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This work seeks to advance the understanding of the smooth structure of the moduli space of self-dual contact instantons (SDCI) on Sasakian 7-manifolds M. A neighborhood of a smooth point of M is locally modeled on the first cohomological…

Differential Geometry · Mathematics 2024-04-23 Luis E. Portilla P. , Eric Loubeau , Henrique N. Sá Earp

We study fundamental groups of toroidal compactifications of non compact ball quotients and show that the Shafarevich conjecture on holomorphic convexity for these complex projective manifolds is satisfied in dimension 2 provided the…

Algebraic Geometry · Mathematics 2018-05-03 Philippe Eyssidieux

We systematically study calibrated geometry in hyperk\"ahler cones $C^{4n+4}$, their 3-Sasakian links $M^{4n+3}$, and the corresponding twistor spaces $Z^{4n+2}$, emphasizing the relationships between submanifold geometries in various…

Differential Geometry · Mathematics 2025-06-23 Benjamin Aslan , Spiro Karigiannis , Jesse Madnick

The first goal of the article is to solve several fundamental problems in the theory of holomorphic bundles over non-algebraic manifolds: For instance we prove that stability and semi-stability are Zariski open properties in families when…

Differential Geometry · Mathematics 2007-05-23 Andrei Teleman

In this paper, we provide new examples of 1-obstructed and atomic sheaves on an infinite series of locally complete families of projective hyper-K\"ahler manifolds. More precisely, (1) we prove that the fixed loci of the natural…

Algebraic Geometry · Mathematics 2025-07-21 Hanfei Guo , Zhiyu Liu

A hyperk\"ahler manifold $M$ has a family of induced complex structures indexed by a two-dimensional sphere $S^2 \cong \mathbb{CP}^1$. The twistor space of $M$ is a complex manifold $Tw(M)$ together with a natural holomorphic projection…

Differential Geometry · Mathematics 2021-04-29 T. Barron , A. Tomberg

We study metric aspects of the universal moduli space of solutions to Hitchin's equations as the complex structure $J$ varies over the Teichm\"uller space $\mathcal{T}$ of a closed surface $\Sigma$. Our approach is gauge theoretical and…

Differential Geometry · Mathematics 2026-01-09 Luis Álvarez-Cónsul , Mario Garcia-Fernandez , Oscar García-Prada , Samuel Trautwein

Let G be a Lie goup, let M and N be smooth connected G-manifolds, let f be a smooth G-map from M to N, and let P denote the fiber of f. Given a closed and equivariantly closed relative 2-form for f with integral periods, we construct the…

Algebraic Topology · Mathematics 2009-07-31 Johannes Huebschmann

We show that a 1-parameter family Ricci flow ancient solutions arises from the natural collapsings of the twistor space of positive quaternion K\"ahler manifolds. We use these ancient solutions to show that a positive quaternion K\"ahler…

Differential Geometry · Mathematics 2008-10-14 Ryoichi Kobayashi

In this paper, we consider $n$-dimensional compact K$\ddot{a}$hler manifold with semi-ample canonical line bundle under the long time solution of K$\ddot{a}$hler Ricci Flow. In particular, if the Kodaira dimension is one, Ricci curvature…

Differential Geometry · Mathematics 2026-02-23 Cheuk Yan Fung

We study the geometry of exceptional loci of birational contractions of hyper-K\"ahler fourfolds that are of K3$^{[2]}$-type. These loci are conic bundles over K3 surfaces and we determine their classes in the Brauer group. For this we use…

Algebraic Geometry · Mathematics 2022-12-12 Bert van Geemen , Grzegorz Kapustka

The twistor space of representations on an open variety maps to a weight two space of local monodromy transformations around a divisor component at infinty. The space of $\sigma$-invariant sections of this slope-two bundle over the twistor…

Algebraic Geometry · Mathematics 2007-10-16 Carlos T. Simpson

Let $X=\overline{X}-D$ be a smooth quasi-projective curve. In arXiv:2110.12300 we constructed a Deligne-Hitchin modui space with Hecke gauge groupoid for connections of rank $2$. We extend this construction to the case of any rank $r$,…

Algebraic Geometry · Mathematics 2023-03-27 Carlos Simpson

We show that the Reshetikhin-Turaev-Walker invariant of 3-manifolds can be normalized to obtain an invariant of 4-dimensional thickenings of 2-complexes. Moreover when the underlying semisimple tortile category comes from the…

Geometric Topology · Mathematics 2007-05-23 Ivelina Bobtcheva , Frank Quinn

It is well-known that odd-dimensional manifolds have Euler characteristic zero. Furthemore orientable manifolds have an even Euler characteristic unless the dimension is a multiple of $4$. We prove here a generalisation of these statements:…

Algebraic Topology · Mathematics 2018-10-30 Renee S. Hoekzema

We remark the density of the jumping loci of the Picard number of a hyperk\"ahler manifold under small one-dimensional deformation and provide some applications for the Mordell-Weil groups of Jacobian K3 surfaces.

Algebraic Geometry · Mathematics 2007-05-23 Keiji Oguiso

This expository paper details the theory of rank one Higgs bundles over a closed Riemann surface X and their relationship to representations of the fundamental group of X. We construct an equivalence between the deformation theories of flat…

Differential Geometry · Mathematics 2011-07-12 William M. Goldman , Eugene Z. Xia

We study a system of equations on a compact complex manifold, that couples the scalar curvature of a Kaehler metric with a spectral function of a first-order deformation of the complex structure. The system comes from an…

Differential Geometry · Mathematics 2022-07-08 Carlo Scarpa

The aim of this paper is to continue the study of Kodaira dimension for almost complex manifolds, focusing on the case of compact $4$-dimensional solvmanifolds without any integrable almost complex structure. According to the classification…

Differential Geometry · Mathematics 2021-06-07 Andrea Cattaneo , Antonella Nannicini , Adriano Tomassini

We investigate the structure of smooth holomorphic foliations with numerically flat tangent bundles on compact K\"ahler manifolds. Extending earlier results on non-uniruled projective manifolds by the second and fourth authors, we show that…

Algebraic Geometry · Mathematics 2024-11-14 Stéphane Druel , Jorge Vitório Pereira , Brent Pym , Frédéric Touzet