#14353: Factor toric morphism into surjective and generically injective
----------------------------------------------------+-----------------------
Reporter: vbraun | Owner:
AlexGhitza
Type: enhancement | Status:
needs_work
Priority: major | Milestone: sage-5.9
Component: algebraic geometry | Resolution:
Keywords: toric | Work issues: morphism
composition
Report Upstream: N/A | Reviewers: Andrey
Novoseltsev, Volker Braun
Authors: Volker Braun, Andrey Novoseltsev | Merged in:
Dependencies: | Stopgaps:
----------------------------------------------------+-----------------------
Changes (by {'newvalue': u'Volker Braun, Andrey Novoseltsev', 'oldvalue':
u'Volker Braun'}):
* status: needs_review => needs_work
* author: Volker Braun => Volker Braun, Andrey Novoseltsev
* keywords: => toric
* reviewer: => Andrey Novoseltsev, Volker Braun
* work_issues: => morphism composition
Old description:
> This ticket implements the HLY factorization into a surjective and a
> generically injective toric morphism.
New description:
This ticket implements factorization into a surjective, birational, and
injective toric morphism.
'''Apply:'''
1. [attachment:trac_14353_fan_morphism_factoring.patch]
1. [attachment:trac_14353_auxiliary_methods.patch]
1. [attachment:trac_14353_toric_morphism_factoring.patch]
--
Comment:
Hi Volker, I propose this version based on triple factorization for both
fan and variety morphisms. I hope the documentation is written clearly and
the example chosen gives a good idea what is what. The only remaining
problem is that I really want to multiply factors back into the original
one. For fan morphisms I just added `__mul__` as they are standalone
(although it may make sense to change that...), but toric morphisms should
follow coercion rules, so implementing the double underscore method as it
is done now is not acceptable. And even with it there is an issue of
comparing, although it does seem that the result is correct.
Anyway: let me know what you think of composition and if the rest looks
OK!
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14353#comment:7>
Sage <http://www.sagemath.org>
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