The gravity-related decoherence master equation from hybrid dynamics
  Canonical coupling between classical and quantum systems cannot result in reversible equations, rather it leads to irreversible master equations. Coupling of quantized non-relativistic matter to gravity is illustrated by a simplistic example. The heuristic derivation yields the theory of gravity-related decoherence proposed longtime ago by Penrose and the author. 
Lajos Di\'osi
quant-ph gr-qc