Transposing cartesian and other structure in double categories
The cartesian structure possessed by morphisms like relations, spans, and profunctors is elegantly expressed by universal properties in double categories. Though cartesian double categories were inspired in part by the older program of cartesian bicategories, the precise relationship between the double-categorical and bicategorical approaches has so far remained mysterious, except in special cases. We provide a formal connection by showing that every double category with iso-strong finite produ…