2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/165415We present a positivity conjecture for the coefficients of the development of Jack polynomials in terms of power sums. This extends Stanley's ex-conjecture about normalized characters of the symmetric group. We prove this conjecture for partitions having a rectangular shape.24 pages, LaTeXCombinatoricstext