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We furnish any category of a universal (co)homology theory. Universal (co)homologies and universal relative (co)homologies are obtained by showing representability of certain functors and take values in $R$-linear abelian categories of…

Algebraic Geometry · Mathematics 2023-05-10 L. Barbieri-Viale

We study the representation theory of the increasing monoid. Our results provide a fairly comprehensive picture of the representation category: for example, we describe the Grothendieck group (including the effective cone), classify…

Representation Theory · Mathematics 2018-12-27 Sema Güntürkün , Andrew Snowden

We use ring-theoretic methods and methods from the theory of skew braces to produce set-theoretic solutions to the reflection equation. We also use set-theoretic solutions to construct solutions to the parameter-dependent reflection…

Rings and Algebras · Mathematics 2020-01-16 Agata Smoktunowicz , Leandro Vendramin , Robert Weston

We give a general method to build categories of combinatorial manifolds, i.e. categories of combinatorial objects satisfying some local property at every "point", as coreflective subcategories of categories of relational presheaves. To do…

Category Theory · Mathematics 2026-05-21 Yorgo Chamoun

This second part comes to the construction of the spectrum associated to a situation of multi-adjunction. Exploiting a geometric understanding of its multi-versal property, the spectrum of an object is obtained as the spaces of local units…

Category Theory · Mathematics 2021-04-07 Axel Osmond

In this paper, we provide a general framework for counting geometric structures in pseudo-random graphs. As applications, our theorems recover and improve several results on the finite field analog of questions originally raised in the…

Combinatorics · Mathematics 2025-04-30 Thang Pham , Steven Senger , Michael Tait , Vu Thi Huong Thu

This work presents a way to associate a Grothendieck site structure to a category endowed with a unique factorisation system of its arrows. In particular this recovers the Zariski and Etale topologies and others related to Voevodsky's…

Algebraic Geometry · Mathematics 2009-10-22 Mathieu Anel

For all classical groups (and for their analogs in infinite dimension or over general base fields or rings) we construct certain contractions, called "homotopes". The construction is geometric, using as ingredient involutions of associative…

Rings and Algebras · Mathematics 2010-05-19 Wolfgang Bertram , Michael Kinyon

For all classical groups (and for their analogs in infinite dimension or over general base fields or rings) we construct certain contractions, called "homotopes". The construction is geometric, using as ingredient involutions of associative…

Rings and Algebras · Mathematics 2010-05-31 Wolfgang Bertram , Michael Kinyon

We give a version of geometric motivic integration that specializes to p-adic integration via point counting. This has been done before for stable sets; we extend this to more general sets. The main problem in doing this is that it requires…

Algebraic Geometry · Mathematics 2008-10-27 Karl Rökaeus

Ever since the introduction of motivic homotopy theory, as a well-proposed approximation of Grothendieck's dream, algebraic geometers then have the chance to study schemes via a homotopy theory. However topologists also found that lifting…

Algebraic Geometry · Mathematics 2025-12-09 Xin Tong

We introduce a new method for expanding an abelian category and study it using recollements. In particular, we give a criterion for the existence of cotilting objects. We show, using techniques from noncommutative algebraic geometry, that…

Representation Theory · Mathematics 2015-05-11 Boris Lerner , Steffen Oppermann

We show connections between a special type of addition formulas and a theorem of Stieltjes and Rogers. We use different techniques to derive the desirable addition formulas. We apply our approach to derive special addition theorems for…

Classical Analysis and ODEs · Mathematics 2007-12-27 Mourad E. H. Ismail , Jiang Zeng

Grothendieck proved that if $f:X\longrightarrow Y$ is a proper morphism of nice schemes, then $Rf_*$ has a right adjoint, which is given as tensor product with the relative canonical bundle. The original proof was by patching local data.…

alg-geom · Mathematics 2015-06-30 Amnon Neeman

Non-trivial examples of generalized paracomplex structures (in the sense of the generalized geometry \`a la Hitchin) are constructed applying the twistor space construction scheme.

Differential Geometry · Mathematics 2024-09-10 Johann Davidov

Morphisms between (formal) contexts are certain pairs of maps, one between objects and one between attributes of the contexts in question. We study several classes of such morphisms and the connections between them. Among other things, we…

Category Theory · Mathematics 2014-07-03 Marcel Erné

We survey the existing parts of a classification of finite groups generated by orthogonal transformations in a finite-dimensional Euclidean space whose fixed point subspace has codimension one or two and extend it to a complete…

Group Theory · Mathematics 2017-11-02 Christian Lange , Marina A. Mikhailova

Grothendieck Duality -- the theory of the twisted inverse image pseudofunctor (-)^! over a suitable category of scheme-maps -- can be developed concretely, with emphasis on explicit constructions, or abstractly, with emphasis on…

Algebraic Geometry · Mathematics 2025-03-25 Joseph Lipman

We study the circumstances under which one can reconstruct a stack from its associated functor of isomorphism classes. This is possible surprisingly often: we show that many of the standard examples of moduli stacks are determined by their…

Algebraic Geometry · Mathematics 2018-06-18 Max Lieblich , Brian Osserman

We prove a formula for the structure sheaf of a quiver variety in the Grothendieck ring of its embedding variety. This formula generalizes and gives new expressions for Grothendieck polynomials. We furthermore conjecture that the…

Algebraic Geometry · Mathematics 2007-05-23 Anders Skovsted Buch