Initial Topology on Hausdorff Locally Convex Space is Weak Topology
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Theorem
Let $\GF \in \set {\R, \C}$.
Let $\struct {X, \PP}$ be a Hausdorff locally convex space over $\GF$.
Let $X^\ast$ be the topological dual space of $X$.
Let $w$ be the initial topology on $X$ with respect to $X^\ast$.
Then $w$ is the weak topology on $X$.
Proof
From Topological Dual Space of Hausdorff Locally Convex Space Separates Points, if $x \ne y$ then there exists $f \in X^\ast$ such that $\map f x \ne \map f y$.
That is, if $x \ne \mathbf 0_X$, there exists $f \in X^\ast$ such that $\map f x \ne 0$.
$\blacksquare$