Parametric connected sum
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− | Parametric connected sum is an operation on compact connected n-manifolds $M$ and $N$ equipped with codimension 0-embeddings $\phi: T \to M$ and $\psi : T \to N$ of a compact connected manifold $T$. It generalises the usual connected sum operation | + | Parametric connected sum is an operation on compact connected n-manifolds $M$ and $N$ equipped with codimension 0-embeddings $\phi: T \to M$ and $\psi : T \to N$ of a compact connected manifold $T$. It generalises the usual [[Connected sum|connected sum]] operation |
− | + | which is the special case when $T = D^n$ is the $n$-disc. | |
− | + | The parametric connected sum operation is more complicated than the usual connected | |
− | + | sum operation since the isotopy classes of the embeddings of $T$ into $M$ may be significantly more complicated than the isotopy classes of embeddings of n-discs need for connected sum: these last are determined by (local) orientations. | |
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Revision as of 18:06, 19 February 2013
This page has not been refereed. The information given here might be incomplete or provisional. |
Contents |
1 Introduction
Tex syntax errorand equipped with codimension 0-embeddings and of a compact connected manifold . It generalises the usual connected sum operation which is the special case when is the
Tex syntax error-disc.
The parametric connected sum operation is more complicated than the usual connected
sum operation since the isotopy classes of the embeddings of intoTex syntax errormay be significantly more complicated than the isotopy classes of embeddings of n-discs need for connected sum: these last are determined by (local) orientations.
2 Connected sum along k-spheres
Tex syntax errorand it is sufficient to equip them with an isotopy class of embeddings of the k-disc. Moreover, the disjoint union is the unique thickening of . This motivates the following
Defintion 2.1.
A manifold with an -thickening, an -thickened manifold for short, is a pair whereTex syntax erroris a compact connected manifold and is an embedding.
Defintion 2.2. Let and by -thickened manifolds. Define
where is defined via the embeddings and .
It is clear that we have the following
Observation 2.3.
The diffeomorphism type of depends only upon the the isotopy classes of the embeddings and (which of course includes the diffeomorphism types ofTex syntax errorand ).
2.1 Applications
The operation of -connected sum was used in [Ajala1984] and [Ajala1987] to describe the set of smooth structures on the product of spheres . This construction also appears in [Sako1981]. The analogue of such a construction for embeddings is used in [Skopenkov2006] to define, for , a group stucture on the set of (smooth or PL) isotopy classes of embeddings of into . In [Skopenkov2007] and [Skopenkov2010] the -connected sum of embeddings was used to estimate the set of embeddings.
3 Parametric connected sum along thickenings
Let be a stable fibred vector bundle. A foundational theorem of modified surgery is
In particular, has the structure of an abelian group. The question of whether there is a geometric definition of this group structure is taken up in [Kreck1985, Chapter 2, pp 26-7] where it is shown how to use parametric connected sum along thickenings to define an addition of stable diffeomorphism classes of closed 2n-B-manifolds.
4 References
- [Ajala1984] S. O. Ajala, Differentiable structures on products of spheres, Houston J. Math. 10 (1984), no.1, 1–14. MR736571 (85c:57032) Zbl 0547.57026
- [Ajala1987] S. O. Ajala, Differentiable structures on a generalized product of spheres, Internat. J. Math. Math. Sci. 10 (1987), no.2, 217–226. MR886378 (88j:57028) Zbl 0627.57022
- [Kreck1985] M. Kreck, An extension of the results of Browder, Novikov and Wall about surgery on compact manifolds, preprint Mainz (1985).
- [Kreck1999] M. Kreck, Surgery and duality, Ann. of Math. (2) 149 (1999), no.3, 707–754. MR1709301 (2001a:57051) Zbl 0935.57039
- [Sako1981] Y. Sako, Connected sum along the cycle operation of on -manifolds, Proc. Japan Acad. Ser. A Math. Sci. 57 (1981), no.10, 499–502. MR640259 (83a:57043) Zbl 0505.57010
- [Skopenkov2006] A. Skopenkov, Embedding and knotting of manifolds in Euclidean spaces, in: Surveys in Contemporary Mathematics, Ed. N. Young and Y. Choi, London Math. Soc. Lect. Notes, 347 (2008) 248-342. Available at the arXiv:0604045.
- [Skopenkov2007] A. Skopenkov, A new invariant and parametric connected sum of embeddings, Fund. Math. 197 (2007), 253–269. arXiv:math/0509621. MR2365891 (2008k:57044) Zbl 1145.57019
- [Skopenkov2010] A. Skopenkov, Embeddings of k-connected n-manifolds into , Proc. AMS, 138 (2010) 3377--3389. Available at the arXiv:0812.0263.