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We introduce toric arrangements, essentially finite families of codimension 1 subtori of a torus or of their cosets, as a periodic generalization of hyperplane arrangements, compute cohomology of the complement of such an arrangement and…

Algebraic Geometry · Mathematics 2007-05-23 C. De Concini , C. Procesi

Let $P$ be the Gelfand--Tsetlin polytope defined by the skew shape $\lambda/\mu$ and weight $w$. In the case corresponding to a standard Young tableau, we completely characterize for which shapes $\lambda/\mu$ the polytope $P$ is integral.…

Combinatorics · Mathematics 2018-11-13 Per Alexandersson

Using Okounkov's $q$-integral representation of Macdonald polynomials we construct an infinite sequence $\Omega_1,\Omega_2,\Omega_3,\dots$ of countable sets linked by transition probabilities from $\Omega_N$ to $\Omega_{N-1}$ for each…

Probability · Mathematics 2021-06-29 Grigori Olshanski

The Hodge algebra structures on the homogeneous coordinate rings of Grassmann varieties provide semi-toric degenerations of these varieties. In this paper we construct these semi-toric degenerations using quasi-valuations and triangulations…

Algebraic Geometry · Mathematics 2018-04-12 Xin Fang , Peter Littelmann

We extend the results on the graph closures of the birational maps between projective spaces and Grassmannians to the case of PBW degenerate flag varieties. The advantage of the PBW degenerate flags (as opposed to their classical analogues)…

Algebraic Geometry · Mathematics 2024-07-11 Evgeny Feigin

We show that a weight variety, which is a quotient of a flag variety by the maximal torus, admits a flat degeneration to a toric variety. In particular, we show that the moduli spaces of spatial polygons degenerate to polarized toric…

Algebraic Geometry · Mathematics 2007-05-23 Philip Foth , Yi Hu

We study the combinatorics of Gr\"obner degenerations of Grassmannians and the Schubert varieties inside them. We provide a family of binomial ideals whose combinatorics is governed by tableaux induced by matching fields in the sense of…

Commutative Algebra · Mathematics 2020-09-15 Oliver Clarke , Fatemeh Mohammadi

We introduce a family of toric algebras defined by maximal chains of a finite distributive lattice. Applying results on stable set polytopes we conclude that every such algebra is normal and Cohen-Macaulay, and give an interpretation of its…

Commutative Algebra · Mathematics 2024-03-13 Oleksandra Gasanova , Lisa Nicklasson

The goal of this paper is to study the link between the topology of the degenerate flag varieties and combinatorics of the Dellac configurations. We define three new classes of algebraic varieties closely related to the degenerate flag…

Combinatorics · Mathematics 2018-08-14 Ange Bigeni , Evgeny Feigin

Using multigraded Castelnuovo-Mumford regularity, we study the equations defining a projective embedding of a variety X. Given globally generated line bundles B_1, ..., B_k on X and integers m_1, ..., m_k, consider the line bundle L :=…

Algebraic Geometry · Mathematics 2010-03-15 Milena Hering , Hal Schenck , Gregory G. Smith

In this paper we use toric geometry to investigate the topology of the totally non-negative part of the Grassmannian (Gr_{kn})_{\geq 0}. This is a cell complex whose cells Delta_G can be parameterized in terms of the combinatorics of…

Algebraic Geometry · Mathematics 2008-10-15 Alexander Postnikov , David Speyer , Lauren Williams

We define toric partial orders, corresponding to regions of graphic toric hyperplane arrangements, just as ordinary partial orders correspond to regions of graphic hyperplane arrangements. Combinatorially, toric posets correspond to finite…

Combinatorics · Mathematics 2012-11-20 Mike Develin , Matthew Macauley , Victor Reiner

Block diagonal matching field has many previous works. In general, a coherent matching field induces a monomial order to Pl\"{u}cker algebra, and block diagonal matching fields are a kind of coherent matching fields. In the present paper,…

Combinatorics · Mathematics 2025-05-02 Akihiro Higashitani , Nobukazu Kowaki

Toric varieties play an important role both in symplectic and complex geometry. In symplectic geometry, the construction of a symplectic toric manifold from a smooth polytope is due to Delzant. In algebraic geometry, there is a more general…

Algebraic Geometry · Mathematics 2018-01-17 Andreas Hochenegger , Frederik Witt

Postnikov gave a parametrization for the totally non-negative Grassmannian using the matroid decomposition and associating a network with \reflectbox{L}-diagrams. Talaska and Williams extend this result to the entire Grassmannian by using…

Combinatorics · Mathematics 2025-12-19 Kartik Singh

We create a framework for studying symmetric chain decompositions of families of finite posets based on the geometry of polytopes. Our framework unifies almost all known results regarding symmetric chain decompositions of the Young posets…

Combinatorics · Mathematics 2017-06-07 Stefan David , Hunter Spink , Marius Tiba

The goal of the paper is to describe new connections between representation theory and algebraic combinatorics on one side, and probability theory on the other side. The central result is a construction, by essentially algebraic tools, of a…

Combinatorics · Mathematics 2024-08-15 Grigori Olshanski

We apply the theory of Seshadri stratifications to embedded toric varieties $X_P\subseteq \mathbb P(V)$ associated with a normal lattice polytope $P$. The approach presented here is purely combinatorial and completely independent of…

Algebraic Geometry · Mathematics 2025-05-06 Rocco Chirivì , Martina Costa Cesari , Xin Fang , Peter Littelmann

In this article we investigate a class of linear error correcting codes in relation with the order polytopes. In particular we consider the order polytopes of tree posets and bipartite posets. We calculate the parameters of the associated…

Combinatorics · Mathematics 2021-07-28 Mahir Bilen Can , Takayuki Hibi

Given a matrix Schubert variety $\overline{X_\pi}$, it can be written as $\overline{X_\pi}=Y_\pi\times \mathbb{C}^q$ (where $q$ is maximal possible). We characterize when $Y_{\pi}$ is toric (with respect to a $(\mathbb{C}^*)^{2n-1}$-action)…

Combinatorics · Mathematics 2015-08-17 Laura Escobar , Karola Meszaros