Quantum corrections to solitons and BPS saturation

We review our work of the past decade on one-loop quantum corrections to the mass M and central charge Z of solitons in supersymmetric field theories: the kink, the vortex, and the monopoles (focussing on the kink and the monopoles here). In each case a new feature was needed to obtain BPS saturation: a new anomaly-like contribution to Z for the kink and the N = 2 monopole, the effect of classical winding of the quantum vortex contributing to Z, surface terms contributing to M of the N = 4 monopole and to Z of the N = 2 and N = 4 monopoles, and composite operator renormalization for the currents of the “finite”N = 4 model. We use dimensional regularization, modified to preserve susy and be applicable to solitons, and suitable renormalization conditions. In the mode expansion of bosonic and fermionic quantum fields, zero modes appear then as massless nonzero modes.