Fourth Arolla Conference on Algebraic Topology, which took place in
Arolla, Switzerland, from August 20-25, 2012.
The papers in this volume cover topics such as category theory and homological algebra, functor homology, algebraic -theory,
cobordism categories, group theory, generalized cohomology theories
and multiplicative structures, the theory of iterated loop spaces,
Smith-Toda complexes, and topological modular forms.