  The quantum action generated by fermions which are minimally coupled to
abelian vortex background fields is studied in D=2+1 and D=3+1 Euclidean
dimensions. We present a detailed analysis of single- and binary-vortex
configurations using the recently developed method of worldline numerics. The
dependence of the fermion-induced quantum action on the fermion mass and the
magnetic fluxes carried by the vortices is studied, and the binary-vortex
interaction is computed. Additionally, we discuss the chiral condensate
generated from a dilute gas of vortices in the intermediate fermion mass range
for the case D=3+1. As a byproduct, our findings provide insight into the
validity limits of the derivative expansion, which is the standard analytical
approach to inhomogeneous backgrounds.
