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In this paper, we define $\Lambda$-quot-functors on Deligne-Mumford stacks. We prove that the $\Lambda$-quot-functor is representable by an algebraic space. Then, we construct the moduli space of $\Lambda$-modules on a projective…

Algebraic Geometry · Mathematics 2020-11-16 Hao Sun

We show that the continuous \'etale cohomology groups $H^n_{\mathrm{cont}}(X,\mathbf{Z}_l(n))$ of smooth varieties $X$ over a finite field $k$ are spanned as $\mathbf{Z}_l$-modules by the $n$-th Milnor $K$-sheaf locally for the Zariski…

Algebraic Geometry · Mathematics 2025-12-03 Bruno Kahn

In this semi-expository note, we give a new proof of a structure theorem due to Shimura for nearly holomorphic modular forms on the complex upper half plane. Roughly speaking, the theorem says that the space of all nearly holomorphic…

Number Theory · Mathematics 2015-01-06 Ameya Pitale , Abhishek Saha , Ralf Schmidt

The de Rham comparison theorem for varieties, first proved by Faltings, gives the de Rham cohomology of a variety in terms of its p-adic etale cohomology. We extend this theorem to proper, smooth Deligne-Mumford stacks. Two approaches are…

Algebraic Geometry · Mathematics 2008-09-09 Theo van den Bogaart

We study the relationship between derived categories of factorizations on gauged Landau-Ginzburg models related by variations of the linearization in Geometric Invariant Theory. Under assumptions on the variation, we show the derived…

Algebraic Geometry · Mathematics 2014-05-14 Matthew Ballard , David Favero , Ludmil Katzarkov

Let $\mathcal{X}_1$ and $\mathcal{X}_2$ be smooth proper Deligne-Mumford stacks with projective coarse moduli spaces. We prove a formula for orbifold Gromov-Witten invariants of the product stack $\mathcal{X}_1\times \mathcal{X}_2$ in terms…

Algebraic Geometry · Mathematics 2016-06-16 Elena Andreini , Yunfeng Jiang , Hsian-Hua Tseng

We prove the existence of tilting objects on some global quotient stacks. As a consequence we provide further evidence for a conjecture on the Rouquier dimension of derived categories formulated by Orlov.

Algebraic Geometry · Mathematics 2017-04-07 Saša Novaković

The representability theorem for stacks, due to Artin in the underived setting and Lurie in the derived setting, gives conditions under which a stack is representable by an $n$-geometric stack. In recent work of Ben-Bassat, Kelly, and…

Algebraic Geometry · Mathematics 2025-11-17 Rhiannon Savage

We prove the cone theorem for varieties with LCIQ singularities using deformation theory of stable maps into Deligne-Mumford stacks. We also obtain a sharper bound on $-(K_X+D)$-degree of $(K_X+D)$-negative extremal rays for projective…

Algebraic Geometry · Mathematics 2009-08-20 Jiun-Cheng Chen , Hsian-Hua Tseng

We study stacks of slope-semistable twisted sheaves on orbisurfaces with projective coarse spaces and prove that in certain cases they have many of the asymptotic properties enjoyed by the moduli of slope-semistable sheaves on smooth…

Algebraic Geometry · Mathematics 2018-06-18 Max Lieblich

We show how a quasi-smooth derived enhancement of a Deligne-Mumford stack X naturally endows X with a functorial perfect obstruction theory in the sense of Behrend-Fantechi. This result is then applied to moduli of maps and perfect…

Algebraic Geometry · Mathematics 2011-11-07 Timo Schürg , Bertrand Toën , Gabriele Vezzosi

Suppose $X$ is a smooth quasiprojective variety over $\cc$ and $\rho : \pi _1(X,x) \to SL(2,\cc)$ is a Zariski-dense representation with quasiunipotent monodromy at infinity. Then $\rho$ factors through a map $X\to Y$ with $Y$ either a…

Algebraic Geometry · Mathematics 2014-01-14 Kevin Corlette , Carlos T. Simpson

We give a completely algebraic proof of the Bogomolov-Tian-Todorov theorem. More precisely, we shall prove that if X is a smooth projective variety with trivial canonical bundle defined over an algebraically closed field of characteristic…

Algebraic Geometry · Mathematics 2016-02-17 Donatella Iacono , Marco Manetti

We generalize the notion of expanded degenerations and pairs for a simple degeneration or smooth pair to the case of smooth Deligne-Mumford stacks. We then define stable quotients on the classifying stacks of expanded degenerations and…

Algebraic Geometry · Mathematics 2017-09-11 Zijun Zhou

We introduce the notion of almost representations of Lie algebras and quantum tori, and establish an Ulam-stability type phenomenon: every irreducible almost representation is close to a genuine irreducible representation. As an…

Mathematical Physics · Physics 2022-02-01 Louis Ioos , David Kazhdan , Leonid Polterovich

Due to the work of many authors in the last decades, given an algebraic orbifold (smooth proper Deligne-Mumford stack with trivial generic stabilizer), one can construct its orbifold Chow ring and orbifold Grothendieck ring, and relate them…

Algebraic Geometry · Mathematics 2019-10-08 Lie Fu , Manh Toan Nguyen

In this paper, we propose a definition of the moduli stack of stable relative ideal sheaves, and prove that it is a separated and proper Deligne-Mumford stack. It is the first part of the project of relative Donaldson-Thomas theory of ideal…

Algebraic Geometry · Mathematics 2020-01-21 Baosen Wu

We present reformulation of Mathieu's result on representing cohomology classes of symplectic manifold with symplectically harmonic forms. We apply it to the case of foliated manifolds with transversally symplectic structure and to…

Differential Geometry · Mathematics 2010-01-15 Lukasz Bak , Andrzej Czarnecki

A theorem of Bondal and Kapranov lifts representations of cohomological functors from semiorthogonal decompositions of triangulated categories. We present a version of this result for triangulated functors. To this end, we introduce…

Category Theory · Mathematics 2025-05-19 Jonas Frank , Mathias Schulze

Recently, by studying an explicit basis, K\"ock and Laurent give the decomposition of the $\overline{\mathbb{F}}_q[\mathrm{SL}_2(\mathbb{F}_q)]$-module of holomorphic forms on the Drinfeld curve. We present a crystalline cohomological proof…

Representation Theory · Mathematics 2024-11-27 Zhe Chen , Yushan Pan