Constructions of new partial homeomorphisms from old #
Main definitions #
OpenPartialHomeomorph.const: an open partial homeomorphism which is a constant map, whose source and target are necessarily singleton setsOpenPartialHomeomorph.subtypeRestr: restriction to a subtypeOpenPartialHomeomorph.prod: the product of two open partial homeomorphisms, as an open partial homeomorphism on the product spaceOpenPartialHomeomorph.pi: the product of a finite family of open partial homeomorphismsOpenPartialHomeomorph.disjointUnion: combine two open partial homeomorphisms with disjoint sources and disjoint targetsOpenPartialHomeomorph.lift_openEmbedding: extend an open partial homeomorphismX → Yunder an open embeddingX → X', to an open partial homeomorphismX' → Z. (This is used to define the disjoint union of charted spaces.)
This is PartialEquiv.single as an open partial homeomorphism: a constant map,
whose source and target are necessarily singleton sets.
Equations
- OpenPartialHomeomorph.const ha hb = { toPartialEquiv := PartialEquiv.single a b, open_source := ha, open_target := hb, continuousOn_toFun := ⋯, continuousOn_invFun := ⋯ }
Instances For
Products #
Product of two open partial homeomorphisms
The product of two open partial homeomorphisms, as an open partial homeomorphism on the product space.
Equations
Instances For
Pi types #
Finite indexed products of partial homeomorphisms
The product of a finite family of OpenPartialHomeomorphs.
Equations
- OpenPartialHomeomorph.pi ei = { toPartialEquiv := PartialEquiv.pi fun (i : ι) => (ei i).toPartialEquiv, open_source := ⋯, open_target := ⋯, continuousOn_toFun := ⋯, continuousOn_invFun := ⋯ }
Instances For
Disjoint union #
Combining two partial homeomorphisms using Set.piecewise
Combine two OpenPartialHomeomorphs using Set.piecewise. The source of the new
OpenPartialHomeomorph is s.ite e.source e'.source = e.source ∩ s ∪ e'.source \ s, and similarly
for target. The function sends e.source ∩ s to e.target ∩ t using e and
e'.source \ s to e'.target \ t using e', and similarly for the inverse function.
To ensure the maps toFun and invFun are inverse of each other on the new source and target,
the definition assumes that the sets s and t are related both by e.is_image and e'.is_image.
To ensure that the new maps are continuous on source/target, it also assumes that e.source and
e'.source meet frontier s on the same set and e x = e' x on this intersection.
Equations
Instances For
Combine two OpenPartialHomeomorphs with disjoint sources and disjoint targets. We reuse
OpenPartialHomeomorph.piecewise then override toPartialEquiv to PartialEquiv.disjointUnion.
This way we have better definitional equalities for source and target.
Equations
- e.disjointUnion e' Hs Ht = (e.piecewise e' e.source e.target ⋯ ⋯ ⋯ ⋯).replaceEquiv (e.disjointUnion e'.toPartialEquiv Hs Ht) ⋯
Instances For
Postcompose an open partial homeomorphism with a homeomorphism. We modify the source and target to have better definitional behavior.
Equations
- e.transHomeomorph f' = { toPartialEquiv := e.transEquiv f'.toEquiv, open_source := ⋯, open_target := ⋯, continuousOn_toFun := ⋯, continuousOn_invFun := ⋯ }
Instances For
Restriction to a subtype #
subtypeRestr: restriction to a subtype
The restriction of an open partial homeomorphism e to an open subset s of the domain type
produces an open partial homeomorphism whose domain is the subtype s.
Equations
- e.subtypeRestr hs = (s.openPartialHomeomorphSubtypeCoe hs).trans e
Instances For
This lemma characterizes the transition functions of an open subset in terms of the transition functions of the original space.
Extending along an open embedding #
Extend an open partial homeomorphism e : X → Z to X' → Z, using an open embedding
ι : X → X'. On ι(X), the extension is specified by e; its value elsewhere is arbitrary
(and uninteresting).
Equations
- One or more equations did not get rendered due to their size.