nLab acyclic Kan fibration



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Basic facts




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


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


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

In fact:


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 QusSet_{Qu} is a cofibrantly generated (see this Prop.).

Last revised on July 21, 2022 at 15:42:47. See the history of this page for a list of all contributions to it.