46,321 research outputs found
Gauge dependence of calculations in relativistic Coulomb excitation
Before a quantum-mechanical calculation involving electromagnetic
interactions is performed, a choice must be made of the gauge to be used in
expressing the potentials. If the calculation is done exactly, the observable
results it predicts will be independent of the choice of gauge. However, in
most practical calculations approximations are made, which can destroy the
gauge invariance of the predictions. We compare here the results of
coupled-channel time-dependent relativistic Coulomb excitation calculations, as
performed in either Lorentz or Coulomb gauges. We find significant differences
when the bombarding energy per nucleon is 2 GeV, which indicates that
the common practice of relying completely on the Lorentz gauge can be
dangerous.Comment: 23 pages, 3 figure
Rutherford scattering with radiation damping
We study the effect of radiation damping on the classical scattering of
charged particles. Using a perturbation method based on the Runge-Lenz vector,
we calculate radiative corrections to the Rutherford cross section, and the
corresponding energy and angular momentum losses.Comment: Latex, 11 pages, 4 eps figure
Generalization of the Schott energy in electrodynamic radiation theory
We discuss the origin of the Schott energy in the Abraham-Lorentz version of
electrodynamic radiation theory and how it can be used to explain some apparent
paradoxes. We also derive the generalization of this quantity for the
Ford-O'Connell equation, which has the merit of being derived exactly from a
microscopic Hamiltonian for an electron with structure and has been shown to be
free of the problems associated with the Abraham-Lorentz theory. We emphasize
that the instantaneous power supplied by the applied force not only gives rise
to radiation (acceleration fields), but it can change the kinetic energy of the
electron and change the Schott energy of the velocity fields. The important
role played by boundary conditions is noted
Algebraic {}-Integration and Fourier Theory on Quantum and Braided Spaces
We introduce an algebraic theory of integration on quantum planes and other
braided spaces. In the one dimensional case we obtain a novel picture of the
Jackson -integral as indefinite integration on the braided group of
functions in one variable . Here is treated with braid statistics
rather than the usual bosonic or Grassmann ones. We show that the definite
integral can also be evaluated algebraically as multiples of the
integral of a -Gaussian, with remaining as a bosonic scaling variable
associated with the -deformation. Further composing our algebraic
integration with a representation then leads to ordinary numbers for the
integral. We also use our integration to develop a full theory of -Fourier
transformation . We use the braided addition and braided-antipode to define a convolution product, and prove a
convolution theorem. We prove also that . We prove the analogous results
on any braided group, including integration and Fourier transformation on
quantum planes associated to general R-matrices, including -Euclidean and
-Minkowski spaces.Comment: 50 pages. Minor changes, added 3 reference
Scattering of surface plasmons by one-dimensional periodic nanoindented surfaces
In this work, the scattering of surface plasmons by a finite periodic array
of one-dimensional grooves is theoretically analyzed by means of a modal
expansion technique. We have found that the geometrical parameters of the array
can be properly tuned to achieve optimal performance of the structure either as
a Bragg reflector or as a converter of surface plasmons into light. In this
last case, the emitted light is collimated within a few degrees cone.
Importantly, we also show that a small number of indentations in the array are
sufficient to fully achieve its functional capabilities.Comment: 5 pages, 5 figures; changed sign convention in some definition
Coulomb Excitation of Multi-Phonon Levels of the Giant Dipole Resonance
A closed expression is obtained for the cross-section for Coulomb excitation
of levels of the giant dipole resonance of given angular momentum and phonon
number. Applications are made to the Goldhaber-Teller and Steinwedel-Jensen
descriptions of the resonance, at non-relativistic and relativistic bombarding
energies.Comment: 16 pages, 5 figure
Quantum derivation of the use of classical electromagnetic potentials in relativistic Coulomb excitation
We prove that a relativistic Coulomb excitation calculation in which the
classical electromagnetic field of the projectile is used to induce transitions
between target states gives the same target transition amplitudes, to all
orders of perturbation theory, as would a calculation in which the interaction
between projectile and target is mediated by a quantized electromagnetic field.Comment: 1 .zip file containing LaTex source plus three figures as .eps file
Influence of magnetic-field inhomogeneity on nonlinear magneto-optical resonances
In this work, a sensitivity of the rate of relaxation of ground-state atomic
coherences to magnetic-field inhomogeneities is studied. Such coherences give
rise to many interesting phenomena in light-atom interactions, and their
lifetimes are a limiting factor for achieving better sensitivity, resolution or
contrast in many applications. For atoms contained in a vapor cell, some of the
coherence-relaxation mechanisms are related to magnetic-field inhomogeneities.
We present a simple model describing relaxation due to such inhomogeneities in
a buffer-gas-free anti-relaxation coated cell. A relation is given between
relaxation rate and magnetic-field inhomogeneities including the dependence on
cell size and atomic spices. Experimental results, which confirm predictions of
the model, are presented. Different regimes, in which the relaxation rate is
equally sensitive to the gradients in any direction and in which it is
insensitive to gradients transverse to the bias magnetic field, are predicted
and demonstrated experimentally.Comment: 6 pages, 4 figures, Submitted to Phys. Rev.
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