Search results for "QFT"
showing 4 items of 4 documents
Spectral function of fermions in a highly occupied non-Abelian plasma
2022
We develop a method to obtain fermion spectral functions non-perturbatively in a non-Abelian gauge theory with high occupation numbers of gauge fields. After recovering the free field case, we extract the spectral function of fermions in a highly occupied non-Abelian plasma close to its non-thermal fixed point, i.e., in a self-similar regime of the non-equilibrium dynamics. We find good agreement with hard loop perturbation theory for medium-induced masses, dispersion relations and quasiparticle residues. We also extract the full momentum dependence of the damping rate of the collective excitations.
A closed formula for the evaluation of foams
2020
International audience; We give a purely combinatorial formula for evaluating closed, decorated foams. Our evaluation gives an integral polynomial and is directly connected to an integral, equivariant version of colored Khovanov-Rozansky link homology categorifying the sl(N) link polynomial. We also provide connections to the equivariant cohomology rings of partial flag varieties.
Neutrino transport in coherent quasiparticle approximation
2012
We introduce the coherent quasiparticle approximation (cQPA), a model in thermal quantum field theory which describes various effects of temporally varying thermal medium on particle propagation. We present the cQPA Feynman rules and develop related calculational tools. Using these methods we calculate neutrino self energies in the Standard Model and derive an equation of motion for neutrino propagation in a very general framework. Some immediate implications of this equation are discussed. (More detailed abstract in the PDF file.)
Lowest order perturbative quantum field theory calculations of bound state decay widths
2017
Alimman kertaluvun häiriöteoreettisia kvanttikenttäteorialaskuja sidottujen tilojen hajoamisleveyksille. Työssä lasketaan sidottujen tilojen hajoamisleveydet prosesseille $J/ \psi \rightarrow l^+ l^-$, $\eta_c \rightarrow gg$, $\text{O-Ps}\rightarrow \gamma\gamma\gamma$, $J/ \psi \rightarrow ggg$ ja $J/ \psi \rightarrow \gamma gg$. Prosessit lasketaan perturbatiivisen QED:n ja QCD:n alimmassa kertaluvussa. Laskuissa käydään läpi kolme erilaista tekniikkaa invariantin amplitudin käsittelemiseksi. Johdetut hajoamisleveystulokset käyvät yksiin kirjallisuudesta löytyvien tulosten kanssa. Lisäksi tarkastellaan kokeellisesti varmistettavissa olevia hajoamisleveyssuhteita. Teoreettiset ennusteet o…