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This thesis studies skein relations in cluster algebras arising from punctured surfaces. We introduce skein-type identities expressing cluster variables associated with incompatible curves on a surface in terms of cluster variables…

Combinatorics · Mathematics 2026-01-01 Michael Tsironis

We outline a novel clustering scheme for simplicial complexes that produces clusters of simplices in a way that is sensitive to the homology of the complex. The method is inspired by, and can be seen as a higher-dimensional version of,…

Machine Learning · Computer Science 2020-06-23 Stefania Ebli , Gard Spreemann

As a model problem for clustering, we consider the densest k-disjoint-clique problem of partitioning a weighted complete graph into k disjoint subgraphs such that the sum of the densities of these subgraphs is maximized. We establish that…

Optimization and Control · Mathematics 2019-02-18 Aleksis Pirinen , Brendan Ames

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

We consider the Ptolemy cluster algebras, which are cluster algebras of finite type $A$ (with non-trivial coefficients) that have been described by Fomin and Zelevinsky using triangulations of a regular polygon. Given any seed $\zS$ in a…

Representation Theory · Mathematics 2007-05-23 Ralf Schiffler

We study the cluster algebra of the kinematic configuration space $Conf_n(\mathbb{P}^3)$ of a n-particle scattering amplitude restricted to the special 2D kinematics. We found that the n-points two loop MHV remainder function found in…

High Energy Physics - Theory · Physics 2014-01-29 Marcus A. C. Torres

Let $G$ be a simply connected simple algebraic group over $\mathbb{C}$ of type $B_r$, $B$ and $B_-$ be its two opposite Borel subgroups, and $W$ be the associated Weyl group. For $u$, $v\in W$, it is known that the coordinate ring ${\mathbb…

Quantum Algebra · Mathematics 2017-04-12 Yuki Kanakubo

We give a module-theoretic interpretation of Schiffler's expansion formula which is defined combinatorially in terms of complete (T,r)-paths in order to get the expansion of the cluster variables in the cluster algebra of a marked surface…

Representation Theory · Mathematics 2011-05-31 Thomas Brüstle , Jie Zhang

We introduce a class of non-commutative algebras that carry a non-commutative (geometric) cluster structure which are generated by identical copies of generalized Weyl algebras. Equivalent conditions for the finiteness of the set of the…

Representation Theory · Mathematics 2016-05-13 Ibrahim Saleh

We generalize the construction of the bracelet and bangle bases defined by Musiker, Schiffler and Williams, and the band basis defined by D. Thurston to cluster algebras arising from orbifolds. We prove that the bracelet bases are positive,…

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

Given one of an infinite class of supersymmetric quiver gauge theories, string theorists can associate a corresponding toric variety (which is a Calabi-Yau 3-fold) as well as an associated combinatorial model known as a brane tiling. In…

Combinatorics · Mathematics 2017-08-07 Tri Lai , Gregg Musiker

In this paper we give a direct proof of the positivity conjecture for adapted quantum cluster variables. Moreover, our process allows one to explicitly compute formulas for all adapted cluster monomials and certain ordered products of…

Quantum Algebra · Mathematics 2011-04-06 Dylan Rupel

We develop an elementary formula for certain non-trivial elements of upper cluster algebras. These elements have positive coefficients. We show that when the cluster algebra is acyclic these elements form a basis. Using this formula, we…

Rings and Algebras · Mathematics 2015-06-29 Kyungyong Lee , Li Li , Matthew R. Mills

Clustering, like covariate selection for classification, is an important step to compress and interpret the data. However, clustering of covariates is often performed independently of the classification step, which can lead to undesirable…

Computation · Statistics 2020-04-08 Daniel Andrade , Kenji Fukumizu , Yuzuru Okajima

$k$-means and $k$-median clustering are powerful unsupervised machine learning techniques. However, due to complicated dependences on all the features, it is challenging to interpret the resulting cluster assignments. Moshkovitz, Dasgupta,…

Data Structures and Algorithms · Computer Science 2021-12-17 Sayan Bandyapadhyay , Fedor V. Fomin , Petr A. Golovach , William Lochet , Nidhi Purohit , Kirill Simonov

We provide a module-theoretic interpretation of the expansion formula given by Huang (2022), which defines a map on perfect matchings to compute the expansion of quantum cluster variables in quantum cluster algebras arising from unpunctured…

Representation Theory · Mathematics 2026-04-07 Yutong Yu

We give a uniform geometric realization for the cluster algebra of an arbitrary finite type with principal coefficients at an arbitrary acyclic seed. This algebra is realized as the coordinate ring of a certain reduced double Bruhat cell in…

Rings and Algebras · Mathematics 2008-05-19 Shih-Wei Yang , Andrei Zelevinsky

This paper studies clustering algorithms for dynamically evolving graphs $\{G_t\}$, in which new edges (and potential new vertices) are added into a graph, and the underlying cluster structure of the graph can gradually change. The paper…

Data Structures and Algorithms · Computer Science 2024-06-06 Steinar Laenen , He Sun

In this paper we study the derived equivalences between surface algebras, introduced by David-Roesler and Schiffler. Each surface algebra arises from a cut of an ideal triangulation of an unpunctured marked Riemann surface with boundary. A…

Representation Theory · Mathematics 2016-03-28 Claire Amiot , Yvonne Grimeland

We obtain a multiplication formula for cluster characters on (stably) 2-Calabi-Yau (Frobenius or) triangulated categories. This formula generalizes those known for arbitrary pairs of objects and for Auslander-Reiten triangles. As an…

Representation Theory · Mathematics 2023-01-11 Bernhard Keller , Pierre-Guy Plamondon , Fan Qin