Spans of cospans in a topos

Daniel Cicala, Kenny Courser

For a topos $\mathbf{T}$, there is a bicategory $\mathbf{MonicSp}(\mathbf{Csp}(\mathbf{T}))$ whose objects are those of $\mathbf{T}$, morphisms are cospans in $\mathbf{T}$, and 2-morphisms are isomo…