An existence theorem for a fractional control problem

Computational algorithms in mathematical programming have been much in use in the theory of optimal control (see, for example Refs. 1–2). In the present work, we use the algorithm devised by Dinkelback (Ref. 3) for a nonlinear fractional programming problem to prove an existence theorem for a control problem with the cost functional having a fractional form which subsumes the control problem considered by Lee and Marcus (Ref. 4) as a particular case.The author is thankful to the referee for suggestions.     

An existence theorem for a control problem in oil recovery

This paper studies a Sturm-Liouville system, arising from the stability of interfaces in secondary recovery process : the oil is obtained from a porous medium by displacing it with a second fluid water. A polymer solute contained in an intermediate region between water and oil is used to minimize the "fingering" phenomenon the instability constants in time of the perturbations. The growth constants may be controlled by the viscosity in the intermediate region. An existence theorem for an optimal viscosity in the intermediate region is given, which allows us to minimize the maximum growth constant. The Rayleigh's quotient and the properties of the weakly continuous functionals on a bounded domain of a Hilbert space are used. A characterization is given for the domain of the wavenumbers for which we have only positive growth constants     

An existence and uniqueness theorem for one optimal control problem

In this paper we investigate the existence and uniqueness for an optimal control problem with processes described by a quasilinear parabolic equation with controls in coefficients and the right side of this equation.     

An existence theorem for antichains

Let k₁, k₂,…, k_n be given integers, 1 ? k₁ ? k₂ ? … ? k_n, and let S be the set of vectors x = (x₁,…, x_n) with integral coefficients satisfying 0 ? x_i ? k_i, i = 1, 2, 3,…, n. A subset H of S is an antichain (or Sperner family or clutter) if and only if for each pair of distinct vectors x and y in H the inequalities x_i ? y_i, i = 1, 2,…, n, do not all hold. Let |H| denote the number of vectors in H, let K = k₁ + k₂ + … + k_n and for 0 ? l ? K let (l)H denote the subset of H consisting of vectors h = (h₁, h₂,…, h_n) which satisfy h₁ + h₂ + … + h_n = l. In this paper we show that if H is an antichain in S, then there exists an antichain H′ in S for which |(l)H′| = 0 if $\text{l <}\text{K}\text{2}$, $\text{|(}\text{K}\text{2}\text{)H′| = |(}\text{K}\text{2}\text{)H|}$ if K is even and |(l)H′| = |(l)H| + |(K ? l)H| if $\text{l>}\text{K}\text{2}$.     

An existence theorem for an inverse problem for a semilinear hyperbolic system

In the present paper, we consider a semilinear hyperbolic system with coefficients depending on different solution components. We study the inverse problem of finding one of the coefficients on the basis of additional information on the solution. The proof of the existence theorem for the inverse problem is based on the reduction of the latter to a nonlinear operator equation, which is a nonlinear integro-differential equation for the unknown coefficient. This approach was used in [1] to prove the existence of a solution of the inverse problem for a quasilinear hyperbolic equation. Inverse problems for quasilinear hyperbolic equations and systems were also considered in [2–6] and other papers.Translated from Differentsialnye Uravneniya, Vol. 40, No. 9, 2004, pp. 1155–1165.Original Russian Text Copyright © 2004 by Denisov.     

An existence and uniqueness theorem for an optimal inventory problem with forecasting

An existence and uniqueness theorem is proved for an optimal inventory problem with forecasting. The model assumes costs are fixed and that unsatisfied demand is lost. At each stage a forecast is obtained on the basis of which the decisionmaker has a known conditional probability distribution of demand. The theorem is a generalization of a result stated but not proved by White.     

An existence theorem for harmonic maps

The aim of this article is to prove the existence of a harmonic map in a given homotopy class from a non-compact manifold into another one, while this class fulfills a geometrical simplicity condition.     

An existence theorem for optimal controls

An existence theorem is given based on a criterion ensuring compactness of the controls in the metric corresponding to convergence in measure.This research was performed under NSF Grant No. GP-7372     

An existence theorem for invariant manifolds

For systems of the form =Ax +F ₁ (x, y, z), =By +F ₂ (x, y,z), =Cz +F ₃ (x, y, z) possessingP = {(0,0,z)} as invariant manifold we present sufficient conditions for the extension ofP to an invariant manifold of the form (x, s (x, z), z). Hereby we assume that the spectrum _A ofA is located to the left and the spectrum _b ofB to the right of a vertical straight linel in . In the case where the spectrum _C ofC lies to the left ofl too such an extension ofP is rather simple. We consider the situation where _{A C} cannot be separated from _B by a vertical line in .

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Zusammenfassung Für Systeme der Form =Ax +F ₁ (x, y, z), =By +F ₂ (x, y,z), =Cz +F ₃ (x, y, z) mitP = {(0,0,z)} als invarianter Mannigfaltigkeit geben wir Bedingungen an, unter welchen sichP zu einer invarianten Mannigfaltigkeit der Form (x, s (x, z), z) fortsetzen läßt. Wir gehen stets davon aus, daß das Spektrum _A vonA links und das Spektrum _B vonB rechts einer vertikalen Geradenl in liegen. Eine derartige Fortsetzung vonP ist einfach, falls das Spektrum _C vonC ebenfalls links vonl liegt. Wir untersuchen den Fall, in welchem _{A C} sich nicht durch eine vertikale Gerade von _B trennen läßt.

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Dedicated to H. W. Knobloch on the occasion of his sixtieth birthday

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Supported by the Volkswagenwerk foundation     

An existence theorem for harmonic sections

In the context of sections of Riemannian fibre bundles, the analogue of a harmonic mapping of Riemannian manifolds is a harmonic section. Existence and unique continuation theory for harmonic sections generalizes, and may be derived from, that for harmonic maps. The results presented here are extracted from the author's Ph.D. thesis.     

An existence theorem for planar maps

The main result of this paper is a theorem concerning possible cubic maps on the plane or sphere. The dual approach of spherical triangulations will be used. Every such triangulation must contain a vertex of degree less than 8 and other than 5, or else contain one of a list of 5 configurations. Due to the occurrence of these five configurations in four color reduction arguments, this implies that a minimal five color map must have at least one face with six or seven neighbors. The theorem is given in Heesch [1, p. 129 ff.], but the proof here is much shorter, due to a modification of Heesch's principle of “discharging”. The principle itself is obtained by exploiting the Euler formula, and should be compared with the theory of Euler contributions as developed by Ore in [3], and by Ore and Stemple [4].     

Kneser''s theorem and the multivalued generalized order complementarity problem

The Generalized Order Complementarity Problem studied by Isac and Kostreva is extended to multivalued mappings satisfying a condition proposed by Kneser. Existence of solutions to a related fixed point problem leads to existence theory for the new type of complementarity problem. Some important applications include problems in lubrication and in economics in which functions are set valued.     

An existence theorem for the unmodified Vlasov Equation

The initial value problem for the modified Vlasov equation with a mollification parameter δ > 0, as introduced by Batt, has a unique global solution in the weak sense whenever f₀ ε L¹ and f₀ ≧ 0 λ-a.e. Assuming boundedness of f₀ and boundedness of the kinetic energy, it is shown that, as δ → 0, there are subsequences δ_n → 0 such that the corresponding solutions converge weakly in the measure-theoretical sense. The limits are shown to be global weak solutions of the initial value problem for Vlasov's equation, and these solutions are seen to be weakly continuous with respect to t. For the plasma physical case, boundedness of the kinetic energy is a consequence of energy conservation.     

An existence theorem for the Scheinkman-Weiss economic model

The Scheinkman-Weiss model and later works by Conze-Lasry-Scheinkman provide insights on cycles and correlations of economies with incomplete markets, namely with borrowing constraints. This work gives a mathematical solution in the case of high relative risk aversion, which has not yet been solved. The existence of an equilibrium results from the solution of a system of nonlinear functional differential equations. High risk aversion leads to new mathematical difficulties, not present in previous papers on this subject.This work is an extension of previous works done under the direction of Professor Jean-Michel Lasry, University of Paris 9, Dauphine. The author is sincerely grateful to Professor Lasry who suggested the idea of this article and whose remarks were always of help.