Assisted Vacuum Decay by Time Dependent Electric Fields

We consider the vacuum decay by electron-positron pair production in spatially homogeneous, time dependent electric fields by means of quantum kinetic equations. Our focus is on the impact of various pulse shapes as envelopes of oscillating fields and the assistance effects in multi-scale fields, which are also seen in photons accompanying the creation and motion of pairs.Comment: 9 pages, 7 figure

Proceedings of the Miniworkshop "Electromagnetic Radiation off Colliding Hadron Systems: Dileptons and Bremsstrahlung"

Since several years various groups of the Institute of Nuclear und Hadron Physics at Forschungszentrurn Rossendorf (FZR) are involved in medium energy physics projects where electromagnetic signals play a role: (i) pp bremsstrahlung experiments at COSY-ToF have been proposed by a group from Dresden with FZR participation, and a large part of the ToF detector system has been built in Rossendorf. (ii) The FZR is presently building one of the large wire chamber planes for the HADES detector at GSI and is also actively taking part in the HADES commissioning. (iii) The theory group here at Rossendorf is working in the field of dilepton production and other electromagnetic processes. To discuss the research in these fields with colleagues from other places and to coordinate the efforts this mini-workshop was organized. The idea was to discuss the results of the experiments at different accelerators, the status of the calculations and the plans for future investigations. Besides bremsstrahlung special emphasis will be on dielectron production; other processes with electromagnetic signals (like vector-meson production) have also been discussed

Thermal dilepton and open charm signals versus hard initial yields in heavy-ion collisions at RHIC and LHC energies

The hard initial production of open charm and dileptons is compared with possible thermal signals in heavy-ion collisions at RHIC and LHC energies. Our approach is based on the perturbative QCD mini-jet mechanism of quark-gluon matter formation. The thermal dilepton signal is found to rise much stronger as compared to the hard Drell - Yan background with increasing collider energy and clearly dominates at LHC energy. Oppositely, open charm stems from initial hard production. A possible rnanifestation of gluon shadowing at RHIC and LHC energies is discussed

Dynamical Schwinger process in a bifrequent electric field of finite duration: survey on amplification

The electron-positron pair production due to the dynamical Schwinger process in a slowly oscillating strong electric field is enhanced by the superposition of a rapidly oscillating weaker electric field. A systematic account of the enhancement by the resulting bifrequent field is provided for the residual phase space distribution. The enhancement is explained by a severe reduction of the suppression in both the tunneling and multiphoton regimes

Contribution of the massive photon decay channel to the neutrino cooling of neutron stars

The role of the massive photon decay via intermediate states of electron-electron-holes and proton-proton-holes into neutrino-anti-neutrino pairs in the course of neutron star cooling is investigated. These reactions may ba operative in hot neutron stars in the region of proton pairing. The corresponding contribution to the neutrino emissivity is calculated. It varies with the temperature as T3/2e−mγ/T for T < m γ, where mγ is an effective photon mass in superconducting matter. Estimates show that this process appears as strong cooling channel of neutron stars at temperatures T ≈ ( 10^9 - 10^10) K