Opened 3 years ago
Closed 3 years ago
#22667 closed defect (fixed)
Fix computation of inverse metric on parallelizable manifolds
Reported by:  egourgoulhon  Owned by:  

Priority:  major  Milestone:  sage8.0 
Component:  geometry  Keywords:  metric, manifold 
Cc:  tscrim  Merged in:  
Authors:  Eric Gourgoulhon  Reviewers:  Travis Scrimshaw 
Report Upstream:  N/A  Work issues:  
Branch:  fc04276 (Commits)  Commit:  fc042765144026ad59876ad8680f538c6e274ebc 
Dependencies:  #22637  Stopgaps: 
Description
The following is a bug:
sage: S1 = Manifold(1, 'S^1') # the circle sage: U = S1.open_subset('U') # the complement of one point sage: Xt.<t> = U.chart('t:(0,2*pi)') # the standard angle coordinate sage: V = S1.open_subset('V') # the complement of the point t=pi sage: Xu.<u> = V.chart('u:(0,2*pi)') # the angle tpi sage: S1.declare_union(U, V) sage: e = S1.vector_frame('e') # a global vector frame (makes S^1 parallelizable) sage: g = S1.metric('g') sage: g[e,0,0] = 1 sage: g[[e,0,0]].display() S^1 > R on U: t > 1 on V: u > 1 sage: g.inverse()[[e,0,0]].display() S^1 > R on U: t > 1
The last output should be
S^1 > R on U: t > 1 on V: u > 1
since the component g^{00} of the inverse metric in the global frame e is the constant scalar field 1, which must have a representation on both open subsets U and V. The current ticket fixes this.
Change History (6)
comment:1 Changed 3 years ago by
 Branch set to public/manifolds/buginversemetric22667
 Cc tscrim added
 Commit set to 73638157694451c7bebc4575b38aa525c457b9ab
 Status changed from new to needs_review
comment:2 followup: ↓ 4 Changed 3 years ago by
 Reviewers set to Travis Scrimshaw
One little thing: you should put the try/except block on the minimal number of lines as it makes for easier maintenance/debugging. So I think it should just include the assignment of gmat
. Otherwise LGTM.
comment:3 Changed 3 years ago by
 Commit changed from 73638157694451c7bebc4575b38aa525c457b9ab to fc042765144026ad59876ad8680f538c6e274ebc
Branch pushed to git repo; I updated commit sha1. New commits:
fc04276  Better treatment of exceptions in inverse metric computation

comment:4 in reply to: ↑ 2 Changed 3 years ago by
Replying to tscrim:
One little thing: you should put the try/except block on the minimal number of lines as it makes for easier maintenance/debugging. So I think it should just include the assignment of
gmat
.
Done (I've also included the computation of the matrix inverse in the try block).
comment:6 Changed 3 years ago by
 Branch changed from public/manifolds/buginversemetric22667 to fc042765144026ad59876ad8680f538c6e274ebc
 Resolution set to fixed
 Status changed from positive_review to closed
This should be the last of the manifold bug fixes relative to Sage 7.5.1 ;)
New commits:
Fix treatment of pullback on parallelizable manifolds
Change the name of first argument to 'self' in nested method _pullback_chart of DiffMap
Revert to previous version of nested function _pullback_chart in DiffMap.pullback
Merge branch 'public/manifolds/bugpullbackparallelizable' of git://trac.sagemath.org/sage into Sage 7.6.rc0
Fix treatment of restrictions of tensor fields with parallelizable domains
Fix computation of inverse metric on parallelizable manifolds (#22667)