Non-perturbative decoupling of heavy fermions

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 doesnʹt admit instantons. We present the mechanism which suppresses instantons in the effective theory.