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Austere submanifolds of Euclidean space were introduced in 1982 by Harvey and Lawson in their foundational work on calibrated geometries. In general, the austerity condition is much stronger than minimality since it express that the nonzero…

Differential Geometry · Mathematics 2019-02-26 M. Dajczer , Th. Vlachos

We develop a general structure theory for compact homogeneous Riemannian manifolds in relation to the co-index of symmetry. We will then use these results to classify irreducible, simply connected, compact homogeneous Riemannian manifolds…

Differential Geometry · Mathematics 2013-12-23 Jurgen Berndt , Carlos Olmos , Silvio Reggiani

Campana introduced the class of special varieties as the varieties admitting no Bogomolov sheaves i.e. rank one coherent subsheaves of maximal Kodaira dimension in some exterior power of the cotangent bundle. Campana raised the question if…

Algebraic Geometry · Mathematics 2021-06-24 Jorge Vitorio Pereira , Erwan Rousseau , Frédéric Touzet

Based on work of R. Lazarsfeld and M. Popa, we use the derivative complex associated to the bundle of the holomorphic p-forms to provide inequalities for all the Hodge numbers of a special class of irregular compact Kaehler manifolds. For…

Algebraic Geometry · Mathematics 2012-04-06 Luigi Lombardi

Given a polarized variety $(X,L)$, we construct and study projections of low degree $ X\dashrightarrow \mathbb{P}(H^0(L^\vee)) \dashrightarrow \mathbb P ^n $ using the associated kernel bundles. As an application, we can show that the…

Algebraic Geometry · Mathematics 2025-06-05 Federico Moretti

On a compact K\"ahler manifold, we introduce a notion of almost nonpositivity for the holomorphic sectional curvature, which by definition is weaker than the existence of a K\"ahler metric with semi-negative holomorphic sectional curvature.…

Differential Geometry · Mathematics 2020-11-12 Yashan Zhang

We study Kahler manifolds-with-boundary, not necessarily compact, with weakly pseudoconvex boundary, each component of which is compact. If such a manifold $K$ has $l\ge2$ boundary components (possibly $l=\infty$), then it has first betti…

Differential Geometry · Mathematics 2018-10-12 Brian Weber

Geometry of manifolds with positive sectional curvature has been a central object dates back to the beginning of Riemannian geometry. Up to homeomorphism, there are only finitely many examples of simply connected positively curved manifolds…

Differential Geometry · Mathematics 2024-10-11 Fuquan Fang , Wen Shen

In this survey we discuss the problem of the existence of rational curves on complex surfaces, both in the K\"ahler and non-K\"ahler setup. We systematically go through the Enriques--Kodaira classification of complex surfaces to highlight…

Algebraic Geometry · Mathematics 2023-04-06 Giuseppe Barbaro , Filippo Fagioli , Ángel David Ríos Ortiz

Motivated by a general question addressed by Mario Baldassarri in 1956, we discuss characterizations of the Pseudo-Abelian Varieties introduced by Roth, and we introduce a first new notion, of Manifolds Isogenous to a k-Torus Product: the…

Algebraic Geometry · Mathematics 2025-02-07 Fabrizio Catanese

In this paper, motivated by a problem posed by Barry Mazur, we show that for smooth projective varieties over the rationals, the odd cohomology groups of degree less than or equal to the dimension can be modeled by the cohomology of an…

Algebraic Geometry · Mathematics 2019-02-20 Jeff Achter , Sebastian Casalaina-Martin , Charles Vial

Polyfold theory was developed by Hofer-Wysocki-Zehnder by finding commonalities in the analytic framework for a variety of geometric elliptic PDEs, in particular moduli spaces of pseudoholomorphic curves. It aims to systematically address…

Symplectic Geometry · Mathematics 2016-11-23 Oliver Fabert , Joel W. Fish , Roman Golovko , Katrin Wehrheim

We classify K\"ahler-Einstein manifolds which admit a K\"ahler immersion into a finite dimensional complex projective space endowed with the Fubini-Study metric, whose codimention is not greater than 3 and whose metric is rotation…

Differential Geometry · Mathematics 2016-12-06 Filippo Salis

We classify these threefolds, which are the ones such that their universal cover is not compact and not covered by positive-dimensional compact analytic subsets. We show that these threefolds have nonnegative Kodaira dimension, and that…

Algebraic Geometry · Mathematics 2007-05-23 F. Campana , Q. Zhang

After R.~Schoen completed the solution to the Yamabe problem, compact manifolds could be categorized into three classes, depending on whether they admit a metric with positive, non-negative, or only negative scalar curvature. Here we follow…

Differential Geometry · Mathematics 2023-05-16 Leonardo F. Cavenaghi , João Marcos do Ó , Llohann D. Sperança

In this paper we classify low degree del Pezzo orbifolds with irreducible boundaries. In order to achieve desired boundaries, we classify low degree curves on low degree del Pezzo surfaces. The notion of Campana orbifolds was introduced by…

Algebraic Geometry · Mathematics 2026-01-30 Saptarshi Dandapat

The aim of these notes is to acquaint the reader with important objects in complex algebraic geometry: K3 surfaces and their higher-dimensional analogs, hyperk\"ahler manifolds. These manifolds are interesting from several points of view:…

Algebraic Geometry · Mathematics 2020-11-18 Olivier Debarre

We study cohomological properties of complex manifolds. In particular, under suitable metric conditions, we extend to higher dimensions a result by A. Teleman, which provides an upper bound for the Bott-Chern cohomology in terms of Betti…

Differential Geometry · Mathematics 2019-12-23 Daniele Angella , Adriano Tomassini , Misha Verbitsky

Complex supermanifold structures being deformations of the exterior algebra of a holomorphic vector bundle, have been parametrized by orbits of a group on non-abelian cohomology by P. Green. For the case of odd dimension $4$ and $5$ an…

Complex Variables · Mathematics 2016-01-28 Matthias Kalus

Given a general polarized $K3$ surface $S\subset \mathbb P^g$ of genus $g\le 14$, we study projections $S\hookrightarrow \mathbb P^g\dashrightarrow \mathbb P^2$ of minimal degree and their variational structure. In particular, we prove that…

Algebraic Geometry · Mathematics 2025-04-16 Federico Moretti , Andrés Rojas