86 research outputs found
Richard Stanley through a crystal lens and from a random angle
We review Stanley's seminal work on the number of reduced words of the
longest element of the symmetric group and his Stanley symmetric functions. We
shed new light on this by giving a crystal theoretic interpretation in terms of
decreasing factorizations of permutations. Whereas crystal operators on
tableaux are coplactic operators, the crystal operators on decreasing
factorization intertwine with the Edelman-Greene insertion. We also view this
from a random perspective and study a Markov chain on reduced words of the
longest element in a finite Coxeter group, in particular the symmetric group,
and mention a generalization to a poset setting.Comment: 11 pages; 3 figures; v2 updated references and added discussion on
Coxeter-Knuth grap
The forgotten monoid
We study properties of the forgotten monoid which appeared in work of Lascoux
and Schutzenberger and recently resurfaced in the construction of dual
equivalence graphs by Assaf. In particular, we provide an explicit
characterization of the forgotten classes in terms of inversion numbers and
show that there are n^2-3n+4 forgotten classes in the symmetric group S_n. Each
forgotten class contains a canonical element that can be characterized by
pattern avoidance. We also show that the sum of Gessel's quasi-symmetric
functions over a forgotten class is a 0-1 sum of ribbon-Schur functions.Comment: 13 pages; in version 3 the proof of Proposition 3 is correcte
Schubert Polynomials and Quiver Formulas
The work of Buch and Fulton established a formula for a general kind of
degeneracy locus associated to an oriented quiver of type . The main
ingredients in this formula are Schur determinants and certain integers, the
quiver coefficients, which generalize the classical Littlewood-Richardson
coefficients. Our aim in this paper is to prove a positive combinatorial
formula for the quiver coefficients when the rank conditions defining the
degeneracy locus are given by a permutation. In particular, this gives new
expansions for Fulton's universal Schubert polynomials and the Schubert
polynomials of Lascoux and Sch\"utzenberger.Comment: 13 page
Grothendieck polynomials and the Boson-Fermion correspondence
In this paper we study algebraic and combinatorial properties of Grothendieck
polynomials and their dual polynomials by means of the Boson-Fermion
correspondence. We show that these symmetric functions can be expressed as a
vacuum expectation value of some operator that is written in terms of
free-fermions. By using the free-fermionic expressions, we obtain alternative
proofs of determinantal formulas and Pieri type formulas.Comment: 19 page
Symmetric Functions in Noncommuting Variables
Consider the algebra Q> of formal power series in countably
many noncommuting variables over the rationals. The subalgebra Pi(x_1,x_2,...)
of symmetric functions in noncommuting variables consists of all elements
invariant under permutation of the variables and of bounded degree. We develop
a theory of such functions analogous to the ordinary theory of symmetric
functions. In particular, we define analogs of the monomial, power sum,
elementary, complete homogeneous, and Schur symmetric functions as will as
investigating their properties.Comment: 16 pages, Latex, see related papers at
http://www.math.msu.edu/~sagan, to appear in Transactions of the American
Mathematical Societ
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