Functions with connected graphs and $B_1$-retracts

O. Karlova

doi:10.15330/cmp.6.2.256-259

Functions with connected graphs and $B_1$-retracts

Authors

O. Karlova Yuriy Fedkovych Chernivtsi National University, 2 Kotsjubynskyi str., 58012, Chernivtsi, Ukraine https://orcid.org/0000-0002-8285-7133

https://doi.org/10.15330/cmp.6.2.256-259

Keywords:

$B_1$-retract, $H_1$-retract, Baire-one function, function with arcwise connected graph

Published online: 2014-12-26

Abstract

A subset $E$ of a topological space $X$ is called a $B_1$-retract if there exists a mapping $r:X\to E$ which is the pointwise limit of a sequence of continuous mappings $r_n:X\to E$ and $r(x)=x$ for all $x\in E$. We prove that if $Y$ is a union of an increasing sequence of continuums, then the graph of a function $f:\mathbb R\to Y$ is a $B_1$-retract of $\mathbb R\times Y$ if and only if $f$ is continuous.