50 research outputs found
NN bundle method applied to cosmology: an improvement in computational times
In the last few years, there has been significant progress in the development
of machine learning methods tailored to astrophysics and cosmology. Among the
various methods that have been developed, there is one that allows to obtain a
bundle of solutions of differential systems without the need of using
traditional numerical solvers. We have recently applied this to the
cosmological scenario and showed that in some cases the computational times of
the inference process can be reduced. In this paper, we present an improvement
to the neural network bundle method that results in a significant reduction of
the computational times of the statistical analysis. The novelty of the method
consists in the use of the neural network bundle method to calculate the
luminosity distance of type Ia supernovae, which is usually computed through an
integral with numerical methods. In this work, we have applied this improvement
to the Starobinsky model, which is more difficult to integrate than the
models analyzed in our previous work. We performed a statistical
analysis with data from type Ia supernovae of the Pantheon+ compilation and
cosmic chronometers to estimate the values of the free parameters of the
Starobinsky model. We show that the statistical analyses carried out with our
new method require lower computational times than the ones performed with both
the numerical and the neural network method from our previous work. This
reduction in time is more significant in the case of a difficult computational
problem such as the one we address in this work.Comment: 11 pages, 3 figures, 2 tables, to be submitted to PR
B polarization of the CMB from Faraday rotation
We study the effect of Faraday rotation due to a homogeneous magnetic field
on the polarization of the cosmic microwave background (CMB). Scalar
fluctuations give rise only to parity-even E-type polarization of the CMB.
However in the presence of a magnetic field, a non-vanishing parity-odd B-type
polarization component is produced through Faraday rotation. We derive the
exact solution for the E and B modes generated by scalar perturbations
including the Faraday rotation effect of a uniform magnetic field, and evaluate
their cross-correlations with temperature anisotropies. We compute the angular
autocorrelation function of the B-modes in the limit that the Faraday rotation
is small. We find that primordial magnetic fields of present strength around
G rotate E-modes into B-modes with amplitude comparable to those
due to the weak gravitational lensing effect at frequencies around
GHz. The strength of B-modes produced by Faraday rotation scales as
. We evaluate also the depolarizing effect of Faraday rotation upon
the cross correlation between temperature anisotropy and E-type polarization.Comment: 11 pages, 4 figures. Minor changes to match the published versio
Constraining the halo bispectrum in real and redshift space from perturbation theory and non-linear stochastic bias
This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2015 RAS. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reservedWe present a method to produce mock galaxy catalogues with efficient perturbation theory schemes, which match the number density, power spectra and bispectra in real and in redshift space from N-body simulations. The essential contribution of this work is the way in which we constrain the bias parameters of the PATCHY-code. In addition to aiming at reproducing the two-point statistics, we seek the set of bias parameters, which constrain the univariate halo probability distribution function (PDF) encoding higher order correlation functions. We demonstrate that halo catalogues based on the same underlying dark matter field with a fix halo number density, and accurately matching the power spectrum (within 2 per cent) can lead to very different bispectra depending on the adopted halo bias model. A model ignoring the shape of the halo PDF can lead to deviations up to factors of 2. The catalogues obtained additionally constraining the shape of the halo PDF can significantly lower the discrepancy in the three-point statistics, yielding closely unbiased bispectra both in real and in redshift space; which are in general compatible with those corresponding to an N-body simulation within 10 per cent (deviating at most up to 20 per cent). Our calculations show that the constant linear bias of ~2 for luminous red galaxy (LRG) like galaxies found in the power spectrum, mainly comes from sampling haloes in high-density peaks, choosing a high-density threshold rather than from a factor multiplying the dark matter density field. Our method contributes towards an efficient modelling of the halo/galaxy distribution required to estimate uncertainties in the clustering measurements from galaxy redshift surveys. We have also demonstrated that it represents a powerful tool to test various bias modelsHGM is grateful for support from the UK Science and Technology Facilities Council through the grant ST/I001204/1. CGS acknowledges funding from the Spanish Ministry of Economy and Competitiveness (MINECO) under the project AYA2012-3972-C02-01. CC and FP were supported by (MINECO) under the project AYA2012-3972-C02-01. CC and FP were supported by the Spanish MICINNs Consolider-Ingenio 2010 Programme under grant MultiDark CSD2009-00064 and AYA2010-21231-C02-01 grant, the Comunidad de Madrid under grant HEPHACOS S2009/ESP-1473, and Spanish MINECOs Centro de Excelencia
Severo Ochoa Programme under grant SEV-2012-0249. GY and FP acknowledge support
from the Spanish MINECO under research grants AYA2012-31101, FPA2012-34694, AYA2010-21231, Consolider Ingenio SyeC CSD2007-0050 and from Comunidad de Madrid
under ASTROMADRID project (S2009/ESP-1496
Early Universe Constraints on Time Variation of Fundamental Constants
We study the time variation of fundamental constants in the early Universe.
Using data from primordial light nuclei abundances, CMB and the 2dFGRS power
spectrum, we put constraints on the time variation of the fine structure
constant , and the Higgs vacuum expectation value leads to a variation
in the electron mass, among other effects. Along the same line, we study the
variation of and the electron mass . In a purely phenomenological
fashion, we derive a relationship between both variations.Comment: 18 pages, 12 figures, accepted for publication in Physical Review
WMAP 5-year constraints on time variation of and in a detailed recombination scenario
We study the role of fundamental constants in an updated recombination
scenario. We focus on the time variation of the fine structure constant, and
the electron mass in the early Universe, and put bounds on these quantities by
using data from CMB including WMAP 5-yr release and the 2dFGRS power spectrum.
We analyze how the constraints are modified when changing the recombination
scenario.Comment: 11 pages, accepted for publication in Physics Letters
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: constraints on the time variation of fundamental constants from the large-scale two-point correlation function
We obtain constraints on the variation of the fundamental constants from the
full shape of the redshift-space correlation function of a sample of luminous
galaxies drawn from the Data Release 9 of the Baryonic Oscillations
Spectroscopic Survey. We combine this information with data from recent CMB,
BAO and H_0 measurements. We focus on possible variations of the fine structure
constant \alpha and the electron mass m_e in the early universe, and study the
degeneracies between these constants and other cosmological parameters, such as
the dark energy equation of state parameter w_DE, the massive neutrinos
fraction f_\nu, the effective number of relativistic species N_eff, and the
primordial helium abundance Y_He. When only one of the fundamental constants is
varied, our final bounds are \alpha / \alpha_0 = 0.9957_{-0.0042}^{+0.0041} and
m_e /(m_e)_0 = 1.006_{-0.013}^{+0.014}. For their joint variation, our results
are \alpha / \alpha_0 = 0.9901_{-0.0054}^{+0.0055} and m_e /(m_e)_0 = 1.028 +/-
0.019. Although when m_e is allowed to vary our constraints on w_DE are
consistent with a cosmological constant, when \alpha is treated as a free
parameter we find w_DE = -1.20 +/- 0.13; more than 1 \sigma away from its
standard value. When f_\nu and \alpha are allowed to vary simultaneously, we
find f_\nu < 0.043 (95% CL), implying a limit of \sum m_\nu < 0.46 eV (95% CL),
while for m_e variation, we obtain f_nu < 0.086 (95% CL), which implies \sum
m_\nu < 1.1 eV (95% CL). When N_eff or Y_He are considered as free parameters,
their simultaneous variation with \alpha provides constraints close to their
standard values (when the H_0 prior is not included in the analysis), while
when m_e is allowed to vary, their preferred values are significantly higher.
In all cases, our results are consistent with no variations of \alpha or m_e at
the 1 or 2 \sigma level.Comment: 18 pages, 16 figures. Submitted to MNRA
SDSS-III Baryon Oscillation Spectroscopic Survey data release 12 : galaxy target selection and large-scale structure catalogues
The Baryon Oscillation Spectroscopic Survey (BOSS), part of the Sloan Digital Sky Survey (SDSS) III project, has provided the largest survey of galaxy redshifts available to date, in terms of both the number of galaxy redshifts measured by a single survey, and the effective cosmological volume covered. Key to analysing the clustering of these data to provide cosmological measurements is understanding the detailed properties of this sample. Potential issues include variations in the target catalogue caused by changes either in the targeting algorithm or properties of the data used, the pattern of spectroscopic observations, the spatial distribution of targets for which redshifts were not obtained, and variations in the target sky density due to observational systematics. We document here the target selection algorithms used to create the galaxy samples that comprise BOSS. We also present the algorithms used to create large-scale structure catalogues for the final Data Release (DR12) samples and the associated random catalogues that quantify the survey mask. The algorithms are an evolution of those used by the BOSS team to construct catalogues from earlier data, and have been designed to accurately quantify the galaxy sample. The code used, designated mksample, is released with this paper.Publisher PDFPeer reviewe
QUBIC: Exploring the Primordial Universe with the Q&U Bolometric Interferometer
In this paper, we describe QUBIC, an experiment that will observe the polarized microwave sky with a novel approach, which combines the sensitivity of state-of-the-art bolometric detectors with the systematic effects control typical of interferometers. QUBIC’s unique features are the so-called “self-calibration”, a technique that allows us to clean the measured data from instrumental effects, and its spectral imaging power, i.e., the ability to separate the signal into various sub-bands within each frequency band. QUBIC will observe the sky in two main frequency bands: 150 GHz and 220 GHz. A technological demonstrator is currently under testing and will be deployed in Argentina during 2019, while the final instrument is expected to be installed during 2020.Fil: Mennella, Aniello. University of Milan; ItaliaFil: Barbaràn, Gustavo. Comisión Nacional de Energía Atómica; ArgentinaFil: Bonaparte, Juan. Comisión Nacional de Energía Atómica; ArgentinaFil: Di Donato, Andrés Leonardo. Comisión Nacional de Energía Atómica; ArgentinaFil: Etchegoyen, Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Tecnología en Detección y Astropartículas. Comisión Nacional de Energía Atómica. Instituto de Tecnología en Detección y Astropartículas. Universidad Nacional de San Martín. Instituto de Tecnología en Detección y Astropartículas; ArgentinaFil: Fasciszewski, Adrián. Comisión Nacional de Energía Atómica; ArgentinaFil: Gamboa Lerena, Martin Miguel. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Garcia, Beatriz Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Tecnología en Detección y Astropartículas. Comisión Nacional de Energía Atómica. Instituto de Tecnología en Detección y Astropartículas. Universidad Nacional de San Martín. Instituto de Tecnología en Detección y Astropartículas; ArgentinaFil: Gómez Berisso, Mariano. Centro Atómico Bariloche. Instituto Balseiro; ArgentinaFil: González. Manuel. Centro Atómico Bariloche. Instituto Balseiro; ArgentinaFil: Luterstein, Raùl Horacio. Comisión Nacional de Energía Atómica; ArgentinaFil: Harari, Diego Dario. Centro Atómico Bariloche. Instituto Balseiro; ArgentinaFil: Kristukat, Christian. Universidad Nacional de San Martín; ArgentinaFil: Medina, Maria Clementina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Mundo, Luis Mariano. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Pastoriza, Hernan. Centro Atómico Bariloche. Instituto Balseiro; ArgentinaFil: Ringegni, Pablo. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Romero, Gustavo Esteban. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Argentino de Radioastronomía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Argentino de Radioastronomía; ArgentinaFil: Scóccola, Claudia G.. Universidad Nacional de La Plata. Facultad de Ciencias Astronómicas y Geofísicas; ArgentinaFil: Suarez, Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Tecnología en Detección y Astropartículas. Comisión Nacional de Energía Atómica. Instituto de Tecnología en Detección y Astropartículas. Universidad Nacional de San Martín. Instituto de Tecnología en Detección y Astropartículas; ArgentinaFil: The Qubic Collaboration. No especifíca;7th International Conference on New frontiers in PhysicsCretaGreciaCenter of the Orthodox Academy of Cret