19,025 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
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
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
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