Smooth isotopies through embeddings #
A SmoothIsotopy f₀ f₁ is a jointly C^n map on unitInterval × M from f₀ to
f₁ whose time slices are smooth embeddings. The endpoints are arbitrary bundled
smooth maps; existence of an isotopy forces them to be embeddings.
The time interval carries Mathlib's manifold-with-boundary structure. Forgetting
smoothness produces the existing continuous TauCeti.Isotopy, with exactly the
same time slices. Constant isotopies, smooth changes of time, and time reversal
are provided here, as is the isotopy SmoothIsotopy.ofContDiff given by a C^n map on
ℝ × E between normed spaces. Smooth concatenation is provided in SmoothIsotopy.Trans;
isotopy extension is a separate result.
This slice-wise convention does not impose properness on a noncompact source. Ambient isotopy remains the relation used for knot equivalence; a smooth isotopy is the input to an isotopy extension theorem, rather than an assertion that such an extension exists.
References #
- M. Hirsch, Differential Topology, Springer GTM 33 (1976), Chapter 8, §8.1.
The continuous forgetful construction follows Mathlib's ContinuousMap.HomotopyWith
and Tau Ceti's Isotopy.
A jointly C^n homotopy through smooth embeddings, with prescribed endpoints.
The source and target may have boundary or corners.
- toContMDiffMap : ContMDiffMap ((modelWithCornersEuclideanHalfSpace 1).prod I) J (↑unitInterval × M) N n
The motion, smooth in both time and the source variable.
The motion starts at
f₀.The motion ends at
f₁.- isSmoothEmbedding (t : ↑unitInterval) : Manifold.IsSmoothEmbedding I J n fun (x : M) => self.toContMDiffMap (t, x)
Every time slice is a smooth embedding.
Instances For
Evaluate a smooth isotopy at a time and a source point.
The underlying smooth map evaluates to the motion.
The motion starts at its initial endpoint.
The motion ends at its final endpoint.
Two smooth isotopies agree when their motions agree pointwise.
A smooth isotopy is jointly smooth in time and space.
The time-t slice, bundled as a smooth embedding.
Instances For
Evaluating a time slice is evaluating the isotopy at that time.
The initial endpoint of a smooth isotopy is a smooth embedding.
The final endpoint of a smooth isotopy is a smooth embedding.
Forgetting smoothness gives a continuous isotopy through embeddings.
Instances For
Forgetting smoothness preserves the motion.
Smooth isotopy implies the existing continuous isotopy relation.
The constant smooth isotopy at a smooth embedding.
Instances For
A constant isotopy keeps its source points stationary.
Change time by a smooth map of the unit interval fixing its endpoints. The time map need not be injective or monotone.
Instances For
A time change evaluates the original isotopy at the new time.
Reverse a smooth isotopy in time.
Instances For
Time reversal evaluates the original isotopy at 1 - t.
Reversing time twice recovers the original smooth isotopy.
The smooth isotopy given by a C^n map G on ℝ × E, read on [0, 1] × E, which starts at
f₀, ends at f₁, and whose time slices over [0, 1] are smooth embeddings.
Instances For
The isotopy given by a C^n map on ℝ × E evaluates to that map.
Two bundled smooth maps are smoothly isotopic when a jointly smooth homotopy through smooth embeddings connects them. This does not assert ambient isotopy.
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Smooth isotopy is witnessed by a smooth isotopy through embeddings.
A smooth embedding is smoothly isotopic to itself.
Smooth isotopy is symmetric.
Smoothly isotopic maps are isotopic after forgetting smoothness.