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 Kaehler metric in field space. The total number of SUSY vacua is invariant under holomorphic field redefinitions if we count 'runaway vacua' also