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Let $M^n$ be a n-dimensional compact manifold, with $n\geq3$. For any conformal class C of riemannian metrics on M, we set $\mu_k^c(M,C)=\inf_{g\in C}\mu_{[\frac n2],k}(M,g)\Vol(M,g)^{\frac2n}$, where $\mu_{p,k}(M,g)$ is the k-th eigenvalue…

微分几何 · 数学 2007-06-13 Pierre Jammes

Let (M,J) be a minimal compact complex surface of Kaehler type. It is shown that the smooth 4-manifold M admits a Riemannian metric of positive scalar curvature iff (M,J) admits a KAEHLER metric of positive scalar curvature. This extends…

dg-ga · 数学 2008-02-03 Claude LeBrun

Index expectation curvature K(x) = E[i_f(x)] on a compact Riemannian 2d-manifold M is the expectation of Poincare-Hopf indices i_f(x) and so satisfies the Gauss-Bonnet relation that the interval of K over M is Euler characteristic X(M).…

微分几何 · 数学 2020-01-22 Oliver Knill

We study an eigenvalue problem for the Laplacian on a compact K\"{a}hler manifold. Considering the $k$-th eigenvalue $\lambda_{k}$ as a functional on the space of K\"{a}hler metrics with fixed volume on a compact complex manifold, we…

微分几何 · 数学 2024-11-27 Kazumasa Narita

We revisit Brunella's proof of the fact that Kato surfaces admit locally conformally K\" ahler metrics, and we show that it holds for a large class of higher dimensional complex manifolds containing a global spherical shell. On the other…

代数几何 · 数学 2019-06-27 Nicolina Istrati , Alexandra Otiman , Massimiliano Pontecorvo

This paper proves that the universal covering of a compact K\"{a}hler manifold with small positive sectional curvature in a certain sense is contractible.

微分几何 · 数学 2025-02-20 Yuguang Zhang

We study conditions for which the mapping torus of a 6-manifold endowed with an $SU(3)$-structure is a locally conformal calibrated $G_2$-manifold, that is, a 7-manifold endowed with a $G_2$-structure $\varphi$ such that $d \varphi = -…

微分几何 · 数学 2015-11-02 Marisa Fernández , Anna Fino , Alberto Raffero

We show that if $(M,\omega)$ is any compact K\"ahler manifold, then the blowup of $M$ at any point furnishes a K\"ahler metric with scalar curvature globally and arbitrarily $C^0$-close to the scalar curvature of $\omega$. It follows that…

微分几何 · 数学 2026-01-28 Garrett M. Brown

The flag curvature is a natural Finsler extension of the sectional curvature in Riemannian geometry. However, there are many non-Riemannian quantities which interact with the flag curvature. In this paper, we introduce a notion of weighted…

微分几何 · 数学 2025-06-19 Zhongmin Shen , Runzhong Zhao

We characterize manifolds which are locally conformally equivalent to either complex projective space or to its negative curvature dual in terms of their Weyl curvature tensor. As a byproduct of this investigation, we classify the…

微分几何 · 数学 2015-06-26 N. Blazic , P. Gilkey

Our main result asserts that for any given numbers C and D the class of simply connected closed smooth manifolds of dimension m<7 which admit a Riemannian metric with sectional curvature bounded in absolute value by C and diameter uniformly…

微分几何 · 数学 2007-05-23 Wilderich Tuschmann

We show that a closed almost K\"ahler 4-manifold of globally constant holomorphic sectional curvature $k\geq 0$ with respect to the canonical Hermitian connection is automatically K\"ahler. The same result holds for $k<0$ if we require in…

微分几何 · 数学 2017-09-18 Mehdi Lejmi , Markus Upmeier

I present a selection of results on locally conformally K\"ahler geometry published after 1997. The proofs are mainly sketched, some of them are even omitted. Several open problems are indicated in the end.

微分几何 · 数学 2007-05-23 Liviu Ornea

We obtain a locally symmetric Kaehler Einstein structure on a tube in the nonzero cotangent bundle of a Riemannian manifold of positive constant sectional curvature. The obtained Kaehler Einstein structure cannot have constant holomorphic…

微分几何 · 数学 2007-05-23 D. D. Porosniuc

Suppose $\bar{M}$ is a compact connected odd-dimensional manifold with boundary, whose interior $M$ comes with a complete hyperbolic metric of finite volume. We will show that the $L^2$-topological torsion of $\bar{M}$ and the…

dg-ga · 数学 2018-11-28 Wolfgang Lueck , Thomas Schick

We prove a local well-posedness theorem for the (n+1)-dimensional Einstein equations in Lorentzian signature, with initial data $(\tilde g, K)$ whose asymptotic geometry at infinity is similar to that anti-de Sitter (AdS) space, and…

偏微分方程分析 · 数学 2017-01-19 Alberto Enciso , Niky Kamran

Let M be an almost Hermitian manifold of dimension greater or equal to 6. The following theorems are proved: Theorem 1. If M is of pointwise constant {\theta}-holomorphic sectional curvature for a number {\theta} in (0,{\pi}/2) then M is of…

微分几何 · 数学 2010-09-15 Ognian Kassabov

Is a sequence of Riemannian manifolds with positive scalar curvature, satisfying some conditions to keep the sequence reasonable, compact? What topology should one use for the convergence and what is the regularity of the limit space? In…

微分几何 · 数学 2024-06-07 Brian Allen , Wenchuan Tian , Changliang Wang

We study left-invariant locally conformally K\"ahler structures on Lie groups, or equivalently, on Lie algebras. We give some properties of these structures in general, and then we consider the special cases when its complex structure is…

微分几何 · 数学 2020-04-06 Adrián Andrada , Marcos Origlia

A classical question in spectral geometry is, for each pair of nonnegative integers $(p,n)$ such that $p\leq 2n$, if the eigenvalues of Laplacian on $p$-forms of a compact K\"{a}hler manifold are the same as those of $\mathbb{C}P^n$…

微分几何 · 数学 2018-10-17 Ping Li
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