Homology, Homotopy and Applications
Volume 1 (1999)
Higher homotopy groupoids and Toda brackets
Pages: 117 – 134
We describe a category htTop whose objects are pointed continuous maps and whose morphisms are generated under composition by the tracks (relative homotopy classes) of homotopies. For example, if $m_t:hk \to *$ is a nullhomotopy then its track is a morphism from $k$ to $h$. The composition of tracks in htTop amounts to a sharpening of the classical secondary composition operation (Toda bracket). Standard properties of the Toda bracket can be derived in this setting. Moreover we show that htTop is itself the homotopy category of a bicategory htTop and so admits also a secondary composition operation.
Toda bracket, bicategory, track, double category, $2$-groupoid, 2-track, Hopf invariant
2010 Mathematics Subject Classification