Opened 10 years ago

Closed 7 years ago

#11276 closed defect (duplicate)

bug in documentation for non_surjective for Galois representations attached to elliptic curves

Reported by: dpathakjee Owned by: cremona
Priority: minor Milestone: sage-duplicate/invalid/wontfix
Component: elliptic curves Keywords: galois representation, elliptic curves, non_surjective, documentation
Cc: was Merged in:
Authors: Reviewers: Chris Wuthrich
Report Upstream: N/A Work issues:
Branch: Commit:
Dependencies: Stopgaps:

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Description (last modified by chapoton)

non_surjective() docstring incorrectly states that it's inconclusive and often wrong for p=2. The function it calls, is_surjective, is correct for p=2.

The docstring states that "[the] list of primes p such that the mod-p representation *might* not be surjective... usually contains 2, because of shortcomings of the algorithm..." However, non_surjective calls is_surjective, which should always be correct for p=2,3 because it computes the Galois group of the 2-division polynomial. (More precisely, its helper, _is_surjective, does this.) I suspect this caveat may have been written before the special cases for p=2,3 in _is_surjective had been written.

All that really needs to be done is to remove the phrase "(this list usually contains 2, because of shortcomings of the algorithm)" from the docstring.

See also #11271, #11270

Change History (5)

comment:1 Changed 8 years ago by chapoton

  • Description modified (diff)

comment:2 Changed 8 years ago by jdemeyer

  • Milestone changed from sage-5.11 to sage-5.12

comment:3 Changed 7 years ago by wuthrich

  • Milestone changed from sage-6.1 to sage-duplicate/invalid/wontfix
  • Status changed from new to needs_review

This is a duplicate (well, striclty speaking a sub-ticket) of #11271. This should be closed.

comment:4 Changed 7 years ago by pbruin

  • Reviewers set to Chris Wuthrich
  • Status changed from needs_review to positive_review

comment:5 Changed 7 years ago by vbraun

  • Resolution set to duplicate
  • Status changed from positive_review to closed
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