Future observations of the large-scale structure have the potential to investigate cosmological models with a high degree of complexity, including the properties of gravity on large scales, the presence of a complicated dark energy component, and the addition of neutrinos changing structures on small scales. Here we study Horndeski theories of gravity, the most general minimally coupled scalar-tensor theories of second order. While the cosmological background evolution can be described by an effective equation of state, the perturbations are characterised by four free functions of time. We consider a specific parametrisation of these functions tracing the dark energy component. The likelihood of the full parameter set resulting from combining cosmic microwave background primary anisotropies including their gravitational lensing signal, tomographic angular galaxy clustering and weak cosmic shear, together with all possible non-vanishing cross-correlations is evaluated; both with the Fisher-formalism as well as without the assumption of a specific functional form of the posterior through Monte-Carlo Markov-chains (MCMCs). Our results show that even complex cosmological models can be constrained and could exclude variations of the effective Newtonian gravitational coupling larger than 10\% over the age of the Universe. In particular, we confirm strong correlations between parameter groups. Furthermore, we find that the expected contours from MCMC are significantly larger than those from the Fisher analysis even with the vast amount of signal provided by stage IV experiments, illustrating the importance of a proper treatment of non-Gaussian likelihoods and the high level of precision needed for unlocking the sensitivity on gravitational parameters.
As observational evidence increasingly consolidates the case for a cosmological constant being the source of the Universe's accelerated expansion, the question whether, and if so, how well, future experiments could detect deviations from this standard scenario is raised with urgency. Assuming a dark energy component different from a cosmological constant, the observable effects in general include gravitational clustering described by the fluid's (rest-frame) speed of sound. We employ 3d weak cosmic shear, a proposed method to take advantage of the full three-dimensional information inherent to…
Standard candles can probe the evolution of dark energy in a large redshift range. But the cosmic opacity can degrade the quality of standard candles. In this paper, we use the latest observations, including type Ia supernovae (SNe Ia) from JLA sample and Hubble parameters, to probe the opacity of the universe. In order to avoid the cosmological dependence of SNe Ia luminosity distances, a joint fitting of the SNe Ia light-curve parameters, cosmological parameters and opacity is used. In order to explore the cosmic opacity at high redshifts, the latest gamma-ray bursts (GRBs) are used. At high…
We show that a combined analysis of CMB anisotropy power spectra obtained by the Planck satellite and luminosity distance data simultaneously excludes a flat universe and a cosmological constant at $99 \%$ CL. These results hold separately when combining Planck with three different datasets: the two determinations of the Hubble constant from Riess et al. 2019 and Freedman et al. 2020, and the Pantheon catalog of high redshift supernovae type-Ia. We conclude that either LCDM needs to be replaced by a different model, or else there are significant but still undetected systematics. Our result cal…
We investigate the relationship between the cosmic curvature and the model of dark energy (hereafter DE) with the recent Type Ia supernovae (hereafter SNe Ia) data, i.e., the Pantheon sample including 1048 SNe Ia with $0.01 < z < 2.3$. We obtain the measurements of the dimensionless spatial curvature density today, i.e., $Ω_{k0} = -0.062^{+0.189}_{-0.169}, -0.004^{+0.228}_{-0.134}, 0.127^{+0.280}_{-0.276}$ and $0.422^{+0.213}_{-0.338}$ at 68\% confidence level (CL), respectively, in the scenarios of $Λ$CDM, $ϕ$CDM (i.e., scalar field dark energy), $ω$CDM and $ω_0ω_a$CDM models. In the scenario…
In this article, we do a thorough investigation of the competency of the forthcoming Cosmic Microwave Background (CMB) and Galaxy surveys in probing the features in the primordial power spectrum. Primordial features are specific model-dependent corrections on top of the standard power-law inflationary power spectrum; the functional form being given by different inflationary scenarios. Signature of any significant departure from the feature-less power spectrum will enable us to decipher the intricacies of the inflationary Universe. Here, we delve into three major yet distinct features, namely, …
Kolmogorov's statistic is used for the analysis of properties of perturbations in the Cosmic Microwave Background signal. We obtain the maps of the Kolmogorov stochasticity parameter for W and V band temperature data of WMAP which are differently affected by the Galactic disk radiation and then we model datasets with various statistic of perturbations. The analysis shows that the Kolmogorov's parameter can be an efficient tool for the separation of Cosmic Microwave Background from the contaminating radiations due to their different statistical properties.
Understanding the internal structure and spatial distribution of cosmic voids is crucial when considering them as probes of cosmology. We present recent advances in modeling void density- and velocity-profiles in real space, as well as void two-point statistics in redshift space, by examining voids identified via the watershed transform in state-of-the-art $Λ$CDM n-body simulations and mock galaxy catalogs. The simple and universal characteristics that emerge from these statistics indicate the self-similarity of large-scale structure and suggest cosmic voids to be among the most pristine objec…
We describe and discuss the application of Gumbel statistics, which model extreme events, to WMAP 5-year measurements of the cosmic microwave background. We find that temperature extrema of the CMB are well modelled by the Gumbel formalism and describe tests for Gaussianity that the approach can provide. Comparison to simulations reveals Gumbel statistics to have only weak discriminatory power for the conventional statistic: $f_{NL}<1000$, though it may probe other regimes of non-Gaussianity. Tests based on hemispheric cuts reveal interesting alignment with other reported CMB anomalies. The ap…
Commonly used methods to decompose E- and B-modes in cosmic shear, namely the aperture mass dispersion and the E/B-mode shear correlation function, suffer from incomplete knowledge of the two-point correlation function (2PCF) on very small and/or very large scales. The ring statistics, the most recently developed cosmic shear measure, improves on this issue and is able to decompose E- and B-modes using a 2PCF measured on a finite interval. First, we improve on the ring statistics' filter function with respect to the signal-to-noise ratio. Second, we examine the ability of the ring statistics t…
We introduce new statistical methods for the study of cosmic voids, focusing on the statistics of largest size voids. We distinguish three different types of distributions of voids, namely, Poisson-like, lognormal-like and Pareto-like distributions. The last two distributions are connected with two types of fractal geometry of the matter distribution. Scaling voids with Pareto distribution appear in fractal distributions with box-counting dimension smaller than three (its maximum value), whereas the lognormal void distribution corresponds to multifractals with box-counting dimension equal to t…
Ultracompact Minihalos (UCMHs) have been proposed as a type of dark matter sub-structure seeded by large-amplitude primordial perturbations and topological defects. UCMHs are expected to survive to the present era, allowing constraints to be placed on their cosmic abundance using observations within our own Galaxy. Constraints on their number density can be linked to conditions in the early universe that impact structure formation, such as increased primordial power on small scales, generic weak non-Gaussianity, and the presence of cosmic strings. We use new constraints on the abundance of UCM…
The Dark Ages, probed by the redshifted 21-cm signal, is the ideal epoch for a new rigorous test of the standard LCDM cosmological model. Divergences from that model would indicate new physics, such as dark matter decay (heating) or baryonic cooling beyond that expected from adiabatic expansion of the Universe. In the early Universe, most of the baryonic matter was in the form of neutral hydrogen (HI), detectable via its ground state's spin-flip transition. A measurement of the redshifted 21-cm spectrum maps the history of the HI gas through the Dark Ages and Cosmic Dawn and up to the Epoch of…
The Fourier transformation is an effective and efficient operation of Gaussianization at the one-point level. Using a set of N-body simulation data, we verified that the one-point distribution functions of the dark matter momentum divergence and density fields closely follow complex Gaussian distributions. The one-point distribution function of the quotient of two complex Gaussian variables is introduced and studied. Statistical theories are then applied to model one-point statistics about the growth of individual Fourier mode of the dark matter density field, which can be obtained by the rati…
In this work, by investigating the low temperature behaviour of a scalar field around a cosmic string, and assuming stable thermodynamic equilibrium, it is shown that the coupling parameter of the field with curvature must be restricted to a certain range of values whose bounds are determined by the deficit angle of the associated conical geometry.
We present new numerical tools to analyse cosmic void catalogues, implemented inside the CosmoBolognaLib, a large set of Open Source C++/Python numerical libraries. The CosmoBolognaLib provides a common numerical environment for cosmological calculations. This work extends these libraries by adding new algorithms for cosmological analyses of cosmic voids, covering the existing gap between theory and observations. We implemented new methods to model the size function of cosmic voids, in both observed and simulated samples of dark matter and biased tracers. Moreover, we provide new numerical too…
Stereology allows shifting from the 3D distribution of the volumes of Poissonian Voronoi Diagrams to their 2D cross-sections. The basic assumption is that the 3D statistics of the volumes of the voids in the local Universe has a distribution function of the gamma-type. The standard rule of conversion from 3D volumes to 2D circles, adopting the standard rules of stereology, produces a new probability density function of the radii which contains the Meijer $G$-function. A non-Poissonian distribution of volumes is also considered. The distribution of the 3D radii of the Sloan Digital Sky Survey D…
In this work, we explore the evolution of the dark energy equation of state ω by using Chevalliear-PolarskiLinder (CPL) parametrization and the binned parametrizations. For binned parametrizations, we adopt three methods to choose the redshift interval: I. Ensure that "Δz = const", where Δz is the width of each bin; II.Ensure that "nΔz = const", where n is the number of SNIa in each bin; III. Treat redshift discontinuity points as models parameters, i.e. "free Δz". For observational data, we adopt JLA type Ia supernova (SNIa) samples, SDSS DR12 data, and Planck 2015 distance priors. In particu…
We propose a novel technique to probe the expansion history of the Universe based on the clustering statistics of cosmic voids. In particular, we compute their two-point statistics in redshift space on the basis of realistic mock galaxy catalogs and apply the Alcock-Paczynski test. In contrast to galaxies, we find void auto-correlations to be marginally affected by peculiar motions, providing a model-independent measure of cosmological parameters without systematics from redshift-space distortions. Because only galaxy-galaxy and void-galaxy correlations have been considered in these types of s…
Making cosmological inferences from the observed galaxy clustering requires accurate predictions for the mean clustering statistics and their covariances. Those are affected by cosmic variance -- the statistical noise due to the finite number of harmonics. The cosmic variance can be suppressed by fixing the amplitudes of the harmonics instead of drawing them from a Gaussian distribution predicted by the inflation models. Initial realizations also can be generated in pairs with 180 degrees flipped phases to further reduce the variance. Here, we compare the consequences of using paired-and-fixed…
In this article, we extend previous studies based on CMB spherical harmonic phases (SHP) to examine the validity of the hypothesis that the temperature field of the CMB is consistent with a Gaussian random field (GRF). The null hypothesis is that the corresponding CMB SHP are independent and identically distributed in terms of a uniform distribution in the interval [0, 2$π$] \citep{1986ApJ...304...15B,2013rossmanith}. We devise a new model-independent method where we use ordered and non-parametric Rao's statistic, based on sample arc-lengths to comprehensively test uniformity and independence …
The correlation between radio spectral index and redshift has long been used to identify high redshift radio galaxies, but its cause is unknown. Traditional explanations invoke either $(i)$ intrinsic relations between spectral index and power, $(ii)$ environmental differences at high redshift, or $(iii)$ higher inverse Compton losses due to the increased photon energy density of the cosmic microwave background. In this paper we investigate whether the increased inverse Compton losses alone can cause the observed spectral index - redshift correlation by using spectral modelling of nearby radio …
We briefly summarize our study on anisotropy of Ultra-High Energy Cosmic-Rays (UHECRs), in which we define a statistics that measures the correlation between UHECRs and Large Scale Structure (LSS). We also comment here on recently published paper by Koers and Tinyakov that compared our statistics to improved KS statistics.
Starting from the geometrical concept of a 4-dimensional de-Sitter configuration of spheres in Euclidean 3-space and modelling voids in the Universe as spheres, we show that a uniform distribution over this configuration space implies a power-law for the void number density which is consistent with results from the excursion set formalism and with data, for an intermediate range of void volumes. The scaling dimension of the large scale structure can be estimated as well. We also discuss the effect of restricting the survey geometry on the void statistics. This work is a new application of de-S…
Building upon the recent pioneering work by Mazenko and by Das and Mazenko, we develop a microscopic, non-equilibrium, statistical field theory for initially correlated canonical ensembles of classical microscopic particles obeying Hamiltonian dynamics. Our primary target is cosmic structure formation, where initial Gaussian correlations in phase space are believed to be set by inflation. We give an exact expression for the generating functional of this theory and work out suitable approximations. We specify the initial correlations by a power spectrum and derive general expressions for the co…
The formalism to compute the geometrical and topological one-point statistics of mildly non-Gaussian 2D and 3D cosmological fields is developed. Leveraging the isotropy of the target statistics, the Gram-Charlier expansion is reformulated with rotation invariant variables. This formulation allows us to track the geometrical statistics of the cosmic field to all orders. It then allows us to connect the one point statistics of the critical sets to the growth factor through perturbation theory, which predicts the redshift evolution of higher order cumulants. In particular, the cosmic non-linear e…
