Higher order Toda brackets

Abstract

We describe two ways to define higher order Toda brackets in a pointed simplicial model category $${\mathcal {D}}$$ : one is a recursive definition using model categorical constructions, and the second uses the associated simplicial enrichment. We show that these two definitions agree, by providing a third, diagrammatic, description of the Toda bracket, and explain how it serves as the obstruction to rectifying a certain homotopy-commutative diagram in $${\mathcal {D}}$$ .