Reheating in geometric Weyl-invariant Einstein-Cartan gravity

TL;DR

This paper explores Weyl-invariant Einstein-Cartan gravity, showing its equivalence to general relativity with an axion-like field that can drive inflation, and emphasizes the importance of reheating dynamics in inflationary predictions.

Contribution

It demonstrates the role of reheating in Weyl-invariant Einstein-Cartan models and its impact on inflationary observables, highlighting the need for consistent reheating treatment.

Findings

Reheating dynamics significantly influence inflationary predictions.

The models are equivalent to GR with an axion-like pseudoscalar.

Reheating assumptions affect observable inflation parameters.

Abstract

We study Weyl-invariant purely gravitational theories formulated within the Einstein-Cartan framework. In the Einstein-frame description, these models are dynamically equivalent to standard general relativity coupled to an axion-like pseudoscalar degree of freedom, which naturally drives a period of cosmic inflation. Without committing to a specific microscopic mechanism for reheating, we demonstrate that the post-inflationary reheating dynamics play a crucial role in shaping the inflationary predictions. In particular, we show that assumptions about the reheating temperature and the equation-of-state parameter can significantly affect the predicted values of inflationary observables, highlighting the necessity of consistently incorporating reheating effects in the phenomenological analysis of inflationary models.