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The Mardesic factorization theorem for extension theory and c-separation
Authors:Michael Levin   Leonard R. Rubin   Philip J. Schapiro
Affiliation:Department of Mathematics, Tulane University, New Orleans, Louisiana 70118 ; Department of Mathematics, The University of Oklahoma, 601 Elm Avenue, Room 423, Norman, Oklahoma 73019 ; Department of Mathematics, Langston University, Langston, Oklahoma 73050
Abstract:
We shall prove a type of Mardesic factorization theorem for extension theory over an arbitrary stratum of CW-complexes in the class of arbitrary compact Hausdorff spaces. Our result provides that the space through which the factorization occurs will have the same strong countability property (e.g., strong countable dimension) as the original one had. Taking into consideration the class of compact Hausdorff spaces, this result extends all previous ones of its type. Our factorization theorem will simultaneously include factorization for weak infinite-dimensionality and for Property C, that is, for C-spaces.

A corollary to our result will be that for any weight $alpha $and any finitely homotopy dominated CW-complex $K$, there exists a Hausdorff compactum $X$ with weight $wXleq alpha $ and which is universal for the property $Xtau K$ and weight $leq alpha $. The condition $Xtau K$ means that for every closed subset $A$ of $X$ and every map $f:Arightarrow K$, there exists a map $F:Xrightarrow K$which is an extension of $f$. The universality means that for every compact Hausdorff space $Y$ whose weight is $leq alpha $ and for which $Ytau K$ is true, there is an embedding of $Y$ into $X$.

We shall show, on the other hand, that there exists a CW-complex $S$ which is not finitely homotopy dominated but which has the property that for each weight $alpha $, there exists a Hausdorff compactum which is universal for the property $Xtau S$ and weight $leq alpha $.

Keywords:Cohomological dimension   covering dimension   extension theory   inverse sequences   inverse systems   inverse limits   compactification   Mardev{s}i'{c} factorization   weight   universal compactum   homotopy domination   C-space   weak infinite-dimension   strong countable-dimension
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