Definition:P-adic Valuation/P-adic Numbers/Definition 1

Definition
Let $p$ be a prime number.

Let $\struct {\Q_p, \norm {\,\cdot\,}_p}$ be the $p$-adic numbers.

The $p$-adic valuation on $p$-adic numbers is the function $\nu_p: \Q_p \to \Z \cup \set {+\infty}$ defined by:
 * $\forall x \in \Q_p : \map {\nu_p} x = \begin {cases}

-\log_p \norm x_p : x \ne 0 \\ +\infty : x = 0 \end{cases}$

Also see

 * P-adic Valuation Extends to P-adic Numbers where it is shown that $\nu_p$ is a valuation that extends the $p$-adic valuation on the rational numbers $\Q$ to $\Q_p$.