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On sums of Darboux and nowhere constant continuous functions
Authors:Krzysztof Ciesielski  Janusz Pawlikowski
Institution:Department of Mathematics, West Virginia University, Morgantown, West Virginia 26506-6310 ; Department of Mathematics, University of Wroclaw, pl. Grunwaldzki 2/4, 50-384 Wroclaw, Poland -- and -- Department of Mathematics, West Virginia University, Morgantown, West Virginia 26506-6310
Abstract:We show that the property
(P)
for every Darboux function $g\colon{\mathbb R}\to\mathbb{R} $ there exists a continuous nowhere constant function $f\colon{\mathbb R}\to\mathbb{R} $ such that $f+g$ is Darboux
follows from the following two propositions:
(A)
for every subset $S$ of $\mathbb{R} $ of cardinality $\mathfrak{c}$ there exists a uniformly continuous function $f\colon\mathbb{R}\to0,1]$ such that $fS]=0,1]$,
(B)
for an arbitrary function $h\colon\mathbb{R}\to\mathbb{R} $ whose image $h\mathbb{R} ]$ contains a non-trivial interval there exists an $A\subset\mathbb{R} $ of cardinality $\mathfrak{c}$ such that the restriction $h\restriction A$ of $h$ to $A$is uniformly continuous,
which hold in the iterated perfect set model.

Keywords:Darboux  nowhere constant  images of continuous functions
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