## Doctoral Dissertations

## Date of Award

8-1998

## Degree Type

Dissertation

## Degree Name

Doctor of Philosophy

## Major

Mathematics

## Major Professor

Robert J. Daverman

## Committee Members

Klaus Johannson, Morwen B. Thistlethwaite, Jerzy Dydak, Kenneth C. Gilbert

## Abstract

An extensive variety of closed n-manifolds N, called codimension-2 (orientable) fibrators, automatically induce approximate fibrations, in the sense that all proper maps ƒ: M → B from any (respectively, orientable) (n + 2)-manifold M to a metric space B (equivalently, to a 2-manifold B) such that each f^{-1}(b) has the same homotopy type (or, more generally, the same shape) as N are approximate fibrations. R.J. Daverman showed that closed hopfian manifolds with hopfian fundamental group and nonzero Euler characteristic, as well as closed hopfian manifolds with hyperhopfian fundamental group are codimension-2 orientable fibrators. Using the concept of s-hopfianness, we generalize Daverman's results about codimension-2 orientable fibra tors to the orientation-free version as follows:

Closed s-hopfian manifolds with either hyperhopfian fundamental group or hopfian fundamental group and nonzero Euler characteristic are codimension-2 fibrators.

In the second part of this dissertation, we study the behavior of codimension-2 fibrators under the connected sum operation. As a consequence, we will get the neat result on closed 4—manifolds as follows;

Given a closed 4—manifold N which is a nontrivial connected sum of two 4—manifolds N_{1} and N_{2}, where π_{1}(N_{1} and π_{1}(N_{2}) are hopfian, then N is a codimension-2 fibrator if and only if N is not homotopy equivalent to RP^{4}#RP^{4}. In the next section we determine which closed n-manifolds (n ≤ 4) with geometric structure are codimension-2 fibrators. In closing, we mention some unsettled topics.

## Recommended Citation

Kim, Yongkuk, "Codimension two submanifold decompositions that induce approximate fibrations. " PhD diss., University of Tennessee, 1998.

https://trace.tennessee.edu/utk_graddiss/9292