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We show that representations of convolution algebras such as Lustzig's graded affine Hecke algebra or the quiver Hecke algebra and quiver Schur algebra in (affine) type A can be realised in terms of certain equivariant motivic sheaves…

Representation Theory · Mathematics 2021-11-16 Jens Niklas Eberhardt , Catharina Stroppel

We give a geometric construction of tilting perverse sheaves using stratified Morse theory, torus actions, and nearby cycles.

Representation Theory · Mathematics 2007-05-23 David Nadler

We define the singular support of an $\ell$-adic sheaf on a smooth variety over any field. To do this, we combine Beilinson's construction of the singular support for torsion \'etale sheaves with Hansen and Scholze's theory of universal…

Algebraic Geometry · Mathematics 2024-12-25 Owen Barrett

If $X$ is a smooth toric variety over an algebraically closed field of positive characteristic and $L$ is an invertible sheaf on $X$, it is known that $F_* L$, the push-forward of $L$ along the Frobenius morphism of $X$, is a direct sum of…

Algebraic Geometry · Mathematics 2013-03-26 Piotr Achinger

Let $X$ be a normal projective variety and $f:X\to X$ a non-isomorphic polarized endomorphism. We give two characterizations for $X$ to be a toric variety. First we show that if $X$ is $\mathbb{Q}$-factorial and $G$-almost homogeneous for…

Algebraic Geometry · Mathematics 2019-08-05 Sheng Meng , De-Qi Zhang

Let $X$ be a smooth scheme over a finite field of characteristic $p$. In answer to a conjecture of Deligne, we establish that for any prime $\ell \neq p$, an $\ell$-adic Weil sheaf on $X$ which is algebraic (or irreducible with finite…

Number Theory · Mathematics 2026-03-25 Kiran S. Kedlaya

For (X,L) a polarized toric variety and G a torus of automorphisms of (X,L), denote by Y the GIT quotient X/G. We define a family of fully faithful functors from the category of torus equivariant reflexive sheaves on Y to the category of…

Algebraic Geometry · Mathematics 2021-12-15 Andrew Clarke , Carl Tipler

We study motivic Chern classes of cones. First we show examples of projective cones of smooth curves such that their various $K$-classes (sheaf theoretic, push-forward and motivic) are all different. Then we show connections between the…

Algebraic Geometry · Mathematics 2020-06-22 László M. Fehér

Toric prevarieties are non-separated analogues of toric varieties. Perling \cite{Perling_equivariant_sheaves_tor_var} provided a combinatorial description of equivariant quasicoherent sheaves on toric varieties, extending earlier ideas of…

Algebraic Geometry · Mathematics 2026-05-05 Jyoti Dasgupta , Kartik Roy

In this paper we study Bayesian networks from a commutative algebra perspective. We characterize a class of toric Bayesian nets, and provide the first example of a Bayesian net which is proved non-toric under any linear change of variables.…

Statistics Theory · Mathematics 2023-07-24 Lisa Nicklasson

We investigate combinatorial aspects of exceptional sequences in the derived category of coherent sheaves on certain smooth and complete algebraic surfaces. We show that to any such sequence there is canonically associated a complete toric…

Algebraic Geometry · Mathematics 2022-10-25 Markus Perling

A conjecture of Morel asserts that the sheaf of $\mathbb A^1$-connected components of a space is $\mathbb A^1$-invariant. Using purely algebro-geometric methods, we determine the sheaf of $\mathbb A^1$-connected components of a smooth…

Algebraic Geometry · Mathematics 2022-04-20 Chetan Balwe , Anand Sawant

A framed symplectic sheaf on a smooth projective surface $X$ is a torsion-free sheaf $E$ together with a trivialization on a divisor $D\subseteq X$ and a morphism $\Lambda^{2}E\rightarrow\mathcal{O}_{X}$ satisfying some additional…

Algebraic Geometry · Mathematics 2016-04-29 Jacopo Scalise

In this paper we give an inherently toric description of a special class of sheaves (known as equivariant sheaves) over toric varieties, due in part to A. A. Klyachko. We apply this technology to heterotic compactifications, in particular…

High Energy Physics - Theory · Physics 2016-10-04 A. Knutson , E. Sharpe

We prove that a smooth rationally connected projective threefold of Picard number two is toric if and only if it admits an int-amplified endomorphism. As a corollary, we show that a totally invariant smooth curve of a non-isomorphic…

Algebraic Geometry · Mathematics 2025-06-18 Zelong Chen , Sheng Meng , Guolei Zhong

We investigate toric varieties defined by arrangements of hyperplanes and call them strongly symmetric. The smoothness of such a toric variety translates to the fact that the arrangement is crystallographic. As a result, we obtain a…

Algebraic Geometry · Mathematics 2015-01-14 M. Cuntz , Y. Ren , G. Trautmann

We investigate the behaviour of tilting sheaves under pushforward by a finite Galois morphism. We determine conditions under which such a pushforward of a tilting sheaf is a tilting sheaf. We then produce some examples of Severi Brauer flag…

Algebraic Geometry · Mathematics 2018-11-30 Ajneet Dhillon , Nicole Lemire , Youlong Yan

In this paper, we describe a way to construct cycles which represent the Todd class of a toric variety. Given a lattice with an inner product we assign a rational number m(s) to each rational polyhedral cone s in the lattice, such that for…

Algebraic Geometry · Mathematics 2007-05-23 James Pommersheim , Hugh Thomas

We formulate a conjecture characterizing smooth projective varieties in positive characteristic whose Frobenius morphism can be lifted modulo $p^2$ - we expect that such varieties, after a finite \'etale cover, admit a toric fibration over…

Algebraic Geometry · Mathematics 2021-02-08 Piotr Achinger , Jakub Witaszek , Maciej Zdanowicz

We propose an algebraic method for the classification of branched Galois covers of a curve $X$ focused on studying Galois ring extensions of its geometric adele ring $\A_{X}$. As an application, we deal with cyclic covers; namely, we…

Algebraic Geometry · Mathematics 2026-03-16 Luis Manuel Navas Vicente , Francisco J. Plaza Martin