Opened 8 months ago

Closed 8 months ago

# Categories for Homset of Manifolds do not meet

Reported by: Owned by: gh-mjungmath major sage-9.3 manifolds tscrim, egourgoulhon Michael Jung Travis Scrimshaw N/A 111015d 111015d2ce8cd36edb4ce5a11926fd412e644f7c

### Description

Here is a minimal example:

```sage: R3 = EuclideanSpace(3)
....: S2 = R3.sphere(coordinates='stereographic'); S2
2-sphere S^2 of radius 1 smoothly embedded in the Euclidean space E^3
sage: I = S2.identity_map()
sage: iota = S2.embedding()
sage: iota * I
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-5-2ed3e7f8e656> in <module>
----> 1 iota * I

~/Projekte/sage-devel/local/lib/python3.8/site-packages/sage/categories/map.pyx in sage.categories.map.Map.__mul__ (build/cythonized/sage/categories/map.c:7680)()
895         if right.codomain() != self.domain():
896             raise TypeError("self (=%s) domain must equal right (=%s) codomain" % (self, right))
--> 897         return self._composition(right)
898
899     def _composition(self, right):

~/Projekte/sage-devel/local/lib/python3.8/site-packages/sage/categories/map.pyx in sage.categories.map.Map._composition (build/cythonized/sage/categories/map.c:7854)()
935         """
936         category = self.category_for()._meet_(right.category_for())
--> 937         H = homset.Hom(right.domain(), self._codomain, category)
938         return self._composition_(right, H)
939

~/Projekte/sage-devel/local/lib/python3.8/site-packages/sage/categories/homset.py in Hom(X, Y, category, check)
416                     # available for the following error message. It simply
417                     # belongs to the wrong category.
--> 418                     raise ValueError("{} is not in {}".format(O, category))
419
420         # Construct H

ValueError: Euclidean space E^3 is not in Join of Category of compact topological spaces and Category of smooth manifolds over Real Field with 53 bits of precision and Category of complete metric spaces
```

### comment:1 Changed 8 months ago by gh-mjungmath

• Branch set to u/gh-mjungmath/categories_for_homset_of_manifolds_do_not_meet

### comment:2 Changed 8 months ago by gh-mjungmath

• Commit set to be52d78edd5b44a41e9a57551e6a105418eeffda
• Status changed from new to needs_review

New commits:

 ​be52d78 `Trac #31233: meet categories`

### comment:3 Changed 8 months ago by gh-mjungmath

There are some failed doctests in `integrated_curve.py` on `__recude__`. However, I think this is the proper way to do it. Just overwrite the docstrings?

### comment:4 Changed 8 months ago by tscrim

It depends on what the failures are. In this case, it seems like the best thing is to just change them.

This is probably the right solution. It feels slightly strange to weaken the type of morphism, but this doesn't make so much sense at the category level I think.

### comment:5 Changed 8 months ago by git

• Commit changed from be52d78edd5b44a41e9a57551e6a105418eeffda to 78f7af381e3bd01f621001e1947057844bd8e276

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

 ​78f7af3 `Trac #31233: category of homset docstring adapted`

### comment:6 Changed 8 months ago by git

• Commit changed from 78f7af381e3bd01f621001e1947057844bd8e276 to 8d31e0f74fed80c426995089e6455b026a21cb8d

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

 ​8d31e0f `Trac #31233: fixing format`

### comment:7 Changed 8 months ago by git

• Commit changed from 8d31e0f74fed80c426995089e6455b026a21cb8d to 111015d2ce8cd36edb4ce5a11926fd412e644f7c

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

 ​111015d `Trac #31233: adapt homsets in docstring`

### comment:8 Changed 8 months ago by gh-mjungmath

Even mathematically it makes more sense to restrict the categories.

This should be it. Wait for green patchbot.

### comment:9 Changed 8 months ago by tscrim

• Reviewers set to Travis Scrimshaw
• Status changed from needs_review to positive_review

LGTM.

Thanks!

### comment:11 Changed 8 months ago by vbraun

• Branch changed from u/gh-mjungmath/categories_for_homset_of_manifolds_do_not_meet to 111015d2ce8cd36edb4ce5a11926fd412e644f7c
• Resolution set to fixed
• Status changed from positive_review to closed
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