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We study standard monomial bases for Richardson varieties inside the flag variety. In general, writing down a standard monomial basis for a Richardson variety can be challenging, as it involves computing so-called defining chains or key…

Algebraic Geometry · Mathematics 2022-05-10 Narasimha Chary Bonala , Oliver Clarke , Fatemeh Mohammadi

Some examples of naturally arising multisum $q$-series which turn out to have representations as fermionic single sums are presented. The resulting identities are proved using transformation formulas from the theory of basic hypergeometric…

Classical Analysis and ODEs · Mathematics 2018-12-14 Andrew V. Sills

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

When the standard representation of a crystallographic Coxeter group G (with string diagram) is reduced modulo the integer d>1, one obtains a finite group G^d which is often the automorphism group of an abstract regular polytope. Building…

Combinatorics · Mathematics 2008-05-23 B. Monson , Egon Schulte

Based on the notion of vectors and linear subspaces for a matroid, we develop a theory of flats and hyperplane arrangements for T-matroids, where T is a tract. This leads to several cryptomorphic descriptions of T-matroids: in terms of its…

Combinatorics · Mathematics 2026-03-11 Jannis Koulman , Oliver Lorscheid

We study mapping properties of operators with kernels defined via a combination of continuous and discrete orthogonal polynomials, which provide an abstract formulation of quantum (q-) Fourier type systems. We prove Ismail conjecture…

Classical Analysis and ODEs · Mathematics 2007-05-23 Luis Daniel Abreu

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 $V$ be a complex algebraic hypersurface defined by a polynomial $f$ with Newton polytope $\Delta$. It is well known that the spine of its amoeba has a structure of a tropical hypersurface. We prove in this paper that there exists a…

Algebraic Geometry · Mathematics 2009-12-05 Mounir Nisse

A subunit in a monoidal category is a subobject of the monoidal unit for which a canonical morphism is invertible. They correspond to open subsets of a base topological space in categories such as those of sheaves or Hilbert modules. We…

Category Theory · Mathematics 2020-06-22 Pau Enrique Moliner , Chris Heunen , Sean Tull

Let $X$ be a toric variety. Rationally Borel-Moore homology of $X$ is isomorphic to the homology of the Koszul complex $A^T_*(X)\otimes \Lambda^\x M$, where $A^T_*(X)$ is the equivariant Chow group and $M$ is the character group of $T$.…

Algebraic Geometry · Mathematics 2007-05-23 Andrzej Weber

Topologically, compact toric varieties can be constructed as identification spaces: they are quotients of the product of a compact torus and the order complex of the fan. We give a detailed proof of this fact, extend it to the non-compact…

Algebraic Topology · Mathematics 2010-10-25 Matthias Franz

In this paper we develop a theory of volume polynomials of generalized virtual polytopes based on the study of topology of affine subspace arrangements in a real Euclidean space. We apply this theory to obtain a topological version of the…

Algebraic Topology · Mathematics 2022-04-04 Askold Khovanskii , Ivan Limonchenko , Leonid Monin

We introduce a toric version of the sheaf of logarithmic vector fields along a divisor of a simplicial toric variety. The notion is also relevant for algebraically independent families of polynomials in the Cox ring. We provide a…

Algebraic Geometry · Mathematics 2024-08-21 Daniele Faenzi , Marcos Jardim , William D Montoya

We propose to take a look at a new approach to the study of integral polyhedra. The main idea is to give an integral representation, or matrix model representation, for the key combinatorial characteristics of integral polytopes. Based on…

Combinatorics · Mathematics 2022-10-20 Aleksey Andreev

In this paper, we study the (singular) universal cover of an affine hypertoric variety. We show that it is given by another affine hypertoric variety, and taking the universal cover corresponds to taking the simplification of the associated…

Algebraic Geometry · Mathematics 2019-10-29 Takahiro Nagaoka

It has been recently shown that the iteration of Nash modification on not necessarily normal toric varieties corresponds to a purely combinatorial algorithm on the generators of the semigroup associated to the toric variety. We will show…

Algebraic Geometry · Mathematics 2015-03-19 Daniel Duarte

We use the equivariant cohomology ring of the permutohedral variety to study matroids and their invariants. Investigating the pushforward of matroid Chern classes defined by A. Berget, C. Eur, H. Spink and D. Tseng to the product space…

Algebraic Geometry · Mathematics 2025-09-25 Mario Bauer , Matěj Doležálek , Magdaléna Mišinová , Semen Słobodianiuk , Julian Weigert

Our main result is a combinatorial characterization of when a horospherical variety has (at worst) quotient singularities. Using this characterization, we show that every quasiprojective horospherical variety with quotient singularities is…

Algebraic Geometry · Mathematics 2026-03-31 Sean Monahan

Curve singularities are classical objects of study in algebraic geometry. The key player in their combinatorial structure is the {\it value semigroup}, or its compactification, the {\it value semiring}. One natural problem is to explicitly…

Algebraic Geometry · Mathematics 2024-03-26 Ethan Cotterill , Cristhian Garay López

We study the subvariety of singular sections, the discriminant, of a base point free linear system $|L|$ on a smooth toric variety $X$. On one hand we describe pairs $(X,L)$ for which the discriminant is of low dimension. Precisely, we…

Algebraic Geometry · Mathematics 2021-06-09 Roberto Muñoz , Álvaro Nolla