Time-Harmonic Solutions for Maxwell’s Equations in Anisotropic Media and Bochner–Riesz Estimates with Negative Index for Non-elliptic Surfaces

Entire solutions of sublinear elliptic equations in anisotropic media

We study the nonlinear elliptic problem −∆u = ρ(x)f(u) in R (N ≥ 3), lim|x|→∞ u(x) = l, where l ≥ 0 is a real number, ρ(x) is a nonnegative potential belonging to a certain Kato class, and f(u) has a sublinear growth. We distinguish the cases l > 0 and l = 0 and we prove existence and uniqueness results if the potential ρ(x) decays fast enough at infinity. Our arguments rely on comparison techn...

Eigenvalue Problems for Degenerate Nonlinear Elliptic Equations in Anisotropic Media

We study nonlinear eigenvalue problems of the type −div(a(x)∇u) = g(λ,x,u) in RN , where a(x) is a degenerate nonnegative weight. We establish the existence of solutions and we obtain information on qualitative properties as multiplicity and location of solutions. Our approach is based on the critical point theory in Sobolev weighted spaces combined with a Caffarelli-Kohn-Nirenberg-type inequal...

Analytic solutions for the Stephen's inverse problem with local boundary conditions including Elliptic and hyperbolic equations

In this paper, two inverse problems of Stephen kind with local (Dirichlet) boundary conditions are investigated. In the first problem only a part of boundary is unknown and in the second problem, the whole of boundary is unknown. For the both of problems, at first, analytic expressions for unknown boundary are presented, then by using these analytic expressions for unknown boundaries and bounda...

Gradient Estimates for Weak Solutions of A-Harmonic Equations

A Priori Estimates of Positive Solutions for Sublinear Elliptic Equations

In this paper, a priori estimates of positive solutions for sublinear elliptic equations are given in terms of thicknesses of domains. To this end, a supersolution is constructed by a composite function of a solution to an ordinary differential equation and a distance function. The results work efficiently in the case where the domain is an exterior or an interior of a convex set.