Front. Math. China All Journals

Jun 2008, Volume 3 Issue 2

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  • Progress in variational methods
    Yiming Long
  • Cantor families of periodic solutions for completely resonant wave equations
    Massimiliano Berti, Philippe Bolle

    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 as selfdual equations
    Nassif Ghoussoub

    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 ‘dcompleting 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.

  • Hamiltonian constants for several new entire solutions
    Changfeng Gui

    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 show interesting properties of the solutions such as formulas for contact angles at infinity of concentration curves.

  • Variational approach to various nonlinear problems in geometry and physics
    Jiayu Li

    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.

  • Sign-changing solutions of nonlinear elliptic equations
    Zhaoli Liu, Zhi-Qiang Wang

    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 briefly revisited.

  • Concentrating solutions of some singularly perturbed elliptic equations
    Andrea Malchiodi

    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 geometry.

  • The second closed geodesic on a complex projective plane
    Hans-Bert Rademacher

    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.

  • Collection of problems proposed at International Conference on Variational Methods
    Yiming Long

    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.

  • Recognition by spectrum for finite simple groups of Lie type
    Maria A. Grechkoseeva, Wujie Shi, Andrey V. Vasilev

    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.

  • Fractional Lévy processes on Gel’fand triple and stochastic integration
    Xuebin Lü, Zhiyuan Huang, Jianping Wan

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

  • Complete rank theorem of advanced calculus and singularities of bounded linear operators
    Jipu Ma

    Let E and F be Banach spaces, f: UEF be a map of Cr (r ⩾ 1), x0U, and ft (x0) denote the FréLechet differential of f at x0. Suppose that f′(x0) is double split, Rank(f′(x0)) = ∞, dimN(f′(x 0)) > 0 and codimR(f′(x0)) s> 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.