881 research outputs found
Non-linear general relativistic effects in the observed redshift
We present the second-order expression for the observed redshift, accounting
for all the relativistic effects from the light propagation and from the frame
change at the observer and the source positions. We derive the generic
gauge-transformation law that any observable quantities should satisfy, and we
verify our second-order expression for the observed redshift by explicitly
checking its gauge transformation property. This is the first time an explicit
verification is made for the second-order calculations of observable
quantities. We present our results in popular gauge choices for easy use and
discuss the origin of disagreements in previous calculations.Comment: 44 pages, 1 figure, Version published in JCA
Galaxy Two-Point Correlation Function in General Relativity
We perform theoretical and numerical studies of the full relativistic
two-point galaxy correlation function, considering the linear-order scalar and
tensor perturbation contributions and the wide-angle effects. Using the
gauge-invariant relativistic description of galaxy clustering and accounting
for the contributions at the observer position, we demonstrate that the
complete theoretical expression is devoid of any long-mode contributions from
scalar or tensor perturbations and it lacks the infrared divergences in
agreement with the equivalence principle. By showing that the gravitational
potential contribution to the correlation function converges in the infrared,
our study justifies an IR cut-off in computing the
gravitational potential contribution. Using the full gauge-invariant
expression, we numerically compute the galaxy two-point correlation function
and study the individual contributions in the conformal Newtonian gauge. We
find that the terms at the observer position such as the coordinate lapses and
the observer velocity (missing in the standard formalism) dominate over the
other relativistic contributions in the conformal Newtonian gauge such as the
source velocity, the gravitational potential, the integrated Sachs-Wolf effect,
the Shapiro time-delay and the lensing convergence. Compared to the standard
Newtonian theoretical predictions that consider only the density fluctuation
and redshift-space distortions, the relativistic effects in galaxy clustering
result in a few percent-level systematic errors beyond the scale of the
baryonic acoustic oscillation. Our theoretical and numerical study provides a
comprehensive understanding of the relativistic effects in the galaxy two-point
correlation function, as it proves the validity of the theoretical prediction
and accounts for effects that are often neglected in its numerical evaluation.Comment: 35 pages, 9 figures, submitted to JCA
Nuclear-cytoplasmic interactions in rat oocytes and reconstructed eggs derived by somatic cell nuclear transfer
Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal
2.45 GHz Active Isolator based on asymmetric coupler
An active isolator achieving both high isolation and low insertion loss at 2.45 GHz is proposed. The isolator is based on an asymmetric coupler and is designed to leverage the gain and reverse isolation of an amplifier and coupling coefficients between the input and output of the coupler. The insertion loss and isolation of the isolator are enhanced by using the coefficients, and the power level with optimal isolation can be determined for a target specification. The asymmetric coupler increases the power handling capability of the proposed isolator that has a low coupling coefficient and achieves highly efficient isolation with a high coupling coefficient. Electromagnetic-circuit co-simulation results show that the proposed isolator with operation stability has ≥40 dB isolation and <1 dB insertion loss for input power between 0−8 dBm
Removal of Particulate Matter in a Tubular Wet Electrostatic Precipitator Using a Water Collection Electrode
As one of the effective control devices of air pollutants, the wet electrostatic precipitator (ESP) is an effective technique to eliminate acid mist and fine particles that are re-entrained in a collection electrode. However, its collection efficiency can deteriorate, as its operation is subject to water-induced corrosion of the collection electrode. To overcome this drawback, we modified the wet ESP system with the installation of a PVC dust precipitator wherein water is supplied as a replacement of the collection electrode. With this modification, we were able to construct a compact wet ESP with a small specific collection area (SCA, 0.83 m2/(m3/min)) that can acquire a high collection efficiency of fine particles (99.7%)
A case of primary psoas abscess presenting as buttock abscess
Buttock abscess is a rare clinical manifestation from unusual extrapelvic extension of psoas abscess. A 48-year-old woman presented with painful swelling of the buttock with a sense of local heat. Magnetic resonance imaging revealed a large subfascial abscess over the glutei muscles and was traced into the intraabdominal cavity over the iliac wing to the psoas muscle. Both the psoas abscess and the buttock abscess were evacuated via separate approaches. Empirical antibiotic therapy was delivered for 3 weeks. After 6 months, no evidence of recurrence was found. Psoas abscess could be included in the differential diagnosis of buttock abscess
Galaxy Power Spectrum in General Relativity
We present the galaxy power spectrum in general relativity. Using a novel
approach, we derive the galaxy power spectrum taking into account all the
relativistic effects in observations. In particular, we show independently of
survey geometry that relativistic effects yield no divergent terms
(proportional to or on all scales) that would
mimic the signal of primordial non-Gaussianity. This cancellation of such
divergent terms is indeed expected from the equivalence principle, meaning that
any perturbation acting as a uniform gravity on the scale of the experiment
cannot be measured. We find that the unphysical infrared divergence obtained in
previous calculations occurred only due to not considering all general
relativistic contributions consistently. Despite the absence of divergent
terms, general relativistic effects represented by non-divergent terms alter
the galaxy power spectrum at large scales (smaller than the horizon scale). In
our numerical computation of the full galaxy power spectrum, we show the
deviations from the standard redshift-space power spectrum due to these
non-divergent corrections. We conclude that, as relativistic effects
significantly alter the galaxy power spectrum at , they need
to be taken into account in the analysis of large-scale data.Comment: 29 pages, 10 figures, accepted for publication in JCA
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