S. A. Smolyansky

A Quantum kinetic equation for particle production in the Schwinger mechanism

A quantum kinetic equation has been derived for the description of pair production in a time-dependent homogeneous electric field

Pair production and optical lasers.

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Pair creation: Back reactions and damping

. As a source term, the Schwinger mechanism for particle creation is incorporated. Possible particle production due to collisions and collisional damping are neglected. The main result is a closed kinetic equation of the non-Markovian type. In the low density approximation, the source term is reduced to the leading part of the well known Schwinger formula for the probability of pair creation. We compare the formula obtained with other approaches and discuss the differences.

Non-Markovian effects in strong-field pair creation

Electron-positron pair creation in a standing wave is explored using a parameter-free quantum kinetic equation. Field strengths and frequencies corresponding to modern optical lasers induce a material polarization of the QED vacuum, which may be characterized as a plasma of e+e- quasiparticle pairs with a density of approximately 10(20) cm-3. The plasma vanishes almost completely when the laser field is zero, leaving a very small residual pair density n(r) which is the true manifestation of vacuum decay. The average pair density per period is proportional to the laser intensity but independent of the frequency nu. The density of residual pairs also grows with laser intensity but n(r) proportional to nu(2). With optical lasers at the forefront of the current generation, these dynamical QED vacuum effects can plausibly generate 5-10 observable two-photon annihilation events per laser pulse.

Lifting shell structures in the dynamically assisted Schwinger effect in periodic fields

We solve the quantum Vlasov equation for fermions and bosons, incorporating spontaneous pair creation in the presence of back reactions and collisions. Pair creation is initiated by an external impulse field and the source term is non-Markovian. A simultaneous solution of Maxwells equation in the presence of feedback yields an internal current and electric field that exhibit plasma oscillations with a period {tau}{sub pl}. Allowing for collisions, these oscillations are damped on a time scale {tau}{sub r} determined by the collision frequency. Plasma oscillations cannot affect the early stages of the formation of a quark-gluon plasma unless {tau}{sub r}>>{tau}{sub pl} and {tau}{sub pl}{approx}1/{lambda}{sub QCD}{approx}1 fm/c. (c) 1999 The American Physical Society.

Plasma production and thermalisation in a strong field

We analyze a quantum kinetic equation describing both boson and fermion pair production and explore analytically and numerically the solution of the non-Markovian kinetic equation. In the Markovian limit of the kinetic equation we find an analytical solution for the single particle distribution function of bosons and fermions. The numerical investigation for a homogeneous, constant electric field shows an enhancement (bosons) or a suppression (fermions) of the pair creation rate according to the symmetry character of the produced particles. For strong fields non-Markovian effects are important while they disappear for weak fields. Hence it is sufficient to apply the low density limit for weak fields but necessary to take into account memory effects for strong fields.

THE KINETIC DESCRIPTION OF VACUUM PARTICLE CREATION IN THE OSCILLATOR REPRESENTATION

Abstract The dynamically assisted pair creation (Schwinger effect) is considered for the superposition of two periodic electric fields acting in a finite time interval. We find a strong enhancement by orders of magnitude caused by a weak field with a frequency being a multitude of the strong-field frequency. The strong low-frequency field leads to shell structures which are lifted by the weaker high-frequency field. The resonance type amplification refers to a new, monotonously increasing mode, often hidden in some strong oscillatory transient background, which disappears during the smoothly switching off the background fields, thus leaving a pronounced residual shell structure in phase space.

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

Aspects of the formation and equilibration of a quark-gluon plasma are explored using a quantum kinetic equation, which involves a non-Markovian, Abelian source term for quark and antiquark production and, for the collision term, a relaxation time approximation that defines a time-dependent quasi-equilibrium temperature and collective velocity. The strong Abelian field is determined via the simultaneous solution of Maxwells equation. A particular feature of this approach is the appearance of plasma oscillations in all thermodynamic observables. Their presence can lead to a sharp increase in the time-integrated dilepton yield.

Dynamical Schwinger effect and high-intensity lasers. Realising nonperturbative QED

The oscillator representation is used for the nonperturbative description of vacuum particle creation in a strong time-dependent electric field in the framework of scalar QED. It is shown that the method can be more effective for the derivation of the quantum kinetic equation (KE) in comparison with the Bogoliubov method of time-dependent canonical transformations. This KE is used for the investigation of vacuum creation in periodical linear and circular polarized electric fields and also in the case of the presence of a constant magnetic field, including the back reaction problem. In particular, these examples are applied for a model illustration of some features of vacuum creation of electron–positron plasma within the planned experiments on the X-ray free electron lasers.

Inertial mechanism: Dynamical mass as a source of particle creation

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.