Definition:Overlapping Interval Topology

Definition
Let $S = \closedint {-1} 1$ denote the open real interval:
 * $\closedint {-1} 1 = \set {x \in \R: -1 \le x \le 1}$

Let $\BB$ be the set:
 * $\BB = \set {\hointl a 1: -1 < a < 0} \cup \set {\hointr {-1} b: 0 < b < 1}$

where:
 * $\hointl a 1$ is the half-open interval $\set {x \in \R: a < x \le 1}$.
 * $\hointr {-1} b$ is the half-open interval $\set {x \in \R: -1 \le x < b}$.

Then $\BB$ is the basis for a topology $\tau$ on $\R$.

Thus the sets of the form $\openint a b$ such that $a < 0 < b$ are open sets in $S$.

$\tau$ is referred to as the overlapping interval topology.

The topological space $T = \struct {S, \tau}$ is referred to as the overlapping interval space.

Also see

 * Overlapping Interval Topology is Topology


 * Existence of Topological Space which satisfies no Separation Axioms but $T_0$