[GAP Forum] subfields of big finite fields

[Inneke Van Gelder]

Dear GAP forum,


I extend GF(2) by a primitive 19-th root of unity as follows:

gap> xi:=PrimitiveRoot(GF(2^18))^((2^18-1)/19);
z
gap> F:=GF(GF(2),MinimalPolynomial(GF(2),xi));
<field of size 262144>

However I am interested in the subfields of this field. But this causes
an error in GAP:

gap> Subfields(F);
Error, no method found! For debugging hints type ?Recovery from
NoMethodFound
Error, no 2nd choice method found for `Subfields' on 1 arguments called
from
<function "HANDLE_METHOD_NOT_FOUND">( <arguments> )
 called from read-eval loop at line 28 of *stdin*
you can 'quit;' to quit to outer loop, or
you can 'return;' to continue

Is there a way to get around this error?


Thanks

Inneke Van Gelder