Opened 18 months ago

Last modified 3 months ago

#31241 new enhancement

Forgetful Functors for Manifolds — at Initial Version

Reported by: gh-mjungmath Owned by:
Priority: major Milestone: sage-9.7
Component: manifolds Keywords:
Cc: tscrim, egourgoulhon, mkoeppe Merged in:
Authors: Reviewers:
Report Upstream: N/A Work issues:
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Dependencies: Stopgaps:

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Description

It would be nice to allow forgetful functors for manifolds. In particular:

  • differentiable manifold -> topological manifold
  • (Pseudo-)Riemannian manifold -> differentiable manifold
  • topological manifold -> sets (?)

and probably even more. The last point might also be useful in terms of #30832.

At the moment, we have the following behavior (which could be seen as a bug):

sage: from sage.categories.functor import ForgetfulFunctor
sage: from sage.categories.manifolds import Manifolds
sage: F = ForgetfulFunctor(Manifolds(RR).Differentiable(), Manifolds().Topological())
sage: M = Manifold(2, 'M')
sage: F(M)
2-dimensional differentiable manifold M

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