Suchergebnisse

The characterization of dark energy is one of the primary goals in cosmology especially now that many new experiments are being planned with the aim of reaching a high sensitivity on cosmological parameters. It is known that if we move away from the simple cosmological constant model then we need to consider perturbations in the dark energy fluid. This means that dark energy has two extra degrees of freedom: the sound speed cs2 and the anisotropic stress σ. If dark energy is inhomogenous at the scales of interest then the gravitational potentials are modified and the evolution of the dark matter perturbations is also directly affected. In this paper we add an anisotropic component to the dark energy perturbations. Following the idea introduced in D. Sapone and M. Kunz, Phys. Rev. D 80, 083519 (2009), we solve analytically the equations of perturbations in the dark sector, finding simple and accurate approximated solutions. We also find that the evolution of the density perturbations is governed by an effective sound speed that depends on both the sound speed and the anisotropic stress parameter. We then use these solutions to look at the impact of the dark energy perturbations on the matter power spectrum and on the integrated Sachs-Wolfe effect in the cosmic microwave background ; D. S. acknowledges support from the JAEDoc program with ref. JAEDoc074 and the Spanish MICINN under the project AYA2009-13936-C06-06. D. S. also acknowledges financial support from the Madrid Regional Government (CAM) under the program HEPHACOS P-ESP-00346, Consolider-Ingenio 2010 PAU (CSD2007-00060), as well as in the European Union Marie Curie Network ''UniverseNet'' under Contract No.MRTNCT- 2006-035863. E.M. was supported by the Spanish MICINNs Juan de la Cierva program (JCI-2010-08112), by CICYT through the project FPA-2009 09017, by the Community of Madrid through the project HEPHACOS (S2009/ESP-1473) under Grant No. P-ESP-00346, and by the European Union ITN project (FP7-PEOPLE-2011-ITN, PITN-GA-2011-289442-INVISIBLES)

If light enough primordial black holes (PBH) account for dark matter, then its density decreases with time as they lose mass via Hawking radiation. We show that this time-dependence of the matter density can be formulated as an equivalent w(z) dark energy model and we study its implications on the expansion history. Using our approach and comparing with the latest cosmological data, including the supernovae type Ia, Baryon Acoustic Oscillations, Cosmic Microwave Background and the Hubble expansion H(z) data, we place observational constraints on the PBH model. We find that it is statistically consistent with.CDMaccording to the AIC statistical tool. Furthermore, we entertain the idea of having a population of ultra-light PBHs, decaying around neutrino decoupling, on top of the dark matter fluid and show how this offers a natural dark matter-radiation coupling altering the expansion history of the Universe and alleviating the H-0 tension. ; MINECO-FEDER, Spain FPA2015-68048-03-3P Centro de Excelencia Severo Ochoa Program, Spain SEV-2016-0597 Spanish Government RYC-2014-15843 CUniverse research promotion project (CUAASC) at Chulalongkorn University, Thailand PGC2018-094773-B-C32

Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM ; We systematically study the null-test for the growth rate data first presented in [S. Nesseris and D. Sapone, arXiv:1409.3697.] and we reconstruct it using various combinations of data sets, such as the fσ8 and H(z) or type Ia supernovae data. We perform the reconstruction in two different ways, either by directly binning thedata or by fitting various dark energy models. We also examine how well the null-test can be reconstructed by future data by creating mock catalogs based on the cosmological constant model, a model with strong dark energy perturbations, the f(R) and f(G) models, and the large void Lemaitre-Tolman-Bondi model that exhibit different evolution of the matter perturbations. We find that with future data similar to an LSST-like survey, the null-test will be able to successfully discriminate between these different cases at the 5σ level ; The authors acknowledge financial support from the Madrid Regional Government (CAM) under the Grant No. HEPHACOS S2009/ESP-1473-02, from MICINN under Grant No. FPA2012-39684-C03-02 and Consolider-Ingenio 2010 PAU (Grant No. CSD2007-00060), as well as from the European Union Marie Curie Initial Training Network UNILHC Grant No. PITN-GA-2009-237920. We also acknowledge the support of the Spanish MINECO's "Centro de Excelencia Severo Ochoa" Programme under Grant No. SEV-2012-0249

Recent work has demonstrated that it is important to constrain the dynamics of cosmological perturbations, in addition to the evolution of the background, if we want to distinguish among different models of the dark sector. Especially the anisotropic stress of the (possibly effective) dark energy fluid has been shown to be an important discriminator between modified gravity and dark energy models. In this paper we use approximate analytical solutions of the perturbation equations in the presence of viscosity to study how the anisotropic stress affects the weak lensing and galaxy power spectrum. We then forecast how sensitive the photometric and spectroscopic Euclid surveys will be to both the speed of sound and the viscosity of our effective dark energy fluid when using weak lensing tomography and the galaxy power spectrum. We find that Euclid alone can only constrain models with a very small speed of sound and viscosity, while it will need the help of other observables in order to give interesting constraints on models with a sound speed close to one. This conclusion is also supported by the expected Bayes factor between models ; D. S. acknowledges support from the JAEDoc program with Grant No. JAEDoc074 and the Spanish MICINN under Project No. AYA2009-13936-C06-06. D. S. also acknowledges financial support from the Madrid Regional Government (CAM) under the program HEPHACOS P-ESP-00346, Consolider-Ingenio 2010 PAU (CSD2007-00060), as well as the European Union Marie Curie Network ''UniverseNet'' under Contract No. MRTN-CT-2006-035863. E. M. was supported by the Spanish MICINNs Juan de la Cierva programme (Grant No. JCI-2010-08112), by CICYT through Project No. FPA-2009 09017, by the Community of Madrid through the project HEPHACOS (Grant No. S2009/ESP- 1473) under Grant No. P-ESP-00346 and by the European Union FP7 ITN INVISIBLES (Marie Curie Actions, PITNGA-2011-289442). M. K. acknowledges funding by the Swiss NSF

[Context] In metric theories of gravity with photon number conservation, the luminosity and angular diameter distances are related via the Etherington relation, also known as the distance duality relation (DDR). A violation of this relation would rule out the standard cosmological paradigm and point to the presence of new physics. Aims. We quantify the ability of Euclid, in combination with contemporary surveys, to improve the current constraints on deviations from the DDR in the redshift range 0 < z < 1.6. ; [Methods] We start with an analysis of the latest available data, improving previously reported constraints by a factor of 2.5. We then present a detailed analysis of simulated Euclid and external data products, using both standard parametric methods (relying on phenomenological descriptions of possible DDR violations) and a machine learning reconstruction using genetic algorithms. ; [Results] We find that for parametric methods Euclid can (in combination with external probes) improve current constraints by approximately a factor of six, while for non-parametric methods Euclid can improve current constraints by a factor of three.; [Conclusions] Our results highlight the importance of surveys like Euclid in accurately testing the pillars of the current cosmological paradigm and constraining physics beyond the standard cosmological model. ; MM has received the support of a fellowship from "la Caixa" Foundation (ID 100010434), with fellowship code LCF/BQ/PI19/11690015, and the support of the Spanish Agencia Estatal de Investigacion through the grant "IFT Centro de Excelencia Severo Ochoa SEV-2016-0597". The work of CJM was financed by FEDER – Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020 – Operational Programme for Competitiveness and Internationalisation (POCI), and by Portuguese funds through FCT - Fundação para a Ciência e a Tecnologia in the framework of the project POCI-01-0145-FEDER-028987. S.N. acknowledges support from the research project PGC2018-094773-B-C32, the Centro de Excelencia Severo Ochoa Program SEV-2016-059 and the Ramón y Cajal program through Grant No. RYC-2014-15843. D.S. acknowledges financial support from the Fondecyt Regular project number 1200171. I.T. acknowledges support from the Spanish Ministry of Science, Innovation and Universities through grant ESP2017-89838-C3-1-R, and the H2020 programme of the European Commission through grant 776247. A.A. acknowledges support from the Science and Technology Facilities Council (STFC) grant ST/P000703/1. V.Y. acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement No. 769130)

Context. Stage IV weak lensing experiments will offer more than an order of magnitude leap in precision. We must therefore ensure that our analyses remain accurate in this new era. Accordingly, previously ignored systematic effects must be addressed.Aims. In this work, we evaluate the impact of the reduced shear approximation and magnification bias on information obtained from the angular power spectrum. To first-order, the statistics of reduced shear, a combination of shear and convergence, are taken to be equal to those of shear. However, this approximation can induce a bias in the cosmological parameters that can no longer be neglected. A separate bias arises from the statistics of shear being altered by the preferential selection of galaxies and the dilution of their surface densities in high-magnification regions.Methods. The corrections for these systematic effects take similar forms, allowing them to be treated together. We calculated the impact of neglecting these effects on the cosmological parameters that would be determined from Euclid, using cosmic shear tomography. To do so, we employed the Fisher matrix formalism, and included the impact of the super-sample covariance. We also demonstrate how the reduced shear correction can be calculated using a lognormal field forward modelling approach.Results. These effects cause significant biases in Omega (m), sigma (8), n(s), Omega (DE), w(0), and w(a) of -0.53 sigma, 0.43 sigma, -0.34 sigma, 1.36 sigma, -0.68 sigma, and 1.21 sigma, respectively. We then show that these lensing biases interact with another systematic effect: the intrinsic alignment of galaxies. Accordingly, we have developed the formalism for an intrinsic alignment-enhanced lensing bias correction. Applying this to Euclid, we find that the additional terms introduced by this correction are sub-dominant. ; Royal Society of London NASA Postdoctoral Program Fellowship UK Science and Technologies Facilities Council National Aeronautics & Space Administration (NASA) European Space Agency Academy of Finland Italian Space Agency (ASI) Belgian Federal Science Policy Office Canadian Euclid Consortium Centre National D'etudes Spatiales Helmholtz Association German Aerospace Centre (DLR) Danish Space Research Institute Portuguese Foundation for Science and Technology Spanish Government Netherlandse Onderzoekschool Voor Astronomie Norwegian Space Agency Romanian Space Agency State Secretariat for Education, Research and Innovation (SERI) at the Swiss Space Office (SSO) United Kingdom Space Agency

Context. In metric theories of gravity with photon number conservation, the luminosity and angular diameter distances are related via the Etherington relation, also known as the distance duality relation (DDR). A violation of this relation would rule out the standard cosmological paradigm and point to the presence of new physics.Aims. We quantify the ability of Euclid, in combination with contemporary surveys, to improve the current constraints on deviations from the DDR in the redshift range 0< z< 1.6.Methods. We start with an analysis of the latest available data, improving previously reported constraints by a factor of 2.5. We then present a detailed analysis of simulated Euclid and external data products, using both standard parametric methods (relying on phenomenological descriptions of possible DDR violations) and a machine learning reconstruction using genetic algorithms.Results. We find that for parametric methods Euclid can (in combination with external probes) improve current constraints by approximately a factor of six, while for non-parametric methods Euclid can improve current constraints by a factor of three.Conclusions. Our results highlight the importance of surveys like Euclid in accurately testing the pillars of the current cosmological paradigm and constraining physics beyond the standard cosmological model. ; La Caixa Foundation 100010434 LCF/BQ/PI19/11690015 Spanish Agencia Estatal de Investigacion through the grant "IFT Centro de Excelencia Severo Ochoa" SEV-2016-0597 FEDER -Fundo Europeu de Desenvolvimento Regional funds through the COMPETE 2020 -Operational Programme for Competitiveness and Internationalisation (POCI) Portuguese funds through FCT -Fundacao para a Ciencia e a Tecnologia POCI-01-0145-FEDER-028987 Centro de Excelencia Severo Ochoa Program SEV-2016-059 Spanish Government RYC-2014-15843 Comision Nacional de Investigacion Cientifica y Tecnologica (CONICYT) CONICYT FONDECYT 1200171 Spanish Ministry of Science, Innovation and Universities ESP2017-89838-C3-1-R H2020 programme of the European Commission 776247 UK Research & Innovation (UKRI) Science & Technology Facilities Council (STFC) Science and Technology Development Fund (STDF) ST/P000703/1 European Research Council (ERC) 769130 Academy of Finland European Commission Agenzia Spaziale Italiana (ASI) Belgian Federal Science Policy Office Canadian Euclid Consortium Centre National D'etudes Spatiales Helmholtz Association German Aerospace Centre (DLR) Danish Space Research Institute Portuguese Foundation for Science and Technology European Commission Spanish Government National Aeronautics & Space Administration (NASA) Netherlandse Onderzoekschool Voor Astronomie Norwegian Space Agency Romanian Space Agency State Secretariat for Education, Research and Innovation (SERI) at the Swiss Space O ffice (SSO) United Kingdom Space Agency PGC2018-094773-B-C32