- #1
wiser
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- 0
Hello everyone:(Please forgive my poor English.)
I've been learning many-body theory for a year or so, however, I'm quite confused with different Green's functions (GF) there. One of the most things I want to get clear is about zero-temperature GF and imaginary-time GF (or Matsubara GF), both of which are time ordered.
I learned that one of the most physically interesting GF is retarded GF and all that we need to do is try to calculate it. In Mahan's book I got to know that through analytic continuation of imaginary-time GF we will get retarded GF. This is what I know.
My confusion is that if we could get retarded GF from zero-temperature GF or simply use real-time formalism if we only want to know about the ground state? Summations over Matsubara frequencies are really annoying. But I don't know how to relate the zero-temperature GF to retarded GF?
I wonder if it is possible that we begin by calculating real-time GF (time ordered) and through some transformations we get retarded GF? Or the only way to get retarded GF is to use imaginary-time GF and then analytic continuation, besides EOM and NEGF?
Looking forward to your reply! Thank you very much!
yours sincerely wiser
I've been learning many-body theory for a year or so, however, I'm quite confused with different Green's functions (GF) there. One of the most things I want to get clear is about zero-temperature GF and imaginary-time GF (or Matsubara GF), both of which are time ordered.
I learned that one of the most physically interesting GF is retarded GF and all that we need to do is try to calculate it. In Mahan's book I got to know that through analytic continuation of imaginary-time GF we will get retarded GF. This is what I know.
My confusion is that if we could get retarded GF from zero-temperature GF or simply use real-time formalism if we only want to know about the ground state? Summations over Matsubara frequencies are really annoying. But I don't know how to relate the zero-temperature GF to retarded GF?
I wonder if it is possible that we begin by calculating real-time GF (time ordered) and through some transformations we get retarded GF? Or the only way to get retarded GF is to use imaginary-time GF and then analytic continuation, besides EOM and NEGF?
Looking forward to your reply! Thank you very much!
yours sincerely wiser