Structure coefficients for Jack characters: approximate factorization property

Jack characters are a generalization of the characters of the symmetric groups; a generalization that is related to Jack symmetric functions. We investigate the structure coefficients for Jack characters; they are a generalization of the connection coefficients for the symmetric groups. More specifically, we study the cumulants which measure the discrepancy between these structure coefficients and the simplistic structure coefficients related to the disjoint product. We show that Jack characters satisfy approximate factorization property: their cumulants are of very small degree and the character related to a given partition is approximately equal to the product of the characters related to its parts. This result will play a key role in the proof of Gaussianity of fluctuations for a class of random Young diagrams related to the Jack polynomials.