The effective model structure and infinity-groupoid objects

Journal article, 2022

For a category E with finite limits and well-behaved countable coproducts, we construct a model structure, called the effective model structure, on the category of simplicial objects in E, generalising the Kan-Quillen model structure on simplicial sets. We then prove that the effective model structure is left and right proper and satisfies descent in the sense of Rezk. As a consequence, we obtain that the associated infinity-category has finite limits, colimits satisfying descent, and is locally Cartesian closed when E is but is not a higher topos in general. We also characterise the infinity-category presented by the effective model structure, showing that it is the full sub-category of presheaves on E spanned by Kan complexes in E, a result that suggests a close analogy with the theory of exact completions.