Non-Perturbative Decoupling of Heavy Fermions

TL;DR

This paper demonstrates that heavy fermions decouple from low-energy physics even in non-perturbative instanton effects, with instantons suppressed in the effective theory when heavy fermions are lighter than the symmetry breaking scale.

Contribution

It introduces a mechanism showing how instanton effects are suppressed in the effective theory with heavy fermions lighter than the symmetry breaking scale.

Findings

Heavy fermions decouple from instanton effects.

Instanton effects can be expressed as local operators.

The effective theory suppresses instantons.

Abstract

We show that heavy fermions decouple from the low energy physics also in non-perturbative instanton effects. Provided the heavy fermions are lighter than the symmetry breaking scale, all the instanton effects should be expressed as local operators in the effective Lagrangian. The effective theory itself doesn't admit instantons. We present the mechanism which suppresses instantons in the effective theory.