Let s in S_n be a product of disjoint cycles of the same length, C the conjugacy class of s and rho an irreducible representation of the isotropy group of s. We prove that either the Nichols algebra B(C, rho) is infinite-dimensional, or the braiding of the Yetter-Drinfeld module is negative.
@article{arxiv.math/0608701,
title = {On pointed Hopf algebras associated to unmixed conjugacy classes in S_n},
author = {Nicol'as Andruskiewitsch and Fernando Fantino},
journal= {arXiv preprint arXiv:math/0608701},
year = {2009}
}