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How does one modify the decay width of a particle (QFT/Thermal Field theory style) when a particle is travelling through matter

I believe a particle's decay width/rate should depend on whether they are in matter or vacuum, but am unsure of where to find a prescription describing this phenomena. Please could someone point me in ...
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436 views

What are thermal photons?

What is the difference between an ordinary photon and a thermal photon? Do thermal photons act as an exchange particle for any forces similar to an ordinary photon which acts as an exchange particle ...
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Physical understanding of the change in scattering cross-sections at finite temperatures

I am familiar with the computation of scattering cross-sections in zero temperature quantum field theory. How does a scattering cross-section typically behave at temperature $T$? Let the cross-...
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189 views

What is the meaning of thermal spectral function and thermal decay width in thermal field theory?

In Kallen-Lehmann spectral representation of 2-point correlation function \begin{equation} \langle 0|T\phi(x)\phi(0)|0\rangle=\int_0^\infty \frac{dM^2}{2\pi}\rho(M^2)D_F(x-y;M^2),\quad (a) \end{...