Interior Boundaries for Degenerate Elliptic Equations of Second Order Some Theory and Numerical Observations

2010 Mathematics Subject Classification: Primary 35J70; Secondary 35J15, 35D05.For boundary value problems for degenerate-elliptic equations of second order in ⊂ Rn there are cases when a closed surface exists, dividing into two subdomains in such a manner that two new correct boundary value problems can be formulated without introducing new boundary conditions. Such surfaces are called interior boundaries. Some theoretical results regarding the connections between the solutions of the original problem and the two new problems are given. Some numerical experiments using the finite elements method are carried out trying to visualize the effects of the presence of such interior boundary when n = 2. Also some more precise study of the solutions in the case n = 2 is presented

A study on gradient blow up for viscosity solutions of fully nonlinear, uniformly elliptic equations

We investigate sharp conditions for boundary and interior gradient es- timates of continuous viscosity solutions to fully nonlinear, uniformly ellip- tic equations under Dirichlet boundary conditions. When these conditions are violated, there can be blow up of the gradient in the interior or on the boundary of the domain

New Hardy-Type Inequalities with Singular Weights

2010 Mathematics Subject Classification: 26D10.We prove a new Hardy–type inequality with weights that are possibly singular at internal point and on the boundary of the domain. As an illustration some applications and examples are given

On Principle Eigenvalue for Linear Second Order Elliptic Equations in Divergence Form

2002 Mathematics Subject Classification: 35J15, 35J25, 35B05, 35B50The principle eigenvalue and the maximum principle for second-order elliptic equations is studied. New necessary and sufficient conditions for symmetric and nonsymmetric operators are obtained. Applications for the estimation of the first eigenvalue are given

Theoretical study of nonlinear wave equations with combined power-type nonlinearities with variable coefficients

In this paper, we study the initial boundary value problem for the nonlinear wave equation with combined power-type nonlinearities with variable coefficients. The global behavior of the solutions with non-positive and sub-critical energy is completely investigated. The threshold between the nonexistence of global in time weak solutions and non-blowing up solutions is found. For super-critical energy, two new sufficient conditions guaranteeing nonexistence of global in time solutions are given. One of them is proved for arbitrary sign of the scalar product of the initial data, while the other one is derived only for positive sign. Uniqueness and existence of local weak solutions are proved.Comment: 33 page

The Asymptotic Behaviour of the First Eigenvalue of Linear Second-Order Elliptic Equations in Divergente Form

2000 Mathematics Subject Classification: 35J70, 35P15.The asymptotic of the first eigenvalue for linear second order elliptic equations in divergence form with large drift is studied. A necessary and a sufficient condition for the maximum possible rate of the first eigenvalue is proved