Real-time nonequilibrium dynamics in hot QED plasmas: Dynamical renormalization group approach - art. no. 105026

We study the real-time nonequilibrium dynamics in hot QED plasmas implement ing a dynamical renormalization group and using the hard thermal loop (HTL) approximation. The focus is on the study of the relaxation of gauge and fe rmionic mean fields and on the quantum kinetics of the photon and fermion d istribution functions. For semihard photons of momentum eT much less thank much less thanT we find to leading order in the HTL that the gauge mean fie ld relaxes in time with a power law as a result of infrared enhancement of the spectral density near the Landau damping threshold. The distribution fu nction of semihard photons in linear response also relaxes with a power law , with a power that is twice that for the mean field. The dynamical renorma lization group reveals the emergence of detailed balance for microscopic ti me scales larger than Ilk while the rates are still varying with time. The quantum kinetic equation for the photon distribution function allows us to study photon production from a thermalized quark-gluon plasma (QGP) by off- shell effects. We find that for a QGP of temperature T similar to 200 MeV a nd lifetime 10 less than or similar tot less than or similar to 50 fm/c the hard (k similar toT) photon production from off-shell bremsstrahlung (q--> q gamma and (q) over bar-->(q) over bar gamma) at O(alpha) grows logarithmi cally in time and is comparable to that produced from on-shell Compton scat tering and pair annihilation at O(alpha alpha (s)). Hard fermion mean field s relax as e(-alpha Tt ln(omega pt)) with omegap=eT/3 the plasma frequency, as a consequence of the emission and absorption of soft magnetic photons. A quantum kinetic equation for hard fermions is obtained directly in real t ime from a field theoretical approach improved by the dynamical renormaliza tion group, The collision kernel is time-dependent and infrared finite. In linear response the fermion distribution function relaxes with an anomalous exponential law with an exponent twice as large as that for the mean field .