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subgroup of number field unit group

asked 2015-07-07 17:59:55 -0600

Kate Stange gravatar image

updated 2015-07-31 10:54:03 -0600

FrédéricC gravatar image

I would like to be able to create subgroups of a unit group generated by given elements. I haven't, thus far, been able to find a way to make this work. The following doesn't work:

N.<a> = NumberField(x^3+2)
G = N.unit_group()
g = G.random_element()
G.subgroup([g])

Can anyone help me find a workaround?

(Note: it appears to be a bug, see trac.sagemath.org/ticket/18863, but I'm just looking for a workaround for now.)

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answered 2015-07-08 08:48:34 -0600

tmonteil gravatar image

It seems you hit a bug with gap interface (though i am not able to explain further):

sage: G.inject_variables()
Defining u0, u1
sage: gap(u0)
f1
sage: gap(u1)
TypeError: Gap produced error output
Error, Variable: 'u1' must have a value
       executing $sage5:=u1;;

sage: u1.value()
a + 1
sage: gap(u1.value())
a+1

It is not clear to me what kind of value is gap requiring. I tried with an embedded number field, but i get the same error.

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Ticket # ?

kcrisman gravatar imagekcrisman ( 2015-07-08 09:50:36 -0600 )edit

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Asked: 2015-07-07 17:59:55 -0600

Seen: 168 times

Last updated: Jul 08 '15