Positivity of affine charge

Abstract

The branching of k − 1-Schur functions into k-Schur functions was given by Lapointe, Lam, Morse and Shimozono as chains in a poset on k-shapes. The k-Schur functions are the parameterless case of a more general family of symmetric functions over Q(t), conjectured to satisfy a k-branching formula given by weights on the k-shape poset. A concept of a (co)charge on a k-tableau was defined by Lapointe and Pinto. Although it is not manifestly positive, they prove it is compatible with the k-shape poset for standard k-tableau and the positivity follows. Morse introduced a manifestly positive notion of affine (co)charge on k-tableaux and conjectured that it matches the statistic of Lapointe-Pinto. Here we prove her conjecture and the positivity of k-(co)charge for semi-standard tableaux follows.