# PlanetPhysics/Borel Morphism

Let $\displaystyle \grp_B$ and $\displaystyle \grp_B$ * be two groupoids whose object spaces are Borel. An \htmladdnormallink{algebraic {http://planetphysics.us/encyclopedia/CoIntersections.html} morphism} from $\displaystyle \grp_B$ to $\displaystyle \grp_B$ * is defined as a left action of $\displaystyle \grp_B$ on $\displaystyle \grp_B$ * which commutes with the multiplication on $\displaystyle \grp_B$ . Such an algebraic morphism between Borel groupoids is said to be a Borel morphism if the action of $\displaystyle \grp_B$ on $\displaystyle \grp_B$ * is Borel (viz. ref. [1])

[1]

## References

1. M.R. Buneci. 2006., Groupoid C*-Algebras., Surveys in Mathematics and its Applications , Volume 1: 71--98.