#14353: Factor toric morphism into surjective and generically injective
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Reporter: vbraun | Owner: AlexGhitza
Type: enhancement | Status: needs_review
Priority: major | Milestone: sage-5.9
Component: algebraic geometry | Resolution:
Keywords: | Work issues:
Report Upstream: N/A | Reviewers:
Authors: Volker Braun | Merged in:
Dependencies: | Stopgaps:
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Comment (by novoselt):
Here is some work in progress, does not look good in the patch, but it
removes `restrict_to_image` in the end and adds `factor` instead, diff
blends these activities.
No other new methods apart `is_birational` which is not proper yet and
there are some failures with composition of morphisms - I completely agree
that these fans have to be accessed through morphisms, no need for new
names.
As for `Sigma_i` indeed we have a choice, but I'd rather stick with "the
big one" because:
- it makes it independent of the domain fan, which is symmetrical to
`Sigma_s` not depending on the codomain fan;
- the corresponding variety will be a closed subvariety of the codomain;
- it is easier to implement/faster to compute;
- last but not least - I already have it in the patch ;-)
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Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/14353#comment:6>
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