Two examples concerning almost continuous functions
Abstract
We construct, under the assumption that union of less than continuum many meager subsets of R is meager in R, an additive connectivity function f:R-->R with Cantor intermediate value property which is not almost continuous. This gives a partial answer to a question of D. Banaszewski. We also show that every extendable function g:R-->R with a dense graph satisfies the following stronger version of the SCIVP property: for every a<b and every perfect set K between g(a) and g(b) there is a perfect subset C of (a,b) such that g[C] subset K and g|C is continuous strictly increasing. This property is used to construct a ZFC example of an additive almost continuous function f:R-->R which has the strong Cantor intermediate value property but is not extendable. This answers a question of H. Rosen. This also generalizes Rosen's result that a similar (but not additive) function exists under the assumption of the continuum hypothesis.
Keywords
Cite
@article{arxiv.math/9811011,
title = {Two examples concerning almost continuous functions},
author = {Krzysztof Ciesielski and Andrzej Roslanowski},
journal= {arXiv preprint arXiv:math/9811011},
year = {2013}
}
Comments
22 pages