P-adic Numbers is Hausdorff Topological Space/Proof 2
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Theorem
Let $p$ be a prime number.
Let $\struct {\Q_p, \norm {\,\cdot\,}_p}$ be the $p$-adic numbers.
Let $\tau_p$ be the topology induced by the non-Archimedean norm $\norm {\,\cdot\,}_p$.
Then the topological space $\struct{\Q_p, \tau_p}$ is Hausdorff.
Proof
Let $x, y \in \Q_p$ such that $x \ne y$.
By Non-Archimedean Norm Axiom $\text N 1$: Positive Definiteness:
- $r := \norm {x - y}_p > 0$
Then, for all $z\in\Q_p$ we have:
\(\ds \max\set {\norm {x - z}_p, \norm {z - y}_p}\) | \(\ge\) | \(\ds \norm {(x-z) + (z-y)} _p\) | Non-Archimedean Norm Axiom $\text N 4$: Ultrametric Inequality | |||||||||||
\(\ds \) | \(=\) | \(\ds \norm {x - y} _p\) | ||||||||||||
\(\ds \) | \(=\) | \(\ds r\) |
Therefore, the $r$-open balls $\map {B_r} x$ and $\map {B_r} y$ are disjoint.
$\blacksquare$