Coexisting vacua and effective gravity

TL;DR

This paper explores the concept of multiple coexisting vacua in the universe, examining how phase boundaries and fermionic charges could regulate their coexistence and influence the structure of spacetime.

Contribution

It proposes mechanisms involving fermionic charges and zero modes for the coexistence of different quantum vacua across phase boundaries.

Findings

Coexisting vacua can be stabilized by fermionic charge exchange.

Phase boundaries may host fermion zero modes affecting vacuum stability.

Examples include a de-Sitter universe within flat spacetime.

Abstract

Our Universe may be a domain separated by physical phase boundaries from other domain-Universes with different vacuum energy density and matter content. The coexistence of different quantum vacua is perhaps regulated by the exchange of global fermionic charges or by fermion zero modes on the phase boundary. An example would be a static de-Sitter Universe embedded in an asymptotically flat spacetime.