was proved. We remarked that Tadic’s formula for the characters of Speh representations is
given by the determinant of a matrix, and that the combinatorial identity needed can be
reinterpreted as a curious identity of determinants. We proved this identity, learning later that it
was already known under the name of Lewis Caroll identity [1], [6]. We finish this introduction
by remarking that in the case of GL(m, C), the argument can be reversed, and that it gives a …