4,570 research outputs found
CMB polarization as a probe of the anomalous nature of the Cold Spot
One of the most interesting explanations for the non-Gaussian Cold Spot (CS)
detected in the WMAP data by Vielva et al. 2004, is that it arises from the
interaction of the CMB radiation with a cosmic texture (Cruz et al. 2007b). In
this case, a lack of polarization is expected in the region of the spot, as
compared to the typical values associated to large fluctuations of a GIRF. In
addition, other physical processes related to a non-linear evolution of the
gravitational field could lead to a similar scenario. However, some of these
alternative scenarios (e.g., a large void in the large scale structure) have
been shown to be very unlikely. In this work we characterise the polarization
properties of the Cold Spot under both hypotheses: a large Gaussian spot and an
anomalous feature generated, for instance, by a cosmic texture. We propose a
methodology to distinguish between them, and we discuss its discrimination
power as a function of the instrumental noise level. In particular, we address
the cases of current experiments, like WMAP and Planck, and others in
development as QUIJOTE. We find that for an ideal experiment the Gaussian
hypothesis could be rejected at a significance level better than 0.8%. While
WMAP is far from providing useful information in this respect, we find that
Planck will be able to reach a significance of around 7%; in addition, we show
that the ground-based experiment QUIJOTE could provide a significance of around
1%. If these results are combined with the significance level found for the CS
in temperature, the capability of QUIJOTE and Planck to reject the alternative
hypothesis becomes 0.025% and 0.124%, respectively.Comment: 7 pages, 3 figures, accepted in MNRAS. Minor changes made to match
the final versio
Pobreza y políticas de desarrollo rural en México
La lucha contra la pobreza en lo rural ha dejado de ser prioritaria en algunos países, fruto de una aparente mejoría de sus condi- ciones de vida. El estudio de las políticas de desarrollo rural en México resulta de espe- cial interés, por cuanto este país se sitúa a la vanguardia en el intento de aumentar la coordinación de sus políticas, siendo este objeto de evaluación en este trabajo. A par- tir de la información obtenida con las en- trevistas realizadas en dos rondas a expertos en desarrollo rural – metodología Delphi – , en este trabajo se analiza la desatención de la pobreza en zonas rurales, aportando los expertos sus valoraciones acerca de la efi ca- cia que en la reducción de la pobreza rural están teniendo las políticas implementadas, planteándose el interés de seguir profundi- zando las reformas iniciadas
Anomalous variance in the WMAP data and Galactic Foreground residuals
A previous work (Monteser\'in et al. 2008) estimated the CMB variance from
the three-year WMAP data, finding a lower value than expected from Gaussian
simulations using the WMAP best-fit cosmological model. We repeat the analysis
on the five-year WMAP data using a new estimator with lower bias and variance.
Our results confirm this anomaly at higher significance, namely with a p-value
of 0.31%. We perform the analysis using different exclusion masks, showing that
a particular region of the sky near the Galactic plane shows a higher variance
than 95.58% of the simulations whereas the rest of the sky has a lower variance
than 99.96% of the simulations. The relative difference in variance between
both regions is bigger than in 99.64% of the simulations. This anisotropic
distribution of power seems to be causing the anomaly since the model assumes
isotropy. Furthermore, this region has a clear frequency dependence between
41GHz and 61GHz or 94GHz suggesting that Galactic foreground residuals could be
responsible for the anomaly. Moreover, removing the quadrupole and the octopole
from data and simulations the anomaly disappears. The variance anomaly and the
previously reported quadrupole and octopole alignment seem therefore to be
related and could have a common origin. We discuss different possible causes
and Galactic foreground residuals seem to be the most likely one. These
residuals would affect the estimation of the angular power spectrum from the
WMAP data, which is used to generate Gaussian simulations, giving rise to an
inconsistency between the estimated and expected CMB variance. If the presence
of residuals is confirmed, the estimation of the cosmological parameters could
be affected.Comment: Accepted for publication in MNRAS. Analysis section rewritten. New
exclusion masks are used finding a high variance region. Relation to the
Quadrupole-Octopole alignment foun
Mini-quadrotor Attitude Control based on Hybrid Backstepping & Frenet-Serret Theory
This paper is about modeling and control of miniature quadrotors, with a special emphasis on attitude control. Mathematical models for simulation and nonlinear control approaches are introduced and subsequently applied to commercial aircraft: the DraganFlyer quadrotor, which has been hardware-modified in order to perform experimental autonomous flying. Hybrid Backstepping control and the Frenet-Serret theory is used for attitude stabilization, introducing a desired attitude angle acceleration function dependent on aircraft velocity. Finally, improvements on disturbance rejection and attitude tracking at moderate aircraft speeds are validated through various simulation scenarios (indoor navigation based on camera tracking), and flight experiments conducted on the DraganFlyer quadroto
On the optimality of the spherical Mexican hat wavelet estimator for the primordial non-Gaussianity
We study the spherical Mexican hat wavelet (SMHW) as a detector of primordial
non-Gaussianity of the local type on the Cosmic Microwave Background (CMB)
anisotropies. For this purpose we define third order statistics based on the
wavelet coefficient maps and the original map. We find the dependence of these
statistics in terms of the non-linear coupling parameter fnl and the bispectrum
of this type of non-Gaussianity. We compare the analytical values for these
statistics with the results obtained with non-Gaussian simulations for an ideal
full-sky CMB experiment without noise. We study the power of this method to
detect fnl, i. e. the variance of this parameter, and compare it with the
variance obtained from the primary bispectrum for the same experiment. Finally
we apply our wavelet based estimator on WMAP-like maps with incomplete sky and
inhomogeneous noise and compare with the optimal bispectrum estimator. The
results show that the wavelet cubic statistics are as efficient as the
bispectrum as optimal detectors of this type of primordial non-Gaussianity.Comment: 10 pages, 9 figures, 1 table. Minor revision, references added,
accepted for publication in MNRA
Seasonal and Sexual Differences in the Microbiota of the Hoopoe Uropygial Secretion
The uropygial gland of hoopoe nestlings and nesting females hosts bacterial symbionts that
cause changes in the characteristics of its secretion, including an increase of its antimicrobial activity.
These changes occur only in nesting individuals during the breeding season, possibly associated
with the high infection risk experienced during the stay in the hole-nests. However, the knowledge
on hoopoes uropygial gland microbial community dynamics is quite limited and based so far on
culture-dependent and molecular fingerprinting studies. In this work, we sampled wild and captive
hoopoes of different sex, age, and reproductive status, and studied their microbiota using quantitative
polymerase chain reaction (qPCR), fluorescence in situ hybridization (FISH) and pyrosequencing.
Surprisingly, we found a complex bacterial community in all individuals (including non-nesting
ones) during the breeding season. Nevertheless, dark secretions from nesting hoopoes harbored
significantly higher bacterial density than white secretions from breeding males and both sexes in
winter. We hypothesize that bacterial proliferation may be host-regulated in phases of high infection
risk (i.e., nesting). We also highlight the importance of specific antimicrobial-producing bacteria
present only in dark secretions that may be key in this defensive symbiosis. Finally, we discuss the
possible role of environmental conditions in shaping the uropygial microbiota, based on differences
found between wild and captive hoopoes.This work was supported by the Spanish Ministry of Economy and Competitiveness and European
(FEDER) funds (CGL2013-48193-C3-1-P/BOS, CGL2013-48193-C3-2-P/BOS, CGL2017-83103-P), and the Junta de
Andalucía (RNM 339, RNM 340). S. M. Rodríguez-Ruano received a grant from the Spanish Ministry of Science
and Innovation (FPI program)
Wilkinson Microwave Anisotropy Probe 7-yr constraints on fNL with a fast wavelet estimator
A new method to constrain the local non-linear coupling parameter fNL based
on a fast wavelet decomposition is presented. Using a multiresolution wavelet
adapted to the HEALPix pixelization, we have developed a method that is 10^2
times faster than previous estimators based on isotropic wavelets and 10^3
faster than the KSW bispectrum estimator, at the resolution of the Wilkinson
Microwave Anisotropy Probe (WMAP) data. The method has been applied to the WMAP
7-yr V+W combined map, imposing constraints on fNL of -69 < fNL < 65 at the 95
per cent CL. This result has been obtained after correcting for the
contribution of the residual point sources which has been estimated to be fNL =
7 +/- 6. In addition, a Gaussianity analysis of the data has been carried out
using the third order moments of the wavelet coefficients, finding consistency
with Gaussianity. Although the constrainsts imposed on fNL are less stringent
than those found with optimal estimators, we believe that a very fast method,
as the one proposed in this work, can be very useful, especially bearing in
mind the large amount of data that will be provided by future experiments, such
as the Planck satellite. Moreover, the localisation of wavelets allows one to
carry out analyses on different regions of the sky. As an application, we have
separately analysed the two hemispheres defined by the dipolar modulation
proposed by Hoftuft et al. (2009). We do not find any significant asymmetry
regarding the estimated value of fNL in those hemispheres.Comment: 8 pages, 5 figures. Submitted and Accepted for publication in MNRA
Testing Gaussianity on Archeops Data
A Gaussianity analysis using a goodness-of-fit test and the Minkowski
functionals on the sphere has been performed to study the measured Archeops
Cosmic Microwave Background (CMB) temperature anisotropy data for a 143 GHz
Archeops bolometer. We consider large angular scales, greater than 1.8 degrees,
and a large fraction of the North Galactic hemisphere, around 16%, with a
galactic latitude b > 15 degrees.
The considered goodness-of-fit test, first proposed by Rayner & Best (1989),
has been applied to the data after a signal-to-noise decomposition. The three
Minkowski functionals on the sphere have been used to construct a chi-square
statistic using different thresholds. The first method has been calibrated
using simulations of Archeops data containing the CMB signal and instrumental
noise in order to check its asymptotic convergence. Two kind of maps produced
with two different map-making techniques (coaddition and Mirage) have been
analysed.
Archeops maps for both Mirage and coaddition map-making, have been found to
be compatible with Gaussianity. From these results we can exclude a dust and
atmospheric contamination larger than 7.8% (90% CL). Also the non-linear
coupling parameter f_{nl} can be constrained to be -800 < f_{nl} < 1100 at the
95% CL and on angular scales of 1.8 degrees. For comparison, the same method
has been applied to data from the NASA WMAP satellite in the same region of
sky. The 1-year and 3-year releases have been used. Results are compatible with
those obtained with Archeops, implying in particular an upper limit for f_{nl}
on degree angular scales.Comment: A&A accepted. The limits on the contamination and the fnl parameter
have been improve
Integrable models and degenerate horizons in two-dimensional gravity
We analyse an integrable model of two-dimensional gravity which can be
reduced to a pair of Liouville fields in conformal gauge. Its general solution
represents a pair of ``mirror'' black holes with the same temperature. The
ground state is a degenerate constant dilaton configuration similar to the
Nariai solution of the Schwarzschild-de Sitter case. The existence of
solutions and their relation with the solution given by the 2D
Birkhoff's theorem is then investigated in a more general context. We also
point out some interesting features of the semiclassical theory of our model
and the similarity with the behaviour of AdS black holes.Comment: Latex, 16 pages, 1 figur
Chromomagnetic Dipole Moment of the Top Quark Revisited
We study the complete one-loop contributions to the chromagnetic dipole
moment of the top quark in the Standard Model, two Higgs doublet
models, topcolor assited technicolor models (TC2), 331 models and extended
models with a single extra dimension. We find that the SM predicts
and that the predictions of the other models are also
consitent with the constraints imposed on by low-energy
precision measurements.Comment: 20 pages, 5 figures, Updat
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