A weak Kantorovich existence theorem for the solution of nonlinear equations

The Kantorovich theorem is a fundamental tool in nonlinear analysis for proving the existence and uniqueness of solutions of nonlinear equations arising in various fields. This theorem was weakened recently by Argyros who used a combination of Lipschitz and center-Lipschitz conditions in place of the Lipschitz conditions of the Kantorovich theorem. In the present paper we prove a weak Kantorovich-type theorem that gives the same conclusions as the previous two results under weaker conditions. Illustrative examples are provided in the paper.     

Generalized equations,variational inequalities and a weak Kantorovich theorem

We prove a Kantorovich-type theorem on the existence and uniqueness of the solution of a generalized equation of the form f(u)+g(u) ' 0f(u)+g(u)\owns 0 where f is a Fréchet-differentiable function and g is a maximal monotone operator defined on a Hilbert space. The depth and scope of this theorem is such that when we specialize it to nonlinear operator equations, variational inequalities and nonlinear complementarity problems we obtain novel results for these problems as well. Our approach to the solution of a generalized equation is iterative, and the solution is obtained as the limit of the solutions of partially linearized generalized Newton subproblems of the type Az+g(z) ' bAz+g(z)\owns b where A is a linear operator.     

An operator splitting method for nonlinear convection-diffusion equations

Summary. We present a semi-discrete method for constructing approximate solutions to the initial value problem for the -dimensional convection-diffusion equation . The method is based on the use of operator splitting to isolate the convection part and the diffusion part of the equation. In the case , dimensional splitting is used to reduce the -dimensional convection problem to a series of one-dimensional problems. We show that the method produces a compact sequence of approximate solutions which converges to the exact solution. Finally, a fully discrete method is analyzed, and demonstrated in the case of one and two space dimensions. ReceivedFebruary 1, 1996 / Revised version received June 24, 1996     

An application of generalized implicit function theorem to Goursat problems for nonlinear Leray-Volevich systems

Recently, Bramson proved a theorem that classifies the initial data under which solutions of the K-P-P equation converge to the appropriate travelling waves. In this paper, a simplified proof is given by using maximal principles instead of his Brownian motion approach. The regularity condition on the forcing term is also weakened.     

A generalized sub-equations rational expansion method for nonlinear evolution equations

In this paper, based on symbolic computation and the idea of rational expansion method, a generalized sub-equations rational expansion method (GSRE) is devised to uniformly construct a series of exact complexiton solutions for nonlinear evolution equations. Compared with most existing tanh function methods and other sophisticated methods, the proposed method not only recover some known solutions, but also find some new and general solutions which include many new types of complexiton solutions: the combination of hyperbolic (and square form) function and elliptic function, trigonometric (and square form) function and elliptic function. The efficiency of the method can be demonstrated on (2 + 1)-dimensional Burgers equations.     

An existence theorem for some nonlinear quasi-elliptic equations

Sunto In questo lavoro si prova l'esistenza di una soluzione periodica di classe C dell'equazione quasiellittica totalmente non lineare: v + F(D _x ⁴ v, Dsky/4v)=f.

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Lavoro eseguito nell'ambito del G.N.A.F.A. del C.N.R.     

A general multiplicity theorem for certain nonlinear equations in Hilbert spaces

In this paper, we prove the following general result. Let be a real Hilbert space and a continuously Gâteaux differentiable, nonconstant functional, with compact derivative, such that

Then, for each for which the set is not convex and for each convex set dense in , there exist and 0$"> such that the equation

has at least three solutions.