286 research outputs found
Radiation from Excited Vortex in the Abelian Higgs Model
Excitation of a vortex in the Abelian Higgs model is investigated with the
help of a polynomial approximation. The excitation can be regarded as a
longitudinal component of the vector field trapped by the vortex. The energy
and profile of the excitation are found. Back-reaction of the excitation on the
vortex is calculated in the small limit. It turns out that in the
presence of the excitation the vortex effectively becomes much wider - its
radius oscillates in time and for all times it is not smaller than the radius
of the unexcited vortex. Moreover, we find that the vector field of the excited
vortex has long range radiative component. Bound on the amplitude of the
excitation is also found.Comment: Latex, 20 pages. 2 figures attached as .uu file to be decoded and
used as input for epsfbox command which is already included in the main Latex
fil
D-branes, Matrix Theory and K-homology
In this paper, we study a new matrix theory based on non-BPS D-instantons in
type IIA string theory and D-instanton - anti D-instanton system in type IIB
string theory, which we call K-matrix theory. The theory correctly incorporates
the creation and annihilation processes of D-branes. The configurations of the
theory are identified with spectral triples, which are the noncommutative
generalization of Riemannian geometry a la Connes, and they represent the
geometry on the world-volume of higher dimensional D-branes. Remarkably, the
configurations of D-branes in the K-matrix theory are naturally classified by a
K-theoretical version of homology group, called K-homology. Furthermore, we
argue that the K-homology correctly classifies the D-brane configurations from
a geometrical point of view. We also construct the boundary states
corresponding to the configurations of the K-matrix theory, and explicitly show
that they represent the higher dimensional D-branes.Comment: 53 pages, corrected a few typos, version published in JHE
A rare case of pigmented villonodular synovitis after unicompartmental knee replacement: a case report
Pigmented villonodular synovitis is a benign proliferative disease involving the synovium. Pigmented villonodular synovitis is rare after replacement arthroplasty and has not been recognised and reported as a cause of failure of unicompartmental knee replacement in the literature
The new generation CMB B-mode polarization experiment: POLARBEAR
We describe the Cosmic Microwave Background (CMB) polarization experiment
called Polarbear. This experiment will use the dedicated Huan Tran Telescope
equipped with a powerful 1,200-bolometer array receiver to map the CMB
polarization with unprecedented accuracy. We summarize the experiment, its
goals, and current status
A multifrequency study of the large radio galaxies 3C46 and 3C452
We present low-frequency observations starting from ~150 MHz with the Giant
Metrewave Radio Telescope (GMRT), and high-frequency observations with the Very
Large Array (VLA) of two large radio galaxies 3C46 and 3C452. These
observations were made with the objectives of estimating their spectral ages
and examining any evidence of diffuse extended emission at low radio
frequencies due to an earlier cycle of activity. While no evidence of extended
emission due to an earlier cycle of activity has been found, the spectral ages
have been estimated to be ~15 and 27 Myr for the oldest relativistic plasma
seen in the regions close to the cores for 3C46 and 3C452 respectively. The
spectra in the vicinity of the hotspots are consistent with a straight spectrum
with injection spectral indices of ~1.0 and 0.78 respectively, somewhat steeper
than theoretical expectations.Comment: Accepted for publication in MNRAS, 10 pages, 8 figures and 4 table
Ultra High Energy Cosmology with POLARBEAR
Observations of the temperature anisotropy of the Cosmic Microwave Background
(CMB) lend support to an inflationary origin of the universe, yet no direct
evidence verifying inflation exists. Many current experiments are focussing on
the CMB's polarization anisotropy, specifically its curl component (called
"B-mode" polarization), which remains undetected. The inflationary paradigm
predicts the existence of a primordial gravitational wave background that
imprints a unique B-mode signature on the CMB's polarization at large angular
scales. The CMB B-mode signal also encodes gravitational lensing information at
smaller angular scales, bearing the imprint of cosmological large scale
structures (LSS) which in turn may elucidate the properties of cosmological
neutrinos. The quest for detection of these signals; each of which is orders of
magnitude smaller than the CMB temperature anisotropy signal, has motivated the
development of background-limited detectors with precise control of systematic
effects. The POLARBEAR experiment is designed to perform a deep search for the
signature of gravitational waves from inflation and to characterize lensing of
the CMB by LSS. POLARBEAR is a 3.5 meter ground-based telescope with 3.8
arcminute angular resolution at 150 GHz. At the heart of the POLARBEAR receiver
is an array featuring 1274 antenna-coupled superconducting transition edge
sensor (TES) bolometers cooled to 0.25 Kelvin. POLARBEAR is designed to reach a
tensor-to-scalar ratio of 0.025 after two years of observation -- more than an
order of magnitude improvement over the current best results, which would test
physics at energies near the GUT scale. POLARBEAR had an engineering run in the
Inyo Mountains of Eastern California in 2010 and will begin observations in the
Atacama Desert in Chile in 2011.Comment: 8 pages, 6 figures, DPF 2011 conference proceeding
The bolometric focal plane array of the Polarbear CMB experiment
The Polarbear Cosmic Microwave Background (CMB) polarization experiment is
currently observing from the Atacama Desert in Northern Chile. It will
characterize the expected B-mode polarization due to gravitational lensing of
the CMB, and search for the possible B-mode signature of inflationary
gravitational waves. Its 250 mK focal plane detector array consists of 1,274
polarization-sensitive antenna-coupled bolometers, each with an associated
lithographed band-defining filter. Each detector's planar antenna structure is
coupled to the telescope's optical system through a contacting dielectric
lenslet, an architecture unique in current CMB experiments. We present the
initial characterization of this focal plane
Changes in behavioural synchrony during dog-assisted therapy for children with autism spectrum disorder and children with Down syndrome
BACKGROUND: Dog-assisted therapy (DAT) is hypothesized to help children with autism spectrum disorder (ASD) and Down syndrome (DS). METHODS: The present authors compared synchronous movement patterns of these children (n = 10) and their therapy dogs during the first and last session of a DAT programme, and their post-therapy changes in emotional and behavioural problems. RESULTS: The present authors found a significant increase in synchrony between child and therapy dog over time. Exploratory analyses suggest more synchrony between children with ASD and their therapy dogs, compared to the children with DS. CONCLUSIONS: This study is the first to test the synchrony hypothesis, shedding light upon a mechanism that may underlie the effect of DAT and how this may be different for children with ASD and DS
Development and characterization of the readout system for POLARBEAR-2
POLARBEAR-2 is a next-generation receiver for precision measurements of the
polarization of the cosmic microwave background (Cosmic Microwave Background
(CMB)). Scheduled to deploy in early 2015, it will observe alongside the
existing POLARBEAR-1 receiver, on a new telescope in the Simons Array on Cerro
Toco in the Atacama desert of Chile. For increased sensitivity, it will feature
a larger area focal plane, with a total of 7,588 polarization sensitive
antenna-coupled Transition Edge Sensor (TES) bolometers, with a design
sensitivity of 4.1 uKrt(s). The focal plane will be cooled to 250 milliKelvin,
and the bolometers will be read-out with 40x frequency domain multiplexing,
with 36 optical bolometers on a single SQUID amplifier, along with 2 dark
bolometers and 2 calibration resistors. To increase the multiplexing factor
from 8x for POLARBEAR-1 to 40x for POLARBEAR-2 requires additional bandwidth
for SQUID readout and well-defined frequency channel spacing. Extending to
these higher frequencies requires new components and design for the LC filters
which define channel spacing. The LC filters are cold resonant circuits with an
inductor and capacitor in series with each bolometer, and stray inductance in
the wiring and equivalent series resistance from the capacitors can affect
bolometer operation. We present results from characterizing these new readout
components. Integration of the readout system is being done first on a small
scale, to ensure that the readout system does not affect bolometer sensitivity
or stability, and to validate the overall system before expansion into the full
receiver. We present the status of readout integration, and the initial results
and status of components for the full array.Comment: Presented at SPIE Astronomical Telescopes and Instrumentation 2014:
Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for
Astronomy VII. Published in Proceedings of SPIE Volume 915
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