arXiv subjects

Amos Uderzo

Publications and source records attributed to Amos Uderzo.

25 records · Page 2Linked to original sources

arXiv2015

A strong metric subregularity analysis of nonsmooth mappings via steepest displacement rate

In this paper, a systematic study of the strong metric subregularity property of mappings is carried out by means of a variational tool, called steepest displacement rate. With the aid of this tool, a simple characterization of strong metric subregularity for multifunctions acting in metric spaces is formulated. The resulting criterion is shown to be useful for establishing stability properties of the strong metric subregularity in the presence of perturbations, as well as for deriving various conditions, enabling to detect such a property in the case of nonsmooth mappings. Some of these conditions, involving several nonsmooth analysis constructions, are then applied in studying the isolated calmness property of the solution mapping to parameterized generalized equations.

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arXiv2015

Convexity of the images of small balls through perturbed convex multifunctions

In the present paper, the following convexity principle is proved: any closed convex multifunction, which is metrically regular in a certain uniform sense near a given point, carries small balls centered at that point to convex sets, even if it is perturbed by adding C^{1,1} smooth mappings with controlled Lipschizian behaviour. This result, which is valid for mappings defined on a subclass of uniformly convex Banach spaces, can be regarded as a set-valued generalization of the Polyak convexity principle. The latter, indeed, can be derived as a special case of the former. Such an extension of that principle enables one to build large classes of nonconvex multifunctions preserving the convexity of small balls. Some applications of this phenomenon to the theory of set-valued optimization are proposed and discussed.

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arXiv2014

On the variational behaviour of functions with positive steepest descent rate

This paper investigates some aspects of the variational behaviour of nonsmooth functions, with special emphasis on certain stability phenomena. Relationships linking such properties as sharp minimality, superstability, error bound and sufficiency of first-order optimality conditions are discussed. Their study is performed by employing the steepest descent rate, a rather general tool, which is adequate for a metric space analysis. The positivity of the steepest descent rate is then characterized in terms of $Φ$-subdifferentials. If specialized to a Banach space setting, the resulting characterizations subsume known results on the stability of error bounds.

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arXiv2013

Localizing vector optimization problems with application to welfare economics

In the present paper, the Polyak's principle, concerning convexity of the images of small balls through C1,1 mappings, is employed in the study of vector optimization problems. This leads to extend to such a context achievements of local programming, an approach to nonlinear optimization, due to B.T. Polyak, which consists in exploiting the benefits of the convex local behaviour of certain nonconvex problems. In doing so, solution existence and optimality conditions are established for localizations of vector optimization problems, whose data satisfy proper assumptions. Such results are subsequently applied in the analysis of welfare economics, in the case of an exchange economy model with infinite-dimensional commodity space. In such a setting, the localization of an economy yields existence of Pareto optimal allocations, which, under certain additional assumptions, lead to competitive equilibria.

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arXiv2013

On Lipschitz semicontinuity properties of variational systems with application to parametric optimization

In this paper two properties of recognized interest in variational analysis, known as Lipschitz lower semicontinuity and calmness, are studied with reference to a general class of variational systems, i.e. to solution mappings to parameterized generalized equations. In consideration of the metric nature of such properties, some related sufficient conditions are established, which are expressed via nondegeneracy conditions on derivative-like objects appropriate for a metric space analysis. For certain classes of generalized equations in Asplund spaces, it is shown how such conditions can be formulated by using the Fréchet coderivative of the field and the derivative of the base. Applications to the stability analysis of parametric constrained optimization problems are proposed.

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arXiv2013

On the Polyak convexity principle and its application to variational analysis

According to a result due to B.T. Polyak, a mapping between Hilbert spaces, which is $C^{1,1}$ around a regular point, carries a ball centered at that point to a convex set, provided that the radius of the ball is small enough. The present paper considers the extension of such result to mappings defined on a certain subclass of uniformly convex Banach spaces. This enables one to extend to such setting a variational principle for constrained optimization problems, already observed in finite dimension, that establishes a convex behaviour for proper localizations of them. Further variational consequences are explored.

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arXiv2013

Some dual conditions for global weak sharp minimality of nonconvex functions

Weak sharp minimality is a notion emerged in optimization, whose utility is largeley recognized in the convergence analysis of algorithms for solving extremum problems as well as in the study of the perturbation behaviour of such problems. In the present paper some dual constructions of nonsmooth analysis, mainly related to quasidifferential calculus and its recent developments, are employed in formulating sufficient conditions for global weak sharp minimality. They extend to nonconvex functions a condition, which is known to be valid in the convex case. A feature distinguishing the results here proposed is that they avoid to assume the Asplund property on the underlying space.

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