Cores: Rel
The category Rel has the groupoid SymmRel as its core, or maximal subcategory which is still a groupoid. As with all cores, SymmRel is an (essentially) wide subcategory of Rel.
There is a functor from categories to groupoids:
Core : Cat → Grpd
And it sends Rel to SymmRel:
Core : Rel ↦ SymmRel
Core(Rel) ≅ SymmRel
cores: Rel
This data as json
| groupoid | category |
|---|---|
| SymmRel | Rel |