I am reading chapter three of Huang's Statistical Mechanics and I have a problem with equation (3.22). Having discussed the derivation of the classical cross section for a scattering process, Huang moves on to the quantum version of it. He states that in quantum mechanics the fundamental quantity in a scattering process is the matrix T, that represents an operator T(E):(adsbygoogle = window.adsbygoogle || []).push({});

[tex]T=<1',2'|T(E)|1,2>[/tex]

where [itex]|1,2>[/itex] is the initial state ket of the system of two particles and the primed ket is the final state ket. He also writes:

[tex]T(E)=H'+H'(E-H_0+i\epsilon)^{-1}H'+\dots[/tex]

where H_0 is the unperturbed hamiltonian, H' the potential and epsilon goes to zero. I don't understand what he means by that. Can you explain what I am missing or give me some reference? Up to now, the first two chapters were really good and I enjoyed them, but given that I have only a basic knowledge of non-relativistic quantum mechanics (one dimensional problems, bra-ket notation and not much more), do you think is it useful to go on reading this book?

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# Cross section computation - Huang's Statistical Mechanics

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