A quantum kinetic equation is derived for the description of pair production in a timedependent homogeneous electric field E(t). 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 kinetic equation of non-Markovian character. 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 discuss the momentum and time dependence of the derived source term and compare with other approaches. *
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 Maxwell's equation in the presence of feedback yields an internal current and electric field that exhibit plasma oscillations with a period pl . Allowing for collisions, these oscillations are damped on a time scale r determined by the collision frequency. Plasma oscillations cannot affect the early stages of the formation of a quark-gluon plasma unless r ӷ pl and pl ϳ1/⌳ QCD ϳ1 fm/c. ͓S0556-2821͑99͒06123-8͔
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.
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.Comment: 11 pages, revteX, epsfig.sty, 6 figure
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.
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