New Representation Formula for Convex Functions on Separable Normed Spaces

We derive a new representation formula for lower-semicontinuous convex functions on separable normed spaces. As a consequence of this formula, we obtain a C -approximation method for convex functions which are not necessarily differentiable.     

Algorithms for computing shape preserving spline approximations to data

Summary We treat the problem of approximating data that are sampled with error from a function known to be convex and increasing. The approximating function is a polynomial spline with knots at the data points. This paper presents results (analogous to those in [7] and [9]) that describe some approximation properties of polynomial splines and algorithms for determining the existence of a shape-preserving approximant for given data.Formerly of the Graduate Program in Operations Research, NC State University. Author nowResearch supported in part by NASA Grant NAG1-103     

Some existence results about radial graphs of constant mean curvature with boundary in parallel planes

In this work, for given H, we investigate the existence of radial cmc H annulus spanning two given non necessarily convex Jordan curves in parallel planes of . We established some existence results under hypotheses relating the geometry of the curves and the distance between the planes. Ari J. Aiolfi was partially supported by Fapergs and Programa FIPE Junior/UFSM.     

On closed convex sets without boundary rays and asymptotes

We study in finite-dimensional spaces the class of closed convex sets without boundary rays and asymptotes, denoted by and introduced by D. Gale and V. Klee. These sets, not necessarily bounded, enjoy many properties satisfied by compacts sets. New properties of this class are given and convergence analysis of this class is investigated. We also introduce the class of closed convex proper functions which have an epigraph in and we give some properties of these functions.     

Linear operator pencilsA-λB with discrete spectrum

We study the spectral properties of non-self-adjoint linear pencilsA-B of bounded operators with discrete spectrum whereB is not necessarily bijective. The main results concern the minimality, completeness and basis properties of the corresponding eigenvectors and associated vectors.     

Solvability of strongly nonlinear boundary value problems for second order differential inclusions

In this paper we study a problem for a second order differential inclusion with Dirichlet, Neumann and mixed boundary conditions. The equation is driven by a nonlinear, not necessarily homogeneous, differential operator satisfying certain conditions and containing, as a particular case, the p$p$-Laplacian operator. We prove the existence of solutions both for the case in which the multivalued nonlinearity has convex values and for the case in which it has not convex values. The presence of a maximal monotone operator in the equation make the results applicable to gradient systems with non-smooth, time invariant, convex potential and differential variational inequalities.     

Constraint qualifications in a class of nondifferentiable mathematical programming problems

The Kuhn-Tucker type necessary optimality conditions are given for the problem of minimizing the sum of a differentiable function and a convex function subject to a set of differentiable nonlinear inequalities on a convex subset C of , under the conditions similar to the Kuhn-Tucker constraint qualification or the Arrow-Hurwicz-Uzawa constraint qualification. The case when the set C is open (not necessarily convex) is shown to be a special one of our results, which helps us to improve some of the existing results in the literature.     

Planar point-objective location problems with nonconvex constraints: A geometrical construction

The planar point-objective location problem has attracted considerable interest among Location Theory researchers. The result has been a number of papers giving properties or algorithms for particular instances of the problem. However, most of these results are only valid when the feasible region where the facility is to be located is the whole space ², which is a rather inaccurate approximation in many real world location problems.In this paper, the feasible region is allowed to be any closed, not necessarily convex, setS in ². The special structure of this nonconvex vector-optimization problem is exploited, leading to a geometrical resolution procedure when the feasible regionS can be decomposed into a finite number of (not necessarily disjoint) polyhedra.     

The graph of an abstract polytope

Recently a generalization of simple convex polytopes to combinatorial entities known as abstract polytopes has been proposed. The graph of an abstract polytope of dimensiond is a regular connected graph of degreed. Given a connected regular graph of degreed, it is interesting to find out whether it is the graph of some abstract polytopeP. We obtain necessary and sufficient conditions for this, in terms of the existence of a class of simple cycles in satisfying certain properties. The main result in this paper is that if a pair of simple convex polytopes or abstract polytopes have the same two-dimensional skeleton, then they are isomorphic. Every two-dimensional face of a simple convex polytope or an abstract polytope is a simple cycle in its graph. Given the graph of a simple convex polytope or an abstract polytope and the simple cycles in this graph corresponding to all its two-dimensional faces, then we show how to construct all its remaining faces. Given a regular connected graph and a class of simple cylesD in it, we provide necessary and sufficient conditions under whichD is the class of two-dimensional faces of some abstract polytope which has as its graph.This research has been partially supported by the ISDOS Research Project at the Department of Industrial and Operations Engineering, and by the National Science Foundation under Grant No. GK-27872 with the University of Michigan.     

Multivalued differential equations in separable Banach spaces

This paper is concerned with multivalued differential equations of the form F(t,x), whereF is a multivalued mapping taking as its values nonempty compact, but not necessarily convex, subsets in a separable Banach space. The main result is connected with the existence of solutions of these equations.     

A generalization of hadwiger's transversal theorem to intersecting sets

Given an ordered family of compact convex sets in the plane, if every three sets can be intersected by some directed line consistent with the ordering, then there exists a common transversal of the family. This generalizes Hadwiger's Transversal Theorem to families of compact convex sets which are not necessarily pairwise disjoint. If every six sets can be intersected by some directed line consistent with the ordering, then there exists a common transversal which is consistent with the ordering. If the family is pairwise disjoint and every four sets can be intersected by some directed line consistent with the ordering, then there exists a common transversal which is consistent with the ordering.     

Non-convex perturbations of maximal monotone differential inclusions

We give an existence result for \(\dot x \in -- Ax + F(x)\) whereA is a maximal monotone map andF is a set-valued map, with images not necessarily convex.     

The Busemann-Petty problem for arbitrary measures

The Busemann-Petty problem asks whether symmetric convex bodies in ⁿ with smaller (n–1)-dimensional volume of central hyperplane sections necessarily have smaller n-dimensional volume. The answer to this problem is affirmative for n4 and negative for n5. In this paper we generalize the Busemann-Petty problem to essentially arbitrary measure in place of the volume. We also present applications of the latter result by proving several inequalities concerning the measure of sections of convex symmetric bodies in ⁿ.Mathematics Subject Classification (2000): 52A15, 52A21, 52A38     

Convex hull of Brownian motion ind-dimensions

We supposeK(w) to be the boundary of the closed convex hull of a sample path ofZ _t(w), 0 ≦t ≦ 1 of Brownian motion ind-dimensions. A combinatorial result of Baxter and Borndorff Neilson on the convex hull of a random walk, and a limiting process utilizing results of P. Levy on the continuity properties ofZ _t(w) are used to show that the curvature ofK(w) is concentrated on a metrically small set.     

Lototsky-Schnabl operators associated with a strictly elliptic differential operator and their corresponding Feller semigroup

Given an open bounded convex subset of ^p , a strictly elliptic differential operatorL and a continuous function , and denoted withT _L the Dirichlet operator associated withL, the Lototsky-Schnabl operators associated withT _L and are investigated. In particular, conditions are established which ensure the existence of a Feller semigroup represented by limit of powers of these operators. Then the analytic expression of the infinitesimal generator is determined and some properties of the semigroup are deduced. Finally, the saturation class of Lototsky-Schnabl operators is determined.Work supported by a C.N.R. Research Grant (n. 201.19.1, November 30, 1994)     

On a Class of Convex Sets and Functions

Given a convex subset C of ⁿ, the set-valued mapping C (where 0C is, by convention, the recession cone of C) is increasing on ₊ if and only if C contains the origin, and decreasing on ₊ if and only if C is contained in its recession cone. This simple fact enables us to define a binary operation which combines a concave or convex function on ^m with a convex subset of ⁿ to produce a convex subset of ^n+m. This binary operation is the set theoretic counterpart of a functional operation introduced by the author. In this paper, we present a detailed study of the class of convex subsets which are contained in their recession cones, and we establish some remarkable properties of our binary operation.Mathematics Subject Classifications (2000) 26A51, 26B25, 26E25.     

Almost convex groups and the eight geometries

IfM is a closed Nil geometry 3-manifold then ₁(M) is almost convex with respect to a fairly simple geometric generating set. IfG is a central extension or a extension of a word hyperbolic group, thenG is also almost convex with respect to some generating set. Combining these with previously known results shows that ifM is a closed 3-manifold with one of Thurston's eight geometries, ₁(M) is almost convex with respect to some generating set if and only if the geometry in question is not Sol.     

Vollständige und B-vollständige topologische Vektorgruppen Graphensätze und Open-Mapping Theorems

We are studying complete and B-complete topological vector groups. These Objects have been introduced by P. Kenderov [6] and D. A. Raikov [11]. They form a category TVG intermediate to the categories of topological Abelian groups and topological vector spaces and are close enough to the last one to give many useful applications to it. We first consider the problem of completion in the most used subcategories of TVG. A special functor allows to play back permanence property questions of completeness in locally convex vector groups to the same questions for locally convex vector spaces. Some examples of complete locally convex vector groups follow. We then unify some differently defined notions of B-completeness and generalize well known theorems concerning B-complete locally convex topological vector spaces to locally convex topological vector groups. Barrelledness concepts introduced in 9 and a special functor constructed in section 6 are used to formulate analogues of the closed graph and open mapping theorem for locally convex vector groups. The remainder of the note is left for applications to locally convex vector spaces. Many theorems about 1^p-sums of normed spaces are proved, as well as the B-completeness of a vast class of locally convex vector spaces including the spaces and of Köthe ([7], §13, No 5,6).     

A Helly-type theorem for simple polygons

Let be a family of simple polygons in the plane. If every three (not necessarily distinct) members of have a simply connected union and every two members of have a nonempty intersection, then {P:P in } . Applying the result to a finite family of orthogonally convex polygons, the set {C:C in } will be another orthogonally convex polygon, and, in certain circumstances, the dimension of this intersection can be determined.Supported in part by NSF grant DMS-9207019.     

Invariant sets and Lyapunov pairs for differential inclusions with maximal monotone operators

We give different conditions for the invariance of closed sets with respect to differential inclusions governed by a maximal monotone operator defined on Hilbert spaces, which is subject to a Lipschitz continuous perturbation depending on the state. These sets are not necessarily weakly closed as in [3], [4], while the invariance criteria are still written by using only the data of the system. So, no need to the explicit knowledge of neither the solution of this differential inclusion, nor the semi-group generated by the maximal monotone operator. These invariant/viability results are next applied to derive explicit criteria for a-Lyapunov pairs of lower semi-continuous (not necessarily weakly-lsc) functions associated to these differential inclusions. The lack of differentiability of the candidate Lyapunov functions and the consideration of general invariant sets (possibly not convex or smooth) are carried out by using techniques from nonsmooth analysis.