Primordial Black Holes and Gravitational Waves in Extensions of the Standard Model

TL;DR

This paper explores how extensions of the Standard Model with additional scalar fields and gauge symmetries can lead to strong phase transitions, gravitational waves, and primordial black holes, with potential detectability in future experiments.

Contribution

It demonstrates that specific Standard Model extensions can produce observable gravitational waves and primordial black holes from early universe phase transitions.

Findings

Strong first-order phase transitions are possible in the model.

Generated gravitational waves could be detected by upcoming experiments.

Primordial black holes may form during high-scale transitions.

Abstract

We investigate the phenomenology of a Standard Model extension incorporating an inert scalar doublet and a gauged $U(1)_{B-L}$ symmetry. Our analysis reveals regions of the parameter space that support strong first-order phase transitions, including cases featuring two successive transitions. Each transition can generate a stochastic gravitational wave background within the sensitivity reach of upcoming experiments. Remarkably, the high-scale transition may also produce primordial black holes with appreciable abundance.