Pii: S0040-9383(98)00034-2
نویسنده
چکیده
The choice of a closed regular neighborhood of a finite polyhedron embedded in a manifold enables one to write the ambient space as a union of two manifolds, the neighborhood and its complement, glued along a common boundary component. Poincaré duality embeddings are a homotopy theoretic version of this in which the manifolds are replaced by Poincaré spaces and the gluing is now done with respect to a homotopy equivalence. To put it another way, a map f : KPX from a finite complex K into an n-dimensional Poincaré duality space X (or Poincaré pair (X, LX)) is said to Poincare& embed if f extends to a homotopy equivalence
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Pii: S0040-9383(98)00044-5
Novikov [25] generalized this to multiple-valued functions, i.e. closed 1-forms. In the simplest version of Novikov’s construction, we consider a circle-valued Morse function / :XPS1. There is an analogue of the Morse complex which counts gradient flow lines of /. In this circle-valued case, to obtain a finite count we need to classify flow lines using some information about their homotopy clas...
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We have obtained further insights into the CBD growth mechanisms of ZnS thin ®lms using an aqueous medium containing an ammonium salt. At room temperature the optimum concentration of this salt has enabled us to increase the thickness of the ®lm by more than 400%. The optical transmission below the band edge of our best ®lm is also found to be excellent. q 1999 Elsevier Science S.A. All rights ...
متن کاملPii: S0040-9383(98)00039-1
In this paper we extend several results about classical knot invariants derived from the infinite cyclic cover to the twisted case. Let X be a finite complex with fundamental group n, let o :nPG ̧(») be a linear representation where » is a finite dimensional vector space over a field F, and let e : nPZ be a homomorphism. Finally let X = be the infinite cyclic cover of X corresponding to e. The r...
متن کاملPii: S0040-4020(00)00678-5
The diazo group of a series of a-diazo carbonyl compounds can be reduced to the corresponding CH2 group by Bu3SnH under Cu(acac)2-catalytic or photochemical conditions. The mechanistic aspects of this reaction were investigated in some detail, and a possible reaction pathway was discussed. q 2000 Elsevier Science Ltd. All rights reserved.
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