Returning functions with closed graph are continuous
Abstract
A function defined on a topological space is called returning if for any point there exists a positive real number such that for every path-connected subset containing the point and any there exists a point such that . A topological space is called path-inductive if a subset is open if and only if for any path the preimage is open in . The class of path-inductive spaces includes all first-countable locally path-connected spaces and all sequential locally contractible space. We prove that a function defined on a path-inductive space is continuous if and only of it is returning and has closed graph. This implies that a (weakly) \'Swi\c atkowski function is continuous if and only if it has closed graph, which answers a problem of Maliszewski, inscibed to Lviv Scottish Book.
Cite
@article{arxiv.1903.01937,
title = {Returning functions with closed graph are continuous},
author = {Taras Banakh and Małgorzata Filipczak and Julia Wódka},
journal= {arXiv preprint arXiv:1903.01937},
year = {2020}
}
Comments
5 pages