A necessary condition for embedding a complex in
A new invariant and parametric connected sum of embeddings
We define an isotopy invariant of embeddings of manifolds into Euclidean space. This invariant together with the α-invariant of Haefliger-Wu is complete in the dimension range where the α-invariant could be incomplete. We also define parametric connected sum of certain embeddings (analogous to surgery). This allows us to obtain new completeness results for the α-invariant and the following estimation of isotopy classes of embeddings. In the piecewise-linear category, for a (3n-2m+2)-connected...
Algebraic models of Poincaré embeddings.
An unknotting theorem for tori in 4-dimensional spheres.
Let T be a torus in S4 and T* a projection of T. If the singular set Gamma(T*) consists of one disjoint simple closed curve, then T can be moved to the standard position by an ambient isotopy of S4.
...-Applications dans une variété
Cobordisme d'immersions
Complexes Whose Boundaries Cannot Be Pushed Around.
Cubulations, immersions, mappability and a problem of Habegger
Embedding, compression and fiberwise homotopy theory.
Embedding Finite Covering Spaces into Trivial Bundles.
Embedding products of graphs into Euclidean spaces
For any collection of graphs we find the minimal dimension d such that the product is embeddable into (see Theorem 1 below). In particular, we prove that (K₅)ⁿ and are not embeddable into , where K₅ and are the Kuratowski graphs. This is a solution of a problem of Menger from 1929. The idea of the proof is a reduction to a problem from so-called Ramsey link theory: we show that any embedding , where O is a vertex of (K₅)ⁿ, has a pair of linked (n-1)-spheres.
Embedding proper homotopy types
We show that the proper homotopy type of any properly c-connected locally finite n-dimensional CW-complex is represented by a closed polyhedron in (Theorem I). The case n - c ≥ 3 is a special case of a general proper homotopy embedding theorem (Theorem II). For n - c ≤ 2 we need some basic properties of “proper” algebraic topology which are summarized in Appendices A and B. The results of this paper are the proper analogues of classical results by Stallings [17] and Wall [20] for finite CW-complexes;...
Embeddings and imnmersions of branched covering spaces.
Eta invariants and complex immersions
Fundamental Groups, ...-groups and Codimension two Submanifolds
Hardness of embedding simplicial complexes in
Let be the following algorithmic problem: Given a finite simplicial complex of dimension at most , does there exist a (piecewise linear) embedding of into ? Known results easily imply polynomiality of (; the case is graph planarity) and of for all . We show that the celebrated result of Novikov on the algorithmic unsolvability of recognizing the 5-sphere implies that and are undecidable for each . Our main result is NP-hardness of and, more generally, of for all , with...
Heegaard splittings of Seifert fibered spaces.
Heegaard splittings of (surface) x I are standars.
Knot and link projections in 3-manifolds.
La courbure totale absolue minimale des surfaces dans