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We show that the coordinate ring of an open positroid variety coincides with the cluster algebra associated to a Postnikov diagram. This confirms conjectures of Postnikov, Muller--Speyer, and Leclerc, and generalizes results of Scott and…

Combinatorics · Mathematics 2021-06-15 Pavel Galashin , Thomas Lam

We give an explicit combinatorial description of cluster structures in Schubert varieties of the Grassmannian in terms of (target labelings of) Postnikov's plabic graphs. This description is a natural generalization of the description given…

Combinatorics · Mathematics 2018-11-08 Khrystyna Serhiyenko , Melissa Sherman-Bennett , Lauren Williams

The Grassmannian is a disjoint union of open positroid varieties $P_v$, certain smooth irreducible subvarieties whose definition is motivated by total positivity. The coordinate ring of $P_v$ is a cluster algebra, and each reduced plabic…

Combinatorics · Mathematics 2022-01-07 Chris Fraser , Melissa Sherman-Bennett

The purpose of this note is to connect two maps related to certain graphs embedded in the disc. The first is Postnikov's boundary measurement map, which combines partition functions of matchings in the graph into a map from an algebraic…

Combinatorics · Mathematics 2017-11-22 Greg Muller , David E Speyer

We introduce quasi-homomorphisms of cluster algebras, a flexible notion of a map between cluster algebras of the same type (but with different coefficients). The definition is given in terms of seed orbits, the smallest equivalence classes…

Rings and Algebras · Mathematics 2016-01-18 Chris Fraser

We introduce a framework for $\mathbb{Z}$-gradings on cluster algebras (and their quantum analogues) that are compatible with mutation. To do this, one chooses the degrees of the (quantum) cluster variables in an initial seed subject to a…

Quantum Algebra · Mathematics 2014-12-03 Jan E. Grabowski , Stéphane Launois

In this article we explain how the coordinate ring of each (open) Schubert variety in the Grassmannian can be identified with a cluster algebra, whose combinatorial structure is encoded using (target labelings of) Postnikov's plabic graphs.…

Combinatorics · Mathematics 2019-08-07 K. Serhiyenko , M. Sherman-Bennett , L. Williams

With any non necessarily orientable unpunctured marked surface (S,M) we associate a commutative algebra, called quasi-cluster algebra, equipped with a distinguished set of generators, called quasi-cluster variables, in bijection with the…

Rings and Algebras · Mathematics 2015-02-17 Grégoire Dupont , Frédéric Palesi

Considered as commutative algebras, cluster algebras can be very unpleasant objects. However, the first author introduced a condition known as "local acyclicity" which implies that cluster algebras behave reasonably. One of the earliest and…

Combinatorics · Mathematics 2015-06-23 Greg Muller , David E. Speyer

Plabic graphs are intimately connected to the positroid stratification of the positive Grassmannian. The duals to these graphs are quivers, and it is possible to associate to them cluster algebras. For the top-cell graph of $Gr_{+}(k,n)$,…

High Energy Physics - Theory · Physics 2015-06-22 Miguel F. Paulos , Burkhard U. W. Schwab

We study the homogeneous coordinate rings of partial flag varieties and Grassmannians in their Pl\"ucker embeddings and exhibit an embedding of the former into the latter. Both rings are cluster algebras and the embedding respects the…

Algebraic Geometry · Mathematics 2025-04-29 Lara Bossinger , Jian-Rong Li

We study the relation between the cluster automorphisms and the quasi-automorphisms of a cluster algebra $\mathcal{A}$. We proof that under some mild condition, satisfied for example by every skew-symmetric cluster algebra, the…

Rings and Algebras · Mathematics 2018-08-08 Wen Chang , Ralf Schiffler

We construct an explicit isomorphism between an open subset in the open positroid variety $\Pi_{k,n}^{\circ}$ in the Grassmannian $\mathrm{Gr}(k,n)$ and the product of two open positroid varieties $\Pi_{k,n-a+1}^{\circ}\times…

Algebraic Geometry · Mathematics 2024-05-27 Eugene Gorsky , Tonie Scroggin

In this article we use the cluster structure on the Grassmannian and the combinatorics of plabic graphs to exhibit a new aspect of mirror symmetry for Grassmannians in terms of polytopes. For our $A$-model, we consider the Grassmannian…

Algebraic Geometry · Mathematics 2017-12-06 Konstanze Rietsch , Lauren Williams

Holm and Jorgensen have shown the existence of a cluster structure on a certain category $D$ that shares many properties with finite type $A$ cluster categories and that can be fruitfully considered as an infinite analogue of these. In this…

Representation Theory · Mathematics 2014-12-03 Jan E. Grabowski , Sira Gratz

In this paper, we study quasi-homomorphisms of quantum cluster algebras, which are quantum analogy of quasi-homomorphisms of cluster algebras introduced by Fraser. For a quantum Grassmannian cluster algebra $\mathbb{C}_q[{\rm Gr}(k,n)]$, we…

Quantum Algebra · Mathematics 2023-09-04 Wen Chang , Min Huang , Jian-Rong Li

We define an action of the extended affine d-strand braid group on the open positroid stratum in the Grassmannian Gr(k,n), for d the greatest common divisor of k and n. The action is by quasi-automorphisms of the cluster structure on the…

Combinatorics · Mathematics 2018-08-17 Chris Fraser

The main goal of this paper is to show that the (multi-homogeneous) coordinate ring of a partial flag variety $\mathbb{C} [G / P_K^{-}]$ admits a cluster algebra structure if $G$ is any simply-connected semisimple complex algebraic group.…

Rings and Algebras · Mathematics 2022-08-30 Fayadh Kadhem

Affine cluster varieties are covered up to codimension 2 by open algebraic tori. We put forth a general conjecture (based on earlier conversation between Vivek Shende and the last author) characterizing their deep locus, i.e. the complement…

Algebraic Geometry · Mathematics 2024-03-06 Marco Castronovo , Mikhail Gorsky , José Simental , David E Speyer

We study tropicalisations of quasi-automorphisms of cluster algebras and show that their induced action on the g-vectors can be realized by tropicalising their action on the homogeneous $\hat{y}$ (or $\mathcal{X}$) variables of a chosen…

Representation Theory · Mathematics 2026-03-17 James Drummond , Ömer Gürdoğan , Jian-Rong Li
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