Implications of purely classical gravity for inflationary tensor modes

TL;DR

This paper explores how a classical gravity framework alters the interpretation of inflationary gravitational wave signals, showing that detecting primordial waves no longer directly indicates the inflation scale due to initial amplitude uncertainties.

Contribution

It introduces the idea that classical gravity models change the link between gravitational wave detection and inflation scale, challenging standard quantum-based assumptions.

Findings

Classical gravity models increase uncertainty in tensor mode amplitudes.

Detection of primordial gravitational waves does not necessarily imply high-scale inflation.

Classical approach allows bypassing observational constraints on inflation scale.

Abstract

We discuss the implications of purely classical, instead of quantum, theory of gravity for the gravitational wave spectrum generated during inflation. We show that a positive detection of primordial gravitational waves will no longer suffice to determine the scale of inflation in this case -- even a high-scale model of inflation can bypass the observational constraints due to large uncertainties in the initial classical amplitude of the tensor modes.