Cyril Houdayer - Université Paris-Sud (Orsay) Connes' bicentralizer problem (CBP) asks whether every type III1 factor has a trivial bicentralizer. Haagerup solved CBP for amenable type III1 factors, thus completing Connes' classification of amenable factors. CBP is known to have a positive solution in some particular cases but remains wide open for arbitrary nonamenable type III1 factors. Motivated by CBP, we investigate the structure of the (relative) bicentralizer algebra B(N⊂M) associated with an irreducible inclusion of type III1 factors N⊂M. We construct a canonical flow β:\R↷B(N⊂M) that does not depend on the choice of states and relate the ergodicity of the flow β to the existence of amenable subfactors P⊂N that are irreducible in M. This also provides new results on the structure of the bicentralizer algebra B(M) in the case N=M. When the inclusion N⊂M is discrete, we prove a relative version of Haagerup's bicentralizer theorem and use it to solve Kadison's problem when N is amenable. This is joint work with Hiroshi Ando, Uffe Haagerup and Amine Marrakchi.