# Topological characterization of chainable sets and chainability via continuous functions

Document Type : Original Article

Authors

1 Department of Mathematics, University of Sistan and Baluchestan, Zahedan, Iran

2 Department of Mathematics, University of Sistan and Baluchestan, Zahedan, Iran.

10.22034/kjm.2020.219320.1710

Abstract

In the last decade, the notions of function-f-ϵ-chainability, uniformly function-f-ϵ-chainability, function-f-ϵ-chainable sets and locally functionf-chainable sets were studied in some papers. We show that the notions of function-f-ϵ-chainability and uniformly function-f-ϵ-chainability are equivalent to the notion of non-ultrapseudocompactness in topological spaces. Also, all of these are equivalent to the condition that each pair of non-empty subsets (resp., subsets with non-empty interiors) is function-f-ϵ-chainable (resp., locally function-f-chainable). Further, we provide a criterion for connectedness with covers. In the paper "Characterization of ϵ-chainable sets in metric spaces" (Indian J. Pure Appl. Math. 33 (2002), no. 6, 933{940), the chainability of a pair of subsets in a metric space has been defined wrongly and consequently Theorem 1 and Theorem 5 are found to be wrong. We rectify
their definition appropriately and consequently, we give appropriate results and counterexamples.

Keywords