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Separation Axioms Weaker Than T1

2020

Abstract

The purpose of this paper is to introduce a new type of separation axioms via dense sets, called DTi-spaces (i = 0‚ 1 4 ‚ 1 3 ‚ 1 2 ‚ 3 4 ‚1), where a DTi-space is a topological space which contains a dense Tisubspace (i = 0‚ 1 4 ‚ 1 3 ‚ 1 2 ‚ 3 4 ‚1). These new axioms are weaker than the axiom of T1. We provide the basic properties of DTispaces (i = 0‚ 1 4 ‚ 1 3 ‚ 1 2 ‚ 3 4 ‚1), and we show that the axioms of DT1 4 , DT1 3 , DT1 2 , DT3 4 , DT1 are open hereditary. Moreover, we study the connections between these axioms and the axioms of Ti where (i = 0‚ 1 4 ‚ 1 3 ‚ 1 2 ‚ 3 4 ‚1).