19,735 research outputs found
Symmetries in nonlinear Bethe-Heitler process
Nonlinear Bethe-Heitler process in a bichromatic laser field is investigated
using strong-field QED formalism. Symmetry properties of angular distributions
of created pairs are analyzed. These properties are showed to be
governed by a behavior of the vector potential characterizing the laser field,
rather than by the respective electric field component.Comment: 4 pages, 4 figure
Non trivial generalizations of the Schwinger pair production result II
It is suggested that Schwinger's (1951) vacuum persistence probability
against pair production by an intense but constant electric field is a very
good approximation to the corresponding quantity if the field does not vary
appreciably over distances less than m/e/E/5 pagesComment: 5 page
On a scale-invariant Fermi gas in a time-dependent harmonic potential
We investigate a scale-invariant two-component Fermi gas in a time-dependent
isotropic harmonic potential. The exact time evolution of the density
distribution in position space in any spatial dimension is obtained. Two
experimentally relevant examples, an abrupt change and a periodic modulation of
the trapping frequency are solved. Small deviations from scale invariance and
isotropy of the confinement are addressed within first order perturbation
theory. We discuss the consequences for experiments with ultracold quantum
gases such as the excitation of a tower of undamped breathing modes and a new
alternative for measuring the Tan contact.Comment: 6+3 pages, 2 figures; revised and extended versio
Multiple colliding electromagnetic pulses: a way to lower the threshold of pair production from vacuum
The scheme of simultaneous multiple pulse focusing on one spot naturally
arises from the structural features of projected new laser systems, such as ELI
and HiPER. It is shown that the multiple pulse configuration is beneficial for
observing pair production from vacuum under the action of sufficiently
strong electromagnetic fields. The field of the focused pulses is described
using a realistic three-dimensional model based on an exact solution of the
Maxwell equations. The pair production threshold in terms of
electromagnetic field energy can be substantially lowered if, instead of one or
even two colliding pulses, multiple pulses focused on one spot are used. The
multiple pulse interaction geometry gives rise to subwavelength field features
in the focal region. These features result in the production of extremely short
bunches.Comment: 10 pages, 4 figure
- …