All Questions
Tagged with quantum-field-theory wick-rotation
156
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Peskin and Schroeder Page no. 95 Feynman Diagrams
From Peskin and Schroeder Page no. 95,
... First, what happened to the large time $T$ that was taken to $\infty(1- i\epsilon)$? We glossed overit completely in this section, starting with Eq. (4.43). ...
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What is the physical difference between the Euclidean and the Lorentzian path integral?
This is a specific example of the broader question of why should physics change with metric signature basically.
Based on a talk by Daniel Harlow, I am generally wondering what exactly makes the ...
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Complex time theories with spacetime $\mathbb{R}^3\times\mathbb{C}$
Are there any well-developed (string?..) theories assuming that, what we perceive as a (3+1) Minkowskian manifold, is a projection/compactification of a 5-dim spacetime, locally obtained via ...
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Different versions of Schwinger parameterization
One common used trick when calculating loop integral is Schwinger parameterization. And I have seen two versions among wiki, arxiv and lecture notes.
$$\frac{1}{A}=\int_0^{\infty} \mathrm{d}t \ e^{-tA}...
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Can you perform a Wick rotation if the poles are on the imaginary axis?
I know you can perform a Wick rotation whenever the poles are outside the contour but what happens if the poles are on the imaginary axis? Can you do it anyway?
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What is the equivalent of causality in Euclidean field theory?
In Wick rotated quantum field theory where $t$ becomes $it$ and it has Euclidean metric signature. What would be the equivalent statement that events outside each others light-cones are disconnected ...
user84158
8
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2
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Lorentz vs. Euclidean invariance for hard momentum cutoff in QFT
Several accounts of QFT allege that using a hard momentum cutoff $p^2<\Lambda^2$ breaks Lorentz invariance. For instance, see Schwartz's book, p833, or Weinberg p14, or answers here. But I don't ...
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How to Wick rotate the Yang-Mills instanton winding number?
How to Wick rotate the instanton number of Yang-Mills theory?
(Related to the earlier question Wick rotate the Yang-Mills $SU(N)$ gauge theory's field strength?)
My question is particularly about ...
- 4,336
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Wick rotation from Minkowski Dirac theory to Euclidean Dirac theory: $\gamma^{0} = -i\gamma^{4}$
I am reading Path Integrals and Quantum Anomalies by Kazuo Fujikawa and Hiroshi Suzuki. In chapter 4.2 they calculate the self-energy of photon for QED and say that the actual calculation is performed ...
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How to understand the path integral of $U(1)$ gauge field under Coulomb gauge?
I want to obtain Green's function of $U(1)$ gauge field under Coulomb gauge. For some reason, I want to finish it in Euclidean space, i.e. both time-space $x_\mu$ and field strength $A_\mu$, so that ...
- 1,602
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Why can you deform the contour in the integral expression for the Klein-Gordon propagator to get the Euclidean propagator?
I'm trying to understand the use of the Euclidean correlation functions in QFT. I chased down the problems I was having to how they manifest in the simplest example I could think of: the two-point ...
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Does a partially traced density operator also become a Boltzmann density operator under Wick rotation to Euclidean space?
I know that, under the Wick rotation $(i\Delta t/\hbar,p_0)\to(-\beta,-ip_{0,E})$, Feynman's path integral supposedly transforms into the traced-over Boltzmann partition function, $trace(e^{-\beta H})=...
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In path-integral, when do we have to insert fact $i$ in front of the action $S$ in the exponent?
I have got stuck in these concepts for a fews days: Wick rotation, Euclidean spacetime and QED in gravity.
Generally, in Minkowski space time, there is a factor $i$ in front of the action $S$, e.g., ...
- 995
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How do we perform 'time' translation in Euclidean QFT?
If we have an operator in a $1+1$ dimension QFT then we get the Hamiltonian, which comes from and generates translations in the $t$ direction and a momentum operator which comes from and generates ...
- 1,933
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Analytic Continuation: Replacement of $t \rightarrow - i \tau$ Mathematical Justification [duplicate]
It's commonly used in imaginary-time path integral that "analytic continuation" means replacing $t \rightarrow - i \tau$ or reparametrizing the theory in terms of imaginary time $\tau = i t$....
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