-adic topology
Let be a ring and an ideal in such that
Though not usually explicitly done, we can define a metric on by defining for a by where is the largest integer such that (well-defined by the intersection assumption, and is taken to be the entire ring) and by , and then defining for any ,
The topology induced by this metric is called the -adic topology. Note that the number 2 was chosen rather arbitrarily. Any other real number greater than 1 will induce an equivalent topology.
Except in the case of the similarly-defined -adic topology, it is rare that reference is made to the actual -adic metric. Instead, we usually refer to the -adic topology.
In particular, a sequence of elements in is Cauchy with respect to this topology if for any there exists an such that for all we have . (Note the parallel with the metric version of Cauchy, where plays the part analogous to an arbitrary ). The ring is complete with respect to the -adic topology if every such Cauchy sequence converges to an element of .
Title | -adic topology |
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Canonical name | IadicTopology |
Date of creation | 2013-03-22 14:36:59 |
Last modified on | 2013-03-22 14:36:59 |
Owner | mathcam (2727) |
Last modified by | mathcam (2727) |
Numerical id | 7 |
Author | mathcam (2727) |
Entry type | Definition |
Classification | msc 13B35 |
Synonym | I-adic topology |