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We classify compact quantum groups associated to noncrossing partitions coloured with two elements $x$ and $y$ which are their own inverses. Together with the work of P. Tarrago and M. Weber, this completes the classification of all…

Quantum Algebra · Mathematics 2018-06-12 Amaury Freslon

We introduce Coxeter-sortable elements of a Coxeter group W. For finite W, we give bijective proofs that Coxeter-sortable elements are equinumerous with clusters and with noncrossing partitions. We characterize Coxeter-sortable elements in…

Combinatorics · Mathematics 2026-05-13 Nathan Reading

In this paper, we give part-preserving bijections between three fundamental families of objects that serve as natural framework for many problems in enumerative combinatorics. Specifically, we consider compositions, Dyck paths, and…

Combinatorics · Mathematics 2024-05-13 Juan B. Gil , Emma G. Hoover , Jessica A. Shearer

We study positive $m$-divisible non-crossing partitions and their positive Kreweras maps. In classical types, we describe their combinatorial realisations as certain non-crossing set partitions. We also realise these positive Kreweras maps…

Combinatorics · Mathematics 2025-06-19 Christian Krattenthaler , Christian Stump

Motivated by recent work on mixtures of classical and free probabilities, we introduce and study the notion of $\epsilon$-noncrossing partitions. It is shown that the set of such partitions forms a lattice, which interpolates as a poset…

Combinatorics · Mathematics 2018-12-06 Kurusch Ebrahimi-Fard , Frederic Patras , Roland Speicher

This paper generalizes in the affine symmetric group the notion of Coxeter sortable (or c-sortable for short) elements, as well as the classical bijection between c-sortable elements and c-noncrossing partitions defined by Reading in finite…

Combinatorics · Mathematics 2026-05-05 Jad Abou-Yassin

The usual, or type A_n, Tamari lattice is a partial order on T_n^A, the triangulations of an (n+3)-gon. We define a partial order on T_n^B, the set of centrally symmetric triangulations of a (2n+2)-gon. We show that it is a lattice, and…

Combinatorics · Mathematics 2007-05-23 Hugh Thomas

For any finite, real reflection group $W$, we construct a geometric basis for the homology of the corresponding non-crossing partition lattice. We relate this to the basis for the homology of the corresponding intersection lattice…

Combinatorics · Mathematics 2008-07-15 Aisling Kenny

Our basic objects are partitions of finite sets of points into disjoint subsets. We investigate sets of partitions which are closed under taking tensor products, composition and involution, and which contain certain base partitions. These…

Combinatorics · Mathematics 2015-09-04 Pierre Tarrago , Moritz Weber

We present a direct bijection between descending plane partitions with no special parts and permutation matrices. This bijection has the desirable property that the number of parts of the descending plane partition corresponds to the…

Combinatorics · Mathematics 2012-07-26 Jessica Striker

For a finite real reflection group $W$ we use non-crossing partitions of type $W$ to construct finite cell complexes with the homotopy type of the Milnor fiber of the associated $W$-discriminant $\Delta_W$ and that of the Milnor fiber of…

Group Theory · Mathematics 2018-12-19 Thomas Brady , Michael Falk , Colum Watt

We describe a special bijection between the indecomposable summands of two basic $\tau$-tilting modules.

Representation Theory · Mathematics 2025-04-10 Gabriella D'Este , H. Melis Tekin Akcin

Set partitions avoiding $k$-crossing and $k$-nesting have been extensively studied from the aspects of both combinatorics and mathematical biology. By using the generating tree technique, the obstinate kernel method and Zeilberger's…

Combinatorics · Mathematics 2017-07-11 Sherry H. F. Yan

For an exact category having enough projective objects, we establish a bijection between thick subcategories containing the projective objects and thick subcategories of the stable derived category. Using this bijection we classify thick…

Category Theory · Mathematics 2015-01-14 Henning Krause , Greg Stevenson

For stacked simplicial complexes, (special subclasses of such are: trees, triangulations of polygons, stacked polytopes), we give an explicit bijection between partitions of facets (for trees: edges), and partitions of vertices into…

Combinatorics · Mathematics 2024-01-17 Gunnar Fløystad

In this article we give a simple, almost uniform proof that the lattice of noncrossing partitions associated with a well-generated complex reflection group is lexicographically shellable. So far a uniform proof is available only for Coxeter…

Combinatorics · Mathematics 2015-07-03 Henri Mühle

For a fixed integer $k$, we consider the set of noncrossing partitions, where both the block sizes and the difference between adjacent elements in a block is $1\bmod k$. We show that these $k$-indivisible noncrossing partitions can be…

Combinatorics · Mathematics 2021-07-26 Henri Mühle , Philippe Nadeau , Nathan Williams

A separating algebra is, roughly speaking, a subalgebra of the ring of invariants whose elements distinguish between any two orbits that can be distinguished using invariants. In this paper, we introduce a geometric notion of separating…

Commutative Algebra · Mathematics 2016-02-01 Emilie Dufresne

A \emph{set partition} of the set $[n]=\{1,...c,n\}$ is a collection of disjoint blocks $B_1,B_2,...c, B_d$ whose union is $[n]$. We choose the ordering of the blocks so that they satisfy $\min B_1<\min B_2<...b<\min B_d$. We represent such…

Combinatorics · Mathematics 2007-05-23 Vit Jelinek , Toufik Mansour

We define a bijection between triangulations of a convex polygon and $312$-avoiding permutations through the process of "ear-clipping". This bijection is then used to obtain a bijection between polygon dissections and a certain class of…

Combinatorics · Mathematics 2013-11-11 Alon Regev