Highly Radiating Charged Particles in a Strong Electromagnetic Field

We consider highly radiating ultra-relativistic electrons in a strong external electromagnetic field. High intensity radiative losses and consequent $e^+e^-$-pair production, appearing in the frame of quantum electrodynamics, determine indirectly mass operator of electrons in the strong field. We calculate a leading term of the mass operator at asymptotically high energies of electrons in a strong constant field. We do not use any perturbation theory based on a low ratio of this mass operator to the electron mass $m_e$, but only the original small parameter of quantum electrodynamics, the fine structure constant, $\alpha$. The analogous %but less nontrivial result is obtained for the polarization operator for photon propagator. These results resolve at least partially a very long-lasted controversy originating from traditional and straightforward application of perturbative approaches for description of highly radiating ultra-relativistic charged particles in a very strong electromagnetic fields.Comment: 5 page

On the new and old physics in the interaction of a radiating electron with the extreme electromagnetic field

We show that an all-optical configuration of the laser-electron collision in the $\lambda^{3}$ configuration based on 10~PW-class lasers presents a viable platform for reaching the range of parameters where a perturbative QED in strong external electromagnetic field breaks. This case is contingently referred to as a case of the nonperturbative QED; and this range of parameters is the intriguing goal from an experimental point of view because of a possible manifestation of a new physics of the interaction of a highly radiating particle with a strong electromagnetic field. We show that the strong field region can be reached by the electrons having the initial energy higher than 50 GeV. Our theoretical considerations are in agreement with three-dimensional particle-in-cell simulations. While increasing of the electron energy raises the number of electrons experiencing the strong field region, the observable signature of photon emission radiative correction in the strong field is expected to fade out when the electron energy surpasses the optimal value. This threshold of electron energy is identified and the parameters for achieving the nonperturbative limit of QED are provided.Comment: 6 pages, 2 figure

Radiation from polarized vacuum in a laser-particle collision

The probability of photon emission of a charged particle traversing a strong field becomes modified if vacuum polarization is considered. This feature is important for fundamental quantum electrodynamics processes present in extreme astrophysical environments and can be studied in a collision of a charged particle with a strong laser field. We show that for today's available 700 GeV (6.5 TeV) protons and the field provided by the next generation of lasers, the emission spectra peak is enhanced due to vacuum polarization effect by 30% (suppressed by 65%) in comparison to the traditionally considered Compton process. This striking phenomenon offers a novel path to the laboratory-based manifestation of vacuum polarization.Comment: 6 pages, 1 figur

Time-resolved extinction rates of stochastic populations

Extinction of a long-lived isolated stochastic population can be described as an exponentially slow decay of quasi-stationary probability distribution of the population size. We address extinction of a population in a two-population system in the case when the population turnover -- renewal and removal -- is much slower than all other processes. In this case there is a time scale separation in the system which enables one to introduce a short-time quasi-stationary extinction rate W_1 and a long-time quasi-stationary extinction rate W_2, and develop a time-dependent theory of the transition between the two rates. It is shown that W_1 and W_2 coincide with the extinction rates when the population turnover is absent, and present but very slow, respectively. The exponentially large disparity between the two rates reflects fragility of the extinction rate in the population dynamics without turnover.Comment: 8 pages, 4 figure

Simple Model of Propagating Flame Pulsations

A simple model which exhibits dynamical flame properties in 1D is presented. It is investigated analytically and numerically. The results are applicable to problems of flame propagation in supernovae Ia.Comment: 10 pages, 8 figures, revised version accepted by MNRA

Optimisation of Thin Plastic Foil Targets for Production of Laser-Generated Protons in the GeV Range

In order to realistically simulate the interaction of a femtosecond laser pulse with a nanometre-thick target it is necessary to consider a target preplasma formation due to the nanosecond long amplified-spontaneous-emission pedestal and/or prepulse. The relatively long interaction time dictated that hydrodynamic simulations should be employed to predict the target particles' number density distributions prior the arrival of the main laser pulse. By using the output of the hydrodynamic simulations as input into particle-in-cell simulations, a detailed understanding of the complete laser-foil interaction is achieved. Once the laser pulse interacts with the preplasma it deposits a fraction of its energy on the target, before it is either reflected from the critical density surface or transmitted through an underdense plasma channel. A fraction of hot electrons is ejected from the target leaving the foil in a net positive potential, which in turn results in proton and heavy ion ejection. In this work protons reaching ~25 MeV are predicted for a laser of ~40 TW peak power and ~600 MeV are expected from a ~4 PW laser system.Comment: 17 pages, 21 figure