struggle to reproduce the correct phase transition dynamics once thermal corrections are accounted for. Next-to-minimal models, instead, yield the desired electroweak symmetry breaking and typically result in a very strong gravitational wave signal.