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[Merged by Bors] - feat(geometry/manifold/sheaf/basic): sheaf of functions satisfying a local_invariant_prop #19146

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@hrmacbeth hrmacbeth commented Jun 2, 2023

Define structure_groupoid.local_invariant_prop.sheaf, the sheaf-of-types of functions f : M → M' (for charted spaces M, M') satisfying some local property in the sense of structure_groupoid.local_invariant_prop (for example continuity, differentiability, smoothness).


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@github-actions github-actions bot added the modifies-synchronized-file This PR touches a files that has already been ported to mathlib4, and may need a synchronization PR. label Jun 2, 2023
@hrmacbeth hrmacbeth added awaiting-review The author would like community review of the PR awaiting-CI The author would like to see what CI has to say before doing more work. t-differential-geometry Manifolds, etc. labels Jun 2, 2023
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src/geometry/manifold/sheaf/basic.lean Show resolved Hide resolved
import geometry.manifold.local_invariant_properties
import topology.sheaves.local_predicate

/-! # Generic construction of a sheaf from a `local_invariant_prop` on a manifold -/
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Can you expand this docstring, by describing the main definition and what it constructs?

Do I understand correctly that this is not universe-polymorphic (i.e., M and M' need to be in the same universe). Isn't that a problem for concrete applications?

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I wrote a module docstring and I opened
https://leanprover.zulipchat.com/#narrow/stream/144837-PR-reviews/topic/.2319146.20sheaves.20on.20manifolds
to solicit help with the universe issue.

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bors bot pushed a commit that referenced this pull request Jun 20, 2023
…tructure (#19147)

We have a long-running conversation in mathlib about whether function spaces should be implemented as subtypes or as structures.  This PR proposes to change `cont_mdiff_map`, the type of smooth functions between manifolds `M` and `M'`, from a "structure" implementation to a "subtype" implementation.  It honestly seems pretty painless, even though this is a widely used type -- the only change for users is that the field names are now `val` and `property` rather than `to_fun` and `cont_mdiff_to_fun`.

The motivation is to make it possible to make certain constructions about function spaces generic, so that work for the space of smooth functions can be reused for (for example) the spaces of continuous or differentiable functions.

Notably, in #19146 we introduce a generic construction of a sheaf of functions on a manifold whose object over the open set `U` is the subtype of functions satisfying a "local invariant property".  With this PR, when that construction is applied to the property "smoothness", the resulting sheaf has objects which are *by definition* the types `cont_mdiff_map`.   They then inherit algebraic structures for free, see #19094.
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LGTM

bors d+

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✌️ hrmacbeth can now approve this pull request. To approve and merge a pull request, simply reply with bors r+. More detailed instructions are available here.

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hrmacbeth and others added 2 commits June 20, 2023 14:43
Co-authored-by: Floris van Doorn <fpvdoorn@gmail.com>
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bors r+

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bors bot pushed a commit that referenced this pull request Jun 20, 2023
…`local_invariant_prop` (#19146)

Define `structure_groupoid.local_invariant_prop.sheaf`, the sheaf-of-types of functions `f : M → M'` (for charted spaces `M`, `M'`) satisfying some local property in the sense of `structure_groupoid.local_invariant_prop` (for example continuity, differentiability, smoothness).
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@bors bors bot changed the title feat(geometry/manifold/sheaf/basic): sheaf of functions satisfying a local_invariant_prop [Merged by Bors] - feat(geometry/manifold/sheaf/basic): sheaf of functions satisfying a local_invariant_prop Jun 20, 2023
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In leanprover-community/mathlib#19146, we defined `StructureGroupoid.LocalInvariantProp.sheaf`, the sheaf-of-types of functions `f : M → M'` (for charted spaces `M`, `M'`) satisfying some local property in the sense of `StructureGroupoid.LocalInvariantProp` (for example continuity, differentiability, smoothness).

In this PR, in the case of smoothness, we upgrade this to a sheaf of groups if `M'` is a Lie group, a sheaf of abelian groups if `M'` is an abelian Lie group, and a sheaf of rings if `M'` is a "smooth ring".

Co-authored-by: Adam Topaz <github@adamtopaz.com>



Co-authored-by: Floris van Doorn <fpvdoorn@gmail.com>
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