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We study the cohomology with modular coefficients of Deligne-Lusztig varieties associated to Coxeter elements. Under some torsion-free assumption on the cohomology we derive several results on the principal l-block of a finite reductive…

Representation Theory · Mathematics 2012-04-11 Olivier Dudas

We give a cohomological criterion for certain decomposition of Borel graphs, which is an analog of Dunwoody's work on accessibility of groups. As an application, we prove that a Borel graph $(X,G)$ with uniformly bounded degrees of…

Group Theory · Mathematics 2026-03-12 Hiroki Ishikura

We complete the study of the topological period-index problem over 8 dimensional finite CW complexes started in a preceding paper. More precisely, we determine the sharp upper bound of the index of a topological Brauer class $\alpha\in…

Algebraic Topology · Mathematics 2020-12-22 Xing Gu

Following an idea of Totaro, we prove that the classical integral cycle class map from algebraic cycles to \'etale cohomology factors through a quotient of $\ell$-adic \'etale cobordism over an algebraically closed field of positive…

Algebraic Geometry · Mathematics 2010-01-06 Gereon Quick

The numerical invariants (global) cohomological length, (global) cohomological width, and (global) cohomological range of complexes (algebras) are introduced. Cohomological range leads to the concepts of derived bounded algebras and…

Representation Theory · Mathematics 2017-05-17 Chao Zhang , Yang Han

We introduce characteristic classes for the spectral sequence associated to a split short exact sequence of Hopf algebras. We show that these characteristic classes can be seen as obstructions for the vanishing of differentials in the…

Algebraic Topology · Mathematics 2011-03-10 Dieter Degrijse , Nansen Petrosyan

We outline Hutchings's prescription that produces an ECH analog of Latschev and Wendl's algebraic $k$-torsion in the context of $ech$, a variant of ECH used in a proof of the isomorphism between Heegaard Floer and Seiberg-Witten Floer…

Symplectic Geometry · Mathematics 2016-03-11 Cagatay Kutluhan , Gordana Matic , Jeremy Van Horn-Morris , Andy Wand

We prove a certain 'fat hyperplane section' Weak Lefschetz-type theorem for etale cohomology of non-projective varieties, similar to a result of Goresky and MacPherson (over complex numbers). This statement easily yields certain (vast)…

Algebraic Geometry · Mathematics 2015-02-03 Mikhail V. Bondarko

We prove the existence of a sequence of commutative diagrams generalizing existing results on the cohomology of the Borel-Serre boundary and well-rounded retract to the context of the well-tempered complex. Our main theorem provides a…

Number Theory · Mathematics 2025-10-21 Dylan Galt , Mark McConnell

Given a non-cyclic simple dimension group D and a subgroup E of Q/Z, we produce a minimal \'etale equivalence relation R such that H_0(\R) is isomorphic to D \oplus E, where H_0(R) denotes the zeroth homology group of R. The equivalence…

Dynamical Systems · Mathematics 2025-04-28 Michael Francesco Ala , Hung-Chang Liao , Aaron Tikuisis

This article is the final one of a series of articles on certain blocks of modular representations of finite groups of Lie type and the associated geometry. We prove the conjecture of Brou\'e on derived equivalences induced by the complex…

Representation Theory · Mathematics 2012-04-10 Olivier Dudas , Raphaël Rouquier

The Bethe approximation is a well-known approximation of the partition function used in statistical physics. Recently, an equality relating the partition function and its Bethe approximation was obtained for graphical models with binary…

Information Theory · Computer Science 2014-12-22 Ryuhei Mori

Plateau's problem is to find a surface with minimal area spanning a given boundary. In 1960, Reifenberg and Adams developed a definition for "span" using \v{C}ech homology, and variants of this definition have been used ever sense. However,…

Differential Geometry · Mathematics 2014-12-09 Jenny Harrison , Harrison Pugh

Main theorem of this paper states that Floer cohomology groups in a Hilbert space are isomorphic to the cohomological Conley Index. It is also shown that calculating cohomological Conley Index does not require finite dimensional…

Differential Geometry · Mathematics 2014-08-05 Maciej Starostka

Using the technique of inductive resolution introduced in arXiv:2303.07979, we prove that the homology of Rook-Brauer Algebra, interpreted as appropriate Tor-group, is isomorphic to that of symmetric group for all degrees under the…

Rings and Algebras · Mathematics 2025-05-29 Khoa Ta

We have previously shown that the isomorphism classes of orientable locally trivial fields of $C^*$-algebras over a compact metrizable space $X$ with fiber $D\otimes \mathbb{K}$, where $D$ is a strongly self-absorbing $C^*$-algebra, form an…

Operator Algebras · Mathematics 2019-10-03 Marius Dadarlat , Ulrich Pennig

This paper investigates the homology of the Brauer algebras, interpreted as appropriate Tor-groups, and shows that it is closely related to the homology of the symmetric group. Our main results show that when the defining parameter of the…

Algebraic Topology · Mathematics 2023-06-13 Rachael Boyd , Richard Hepworth , Peter Patzt

In this paper, we present a conjecture on the degree of unipotent characters in the cohomology of particular Deligne-Lusztig varieties for groups of Lie type, and derive consequences of it. These degrees are a necessary piece of data in the…

Representation Theory · Mathematics 2015-03-19 David A. Craven

In this paper, we define a generalization of the Brauer groups by using Bloch's cycle complex on etale site. We prove the Gersten conjecture of generalized Brauer group on some cases. As an application we prove the Gersten conjecture of the…

Number Theory · Mathematics 2016-11-08 Makoto Sakagaito

Let $G$ be a group and $S$ a unital epsilon-strongly $G$-graded algebra. We construct spectral sequences converging to the Hochschild (co)homology of $S$. Each spectral sequence is expressed in terms of the partial group (co)homology of $G$…

K-Theory and Homology · Mathematics 2025-07-23 Emmanuel Jerez