Chart.subchart_poset, superchart_poset, Manifold.chart_poset

[mkoeppe]

Families of charts on a manifold are quasiordered by set inclusion of domains, ignoring coord_string. Subqosets can be defined by filtering by coord_string; an optional argument of Manifold.chart_poset will do this.

As in #31736, the poset quotients by the equivalence relation, so its elements are finite families of charts that have the same domain.

Depends on #31720

CC: @egourgoulhon @mjungmath

Component: manifolds

Issue created by migration from https://trac.sagemath.org/ticket/31771

[mkoeppe]

Dependencies: #31720

[mjungmath]

comment:2

Probably perfect substitute for the current display implementation of scalar fields.

[mjungmath]

comment:3

I think this quasi order is exactly what we need for presheaves.

Since the set of frames as well as of charts each constitute a presheaf, what if we wrap this up in #31703?

Besides, what do you mean with "Subqosets"?

[mkoeppe]

comment:4

qoset = quasi-ordered set

[mjungmath]

comment:5

But when we take coord_string into account again, shouldn't this become a poset? So you mean subqosets that are actual posets, right?

[mkoeppe]

comment:6

Two subsets with a different name can turn out to be equal. If two restrictions of a chart are defined on these two subsets, then I think these will be distinct but equal elements of the qoset as well.

[mkoeppe]

comment:7

Replying to @mjungmath:

Since the set of frames as well as of charts each constitute a presheaf, what if we wrap this up in #31703?

Sure, that would work; perhaps you can expand that ticket's description a bit.