nLab commutator (changes)

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Contents

Definition

In rings and algebras

For AA a ring or associative algebra, the commutator of two elements x,y∈Ax,y \in A is the element

[x,y]≔xy−yx. [x,y] \coloneqq x y - y x \,.

In groups

For GG a group, the group commutator of two elements a,b∈Ga,b \in G is the element

[a,b]≔a −1b −1ab. [a,b] \coloneqq a^{-1} b^{-1} a b \,.

Properties

References

On commutators in operator algebra:

  • Calvin R. Putnam, Commutation Properties of Hilbert Space Operators and Related Topics, Ergebnisse der Mathematik und ihrer Grenzgebiete 36, Springer (1967) [[doi:10.1007/978-3-642-85938-0](https://doi.org/10.1007/978-3-642-85938-0)]

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