De Rham cohomology

[mjungmath]

We add de Rham cohomology to SageManifolds with limited functionality. For now, the implementation will only consist of abstract elements that are given by representatives of mixed forms, i.e. we take closed mixed forms (with check?), put a bracket around it and do all computations in the algebra of mixed forms.

See also: #31691

CC: @egourgoulhon @tscrim

Component: manifolds

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/31693

[mjungmath]

comment:4

Already part of #31691. This can be closed.

[tscrim]

comment:6

This is how you make a ticket invalid.

[tscrim]

Reviewer: Travis Scrimshaw