1,791 research outputs found
The X-ray Fundamental Plane and Relation of Clusters of Galaxies
We analyze the relations among central gas density, core radius, and
temperature of X-ray clusters by plotting the observational data in the
three-dimensional (, , and ) space and find that
the data lie on a 'fundamental plane'. Its existence implies that the clusters
form a two-parameter family. The data on the plane still has a correlation and
form a band on the plane. The observed relation turns
out to be the cross section of the band perpendicular to the major axis, while
the major axis is found to describe the virial density. We discuss implications
of this two-parameter family nature of X-ray clusters.Comment: 7 pages, 2 figures. To be published in ApJ Letter
Nuclear prolate-shape dominance with the Woods-Saxon potential
We study the prolate-shape predominance of the nuclear ground-state
deformation by calculating the masses of more than two thousand even-even
nuclei using the Strutinsky method, modified by Kruppa, and improved by us. The
influences of the surface thickness of the single-particle potentials, the
strength of the spin-orbit potential, and the pairing correlations are
investigated by varying the parameters of the Woods-Saxon potential and the
pairing interaction. The strong interference between the effects of the surface
thickness and the spin-orbit potential is confirmed to persist for six sets of
the Woods-Saxon potential parameters. The observed behavior of the ratios of
prolate, oblate, and spherical nuclei versus potential parameters are rather
different in different mass regions. It is also found that the ratio of
spherical nuclei increases for weakly bound unstable nuclei. Differences of the
results from the calculations with the Nilsson potential are described in
detail.Comment: 16 pages, 17 figure
Quantum Optics with Surface Plasmons
We describe a technique that enables strong, coherent coupling between
individual optical emitters and guided plasmon excitations in conducting
nano-structures at optical frequencies. We show that under realistic
conditions, optical emission can be almost entirely directed into the plasmon
modes. As an example, we describe an application of this technique involving
efficient generation of single photons on demand, in which the plasmon is
efficiently out-coupled to a dielectric waveguide.Comment: 11 pages, 3 figure
Electron Acceleration and Time Variability of High Energy Emission from Blazars
Blazars are known to emit a broad band emission from radio to gamma-rays with
rapid time variations, particularly, in X- and gamma-rays. Synchrotron
radiation and inverse Compton scattering are thought to play an important role
in emission and the time variations are likely related to the acceleration of
nonthermal electrons. As simultaneous multiwavelength observations with
continuous time spans are recently available, some characteristics of electron
acceleration are possibly inferred from the spectral changes of high energy
emission. In order to make such inferences, we solve the time-dependent kinetic
equations of electrons and photons simultaneously using a simple model for
electron acceleration. We then show how the time variations of emission are
dependent on electron acceleration. We also present a simple model for a flare
in X-rays and TeV gamma-rays by temporarily changing the acceleration
timescale. Our model will be used, in future, to analyze observed data in
detail to obtain information on electron acceleration in blazars.Comment: 24 pages, 12 figures, accepted by the Astrophysical Journa
A Model of the Spectral Evolution of Pulsar Wind Nebulae
Recent observations suggest that many old pulsar wind nebulae (PWNe) are
bright TeV gamma-ray sources without a strong X-ray counterpart. In this paper,
we study the spectral evolution of PWNe taking into account the energy which
was injected when they were young for old PWNe. We model the evolution of the
magnetic field and solve for the particle distribution inside a uniformly
expanding PWN. The model is calibrated by fitting the calculated spectrum to
the observations of the Crab Nebula at an age of a thousand years. We find that
only a small fraction of the injected energy from the Crab Pulsar goes to the
magnetic field, consistent with previous studies. The spectral evolution model
of the Crab Nebula shows that the flux ratio of TeV gamma-rays to X-rays
increases with time, which implies that old PWNe are faint at X-rays, but not
at TeV gamma-rays. The increase of this ratio is primarily because the magnetic
field decreases with time and is not because the X-ray emitting particles are
cooled more rapidly than the TeV gamma-ray emitting particles. Our spectral
evolution model matches the observed rate of the radio flux decrease of the
Crab Nebula.Comment: 5 pages, 3 figures. Proc. of the 2009 Fermi Symposium, Washington,
DC, Nov 2-5; eConf Proceedings C09112
Channel plasmon-polaritons: modal shape, dispersion, and losses
We theoretically study channel plasmon-polaritons (CPPs) with a geometry
similar to that in recent experiments at telecom wavelengths (Bozhevolnyi et
al., Nature 440, 508 (2006)). The CPP modal shape, dispersion relation, and
losses are simulated using the multiple multipole method and the finite
difference time domain technique. It is shown that, with the increase of the
wavelength, the fundamental CPP mode shifts progressively towards the groove
opening, ceasing to be guided at the groove bottom and becoming hybridized with
wedge plasmon-polaritons running along the groove edges.Comment: 4 pages, 4 figure
- …