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3 questions
5votes
1answer
286views
How does one rigorously define two-point functions?
Let $\mathscr{H}$ be a complex Hilbert space, and $\mathcal{F}^{\pm}(\mathscr{H})$ be its associated bosonic (+) and fermionic (-) Fock spaces. Given $f \in \mathscr{H}$, we can define rigorously the ...
- 1,283
2votes
1answer
462views
The relation between full Green's function and S-matrix
I'm learning Green's function in condensed matter. The full Green's function is defined as $$G(k_2,t_2;k_1,t_1) = \langle\Omega |T a_{k_1}(t_1)a_{k_2}^{\dagger}(t_2) |\Omega \rangle $$ The $\Omega$ is ...
- 189
0votes
1answer
401views
What's the meaning of the propagator in QM?
Yesterday I was solving some exercises, and after solving the time evolution I was asked to find the probability of the system to some state. In specific: $$|\Psi(t)\rangle = \frac{1}{\sqrt{2}}\left(|...
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