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Computing Galois group of a polynomial?

asked 2014-09-26 08:41:20 +0200

Alasdair gravatar image

Here's my attempt so far:

x = polygen(QQ, 'x');
K.<z> = NumberField(x^4+x^2+2*x+1)
G = K.galois_group(type='gap')

And now I get several pages of error messages beginning with

verbose 0 (1780:, cardinality) Warning: TransitiveGroups requires the GAP database package. Please install it with ``sage -i database_gap``.

However! - I have installed this:



Anybody got any ideas on where I can go from here?

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It woks for me (with Sage 6.4.beta3 and database_gap-4.7.5), i got : Galois group Transitive group number 3 of degree 4 of the Number Field in z with defining polynomial x^4 + x^2 + 2*x + 1 What is your configuration ?

tmonteil gravatar imagetmonteil ( 2014-09-26 10:28:03 +0200 )edit

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answered 2014-09-26 10:24:03 +0200

install_package() might be slightly broken at the moment, in the course of transition to git. Did you try running sage -i database_gap, as the error message says?

(your example works for me just fine).

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Whenever I try to reinstall database_gap, either with `sage -i database_gap` or with 'install_package('databse_gap') from within Sage, I get an error that it's already installed. I tried also with `install_package('database_gap, force=True)` but that gave a different error: ValueError: There is no package name starting with 'database_gap'. I'll try again later in case there's a network issue.

Alasdair gravatar imageAlasdair ( 2014-09-26 13:30:14 +0200 )edit

`sage -f database_gap` will force a reinstall.

Dima gravatar imageDima ( 2014-09-26 14:19:55 +0200 )edit

if this doesn't work, what is the output of `gap_console()` at your Sage prompt?

Dima gravatar imageDima ( 2014-09-26 14:28:19 +0200 )edit

I reinstalled it (as root) using 'sage -f database_gap' as Dima suggests, and then it works fine if I run Sage as root. However, if I run Sage as an ordinary user, I still receive errors that the GAP database package is not installed. But trying to run 'sage -f database_gap' as an ordinary user gives me the error that I can't write to the /opt/sage-6.2 directory. However, gap_console() from both root and ordinary user gives the same output; that the Components are: trans 1.0, prim 2.1, small* 1.0, id* 1.0. Maybe there's some file ownership issue by which an ordinary user can't access the GAP packages installed by root?

Alasdair gravatar imageAlasdair ( 2014-09-26 15:13:37 +0200 )edit

It's not that - I've adjusted the ownership and still it doesn't work. So I'm installing the package again...wait a bit... yes - now it works!

Alasdair gravatar imageAlasdair ( 2014-09-26 16:19:43 +0200 )edit

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Asked: 2014-09-26 08:41:20 +0200

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Last updated: Sep 26 '14