Combinatorics of ribbon tableaux

Abstract

This thesis begins with the study of a class of symmetric functions ... Which are generating functions for ribbon tableaux (hereon called ribbon functions), first defined by Lascoux, Leclerc and Thibon. Following work of Fomin and Greene, I introduce a set of operators called ribbon Schur operators on the space of partitions. I develop the theory of ribbon functions using these operators in an elementary manner. In particular, I deduce their symmetry and recover a theorem of Kashiwara, Miwa and Stern concerning the Fock space F of the quantum affine algebras ... Using these results, I study the functions ... in analogy with Schur functions, giving: * a Pieri and dual-Pieri formula for ribbon functions, * a ribbon Murnaghan-Nakayama formula, * ribbon Cauchy and dual Cauchy identities, * and a C-algebra isomorphism ... The study of the functions ... will be connected to the Fock space representation F of ...via a linear map [Iota]: F ... which sends the standard basis of F to the ribbon functions. Kashiwara, Miwa and Stern [29] have shown that a copy of the Heisenberg algebra H acts on F commuting with the action of ... Identifying the Fock Space of H with the ring of symmetric functions A(q) I will show that · is in fact a map of H-modules with remarkable properties. In the second part of the thesis, I give a combinatorial generalisation of the classical Boson-Fermion correspondence and explain how the map [phi] is an example of this more general phenomena. I show how certain properties of many families of symmetric functions arise naturally from representations of Heisenberg algebras. The main properties I consider are a tableaux-like definition, a Pieri-style rule and a Cauchy-style identity.

(cont.) Families of symmetric functions which can be viewed in this manner include Schur functions, Hall- Littlewood functions, Macdonald polynomials and the ribbon functions. Using work of Kashiwara, Miwa, Petersen and Yung, I define generalised ribbon functions for certain affine root systems 1 of classical type. I prove a theorem relating these generalised ribbon functions to a speculative global basis of level 1 q-deformed Fock spaces.