# Questions tagged [propagator]

propagator gives the probability amplitude for a particle to travel from one place to another in a given time, or to travel with a certain energy and momentum.

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### Scattering Greens function exactly at energy of bound state

I have a small bit of confusion about the expansion I am seeing in literature for the Greens function in time independent scattering theory. For example here is an excerpt from Scattering Theory of ...
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### Why commutator of positive and negative parts of scalar field is equal to the Feynman propagator?

Peskin & Schroeder state that the contraction of two fields, defined as the commutator: $$[\phi^+(x),\phi^-(y)]\qquad \text{assuming}\ x^0>y^0$$ is equal to the Feynman propagator $D_F(x-y)$. ...
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### Quark propagator

I was reading about Large N QCD, and specifically, T Hooft Double line notation, when I stumbled across the quark propagator- $$\langle \psi^a (x) \overline{\psi^b}(y) \rangle = \delta^{ab} S(x-y)$$ ...
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### Propagator from a spacetime point to itself and physical interpretation of vacuum

I am following a lecture note on the QFT. But am a little confused about some parts related to the vacuum bubbles. We define the Feynman propagator, $D_{F}(x-y)$, as giving the amplitude for a ...
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### Integral of gauge field bulk to boundary propagator in AdS

I'm studying from the book "Introduction to the AdS/CFT Correspondance" by Horatiu Nastase. In page 190, he defines the gauge field bulk-to-boundary propagator in Euclidean $AdS_{d+1}$ given ...
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### Calculating the Nambu-Gorkov propagator (given its inverse) for quarks

I am working through this paper on the calculation of a Nambu-Gorkov propagator, could someone explain how did we reach the next step right after equation (16)?
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