Carmela Vitanza

Time-Dependent Equilibrium Problems

Abstract The paper presents variational models for dynamic traffic, dynamic market, and evolutionary financial equilibrium problems taking into account that the equilibria are not fixed and move with time. The authors provide a review of the history of the variational inequality approach to problems in physics, traffic networks, and others, then they model the dynamic equilibrium problems as time-dependent variational inequalities and give existence results. Moreover, they present an infinite dimensional Lagrangean duality and apply this theory to the above time-dependent variational inequalities.

QUASI-VARIATIONAL APPROACH OF A COMPETITIVE ECONOMIC EQUILIBRIUM PROBLEM WITH UTILITY FUNCTION: EXISTENCE OF EQUILIBRIUM

A Walrasian pure exchange economy with utility functions, a particular case of a general economic equilibrium problem, is considered in this paper. We assume that each agent is endowed with goods and maximizes his utility function, under his budget constraints. We are able to characterize the Walrasian equilibria as solution of an associated quasi-variational inequality. This approach allows us to obtain an existence result of equilibrium solutions. As an application, we provide the explicit equilibrium in the case of two agents and two goods.

A new contribution to a dynamic competitive equilibrium problem

The aim of this paper is to study the Walrasian equilibrium problem when the data are time dependent. For this model an existence result is provided using the variational inequality theory in infinite dimensional spaces. Our results are the generalization of some of the results obtained by several authors in the static case (see e.g. Donato et al. (2008) [5], Donato et al. (2008) [4] and Mordukhovich (2006) [11], Nagurney (1993) [2] and the references therein).

An existence result of a quasi-variational inequality associated to an equilibrium problem

In this paper we consider a Walrasian pure exchange economy with utility function which is a particular case of a general economic equilibrium problem, without production. We assume that each agent is endowed with at least of a commodity, his preferences are expressed by an utility function and it prevails a competitive behaviour: each agent regards the prices payed and received as independent of his own choices. The Walrasian equilibrium can be characterized as a solution to a quasi-variational inequality. By using this variational approach, our goal is to prove an existence result of equilibrium solutions.

Variational inequalities and the elastic-plastic torsion problem

We show that, under suitable conditions, the variational inequality that expresses the elastic-plastic torsion problem is equivalent to a variational inequality on a convex set which depends on δ(x)=d(x, ∂Ω). Such an equivalence allows us to find the related Lagrange multipliers and to exhibit a computational procedure based on the subgradient method.

Topics on Variational Analysis and Applications to Equilibrium Problems

We observe how many equilibrium problems obey a generalized complementarity condition, which in general leads to a variational inequality. We illustrate this fact, by studying the elastic–plastic torsion problem and finding the related Lagrange multipliers.

Variational Problem, Generalized Convexity, and Application to a Competitive Equilibrium Problem

The main purpose of this article is to present a new formulation of a competitive equilibrium in terms of a suitable quasivariational inequality involving multivalued maps. More precisely, a pure exchange economy is considered where the consumers preferences are represented by utility functions that we assume to be generalized concave and non-differentiable. In the concave context, we have characterized the equilibrium by means of a variational problem involving the subdifferential. Now, by relaxing concavity and differentiability assumptions on utility functions, the subdifferential operator of the utility function is replaced by a suitable multimap involving a new concept, recently introduced in [1]: the normal operator to the adjusted sublevel sets. Thanks to this variational formulation we are able to achieve the existence of equilibrium points by using arguments of the set-valued analysis. Finally, we provide some example of utility functions which verify our assumptions.

Oblique derivative problem for uniformly elliptic operators with VMO coefficients and applications

Abstract Strong solvability in Sobolev spaces W 2, p (Ω) is proved for the regular oblique derivative problem for second order uniformly elliptic operators with VMO-principal coefficients. The results are applied to the study of degenerate (tangential) oblique derivative problem in the case of neutral vector field on the boundary.

Quasivariational Inequalities for a Dynamic Competitive Economic Equilibrium Problem

The aim of this paper is to consider a dynamic competitive economic equilibrium problem in terms of maximization of utility functions and of excess demand functions. This equilibrium problem is studied by means of a time-dependent quasivariational inequality which is set in the Lebesgue space . This approach allows us to obtain an existence result of time-dependent equilibrium solutions.

On the Study of an Economic Equilibrium with Variational Inequality Arguments

The main purpose of this paper is to investigate on the existence of a competitive equilibrium for a market with consumption and exchange. A variational representation is used to study this problem. More precisely, we consider an economy where utility functions are assumed concave and non-differentiable, and we characterize the equilibrium by means of a variational problem involving the subdifferential multimap. Thanks to this approach, by introducing suitable perturbed utility functions, we achieve an existence result when the operator is not coercive and the convex set might be unbounded.