arXiv subjects

Francois Gelis

Publications and source records attributed to Francois Gelis.

58 records · Page 4Linked to original sources

arXiv1997

Soft photons and hard thermal loops

We calculate within the Hard Thermal Loop expansion the production rate of soft photons and lepton pairs by a hot quark-gluon plasma at thermal equilibrium, up to the 2-loop order. Strong collinear divergences appear to mix the orders of the perturbative expansion so that the 2-loop order is in fact dominant compared to the 1-loop order. More precisely, angular integrals that would otherwise be of order 1 are found to behave as powers of $1/g$ when the produced photon is massless, therefore breaking the standard HTL power counting rules.

hep-ph↗

arXiv1997

Photons, dileptons and hard thermal loops

The production rate of soft real photons or soft lepton pairs by a hot QCD plasma is dominated by strong collinear divergences. As a consequence, it appears that the effective theory based on the resummation of hard thermal loops fails to handle properly these light-cone sensitive processes since some formally higher order diagrams are in reality the dominant ones.

hep-ph↗

arXiv1997

Cutting rules in the real time formalisms at finite temperature

In this paper, we review the set of rules specific to the calculation of the imaginary part of a Green's function at finite temperature in the real-time formalisms. Emphasis is put on the clarification of a recent controversy concerning these rules in the "1/2" formalism, more precisely on the issue related to the interpretation of these rules in terms of cut diagrams, like at T=0. On the second hand, new results are presented, enabling one to calculate the imaginary part of thermal Green's functions in other formulations of the real-time formalism, like the "retarded/advanced" formalism in which a lot of simplifications occur.

hep-ph↗

arXiv1996

Enhanced photon production near the light-cone by a hot plasma

Strong collinear divergences, although regularized by a thermal mass, result in a breakdown of the standard hard thermal loop expansion in the calculation of the production rate of photons by a plasma of quarks and gluons using thermal field theory techniques.

hep-ph↗