Inflation with negative potentials and the signature reversal symmetry

TL;DR

This paper examines models of quantum cosmology with negative scalar potentials, revealing an underlying symmetry that influences inflation predictions and demonstrating that such models often suffer from instabilities, questioning their physical viability.

Contribution

The paper uncovers a fundamental symmetry in models with negative potentials and analyzes the stability issues of inflationary solutions within these frameworks.

Findings

Identifies a symmetry underlying inflation with negative potentials.

Shows that inflationary solutions often have tachyonic and ghost instabilities.

Questions the physical relevance of such inflationary models.

Abstract

We discuss recent papers by Hartle, Hawking and Hertog, which proposed that quantum cosmology could predict an inflating universe in models with negative scalar potentials. Here we show that this is a result of an underlying symmetry which is manifest in both classical and quantum theory. Moreover, we show that inflating solutions in such models generally develop tachyonic and ghost instabilities and are therefore unphysical in realistic theories.