\title[Colocalizing subcategories and cosupport] {Colocalizing subcategories and cosupport} \author{Dave Benson} \address{Dave Benson \\ Institute of Mathematics\\ University of Aberdeen\\ King's College\\ Aberdeen AB24 3UE\\ Scotland U.K.} \author{Srikanth B. Iyengar} \address{Srikanth B. Iyengar\\ Department of Mathematics\\ University of Nebraska\\ Lincoln, NE 68588\\ U.S.A.} \author{Henning Krause} \address{Henning Krause\\ Fakult\"at f\"ur Mathematik\\ Universit\"at Bielefeld\\ 33501 Bielefeld\\ Germany.} \begin{document} \begin{abstract} The Hom closed colocalizing subcategories of the stable module category of a finite group are classified. Along the way, the colocalizing subcategories of the homotopy category of injectives over an exterior algebra, and the derived category of a formal commutative differential graded algebra, are classified. To this end, and with an eye towards future applications, a notion of local homology and cosupport for triangulated categories is developed, building on earlier work of the authors on local cohomology and support. \end{abstract} \keywords{colocalizing subcategory, cosupport, local homology, localizing subcategory, stable module category, triangulated category} \subjclass[2010]{20J06(primary); 13D45, 16E45, 18E30} \thanks{The research of the first and second authors was undertaken during visits to the University of Paderborn, each supported by a research prize from the Humboldt Foundation. The research of the second author was also partly supported by NSF grant DMS 0903493.}