Definition 7.11 (Support, totally supported, capital).

  • (a)
    By the support of an object A in a regular category, we mean the image of A1. We say A is well-supported if A1 is a cover.
  • (b)
    We say a regular category C is totally supported if every object is well-supported. We say C is almost totally supported if every object is either well-supported or a strict initial object, where we cann an object 0 strict if every A0 is an isomorphism. (Given finite limits, a strict object is initial since for any A there exists 0π10×Aπ2A, and the equaliser of any pair 0A is a).
  • (c)
    We say a regular category C is capital if its terminal object 1 is a detector, i.e. C(1,) reflects isomorphisms.