Gauss-Bonnet Inflation

TL;DR

This paper explores an Einstein-Scalar-Gauss-Bonnet theory that supports inflationary solutions with a decaying scalar field, providing natural exit mechanisms to Milne phases, advancing understanding of early universe inflation models.

Contribution

It demonstrates that a pure scalar-Gauss-Bonnet theory with quadratic coupling can naturally produce inflationary and exit solutions, expanding the theoretical landscape of early universe cosmology.

Findings

Supports inflationary de Sitter solutions with a decaying scalar field

Provides natural exit mechanisms from inflation to Milne phases

Shows the Ricci scalar can be neglected at early times in this theory

Abstract

We consider an Einstein-Scalar-Gauss-Bonnet gravitational theory, and argue that at early times the Ricci scalar can be safely ignored. We then demonstrate that the pure scalar-Gauss-Bonnet theory, with a quadratic coupling function, naturally supports inflationary -- de Sitter -- solutions. During inflation, the scalar field decays exponentially and its effective potential remains always bounded. The theory contains also solutions where these de Sitter phases possess a natural exit mechanism and are replaced by linearly expanding -- Milne -- phases.