The Caccetta-Haggkvist conjecture January 30 to February 3, 2006 AIM Research Conference Center, Palo Alto, CA Organizers: Maria Chudnovsky, Matt Devos, Paul Seymour, and Robin Thomas Workshop topics: This workshop, sponsored by AIM and the NSF, will focus on the Caccetta-Haggkvist conjecture, which in its simplest form asserts the following: If G is an n-vertex directed graph with minimum outdegree at least n/k, then G has a directed cycle of length at most k. This has a number of variants and strengthenings, and in particular it has numerous connections with additive number theory. The workshop aims to clarify and develop these variants, and to bring together people working on different aspects of the conjecture in the hope of finding a solution. Application deadline: October 30, 2005 For more information: http://aimath.org/ARCC/workshops/caccetta.html