Ageing without detailed balance in the bosonic contact and pair-contact   processes: exact results
  Ageing in systems without detailed balance is studied in the exactly solvable bosonic contact process and the critical bosonic pair-contact process. The two-time correlation function and the two-time response function are explicitly found. In the ageing regime, the dynamical scaling of these is analyzed and exact results for the ageing exponents and the scaling functions are derived. For the critical bosonic pair-contact process the autocorrelation and autoresponse exponents agree but the ageing exponents $a$ and $b$ are shown to be distinct. 
Florian Baumann, Malte Henkel, Michel Pleimling, Jean Richert