Let K be a CW-complex. A map f : X โ Y of compacta X and Y is said to be of e-dim K if e-dim f -1 (y) K for every y โ Y . We prove that if e-dim f K then there exists a ฯ -compact subset A of X such that e-dim A K and f | X\A is 0-dimensional. This result is an analogue for extensional dimension of
โฆ LIBER โฆ
Light maps and extensional dimension
โ Scribed by A.N. Dranishnikov; V.V. Uspenskij
- Book ID
- 104295175
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 640 KB
- Volume
- 80
- Category
- Article
- ISSN
- 0166-8641
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โฆ Synopsis
We show that any light map f : X + Y between compact spaces admits a decomposition f = gh, where g : 2 + Y is a finite-to-one map of a special type and h : X + 2 has arbitrarily small fibers. It follows that light maps between compact spaces do not lower extensional dimension. Our theorem yields a positive answer to Problem 423 from "Open Problems in Topology". We also generalize Hurewicz' theorem on dimension-raising maps to the case of extensional dimension.
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