# Searches for other vacua I: bubbles in our universe

## TL;DR

This paper explores models where lower-energy vacua are confined to finite regions in our universe, such as bubbles formed after supernovae, which could produce observable signatures unlike traditional expanding vacuum bubbles.

## Contribution

It introduces density-dependent vacuum models that allow for confined, non-expanding bubbles, providing a novel mechanism for observable vacuum phenomena in the present universe.

## Key findings

- Confined vacuum bubbles can form after supernovae.
- Such bubbles may produce detectable signals near supernova remnants.
- The models differ from standard vacuum tunneling by confinement and potential observability.

## Abstract

We discuss models in which vacua other than our own can be directly observed in the present universe. Models with density-dependent vacuum structure can give rise to `non-lethal'-vacua: vacua with lower energy-density than our vacuum, but only in regions with finite Standard Model densities. These models provide an explicit example of a bubble which is confined to a finite region of space and produces potentially detectable signatures, unlike standard Coleman tunneling events where bubbles expand at the speed of light and are never directly observable. We study the expansion and contraction of a confined bubble created after a core-collapse supernova, focusing on energy deposition that may be observable in the vicinity of a supernova remnant due to the formation and evolution of a confined bubble.