#18443: Multiplier spectra for projective morphisms
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Reporter: gjorgenson | Owner:
Type: enhancement | Status: needs_work
Priority: minor | Milestone: sage-6.8
Component: algebraic | Resolution:
geometry | Merged in:
Keywords: | Reviewers: Ben Hutz
Authors: Grayson Jorgenson | Work issues:
Report Upstream: N/A | Commit:
Branch: | 71d1123d488ff029e34f50600554aa4fd5be32cd
u/gjorgenson/ticket/18443 | Stopgaps:
Dependencies: #18409 |
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Comment (by gjorgenson):
For the formal==True case I used the technique in the morphism change_ring
function to create the homomorphism between polynomial rings to use on F
and this seems to have addressed the issues so far. For the formal==False
case, the conversion already seemed to be working, but the
_number_field_from_algebraics version of the map wasn't needed for finding
roots.
I found another problem though:
{{{
P.<x,y> = ProjectiveSpace(QQ,1)
H = End(P)
f = H([x^2 - 3/4*y^2,y^2])
f.multiplier_spectra(2)
}}}
gives [1,1] back which isn't correct.
I didn’t catch this before, but multiplier_spectra should only return [1]
here, because there is only one two cycle. The collapsing causes this two
cycle to turn into a root of multiplicity 2 of the dynatomic polynomial,
so the algorithm I use to pick representatives from cycles doesn’t work.
I will implement a fix attempt for this next, but I wanted to push up the
current commit before doing so.
--
Ticket URL: <http://trac.sagemath.org/ticket/18443#comment:10>
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