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Snake graphs appear naturally in the theory of cluster algebras. For cluster algebras from surfaces, each cluster variable is given by a formula which is parametrized by the perfect matchings of a snake graph. In this paper, we identify…

Representation Theory · Mathematics 2012-10-22 Ilke Canakci , Ralf Schiffler

Snakes are analogues of alternating permutations defined for any Coxeter group. We study these objects from the point of view of combinatorial Hopf algebras, such as noncommutative symmetric functions and their generalizations. The main…

Combinatorics · Mathematics 2013-02-12 Matthieu Josuat-Vergès , Jean-Christophe Novelli , Jean-Yves Thibon

In our previous paper we have discussed Poisson properties of cluster algebras of geometric type for the case of a nondegenerate matrix of transition exponents. In this paper we consider the case of a general matrix of transition exponents.…

Quantum Algebra · Mathematics 2007-05-23 Michael Gekhtman , Michael Shapiro , Alek Vainshtein

For any cluster algebra whose underlying combinatorial data can be encoded by a bordered surface with marked points, we construct a geometric realization in terms of suitable decorated Teichmueller space of the surface. On the geometric…

Geometric Topology · Mathematics 2018-09-05 Sergey Fomin , Dylan Thurston

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

Any non-degenerate quadratic form over a Hilbertian field (e.g., a number field) is isomorphic to a scaled trace form. In this work we extend this result to more general fields. In particular, prosolvable and prime-to-p extensions of a…

Number Theory · Mathematics 2007-08-29 Lior Bary-Soroker , Dubi Kelmer

Let $\mathcal{C}$ be a Hom-finite triangulated 2-Calabi-Yau category with a cluster tilting object. Under some constructibility assumptions on $\mathcal{C}$ which are satisfied for instance by cluster categories, by generalized cluster…

Representation Theory · Mathematics 2014-02-26 Yann Palu

We develop a general approach to finding combinatorial models for cluster algebras. The approach is to construct a labeled graph called a framework. When a framework is constructed with certain properties, the result is a model…

Combinatorics · Mathematics 2026-05-28 Nathan Reading , David E Speyer

We give several algebraic bounds for percolation on directed and undirected graphs: proliferation of strongly-connected clusters, proliferation of in- and out-clusters, and the transition associated with the number of giant components.

Mathematical Physics · Physics 2015-03-03 Kathleen E. Hamilton , Leonid P. Pryadko

We give an explicit combinatorial formula for the Schur expansion of Macdonald polynomials indexed by partitions with second part at most two. This gives a uniform formula for both hook and two column partitions. The proof comes as a…

Combinatorics · Mathematics 2017-03-23 Sami Assaf

Graph LP algebras are a generalization of cluster algebras introduced by Lam and Pylyavskyy. We provide a combinatorial proof of positivity for certain cluster variables in these algebras. This proof uses a hypergraph generalization of…

Combinatorics · Mathematics 2023-12-20 Esther Banaian , Sunita Chepuri , Elizabeth Kelley , Sylvester W. Zhang

We describe a framework for encoding cluster combinatorics using categorical methods. We give a definition of an abstract cluster structure, which captures the essence of cluster mutation at a tropical level and show that cluster algebras,…

Rings and Algebras · Mathematics 2025-10-06 Jan E. Grabowski , Sira Gratz

We compare two known methods of extending a complex, unital, commutative normed algebra so as to include solutions to sets of monic polynomials over the original algebra. (One of these is a generalisation of a construction from the thesis…

Functional Analysis · Mathematics 2007-05-23 Thomas Dawson

Taking a Feynman categorical perspective, several key aspects of the geometry of surfaces are deduced from combinatorial constructions with graphs. This provides a direct route from combinatorics of graphs to string topology operations via…

Algebraic Topology · Mathematics 2022-01-26 Clemens Berger , Ralph M. Kaufmann

Coupled-cluster theory is a powerful tool for first-principles calculations of atomic nuclei, enabling accurate predictions of nuclear observables across the Segr\`e chart. While coupled-cluster computations are especially efficient at…

Nuclear Theory · Physics 2026-04-08 F. Marino , F. Bonaiti , P. Demol , S. Bacca , T. Duguet , G. Hagen , G. R. Jansen , T. Papenbrock , A. Tichai

In this paper we extend recent results of Fiorini et al. on the extension complexity of the cut polytope and related polyhedra. We first describe a lifting argument to show exponential extension complexity for a number of NP-complete…

Combinatorics · Mathematics 2013-04-30 David Avis , Hans Raj Tiwary

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

We generalise the expansion formulae of Musiker, Schiffler and Williams, obtained for cluster algebras from orientable surfaces, to a larger class of coefficients which we call principal laminations. In doing so, for any quasi-cluster…

Combinatorics · Mathematics 2020-01-01 Jon Wilson

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

We study Newton polytopes of cluster variables in type A_n cluster algebras, whose cluster and coefficient variables are indexed by the diagonals and boundary segments of a polygon. Our main results include an explicit description of the…

Combinatorics · Mathematics 2013-10-03 Adam Kalman