Inverse of Unit in Centralizer of Ring is in Centralizer
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Theorem
Let $\struct {R, +, \circ}$ be a ring.
Let $S$ be a subset of $R$.
Let $\map {C_R} S$ denote the centralizer of $S$ in $R$
Let $u \in R$ be a unit of $R$.
Then:
- $u \in \map {C_R} S \implies u^{-1} \in \map {C_R} S$
Proof
Let $u \in R$ be a unit of $R$.
Let $u \in \map {C_R} S$.
Then from Commutation with Inverse in Monoid:
- $u^{-1} \in \map {C_R} S$
$\blacksquare$
Sources
- 1965: Seth Warner: Modern Algebra ... (previous) ... (next): Chapter $\text {IV}$: Rings and Fields: $21$. Rings and Integral Domains: Theorem $21.5$