ABSTRACT
In numerous nonlinear phenomena the occurrence of isolas or closed isolated loops of solutions have been observed. Theoretically such phenomena are described by the solutions of nonlinear eigenvalue problems which depend on two (or more) parameters. This chapter sketches a new way to determine the occurrence of isolas by local studies. The basic idea is to characterize special solutions which are the “centers” of a family of isolas. The chapter also outlines the unified theory of perturbed bifurcation and isola formation.
