The permutation groupoid, sometimes denoted , is a skeleton of the groupoid of finite sets and bijections. Namely:
where objects are natural numbers, all morphisms are automorphisms, and the automorphism group of the object is the symmetric group .
In other words, is equivalent to the core of FinSet.
There are many notations for besides ‘’, such as and . In The Joy of Cats, is denoted .
Revised on July 9, 2010 01:22:17
by Toby Bartels