Relaxing the TCC Bound on Inflationary Cosmology?

TL;DR

This paper explores how relaxing the TCC bound on inflationary energy scales is possible if the universe's equation of state shifts to near-marginal acceleration after initial slow roll, though such models seem unnatural.

Contribution

It proposes a scenario where the TCC bounds can be loosened by changing the universe's equation of state post-slow roll, challenging previous strict limits.

Findings

Relaxed bounds on inflation energy scale and tensor-to-scalar ratio.

Model construction appears unnatural.

Potential implications for inflationary theory.

Abstract

We demonstrate that the strict upper bounds on the energy scale of inflation and on the tensor-to-scalar ratio can be somewhat relaxed if we assume that - after an initial period of slow rolling when scales probed today in CMB experiments exit the Hubble radius - the equation of state of the background changes to correspond to an almost marginally accelerating universe. Constructing an actual model in which this happens appears, however, to be unnatural.