Definition:Involution (Mapping)
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Definition
Let $A$ be a set.
Let $f: A \to A$ be a mapping on $A$.
Definition 1
$f$ is an involution if and only if:
- $\forall x \in A: \map f {\map f x} = x$
That is:
- $f \circ f = I_A$
where $I_A$ denotes the identity mapping on $A$.
Definition 2
$f$ is an involution if and only if:
- $\forall x, y \in A: \map f x = y \implies \map f y = x$
Definition 3
$f$ is an involution if and only if $f$ is both a bijection and a symmetric relation.
That is, if and only if $f$ is a bijection such that:
- $f = f^{-1}$
Also known as
An involution is also known as an involutive mapping or an involutive function.
An involutive mapping can also be found described as self-inverse.
Also see
- Results about involutions can be found here.
Sources
- 2014: Christopher Clapham and James Nicholson: The Concise Oxford Dictionary of Mathematics (5th ed.) ... (previous) ... (next): involution