Coleman-Weinberg linear inflation: metric vs. Palatini formulation

TL;DR

This paper compares metric and Palatini formulations of Coleman-Weinberg linear inflation, highlighting differences in predictions and potential experimental discriminability based on non-minimal coupling strength.

Contribution

It provides an improved analysis of reheating and a comparative study of metric versus Palatini formulations in Coleman-Weinberg inflation.

Findings

Both formulations predict linear inflation.

Different number of e-folds in metric and Palatini.

Future experiments could distinguish the two models.

Abstract

It has been previously shown that the linear inflation appears naturally as a solution of Coleman-Weinberg inflation, provided that the inflaton has a non-minimal coupling to gravity and the Planck scale is dynamically generated. We revisit the previous study by improving the discussion of reheating and by comparing the results of the metric and the Palatini formulations of non-minimal gravity. We find that both formulations predict linear inflation but a different number of $e$-folds. If the non-minimal coupling is larger than one, future experimental sensitivity can discriminate between the two realizations.