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Cases of Deligne's companion conjecture for normal schemes over finite fields have been proven by L. Lafforgue, Drinfeld, and Zheng in recent years: L. Lafforgue proved the conjecture for curves, Drinfeld proved the conjecture for all…

Number Theory · Mathematics 2026-01-09 Min Shi

Given an $n$-gon, the poset of all collections of pairwise non-crossing diagonals is isomorphic to the face poset of some convex polytope called \textit{associahedron}. We replace in this setting the $n$-gon (viewed as a disc with $n$…

Geometric Topology · Mathematics 2018-11-14 Joseph Gordon , Gaiane Panina

We provide a uniform construction of "mixed versions" or "graded lifts" in the sense of Beilinson-Ginzburg-Soergel which works for arbitrary Artin stacks. In particular, we obtain a general construction of graded lifts of many categories…

Algebraic Geometry · Mathematics 2025-12-10 Quoc P. Ho , Penghui Li

We study the multiplicative structure of orbifold Hochschild cohomology in an attempt to generalize the results of Kontsevich and Calaque-Van den Bergh relating the Hochschild and polyvector field cohomology rings of a smooth variety. We…

Algebraic Geometry · Mathematics 2021-01-19 Andrei Caldararu , Shengyuan Huang

Higher category theory is an exceedingly active area of research, whose rapid growth has been driven by its penetration into a diverse range of scientific fields. Its influence extends through key mathematical disciplines, notably homotopy…

Category Theory · Mathematics 2017-07-07 Simona Paoli

We prove that the derived category of a Grothendieck abelian category has a unique dg enhancement. Under some additional assumptions, we show that the same result holds true for its subcategory of compact objects. As a consequence, we…

Algebraic Geometry · Mathematics 2018-12-06 Alberto Canonaco , Paolo Stellari

Standard results from non-abelian cohomology theory specialize to a theory of torsors and stacks for cosimplicial groupoids. The space of global sections of the stack completion of a cosimplicial groupoid $G$ is weakly equivalent to the…

Algebraic Topology · Mathematics 2019-06-17 J. F. Jardine

Given a diagram of schemes, we can ask if a geometric object over one of them can be built from descent data (usually objects of the same type over the various other schemes in the diagram, together with compatibility isomorphisms). Using…

Algebraic Geometry · Mathematics 2015-05-22 Daniel Schäppi

Let X be a proper scheme over a field k which satisfies Serre's condition S2 and G a reductive group over k. We prove that the functor of principal G-bundles defined away from a non-fixed closed subset in X of codimension at least 3, is an…

Algebraic Geometry · Mathematics 2008-10-02 Vladimir Baranovsky

The absence of intrinsic adjacency relations and orientation systems in hypergraphs creates fundamental challenges for constructing sheaf Laplacians of arbitrary degrees. We resolve these limitations through symmetric simplicial sets…

Machine Learning · Computer Science 2025-08-01 Seongjin Choi , Gahee Kim , Yong-Geun Oh

For a compact oriented smooth $n$-manifold $M$ and a codimension-$1$ homology class $\phi \in \operatorname{H}_{n-1}(M, \partial M)$, we investigate a simplicial complex $\mathcal{S}^\dagger(M, \phi)$ relating the properly embedded…

Geometric Topology · Mathematics 2022-02-23 Gerrit Herrmann , José Pedro Quintanilha

The category of affine schemes is a tangent category whose tangent bundle functor is induced by K\"ahler differentials, providing a direct link between algebraic geometry and tangent category theory. Moreover, this tangent bundle functor is…

Category Theory · Mathematics 2026-04-21 Marcello Lanfranchi , Jean-Simon Pacaud Lemay

For a noetherian scheme, we introduce its unbounded stable derived category. This leads to a recollement which reflects the passage from the bounded derived category of coherent sheaves to the quotient modulo the subcategory of perfect…

Algebraic Geometry · Mathematics 2007-05-23 Henning Krause

We use the definition of a simplicial cycle to define an odd-cycle-free facet complex (hypergraph). These are facet complexes that do not contain any cycles of odd length. We show that besides one class of such facet complexes, all of them…

Commutative Algebra · Mathematics 2007-05-23 Massimo Caboara , Sara Faridi

We study algebraicity and smoothness of fixed point stacks for flat group schemes which have a finite composition series whose factors are either reductive or proper, flat, finitely presented, acting on algebraic stacks with affine,…

Algebraic Geometry · Mathematics 2022-09-19 Matthieu Romagny

We introduce a method of finding large non-positively curved subcomplexes in certain spherical Deligne complexes, which is effective for studying fillings of certain 6-cycles in spherical Deligne complexes. As applications, we show the…

Group Theory · Mathematics 2025-01-17 Jingyin Huang

We introduce the notion of homotopically discrete n-fold category as an n-fold generalization of a groupoid with no non-trivial loops. We give two equivalent descriptions of this structure: in terms of a Segal-type model and in terms of…

Category Theory · Mathematics 2016-05-18 Simona Paoli

We give combinatorial models for complex, smooth, non-spherical, generic, irreducible representations of the group G=PGL(2,F), where F is a non-archimedean locally compact field. They use the graphs X_k lying above the tree of G, introduced…

Representation Theory · Mathematics 2007-05-23 Paul Broussous

In order to develop the foundations of logarithmic derived geometry, we introduce a model category of logarithmic simplicial rings and a notion of derived log \'etale maps and use this to define derived log stacks.

Algebraic Geometry · Mathematics 2016-04-13 Steffen Sagave , Timo Schürg , Gabriele Vezzosi

In this paper we investigate the functoriality properties of map-graded Hochschild complexes. We show that the category MAP of map-graded categories is naturally a stack over the category of small categories endowed with a certain…

K-Theory and Homology · Mathematics 2013-04-30 Wendy Lowen