#20676: Projective closure and affine patches for algebraic curves
-------------------------------------+-------------------------------------
       Reporter:  gjorgenson         |        Owner:
           Type:  enhancement        |       Status:  needs_work
       Priority:  minor              |    Milestone:  sage-7.3
      Component:  algebraic          |   Resolution:
  geometry                           |    Merged in:
       Keywords:                     |    Reviewers:  Ben Hutz
        Authors:  Grayson Jorgenson  |  Work issues:
Report Upstream:  N/A                |       Commit:
         Branch:                     |  0039d7b13dad64025ef70542f407bf3af7423e1a
  u/gjorgenson/ticket/20676          |     Stopgaps:
   Dependencies:  #20697, #20698     |
-------------------------------------+-------------------------------------
Changes (by bhutz):

 * status:  needs_review => needs_work
 * reviewer:   => Ben Hutz


Comment:

 - line 1916:

 {{{R.ideal([R(f) for f in self.defining_polynomials()])}}}
 could be replaced with
 {{{self.defining_ideal()}}}

 - projective closure should take projective space parameter
 {{{
 A.<x,y> = AffineSpace(QQ, 2)
 P.<u,v,w>=ProjectiveSpace(QQ,2)
 C = Curve([y-x^2], A)
 D=C.projective_closure(1,P)
 }}}

 - Affine patch should take affine space parameter
 {{{
 A.<x,y> = AffineSpace(QQ, 2)
 P.<u,v,w>=ProjectiveSpace(QQ,2)
 C = Curve([u^2-v^2], P)
 C.affine_patch(1,A)
 }}}

 - Affine patch should have a default patch and that default should match
 up with the projective closure default
 {{{
 A.<x,y,z> = AffineSpace(GF(3), 3)
 C = Curve([y-x^2,z-x^3], A)
 D=C.projective_closure()
 D.affine_patch()==C
 }}}

 - you should mention in the doc for projective embedding that the image is
 the projective closure

--
Ticket URL: <http://trac.sagemath.org/ticket/20676#comment:15>
Sage <http://www.sagemath.org>
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