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We introduce a definition of ``equivariant quasisymmetry'' for polynomials in two sets of variables. Using this definition we define quasisymmetric generalizations of the theory of double Schur and double Schubert polynomials that we call…

Combinatorics · Mathematics 2025-04-22 Nantel Bergeron , Lucas Gagnon , Philippe Nadeau , Hunter Spink , Vasu Tewari

We obtain a presentation by generators and relations for generalized Schur algebras and their quantizations. This extends earlier results obtained in the type A case. The presentation is compatible with Lusztig's modified form of a…

Quantum Algebra · Mathematics 2007-05-23 Stephen Doty

A quasisymmetric function is assigned to every double poset (that is, every finite set endowed with two partial orders) and any weight function on its ground set. This generalizes well-known objects such as monomial and fundamental…

Combinatorics · Mathematics 2026-04-14 Darij Grinberg

We propose an extension of the theory of parity sheaves, which allows for non-locally constant sheaves along strata. Our definition is tailored for proving the existence of (proper, quasihereditary, etc) stratifications of…

Representation Theory · Mathematics 2025-10-07 Ruslan Maksimau , Alexandre Minets

Using the combinatorics of $\alpha$-unimodal sets, we establish two new results in the theory of quasisymmetric functions. First, we obtain the expansion of the fundamental basis into quasisymmetric power sums. Secondly, we prove that…

Combinatorics · Mathematics 2023-11-14 Per Alexandersson , Robin Sulzgruber

We define and study a new class of bialgebras, which generalize certain Turner double algebras related to generic blocks of symmetric groups. Bases and generators of these algebras are given. We investigate when the algebras are symmetric,…

Representation Theory · Mathematics 2018-10-09 Alexander Kleshchev , Robert Muth

We obtain Schur-Weyl dualities in which the algebras, acting on both sides, are semigroup algebras of various symmetric inverse semigroups and their deformations.

Representation Theory · Mathematics 2010-04-02 Ganna Kudryavtseva , Volodymyr Mazorchuk

The involution Stanley symmetric functions $\hat{F}_y$ are the stable limits of the analogues of Schubert polynomials for the orbits of the orthogonal group in the flag variety. These symmetric functions are also generating functions for…

Combinatorics · Mathematics 2017-11-10 Zachary Hamaker , Eric Marberg , Brendan Pawlowski

I continue the investigation of a q-analogue of the convolution on the line started in a joint work with Koornwinder and based on a formal definition due to Kempf and Majid. Two different ways of approximating functions by means of the…

Classical Analysis and ODEs · Mathematics 2016-09-07 Giovanna Carnovale

In this paper we classify all Schur functions and skew Schur functions that are multiplicity free when expanded in the basis of fundamental quasisymmetric functions, termed F-multiplicity free. Combinatorially, this is equivalent to…

Combinatorics · Mathematics 2014-01-30 Christine Bessenrodt , Stephanie van Willigenburg

We establish explicit isomorphisms of two seemingly-different algebras, and their Schur algebras, arising from the centralizers of two different type B Weyl group actions in Schur-like dualities. We provide a presentation of the geometric…

Representation Theory · Mathematics 2020-04-10 Yiqiang Li , Jieru Zhu

We introduce dual Hopf algebras which simultaneously combine the concepts of the k-Schur function theory with the quasi-symmetric Schur function theory. We construct dual basis of these Hopf algebras with remarkable properties.

Combinatorics · Mathematics 2012-05-11 Chris Berg , Luis Serrano

The quasisymmetric generating function of the set of permutations whose inverses have a fixed descent set is known to be symmetric and Schur-positive. The corresponding representation of the symmetric group is called the descent…

Combinatorics · Mathematics 2023-09-26 Vassilis Dionyssis Moustakas

We characterize the Sheffer sequences by a single convolution identity $$ F^{(y)} p_{n}(x) = \sum _{k=0}^{n}\ p_{k}(x)\ p_{n-k}(y)$$ where $F^{(y)}$ is a shift-invariant operator. We then study a generalization of the notion of Sheffer…

Combinatorics · Mathematics 2016-09-06 Alessandro Di Bucchianico , Daniel E. Loeb

Polynomial representations of general linear groups and modules over Schur algebras are compared. We work over an arbitrary commutative ring and show that Schur-Weyl duality is the key for an equivalence between both categories.

Representation Theory · Mathematics 2013-11-05 Henning Krause

We derive several identities involving Ikeda and Naruse's $K$-theoretic Schur $P$- and $Q$-functions. Our main result is a formula conjectured by Lewis and the second author which expands each $K$-theoretic Schur $Q$-function in terms of…

Combinatorics · Mathematics 2024-02-01 Yu-Cheng Chiu , Eric Marberg

Let A_k denote the twisted group algebra of the symmetric group S_k, whose representations correspond to the nonlinear projective representations of S_k. We establish a duality relation between A_k and a Lie superalgebra q(n), sometimes…

Representation Theory · Mathematics 2007-05-23 Manabu Yamaguchi

A graph is Schur-positive if its chromatic symmetric function expands nonnegatively in the Schur basis. All claw-free graphs are conjectured to be Schur-positive. We introduce a combinatorial object corresponding to a graph G, called a…

Combinatorics · Mathematics 2024-12-24 Ethan Shelburne , Stephanie van Willigenburg

To every labeled poset (P,\omega), one can associate a quasisymmetric generating function for its (P,\omega)-partitions. We ask: when do two labeled posets have the same generating function? Since the special case corresponding to skew…

Combinatorics · Mathematics 2014-08-13 Peter R. W. McNamara , Ryan E. Ward

Characterizing sets of permutations whose associated quasisymmetric function is symmetric and Schur-positive is a long-standing problem in algebraic combinatorics. In this paper we present a general method to construct Schur-positive sets…

Combinatorics · Mathematics 2016-11-01 Sergi Elizalde , Yuval Roichman