Central idempotents of the bifree and left-free double Burnside ring
  We determine the blocks, i.e., the primitive central idempotents, of the bifree double Burnside ring $B^\Delta(G,G)$ and the left-free double Burnside ring $B^{\trl}(G,G)$, as well as the primitive central idempotents of the algebras arising from scalar extension to $\QQ$. 
Robert Boltje, Burkhard K\"ulshammer
math.RT math.KT math.RA