null

We present recent existence results of Cantor families of small amplitude periodic solutions for completely resonant nonlinear wave equations. The proofs rely on the Nash-Moser implicit function theory and variational methods.

Hamiltonian systems with various time boundary conditions are formulated as absolute minima of newly devised non-negative action functionals obtained by a generalization of Bogomolnyi’s trick of ‘completing squares’. Reminiscent of the selfdual Yang-Mills equations, they are not derived from the fact that they are critical points (i.e., from the corresponding Euler-Lagrange equations) but from being zeroes of the corresponding non-negative Lagrangians. A general method for resolving such variational problems is also described and applied to the construction of periodic solutions for Hamiltonian systems, but also to study certain Lagrangian intersections.

Using the Hamiltonian identities and the corresponding Hamiltonian constants for entire solutions of elliptic partial differential equations, we investigate several new entire solutions whose existence were shown recently, and sh

In this survey, we will summarize the existence results of nonlinear partial differential equations which arises from geometry or physics by using variational method. We use the method to study Kazdan-Warner problem, Chern-Simons-Higgs model, Toda systems, and the prescribed Q-curvature problem in 4-dimension.

In this survey article, we recall some known results on existence and multiplicity of sign-changing solutions of elliptic equations. Methods for obtaining sign-changing solutions developed in the last two decades will also be brief

We study singularly perturbed elliptic equations arising from models in physics or biology, and investigate the asymptotic behavior of some special solutions. We also discuss some connections with problems arising in differential g

We show the existence of at least two geometrically distinct closed geodesics on a complex projective plane with a bumpy and non-reversible Finsler metric.

This collection of problems is based on the Problem Section held on May 24, 2007 during the International Conference on Variational Methods. These problems reflect various aspects of variational methods and are due to Professors Victor Bangert, Alain Chenciner, Ivar Ekeland, Nassif Ghoussoub, Zhaoli Liu, Paul Rabinowitz and Hans-Bert Rademacher.

The goal of this article is to survey new results on the recognition problem. We focus our attention on the methods recently developed in this area. In each section, we formulate related open problems. In the last two sections, we review arithmetical characterization of spectra of finite simple groups and conclude with a list of groups for which the recognition problem was solved within the last three years.

In this paper, we investigate the long-range dependence of fractional Levy processes on Gel’fand triple and construct stochastic integral with respect to fractional Levy processes for a class of deterministic integrands.

Let E and F be Banach spaces, f : U ⊂ E → F be a map of C^r (r ≥ 1), x₀ ? U, and f′(x₀) denote the Frechet differential of f at x₀. Suppose that f′(x₀) is double split, Rank(f′(x₀)) = ∞, dimN(f′(x₀)) > 0 and codimR(f′(x₀)) > 0. The rank theorem in advanced calculus asks to answer what properties of f ensure that f(x) is conjugate to f′(x₀) near x₀. We have proved that the conclusion of the theorem is equivalent to one kind of singularities for bounded linear operators, i.e., x₀ is a locally fine point for f′(x) or generalized regular point of f(x); so, a complete rank theorem in advanced calculus is established, i.e., a sufficient and necessary condition such that the conclusion of the theorem to be held is given.