1,702 research outputs found
Pair production in a strong electric field: an initial value problem in quantum field theory
We review recent achievements in the solution of the initial-value problem
for quantum back-reaction in scalar and spinor QED. The problem is formulated
and solved in the semiclassical mean-field approximation for a homogeneous,
time-dependent electric field. Our primary motivation in examining
back-reaction has to do with applications to theoretical models of production
of the quark-gluon plasma, though we here address practicable solutions for
back-reaction in general. We review the application of the method of adiabatic
regularization to the Klein-Gordon and Dirac fields in order to renormalize the
expectation value of the current and derive a finite coupled set of ordinary
differential equations for the time evolution of the system. Three time scales
are involved in the problem and therefore caution is needed to achieve
numerical stability for this system. Several physical features, like plasma
oscillations and plateaus in the current, appear in the solution. From the
plateau of the electric current one can estimate the number of pairs before the
onset of plasma oscillations, while the plasma oscillations themselves yield
the number of particles from the plasma frequency.
We compare the field-theory solution to a simple model based on a
relativistic Boltzmann-Vlasov equation, with a particle production source term
inferred from the Schwinger particle creation rate and a Pauli-blocking (or
Bose-enhancement) factor. This model reproduces very well the time behavior of
the electric field and the creation rate of charged pairs of the semiclassical
calculation. It therefore provides a simple intuitive understanding of the
nature of the solution since nearly all the physical features can be expressed
in terms of the classical distribution function.Comment: Old paper, already published, but in an obscure journa
Pair creation in transport equations using the equal-time Wigner function
Based on the equal-time Wigner function for the Klein-Gordon field, we
discuss analytically the mechanism of pair creation in a classical
electromagnetic field including back-reaction. It is shown that the equations
of motion for the Wigner function can be reduced to a variable-frequency
oscillator. The pair-creation rate results then from a calculation analogous to
barrier penetration in nonrelativistic quantum mechanics. The Wigner function
allows one to utilize this treatment for the formulation of an effective
transport theory for the back-reaction problem with a pair-creation source term
including Bose enhancement.Comment: 19 pages, LaTeX, UFTP 316/199
Back-reaction in a cylinder
A system is studied in which initially a strong classical electric field
exists within an infinitely-long cylinder and no charges are present.
Subsequently, within the cylinder, pairs of charged particles tunnel out from
the vacuum and the current produced through their acceleration by the field
acts back on the field, setting up plasma oscillations. This yields a rough
model of phenomena that may occur in the pre-equilibrium formation phase of a
quark-gluon plasma. In an infinite volume, this back-reaction has been studied
in a field-theory description, and it has been found that the results of a full
calculation of this sort are well represented in a much simpler transport
formalism. It is the purpose here to explore that comparison for a situation
involving a cylindrical volume of given radius.Comment: 19 pages plus 13 figure
Pair creation: back-reactions and damping
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 tau_pl. Allowing for collisions, these oscillations
are damped on a time-scale, tau_r, determined by the collision frequency.
Plasma oscillations cannot affect the early stages of the formation of a
quark-gluon plasma unless tau_r >> tau_pl and tau_pl approx. 1/Lambda_QCD
approx 1 fm/c.Comment: 16 pages, 6 figure, REVTEX, epsfig.st
Relativistic Kinetic Equations for Electromagnetic, Scalar and Pseudoscalar Interactions
We derive the kinetic equations for both the covariant and equal-time Wigner
functions of Dirac particles with electromagnetic, scalar and pseudoscalar
interactions. We emphasize the constraint equations for the spinor components
in the equal-time formulation.Comment: 12 pages, no figures, revte
Dileptons from Disoriented Chiral Condensates
Disoriented chiral condensates or long wavelength pionic oscillations and
their interaction with the thermal environment can be a significant source of
dileptons. We calculate the yield of such dilepton production within the linear
sigma model, both in a quantal mean-field treatment and in a semi-classical
approximation. We then illustrate the basic features of the dilepton spectrum
in a schematic model. We find that dilepton yield with invariant mass near and
below due to the soft pion modes can be up to two orders of
magnitude larger than the corresponding equilibrium yield.Comment: 22 pages, 8 figures, uses epsf-styl
Electrostatic pair creation and recombination in quantum plasmas
The collective production of electron-positron pairs by electrostatic waves
in quantum plasmas is investigated. In particular, a semi-classical governing
set of equation for a self-consistent treatment of pair creation by the
Schwinger mechanism in a quantum plasma is derived.Comment: 4 pages, 3 figures, to appear in JETP Letter
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