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We construct a spectral sequence associated to a stratified space, which computes the compactly supported cohomology groups of an open stratum in terms of the compactly supported cohomology groups of closed strata and the reduced cohomology…

Algebraic Topology · Mathematics 2017-06-14 Dan Petersen

Let T be a compact torus and X a nice compact T-space (say a manifold or variety). We introduce a functor assigning to X a "GKM-sheaf" F_X over a "GKM-hypergraph" G_X. Under the condition that X is equivariantly formal, the ring of global…

Algebraic Topology · Mathematics 2013-04-26 Thomas Baird

We study the cup product on the Hochschild cohomology of the stack quotient [X/G] of a smooth quasi-projective variety X by a finite group G. More specifically, we construct a G-equivariant sheaf of graded algebras on X whose G-invariant…

Algebraic Geometry · Mathematics 2018-12-13 Cris Negron , Travis Schedler , Pieter Belmans , Pavel Etingof

We provide a smoothening criterion for group actions on manifolds by singular diffeomorphisms. We prove that if a countable group $\Gamma$ has the fixed point property FW for walls (e.g. if it has property (T)), every aperiodic action of…

Dynamical Systems · Mathematics 2020-05-13 Yash Lodha , Nicolás Matte Bon , Michele Triestino

Let $\gamma_0$ be a curve on a surface $\Sigma$ of genus $g$ and with $r$ boundary components and let $\pi_1(\Sigma)\curvearrowright X$ be a discrete and cocompact action on some metric space. We study the asymptotic behavior of the number…

Geometric Topology · Mathematics 2016-12-23 Viveka Erlandsson , Hugo Parlier , Juan Souto

Conformable derivatives involve a fractional parameter while preserving locality: on smooth functions they reduce to a classical derivative multiplied by an explicit weight. Exploiting this structural feature, we show that conformable time…

Dynamical Systems · Mathematics 2026-02-09 Mohamed Khoulane , Aziz El Ghazouani , M'hamed Elomari

We compute the cohomological Hall algebra of zero-dimensional sheaves on an arbitrary smooth quasi-projective surface $S$ with pure cohomology, deriving an explicit presentation by generators and relations. When $S$ has trivial canonical…

Algebraic Geometry · Mathematics 2026-05-26 Anton Mellit , Alexandre Minets , Olivier Schiffmann , Eric Vasserot

We consider semi-free Hamiltonian $S^1$-manifolds of dimension six and establish when the equivariant cohomology and data on the fixed point set determine the isomorphism type. Gonzales listed conditions under which the isomorphism type of…

Symplectic Geometry · Mathematics 2025-09-08 Liat Kessler , Nikolas Wardenski

We prove an analogon of the the fundamental homomorphism theorem for certain classes of exact and essentially surjective functors of Abelian categories $\mathscr{Q}:\mathcal{A} \to \mathcal{B}$. It states that $\mathscr{Q}$ is up to…

Category Theory · Mathematics 2016-12-06 Mohamed Barakat , Markus Lange-Hegermann

We introduce partial group algebras with relations in a purely algebraic framework. Given a group and a set of relations, we define an algebraic partial action and prove that the resulting partial skew group ring is isomorphic to the…

Rings and Algebras · Mathematics 2025-12-16 Giuliano Boava , Gilles G. de Castro , Daniel Gonçalves , Daniel W. van Wyk

Several notions of sheaf on various types of quantale have been proposed and studied in the last twenty five years. It is fairly standard that for an involutive quantale Q satisfying mild algebraic properties the sheaves on Q can be defined…

Rings and Algebras · Mathematics 2011-08-02 Pedro Resende

In this paper we study the problem of determining the homology groups of a quotient of a topological space by an action of a group. The method is to represent the original topological space as a homotopy limit of a diagram, and then act…

Combinatorics · Mathematics 2016-09-07 Eric Babson , Dmitry Kozlov

The Computation of discrete Contractive semigroups becomes necessary when we deal with several types of evolution equations in Discretizable Hilbert spaces, in this work we study some properties of the discrete forms of the contractive…

Numerical Analysis · Mathematics 2010-12-24 Fredy Vides

We define the homology of a simplicial set with coefficients in a Segal's $\Gamma$-set ($\mathbf S$-module). We show the relevance of this new homology with values in $\mathbf S$-modules by proving that taking as coefficients the $\mathbf…

Algebraic Geometry · Mathematics 2019-05-10 Alain Connes , Caterina Consani

We study topological properties of semi-group actions on the circle by orientation-preserving homeomorhisms. We prove that a generic action either possesses a forward-invariant interval-domain (i.e. a finite union of disjoint circle arcs),…

Dynamical Systems · Mathematics 2018-04-04 Victor Kleptsyn , Yury Kudryashov , Alexey Okunev

We consider semigroups of Ruelle-expanding maps, parameterized by random walks on the free semigroup, with the aim of examining their complexity and exploring the relation between intrinsic properties of the semigroup action and the…

Dynamical Systems · Mathematics 2017-02-01 Maria Carvalho , Fagner B. Rodrigues , Paulo Varandas

Let $X$ be a smooth projective variety acted on by a reductive group $G$. Let $L$ be a positive $G$-equivariant line bundle over $X$. We use the Witten deformation of the Dolbeault complex of $L$ to show, that the cohomology of the sheaf of…

Symplectic Geometry · Mathematics 2007-05-23 Maxim Braverman

We develop a battery of tools for studying quasi-isometric rigidity and classification problems for splittings of groups. The techniques work best for finite graphs of groups where all edge and vertex groups are coarse PD groups. For…

Group Theory · Mathematics 2007-05-23 Lee Mosher , Michah Sageev , Kevin Whyte

Let $\pi$ be a group equipped with an action of a second group $G$ by automorphisms. We define the equivariant cohomological dimension ${\sf cd}_G(\pi)$, the equivariant geometric dimension ${\sf gd}_G(\pi)$, and the equivariant…

Algebraic Topology · Mathematics 2020-04-24 Mark Grant , Ehud Meir , Irakli Patchkoria

The dynamical degrees of a rational map $f:X\dashrightarrow X$ are fundamental invariants describing the rate of growth of the action of iterates of $f$ on the cohomology of $X$. When $f$ has nonempty indeterminacy set, these quantities can…

Dynamical Systems · Mathematics 2015-03-13 Sarah Koch , Roland K. W. Roeder