- #1
taishizhiqiu
- 63
- 4
Regarding interacting green's function, I found two different description:
1. usually in QFT:
[itex]<\Omega|T\{ABC\}|\Omega>=\lim\limits_{T \to \infty(1-i\epsilon)}\frac{<0|T\{A_IB_I U(-T,T)\}|0>}{<0|T\{U(-T,T)\}|0>}[/itex]
2. usually in quantum many body systems:
[itex]<\Omega|T\{ABC\}|\Omega>=\frac{<0|T\{A_IB_I S\}|0>}{<0|T\{S\}|0>}[/itex]
where interaction is switched off at ##T=\pm\infty## (adiabatic approximation)
Is there any connection between the two descriptions?
1. usually in QFT:
[itex]<\Omega|T\{ABC\}|\Omega>=\lim\limits_{T \to \infty(1-i\epsilon)}\frac{<0|T\{A_IB_I U(-T,T)\}|0>}{<0|T\{U(-T,T)\}|0>}[/itex]
2. usually in quantum many body systems:
[itex]<\Omega|T\{ABC\}|\Omega>=\frac{<0|T\{A_IB_I S\}|0>}{<0|T\{S\}|0>}[/itex]
where interaction is switched off at ##T=\pm\infty## (adiabatic approximation)
Is there any connection between the two descriptions?