Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
4658378 | Topology and its Applications | 2015 | 8 Pages |
Abstract
Let X be a topological space and (Y,≤)(Y,≤) a linearly ordered topological space. Following the Katětov–Tong Insertion Theorem, a pair (X,Y)(X,Y) is said to have the insertion property if for every upper semicontinuous map g:X→Yg:X→Y and every lower semicontinuous map h:X→Yh:X→Y with g(x)≤h(x)g(x)≤h(x) for all x∈Xx∈X, there exists a continuous map f:X→Yf:X→Y such that g(x)≤f(x)≤h(x)g(x)≤f(x)≤h(x) for all x∈Xx∈X. We show that if (X,Y)(X,Y) has the insertion property for every normal space X, then Y is order isomorphic to some interval in the real line. We also prove that if X is a paracompact space or a cardinal and L is the double edged long line, then (X,L)(X,L) has the insertion property.
Related Topics
Physical Sciences and Engineering
Mathematics
Geometry and Topology
Authors
S. García-Ferreira, Y.F. Ortiz-Castillo, T. Yamauchi,