Opened 5 years ago

Last modified 5 years ago

#22150 needs_work enhancement

Set embedding of extension in QQ[2^(1/3)]

Reported by: vdelecroix Owned by:
Priority: major Milestone: sage-8.0
Component: number fields Keywords:
Cc: Merged in:
Authors: Vincent Delecroix Reviewers:
Report Upstream: N/A Work issues: see patchbot report
Branch: u/vdelecroix/22150 (Commits, GitHub, GitLab) Commit: 3360768681a2d913a9ec7987aa423278aca15cf5
Dependencies: Stopgaps:

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Description (last modified by vdelecroix)

Before 

sage: QQ[2^(1/3)].coerce_embedding()
Generic morphism:
  From: Number Field in a with defining polynomial x^3 - 2
  To:   Real Lazy Field
  Defn: a -> 1.259921049894873?

After 

sage: QQ[2^(1/3)].coerce_embedding()
Generic morphism:
  From: Number Field in a with defining polynomial x^3 - 2
  To:   Algebraic Real Field
  Defn: a -> 1.259921049894873?

Change History (10)

comment:1 Changed 5 years ago by vdelecroix

  • Branch set to u/vdelecroix/22150
  • Commit set to 3360768681a2d913a9ec7987aa423278aca15cf5
  • Status changed from new to needs_review

New commits:

​336076822150 set embedding appropriately in QQ[2^(1/3)]

comment:2 Changed 5 years ago by mmezzarobba

  • Status changed from needs_review to needs_work
  • Work issues set to see patchbot report

comment:3 Changed 5 years ago by chapoton

Needs rebase.

Moreover, there is a problem coming from 

sage: sqrt(-3).is_real()
True

comment:4 Changed 5 years ago by mmezzarobba

Whoops, I had forgotten about this ticket, but see #23117.

comment:5 Changed 5 years ago by chapoton

  • Milestone changed from sage-7.5 to sage-duplicate/invalid/wontfix
  • Status changed from needs_work to needs_review

so we can close this as duplicate, right ?

comment:6 Changed 5 years ago by chapoton

Hmm. currently we get: 

Generic morphism:
  From: Number Field in a with defining polynomial x^3 - 2
  To:   Real Lazy Field
  Defn: a -> 1.259921049894873?

with target the real lazy field instead of AA.

comment:7 Changed 5 years ago by vdelecroix

  • Milestone changed from sage-duplicate/invalid/wontfix to sage-8.0
  • Status changed from needs_review to needs_work

It would have been better if you just have read the ticket description.

comment:8 Changed 5 years ago by chapoton

What do you mean ? The ticket description is no longer valid...

comment:9 follow-up: Changed 5 years ago by vdelecroix

  • Description modified (diff)

The branch is not either. I think that #23117 was actually a bad idea. Coercion should not go through the real lazy field.

comment:10 in reply to: ↑ 9 Changed 5 years ago by mmezzarobba

Replying to vdelecroix:

The branch is not either. I think that #23117 was actually a bad idea. Coercion should not go through the real lazy field.

I agree that complex embeddings should go to QQbar or something like that by default, but for me this is a separate issue, already tracked elsewhere.

However, having the K[α] syntax create the “standard” embedding makes more sense to me (less confusing, probably breaks fewer existing things) than having it attempt to embed the number field in α's parent or something like that—if that's what you have in mind.

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