Re: polgalois() bug

[Karim BELABAS <Karim.Belabas@math.u-psud.fr>]

On Sat, 19 Jul 2003, Igor Schein wrote:

> On Fri, Jul 04, 2003 at 09:47:08PM +0200, Karim BELABAS wrote:
> > On Thu, 26 Jun 2003, Igor Schein wrote:
> > > some time ago Galois group notation slightly changed.  It's probably
> > > due to this fact that I am seeing this incorrect result in CVS and
> > > several previous alpha releases:
> > >
> > > ? polgalois(x^6-9*x^4+18*x^2-6)==polgalois(x^6-3*x^4+3)
> > > 1
> >
> > Indeed a typo  [ confusion between group order and degree of defining
> > polynomial ].
>
> Still problems:
>
> ? polgalois(x^6+3)
> [6, -1, 1]
>
> This is wrong, should be [6, -1, 2]

Background info: internally the polgalois routine identifies a group using
the "standard" numbering of transitive subgroups of S_n. The internal output
is actually [n, k], where k is this standard number.

For backward compatibility reasons, this is translated to [ n, s, k' ], where
s is the group signature and k' is an ad hoc identifier (almost always equal
to 1) if the polynomial degree is less than 7 [ see the polgalois() doc and
new_galois_format default for further info ].


The translation was done improperly... Should be OK now.

    Karim.
-- 
Karim Belabas                     Tel: (+33) (0)1 69 15 57 48
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