TY - JOUR
T1 - A 2-categorical approach to change of base and geometric morphisms II
AU - Carboni, A.
AU - Kelly, G. M.
AU - Verity, D.
AU - Wood, R. J.
PY - 1998
Y1 - 1998
N2 - We introduce a notion of equipment which generalizes the earlier notion of pro-arrow equipment and includes such familiar constructs as $\rel\K$, $\spn\K$, $\par\K$, and $\pro\K$ for a suitable category $ \K$, along with related constructs such as the $\V$-$\pro$ arising from a suitable monoidal category $\V $. We further exhibit the equipments as the objects of a 2-category, in such a way that arbitrary functors $F:\eL -> \K$ induce equipment arrows $\rel F:\rel\eL ->\rel\K$, $\spn F:\spn\eL -> \spn\K$, and so on, and similarly for arbitrary monoidal functors $\V -> \W$. The article I with the title above dealt with those equipments $\M$ having each $\M(A,B)$ only an ordered set, and contained a detailed analysis of the case $\M =\rel\K$; in the present article we allow the $\M(A,B)$ to be general categories, and illustrate our results by a detailed study of the case $\M=\spn\K$. We show in particular that $\spn$ is a locally-fully-faithful 2-functor to the 2-category of equipments, and determine its image on arrows. After analyzing the nature of adjunctions in the 2-category of equipments, we are able to give a simple characterization of those $\spn G$ which arise from a geometric morphism $G$.
AB - We introduce a notion of equipment which generalizes the earlier notion of pro-arrow equipment and includes such familiar constructs as $\rel\K$, $\spn\K$, $\par\K$, and $\pro\K$ for a suitable category $ \K$, along with related constructs such as the $\V$-$\pro$ arising from a suitable monoidal category $\V $. We further exhibit the equipments as the objects of a 2-category, in such a way that arbitrary functors $F:\eL -> \K$ induce equipment arrows $\rel F:\rel\eL ->\rel\K$, $\spn F:\spn\eL -> \spn\K$, and so on, and similarly for arbitrary monoidal functors $\V -> \W$. The article I with the title above dealt with those equipments $\M$ having each $\M(A,B)$ only an ordered set, and contained a detailed analysis of the case $\M =\rel\K$; in the present article we allow the $\M(A,B)$ to be general categories, and illustrate our results by a detailed study of the case $\M=\spn\K$. We show in particular that $\spn$ is a locally-fully-faithful 2-functor to the 2-category of equipments, and determine its image on arrows. After analyzing the nature of adjunctions in the 2-category of equipments, we are able to give a simple characterization of those $\spn G$ which arise from a geometric morphism $G$.
KW - Adjunction
KW - Equipment
KW - Span
UR - http://www.scopus.com/inward/record.url?scp=54549127952&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:54549127952
SN - 1201-561X
VL - 4
SP - 82
EP - 136
JO - Theory and Applications of Categories
JF - Theory and Applications of Categories
ER -