The **index** of an open subgroup $H$ of a profinite group $G$ is the positive integer $[G:H]$.

When $G$ is a matrix group over $\widehat \Z$ or $\Z_\ell$ and $H$ is a subgroup of level $N$, this is the same as the index of $H$ in the reduction of $G$ modulo $N$.

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- Review status: beta
- Last edited by Andrew Sutherland on 2021-09-18 14:51:25

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**History:**(expand/hide all)

- 2021-09-18 14:51:25 by Andrew Sutherland
- 2021-09-18 14:51:09 by Andrew Sutherland
- 2021-09-18 14:47:24 by Andrew Sutherland
- 2021-09-18 10:15:25 by Andrew Sutherland
- 2021-09-18 09:50:15 by Andrew Sutherland
- 2021-07-17 11:28:47 by Andrew Sutherland

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