Power law cosmology model comparison with CMB scale information
Isaac Tutusaus, Brahim Lamine, Alain Blanchard, Arnaud Dupays, Yves Zolnierowski, Johann Cohen-Tanugi, Anne Ealet, Stéphanie Escoffier, Olivier Le Fèvre, Stépha… 展开作者
Isaac Tutusaus, Brahim Lamine, Alain Blanchard, Arnaud Dupays, Yves Zolnierowski, Johann Cohen-Tanugi, Anne Ealet, Stéphanie Escoffier, Olivier Le Fèvre, Stéphane Ilić, Alice Pisani, Stéphane Plaszczynski, Ziad Sakr, Valentina Salvatelli, Thomas Schücker, André Tilquin, Jean-Marc Virey
Despite the ability of the cosmological concordance model ($Λ$CDM) to describe the cosmological observations exceedingly well, power law expansion of the Universe scale radius, $R(t)\propto t^n$, has been proposed as an alternative framework. We examine here these models, analyzing their ability to fit cosmological data using robust model comparison criteria. Type Ia supernovae (SNIa), baryonic acoustic oscillations (BAO) and acoustic scale information from the cosmic microwave background (CMB) have been used. We find that SNIa data either alone or combined with BAO can be well reproduced by both $Λ$CDM and power law expansion models with $n\sim 1.5$, while the constant expansion rate model $(n=1)$ is clearly disfavored. Allowing for some redshift evolution in the SNIa luminosity essentially removes any clear preference for a specific model. The CMB data are well known to provide the most stringent constraints on standard cosmological models, in particular, through the position of the first peak of the temperature angular power spectrum, corresponding to the sound horizon at recombination, a scale physically related to the BAO scale. Models with $n\geq 1$ lead to a divergence of the sound horizon and do not naturally provide the relevant scales for the BAO and the CMB. We retain an empirical footing to overcome this issue: we let the data choose the preferred values for these scales, while we recompute the ionization history in power law models, to obtain the distance to the CMB. In doing so, we find that the scale coming from the BAO data is not consistent with the observed position of the first peak of the CMB temperature angular power spectrum for any power law cosmology. Therefore, we conclude that when the three standard probes are combined, the $Λ$CDM model is very strongly favored over any of these alternative models, which are then essentially ruled out.
The weak lensing effect on the cosmic microwave background (CMB) induces distortions in spatial pattern of CMB anisotropies, and statistical properties of CMB anisotropies become a weakly non-Gaussian field. We first summarize the weak lensing effect on the CMB (CMB lensing) in the presence of scalar, vector and tensor perturbations. Then we focus on the lensing effect on CMB statistics and methods to estimate deflection angles and their power spectrum. We end by summarizing recent observational progress and future prospect.
We study the global agreement between the most recent observations of the Cosmic Microwave Background temperature and polarization anisotropies angular power spectra released by the Atacama Cosmology Telescope and the Planck satellite in various cosmological models that differ by the inclusion of different combinations of additional parameters. By using the Suspiciousness statistic, we show that the global "CMB tension" between the two experiments, quantified at the Gaussian equivalent level of $\sim 2.5\,σ$ within the baseline $Λ$CDM, is reduced at the level of $1.8σ$ when the effective numbe…
The local void model has lately attracted considerable attention since it can explain the present apparent accelerated expansion of the universe without introducing dark energy. However, in order to justify this model as an alternative cosmological model to the standard $Λ$CDM model (FLRW universe plus dark energy), one has to test the model by various observations, such as CMB temperature anisotropy, other than the distance-redshift relation of SNIa. For this purpose, we derive some analytic formulae that can be used to rigorously compare consequences of this model with observations of CMB an…
Continuous Spontaneous Localization (CSL) model of Quantum Mechanics modifies Schrödinger equation by adding non-linear stochastic terms due to which the total energy of a system increases with a constant rate which is proportional to the collapse rate $λ$. Thus applying CSL model to cosmological scenarios can change the thermal behaviour of the particles during evolution and we will put constraints on $λ$ by considering several cosmological scenarios.
In recent years cross correlation of lensing of the Cosmic Microwave Background (CMB) with other large scale structure (LSS) tracers has been used as a method to detect CMB lensing. Current experiments are also becoming sensitive enough to measure CMB lensing without the help of auxiliary tracers. As data quality improves rapidly, it has been suggested that the CMB lensing-LSS cross correlation may provide new insights into parameters describing cosmological structure growth. In this work we perform forecasts that combine the lensing potential auto power spectrum from various future CMB experi…
We discuss selected large-scale anomalies in the maps of temperature anisotropies in the cosmic microwave background. Specfically, these include alignments of the largest modes of CMB anisotropy with one another and with the geometry and direction of motion of the Solar System, and the unexpected absence of two-point angular corellations especially outside the region of the sky most contaminated by the Galaxy. We discuss these findings in relation to expectations from standard inflationary cosmology. This paper is adapted from a talk given by one of us (GDS) at the SEENET-2011 meeting in Augus…
The hot gas in clusters of galaxies creates a distinctive spectral distortion in the cosmic microwave background (CMB) via the Sunyaev-Zel'dovich (SZ) effect. The spectral signature of the SZ can be used to measure the CMB temperature at cluster redshift ($T_{\rm CMB}(z)$) and to constrain the monopole of the y-type spectral distortion of the CMB spectrum. In this work, we start showing the measurements of $T_{\rm CMB}(z)$ for a sample extracted from the Second Catalog of galaxy clusters produced by Planck (PSZ2) and containing 75 clusters selected from CHEX-MATE. Then we show the forecasts fo…
Small scale CMB angular power spectrum contains not only primordial CMB information but also many contaminants coming from secondary anisotropies. Most of the latter depend on the cosmological model but are often marginalised over. We propose a new analysis of the SPT data focusing on the cosmological contribution of the thermal Sunyaev Zel'dovich (tSZ) effect. We model the tSZ angular spectrum with the halo model and train a random forest algorithm to speed up its computation. We show that using the cosmological information of the tSZ on top of the primordial CMB one contained in SPT data bri…
We demonstrate that for a cosmic variance limited experiment, CMB E polarization alone places stronger constraints on cosmological parameters than CMB temperature. For example, we show that EE can constrain parameters better than TT by up to a factor 2.8 when a multipole range of l=30-2500 is considered. We expose the physical effects at play behind this remarkable result and study how it depends on the multipole range included in the analysis. In most relevant cases, TE or EE surpass the TT based cosmological constraints. This result is important as the small scale astrophysical foregrounds a…
Towards precision cosmology with Void x CMB correlations (II): Impact of mock catalogs on the Void x CMB lensing signal
Instituto de Astrofísica de Canarias（加那利群岛天体物理研究所）；Universidad de La Laguna（拉戈纳大学）；MTA–CSFK Lendület “Momentum” Large-Scale Structure (LSS) Research Group（匈牙利科学院-塞格德大学“动量”大尺度结构研究组）；Konkoly Observatory, HUN-REN Research Centre for Astronomy and Earth Sciences（孔科利天文台，匈牙利研究与创新网络地球与天文学研究中心）；CPPM, Aix-Marseille Université, CNRS/IN2P3（地中海粒子与核物理中心，艾克斯-马赛大学，法国国家科学研究中心/法国国家核与粒子物理研究所）；Princeton University（普林斯顿大学）；California Institute of Technology（加州理工学院）
研究通过分析模拟目录对Void x CMB引力透镜信号的影响，探讨了未来宇宙学约束的潜力，发现该信号对模拟目录的依赖性较低，预计罗马任务结合现有和未来CMB观测将显著提高信号噪声比。
Amongst standard model parameters that are constrained by cosmic microwave background (CMB) observations, the optical depth $τ$ stands out as a nuisance parameter. While $τ$ provides some crude limits on reionization, it also degrades constraints on other cosmological parameters. Here we explore how 21 cm cosmology---as a direct probe of reionization---can be used to independently predict $τ$ in an effort to improve CMB parameter constraints. We develop two complementary schemes for doing so. The first uses 21 cm power spectrum observations in conjunction with semi-analytic simulations to pred…
The cosmic microwave background (CMB) has been a treasure trove for cosmology. Over the next decade, current and planned CMB experiments are expected to exhaust nearly all primary CMB information. To further constrain cosmological models, there is a great benefit to measuring signals beyond the primary modes. Rayleigh scattering of the CMB is one source of additional cosmological information. It is caused by the additional scattering of CMB photons by neutral species formed during recombination and exhibits a strong and unique frequency scaling ($\propto ν^4$). We will show that with sufficien…
We discuss detectability of the nonlinear growth of the large-scale structure in the cosmic microwave background (CMB) lensing. Lensing signals involved in CMB anisotropies have been measured from multiple CMB experiments, such as Atacama Cosmology Telescope (ACT), Planck, POLARBEAR, and South Pole Telescope (SPT). Reconstructed lensing signals are useful to constrain cosmology via their angular power spectrum, while detectability and cosmological application of their bispectrum induced by the nonlinear evolution are not well studied. Extending the analytic estimate of the galaxy lensing bispe…
We demonstrate that the cosmic microwave background (CMB) temperature-polarization cross-correlation provides accurate and robust constraints on cosmological parameters. We compare them with the results from temperature or polarization and investigate the impact of foregrounds, cosmic variance, and instrumental noise. This analysis makes use of the Planck high-multipole HiLLiPOP likelihood based on angular power spectra, which takes into account systematics from the instrument and foreground residuals directly modelled using Planck measurements. The temperature-polarization correlation (TE) sp…
We measure the cross-correlation of Atacama Cosmology Telescope CMB lensing convergence maps with quasar maps made from the Sloan Digital Sky Survey DR8 SDSS-XDQSO photometric catalog. The CMB lensing-quasar cross-power spectrum is detected for the first time at a significance of 3.8 sigma, which directly confirms that the quasar distribution traces the mass distribution at high redshifts z>1. Our detection passes a number of null tests and systematic checks. Using this cross-power spectrum, we measure the amplitude of the linear quasar bias assuming a template for its redshift dependence, and…
Since the measurements of COBE/FIRAS in the mid-90's we know that the energy spectrum of the cosmic microwave background (CMB) is extremely close to that of a perfect blackbody at an average temperature T0~2.726K. However, a number of early-universe processes are expected to create CMB spectral distortions - departures of the average CMB energy spectrum from a blackbody - at a level that is within reach of present-day technology. This provides strong motivation to study the physics of CMB spectral distortions and ask what these small signals might be able to tell us about the Universe we live …
Galaxy angular-power spectrum and autocorrelation functions (ACFs) provide information about the distribution of matter by using galaxy counts as a proxy. In this study, we are going to estimate autocorrelation angular power spectrum and angular autocorrelation function for EMU-ASKAP 5 sigma sources and then compare them with results from NVSS. We will also use SUMSS data to compare ACF results using Landy-Szalay estimator. EMU-ASKAP will provide excellent opportunity to observe universe with high sensitivity and is likely going to observe millions of high redshift sources which will help in s…
The Sunyaev-Zel'dovich (SZ) effect introduces a specific distortion of the blackbody spectrum of the cosmic microwave background (CMB) radiation when it scatters off hot gas in clusters of galaxies. The frequency dependence of the distortion is only independent of the cluster redshift when the evolution of the CMB radiation is adiabatic. Using 370 clusters within the redshift range $0.07\lesssim z\lesssim1.4$ from the largest SZ-selected cluster sample to date from the Atacama Cosmology Telescope, we provide new constraints on the deviation of CMB temperature evolution from the standard model …
Characterizing accurately the polarized dust emission from our Galaxy will be decisive for the quest for the Cosmic Microwave Background (CMB) primordial $B$-modes. The incomplete modeling of its potentially complex spectral properties could lead to biases in the CMB polarization analyses and to a spurious detection of the tensor-to-scalar ratio $r$. Variations of the dust properties along and between lines of sight lead to unavoidable distortions of the spectral energy distribution (SED) that can not be easily anticipated by standard component separation methods. This issue can be tackled usi…
We argue that the anomalous power asymmetry observed in the cosmic microwave background (CMB) may have originated in a cosmic bounce preceding inflation. In loop quantum cosmology (LQC) the big bang singularity is generically replaced by a bounce due to quantum gravitational effects. We compute the spectrum of inflationary non-Gaussianity and show that strong correlation between observable scales and modes with longer (super-horizon) wavelength arise as a consequence of the evolution of perturbations across the LQC bounce. These correlations are strongly scale dependent and induce a dipole-dom…
We forecast the number of galaxy clusters that can be detected via the thermal Sunyaev-Zeldovich (tSZ) signals by future cosmic microwave background (CMB) experiments, primarily the wide area survey of the CMB-S4 experiment but also CMB-S4's smaller delensing survey and the proposed CMB-HD experiment. We predict that CMB-S4 will detect 75,000 clusters with its wide survey of $f_{\rm sky}$ = 50% and 14,000 clusters with its deep survey of $f_{\rm sky}$ = 3%. Of these, approximately 1350 clusters will be at $z \ge 2$, a regime that is difficult to probe by optical or X-ray surveys. We assume CMB…
The non-Gaussianity of inflationary perturbations, as encoded in the bispectrum (or 3-point correlator), has become an important additional way of distinguishing between inflation models, going beyond the linear Gaussian perturbation quantities of the power spectrum. This habilitation thesis provides a review of my work on both the theoretical and the observational aspects of these non-Gaussianities. In the first part a formalism is described, called the long-wavelength formalism, that provides a way to compute the non-Gaussianities in multiple-field inflation. Applications of this formalism t…
Loop quantum cosmology is a conflicted field in which exuberant claims of observability coexist with serious objections against the conceptual and physical viability of its current formulations. This contribution presents a non-technical case study of the recent claim that loop quantum cosmology might alleviate anomalies in observations of the cosmic microwave background.
Cosmological parameter constraints from the CMB power spectra alone suffer several well-known degeneracies. These degeneracies can be broken by numerical artefacts and also a variety of physical effects that become quantitatively important with high-accuracy data e.g. from the Planck satellite. We study degeneracies in models with flat and non-flat spatial sections, non-trivial dark energy and massive neutrinos, and investigate the importance of various physical degeneracy-breaking effects. We test the CAMB power spectrum code for numerical accuracy, and demonstrate that the numerical calculat…
Canada has thriving communities in CMB (cosmic microwave background) studies, cosmology and submillimetre (submm) astronomy, with involvement in many facilities that featured prominently in previous Astronomy Long Range Plans. The standard cosmological model continues to be well fit using a small number of parameters. No one expects this model to be complete and so we need to continue to challenge it with data; moreover, it does not explain how galaxies and other structures form. So, how do we improve the precision of our understanding of structure formation within this model? Wavelengths from…
Mirror dark matter interacting with ordinary matter via photon-mirror photon kinetic mixing can explain the DAMA, CoGeNT and CRESSTII direct detection experiments. This explanation requires kinetic mixing of strength $ε\sim 10^{-9}$. Such kinetic mixing will have important implications for early Universe cosmology. We calculate the additional relativistic energy density at recombination, $δN_{eff} [CMB]$. We also calculate the effects for big bang nucleosynthesis, $δN_{eff} [BBN]$. Current hints that both $δN_{eff} [CMB]$ and $δN_{eff} [BBN]$ are non-zero and positive can be accommodated withi…
We explore synergies between the Nancy Grace Roman Space Telescope and CMB lensing data to constrain dark energy and modified gravity scenarios. A simulated likelihood analysis of the galaxy clustering and weak lensing data from the Roman Space Telescope High Latitude Survey combined with CMB lensing data from the Simons Observatory is undertaken, marginalizing over important astrophysical effects and calibration uncertainties. Included in the modeling are the effects of baryons on small-scale clustering, scale-dependent growth suppression by neutrinos, as well as uncertainties in the galaxy c…
We test the consistency between Planck temperature and polarization power spectra and the concordance model of $Λ$ Cold Dark Matter cosmology ($Λ$CDM) within the framework of Crossing statistics. We find that Planck TT best fit $Λ$CDM power spectrum is completely consistent with EE power spectrum data while EE best fit $Λ$CDM power spectrum is not consistent with TT data. However, this does not point to any systematic or model-data discrepancy since in the Planck EE data, uncertainties are much larger compared to the TT data. We also investigate the possibility of any deviation from $Λ$CDM mod…
The Atacama Cosmology Telescope: A demonstration of CMB lensing measurement from daytime data
University of Cambridge（剑桥大学）；Kavli Institute for Cosmology Cambridge（卡弗里宇宙学剑桥研究所）；Kavli Institute for Particle Astrophysics and Cosmology（卡弗里粒子天体物理与宇宙学研究所）；SLAC National Accelerator Laboratory（斯坦福直线加速器中心）；University of Pennsylvania（宾夕法尼亚大学）；Princeton University（普林斯顿大学）；Cardiff University（卡迪夫大学）
Recent observational progress has led to the establishment of the standard $Λ$CDM model for cosmology. This development is based on different cosmological probes that are usually combined through their likelihoods at the latest stage in the analysis. We implement here an integrated scheme for cosmological probes, which are combined in a common framework starting at the map level. This treatment is necessary as the probes are generally derived from overlapping maps and are thus not independent. It also allows for a thorough test of the cosmological model and of systematics through the consisten…
For the first time, measurements of the cosmic microwave background radiation (CMB) alone favor cosmologies with $w=-1$ dark energy over models without dark energy at a 3.2-sigma level. We demonstrate this by combining the CMB lensing deflection power spectrum from the Atacama Cosmology Telescope with temperature and polarization power spectra from the Wilkinson Microwave Anisotropy Probe. The lensing data break the geometric degeneracy of different cosmological models with similar CMB temperature power spectra. Our CMB-only measurement of the dark energy density $Ω_Λ$ confirms other measureme…
The cosmic microwave background (CMB) photons that scatter off free electrons in the large-scale structure induce a linear polarization pattern proportional to the remote CMB temperature quadrupole observed in the electrons' rest frame. The associated blackbody polarization anisotropies are known as the polarized Sunyaev Zel'dovich (pSZ) effect. Relativistic corrections to the remote quadrupole field give rise to a non-blackbody polarization anisotropy proportional to the square of the transverse peculiar velocity field; this is the kinetic polarized Sunyaev Zel'dovich (kpSZ) effect. In this p…
In the near future, the overlap of the Rubin Observatory Legacy Survey of Space and Time (LSST) and the Simons Observatory (SO) will present an ideal opportunity for joint cosmological dataset analyses. In this paper we simulate the joint likelihood analysis of these two experiments using six two-point functions derived from galaxy position, galaxy shear, and CMB lensing convergence fields. Our analysis focuses on realistic noise and systematics models and we find that the dark energy Figure-of-Merit (FoM) increases by 53% (92%) from LSST-only to LSST+SO in Year 1 (Year 6). We also investigate…
Cosmological models assuming the scale invariance of the macroscopic empty space show an accelerated expansion, without calling for some unknown particles. Several comparisons between models and observations (tests on distances, m-z diagram, Omega_Lambda vs. Omega_m plot, age vs. H_0, H(z) vs. z, transition braking-acceleration) have indicated an impressive agreement {Maeder 2017}. We pursue the tests with the CMB temperatures T(CMB) as a function of redshifts z. CO molecules in DLA systems provide the most accurate excitation temperatures T(exc) up to z ~ 2.7. Such data need corrections for l…
Cosmic Microwave Background (CMB) anisotropy encodes a lot of information about our Universe. In this paper we take the ground-based CMB observations (GCMB), including the South Pole Telescope (SPT), SPTpol and the Atacama Cosmology Telescope Polarimeter (ACTPol), as a new probe to the CMB anisotropy independent of two satellite observations, i.e. Wilkinson Microwave Anisotropy Probe (WMAP) and Planck. The combination of current GCMB data is consistent with WMAP and Planck. In the spatially flat $Λ$CDM model, the Hubble constant is $H_0=69.72\pm 1.63$ km/s/Mpc at $68\%$ confidence level (CL). …
This brief article sums up the possible imprints of loop quantum gravity effects on the cosmological microwave background. We focus on semi-classical terms and show that "Big Bounce" corrections, together with the "pre Big Bounce" state, could modify the observed spectrum.
We explore the significance of noise from thermal Sunyaev-Zel{'}dovich (tSZ) signals for cluster detection using cosmic microwave background (CMB) surveys. The noise arises both from neighboring objects and also from haloes below the detection limit. A wide range of surveys are considered: SPT-SZ, SPTpol, and SPT-3G from the South Pole Telescope; SO-Baseline and SO-Goal configurations for Simons Observatory; CMB-S4's wide area (S4-Wide) and deep (S4-Ultra deep) surveys; and the futuristic CMB-HD experiment. We find that the noise from tSZ signals has a significant impact on CMB-HD and to some …
During this work, an interacting chameleon like scalar field scenario, by considering SNeIa, CMB, BAO and OHD data sets is investigated. In fact, the investigation is realized by introducing an ansatz for the effective dark energy equation of state, which mimics the behaviour of chameleon like models. Based on this assumption, some cosmological parameters including Hubble, deceleration and coincidence parameters in such mechanism are analysed. It is realized that, to estimate the free parameters of a theoretical model, by regarding the systematic errors it better the whole of the above observa…
The Atacama Cosmology Telescope has measured the angular power spectra of microwave fluctuations to arcminute scales at frequencies of 148 and 218 GHz, from three seasons of data. At small scales the fluctuations in the primordial Cosmic Microwave Background (CMB) become increasingly obscured by extragalactic foregounds and secondary CMB signals. We present results from a nine-parameter model describing these secondary effects, including the thermal and kinematic Sunyaev-Zel'dovich (tSZ and kSZ) power; the clustered and Poisson-like power from Cosmic Infrared Background (CIB) sources, and thei…
Unparticle cosmology gives an unconventional outlook on the dark sector of cosmology, increasingly challenging $Λ\mbox{CDM}$ by $H_0$-tension. This model derives from a finite temperature broken conformal symmetry of radiation, described by a non-radiative correction with unknown sign in energy density. This symmetry breaking has a sign ambiguity, in which corrections about the IR fixed point are normal or tachyonic. While the first has been ruled out in a recent study, the latter possesses a late-time temperature $T_c\simeq 4\,T_{CMB}$ associated with $Ω_{\cal U}\simeq 1$ ($Ω_{\cal U} \simeq …
An observational program focused on the high redshift ($2<z<6$) Universe has the opportunity to dramatically improve over upcoming LSS and CMB surveys on measurements of both the standard cosmological model and its extensions. Using a Fisher matrix formalism that builds upon recent advances in Lagrangian perturbation theory, we forecast constraints for future spectroscopic and 21-cm surveys on the standard cosmological model, curvature, neutrino mass, relativistic species, primordial features, primordial non-Gaussianity, dynamical dark energy, and gravitational slip. We compare these constrain…
Bumblebee cosmology: The FLRW solution and the CMB temperature anisotropy
Tsinghua University（清华大学）；Beijing Institute of Mathematical Sciences and Applications（北京国际数学研究中心）；Universitat Politècnica de València（瓦伦西亚理工大学）；Max-Planck-Institute for Extraterrestrial Physics（马克斯·普朗克地外物理研究所）；Peking University（北京大学）；National Astronomical Observatories, Chinese Academy of Sciences（中国科学院国家天文台）
Perturbations from inflation evolve into large scale structure of the late universe, and encode abundant cosmic structure formation physics. We allow freedom in the primordial power spectrum, rather than assuming a power law scale dependence, to study its impact on cosmological parameter determination. Combining various generations of cosmic microwave background (CMB) data and galaxy redshift survey data, we investigate the constraints on reconstruction of the primordial curvature perturbation power spectrum and the late time cosmology, especially the sum of neutrino masses. We quantify how ea…
Massive gravity in the presence of doubly coupled matter field via en effective composite metric yields an accelerated expansion of the universe. It has been recently shown that the model admits stable de Sitter attractor solutions and could be used as a dark energy model. In this work, we perform a first analysis of the constraints imposed by the SNIa, BAO and CMB data on the massive gravity model with the effective composite metric and show that all the background observations are mutually compatible at the one sigma level with the model.
With the advent of a new generation of cosmological experiments that will provide high-precision measurements of the cosmic microwave background (CMB) and galaxies in the large-scale structure, it is pertinent to examine the potential of performing a joint analysis of multiple cosmological probes. In this paper, we study the cosmological information content contained in the one-loop power spectra and tree bispectra of galaxies cross-correlated with CMB lensing. We use the FFTLog method to compute angular correlations in spherical harmonic space, applicable for wide angles that can be accessed …
We present a measurement of the gravitational lensing of the Cosmic Microwave Background (CMB) temperature and polarization fields obtained by cross-correlating the reconstructed convergence signal from the first season of ACTPol data at 146 GHz with Cosmic Infrared Background (CIB) fluctuations measured using the Planck satellite. Using an overlap area of 206 square degrees, we detect gravitational lensing of the CMB polarization by large-scale structure at a statistical significance of 4.5 sigma. Combining both CMB temperature and polarization data gives a lensing detection at 9.1 sigma sign…
In the inhomogeneous Universe, the cosmological conversion of dark photons into ordinary photons (and vice versa) may happen at a great number of resonance redshifts. This alters the CMB observed energy spectrum and degree of small-scale anisotropies. We utilize results from the EAGLE simulation to obtain the conversion probability along random line-of-sights to quantify these effects. We then apply our results to the case where dark photons are sourced by dark matter decay and their high-redshift conversion into ordinary photons modify the global 21 cm signal expected from the cosmic dawn era…
We forecast the constraints on the parameters of neutrino physics with the constructions of Cosmic Microwave Background (CMB) temperature, E-mode polarization and lensing spectra for the ground-based Ali Cosmic Microwave Background Polarization Telescope (AliCPT). To implement the forecast calculations, we perform numerical simulations which show that AliCPT would yield the result $σ(N_{\mathrm{eff}})=0.42$ and $σ(M_ν)=0.18$ for the first year observation. Moreover, we investigate how the instrumental parameters, such as noise level, full width at half maxima (FWHM), and sky coverage can affec…
The foundation of modern cosmology relies on the so-called cosmological principle which states an homogeneous and isotropic distribution of matter in the universe on large scales. However, recent observations, such as the temperature anisotropy of the cosmic microwave background (CMB) radiation, the motion of galaxies in the universe, the polarization of quasars and the acceleration of the cosmic expansion, indicate preferred directions in the sky. If these directions have a cosmological origin, the cosmological principle would be violated, and modern cosmology should be reconsidered. In this …
One working hypothesis on which analyses of cosmological data are based is the zero ensemble mean hypothesis, which is related to the statistical homogeneity of cosmological perturbations. This hypothesis, however, should be tested by observational data in the current era of precision cosmology. Herein, we test the hypothesis by analyzing recent, foreground-reduced cosmic microwave background (CMB) maps, combining the spherical harmonic coefficients of the masked CMB temperature anisotropies in such a way that the combined variables can be treated as statistically independent samples. We find …
