52,028 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
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
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
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
Helical Symmetry in Linear Systems
We investigate properties of solutions of the scalar wave equation and
Maxwell's equations on Minkowski space with helical symmetry. Existence of
local and global solutions with this symmetry is demonstrated with and without
sources. The asymptotic properties of the solutions are analyzed. We show that
the Newman--Penrose retarded and advanced scalars exhibit specific symmetries
and generalized peeling properties.Comment: 11 page
Higgs boson production with one bottom quark including higher-order soft-gluon corrections
A Higgs boson produced in association with one or more bottom quarks is of
great theoretical and experimental interest to the high-energy community. A
precise prediction of its total and differential cross-section can have a great
impact on the discovery of a Higgs boson with large bottom-quark Yukawa
coupling, like the scalar (h^0 and H^0) and pseudoscalar (A^0) Higgs bosons of
the Minimal Supersymmetric Standard Model (MSSM) in the region of large
\tan\beta. In this paper we apply the threshold resummation formalism to
determine both differential and total cross-sections for b g \to b\Phi (where
\Phi = h^0, H^0), including up to next-to-next-to-next-to-leading order (NNNLO)
soft plus virtual QCD corrections at next-to-leading logarithmic (NLL)
accuracy. We present results for both the Fermilab Tevatron and the CERN Large
Hadron Collider (LHC).Comment: revtex4, 13 pages, 11 figures; new references and additional comment
A simple derivation of the electromagnetic field of an arbitrarily moving charge
The expression for the electromagnetic field of a charge moving along an
arbitrary trajectory is obtained in a direct, elegant, and Lorentz invariant
manner without resorting to more complicated procedures such as differentiation
of the Lienard-Wiechert potentials. The derivation uses arguments based on
Lorentz invariance and a physically transparent expression originally due to
J.J.Thomson for the field of a charge that experiences an impulsive
acceleration.Comment: The following article has been accepted by the American Journal of
Physics. After it is published, it will be found at
http://scitation.aip.org/ajp; 12 pages, 1 figur
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