3,017 research outputs found
Analysis of weighted networks
The connections in many networks are not merely binary entities, either
present or not, but have associated weights that record their strengths
relative to one another. Recent studies of networks have, by and large, steered
clear of such weighted networks, which are often perceived as being harder to
analyze than their unweighted counterparts. Here we point out that weighted
networks can in many cases be analyzed using a simple mapping from a weighted
network to an unweighted multigraph, allowing us to apply standard techniques
for unweighted graphs to weighted ones as well. We give a number of examples of
the method, including an algorithm for detecting community structure in
weighted networks and a new and simple proof of the max-flow/min-cut theorem.Comment: 9 pages, 3 figure
Применение корреляционно-регрессионного и геоинформационного анализа для определения взаимного влияния показателей социальной комфортности элементов городской инфраструктуры на кадастровую стоимость объектов недвижимого имущества
Determinants of Antepartum Human Immunodeficiency Virus Testing in a Non-Medicaid Obstetric Population
On Deusons or Deuteronlike Meson-Meson Bound States
The systematics of deuteronlike two-meson bound states, {\it deusons}, is
discussed. Previous arguments that many of the present non- states are
such states are elaborated including, in particular, the tensor potential. For
pseudoscalar states the important observation is made that the centrifugal
barrier from the P-wave can be overcome by the and terms of the
tensor potential. In the heavy meson sector one-pion exchange alone is strong
enough to form at least deuteron-like and composites
bound by approximately 50 MeV, while and states are
expected near the threshold.Comment: Invited talk at the Hadron93 International Conf. on Hadron
Spectroscopy, Como, Italy 22.-25.6. 1993. 5 pages in LATEX HU-SEFT R 1993-13
Improving the Robustness of the Advanced LIGO Detectors to Earthquakes
Teleseismic, or distant, earthquakes regularly disrupt the operation of ground–based gravitational wave detectors such as Advanced LIGO. Here, we present EQ mode, a new global control scheme, consisting of an automated sequence of optimized control filters that reduces and coordinates the motion of the seismic isolation platforms during earthquakes. This, in turn, suppresses the differential motion of the interferometer arms with respect to one another, resulting in a reduction of DARM signal at frequencies below 100 mHz. Our method greatly improved the interferometers\u27 capability to remain operational during earthquakes, with ground velocities up to 3.9 μm s−1 rms in the beam direction, setting a new record for both detectors. This sets a milestone in seismic controls of the Advanced LIGO detectors\u27 ability to manage high ground motion induced by earthquakes, opening a path for further robust operation in other extreme environmental conditions
Cost-benefit analysis for commissioning decisions in GEO600
Gravitational wave interferometers are complex instruments, requiring years
of commissioning to achieve the required sensitivities for the detection of
gravitational waves, of order 10^-21 in dimensionless detector strain, in the
tens of Hz to several kHz frequency band. Investigations carried out by the
GEO600 detector characterisation group have shown that detector
characterisation techniques are useful when planning for commissioning work. At
the time of writing, GEO600 is the only large scale laser interferometer
currently in operation running with a high duty factor, 70%, limited chiefly by
the time spent commissioning the detector. The number of observable
gravitational wave sources scales as the product of the volume of space to
which the detector is sensitive and the observation time, so the goal of
commissioning is to improve the detector sensitivity with the least possible
detector down time. We demonstrate a method for increasing the number of
sources observable by such a detector, by assessing the severity of
non-astrophysical noise contaminations to efficiently guide commissioning. This
method will be particularly useful in the early stages and during the initial
science runs of the aLIGO and adVirgo detectors, as they are brought up to
design performance.Comment: 17 pages, 17 figures, 2 table
Stellar Collisions and Ultracompact X-ray Binary Formation
(abridged) We report the results of SPH calculations of parabolic collisions
between a subgiant or slightly evolved red-giant star and a neutron star (NS).
Such collisions are likely to form ultracompact X-ray binaries (UCXBs) observed
today in old globular clusters. In particular, we compute collisions of a 1.4
Msun NS with realistically modelled parent stars of initial masses 0.8 and 0.9
Msun, each at three different evolutionary stages (corresponding to three
different radii R). The distance of closest approach for the initial orbit
varies from 0.04 R (nearly head-on) to 1.3 R (grazing). These collisions lead
to the formation of a tight binary, composed of the NS and the subgiant or
red-giant core, embedded in an extremely diffuse common envelope (CE) typically
of mass ~0.1 to 0.3 Msun. Our calculations follow the binary for many hundreds
of orbits, ensuring that the orbital parameters we determine at the end of the
calculations are close to final. Some of the fluid initially in the envelope of
the (sub)giant, from 0.003 to 0.023 Msun in the cases we considered, is left
bound to the NS. The eccentricities of the resulting binaries range from about
0.2 for our most grazing collision to about 0.9 for the nearly head-on cases.
In almost all the cases we consider, gravitational radiation alone will cause
sufficiently fast orbital decay to form a UCXB within a Hubble time, and often
on a much shorter timescale. Our hydrodynamics code implements the recent SPH
equations of motion derived with a variational approach by Springel & Hernquist
and by Monaghan. Numerical noise is reduced by enforcing an analytic constraint
equation that relates the smoothing lengths and densities of SPH particles. We
present tests of these new methods to help demonstrate their improved accuracy.Comment: 41 pages, 17 figures, accepted by Ap
Abstract Poisson summation formulas over homogeneous spaces of compact groups
This paper presents the abstract notion of Poisson summation formulas for homogeneous spaces of compact groups. Let G be a compact group, H be a closed subgroup of G, and μ be the normalized G-invariant measure over the left coset space G / H associated to the Weil’s formula. We prove that the abstract Fourier transform over G / H satisfies a generalized version of the Poisson summation formula
GEO 600 and the GEO-HF upgrade program: successes and challenges
The German-British laser-interferometric gravitational wave detector GEO 600
is in its 14th year of operation since its first lock in 2001. After GEO 600
participated in science runs with other first-generation detectors, a program
known as GEO-HF began in 2009. The goal was to improve the detector sensitivity
at high frequencies, around 1 kHz and above, with technologically advanced yet
minimally invasive upgrades. Simultaneously, the detector would record science
quality data in between commissioning activities. As of early 2014, all of the
planned upgrades have been carried out and sensitivity improvements of up to a
factor of four at the high-frequency end of the observation band have been
achieved. Besides science data collection, an experimental program is ongoing
with the goal to further improve the sensitivity and evaluate future detector
technologies. We summarize the results of the GEO-HF program to date and
discuss its successes and challenges
Characterization of thermal effects in the Enhanced LIGO Input Optics
We present the design and performance of the LIGO Input Optics subsystem as
implemented for the sixth science run of the LIGO interferometers. The Initial
LIGO Input Optics experienced thermal side effects when operating with 7 W
input power. We designed, built, and implemented improved versions of the Input
Optics for Enhanced LIGO, an incremental upgrade to the Initial LIGO
interferometers, designed to run with 30 W input power. At four times the power
of Initial LIGO, the Enhanced LIGO Input Optics demonstrated improved
performance including better optical isolation, less thermal drift, minimal
thermal lensing and higher optical efficiency. The success of the Input Optics
design fosters confidence for its ability to perform well in Advanced LIGO
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