[GAP Forum] Schur index question

[David Joyner]

Hello Gap Forum:

Is there a GAP function which computes the
Schur index (over Q) of a representation?
Doesn't seem to be an answer to this in the
Forum archives. The following seems to give a bound
(based on my possibly wrong understanding of a test in
Cor 31 of ch 22 of Berkovich+Zhmud, Chars of finite gps, vol 2):

SchurIndexBound:=function(chi)
local G,H,IrrH,CG,n,i,L,B;
G:=UnderlyingGroup(chi);
L:=[DegreeOfCharacter(chi)];
CG:=ConjugacyClassesSubgroups(G);
n:=Length(CG);
for i in [2..n] do
 H:=Representative(CG[i]);
 IrrH:=Irr(H);
 L:=Union(L,[ScalarProduct(RestrictedClassFunction(chi,H),IrrH[1])]);
od;
B:=Gcd(L);
return(B);
end;

I'm wondering if there is something better out there.

- David Joyner