Fermion Mass Generation in de Sitter Space

TL;DR

This paper demonstrates that massless fermions in de Sitter space gain an effective mass through one-loop radiative corrections from a Yukawa interaction with a light scalar, affecting their dynamics during inflation.

Contribution

It shows that fermions acquire a mass in de Sitter space via quantum corrections, preserving chirality and resembling massive Dirac fermions, which is a novel insight into fermion behavior during inflation.

Findings

Fermions gain a mass proportional to the expansion rate.

The effective fermionic action remains nonlocal but chirality-preserving.

Fermion dynamics mimic those of a massive Dirac particle.

Abstract

We study the one-loop radiative corrections for massless fermions in de Sitter space induced by a Yukawa coupling to a light, nearly minimally coupled scalar field. We show that the fermions acquire a mass. Next we construct the corresponding (nonlocal) effective fermionic action, which -- in contrast to the case of a massive Dirac fermion -- preserves chirality. Nevertheless, the resulting fermion dynamics is precisely that of a Dirac fermion with a mass proportional to the expansion rate. Our finding supports the view that an observer or a test particle responds to a scalar field in inflation by shifting its energy rather than seeing a thermal bath.