Gravitons Enhance Fermions during Inflation

TL;DR

This paper investigates how quantum gravitational effects during inflation influence massless fermions, revealing a time-dependent renormalization of the fermion field strength due to graviton interactions.

Contribution

It provides the first detailed calculation of one-loop quantum gravity corrections to massless fermions during inflation, demonstrating a specific time-dependent field strength renormalization.

Findings

Fermion behavior is affected by quantum gravity during inflation.

The field strength renormalization Z_2(t) decreases logarithmically with scale factor.

Hartree approximation yields similar qualitative results with different coefficients.

Abstract

We solve the effective Dirac equation for massless fermions during inflation in the simplest gauge, including all one loop corrections from quantum gravity. At late times the result for a spatial plane wave behaves as if the classical solution were subjected to a time dependent field strength renormalization of Z_2(t) = 1 - \frac{17}{4 \pi} G H^2 \ln(a) + O(G^2). We show that this also follows from making the Hartree approximation, although the numerical coefficients differ.