Probing multi-step electroweak phase transition with multi-peaked primordial gravitational waves spectra

TL;DR

This paper investigates how multi-peaked primordial gravitational wave spectra can reveal details about sequential electroweak phase transitions in the early Universe, especially in multi-scalar models, and assesses their detectability.

Contribution

It identifies and analyzes the emergence of multi-peaked gravitational wave spectra from sequential phase transitions in a simple extended Higgs model.

Findings

Multi-peaked spectra are linked to sequential phase transitions.

Sequential transitions can produce distinguishable gravitational wave signatures.

Potential detectability by future gravitational-wave interferometers.

Abstract

Multi-peaked spectra of the primordial gravitational waves are considered as a phenomenologically relevant source of information about the dynamics of sequential phase transitions in the early Universe. In particular, such signatures trace back to specific patterns of the first-order electroweak phase transition in the early Universe occurring in multiple steps. Such phenomena appear to be rather generic in multi-scalar extensions of the Standard Model. In a particularly simple extension of the Higgs sector, we have identified and studied the emergence of sequential long- and short-lasting transitions as well as their fundamental role in generation of multi-peaked structures in the primordial gravitational-wave spectrum. We discuss the potential detectability of these signatures by the proposed gravitational-wave interferometers.