Hello, I am a chemist and have been working on chemical dynamics. Recently I have started working on some many body interactions. Therein I have found some ideas about Fock Space, Fock Matrix, Fock Space Coherences. These are extensively used to provide characteristic information in static/dynamic/coupled systems. 1.What I want to understand is the physical basis of these terms. Although I have a fair bit of idea on its mathematical weightage, I am not able to get its physical significance. 2.Also I need to know how do You perceive the transfer of a state from a Hilbert Space to a Fock Space. 3. How do we know whether the atom/molecule/complex is in the Fock Space. 4. What factors or grounds do we consider before attempting to solve a system by taking it into the Fock Space. 5. If you can prescribe me any book where I can get a hold of these, I will be even more grateful. I've gone through lecture notes by C. Nayak, Demler, Dinsmore. But still am not clear. I would really appreciate if you help me out. A chemist shifting to Physics is really proving difficult.