Definition:Fort Space

Definition
Let $S$ be an infinite set.

Let $p \in S$ be a particular point of $S$.

Let $\tau_p \subseteq \powerset S$ be a subset of the power set of $S$ defined as:
 * $\tau_p = \leftset {U \subseteq S: p \in \relcomp S U} \cup \set {U \subseteq S: \relcomp S U}$ is finite$\rightset{}$

That is, $\tau_p$ is the set of all subsets of $S$ whose complement in $S$ either contains $p$ or is finite.

Then $\tau_p$ is a Fort topology on $S$, and the topological space $T = \struct {S, \tau_p}$ is a Fort space.

Also see

 * Fort Topology is Topology


 * Definition:Modified Fort Space
 * Definition:Fortissimo Space