Trans-Planckian Censorship, Inflation and Dark Matter

TL;DR

This paper discusses the trans-Planckian problem in inflationary cosmology, showing it constrains the inflation scale and impacts dark matter models, while proposing inflationary models consistent with these constraints and observations.

Contribution

It demonstrates the link between trans-Planckian constraints and inflation scale, and introduces inflationary models compatible with these limits and observational data.

Findings

Trans-Planckian problem constrains inflation scale to H_inf ≤ 1 GeV.

Small inflation scale affects dark matter generation scenarios.

Proposes inflationary models satisfying trans-Planckian constraints and observational data.

Abstract

If the inflationary phase lasted longer than the minimal period, the length scales observed today originate from modes that were smaller than the Planck length during inflation. It was recently argued that this "trans-Planckian problem" can never arise in a consistent string theory framework, which places a stringent constraint on the energy scale of inflation, $V^{1/4}\lesssim 10^9$ GeV. In this paper, we show that this requirement corresponds to a very small Hubble scale during inflation, $H_{\rm inf}\lesssim 1$ GeV, and therefore has serious consequences on scenarios where the dark matter density was generated by amplification of quantum fluctuations during inflation. We also present a class of inflationary models which both satisfy the above limit for the scale of inflation and are in perfect agreement with observational data.