Wilson Line Inflation

TL;DR

This paper introduces a novel string theory inflation model where the inflaton is a Wilson line, connecting various D-brane inflation scenarios and allowing for hybrid inflation with potential observational signatures like cosmic strings.

Contribution

It develops a generalized framework for Wilson line inflation in string theory, linking it to existing models and addressing issues like the eta-problem, with explicit examples and phenomenological implications.

Findings

The model can avoid the eta-problem common in brane inflation.

It produces spectral indices with both blue and red tilts.

Remnant cosmic string tension is constrained to Gμ ≲ 10^{-7}.

Abstract

We present a general set-up for inflation in string theory where the inflaton field corresponds to Wilson lines in compact space in the presence of magnetic fluxes. T-dualities and limits on the value of the magnetic fluxes relate this system to the standard D-brane inflation scenarios, such as brane-antibrane inflation, D3/D7 brane inflation and different configurations of branes at angles. This can then be seen as a generalised approach to inflation from open string modes. Inflation ends when the Wilson lines achieve a critical value and an open string mode becomes tachyonic. Then hybrid-like inflation, including its cosmic string remnants, is realized in string theory beyond the brane annihilation picture. Our formalism can be incorporated within flux-induced moduli stabilisation mechanisms in type IIB strings. Also, contrary to the standard D-brane separation, Wilson lines can be considered in heterotic string models. We provide explicit examples to illustrate similarities and differences of our mechanism to D-brane inflation. In particular we present an example in which the eta-problem present in brane inflation models is absent in our case. We have examples with both blue and red tilted spectral index and remnant cosmic string tension $G\mu \lesssim 10^{-7}$.