All Questions
5
questions
1
vote
1
answer
108
views
Why is the Vacuum state got by a limit to imaginary time?
Given a (non-relativistic) propagator $K_t(A,B)$ giving the 'conditional amplitude' to go from state $B$ to state $A$ in time $t$, it is known that one can find the vacuum wavfunction by (independent ...
user84158
5
votes
2
answers
482
views
About sending time to infinity in a slightly imaginary direction in QFT
I am going through the Peskin and Schroeder QFT book. While proving the Gell-Mann and Low theorem in chapter 4 of their book, the authors started with the equation
\begin{equation}
e^{-iHT}|0\rangle = ...
- 2,038
7
votes
1
answer
206
views
Choice of folliation in path integral
Assume we have a scalar field theory for a field $\phi$. Can we think of the Hilbert space as being spanned by states of the form $|\varphi\rangle$ for configurations $\varphi\in C^\infty(\mathbb{R}^3)...
- 3,915
21
votes
1
answer
1k
views
LSZ reduction vs adiabatic hypothesis in perturbative calculation of interacting fields
As far as I know, there are two ways of constructing the computational rules in perturbative field theory.
The first one (in Mandl and Shaw's QFT book) is to pretend in and out states as free states, ...
- 6,401
9
votes
2
answers
2k
views
Imaginary time in QFT
I'm reading chapter 4 of Introduction to Quantum Field Theory by Peskin & Schroeder. In the $\phi^4$ theory, the authors state that the ground state of the interaction theory $|\Omega\rangle$ can ...
- 2,897