Directional quasi/pseudo-normality as sufficient conditions for metric subregularity

Abstract

In this paper we study sufficient conditions for metric subregularity of a set-valued map which is the sum of a single-valued continuous map and a locally closed subset. First we derive a sufficient condition for metric subregularity which is weaker than the so-called first-order sufficient condition for metric subregularity (FOSCMS) by adding an extra sequential condition. Then we introduce a directional version of the quasi-normality and the pseudo-normality which is stronger than the new {weak} sufficient condition for metric subregularity but is weaker than the classical quasi-normality and pseudo-normality respectively. Moreover we introduce a nonsmooth version of the second-order sufficient condition for metric subregularity and show that it is a sufficient condition for the new sufficient condition for metric {sub}regularity to hold. An example is used to illustrate that the directional pseduo-normality can be weaker than FOSCMS. For the class of set-valued maps where the single-valued mapping is affine and the abstract set is the union of finitely many convex polyhedral sets, we show that the pseudo-normality and hence the directional pseudo-normality holds automatically at each point of the graph. Finally we apply our results to the complementarity and the Karush-Kuhn-Tucker systems.