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Given a complete non-compact Riemannian manifold $(M,g)$ with certain curvature restrictions, we introduce an expansion condition concerning a group of isometries $G$ of $(M,g)$ that characterizes the coerciveness of $G$ in the sense of…

Analysis of PDEs · Mathematics 2020-10-14 Csaba Farkas , Alexandru Kristály , Ágnes Mester

Let $f$ be a holomorphic mapping between compact complex manifolds. We give a criterion for $f$ to have {\it unobstructed deformations}, i.e. for the local moduli space of $f$ to be smooth: this says, roughly speaking, that the group of…

Complex Variables · Mathematics 2016-09-06 Ziv Ran

In this paper we produce many examples of thin subgroups of special linear groups that are isomorphic to the fundamental groups of non-arithmetic hyperbolic manifolds. Specifically, we show that the non-arithmetic lattices in…

Geometric Topology · Mathematics 2021-01-20 Samuel A. Ballas

We consider hyperbolic and partially hyperbolic diffeomorphisms on compact manifolds. Associated with invariant foliation of these systems, we define some topological invariants and show certain relationships between these topological…

Dynamical Systems · Mathematics 2007-05-23 Radu Saghin , Zhihong Xia

We formalize the concepts of holomorphic affine and projective structures along the leaves of holomorphic foliations by curves on complex manifolds. We show that many foliations admit such structures, we provide local normal forms for them…

Differential Geometry · Mathematics 2024-07-08 Bertrand Deroin , Adolfo Guillot

A Stein covering of a complex manifold may be used to realise its analytic cohomology in accordance with the Cech theory. If, however, the Stein covering is parameterised by a smooth manifold rather than just a discrete set, then we…

Complex Variables · Mathematics 2007-05-23 Toby Bailey , Michael Eastwood , Simon Gindikin

For several instances of metric largeness like enlargeability or having hyperspherical universal covers, we construct non-large vector subspaces in the rational homology of finitely generated groups. The functorial properties of this…

Geometric Topology · Mathematics 2014-02-26 Michael Brunnbauer , Bernhard Hanke

We review some basic theorems on integrability of Hamiltonian systems, namely the Liouville-Arnold theorem on complete integrability, the Nekhoroshev theorem on partial integrability and the Mishchenko-Fomenko theorem on noncommutative…

Mathematical Physics · Physics 2015-05-13 Emanuele Fiorani

We generalize the notion of tight geodesics in the curve complex to tight trees. We then use tight trees to construct model geometries for certain surface bundles over graphs. This extends some aspects of the combinatorial model for doubly…

Geometric Topology · Mathematics 2020-07-08 Mahan Mj

This is the first in a series of papers about foliations in derived geometry. After introducing derived foliations on arbitrary derived stacks, we concentrate on quasi-smooth and rigid derived foliations on smooth complex algebraic…

Algebraic Geometry · Mathematics 2020-05-22 Bertrand Toën , Gabriele Vezzosi

A conjecture due to Gompf asserts that no nontrivial Brieskorn homology sphere admits a pseudoconvex embedding in ${\mathbb C}^2$, with either orientation. A related question asks whether every compact contractible 4-manifold admits the…

Geometric Topology · Mathematics 2017-12-12 Thomas E. Mark , Bülent Tosun

We consider singular foliations of codimension one on 3-manifolds, in the sense defined by A. Haefliger as being Gamma_1-structures. We prove that under the obvious linear embedding condition, they are Gamma_1-homotopic to a regular…

Geometric Topology · Mathematics 2012-10-18 Francois Laudenbach , Gael Gael Meigniez

We prove the nonexistence of a proper singular Riemannian foliation admitting section in compact manifolds of nonpositive curvature. Then we give a global description of proper singular Riemannian foliations admitting sections on Hadamard…

Differential Geometry · Mathematics 2007-05-23 Dirk Toeben

We give an infinite family of embeddings of $\mathbb{R} P^2$ to $S^4$ such that they are mutually topologically isotopic however are not smoothly isotopic to each other. Moreover, they are topologically isotopic to the standard $P^2$-knot.…

Geometric Topology · Mathematics 2023-12-05 Jin Miyazawa

We introduce a new generalization of Gompf nuclei and give applications. We construct infinitely many exotic smooth structures for a large class of compact 4-manifolds with boundary, regarding topological invariants. We prove that a large…

Geometric Topology · Mathematics 2012-02-17 Kouichi Yasui

A well-known class of questions asks the following: If $X$ and $Y$ are metric measure spaces and $f:X\rightarrow Y$ is a Lipschitz mapping whose image has positive measure, then must $f$ have large pieces on which it is bi-Lipschitz?…

Metric Geometry · Mathematics 2013-12-16 Guy C. David

Let $\Sigma$ be a Riemannian manifold with strictly convex spherical boundary. Assuming absence of conjugate points and that the trapped set is hyperbolic, we show that $\Sigma$ can be isometrically embedded into a closed Riemannian…

Differential Geometry · Mathematics 2023-04-03 Dong Chen , Alena Erchenko , Andrey Gogolev

We study smooth proper embeddings of compact orientable surfaces in compact orientable $4$-manifolds and elements in the mapping class group of that surface which are induced by diffeomorphisms of the ambient $4$-manifolds. We call such…

Geometric Topology · Mathematics 2025-02-28 Shital Lawande , Kuldeep Saha

We give a simple procedure to construct explicit examples of nilmanifolds admitting an Anosov diffeomorphism, and show that a reasonable classification up to homeomorphism (or even up to commensurability) of such nilmanifolds would not be…

Dynamical Systems · Mathematics 2007-05-23 Jorge Lauret

Given a closed $n$-manifold, we consider the set of simple homotopy types of $n$-manifolds within its homotopy type, called its simple homotopy manifold set. We characterise it in terms of algebraic K-theory, the surgery obstruction map,…

Algebraic Topology · Mathematics 2026-04-13 Csaba Nagy , John Nicholson , Mark Powell