Either-Or Topology is Lindelöf

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Let $T = \struct {S, \tau}$ be the either-or space.

Then $T$ is a Lindelöf space.

Proof 1

We have:

Either-Or Topology is Compact
Compact Space is Lindelöf

Hence the result.


Proof 2

Any open cover $\CC$ of $T$ must contain an open set of $T$ which contains $0$.

So $\openint {-1} 1$ will always be covered by one set in $\CC$, leaving just $-1$ and $1$ possibly needing to be included in at most two other sets.

So $\CC$ has a subcover containing at most three sets.

Hence $T$ is a Lindelöf space by definition.