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We study low-dimensional problems in topology and geometry via a study of contact and Cauchy-Riemann ($CR$) structures. A contact structure is called spherical if it admits a compatible spherical $CR$ structure. We will talk about spherical…

Symplectic Geometry · Mathematics 2007-05-23 Jih-Hsin Cheng

We consider possibly singular rational projective k*-surfaces and provide an explicit description of the unit component of the automorphism group in terms of isotropy group orders and intersection numbers of suitable invariant curves. As an…

Algebraic Geometry · Mathematics 2020-12-02 Juergen Hausen , Timo Hummel

We produce a large class of hyperbolic homology 3-spheres admitting arbitrarily many distinct tight contact structures. We also produce a sub-class admitting arbitrarily many distinct tight contact structures within the same homotopy class…

Geometric Topology · Mathematics 2024-05-29 Mahan Mj , Balarka Sen

We determine the structure of automorphism group or each nonsplit metacyclic 2-group. This completes the work on automorphism groups of metacyclic $p$-groups.

Group Theory · Mathematics 2017-06-27 Haimiao Chen

We classify compact 2-connected homogeneous spaces with the same rational cohomology as a product of spheres. This classification relies on spectral sequences, homotopy theory, and representation theory. We then apply this classification to…

Geometric Topology · Mathematics 2007-05-23 Linus Kramer

It is known that the automorphism group of any projective K3 surface is finitely generated [24]. In this paper, we consider a certain kind of K3 surfaces with Picard number 3 whose automorphism groups are isomorphic to congruence subgroups…

Algebraic Geometry · Mathematics 2023-08-15 Kenji Hashimoto , Kwangwoo Lee

The principal filtration of the infinite-dimensional odd Contact Lie superalgebra over a field of characteristic $p>2$ is proved to be invariant under the automorphism group by investigating ad-nilpotent elements and determining certain…

Rings and Algebras · Mathematics 2018-07-27 Jixia Yuan , Wende Liu

We determine which simple algebraic groups of type $^3D_4$ over arbitrary fields of characteristic different from 2 admit outer automorphisms of order 3, and classify these automorphisms up to conjugation. The criterion is formulated in…

Group Theory · Mathematics 2014-09-08 Max-Albert Knus , Jean-Pierre Tignol

We are interested in overgroups of the automorphism group of the Rado graph. One class of such overgroups is completely understood; this is the class of reducts. In this article we tie recent work on various other natural overgroups, in…

Combinatorics · Mathematics 2012-05-17 Peter Cameron , Claude Laflamme , Maurice Pouzet , Sam Tarzi , Robert Woodrow

Let $f:G\rightarrow H$ be a homomorphism of groups, we construct a topological space $X_f$ such that its group of homeomorphisms is isomorphic to $G$, its group of homotopy classes of self-homotopy equivalences is isomorphic to $H$ and the…

Algebraic Topology · Mathematics 2021-04-16 Pedro J. Chocano , Manuel A. Morón , Francisco R. Ruiz del Portal

We construct (infinitely many) examples in all dimensions of contactomorphisms of closed overtwisted contact manifolds that are smoothly isotopic but not contact-isotopic to the identity.

Symplectic Geometry · Mathematics 2019-05-29 Fabio Gironella

We show that a complex normal surface singularity admitting a contracting automorphism is necessarily quasihomogeneous. We also describe the geometry of a compact complex surface arising as the orbit space of such a contracting…

Dynamical Systems · Mathematics 2013-03-07 Charles Favre , Matteo Ruggiero

In this paper, homology of a contact CR-submanifold of a real hypersurface, which has naturally almost contact metric structure induced from the complex Euclidean space $\mathbb{C}^{m}$, is examined. More precisely, nonexistence of stable…

Differential Geometry · Mathematics 2021-07-28 Fulya Sahin , Bayram Sahin

In this note we observe, answering a question of Eliashberg and Thurston, that all contact structures on a closed oriented 3-manifold are $C^\infty$-deformations of foliations.

Symplectic Geometry · Mathematics 2007-05-23 John B. Etnyre

Closed (and simply-connected) manifolds whose dimensions are greater than 4 are classified via sophisticated algebraic and abstract theory such as surgery theory and homotopy theory. It is difficult to handle 3 or 4-dimensional closed…

Algebraic Topology · Mathematics 2021-09-24 Naoki Kitazawa

To any metric spaces there is an associated metric profile. The rectifiability of the metric profile gives a good notion of curvature of a sub-Riemannian space. We shall say that a curvature class is the rectifiability class of the metric…

Metric Geometry · Mathematics 2007-05-23 Marius Buliga

We give examples of contactomorphisms in every dimension that are smoothly isotopic to the identity but that are not contact isotopic to the identity. In fact, we prove the stronger statement that they are not even symplectically…

Symplectic Geometry · Mathematics 2019-09-16 Patrick Massot , Klaus Niederkrüger

We classify contact toric 3-manifolds up to contactomorphism, through explicit descriptions, building off of work by Lerman [Lerman03]. As an application, we classify all contact structures on 3-manifolds that can be realised as a concave…

Symplectic Geometry · Mathematics 2025-01-17 Aleksandra Marinković , Laura Starkston

A normal subgroup of the (extended) mapping class group of a surface is said to be geometric if its automorphism group is the mapping class group. We prove that in the case of the Cantor tree surface, every normal subgroup is geometric. We…

Group Theory · Mathematics 2020-02-18 Alan McLeay

On every compact and orientable three-manifold, we construct total foliations (three codimension 1 foliations that are transverse at every point). This construction can be performed on any homotopy class of plane fields with vanishing Euler…

Geometric Topology · Mathematics 2009-10-19 Masayuki Asaoka , Emmanuel Dufraine , Takeo Noda