Opened 2 years ago
Closed 2 years ago
#20018 closed defect (fixed)
init for endomorphism of projective subschemes fails
Reported by:  bhutz  Owned by:  bhutz 

Priority:  minor  Milestone:  sage7.1 
Component:  algebraic geometry  Keywords:  
Cc:  Merged in:  
Authors:  Ben Hutz  Reviewers:  Adam Towsley 
Report Upstream:  N/A  Work issues:  
Branch:  03736f5 (Commits)  Commit:  03736f56d5bff62e77344494349864f42a43fdd0 
Dependencies:  Stopgaps: 
Description
The following example does not work
sage: R.<t>=PolynomialRing(QQ) sage: P.<x,y,z> = ProjectiveSpace(R,2) sage: X = P.subscheme(x^2y^2) sage: H = Hom(X,X) sage: f = H([x^2,y^2,x*z])
but does work in affine space. It seems that the check in init is not quite doing the right thing.
Change History (9)
comment:1 Changed 2 years ago by
 Branch set to u/bhutz/ticket/20018
comment:2 Changed 2 years ago by
 Commit set to bcb68d013dc8786c8f897f5d2b0c3329a93822a5
 Status changed from new to needs_review
comment:3 Changed 2 years ago by
 Commit changed from bcb68d013dc8786c8f897f5d2b0c3329a93822a5 to dd2c436278540666c3afd93f48ca7cae5977f64d
Branch pushed to git repo; I updated commit sha1. New commits:
dd2c436  20018: changes to scheme morphism polynomial initialization

comment:4 Changed 2 years ago by
 Commit changed from dd2c436278540666c3afd93f48ca7cae5977f64d to 9fcdd5bc8e44c0553c2d26bb9752d57534afa4a4
comment:5 Changed 2 years ago by
 Commit changed from 9fcdd5bc8e44c0553c2d26bb9752d57534afa4a4 to 03736f56d5bff62e77344494349864f42a43fdd0
Branch pushed to git repo; I updated commit sha1. New commits:
03736f5  Merge branch '7.1.beta5' into ticket/20018

comment:6 Changed 2 years ago by
 Status changed from needs_review to positive_review
comment:7 Changed 2 years ago by
 Status changed from positive_review to needs_work
Reviewer name is missing
comment:8 Changed 2 years ago by
 Reviewers set to Adam Towsley
 Status changed from needs_work to positive_review
comment:9 Changed 2 years ago by
 Branch changed from u/bhutz/ticket/20018 to 03736f56d5bff62e77344494349864f42a43fdd0
 Resolution set to fixed
 Status changed from positive_review to closed
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Since I didn't get any input from the sagedevel thread I went ahead an implemented one possible correction to these issues. At this stage I welcome comments on the solution.
The key points are as follows
This allows initialization to work in more situations such as for the problem in the description, but also corrects the weird behavior such as:
old behavior
new behavior
One consequence is the projective_embedding functionality in toric variety seems to be programmed to expect the reduction. Consequently, I've had the creation code use the quotient ring variables, so that behavior matches the current doctests.
In a couple places in elliptic_curve/jacobian.py the morphism returned is now in a slightly different form. This did not seem to big a difference, so I just updated those doctests.