English

Two examples concerning almost continuous functions

Classical Analysis and ODEs 2013-01-04 v1 Logic

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}
}

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22 pages