P-adic metric: Difference between revisions
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Revision as of 16:57, 1 November 2008
The p -adic metric, with respect to a given prime number p, on the field Q of rational numbers is a metric which is a valuation on the field.
Definition
Every non-zero rational number may be written uniquely in the form where r and s are integers coprime to p and n is an integer. We define the p-adic valuation on Q by
The p-adic metric is then defined by
Properties
The p-adic metric on Q is not complete: the p-adic numbers are the corresponding completion.
Ostrowksi's Theorem
The p-adic metrics and the usual absolute value on Q are mutually inequivalent. Ostrowkski's theorem states that any non-trivial absolute value on the rational numbers Q is equivalent to either the usual real absolute value or a p-adic absolute value.