Compact Complement Topology is T1

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Theorem

Let $T = \struct {S, \tau}$ be a compact complement space.


Then $T$ is a $T_1$ (Fréchet) space.


Proof

We have that a Finite Topological Space is Compact.

So any finite subspace of $T$ is compact.

Let $\tau^*$ be the set defined as:

$\tau^* = \leftset {S \subseteq \R: S = \O \text { or } \relcomp \R S}$ is finite $\rightset {}$

where $\relcomp \R S$ denotes the complement of $S$ in $\R$.

Then $\tau^*$ is a subset of $\tau$ by definition of the compact complement topology.

But $\tau^*$ is the finite complement topology.

The result follows from Finite Complement Topology is Minimal $T_1$ Topology.

$\blacksquare$


Sources