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$\frak T$ need not be a topology, so I replaced it by the topology generated by $\frak T$.
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Is the topology generated by the union of a chain of paracompact topologies paracompact?

Let $X$ be a set and let ${\frak T}$ be a collection of paracompact topologies on $X$ such that for any $\tau, \tau'\in {\frak T}$ we have $\tau\subseteq \tau'$ or $\tau'\subseteq \tau$. It is easy to see thatLet $\sigma$ be the topology having $\bigcup {\frak T}$ isas a topologybase.

Is $(X,\bigcup {\frak T})$$(X,\sigma)$ necessarily paracompact?

EDIT. Thanks to Tomek Kania for observing that $\bigcup {\frak T}$ need not be a topology.

Is the union of a chain of paracompact topologies paracompact?

Let $X$ be a set and let ${\frak T}$ be a collection of paracompact topologies on $X$ such that for any $\tau, \tau'\in {\frak T}$ we have $\tau\subseteq \tau'$ or $\tau'\subseteq \tau$. It is easy to see that $\bigcup {\frak T}$ is a topology.

Is $(X,\bigcup {\frak T})$ necessarily paracompact?

Is the topology generated by the union of a chain of paracompact topologies paracompact?

Let $X$ be a set and let ${\frak T}$ be a collection of paracompact topologies on $X$ such that for any $\tau, \tau'\in {\frak T}$ we have $\tau\subseteq \tau'$ or $\tau'\subseteq \tau$. Let $\sigma$ be the topology having $\bigcup {\frak T}$ as a base.

Is $(X,\sigma)$ necessarily paracompact?

EDIT. Thanks to Tomek Kania for observing that $\bigcup {\frak T}$ need not be a topology.

Source Link

Is the union of a chain of paracompact topologies paracompact?

Let $X$ be a set and let ${\frak T}$ be a collection of paracompact topologies on $X$ such that for any $\tau, \tau'\in {\frak T}$ we have $\tau\subseteq \tau'$ or $\tau'\subseteq \tau$. It is easy to see that $\bigcup {\frak T}$ is a topology.

Is $(X,\bigcup {\frak T})$ necessarily paracompact?