The Chern Conjecture for Affinely Flat Manifolds Using Combinatorial Methods

An affine manifold is a manifold with a flat affine structure, i.e. a torsion-free flat affine connection. We slightly generalize the result of Hirsch and Thurston that if the holonomy of a closed affine manifold is isomorphic to amenable groups amalgamated or HNN-extended along finite groups, then the Euler characteristic of the manifold is zero confirming an old conjecture of Chern. The technique is from Kim and Lee's work using the combinatorial Gauss–Bonnet theorem and taking the means of the angles by amenability. We show that if an even-dimensional manifold is obtained from a connected sum operation from K(, 1)s with amenable fundamental groups, then the manifold does not admit an affine structure generalizing a result of Smillie.     

A NEW FORMULA WITHOUT BOUNDARY INTEGRALS ON A STEIN MANIFOLD

A new Koppelman-Leray-Norguet formula of (p-1,q) differential forms for a strictly pseudoconvex polyhedron with not necessarily smooth boundary on a Stein manifold is obtained, and an integral representation for the solution of (?)-equation on this domain which does not involve integrals on boundary is given, so one can avoid complex estimates of boundary integrals.     

Two Special Simply Connected Spaces of Nonpositive Curvature

We construct two examples of spaces homeomorphic to R ⁿ (n3) each of which has a closed geodesic and admits no isoperimetric inequality. The first is a complete polyhedral metric space of nonpositive curvature, and the second is an incomplete Riemannian space with nonpositive sectional curvatures.     

of Hamiltonian manifolds

Let be a connected, compact symplectic manifold equipped with a Hamiltonian action. We prove that, as fundamental groups of topological spaces, , where is the symplectic quotient at any value in the image of the moment map .

     

Proper actions on cohomology manifolds

Essential results about actions of compact Lie groups on connected manifolds are generalized to proper actions of arbitrary groups on connected cohomology manifolds. Slices are replaced by certain fiber bundle structures on orbit neighborhoods. The group dimension is shown to be effectively finite. The orbits of maximal dimension form a dense open connected subset. If some orbit has codimension at most , then the group is effectively a Lie group.

     

Positive and negative 3-K-contact structures

The aim of this paper is to give a characterization of 3-K-contact and quasi 3-K-contact manifolds.

     

Necessary and sufficient conditions for s-Hopfian manifolds to be codimension-2 fibrators

Fibrators help detect approximate fibrations. A closed, connected -manifold is called a codimension-2 fibrator if each map defined on an -manifold such that all fibre , are shape equivalent to is an approximate fibration. The most natural objects to study are s-Hopfian manifolds. In this note we give some necessary and sufficient conditions for s-Hopfian manifolds to be codimension-2 fibrators.

     

关于调和映照的一个 Liouville型定理

本文证明了完备非紧 Riemann流形 M,若其上不存在非常数、具有限 Dirichlet积分的调和函数 , 则从 M出发到任何 C-H流形的具有限能量的调和映照必为常值映照.     

THE HEAT FLOWOF HARMONIC MAPS FROM NONCOMPACT MANIFOLDS

1.IntroductionLetMandNbetwoRiemannianmanifoldsofdimensionmandn.Supposetheirmetricsaregivenbydski~giid-c'dxianddsX~h.odu"duo.Letu:M~Nbeasmoothmap.Theenergydensityfunctionofuisgivenbye(u)~g'jCZh.,~Ical'.ThetotalenergyisdefinedbyE(u)=[e(u)dx.iMAmappingu:M~NiscalledaharmonicmapifitisaclassicalsolutionoftheEulerLagrangeequationofE(u)whichcanbewrittenasT"(U(X))~AU"(X) r3.(U(X))ZZg.j~0,whereT(u)iscalledthetensionfieldofu.Thecorrespondingparabolicsystemwithinitialdata"o(x)knownastheheatequ…     

Large volume growth and finite topological type

It is shown in this paper that a complete noncompact -dimensional Riemannian manifold with nonnegative Ricci curvature, sectional curvature bounded from below, and large volume growth is of finite topological type provided that the volume growth rate of the complement of the cone of rays from a fixed base point is less than .