407 research outputs found
A note on the polarization of the laser field in Mott Scattering
In the first Born approximation and using an elliptically polarized laser
field, the Mott scattering of an electron by a Coulomb potential is
investigated using the Dirac-Volkov states to describe the incident and
scattered electrons. The results obtained are compared with the results of S.M.
Li \textit{et al} \cite{1} for the case of a linearly polarized laser field and
with the results of Y. Attaourti \textit{et al} \cite{2} for the case of a
circular polarization.Comment: 9 pages, Latex, 2 figure
Self-organization of ultrasound in viscous fluids
We report the theoretical and experimental demonstration of pattern formation
in acoustics. The system is an acoustic resonator containing a viscous fluid.
When the system is driven by an external periodic force, the ultrasonic field
inside the cavity experiences different pattern-forming instabilities leading
to the emergence of periodic structures. The system is also shown to possess
bistable regimes, in which localized states of the ultrasonic field develop.
The thermal nonlinearity in the viscous fluid, together with the
far-from-equilibrium conditions, are is the responsible of the observed
effects
Quantum signatures in laser-driven relativistic multiple-scattering
The dynamics of an electronic Dirac wave packet evolving under the influence
of an ultra-intense laser pulse and an ensemble of highly charged ions is
investigated numerically. Special emphasis is placed on the evolution of
quantum signatures from single to multiple scattering events. We quantify the
occurrence of quantum relativistic interference fringes in various situations
and stress their significance in multiple-particle systems, even in the
relativistic range of laser-matter interaction.Comment: 4 pages, 2 figures, LaTeX, revtex
Momentum dependence in the dynamically assisted Sauter-Schwinger effect
Recently it has been found that the superposition of a strong and slow
electric field with a weaker and faster pulse can significantly enhance the
probability for non-perturbative electron-positron pair creation out of the
vacuum -- the dynamically assisted Sauter-Schwinger effect. Via the WKB method,
we estimate the momentum dependence of the pair creation probability and
compare it to existing numerical results. Besides the theoretical interest, a
better understanding of this pair creation mechanism should be helpful for the
planned experiments aiming at its detection.Comment: 4 pages RevTeX, 1 figur
Entangled States and Entropy Remnants of a Photon-Electron System
In the present paper an example of entanglement between two different kinds
of interacting particles, photons and electrons is analysed. The initial-value
problem of the Schroedinger equation is solved non-perturbatively for the
system of a free electron interacting with a quantized mode of the
electromagnetic radiation. Wave packets of the dressed states so obtained are
constructed in order to describe the spatio-temporal separation of the
subsystems before and after the interaction. The joint probability amplitudes
are calculated for the detection of the electron at some space-time location
and the detection of a definite number of photons. The analytical study of the
time evolution of entanglement between the initially separated electron wave
packet and the radiation mode leads to the conclusion that in general there are
non-vanishing entropy remnants in the subsystems after the interaction. On the
basis of the simple model to be presented here, the calculated values of the
entropy remnants crucially depend on the character of the switching-on and off
of the interaction.Comment: 12 pages, 2 figure
Quantum simulator for the Schwinger effect with atoms in bi-chromatic optical lattices
Ultra-cold atoms in specifically designed optical lattices can be used to
mimic the many-particle Hamiltonian describing electrons and positrons in an
external electric field. This facilitates the experimental simulation of (so
far unobserved) fundamental quantum phenomena such as the Schwinger effect,
i.e., spontaneous electron-positron pair creation out of the vacuum by a strong
electric field.Comment: 4 pages, 2 figures; minor corrections and improvements in text and in
figures; references adde
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