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We study the moment maps of a smooth projective toric variety. In particular, we characterize when the moment map coming from the quotient construction is equal to a weighted Fubini-Study moment map. This leads to an investigation into…

Algebraic Geometry · Mathematics 2020-04-07 Patrick Clarke , David A. Cox

We give two simple geometric constructions of a smooth family of projective varieties with central fiber isomorphic to the horospherical variety of type $\mathrm{G}_2$ and all other fibers isomorphic to the isotropic orthogonal Grassmannian…

Algebraic Geometry · Mathematics 2023-02-21 Alexander Kuznetsov

Let $\Delta =\left(\begin{smallmatrix} A & {_AN_B}\\ {_BM_A} & B \\\end{smallmatrix}\right)$ be a Morita ring with $M\otimes_{A}N=0=N\otimes_{B}M$.We first study how to construct (complete) duality pairs of $\Delta$-modules using (complete)…

Rings and Algebras · Mathematics 2023-05-02 Yajun Ma , Jiafeng Lü , Huanhuan Li , Jiangsheng Hu

We prove the existence of pl-flips.

Algebraic Geometry · Mathematics 2008-08-15 Christopher D. Hacon , James McKernan

The purpose of this paper is to compute the minimal fibering degree of an arbitrary projective toric variety. We prove that it equals the lattice width of the associated polytope. This gives a complete answer to a question asked in a recent…

Algebraic Geometry · Mathematics 2023-08-09 Audric Lebovitz , David Stapleton

In this article we introduce a new family of lattice polytopes with rational linear precision. For this purpose, we define a new class of discrete statistical models that we call multinomial staged tree models. We prove that these models…

Combinatorics · Mathematics 2022-08-10 Isobel Davies , Eliana Duarte , Irem Portakal , Miruna-Stefana Sorea

In this paper, we study the minimal model theory for threefolds in mixed characteristic. As a generalization of a result of Kawamata, we show that the MMP holds for strictly semi-stable schemes over an excellent Dedekind scheme $V$ of…

Algebraic Geometry · Mathematics 2023-01-09 Teppei Takamatsu , Shou Yoshikawa

The Cox ring provides a coordinate system on a toric variety analogous to the homogeneous coordinate ring of projective space. Rational maps between projective spaces are described using polynomials in the coordinate ring, and we generalise…

Algebraic Geometry · Mathematics 2014-06-02 Gavin Brown , Jarosław Buczyński

We describe a general program for studying the dynamics of surjective endomorphisms of algebraic varieties that are amenable to techniques from the minimal model program. We obtain density results on the pre-periodic points of surjective…

Algebraic Geometry · Mathematics 2022-12-06 Brett Nasserden

We prove that for every reductive algebraic group $H$ with centre of positive dimension and every integer $K$ there is a smooth and projective variety $X$ and an algebraic $H$-torsor $P \to X$ such that the classifying map $X \to \Bclass H$…

Algebraic Geometry · Mathematics 2009-05-12 Torsten Ekedahl

We characterize the smallest finite spaces with the same homotopy groups of the spheres. Similarly, we describe the minimal finite models of any finite graph. We also develop new combinatorial techniques based on finite spaces to study…

Algebraic Topology · Mathematics 2007-05-23 Jonathan Ariel Barmak , Elias Gabriel Minian

We study semi-stable degenerations of toric varieties determined by certain partitions of their moment polytopes. Analyzing their defining equations we prove a property of uniqueness.

Algebraic Geometry · Mathematics 2007-12-21 Marina Marchisio , Vittorio Perduca

We introduce a characteristic vector with respect to a regular triangulation of the momentum polytope to compute the Hurwitz polytope of a given smooth toric variety. As a result, we prove that the convex hull of such vectors of all regular…

Algebraic Geometry · Mathematics 2023-02-21 Ryoma Ogusu , Yuji Sano

The Minimal Model Program offers natural higher-dimensional analogues of stable $n$-pointed curves and maps: stable pairs consisting of a projective variety $X$ of dimension $\ge2$ and a divisor $B$, that should satisfy a few simple…

Algebraic Geometry · Mathematics 2007-05-23 Valery Alexeev

We reduce the problem of the projective normality of polarized abelian varieties to check the rank of very explicit matrices. This allow us to prove some results on normal generation of primitive line bundles on abelian threefolds and…

Algebraic Geometry · Mathematics 2007-05-23 Luis Fuentes Garcia

Let $f\colon X \to \mathbb{A}^1_t$ be an affine flat morphism of finite type, and let $V = f^{-1}(0)$. Then, we obtain a morphism of log schemes $f\colon (X|V) \to (\mathbb{A}^1_t|0)$. In this article, we develop algorithmic tools to study…

Algebraic Geometry · Mathematics 2026-02-20 Simon Felten

In previous work by Coates, Galkin, and the authors, the notion of mutation between lattice polytopes was introduced. Such a mutation gives rise to a deformation between the corresponding toric varieties. In this paper we study one-step…

Algebraic Geometry · Mathematics 2022-10-28 Mohammad Akhtar , Alexander Kasprzyk

We show the validity of the Minimal Model Program for threefolds in characteristic five.

Algebraic Geometry · Mathematics 2019-12-02 Christopher Hacon , Jakub Witaszek

For each strongly connected finite-dimensional (pure) simplicial complex we construct a finite group, the group of projectivities of the complex, which is a combinatorial but not a topological invariant. This group is studied for…

Combinatorics · Mathematics 2007-05-23 Michael Joswig

Under semi-weak and weak compatibility of bimodules, we establish sufficient and necessary conditions of Gorenstein-projective modules over rings of Morita contexts with one bimodule homomorphism zero. This generalises and extends results…

Representation Theory · Mathematics 2022-08-24 Qianqian Guo , Changchang Xi