field = self.base_ring().base_ring() # yeeeeaaaahhh
J = self.__class__(n, field, False)
(_,x,_,_) = J._charpoly_matrix_system()
field = self.base_ring().base_ring() # yeeeeaaaahhh
J = self.__class__(n, field, False)
(_,x,_,_) = J._charpoly_matrix_system()