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We describe a Schubert induction theorem, a tool for analyzing intersections on a Grassmannian over an arbitrary base ring. The key ingredient in the proof is the Geometric Littlewood-Richardson rule, described in a companion paper.…

Algebraic Geometry · Mathematics 2007-05-23 Ravi Vakil

Inspired by the BCFW recurrence for tilings of the amplituhedron, we introduce the general framework of `plabic tangles' that utilizes plabic graphs to define rational maps between products of Grassmannians called `promotions'. The central…

Combinatorics · Mathematics 2026-02-24 Chaim Even-Zohar , Matteo Parisi , Melissa Sherman-Bennett , Ran Tessler , Lauren Williams

We construct geometric realization for non-exceptional mutation-finite cluster algebras by extending the theory of Fomin and Thurston to skew-symmetrizable case. Cluster variables for these algebras are renormalized lambda lengths on…

Combinatorics · Mathematics 2019-10-25 Anna Felikson , Michael Shapiro , Pavel Tumarkin

We apply our previous work on cluster characters for Hom-infinite cluster categories to the theory of cluster algebras. We give a new proof of Conjectures 5.4, 6.13, 7.2, 7.10 and 7.12 of Fomin and Zelevinsky's Cluster algebras IV for…

Representation Theory · Mathematics 2019-02-20 Pierre-Guy Plamondon

We construct the affine version of the Fomin-Kirillov algebra, called the affine FK algebra, to investigate the combinatorics of affine Schubert calculus for type $A$. We introduce Murnaghan-Nakayama elements and Dunkl elements in the…

Combinatorics · Mathematics 2018-06-28 Seung Jin Lee

Based on the Basis theorem of Bruhat--Chevalley [C] and the formula for multiplying Schubert classes obtained in [D\QTR{group}{u}] and programed in [DZ$_{\QTR{group}{1}}$], we introduce a new method computing the Chow rings of flag…

Algebraic Geometry · Mathematics 2014-01-14 Haibao Duan , Xuezhi Zhao

Cominuscule flag varieties generalize Grassmannians to other Lie types. Schubert varieties in cominuscule flag varieties are indexed by posets of roots labeled long/short. These labeled posets generalize Young diagrams. We prove that…

Combinatorics · Mathematics 2024-03-26 Edward Richmond , Mihail Tarigradschi , Weihong Xu

We first prove an identity involving symmetric polynomials. This identity leads us into exploring the geometry of Lagrangian Grassmannians. As an insight applications, we obtain a formula for the integral over the Lagrangian Grassmannian of…

Algebraic Geometry · Mathematics 2020-05-05 Dang Tuan Hiep

In this paper we propose the notion of cluster superalgebras which is a supersymmetric version of the classical cluster algebras introduced by Fomin and Zelevinsky. We show that the symplectic-orthogonal supergroup $SpO(2|1)$ admits a…

Rings and Algebras · Mathematics 2021-02-01 Li Li , James Mixco , B. Ransingh , Ashish K. Srivastava

While the projections of Schubert varieties in a full generalized flag manifold G/B to a partial flag manifold $G/P$ are again Schubert varieties, the projections of Richardson varieties (intersections of Schubert varieties with opposite…

Algebraic Geometry · Mathematics 2011-09-02 Allen Knutson , Thomas Lam , David E Speyer

The cluster automorphism group of a cluster variety was defined by Gekhtman--Shapiro--Vainshtein, and later studied by Lam--Speyer. Braid varieties are interesting affine algebraic varieties indexed by positive braid words. It was proved…

Combinatorics · Mathematics 2026-05-26 Soyeon Kim

Let $\sigma$ be a simple involution of an algebraic semisimple group $G$ and let $H$ be the subgroup of $G$ of points fixed by $\sigma$. If the restricted root system is of type $A$, $C$ or $BC$ and $G$ is simply connected or if the…

Representation Theory · Mathematics 2007-05-23 Rocco Chiriví , Peter Littelmann , Andrea Maffei

Let $\mathbf{P}_{2n+2}$ be the regular polygon with $2n+2$ vertices, and let $\theta$ be the rotation of 180$^\circ$. Fomin and Zelevinsky proved that $\theta$-invariant triangulations of $\mathbf{P}_{2n+2}$ are in bijection with the…

Representation Theory · Mathematics 2026-01-09 Azzurra Ciliberti

Lots of research focuses on the combinatorics behind various bases of cluster algebras. This paper studies the natural basis of a type A cluster algebra, which consists of all cluster monomials. We introduce a new kind of combinatorial…

Combinatorics · Mathematics 2017-06-07 Kyungyong Lee , Li Li , Ba Nguyen

We present a combinatorial and computational commutative algebra methodology for studying singularities of Schubert varieties of flag manifolds. We define the combinatorial notion of *interval pattern avoidance*. For "reasonable" invariants…

Algebraic Geometry · Mathematics 2008-09-13 Alexander Woo , Alexander Yong

We propose a theory of combinatorially explicit Schubert polynomials which represent the Schubert classes in the Borel presentation of the cohomology ring of orthogonal flag varieties. We use these polynomials to describe the arithmetic…

Algebraic Geometry · Mathematics 2013-09-10 Harry Tamvakis

Cluster varieties are geometric objects that have recently found applications in several areas of mathematics and mathematical physics. This thesis studies the geometry of a large class of cluster varieties associated to compact oriented…

Algebraic Geometry · Mathematics 2018-12-27 Dylan G. L. Allegretti

A solution is given to the following problem: how to compute the multiplicity, or more generally the Hilbert function, at a point on a Schubert variety in an orthogonal Grassmannian. Standard monomial theory is applied to translate the…

Combinatorics · Mathematics 2009-04-16 K. N. Raghavan , Shyamashree Upadhyay

We consider tangent cones of Schubert varieties in the complete flag variety, and investigate the problem when the tangent cones of two different Schubert varieties coincide. We give a sufficient condition for such coincidence, and…

Representation Theory · Mathematics 2017-06-12 Dmitry Fuchs , Alexandre Kirillov , Sophie Morier-Genoud , Valentin Ovsienko

Let $\mathbb{X}_{\boldsymbol{p},\boldsymbol{\lambda}}$ be a weighted projective line. We define the quantum cluster algebra of $\mathbb{X}_{\boldsymbol{p},\boldsymbol{\lambda}}$ and realize its specialized version as the subquotient of the…

Representation Theory · Mathematics 2022-07-08 Fan Xu , Fang Yang