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In this short note we prove that the number of deformation types of compact hyperkaehler manifolds with prescribed second cohomology and second Chern class is finite. The proof uses the finiteness result of Kollar and Matsusaka, a formula…

Algebraic Geometry · Mathematics 2007-05-23 Daniel Huybrechts

We realise Buchweitz and Flenner's semiregularity map (and hence a fortiori Bloch's semiregularity map) for a smooth variety $X$ as the tangent of a generalised Abel--Jacobi map on the derived moduli stack of perfect complexes on $X$. The…

Algebraic Geometry · Mathematics 2024-11-06 J. P. Pridham

In this note we prove a conjecture of Kashiwara, which states that the Euler class of a coherent analytic sheaf F on a complex manifold X is the product of the Chern character of F with the Todd class of X. As a corollary, we obtain a…

Algebraic Geometry · Mathematics 2017-10-10 Julien Grivaux

A remarkable result of Peter O'Sullivan asserts that the algebra epimorphism from the rational Chow ring of an abelian variety to its rational Chow ring modulo numerical equivalence admits a (canonical) section. Motivated by Beauville's…

Algebraic Geometry · Mathematics 2019-07-26 Lie Fu , Charles Vial

The third author has shown that Shelah's eventual categoricity conjecture holds in universal classes: class of structures closed under isomorphisms, substructures, and unions of chains. We extend this result to the framework of…

Logic · Mathematics 2019-05-20 Nathanael Ackerman , Will Boney , Sebastien Vasey

We give sufficient conditions which ensure that a functor of finite length from an additive category to finite-dimensional vector spaces has a projective resolution whose terms are finitely generated. For polynomial functors, we study also…

K-Theory and Homology · Mathematics 2023-07-14 Aurélien Djament , Antoine Touzé

One of the classic results of group theory is the so-called Schur theorem. It states that if the central factor-group $G/\zeta(G)$ of a group $G$ is finite, then its derived subgroup $[G,G]$ is also finite. This result has numerous…

Rings and Algebras · Mathematics 2024-04-30 P. Ye. Minaiev , O. O. Pypka , I. V. Shyshenko

The purpose of this note is to prove that the Chow motive of the Fano surface of lines on the smooth cubic threefold is finite-dimensional in the sense of Kimura. This gives an example of a smooth projective variety that is not dominated by…

Algebraic Geometry · Mathematics 2016-02-23 Humberto Diaz

The paper concerns an analogue of the famous Schur multiplier in the context of associative algebras and a measure of how far its dimension is from being maximal. Applying a methodology from Lie theory, we characterize all…

Rings and Algebras · Mathematics 2023-02-06 Erik Mainellis

In 1995, Koll\'ar conjectured that a smooth complex projective $n$-fold $X$ with generically large fundamental group has Euler characteristic $\chi(X, K_X)\geq 0$. In this paper, we prove the conjecture assuming $X$ has linear fundamental…

Algebraic Geometry · Mathematics 2025-08-07 Ya Deng , Botong Wang

M.R.Jones and J.Wiegold in [3] have shown that if $G$ is a finite group with a subgroup $H$ of finite index $n$, then the $n$-th power of Schur multiplier of $G$, $M(G)^n$, is isomorphic to a subgroup of $M(H)$. In this paper we prove a…

Group Theory · Mathematics 2011-04-05 Mohammad Reza Rajabzadeh Moghaddam , Behrooz Mashayekhy , Saeed Kayvanfar

In a recent article, D. Kazhdan and A. Yom Din conjectured the validity of an asymptotic form of Schur's orthogonality for tempered irreducible unitary representations of semisimple groups defined over local fields. In the non-Archimedean…

Representation Theory · Mathematics 2025-09-03 Anne-Marie Aubert , Alfio Fabio La Rosa

In this paper, we study a variation of a conjecture of Debarre on positivity of cotangent bundles of complete intersections. We establish the ampleness of Schur powers of cotangent bundles of generic complete intersections in projective…

Algebraic Geometry · Mathematics 2021-01-11 Antoine Etesse

Given a Henselian and Japanese discrete valuation ring $A$ and a flat and projective $A$-scheme $X$, we follow the approach of Biswas-dos Santos to introduce a full subcategory of coherent modules on $X$ which is then shown to be Tannakian.…

Algebraic Geometry · Mathematics 2019-04-25 Phung Ho Hai , Joao Pedro dos Santos

In the moduli space of polarized varieties the same unpolarized variety can occur multiple times However, for K3 surfaces, compact hyperk\"ahler manifolds, and abelian varieties the number is finite. This may be viewed as a consequence of…

Algebraic Geometry · Mathematics 2019-08-20 Daniel Huybrechts

The recently developed theory of Schur rings over a finite cyclic group is generalized to Schur rings over a ring R being a product of Galois rings of coprime characteristics. It is proved that if the characteristic of R is odd, then as in…

Combinatorics · Mathematics 2015-05-07 Sergei Evdokimov , Ilya Ponomarenko

In this paper we introduce the concept of purely infinite rings, which in the simple case agrees with the already existing notion of pure infiniteness. We establish various permanence properties of this notion, with respect to passage to…

Rings and Algebras · Mathematics 2008-06-26 Gonzalo Aranda Pino , Ken Goodearl , Francesc Perera , Mercedes Siles Molina

We provide a universal characterization of the construction taking a scheme $X$ to its stable $\infty$-category $\text{Mot}(X)$ of noncommutative motives, patterned after the universal characterization of algebraic K-theory due to…

K-Theory and Homology · Mathematics 2024-08-21 Aaron Mazel-Gee , Reuben Stern

Let $X$ be a compact smooth manifold, possibly with boundary. Denote by $X_1,\dots,X_r$ the connected components of $X$. Assume that the integral cohomology of $X$ is torsion free and supported in even degrees. We prove that there exists a…

Differential Geometry · Mathematics 2014-05-30 Ignasi Mundet i Riera

A vector bundle E on a projective variety X is called finite if it satisfies a nontrivial polynomial equation with integral coefficients. A theorem of Nori implies that E is finite if and only if the pullback of E to some finite etale…

Algebraic Geometry · Mathematics 2023-06-22 Indranil Biswas , Vamsi Pritham Pingali