nLab localization of a monoid




Monoid theory



The concept of localization of a monoid, the localization of a category with a single object. Could be generalized to localization of monoid objects in a cartesian monoidal category CC. The localization of a ring is a localization of a monoid object in Ab.


For commutative monoids

Let (M,1,*)(M,1,*) be a commutative monoid object in SetSet and let SS be a commutative submonoid of MM. Then the localization of MM away from SS, S 1MS^{-1}M, is the set of equivalences on M×SM \times S, (m 1,s 1)(m 2,s 2)(m_1,s_1) \sim (m_2,s_2) such that there is an element u:Su:S where m 1s 2u=m 2s 1um_1 \cdot s_2 \cdot u = m_2 \cdot s_1 \cdot u.

Write ms 1m s^{-1} for the equivalence class of (m,s)(m,s). On this set, the product is defined by

(m 1s 1 1)(m 2s 2 1)(m 1m 2)(s 1s 2) 1. (m_1 s_1^{-1}) \cdot (m_2 s_2^{-1}) \coloneqq (m_1 \cdot m_2) (s_1 \cdot s_2)^{-1} \,.

For non-commutative monoids

Analogue of noncommutative localization for noncommutative monoid objects in SetSet instead of AbAb.

Group completion

The group completion of a commutative monoid MM is the localization of MM away from MM.

Last revised on December 27, 2023 at 15:17:39. See the history of this page for a list of all contributions to it.