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monoid [2015/03/28 20:17] nikolaj |
monoid [2015/04/12 17:48] nikolaj |
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| @#FFBB00: definiendum | @#FFBB00: $ \langle\!\langle M,*\rangle\!\rangle \in$ it | | | @#FFBB00: definiendum | @#FFBB00: $ \langle\!\langle M,*\rangle\!\rangle \in$ it | | ||
| @#AAFFAA: inclusion | @#AAFFAA: $*$ ... binary operation | | | @#AAFFAA: inclusion | @#AAFFAA: $*$ ... binary operation | | ||
+ | | @#FFFDDD: exists | @#FFFDDD: $e$ | | ||
+ | | @#55EE55: postulate | @#55EE55: $e$ ... unit element $\langle\!\langle M,*\rangle\!\rangle$ | | ||
| @#55EE55: postulate | @#55EE55: $(a*b)*c=a*(b*c)$ | | | @#55EE55: postulate | @#55EE55: $(a*b)*c=a*(b*c)$ | | ||
- | | @#FFFDDD: exists | @#FFFDDD: $e\in M$ | | ||
- | | @#FFFDDD: for all | @#FFFDDD: $a\in M$ | | ||
- | | @#55EE55: postulate | @#55EE55: $a*e=e*a=a$ | | ||
----- | ----- | ||
=== Discussion === | === Discussion === | ||
- | The binary operation is often called //multiplication// and $e$ is called the identity, identity element or unit. | + | The binary operation is often called //multiplication// and $e$ is called the //identity//, //identity element// or //unit//. |
- | One generally calls $M$ the monoid, i.e. the set where the operation "$*$" is defined on. | + | One generally calls $M$ the monoid, i.e. the set where the operation "$*$" is defined on, not the pair. For example, not that "A monoid is non-empty". |
+ | |||
+ | Like above, one often uses infix notion for $*$. | ||
=== Reference === | === Reference === | ||
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----- | ----- | ||
+ | === Requirements === | ||
+ | [[Unit element]] | ||
=== Subset of === | === Subset of === | ||
[[Semigroup]] | [[Semigroup]] |