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A proper injective immersion is an embedding
Statement
A proper injective immersion between smooth manifolds is a smooth embedding; this general criterion is choice-free. Assume for the following high-codimension consequences. If is a proper self-transverse immersion with , then is a smooth embedding; if in addition is closed, self-transversality with alone suffices, properness being automatic.
Facts & Assumptions
Given: The published criterion for proper injective immersions, and (for the stated consequences) countable choice and a self-transverse immersion with .
A proper injective immersion between smooth manifolds is a smooth embedding (A proper injective immersion is a smooth embedding).
A smooth embedding is an injective immersion that is a homeomorphism onto its image with the subspace topology (Smooth embeddings); the phrase is therefore exactly what [F1] concludes for such a map (Immersions, submersions, and constant-rank maps).
A self-transverse immersion with has empty double point locus and is injective (A self-transverse immersion has no double points when ).
A closed subset of a compact space is compact (A closed subspace of a compact space is compact, and a finite union of compact subspaces is compact).
A smooth map of smooth manifolds is continuous (Smooth maps are continuous).
A subset is compact when it is compact as a subspace in its own right (Open cover, subcover, and compact topological space; a compact subset is a subspace that is compact in its own right); a smooth manifold is in particular a Hausdorff topological manifold (Smooth manifolds and their smooth charts).
Countable choice is the hypothesis of [L1] and is inherited by the second and third sentences of the statement; the first sentence and the properness computation select nothing (The Axiom of Countable Choice ()).
Proof
The general criterion of [F1] is the published proposition cited in [F2]; its conclusion is precisely that a proper injective immersion satisfies the three clauses of [F2] and hence is a smooth embedding.
Suppose is closed, that is, compact without boundary. Every compact subset is closed by [L2], since a smooth manifold is Hausdorff by [L5]; the preimage is closed in because is continuous by [L4], and a closed subset of the compact space is compact by [L3]. Hence preimages of compact sets under are compact, that is, is proper.
Assume and let be a proper self-transverse immersion with . By [L1] the map is injective, and is an immersion and proper by hypothesis, so step 1.1 makes a smooth embedding.
With now proper by step 1.2, injective by [L1] and an immersion by hypothesis, step 1.1 applies and shows that a self-transverse immersion with and closed is a smooth embedding, with no separate properness hypothesis.
The three assertions of the statement are step 1.1, step 2.1 and step 3.1 respectively.
Depends on
- A proper injective immersion is a smooth embedding
- A self-transverse immersion has no double points when $n>2m$
- Smooth embeddings
- Immersions, submersions, and constant-rank maps
- The Axiom of Countable Choice ($\mathrm{AC}_\omega$)
- Open cover, subcover, and compact topological space; a compact subset is a subspace that is compact in its own right
- Smooth manifolds and their smooth charts
- Smooth maps are continuous
- In a Hausdorff space a point and a disjoint compact set, and two disjoint compact sets, have disjoint open neighbourhoods; hence every compact subset is closed, and in a compact Hausdorff space the compact subsets are exactly the closed ones
- A closed subspace of a compact space is compact, and a finite union of compact subspaces is compact
Used by
Nothing in the library uses this result yet.
Dependency tree · two levels
38 results within two dependency steps of this one, each drawn at its shortest distance from it. An arrow runs from a result to what uses it, so the chart reads left to right and ends at this result, which carries a heavier outline. Every node is a link to that result. Click elsewhere on the chart to enlarge it.
Sources
- C. T. C. Wall, Differential Topology (Cambridge Studies in Advanced Mathematics 156, Cambridge University Press 2016; full text retrieved from the Internet Archive Wayback Machine snapshot of the ETH Zürich course copy), Chapter 6 §§6.2–6.4, printed pp. 169–192 (Theorem 6.2.1; Propositions 6.3.1 and 6.3.3; Theorems 6.3.2, 6.3.4, 6.3.6, 6.4.5, 6.4.8 and 6.4.9; Lemma 6.3.5) (standard reference, not scraped)
- Arkadiy Skopenkov, Embedding and Knotting of Manifolds in Euclidean Spaces (arXiv:math/0604045), §1, article pp. 2–5 (self-intersection set; ambient versus non-ambient isotopy) and §2, article pp. 6–14 (Theorems 2.1–2.3 and 2.8; the modulo 2 and integral Whitney obstruction; the Whitney invariant); §3 and §5 used only for the recorded knotting boundary (standard reference, not scraped)
- Morris W. Hirsch, Differential Topology (Graduate Texts in Mathematics 33, Springer 1976; full text retrieved from the Internet Archive Wayback Machine snapshot of the luis.impa.br course copy), Chapter 8 “Isotopy”, §1, printed pp. 177–183 (Theorems 1.1–1.8 and Exercises 3, 7, 9, 10, 11, 16, printed pp. 182–184) (standard reference, not scraped)