nLab
Span

Span

Span

Definition

SpanSpan is the bicategory, or double category, whose

  • objects are sets
  • (horizontal) morphisms are spans
  • 2-cells are morphisms of spans
  • (in the double category case) vertical morphisms are functions.

More generally, we have Span(C)Span(C) consists of spans in CC for any category CC with pullbacks.

Properties

SpanSpan is a sort of classifying object for arbitrary functors; see displayed category.

Categorifications

There is an (infinity,n)-category of correspondences.

Last revised on May 12, 2017 at 05:58:56. See the history of this page for a list of all contributions to it.