57,742 research outputs found
R-modes of neutron stars with a solid crust
We investigate the properties of -mode oscillations of a slowly rotating
neutron star with a solid crust, by taking account of the effects of the
Coriolis force. For the modal analysis we employ three-component neutron star
models that are composed of a fluid core, a solid crust and a surface fluid
ocean. For the three-component models, we find that there exist two kinds of
-modes, that is, those confined in the surface fluid ocean and those
confined in the fluid core, which are most important for the -mode
instability. The -modes do not have any appreciable amplitudes in the solid
crust if rotation rate of the star is sufficiently small. We find that the core
-modes are strongly affected by mode coupling with the crustal torsional
(toroidal) modes and lose their simple properties of the eigenfunction and
eigenfrequency as functions of the angular rotation velocity . This
indicates that the extrapolation formula, which is obtained in the limit of
, cannot be used to examine the -mode instability of rapidly
rotating neutron stars with a solid crust unless the effects of mode coupling
with the crustal torsional modes are correctly taken into account.Comment: 10 pages, 3 figures, revised version accepted for publication in the
Ap
Observation of Scarred Modes in Asymmetrically Deformed Microcylinder Lasers
We report observation of lasing in the scarred modes in an asymmetrically
deformed microcavity made of liquid jet. The observed scarred modes correspond
to morphology-dependent resonance of radial mode order 3 with their Q values in
the range of 10^6. Emission directionality is also observed, corresponding to a
hexagonal unstable periodic orbit.Comment: 4 pages, 6 figure
Collins Asymmetry at Hadron Colliders
We study the Collins effect in the azimuthal asymmetric distribution of
hadrons inside a high energy jet in the single transverse polarized proton
proton scattering. From the detailed analysis of one-gluon and two-gluon
exchange diagrams contributions, the Collins function is found the same as that
in the semi-inclusive deep inelastic scattering and e^+e^- annihilations. The
eikonal propagators in these diagrams do not contribute to the phase needed for
the Collins-type single spin asymmetry, and the universality is derived as a
result of the Ward identity. We argue that this conclusion depends on the
momentum flow of the exchanged gluon and the kinematic constraints in the
fragmentation process, and is generic and model-independent.Comment: 23 pages, 6 figure
A Fully Tunable Single-Walled Carbon Nanotube Diode
We demonstrate a fully tunable diode structure utilizing a fully suspended
single-walled carbon nanotube (SWNT). The diode's turn-on voltage under forward
bias can be continuously tuned up to 4.3 V by controlling gate voltages, which
is ~6 times the nanotube bandgap energy. Furthermore, the same device design
can be configured into a backward diode by tuning the band-to-band tunneling
current with gate voltages. A nanotube backward diode is demonstrated for the
first time with nonlinearity exceeding the ideal diode. These results suggest
that a tunable nanotube diode can be a unique building block for developing
next generation programmable nanoelectronic logic and integrated circuits.Comment: 14 pages, 4 figure
Non-LTE Monte Carlo Radiative Transfer: II. Non-Isothermal Solutions for Viscous Keplerian Disks
We discuss the basic hydrodynamics that determines the density structure of
the disks around hot stars. Observational evidence supports the idea that these
disks are Keplerian (rotationally supported) gaseous disks. A popular scenario
in the literature, which naturally leads to the formation of Keplerian disks,
is the viscous decretion model. According to this scenario, the disks are
hydrostatically supported in the vertical direction, while the radial structure
is governed by the viscous transport. This suggests that the temperature is one
primary factor that governs the disk density structure. In a previous study we
demonstrated, using 3-D NLTE Monte Carlo simulations, that viscous keplerian
disks can be highly non-isothermal. In this paper we build upon our previous
work and solve the full problem of the steady-state non-isothermal viscous
diffusion and vertical hydrostatic equilibrium. We find that the
self-consistent solution departs significantly from the analytic isothermal
density, with potentially large effects on the emergent spectrum. This implies
that non-isothermal disk models must be used for a detailed modeling of Be star
disks.Comment: 22 pages, 9 figures, Ap
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