Contents

# Contents

## Definition

A Kan fibration that at the same time is a weak homotopy equivalence is called an acyclic Kan fibration. (Also: a trivial Kan fibration.)

## Properties

Acyclic Kan fibrations are the acyclic fibrations in the classical model structure on simplicial sets $sSet_{Qu}$, hence those morphisms which have the right lifting property against monomorphisms (degreewise injections) of simplicial sets.

###### Remark

In particular, this implies that acyclic Kan fibrations are always (in particular: degreewise) surjective in that they have right lifting against any empty bundle $\varnothing \xhookrightarrow{\;} S$ (as opposed to plain Kan fibrations, see this remark).

In fact:

###### Proposition

Acyclic Kan fibrations are precisely the morphisms of simplicial sets that have the right lifting property against all simplex boundary inclusions.

See this Prop. at classical model structure on simplicial sets. This is part of the statement that $sSet_{Qu}$ is a cofibrantly generated (see this Prop.).

Last revised on October 11, 2021 at 05:56:14. See the history of this page for a list of all contributions to it.