subgroup of number field unit group

asked 2015-07-08 00:59:55 +0100

Kate Stange
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updated 2015-07-31 17:54:03 +0100

5311 ●4 ●44 ●118

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 15:48:34 +0100

tmonteil
27423 ●31 ●204 ●517 http://wiki.sagemath.o...

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 ( 2015-07-08 16:50:36 +0100 )edit

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Asked: 2015-07-08 00:59:55 +0100

Seen: 562 times

Last updated: Jul 08 '15

subgroup of number field unit group edit