Ultraviolet Completion of the Big Bang in Quadratic Gravity

TL;DR

This paper proposes a quantum quadratic gravity model that naturally leads to inflation compatible with recent cosmological data, predicts a minimum tensor-to-scalar ratio, and connects ultraviolet completion with observable inflationary phenomena.

Contribution

It introduces a UV-complete quadratic gravity framework that dynamically induces slow-roll inflation and aligns with current cosmological constraints.

Findings

The model achieves slow-roll inflation through 1-loop running in quadratic gravity.

It predicts a minimum tensor-to-scalar ratio of 0.01.

The theory connects ultraviolet quantum gravity with observable inflationary parameters.

Abstract

We present a quantum quadratic gravity inflationary scenario that can accommodate the new cosmological constraints, which have disfavored Starobinsky inflation. The theory is asymptotically free in the ultraviolet, but 1-loop running is found to dynamically lead to slow-roll inflation toward the infrared. When a large number of matter fields contribute to the beta functions, the spectral index and the tensor-to-scalar ratio can be phenomenologically viable. We find that as inflation ends, the theory approaches its strong coupling regime and general relativity must emerge, as an effective field theory, as the universe must reheat and enter its standard radiation era. In order to avoid strong coupling, a minimum tensor-to-scalar ratio of 0.01 is predicted for this theory. Our framework offers a laboratory for connecting a concrete ultraviolet completion (quantum quadratic gravity) with inflationary dynamics, reheating, and precise cosmological observations.