Dear Alexander and Forum, If the cyclotomic number is the square of a cyclotomic number, is there an easy way to find it? The number I need are the eigenvalues of the matrix of the unitarized inner product of an irreducible representation of a finite group (see the comment of Paul Garett here: http://math.stackexchange.com/q/1107941/84284). This matrix is positive, I guess its eigenvalues are always cyclotomic (true for the examples I've looked, but I don't know in general), and I hope they are square of cyclotomic. Thanks to these square roots I can compute the unitary matrices for the irreducible representation. Remark: a function on GAP computing the unitary irreducible representations seems very natural, so if there is not such a function, this should means that there are problems for computing them in general with GAP, isn't it? Best regards,Sebastien Palcoux
Le Mardi 20 janvier 2015 3h13, Alexander Hulpke <hul...@fastmail.fm> a écrit : Dear Forum, > On Jan 19, 2015, at 1/19/15 2:18, Palcoux Sebastien > <sebastienpalc...@yahoo.fr> wrote: > > Hi, > Is it possible to extend the function Sqrt on the cyclotomic numbers? How would you represent this root? In general the square root of a cylotomic is not cyclotomic again. (You could form a formal AlgebraicExtension, but then you lose the irrational cyclotomics for operations.) Regards, Alexander Hulpke _______________________________________________ Forum mailing list Forum@mail.gap-system.org http://mail.gap-system.org/mailman/listinfo/forum