# Cosmological first-order phase transitions beyond the standard inflationary scenario

## TL;DR

This paper investigates how non-standard cosmological backgrounds influence the nucleation and evolution of vacuum bubbles during first-order phase transitions, revealing significant effects on tunneling rates and bubble dynamics.

## Contribution

It introduces a detailed analysis of vacuum bubble behavior beyond standard inflation, using complex time methods and various matter models, highlighting the impact of ambient matter on bubble evolution.

## Key findings

- Tunneling rates are significantly affected by dynamical FRW backgrounds.
- Bubble inflation is highly sensitive to ambient matter presence.
- Potential observable imprints depend on inhomogeneous matter models.

## Abstract

Motivated by cosmological first-order phase transitions we examine the nucleation and evolution of vacuum bubbles in non-vacuum environments. Non-standard backgrounds can be relevant in the context of rapid tunneling processes on the landscape. Utilising complex time methods, we show that tunneling rates can be notably modified in the case of dynamical FRW backgrounds. We give a classification of the importance of the effect in terms of the relevant dynamical time scales. For both the bubble nucleation and evolution analysis we make use of the thin-wall approximation. From the classical bubble evolution on homogeneous matter backgrounds via the junction method, we find that the inflation of vacuum bubbles is very sensitive to the presence of ambient matter and quantify this statement. We also employ inhomogeneous matter models (LTB) and models that undergo a rapid phase transition (FRW) as a background and discuss in which cases potentially observable imprints on the bubble trajectory can remain.