Two switching multiple disorder problems for Brownian motions

Abstract

The multiple disorder problem seeks to determine a sequence of stopping times which are as close as possible to the unknown times of disorders at which the observation process changes its probability characteristics. We derive closed form solutions in two formulations of the multiple disorder problem for an observable Brownian motion with switching constant drift rates. The method of proof is based on the reduction of the initial problems to appropriate optimal switching problems and the analysis of the associated coupled free-boundary problems. We also describe the sequential switching multiple disorder detection procedures resulting from these formulations.