Opened 13 years ago

Closed 8 years ago

# relative number field subfield method -- unclear documentation

Reported by: Owned by: dmharvey davidloeffler major sage-5.11 number fields sd51 sage-5.11.rc0 Alejandro Argaez Michiel Kosters N/A

### Description

Consider

```sage: R.<a> = NumberField(x^4 - 2*x^2 - 1)
sage: S.<i> = R.extension(x^2 + 1)
sage: S.subfield(a + i/a)
```

The S.subfield method documentation says that it constructs QQ(alpha), but this is false, I think it constructs R(alpha). In the above example, S.subfield(a + i/a) returns a number field of degree 8 over Q, whereas a + i/a has degree 4 over QQ (the minimal polynomial is `x^4 - 4x^2 + 8`).

### comment:1 Changed 13 years ago by mabshoff

• Milestone set to sage-3.4.1

### comment:2 Changed 12 years ago by davidloeffler

• Component changed from number theory to number fields
• Owner changed from was to davidloeffler

### Changed 8 years ago by ArgaezG

patch against sage 5.10

### comment:3 Changed 8 years ago by ArgaezG

• Authors set to Alejandro Argaez
• Report Upstream set to N/A
• Status changed from new to needs_review

### comment:4 Changed 8 years ago by mkosters

• Keywords sd51 added

### comment:5 Changed 8 years ago by ArgaezG

• Reviewers set to Michiel Kosters
• Status changed from needs_review to positive_review

I happy with changes suggested by Michiel, and he is happy with mine.

### comment:6 Changed 8 years ago by mkosters

Apply trac_5392_subfield_review.patch after trac_5392.patch​

### comment:7 Changed 8 years ago by jdemeyer

• Status changed from positive_review to needs_work

The reviewer patch needs a proper commit message, use `hg qrefresh -e` for this.

### comment:8 follow-up: ↓ 9 Changed 8 years ago by mkosters

@jdemeyer: is it correct now?

### comment:9 in reply to: ↑ 8 Changed 8 years ago by mstreng

• Status changed from needs_work to positive_review

Replying to mkosters:

@jdemeyer: is it correct now?

It has a proper commit message now. So assuming this is the same patch, I'll put this to positive review again.

### comment:10 Changed 8 years ago by jdemeyer

• Merged in set to sage-5.11.rc0
• Resolution set to fixed
• Status changed from positive_review to closed
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