WIMP Dark Matter and Unitarity-Conserving Inflation via a Gauge Singlet Scalar

TL;DR

This paper investigates a gauge singlet scalar as a unified candidate for driving inflation and constituting dark matter, demonstrating viable parameter space and addressing unitarity issues in inflation models.

Contribution

It revisits singlet scalar inflation and Higgs portal dark matter, showing the model's viability and its ability to stabilize the electroweak vacuum while resolving unitarity problems.

Findings

Large viable parameter space for inflation and dark matter.

Singlet mass below 2 TeV consistent with Planck data.

Almost entire parameter range testable by XENON1T.

Abstract

A gauge singlet scalar with non-minimal coupling to gravity can drive inflation and later freeze out to become cold dark matter. We explore this idea by revisiting inflation in the singlet direction (S-inflation) and Higgs Portal Dark Matter in light of the Higgs discovery, limits from LUX and observations by Planck. We show that large regions of parameter space remain viable, so that successful inflation is possible and the dark matter relic abundance can be reproduced. Moreover, the scalar singlet can stabilise the electroweak vacuum and at the same time overcome the problem of unitarity-violation during inflation encountered by Higgs Inflation, provided the singlet is a real scalar. The 2-$\sigma$ Planck upper bound on $n_s$ imposes that the singlet mass is below 2 TeV, so that almost the entire allowed parameter range can be probed by XENON1T.