(Lack of) Model Structures on the Category of Graphs

Abstract

In this article, we study model structures on the category of finite graphs with $\times$-homotopy equivalences as the weak equivalences. We show that there does not exist an analogue of Str\o{}m-Hurewicz model structure on this category of graphs. More interestingly, we show that this category of graphs with $\times$-homotopy equivalences does not have a model structure whenever the class of cofibrations is a subclass of graph inclusions.