3,423 research outputs found
Multipolar Origin of the Unexpected Transverse Force Resulting from Two-Wave Interference
We propose a theoretical study on the electromagnetic forces resulting from
the superposition of a TE and TM plane waves interacting with a sphere.
Specifically, we first show that, under such an illumination condition, the
sphere is subjected to a force transverse to the propagation direction of the
waves. We then analyze the physical origin of this counter-intuitive behavior
using a multipolar decomposition of the electromagnetic modes involved in that
scattering process. This analysis reveals that interference effects, due to the
two-wave illumination, lead to a Kerker-like asymmetric scattering behavior
resulting in this peculiar transverse force
One-Loop Corrections to Bubble Nucleation Rate at Finite Temperature
We present an evaluation of the 1-loop prefactor in the lifetime of a
metastable state which decays at finite temperature by bubble nucleation. Such
a state is considered in one-component phi^4 model in three space dimensions.
The calculation serves as a prototype application of a fast numerical method
for evaluating the functional determinants that appear in semiclassical
approximations.Comment: DO-TH-93/18, 15 pages, 11 Figures available on request, LaTeX, no
macros neede
Global well-posedness for the critical 2D dissipative quasi-geostrophic equation
We give an elementary proof of the global well-posedness for the critical 2D
dissipative quasi-geostrophic equation. The argument is based on a non-local
maximum principle involving appropriate moduli of continuity.Comment: 7 page
Controlled switching of intrinsic localized modes in a 1-D antiferromagnet
Nearly steady-state locked intrinsic localized modes (ILMs) in the quasi-1d
antiferromagnet (C2H5NH3)2CuCl4 are detected via four-wave mixing emission or
the uniform mode absorption. Exploiting the long-time stability of these locked
ILMs, repeatable nonlinear switching is observed by varying the sample
temperature, and localized modes with various amplitudes are created by
modulation of the microwave driver power. This steady-state ILM locking
technique could be used to produce energy localization in other atomic
lattices.Comment: 4 pages, 4 figures, submitted to Phys. Rev. Lett. v.2 :
clarifications of text and figures in response to comment
Gravitational lensing due to dark matter modelled by vector field
The specified constant 4-vector field reproducing the spherically symmetric
stationary metric of cold dark matter halo in the region of flat rotation
curves results in a constant angle of light deflection at small impact
distances. The effective deflecting mass is factor greater than the
dark matter mass. The perturbation of deflection picture due to the halo edge
is evaluated.Comment: 17 pages, LaTeX iopart class, 10 eps figures; explanaitions and
discussion are extended and improved, reference added; version to appear in
Classical and Quantum Gravit
Gold-plated Mode of CP-Violation in Decays of B_c Meson from QCD Sum Rules
The model-independent method based on the triangle ideology is implemented to
extract the CKM-matrix angle gamma in the decays of doubly heavy long-lived
meson B_c. We analyze a color structure of diagrams and conditions to
reconstruct two reference-triangles by tagging the flavor and CP eigenstates of
D^0 meson in the fixed exclusive channels. The characteristic branching ratios
are evaluated in the framework of QCD sum rules.Comment: 11 pages, RevTeX4 file, 4 eps-figure
Centipede ladder at quarter filling
We study the ground state and excitation spectrum of a quasi one-dimensional
nanostructure consisting of a pole and rungs oriented in the opposite
directions ("centipede ladder", CL) at quarter filling. The spin and charge
excitation spectra are found in the limits of small and large longitudinal
hopping compared to the on-rung hopping rate and exchange
coupling . At small the system with ferromagnetic on-rung
exchange demonstrates instability against dimerization. Coherent propagation of
charge transfer excitons is possible in this limit. At large CL behaves
like two-orbital Hubbard chain, but the gap opens in the charge excitation
spectrum thus reducing the symmetry from SU(4) to SU(2). The spin excitations
are always gapless and their dispersion changes from quadratic magnon-like for
ferromagnetic on-rung exchange to linear spinon-like for antiferromagnetic
on-rung exchange in weak longitudinal hopping limit.Comment: 10 pages, 7 eps figure
Landau Theory of Domain Wall Magnetoelectricity
We calculate the exact analytical solution to the domain wall properties in a
multiferroic system with two order parameters that are coupled
bi-quadratically. This is then adapted to the case of a magnetoelectric
multiferroic material such as BiFeO3, with a view to examine critically whether
the domain walls can account for the enhancement of magnetization reported for
thin films fo this material, in view of the correlation between increasing
magnetization and increasing volume fraction of domain walls as films become
thinner. The present analysis can be generalized to describe a class of
magnetoelectric devices based upon domain walls rather than bulk properties.Comment: 9 pages, 4 figure
Multipolar expansions for scattering and optical force calculations beyond the long wavelength approximation
We review three different approaches for the calculation of electromagnetic
multipoles, namely the Cartesian primitive multipoles, the Cartesian
irreducible multipoles and the spherical multipoles. We identify the latter as
the best suited to describe the scattering of electromagnetic radiation, as
exemplified for an amorphous silicon sphere. These multipoles are then used to
calculate the optical force acting on semiconductor, dielectric or metallic
particles in a wide wavelength range, from the dipolar down to the Mie regimes
Origin of Pure Spin Superradiance
The question addressed in this paper is: What originates pure spin
superradiance in a polarized spin system placed inside a resonator? The term
"pure" means that no initial coherence is imposed on spins, and its appearance
manifests a purely self-organized collective effect. The consideration is based
on a microscopic model with dipole spin interactions. An accurate solution of
evolution equations is given. The results show that the resonator Nyquist noise
does not play, contrary to the common belief, any role in starting spin
superradiance, but the emergence of the latter is initiated by local spin
fluctuations. The decisive role of nonsecular dipole interactions is stressed.Comment: 1 file, 13 pages, RevTe
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