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For each prime $p$, this paper constructs compact complex hyperbolic $2$-manifolds with an isometric action of $\mathbb{Z} / p \mathbb{Z}$ that is not free and has only isolated fixed points. The case $p = 2$ is special, and finding general…

Geometric Topology · Mathematics 2025-08-29 Alan W. Reid , Matthew Stover

We prove that every homotopy class of almost contact structures on a closed 5-dimensional manifold admits a contact structure.

Symplectic Geometry · Mathematics 2014-11-10 Roger Casals , Dishant M. Pancholi , Francisco Presas

Homotopy is an important feature of associative and Jordan algebraic structures: such structures always come in families whose members need not be isomorphic among other, but still share many important properties. One may regard homotopy as…

Rings and Algebras · Mathematics 2007-05-23 Wolfgang Bertram

In the paper "The Second cohomology of nilpotent orbits in classical Lie algebras, Kyoto J. Math. 60 (2020), no. 2, 717-799" by I. Biswas, P. Chatterjee and C. Maity homotopy types of nilpotent orbits are explicitly described in the case of…

Group Theory · Mathematics 2022-03-22 Indranil Biswas , Pralay Chatterjee , Chandan Maity

We study the homotopy types of complements of arrangements of n transverse planes in R^4, obtaining a complete classification for n <= 6, and lower bounds for the number of homotopy types in general. Furthermore, we show that the homotopy…

Geometric Topology · Mathematics 2007-05-23 Daniel Matei , Alexander I. Suciu

For a finite simplicial complex K and a CW-pair (X,A), there is an associated CW-complex Z_K(X,A), known as a polyhedral product. We apply discrete Morse theory to a particular CW-structure on the n-sphere moment-angle complexes Z_K(D^{n},…

Combinatorics · Mathematics 2012-12-21 Vladimir Grujic , Volkmar Welker

Let $D_{n,\gamma}$ be the complex of graphs on $n$ vertices and domination number at least $\gamma$. We prove that $D_{n,n-2}$ has the homotopy type of a finite wedge of 2-spheres. This is done by using discrete Morse theory techniques.…

Algebraic Topology · Mathematics 2021-02-16 Jesús González , Teresa I. Hoekstra-Mendoza

We study a class of smooth torus manifolds whose orbit space has the combinatorial structure of a simple polytope with holes. We construct moment angle manifolds for such polytopes with holes and use them to prove that the associated torus…

Symplectic Geometry · Mathematics 2024-12-05 Mainak Poddar , Soumen Sarkar

We study isoparametric submanifolds of rank at least two in a separable Hilbert space, which are known to be homogeneous by a result of Heintze and Liu, and associate to such a submanifold M and a point x in M a canonical homogeneous…

Differential Geometry · Mathematics 2012-05-15 Claudio Gorodski , Ernst Heintze

We prove that independence complex of a bipartite circle graph is homotopy equivalent to a wedge of spheres, resolving a conjecture posed by Przytycki and Silvero. As a corollary, we obtain that extreme Khovanov spectrum,…

Geometric Topology · Mathematics 2023-03-22 Apratim Chakraborty

It is shown that the first and second homotopy groups of the $\eta$-inverted sphere spectrum over a field of characteristic not two are zero. A cell presentation of higher Witt theory is given as well, at least over the complex numbers.

Algebraic Topology · Mathematics 2018-01-10 Oliver Röndigs

We determine the number of distinct fibre homotopy types for the gauge groups of principal $Sp(2)$-bundles over a closed, simply-connected four-manifold.

Algebraic Topology · Mathematics 2018-07-09 Tseleung So , Stephen Theriault

In this article, we treat G_2-geometry as a special case of multisymplectic geometry and make a number of remarks regarding Hamiltonian multivector fields and Hamiltonian differential forms on manifolds with an integrable G_2-structure; in…

Differential Geometry · Mathematics 2015-06-17 Hyunjoo Cho , Sema Salur , Albert J. Todd

We discuss the alternative algebraic structures on the manifold of quantum states arising from alternative Hermitian structures associated with quantum bi-Hamiltonian systems. We also consider the consequences at the level of the Heisenberg…

Quantum Physics · Physics 2007-05-23 G. Marmo , G. Scolarici , A. Simoni , F. Ventriglia

We present a sheaf-theoretic construction of shape space -- the space of all shapes. We do this by describing a homotopy sheaf on the poset category of constructible sets, where each set is mapped to its Persistent Homology Transform (PHT).…

Algebraic Topology · Mathematics 2023-06-26 Shreya Arya , Justin Curry , Sayan Mukherjee

The mapping class group of a non-exceptional oriented surface of finite type admits a biautomatic structure.

Group Theory · Mathematics 2009-12-02 Ursula Hamenstaedt

We give a characterization of the $2$-step nilpotent Lie algebras whose corresponding Lie groups admit a left invariant complex structure. This is done by considering separately the cases when the complex structure is 2-step or 3-step…

Differential Geometry · Mathematics 2025-08-11 Maria Laura Barberis

In this paper, we present a simple proof of the fact that any compact subgroup of homeomorphisms of the 2-sphere is topologically conjugate to a closed subgroup of the orthogonal group O(3).

Geometric Topology · Mathematics 2019-01-03 Boris Kolev

We present a structural description of finite nilpotent groups of class at most $2$ using a specified number of subdirect and central products of $2$-generated such groups. As a corollary, we show that all of these groups are isomorphic to…

Group Theory · Mathematics 2025-04-08 Dávid R. Szabó

We discuss the complex geometry of two complex five-dimensional K\"ahler manifolds which are homogeneous under the exceptional Lie group $G_2$. For one of these manifolds rigidity of the complex structure among all K\"ahlerian complex…

Differential Geometry · Mathematics 2020-11-12 D. Kotschick , D. K. Thung