Let $L$ be a compact open subgroup of locally compact abelian group $G$. Is $nL=\{nx;x\in L\}$ an open subgroup of $G$?
2026-04-01 06:30:22.1775025022
Compact open subgroup of a locally compact abelian group
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It seems that the answer is negative. For instance, $G=L=\mathbb Z_2^\omega$ is a compact group, but the set $2L=\{e\}$ is not open in $G$.