group theory

# Contents

## Definition

The centralizer subgroup of a subset $S$ in a group $G$ is the set $C_G(S)$ of all elements $c\in G$ such that $c s=s c$ for all $s\in S$.

Notice the similarity but difference to the concept of normalizer subgroup.

The centralizer is the largest subgroup $H$ of $G$ containing $S$ such that $S$ is in the center of $H$. The centralizer of a subset is clearly a subgroup of its normalizer, as fixing the set $g H=H g$ is a weaker requirement than $g h=h g$ for all $h\in H$.

Revised on December 11, 2015 04:49:12 by Urs Schreiber (78.104.9.204)