Trans-Planckian Censorship and Inflationary Cosmology

TL;DR

The paper explores how the Trans-Planckian Censorship Conjecture constrains inflationary models, requiring very low inflation energy scales and predicting negligible primordial gravitational waves, thus impacting early universe cosmology.

Contribution

It applies the TCC to inflationary cosmology, deriving strict bounds on inflation energy scale and slow-roll parameters, highlighting significant fine-tuning issues.

Findings

Inflation energy scale must be below 10^9 GeV.

Primordial gravitational waves are predicted to be negligible.

Severe fine-tuning of initial conditions is required.

Abstract

We study the implications of the recently proposed Trans-Planckian Censorship Conjecture (TCC) for early universe cosmology and in particular inflationary cosmology. The TCC leads to the conclusion that if we want inflationary cosmology to provide a successful scenario for cosmological structure formation, the energy scale of inflation has to be lower than $10^9$ GeV. Demanding the correct amplitude of the cosmological perturbations then forces the generalized slow-roll parameter $\epsilon$ of the model to be very small ($<10^{-31}$). This leads to the prediction of a negligible amplitude of primordial gravitational waves. For slow-roll inflation models, it also leads to severe fine tuning of initial conditions.