[sage-devel] Re: Number fields without generators

2011-08-21 Thread Rob Beezer
On Aug 20, 12:32 pm, William Stein  wrote:
> Number fields defined by polynomials that are not monic *and* integral
> are not supported by PARI.

OK, thanks for the explanation.

> It would probably be a 2-3 day project for somebody to make Sage fully
> support fields

Hmm, I don't think I am that somebody.  ;-)

Thanks, William and John, for the help.  I should have enough now to
at least spruce up the eigen-stuff code appropriately, and insert some
doctests that will fail when that somebody gets that project
implemented.

Rob

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Re: [sage-devel] Re: Number fields without generators

2011-08-20 Thread John Cremona
Also Rob, the real name for the field is M._NumberField_relative__gens
(or similar).

John

On Sat, Aug 20, 2011 at 8:32 PM, William Stein  wrote:
> On Sat, Aug 20, 2011 at 10:58 AM, Rob Beezer  wrote:
>> Thanks for the sleuthing and ideas, John.  Yes, I should have used a
>> monic polynomial in my example since the original problem I have is
>> with factors of a characteristic polynomial (and get similar
>> behavior).
>>
>> I also get
>>
>> sage: M._gens is None
>> True
>>
>> The eigenspace code (and probably eigenvalues, too) assume the root
>> field has just one generator, so there is more to do there perhaps.
>>
>> Is that indicative of anything?  I'll dig deeper and see if I can get
>> to the bottom of this.  Maybe at Bug Days 32.  ;-)
>
> Number fields defined by polynomials that are not monic *and* integral
> are not supported by PARI.
> Trying to define them in Sage right now should just give a big error
> on creation, but currently doesn't.
> It would probably be a 2-3 day project for somebody to make Sage fully
> support fields defined by arbitrary
> polynomials though, by secretely using the function
>
>    sage.schemes.elliptic_curves.heegner.make_monic
>
> This project would save people from a lot of headaches, and *has* to
> happen.  It just a matter of time until somebody does it.
>
>  -- William
>
>
>
>>
>> Rob
>>
>> --
>> To post to this group, send an email to sage-devel@googlegroups.com
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>> http://groups.google.com/group/sage-devel
>> URL: http://www.sagemath.org
>>
>
>
>
> --
> William Stein
> Professor of Mathematics
> University of Washington
> http://wstein.org
>
> --
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>

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Re: [sage-devel] Re: Number fields without generators

2011-08-20 Thread William Stein
On Sat, Aug 20, 2011 at 10:58 AM, Rob Beezer  wrote:
> Thanks for the sleuthing and ideas, John.  Yes, I should have used a
> monic polynomial in my example since the original problem I have is
> with factors of a characteristic polynomial (and get similar
> behavior).
>
> I also get
>
> sage: M._gens is None
> True
>
> The eigenspace code (and probably eigenvalues, too) assume the root
> field has just one generator, so there is more to do there perhaps.
>
> Is that indicative of anything?  I'll dig deeper and see if I can get
> to the bottom of this.  Maybe at Bug Days 32.  ;-)

Number fields defined by polynomials that are not monic *and* integral
are not supported by PARI.
Trying to define them in Sage right now should just give a big error
on creation, but currently doesn't.
It would probably be a 2-3 day project for somebody to make Sage fully
support fields defined by arbitrary
polynomials though, by secretely using the function

sage.schemes.elliptic_curves.heegner.make_monic

This project would save people from a lot of headaches, and *has* to
happen.  It just a matter of time until somebody does it.

 -- William



>
> Rob
>
> --
> To post to this group, send an email to sage-devel@googlegroups.com
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> sage-devel+unsubscr...@googlegroups.com
> For more options, visit this group at 
> http://groups.google.com/group/sage-devel
> URL: http://www.sagemath.org
>



-- 
William Stein
Professor of Mathematics
University of Washington
http://wstein.org

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[sage-devel] Re: Number fields without generators

2011-08-20 Thread Rob Beezer
Thanks for the sleuthing and ideas, John.  Yes, I should have used a
monic polynomial in my example since the original problem I have is
with factors of a characteristic polynomial (and get similar
behavior).

I also get

sage: M._gens is None
True

The eigenspace code (and probably eigenvalues, too) assume the root
field has just one generator, so there is more to do there perhaps.

Is that indicative of anything?  I'll dig deeper and see if I can get
to the bottom of this.  Maybe at Bug Days 32.  ;-)

Rob

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