I understand that Quantum Numbers must be preserved during particle interactions, which prevents certain interactions from occurring.
However, as Energy and Momentum must also be conserved, are there any particle interactions which are prevented by the none-conservation of these properties?
Specifically, can an interaction be prevented in general, as oppose to in a specific circumstance.
Yes. Any interaction that violates either energy or momentum conservation is forbidden. Obviously there is an infinite number of such impossible interactions... like, the spontaneous emission of a photon by a nucleus that already is in its ground state; the absorption of a photon by a free electron; the decay of a electron and a anti-electron-neutrino into a muon and a anti-muon neutrino when the kinetic energies are low, etc. pp.
