Definition:Ring of Idempotents

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Let $\struct {R, +, \circ}$ be a commutative ring.

Let $A$ be the set of all idempotent elements of $R$ under $\circ$:

$A = \set {x \in R: x \circ x = x}$

Define a binary operation $\circ$ on $A$ by:

$\forall x, y \in A: x \oplus y := x + y - 2 x \circ y$

Denote also with $\circ$ the restriction of $\circ$ to $A$.

The algebraic structure $\struct {A, \oplus, \circ}$ is called the ring of idempotents of $R$.

It is an idempotent ring, as shown on Ring of Idempotents is Idempotent Ring.