On semiregularity of mappings

TL;DR

This paper explores the concept of semiregularity, a weakening of metric regularity, establishing its theoretical foundations, relationships with other properties, and applications to inexact Newton schemes for generalized equations.

Contribution

It provides a comprehensive and extended theory of semiregularity, clarifies its relation to other regularity properties, and applies it to inexact Newton methods.

Findings

Semiregularity is equivalent to openness with a linear rate at a point.

Necessary and sufficient conditions for semiregularity are derived.

Application to inexact Newton schemes demonstrates practical relevance.

Abstract

There are two basic ways of weakening the definition of the well-known metric regularity property by fixing one of the points involved in the definition. The first resulting property is called metric subregularity and has attracted a lot of attention during the last decades. On the other hand, the latter property which we call semiregularity can be found under several names and the corresponding results are scattered in the literature. We provide a self-contained material gathering and extending the existing theory on the topic. We demonstrate a clear relationship with other regularity properties, for example, the equivalence with the so-called openness with a linear rate at the reference point is shown. In particular cases, we derive necessary and/or sufficient conditions of both primal and dual type. As an application we study an inexact Newton-type scheme for generalized equations with not necessarily differentiable single-valued part.