For every algebra $A$, the center $Z(A)$ is a congruence on $A$. Why is $Z(A)$ an equivalence relation on $A$?
Why $Z(A)$ is an equivalence relation on $A$?
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universal-algebra
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1I don't understand. If "congruence" means what I think it means then I don't know what you mean when you say that a subset of $A$ (as opposed to a subset of $A \times A$) is a congruence. – 2012-12-18