Opened 3 years ago

Closed 3 years ago

#26378 closed defect (fixed)

Bugs in Mass formula for quadratic forms

Reported by: sbrandhorst Owned by:
Priority: major Milestone: sage-8.4
Component: quadratic forms Keywords:
Cc: anna, haensch Merged in:
Authors: Frédéric Chapoton Reviewers: Simon Brandhorst
Report Upstream: N/A Work issues:
Branch: 12c4342 (Commits, GitHub, GitLab) Commit: 12c434294a7fb4dbe45b424a4069bc9d590e96fa
Dependencies: Stopgaps:

Status badges

Description

sage: Q = QuadraticForm(Matrix(ZZ,2,[2,1,1,2]))
sage: Q.conway_mass()
....
TypeError: unable to convert sqrt(1/144) to a rational

The correct result is 1/12.

The method seems to fail in dimension 6 as well for example for the E6 lattice.

Change History (6)

comment:1 Changed 3 years ago by chapoton

  • Authors set to Frédéric Chapoton
  • Branch set to u/chapoton/26378
  • Commit set to 12c434294a7fb4dbe45b424a4069bc9d590e96fa
  • Status changed from new to needs_review

here is a fix proposal, not tested on E6


New commits:

12c4342fixing conway mass

comment:2 Changed 3 years ago by sbrandhorst

  • Status changed from needs_review to positive_review

I tested this against a few thousand lattices of determiants <= 400 in dimensions <= 6 against magma. The answers agree. Thank you so much Frédéric :-).

comment:3 Changed 3 years ago by vbraun

  • Status changed from positive_review to needs_work

Reviewer name...

comment:4 Changed 3 years ago by sbrandhorst

  • Reviewers set to Simon Brandhorst

woops

comment:5 Changed 3 years ago by sbrandhorst

  • Status changed from needs_work to positive_review

comment:6 Changed 3 years ago by vbraun

  • Branch changed from u/chapoton/26378 to 12c434294a7fb4dbe45b424a4069bc9d590e96fa
  • Resolution set to fixed
  • Status changed from positive_review to closed
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