Bogomol’nyi-Prasad-Sommerfield walls and junctions in supersymmetric nonlinear sigma models

Bogomol’nyi-Prasad-Sommerfield (BPS) walls and junctions are studied in N=1 supersymmetric (SUSY) nonlinear sigma models in four spacetime dimensions. New BPS junction solutions connecting N discrete vacua are found for nonlinear sigma models with several chiral scalar superfields. A nonlinear sigma model with a single chiral scalar superfield is also found which has a moduli space of the topology of S¹ and admits BPS walls and junctions connecting arbitrary points in moduli space. SUSY conditions in nonlinear sigma models are classified either as stationary points of a superpotential or as singularities of the Kähler metric in field space. The total number of SUSY vacua is invariant under holomorphic field redefinitions if we count “runaway vacua” also.