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The famous theorem of Conway and Coxeter on frieze patterns gave a geometric interpretation to integral friezes via triangulations of polygons. In this article, we review this result and show some of the development it has led to. The last…

Combinatorics · Mathematics 2021-01-15 Karin Baur

We give a complete classification of torsion pairs in the cluster categories associated to tubes of finite rank. The classification is in terms of combinatorial objects called Ptolemy diagrams which already appeared in our earlier work on…

Representation Theory · Mathematics 2014-06-06 Thorsten Holm , Peter Jorgensen , Martin Rubey

A frieze is an array of numbers obeying the unimodular rule. Coxeter showed that a frieze with integer entries corresponds to a triangulation. Recently, Holm and J{\o}rgenson introduced friezes of type $\Lambda_p$ which correspond to…

Combinatorics · Mathematics 2020-03-17 Lukas Andritsch

Motivated by the definition of super-Teichm\"uller spaces, and Penner-Zeitlin's recent extension of this definition to decorated super-Teichm\"uller space, as examples of super Riemann surfaces, we use the super Ptolemy relations to obtain…

Combinatorics · Mathematics 2021-09-02 Gregg Musiker , Nicholas Ovenhouse , Sylvester W. Zhang

In this article, we establish a relation between the values of a frieze of type D-tile and some values of an SL2-tiling t associated with a particular quiver of type A-tilde . This relation allows us to compute, independently of each other,…

Commutative Algebra · Mathematics 2014-05-07 Magnani Kodjo Essonana

This article, based on joint work with Gabriel Carroll, Andy Itsara, Ian Le, Gregg Musiker, Gregory Price, Dylan Thurston, and Rui Viana, presents a combinatorial model based on perfect matchings that explains the symmetries of the…

Combinatorics · Mathematics 2020-05-29 James Propp

We present a combinatorial model for cluster algebras of type $D_n$ in terms of centrally symmetric pseudotriangulations of a regular $2n$-gon with a small disk in the centre. This model provides convenient and uniform interpretations for…

Commutative Algebra · Mathematics 2023-11-14 Cesar Ceballos , Vincent Pilaud

A frieze on a polygon is a map from the diagonals of the polygon to an integral domain which respects the Ptolemy relation. Conway and Coxeter previously studied positive friezes over $\mathbb{Z}$ and showed that they are in bijection with…

Combinatorics · Mathematics 2025-07-30 Esther Banaian , Libby Farrell , Amy Tao , Kayla Wright , Joy Zhichun Zhang

Finite frieze patterns with entries in $\mathbb{Z}[\lambda_{p_1},\ldots,\lambda_{p_s}]$ where $\{p_1,\ldots,p_s\} \subseteq \mathbb{Z}_{\geq 3}$ and $\lambda_p = 2 \cos(\pi/p)$ were shown to have a connection to dissected polygons by Holm…

Combinatorics · Mathematics 2021-06-15 Esther Banaian , Jiuqi Chen

We give a geometric realization of cluster categories of type $D_n$ using a polygon with $n$ vertices and one puncture in its center as a model. In this realization, the indecomposable objects of the cluster category correspond to certain…

Representation Theory · Mathematics 2007-05-23 Ralf Schiffler

Let Q be a quiver without loops and 2-cycles, let A(Q) be the corresponding cluster algebra and let x be a cluster. We introduce a new class of integer vectors which we call frieze vectors relative to x. These frieze vectors are defined as…

Combinatorics · Mathematics 2020-11-03 Emily Gunawan , Ralf Schiffler

For each Dynkin diagram $D$, we define a ''cluster configuration space'' ${\mathcal{M}}_D$ and a partial compactification ${\widetilde {\mathcal{M}}}_D$. For $D = A_{n-3}$, we have ${\mathcal{M}}_{A_{n-3}} = {\mathcal{M}}_{0,n}$, the…

Algebraic Geometry · Mathematics 2021-10-19 Nima Arkani-Hamed , Song He , Thomas Lam

We introduce some new Frobenius subcategories of the module category of a preprojective algebra of Dynkin type, and we show that they have a cluster structure in the sense of Buan-Iyama-Reiten-Scott. These categorical cluster structures…

Representation Theory · Mathematics 2015-01-06 Bernard Leclerc

We investigate skein relations in cluster algebras from punctured surfaces, extending the work of \c{C}anak\c{c}i-Schiffler and Musiker-Williams on unpunctured surfaces. Using a combinatorial expansion formula by…

Combinatorics · Mathematics 2024-11-21 Esther Banaian , Wonwoo Kang , Elizabeth Kelley

In this survey article we explain the intricate links between Conway-Coxeter friezes and cluster combinatorics. More precisely, we provide a formula, relying solely on the shape of the frieze, describing how each individual entry in the…

Rings and Algebras · Mathematics 2018-06-19 Karin Baur , Eleonore Faber , Sira Gratz , Khrystyna Serhiyenko , Gordana Todorov

In this article we consider tame $ SL_3 $-friezes that arise by specializing a cluster of Pl\"ucker variables in the coordinate ring of the Grassmannian $ \mathscr{G}(3,n) $ to $ 1 $. We show how to calculate arbitrary entries of such…

Combinatorics · Mathematics 2024-04-16 Lucas Surmann

We continue our investigation on denominator conjecture of Fomin and Zelevinsky for cluster algebras via geometric models initialed in \cite{FG22}. In this paper, we confirm the denominator conjecture for cluster algebras of finite type.…

Representation Theory · Mathematics 2024-11-19 Changjian Fu , Shengfei Geng

We study super cluster algebra structure arising in examples provided by super Pl\"{u}cker and super Ptolemy relations. We develop the super cluster structure of the super Grassmannians $\Gr_{2|0}(n|1)$ for arbitrary $n$, which was…

Mathematical Physics · Physics 2025-06-23 Ekaterina Shemyakova

We study cluster algebras with principal and arbitrary coefficient systems that are associated to unpunctured surfaces. We give a direct formula for the Laurent polynomial expansion of cluster variables in these cluster algebras in terms of…

Representation Theory · Mathematics 2008-09-18 Ralf Schiffler

We study cluster algebras that are associated to unpunctured surfaces with coefficients arising from boundary arcs. We give a direct formula for the Laurent polynomial expansion of cluster variables in these cluster algebras in terms of…

Representation Theory · Mathematics 2008-02-27 Ralf Schiffler , Hugh Thomas