#14300: CyclotomicField's is_isomorphic is mathematically incorrect
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Reporter: robharron | Owner: davidloeffler
Type: defect | Status: new
Priority: critical | Milestone: sage-5.9
Component: number fields | Keywords: CyclotomicField
Work issues: | Report Upstream: N/A
Reviewers: | Authors:
Merged in: | Dependencies:
Stopgaps: |
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If K is a CyclotomicField, then K.is_isomorphic(L) returns true as long as
L is a number field and K has an embedding in to L!
{{{
sage: K = CyclotomicField(4)
sage: N = K.extension(x^2-5, 'z')
sage: K.is_isomorphic(N)
True
}}}
Is there a reason that CyclotomicField overrides the generic version of
this? I guess one could first do the quick check: if L is a
CyclotomicField, then checking they are isomorphic just means checking
they are both the nth cyclotomic field (I assume the n is stored somewhere
easily accessible).
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14300>
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