Metaplectic representations of Hecke algebras, Weyl group actions, and associated polynomials

TL;DR

This paper develops a uniform construction of metaplectic representations for Hecke algebras, extending to double affine Hecke algebras, and introduces new metaplectic polynomials generalizing nonsymmetric Macdonald polynomials.

Contribution

It provides a conceptual, uniform construction of metaplectic representations and extends these to double affine Hecke algebras, leading to new metaplectic polynomials.

Findings

Explicit formulas for p-parts of Dirichlet series

Construction of metaplectic representation as a quotient of affine Hecke modules

Introduction of metaplectic polynomials generalizing Macdonald polynomials

Abstract

Chinta and Gunnells introduced a rather intricate multi-parameter Weyl group action on rational functions on a torus, which, when the parameters are specialized to certain Gauss sums, describes the functional equations of Weyl group multiple Dirichlet series associated to metaplectic (n-fold) covers of algebraic groups. In subsequent joint work with Puskas, they extended this action to a "metaplectic" representation of the equal parameter affine Hecke algebra, which allowed them to obtain explicit formulas for the p-parts of these Dirichlet series. They have also verified by a computer check the remarkable fact that their formulas continue to define a group action for general (unspecialized) parameters. In the first part of paper we give a conceptual explanation of this fact, by giving a uniform and elementary construction of the "metaplectic" representation for generic Hecke algebras as a suitable quotient of a parabolically induced affine Hecke algebra module, from which the associated Chinta-Gunnells Weyl group action follows through localization. In the second part of the paper we extend the metaplectic representation to the double affine Hecke algebra, which provides a generalization of Cherednik's basic representation. This allows us to introduce a new family of "metaplectic" polynomials, which generalize nonsymmetric Macdonald polynomials. In this paper, we provide the details of the construction of metaplectic polynomials in type A; the general case will be handled in the sequel to this paper.