Supersymmetric objects in the M-theory on a pp-wave
  We obtain, in a systematic way, all the classical BPS equations which correspond to the quantum BPS states in the M-theory on a fully supersymmetric pp-wave. The superalgebra of the M-theory matrix model shows that the BPS states always preserve pairs of supersymmetry, implying the possible fractions of the unbroken supersymmetry as 2/16, 4/16, 6/16,.... We study their classical counterparts, and find there are essentially one unique set of 2/16 BPS equations, three inequivalent types of 4/16 BPS equations, and three inequivalent types of 8/16 BPS equations only, in addition to the 16/16 static fuzzy sphere. We discuss various supersymmetric objects as solutions. In particular, when the fuzzy sphere rotates, the supersymmetry is further broken as 16/16 -> 8/16 -> 4/16. 
Jeong-Hyuck Park