Inflation as a probe of new physics

TL;DR

This paper explores how inflation can serve as a tool to detect new physics near the string or Planck scale, focusing on vacuum choices and their observable effects on the universe's expansion and primordial spectrum.

Contribution

It introduces the idea that vacuum ambiguity in inflation models, especially with many fields, can lead to observable signatures of new physics.

Findings

Vacuum choice affects primordial spectrum and expansion rate

Multiple fields can amplify effects of new physics

Vacuum ambiguity is a new parameter in inflation models

Abstract

In this paper we consider inflation as a probe of new physics near the string or Planck scale. We discuss how new physics can be captured by the choice of vacuum, and how this leads to modifications of the primordial spectrum as well as the way in which the universe expands during inflation. Provided there is a large number of fields contributing to the vacuum energy -- as typically is expected in string theory -- we will argue that both types of effects can be present simultaneously and be of observational relevance. Our conclusion is that the ambiguity in choice of vacuum is an interesting new parameter in serious model building.