2,050,878 research outputs found
Conductance fluctuations in quasi-two-dimensional systems: a practical view
The universal conductance fluctuations of quasi-two-dimensional systems are
analyzed with experimental considerations in mind. The traditional statistical
metrics of these fluctuations (such as variance) are shown to have large
statistical errors in such systems. An alternative characteristic is
identified, the inflection point of the correlation function in magnetic field,
which is shown to be significantly more useful as an experimental metric and to
give a more robust measure of phase coherence.Comment: 9 pages, 7 figure
Extensive population synthesis of isolated neutron stars with field decay
We perform population synthesis studies of different types of neutron stars
taking into account the magnetic field decay. For the first time, we confront
our results with observations using {\it simultaneously} the Log N -- Log S
distribution for nearby isolated neutron stars, the Log N -- Log L distribution
for magnetars, and the distribution of radio pulsars in the --
diagram. We find that our theoretical model is consistent with all sets of data
if the initial magnetic field distribution function follows a log-normal law
with and . The
typical scenario includes about 10% of neutron stars born as magnetars,
significant magnetic field decay during the first million years of a NS life.
Evolutionary links between different subclasses may exist, although robust
conclusions are not yet possible.
We apply the obtained field distribution and the model of decay to study
long-term evolution of neuton stars till the stage of accretion from the
interstellar medium. It is shown that though the subsonic propeller stage can
be relatively long, initially highly magnetized neutron stars ( G) reach the accretion regime within the Galactic lifetime if their
kick velocities are not too large. The fact that in previous studies made 10
years ago, such objects were not considered results in a slight increase of the
Accretor fraction in comparison with earlier conclusions. Most of the neutron
stars similar to the Magnificent seven are expected to become accreting from
the interstellar medium after few billion years of their evolution. They are
the main predecestors of accreting isolated neutron stars.Comment: 4 pages, conference "Astrophysics of Neutron Stars - 2010" in honor
of M. Ali Alpar, Izmir, Turke
The Theory of SNOM: A Novel Approach
In this paper we consider the application of electromagnetic theory to the
analysis of the Scanning Near-field Optical Microscope (SNOM) in order to
predict experimentally observable quantities such as the transmission or
reflection coefficients for a particular tip-surface configuration. In
particular we present the first application of a transfer matrix based
calculation to this challenging problem by using an adaptive co-ordinate
transformation to accurately model the shape of the SNOM tip.
We also investigate the possibility of increasing the transmitted light
through the SNOM tip by introducing a metal wire into the centre of the tip.
This converts the tip into a co-axial cable. We show that, in principle, this
can dramatically improve the transmission characteristics without having a
detrimental effect on the resolution.Comment: 19 pages, 11 figures. To be published in the Journal of Modern Optic
Static pressure correction in high Reynolds number fully developed turbulent pipe flow
Measurements are reported of the error in wall static pressure reading due to the finite size of the pressure tapping. The experiments were performed in incompressible turbulent pipe flow over a wide range of Reynolds numbers, and the results indicate that the correction term (as a fraction of the wall stress) continues to increase as the hole Reynolds number increases, contrary to previous studies. For small holes relative to the pipe diameter the results follow a single curve, but for larger holes the data diverge from this universal behaviour at a point that depends on the ratio of the hole diameter to the pipe diameter
Design procedure for low-drag subsonic airfoils
Airfoil has least amount of drag under given restrictions of boundary layer transition position, lift coefficient, thickness ratio, and Reynolds number based on airfoil chord. It is suitable for use as wing and propeller aircraft sections operating at subsonic speeds and for hydrofoil sections and blades for fans, compressors, turbines, and windmills
Penrose Diagram for a Transient Black Hole
A Penrose diagram is constructed for a spatially coherent black hole that
smoothly begins an accretion, then excretes symmetrically as measured by a
distant observer, with the initial and final states described by a metric of
Minkowski form. Coordinate curves on the diagram are computationally derived.
Causal relationships between space-time regions are briefly discussed. The life
cycle of the black hole demonstrably leaves asymptotic observers in an
unaltered Minkowski space-time of uniform conformal scale.Comment: 14 pages, 9 figures, spelling correction
Solar Neutrino Matter Effects Redux
Following recent low-threshold analysis of the Sudbury Neutrino Observatory
and asymmetry measurements of the BOREXINO Collaboration of the solar neutrino
flux, we revisit the analysis of the matter effects in the Sun. We show that
solar neutrino data constrains the mixing angle poorly and that
subdominant Standard Model effects can mimic the effects of the physics beyond
the Standard Model.Comment: 12 pages of LATEX, 8 figure
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