Abstract

For a set M of graphs the category CatM of all M-complete categories and all strictly M-continuous functors is known to be monadic over Cat. The question of monadicity of CatM over the category of graphs is known to have an affirmative answer when M specifies either (i) all finite limits, or (ii) all finite products, or (iii) equalizers and terminal objects, or (iv) just terminal objects. We prove that, conversely, these four cases are (essentially) the only cases of monadicity of CatM over the category of graphs, provided that M is a set of finite graphs containing the empty graph.

Citations