# Tagged Questions

Scattering is a general term for several physical processes in which radiation of some sort changes direction due to an interaction with a particle. Scattering can be classified by the type of radiation (ie, electromagnetic, x-ray, neutron), or by the relative sizes of the wave and the particle (ie, ...

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### Convergence of light by light scattering amplitude

Perhaps I'm too exhausted to see the answer of why the photon-photon scattering should contain no divergences. In Peskin and Schroeder page 320 we find that because of the Ward identity the photon-...
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### How to correctly calculate the colour of the sky?

It is well-known that the sky is blue due to Rayleigh-scattering. What bothers me though is the question how to actually calculate the spectrum of the scattered sunlight. Yes, use one of the ...
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### The two point fluctuation autocorrelation function in computing the scattering intensity?

In this paper: http://www.pnas.org/content/113/8/2029.full.pdf?with-ds=yes and: http://www.pnas.org/content/113/8/2029.full.pdf The authors try to compute the scattering intensity for a simulation ...
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### Can someone please give some references on scattering in Proca theory?

Can someone please give some references on scattering in Proca theory? I am looking for scattering calculations with massive photons.
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### Decoherence: What is the spectral density of a bath of gaseous particles?

I am studying the decoherence theory of a two-level system in interaction with a background gas. Caldira and Leggett (1987) showed that any environment can be modeled by a bath of harmonic oscillators....
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### Eikonal approximation in QFT

Does the eikonal approximation for calculating a scattering amplitude in QFT provide the exact result in the limit of $s\rightarrow\infty$ at finite $t=0$ ($s$ and $t$ are the usual Mandelstam ...
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### Do electronic energy levels of an atom effectively shift for scattering processes if the atom is moving in the lab frame?

When an electron of low energy scatters off an atom it interacts with one of the electrons in its shell and can transfer energy to it. The energy transfers would be discrete, since the shell electron ...
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### R-matrix and S-matrix in QFT

In the study of quantum field theory, one may encounter S-matrix a lot. Recently, in the study of integrability, I encountered R-matrix formulation which I am not familiar with. First of all, the S-...
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### S-matrix in Weinberg QFT

I'm a bit confused by Weinberg's discussion of scattering. He defined the in and out states $|\Psi^{\pm}_\alpha\rangle$ with particle content $\alpha$ as states that transform under the Poincare group ...
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### What is the mathematical motivation for complexifying momenta in BCFW?

One of the first steps in obtaining the on-shell BCFW recursion relations is complexifying the momenta of the external particles. Now complexifying things is not unprecedented (the dispersion program ...
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### Questions from Srednicki's Introduction to Interacting Field Theory using the LSZ Formula

I have been reading through the chapter on the LSZ Reduction Formula from Srednicki's Quantum Field Theory, and I have a few questions about which I'm sort of confused. The questions are referenced ...
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### Could the sky on a planet theoretically be any color?

The sky on the Earth is blue. Could the color of the sky on a planet with an atmosphere be of any color theoretically? Which colors are the most likely? I think it would be really awesome to have ...
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### Plasmonic nanoparticle scatering efficient differences

Dears, I got a question for you. I am thinking which nanoparticle shape, nanorods or nanospheres, will have a higher light scattering efficiency, that is without considering the light absorbance due ...