Instability of (1+1) de sitter space in the presence of interacting fields

TL;DR

This paper investigates the stability of (1+1) de Sitter space with interacting fields, finding that fermionic interactions are stable while bosonic sine-Gordon interactions cause symmetry breakdown and vacuum expectation value vanishing.

Contribution

It demonstrates the differing effects of fermionic and bosonic interactions on the stability of (1+1) de Sitter space, highlighting the instability caused by the sine-Gordon model.

Findings

Fermionic models do not induce instabilities.

Bosonic sine-Gordon model causes symmetry breakdown.

Vacuum expectation value of the S matrix vanishes in the bosonic case.

Abstract

Instabilities of two dimensional (1+1) de Sitter space induced by interacting fields are studied. As for the case of flat Minkowski space, several interacting fermion models can be translated into free boson ones and vice versa. It is found that interacting fermion theories do not lead to any instabilities, while the interacting bosonic sine-Gordon model does lead to a breakdown of de Sitter symmetry and to the vanishing of the vacuum expectation value of the S matrix.