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We give a characterization of the $2$-step nilpotent Lie algebras whose corresponding Lie groups admit a left invariant complex structure. This is done by considering separately the cases when the complex structure is 2-step or 3-step…

Differential Geometry · Mathematics 2025-08-11 Maria Laura Barberis

We analyze the structure of the set of limiting Carleman weights in all conformally flat manifolds, 3-manifolds, and 4-manifolds. In particular we give a new proof of the classification of Euclidean limiting Carleman weights, and show that…

Analysis of PDEs · Mathematics 2018-11-07 Pablo Angulo-Ardoy , Daniel Faraco , Luis Guijarro , Mikko Salo

We show that for $n>2$ a compact locally conformally K\"ahler manifold $(M^{2n},g,J)$ carrying a non-trivial parallel vector field is either Vaisman, or globally conformally K\"ahler, determined in an explicit way by some compact K\"ahler…

Differential Geometry · Mathematics 2017-01-20 Andrei Moroianu

An almost complex torus manifold is a $2n$-dimensional compact connected almost complex manifold equipped with an effective action of a real $n$-dimensional torus $T^n \simeq (S^1)^n$ that has fixed points. For an almost complex torus…

Algebraic Topology · Mathematics 2024-04-30 Donghoon Jang , Jiyun Park

An action of a torus T on a manifold M is locally standard if, at each point, the stabilizer is a sub-torus and the non-zero isotropy weights are a basis to its weight lattice. The quotient M/T is then a manifold-with-corners, decorated by…

Geometric Topology · Mathematics 2025-07-22 Yael Karshon , Shintaro Kuroki

We identify the holomorphic de Rham complex of the minimal extension of a meromorphic vector bundle with connexion on a compact Riemann surface X with the L^2 complex relative to a suitable metric on the bundle and a complete metric on the…

Algebraic Geometry · Mathematics 2007-05-23 Claude Sabbah

We study compact complex 3-manifolds admitting holomorphic Riemannian metrics. We prove a uniformization result: up to a finite unramified cover, such a manifold admits a holomorphic Riemannian metric of constant sectionnal curvature.

Differential Geometry · Mathematics 2007-10-25 Sorin Dumitrescu , Abdelghani Zeghib

We give criterions for the existence of toric conical Kahler-Einstein and Kahler-Ricci soliton metrics on any toric manifold in relation to the greatest Ricci and Bakry-Emery-Ricci lower bound. We also show that any two toric manifolds with…

Differential Geometry · Mathematics 2013-09-02 Ved Datar , Bin Guo , Jian Song , Xiaowei Wang

For a proper action by a locally compact group $G$ on a manifold $M$ with a $G$-equivariant Spin-structure, we obtain obstructions to the existence of complete $G$-invariant Riemannian metrics with uniformly positive scalar curvature. We…

Differential Geometry · Mathematics 2024-09-02 Hao Guo , Peter Hochs , Varghese Mathai

The Leit-Faden of the article (which is partially a survey) is a negative answer to the question whether, for a compact complex manifold which is a $K(\pi, 1)$ the diffeomorphism type determines the deformation type. We show that a…

Algebraic Geometry · Mathematics 2007-05-23 Fabrizio M. E. Catanese

We prove that any left-invariant symplectic almost complex structure on a Thurston manifold which is compatible with its canonical left-invariant Riemannian metric has holomorphic type 1.

Complex Variables · Mathematics 2016-11-11 Oleg Mushkarov , Christian L. Yankov

The group SU(2)*SU(2) acts naturally on SL(2,C) by simultaneous right and left multiplication. We study the Kahler metrics invariant under this action using global Kahler potentials. The volume growth and various curvature quantities are…

Mathematical Physics · Physics 2016-09-07 J. M. Baptista

In this work it is shown that a necessary condition for the completeness of the geodesics of left invariant pseudo-Riemannian metrics on Lie groups is also sufficient in the case of 3-dimensional unimodular Lie groups, and not sufficient…

Differential Geometry · Mathematics 2008-12-18 Shirley Bromberg , Alberto Medina

We investigate quantitative properties of exact locally conformally symplectic (LCS) manifolds, namely the homotheties of the Lee form that still produce an exact LCS form. This gives the notion of elasticity of an exact LCS pair. Using…

Symplectic Geometry · Mathematics 2025-11-21 Pacôme Van Overschelde

Motivated by the recent work of Wu and Yau on the ampleness of canonical line bundle for compact K\"ahler manifolds with negative holomorphic sectional curvature, we introduce a new curvature notion called $\textbf{real bisectional…

Differential Geometry · Mathematics 2023-03-31 Xiaokui Yang , Fangyang Zheng

In the focus of our paper is a system of axioms that serves as a basis for introducing structural data for $(2n,k)$-manifolds $M^{2n}$, where $M^{2n}$ is a smooth, compact $2n$-dimensional manifold with a smooth effective action of the…

Algebraic Topology · Mathematics 2019-09-04 Victor M. Buchstaber , Svjetlana Terzic

We prove that if a Calabi--Yau manifold $M$ admits a holomorphic Cartan geometry, then $M$ is covered by a complex torus. This is done by establishing the Bogomolov inequality for semistable sheaves on compact K\"ahler manifolds. We also…

Algebraic Geometry · Mathematics 2010-09-30 Indranil Biswas , Benjamin McKay

Consider an effective Hamiltonian torus action $T\times M \to M$ on a topologically twisted,generalized complex manifold $M$ of dimension $2n$. We prove that the $rank(T) \leq n-2$ and that the topological twisting survives Hamiltonian…

Differential Geometry · Mathematics 2014-02-26 Thomas Baird , Yi Lin

Let (M,I) be a compact Kaehler manifold admitting a hypercomplex structure. We show that (M, I) admits a natural HKT-metric. This is used to construct a holomorphic symplectic form on (M,I).

Algebraic Geometry · Mathematics 2007-05-23 Misha Verbitsky

We prove that the Euler characteristic of an even-dimensional compact manifold with positive (nonnegative) sectional curvature is positive (nonnegative) provided that the manifold admits an isometric action of a compact Lie group $G$ with…

Differential Geometry · Mathematics 2012-07-18 Thomas Puettmann , Catherine Searle