#18175: Implement categories for topological and metric spaces and related
categories
-------------------------------------+-------------------------------------
       Reporter:  tscrim             |        Owner:  tscrim
           Type:  enhancement        |       Status:  new
       Priority:  major              |    Milestone:  sage-6.8
      Component:  categories         |   Resolution:
       Keywords:  geometry,          |    Merged in:
  topology, sd67                     |    Reviewers:
        Authors:  Travis Scrimshaw   |  Work issues:
Report Upstream:  N/A                |       Commit:
         Branch:                     |  95a30aa57fc62f23a884790b57835d107d8bdeef
  public/categories/topological_metric_spaces-18175|     Stopgaps:
   Dependencies:  #18174 #17160      |
-------------------------------------+-------------------------------------

Comment (by egourgoulhon):

 Replying to [comment:27 tscrim]:

 > So you're saying there should be a canonical functor from complex
 manifolds to almost complex manifolds given by changing the base field
 from  '''C''' to '''R''' (as opposed to it being a subcategory)? From what
 you said, this seems to be the best course of action.

 This seems also the best to me.

 >
 > For the example with finite fields, do they have a reasonable topology
 and could that define a transition map? If so, then I think we should
 enforce differentiable as being over '''R'''.
 If we enforce this, then we are back to the diagram of comment:21. But I
 wonder now if a best strategy would be to leave instead the base field
 generic, with the understanding that ''differentiable'' means
 '''K'''-''differentiable'', where '''K''' stands for the base field. Then
 the diagram becomes
 {{{
             Manifolds
                |
          Differentiable
                |
             Smooth
            /      \
       Analytic   AlmostComplex
          |
       Complex
 }}}
 with
 - `Manifolds`: topological manifolds over a topological field '''K'''
 - `Differentiable`: topological manifolds over '''K''' with a
 '''K'''-differentiable atlas
 - `Smooth`: topological manifolds over '''K''' with a '''K'''-infinitely
 differentiable atlas
 - `Analytic`: topological manifolds over '''K''' with a '''K'''-analytic
 atlas
 - `AlmostComplex`: smooth manifolds over '''K'''='''R''' with an almost
 complex structure
 - `Complex`: '''C'''-analytic manifolds over '''K'''='''C'''

--
Ticket URL: <http://trac.sagemath.org/ticket/18175#comment:28>
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