Entropic Idempotent Structure is Self-Distributive

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Theorem

Let $\struct {S, \odot}$ be an algebraic structure such that $\odot$ is both idempotent and entropic.


Then $\struct {S, \odot}$ is a self-distributive structure.


Proof

\(\ds \forall a, b, c \in S: \, \) \(\ds \paren {a \odot b} \odot \paren {a \odot c}\) \(=\) \(\ds \paren {a \odot a} \odot \paren {b \odot c}\) Definition of Entropic Operation
\(\ds \) \(=\) \(\ds a \odot \paren {b \odot c}\) Definition of Idempotent Operation

and:

\(\ds \forall a, b, c \in S: \, \) \(\ds \paren {a \odot c} \odot \paren {b \odot c}\) \(=\) \(\ds \paren {a \odot b} \odot \paren {c \odot c}\) Definition of Entropic Operation
\(\ds \) \(=\) \(\ds \paren {a \odot b} \odot c\) Definition of Idempotent Operation

Hence the result by definition of self-distributive structure.

$\blacksquare$


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