The Ghost length, levels and shriek maps on classifying spaces
  We give a lower bound of the cochain type level of the diagonal map on the classifying space of a Lie group by using the ghostness of a shriek map. Moreover, in a derived category, we discuss the triviality of the shriek map which induces the loop product on the classifying space of a Lie group. 
Katsuhiko Kuribayashi
math.AT math.RA math.RT