is postcritically finite failure for extensions

[bhutz]

When the field extension needs to be extended there can be a conflict of variable names

sage: K.<v> = QuadraticField(-7)
sage: P.<x,y> = ProjectiveSpace(K, 1)
sage: f = DynamicalSystem([x^3 + v*x*y^2, y^3])
sage: fbar = f.change_ring(QQbar)
sage: fbar.is_postcritically_finite()

Component: dynamics

Keywords: SI2019

Author: Ben Hutz

Branch/Commit: 9d99a13

Reviewer: Jasmine Camero, Olivia Schwager

Issue created by migration from https://trac.sagemath.org/ticket/25243

[bhutz]

Author: Ben Hutz

[bhutz]

New commits:

d084135

25243: is_postcritically finite fixes for dynamical systems

[bhutz]

Commit: d084135

[bhutz]

Branch: u/bhutz/25243_pcf_fix

[sagetrac-git]

Branch pushed to git repo; I updated commit sha1. New commits:

d5d5db6	Merge branch 8.3.beta2 into t/25243/25243_pcf_fix
f434ad0	25243: use .change_names

[sagetrac-git]

Changed commit from d084135 to f434ad0

[Torrencem]

comment:3

Fixed merge conflict with master, manually implemented the same code changes, and removed changes to deprecated code. Also have another test case:

K.<a>=QuadraticField(-1)
P.<x,y>=ProjectiveSpace(K,1)
f=DynamicalSystem([x^4 + (-1+2*a)*x*y^3,y^4], domain=P)
f.is_postcritically_finite()

---

New commits:

6a9a729

Fix merge for ticket

[Torrencem]

Changed commit from f434ad0 to 6a9a729

[Torrencem]

Changed branch from u/bhutz/25243_pcf_fix to u/gh-Torrencem/25243_pcf_fix

[Torrencem]

Changed keywords from none to SI2019

[Torrencem]

comment:4

The following changed line's purpose is unclear to us. When we removed it, and changed the variable names, it seemed to still work well without it:

L = K.change_names('a')

Is this line still necessary?

[bhutz]

comment:5

It had been necessary, unless extension/compositums do their own name collision resolution now, leaving the default names was regularly causing name conflict, so that tweak avoided that collision.

[bhutz]

comment:6

Did a little testing. It seems to no longer be an issue. I wasn't able to get an example that fails. Give this branch a try.

[bhutz]

Changed branch from u/gh-Torrencem/25243_pcf_fix to u/bhutz/25243_pcf_fix2

[bhutz]

Changed commit from 6a9a729 to 9d99a13

[bhutz]

comment:7

some trouble pushing my original branch. Here is a new one.

---

New commits:

ab6fb91	25243: remove extra name change
9d99a13	Merge branch beta8.rc1 into t/25243/25243_pcf_fix

[oliviaschwager]

Reviewer: Jasmine Camero, Olivia Schwager

[vbraun]

Changed branch from u/bhutz/25243_pcf_fix2 to 9d99a13