On contrast structures with a multizonal interior layer

A boundary value problem for a singularly perturbed differential equation of second order is considered in two cases, when one root of the degenerate equation is two-tuple. It is proved that in the first case the problem has a solution with the transition from the two-tuple root of the degenerate equation to one-tuple root in the small neighbourhood of an internal point of the interval, and in the second case the problem has a solution which has the spike in the interior layer. Such solutions are named, correspondingly, a contrast structure of step-type and a contrast structure of spike-type. In each case the asymptotic expansion of the contrast structure is constructed. It distinguishes from the known expansion in the case, when all the roots of the degenerate equation are one-tuple, in particular, the interior layer is multizonal.