Positive solutions of discrete third-order three-point right focal boundary value problems

We consider linear and nonlinear boundary value problems for third-order difference equations with three-point right focal boundary conditions. In the linear case, the existence of positive solutions corresponding to the first eigenvalue of the problem is established and an interval estimate for the first eigenvalue is obtained. In the nonlinear case, sufficient conditions for the existence and nonexistence of positive solutions are obtained. An example is included at the end of the paper to illustrate the sharpness of our results.     

On the first eigenfunction of a perturbed Hardy-Sobolev operator

In this paper we study the existence, nonexistence and simplicity of the first eigenvalue of the Hardy-Sobolev operator under various assumptions on q. We will also analyse the singularity present in the first eigenfunction when with 0<s<1.     

Existence and nonexistence of global positive solutions for a weakly coupled P-Laplacian system

In this paper, we deal with a weakly coupled evolution P-Laplacian system with inhomogeneous terms. We obtain a critical criterion concerning existence and nonexistence of its global positive solutions. Such a criterion is different from that of the weakly coupled evolution P-Laplacian system with homogeneous terms. Further, we demonstrate existence and nonexistence of its global positive solutions.     

On positive solutions of eigenvalue problems for a class of \emph{p}-Laplacian fractional differential equations

In this paper, we are concerned with the eigenvalue problem of a class of \emph{p}-Laplacian fractional differential equations involving integral boundary conditions. New criteria are established for the existence of positive solutions of the problem under some superlinear and suberlinear conditions. The results of the existence of at least one, two and the nonexistence of positive solutions are also obtained by using the fixed point theory. Finally, several examples are provided to illustrate the obtained results.     

Nonlinear eigenvalue Neumann problems with discontinuities

In this paper we study nonlinear eigenvalue problems with Neumann boundary conditions and discontinuous terms. First we consider a nonlinear problem involving the p-Laplacian and we prove the existence of a solution for the multivalued approximation of it, then we pass to semilinear problems and we prove the existence of multiple solutions. The approach is based on the critical point theory for nonsmooth locally Lipschitz functionals.     

Verified computation of solutions for obstacle problems with guaranteed L∞ error bound

In this paper, we consider a numerical enclosure method with guaranteed L^∞ error bound for the solutions of obstacle problems. Using the finite-element approximations and the explicit a priori error estimates for obstacle problems, we present an effective verification procedure that automatically generates on a computer a set which includes the exact solution. A particular emphasis is that our method needs no assumption of the existence of the solution of the original obstacle problems, but it follows as the result of computation itself. A numerical example for an obstacle problem is presented.     

Multiple positive solutions of singular eigenvalue type problems involving the one-dimensional p-Laplacian

We establish a existence result of multiple positive solutions for a singular eigenvalue type problem involving the one-dimensional p-Laplacian. Furthermore, we obtain a nonexistence result of positive solutions by taking advantage of the internal geometric properties related to the problem. Our approach is based on the fixed point index theory and the fixed point theorem in cones.     

EXISTENCE AND NONEXISTENCE OF POSITIVE SOLUTIONS TO A THREE-POINT BOUNDARY VALUE PROBLEM

In this paper, we are concerned with the existence and nonexistence of positive solutions to a three-point boundary value problems. By Krasnoselskii’s fixed point theorem in Banach space, we obtain sufficient conditions for the existence and non-existence of positive solutions to the above three-point boundary value problems.     

On octahedral fulleroids

The discovery of the first fullerene has raised an interest in the study of other candidates for modelling of carbon molecules. As a generalization of the fullerenes, fulleroids are defined as cubic convex polyhedra with all the faces of size five or greater. In this paper, we give necessary and sufficient condition for the existence of fulleroids with only pentagonal and n-gonal faces and with the symmetry group isomorphic to the full symmetry group of the regular octahedron. The existence is proved by finding infinite series of examples. The nonexistence is proved using symmetry invariants.     

Entire radial solutions of elliptic systems and inequalities of the mean curvature type

In this paper we study first nonexistence of radial entire solutions of elliptic systems of the mean curvature type with a singular or degenerate diffusion depending on the solution u. In particular we extend a previous result given in [R. Filippucci, Nonexistence of radial entire solutions of elliptic systems, J. Differential Equations 188 (2003) 353-389]. Moreover, in the scalar case we obtain nonexistence of all entire solutions, radial or not, of differential inequalities involving again operators of the mean curvature type and a diffusion term. We prove that in the scalar case, nonexistence of entire solutions is due to the explosion of the derivative of every nonglobal radial solution in the right extremum of the maximal interval of existence, while in that point the solution is bounded. This behavior is qualitatively different with respect to what happens for the m-Laplacian operator, studied in [R. Filippucci, Nonexistence of radial entire solutions of elliptic systems, J. Differential Equations 188 (2003) 353-389], where nonexistence of entire solutions is due, even in the vectorial case, to the explosion in norm of the solution at a finite point. Our nonexistence theorems for inequalities extend previous results given by Naito and Usami in [Y. Naito, H. Usami, Entire solutions of the inequality div(A(|Du|)Du)?f(u), Math. Z. 225 (1997) 167-175] and Ghergu and Radulescu in [M. Ghergu, V. Radulescu, Existence and nonexistence of entire solutions to the logistic differential equation, Abstr. Appl. Anal. 17 (2003) 995-1003].     

Heisenberg群上带不确定权的p-次Laplacian特征值问题(英文)

本文讨论Heisenberg群上带不确定权的p-次Laplacian特征值问题解的存在性,并且证明相应的非负特征函数的第一特征值是单重的,孤立的和唯一的.     

An optimization problem for the first eigenvalue of the ‐fractional Laplacian

In this paper we analyze an eigenvalue problem related to the nonlocal p‐Laplace operator plus a potential. After reviewing some elementary properties of the first eigenvalue of these operators (existence, positivity of associated eigenfunctions, simplicity and isolation) we investigate the dependence of the first eigenvalue on the potential function and establish the existence of some optimal potentials in some admissible classes.     

Non existence of quasi-harmonic spheres

Let M and N be compact Riemannian manifolds. To prove the global existence and convergence of the heat flow for harmonic maps between M and N, it suffices to show the nonexistence of harmonic spheres and nonexistence of quasi-harmonic spheres. In this paper, we prove that, if the universal covering of N admits a nonnegative strictly convex function with polynomial growth, then there are no quasi-harmonic spheres nor harmonic spheres. This generalizes the famous Eells–Sampson’s theorem (Am J Math 86:109–169, [7]).     

Clifford Valued Weighted Variable Exponent Spaces with an Application to Obstacle Problems

In this paper, we introduce the weighted variable exponent spaces in the context of Clifford algebras. After discussing the properties of these spaces, we obtain the existence of weak solutions for obstacle problems for nondegenerate A-Dirac equations with variable growth in the setting of these spaces. Furthermore, we also obtain the existence and uniqueness of weak solutions to the scalar parts of nondegenerate A-Dirac equations in Dirac Sobolev spaces.     

Existence and regularity of maximal metrics for the first Laplace eigenvalue on surfaces

We investigate in this paper the existence of a metric which maximizes the first eigenvalue of the Laplacian on Riemannian surfaces. We first prove that, in a given conformal class, there always exists such a maximizing metric which is smooth except at a finite set of conical singularities. This result is similar to the beautiful result concerning Steklov eigenvalues recently obtained by Fraser and Schoen (Sharp eigenvalue bounds and minimal surfaces in the ball, 2013). Then we get existence results among all metrics on surfaces of a given genus, leading to the existence of minimal isometric immersions of smooth compact Riemannian manifold (M, g) of dimension 2 into some k-sphere by first eigenfunctions. At last, we also answer a conjecture of Friedlander and Nadirashvili (Int Math Res Not 17:939–952, 1999) which asserts that the supremum of the first eigenvalue of the Laplacian on a conformal class can be taken as close as we want of its value on the sphere on any orientable surface.     

2p和2q阶微分方程组正解的存在性

利用拓扑度乘积理论研究2p和2q阶非线性高阶微分方程组边值问题,通过相应的线性问题的第一特征值和拓扑度乘积理论建立了其正解的存在性定理,给出了利用特征值刻划的较为本质的结果,且突破了以往文献要求的方程组同阶和非线性项同是次线性或超线性的要求.     

Two periodic solutions of n-dimensional neutral functional difference systems

In this paper, we establish existence, multiplicity and nonexistence of periodic solutions for a class of first-order n-dimensional neutral functional difference systems. Our approach requires the Krasnoselskii fixed point theorem in cones.     

Positive solutions of an elliptic partial differential equation on R

In this paper, we discuss the existence, nonexistence and uniqueness of positive solutions of a one-parameter family of elliptic partial differential equations on R^N (N>2). These equations are of interests in mathematical biology and Riemannian geometry. Our approach are based on variational arguments and comparison principles.     

Fourth order wave equations with nonlinear strain and source terms

In this paper we study the initial boundary value problem for fourth order wave equations with nonlinear strain and source terms. First we introduce a family of potential wells and prove the invariance of some sets and vacuum isolating of solutions. Then we obtain a threshold result of global existence and nonexistence. Finally we discuss the global existence of solutions for the problem with critical initial condition I(u₀)?0, E(0)=d. So the Esquivel-Avila's results are generalized and improved.     

Positive Solutions for a Lotka–Volterra Prey–Predator Model with Cross-Diffusion of Fractional Type

In this paper we consider a Lotka–Volterra prey–predator model with cross-diffusion of fractional type. The main purpose is to discuss the existence and nonexistence of positive steady state solutions of such a model. Here a positive solution corresponds to a coexistence state of the model. Firstly we study the stability of the trivial and semi-trivial solutions by analyzing the principal eigenvalue of the corresponding linearized system. Secondly we derive some necessary conditions to ensure the existence of positive solutions, which demonstrate that if the intrinsic growth rate of the prey is too small or the death rate (or the birth rate) of the predator is too large, the model does not possess positive solutions. Thirdly we study the sufficient conditions to ensure the existence of positive solutions by using degree theory. Finally we characterize the stable/unstable regions of semi-trivial solutions and coexistence regions in parameter plane.