Expanding the quasisymmetric Macdonald polynomials in the fundamental basis

Abstract

The quasisymmetic Macdonald polynomials $G_{\gamma}(X; q, t)$ were recently introduced by the first and second authors with Haglund, Mason, and Williams in [3] to refine the symmetric Macdonald polynomials $P_{\lambda}(X; q, t)$ with the property that $G_{\gamma}(X; 0, 0)$ equals $QS_{\gamma}(X)$, the quasisymmetric Schur polynomial of [9]. We derive an expansion for $G_{\gamma}(X; q, t)$ in the fundamental basis of quasisymmetric functions.