نتایج جستجو برای: compact base manifolds
تعداد نتایج: 373396 فیلتر نتایج به سال:
If a closed smooth n-manifold M admits a finite cover M̂ whose Z/2Z-cohomology has the maximal cup-length, then for any riemannian metric g on M , we show that the systole Sys(M, g) and the volume Vol(M, g) of the riemannian manifold (M, g) are related by the following isosystolic inequality: Sys(M, g) n ≤ n!Vol(M, g). The inequality can be regarded as a generalization of Burago and Hebda’s ineq...
Building on previous results [17, 35], we complete the classification of compact oriented Einstein 4-manifolds with $$\det (W^+) > 0$$ . There are, up to diffeomorphism, exactly 15 manifolds that carry such metrics, and, each these manifolds, metrics sweep out one connected component corresponding moduli space.
There has always been a lack of examples of compact manifolds which are minimal sets under the action of the real line, minimal meaning that each orbit is dense in the manifold. All tori admit such an action and G. A. Hedlund [4] has given examples of 3-manifolds having such an action. The action of a group T on a metric space X is said to be distal if for any two distinct points x, y&X the dis...
Let (X, ωX) be a compact Kähler manifold such that the anticanonical bundle −KX is nef. We prove that the slopes of the HarderNarasimhan filtration of the tangent bundle with respect to a polarization of the form ω X are semi-positive. As an application, we give a characterization of rationally connected compact Kähler manifolds with nef anticanonical bundles. As another application, we give a ...
We investigate conditions under which a co-computably enumerable closed set in a computable metric space is computable and prove that in each locally computable computable metric space each co-computably enumerable compact manifold with computable boundary is computable. In fact, we examine the notion of a semi-computable compact set and we prove a more general result: in any computable metric ...
Let M be a smooth compact oriented Riemannian manifold, and let ∆M be the Laplace-Beltrami operator on M. Say 0 6= f ∈ S(R), and that f(0) = 0. For t > 0, let Kt(x, y) denote the kernel of f(t∆M). We show that Kt is well-localized near the diagonal, in the sense that it satisfies estimates akin to those satisfied by the kernel of the convolution operator f(t∆) on R. We define continuous S-wavel...
Among the compact homogeneous spaces, a very distinguished subclass is formed by the (generalized) real flag manifolds which by definition are the orbits of the isotropy representations of Riemannian symmetric spaces (sorbits). This class contains most compact symmetric spaces (e.g. all hermitian ones), all classical flag manifolds over real, complex and quaternionic vector spaces, all adjoint ...
According to Lerman, compact connected toric contact 3-manifolds with a non-free toric action whose moment cone spans an angle greater than π are overtwisted, thus non-fillable. In contrast, we show that all compact connected toric contact manifolds in dimension greater than three are weakly symplectically fillable and most of them are strongly symplectically fillable. The proof is based on the...
In this paper we describe our current research in the theory of partial differential equations in conformal geometry. We introduce a bubble tree structure to study the degeneration of a class of Yamabe metrics on Bach flat manifolds satisfying some global conformal bounds on compact manifolds of dimension 4. As applications, we establish a gap theorem, a finiteness theorem for diffeomorphism ty...
Let M be an orientable compact flat Riemannian manifold endowed with a spin structure. In this paper we determine the spectrum of Dirac operators acting on smooth sections of twisted spinor bundles of M , and we derive a formula for the corresponding eta series. In the case of manifolds with holonomy group Z2 , we give a very simple expression for the multiplicities of eigenvalues that allows t...
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