Non-perturbative decoupling of massive fermions

TL;DR

This paper uses lattice simulations to show that massive fermions in SU(2) gauge theory decouple at low energies, leading to a confining pure gauge behavior, confirming theoretical expectations.

Contribution

It provides the first non-perturbative lattice evidence of fermion decoupling in SU(2) gauge theory with massive fermions.

Findings

Massive fermions decouple at low energies as expected.

The infrared behavior matches that of pure SU(2) gauge theory.

Gradient flow coupling measurements confirm decoupling.

Abstract

SU(2) gauge theory with Nf=24 massless fermions is non-interacting at long distances, i.e. it has an infrared fixed point at vanishing coupling. With massive fermions the fermions are expected to decouple at energy scales below the fermion mass, and the infrared behaviour is that of confining SU(2) pure gauge theory. We demonstrate this behaviour non-perturbatively with lattice Monte Carlo simulations by measuring the gradient flow running coupling.