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We study constructions of contact forms on closed manifolds. A notion of strong symplectic fold structure is defined and we prove that there is a contact form on $M \x X$ provided that $M$ admits such a structure and $X$ is contact. This…

Symplectic Geometry · Mathematics 2013-08-13 Bogusław Hajduk , Rafał Walczak

A Jacobi structure $J$ on a line bundle $L\to M$ is weakly regular if the sharp map $J^\sharp : J^1 L \to DL$ has constant rank. A generalized contact bundle with regular Jacobi structure possess a transverse complex structure. Paralleling…

Differential Geometry · Mathematics 2019-07-15 Jonas Schnitzer

A theorem of Mumford states that, on complex surfaces, any normal isolated singularity whose link is diffeomorphic to a sphere is actually a smooth point. While this property fails in higher dimensions, McLean asks whether the contact…

Algebraic Geometry · Mathematics 2017-01-24 Tommaso de Fernex , Yu-Chao Tu

We construct a simple topological invariant of certain 3-manifolds, including quotients of the 3-sphere by finite groups, based on the fact that the tangent bundle of an orientable 3-manifold is trivialisable. This invariant is strong…

Geometric Topology · Mathematics 2007-05-23 Siddhartha Gadgil

Given a contact structure on a manifold $V$ together with a supporting open book decomposition, Bourgeois gave an explicit construction of a contact structure on $V \times \mathbb{T}^2$. We prove that all such structures are universally…

Symplectic Geometry · Mathematics 2022-06-15 Jonathan Bowden , Fabio Gironella , Agustin Moreno

We show that the CR structure on the twistor space of a quaternionic contact structure described by Biquard is normal if and only if the Ricci curvature of the Biquard connection commutes with the endomorphisms in the quaternionic structure…

Differential Geometry · Mathematics 2011-07-07 Johann Davidov , Stefan Ivanov , Ivan Minchev

We study complex projective manifolds X that admit surjective endomorphisms f:X->X of degree at least two. In case f is etale, we prove structure theorems that describe X. In particular, a rather detailed description is given if X is a…

Algebraic Geometry · Mathematics 2007-06-22 Marian Aprodu , Stefan Kebekus , Thomas Peternell

Let $X$ be a cubic fourfold that has only simple singularities and does not contain a plane. We prove that the Fano variety of lines on $X$ has the same analytic type of singularity as the Hilbert scheme of two points on a surface with only…

Algebraic Geometry · Mathematics 2018-04-03 Ryo Yamagishi

Let $(X,0)$ be an isolated complete intersection complex singularity ($X$ can also be smooth at 0). Let $K$ be its link, $\cal X$ its canonical contact structure and $\D_X$ the complex vector bundle associated to $\cal X$. We prove that the…

Algebraic Geometry · Mathematics 2007-05-23 Jose Seade

Let Z be a compact complex (2n+1)-manifold which carries a {\em complex contact structure}, meaning a codimension-1 holomorphic sub-bundle D of TZ which is maximally non-integrable. If Z admits a K\"ahler-Einstein metric of positive scalar…

dg-ga · Mathematics 2008-02-03 Claude LeBrun

We describe a necessary and sufficient condition for a principal circle bundle over an even-dimensional manifold to carry an invariant contact structure. As a corollary it is shown that all circle bundles over a given base manifold carry an…

Symplectic Geometry · Mathematics 2014-02-26 Fan Ding , Hansjörg Geiges

We show that an oriented elliptic 3-manifold admits a universally tight positive contact structure iff the corresponding group of deck transformations on $S^3$ preserves a standard contact structure pointwise. We also relate univerally…

Geometric Topology · Mathematics 2007-05-23 Siddhartha Gadgil

A real 3-manifold is a smooth 3-manifold together with an orientation preserving smooth involution, which is called a real structure. A real contact 3-manifold is a real 3-manifold with a contact distribution that is antisymmetric with…

Geometric Topology · Mathematics 2023-05-08 Merve Cengiz , Ferit Öztürk

This paper explores the Fano variety of lines in hypersurfaces, particularly focusing on those with mild singularities. Our first result explores the irreducibility of the variety $\Sigma$ of lines passing through a singular point $y$ on a…

Algebraic Geometry · Mathematics 2025-03-12 Jiayi Hu , Fengyang Wang , Xinlang Zhu

By use of a variety of techniques (most based on constructions of quasipositive knots and links, some old and others new), many smooth 3-manifolds are realized as transverse intersections of complex surfaces in complex 3-space with strictly…

Geometric Topology · Mathematics 2015-08-21 Lee Rudolph

The notion of non-projectible contact forms on a given compact manifold $M$ is introduced by the first-named author in [Ohb], the set of which he also shows is a residual subset of the set of (coorientable) contact forms, both in the case…

Symplectic Geometry · Mathematics 2025-05-13 Yong-Geun Oh , Yasha Savelyev

We classify codimension two analytic submanifolds X of projective space having the property that any line through a general point p having contact to order two with X at p automatically has contact to order three. We give applications to…

Algebraic Geometry · Mathematics 2007-05-23 J. M. Landsberg , Colleen Robles

We consider certain fiber bundles over a paraquaternionic contact manifolds, called twistor and reflector spaces, and show that these carry an intrinsic geometric structure that is always integrable.

Differential Geometry · Mathematics 2024-09-04 Stefan Ivanov , Ivan Minchev , Marina Tchomakova

Contact path geometries are curved geometric structures on a contact manifold comprising smooth families of paths modeled on the family of all isotropic lines in the projectivization of a symplectic vector space. Locally such a structure is…

Differential Geometry · Mathematics 2007-05-23 Daniel J. F. Fox

In the spirit of Sullivan's paper "Cycles for the Dynamical Study of Foliated Manifolds and Complex Manifolds", existence of a contact structure on a closed manifold $M$ is shown to be equivalent to existence of an ample $S^1$-invariant…

Differential Geometry · Mathematics 2015-12-14 Mélanie Bertelson , Cédric De Groote