We investigate recent reports of a suppression in the growth rate of cosmic structures inferred from analyses of the [fσ8](z) dataset. To address this issue, we explore the hypothesis that the evolution of matter clustering is more accurately described within the framework of scale-dependent modified gravity. We perform a joint analysis of [fσ8](z), cosmic chronometer H(z) measurements, luminosity distance data, and CMB observations using Markov Chain Monte Carlo techniques to constrain the parameters of a scale-dependent cosmological model and investigate its impact on the evolution of [fσ8](z). Our results indicate that the suppression of the growth rate of large-scale structures is more pronounced during the matter-dominated era than in the dark-energy-dominated epoch. We find evidence for scale-dependent growth at a statistical significance of 2.2 σ. In addition, we constrain the S8 parameter and find it to be consistent with the value inferred from the CMB observations of the Planck Collaboration. Overall, our analysis shows that k-dependent growth models provide a viable explanation for the observed clustering of matter without exacerbating the current cosmological tensions.

The Hubble-Lemaître Law provides a satisfactory description of the universe’s dynamics for low red- shifts and reveals insights about its expansion rate. However, at higher redshift values, additional incorporation of the Friedmann equations within the framework of General Relativity is necessary. This project focuses on analyzing large-scale structures of the local universe, specifically at low redshifts, using Hubble-Lemaître diagrams. The goal is to understand the dynamics of universe expansion by studying the Hubble constant independently of specific cosmological models. By utilizing the ALFALFA catalog, the Hubble constant is measured, considering potential systematic effects and using velocity reference frames that minimize peculiar velocity influences. Transformations of frames of reference, e.g. Local Group and CMB frames, and statistical methods were employed to achieve a more accurate determination of the Hubble constant. Within a 1 sigma confidence level, the values for the Hubble constant are equivalent between the two hemispheres. The findings of this work, which contributed to the publication of an article, shed light on the precise measurement of the Hubble constant and its implications.

In this study we investigate potential large-angle anisotropies in the angular distribution of the cosmological parameters H-0 (the Hubble constant) and Omega(m) (the matter density) in the flat-Lambda CDM framework, using the Pantheon+SH0ES supernovae catalog. For this we perform a directional analysis by dividing the celestial sphere into a set of directions, and estimate the best-fit cosmological parameters across the sky using a MCMC approach. Our results show a dominant dipolar pattern for both parameters in study, suggesting a preferred axis in the universe expansion and in the distribution of matter. However, we also found that for z greater than or similar to 0.015, this dipolar behavior is not statistically significant, confirming the expectation -in the Lambda CDM scenario- of an isotropic expansion and a uniform angular distribution of matter (both results at 1 sigma confidence level). Nevertheless, for nearby supernovae, at distances less than or similar to 60 Mpc or z less than or similar to 0.015, the peculiar velocities introduce a highly significant dipole in the angular distribution of H-0. Furthermore, we perform various robustness tests that support our findings, and consistency tests of our methodology.

We investigate and update observational constraints on cosmological parameters within the Λ CDM and dynamical dark energy frameworks, using a new compilation of the transverse (or 2D) BAO data, measurements that provide a relatively model-independent estimate of the BAO angular scale at a given redshift. Firstly, we assess the consistency of this compilation with CMB-Planck data and recent BAO results from the DESI collaboration. After confirming minimal tension with CMB data, we perform a series of joint analyses combining CMB data with the 2D BAO compilation, as well as with several recent Type Ia supernova (SNIa) samples. In all cases, we compare the constraining power of the 2D BAO data with that of DESI DR2 data (3D BAO). Our results indicate that combining 2D BAO with CMB and SNIa data provides observational constraints that are in agreement with those obtained using DESI DR2 data. Although the precision of DESI DR2 results remains higher, as expected due to the more accurate 3D measurements, the 2D BAO compilation combined with other probes yields strong constraints. For example, in the Λ CDM context, we find (CMB + 2D BAO): H_0 = 68.16^+0.41_-0.37 km s^-1 Mpc^-1 and Σ m_ν < 0.081 eV (95

We investigate the quasar clustering in the QuCatS photometric catalog, constructed from the fourth data release of the Southern Photometric Local Universe Survey (S-PLUS). The quasar sample for this study consists of 23,402 quasars, spanning the redshift interval 1.1 ≤ z_ phot≤ 2.6, which we divided into four bins for our tomographic analyses. In each bin, we measured the two-point angular correlation function and compared it with theoretical predictions for the clustering of dark matter in the flat-ΛCDM cosmological model. We then estimate the effective linear bias in each bin that best fits the data, obtaining b_Q(z_ eff=1.26)=2.17^+0.30_-0.35, b_Q(z_ eff=1.63)=2.67^+0.36_-0.42, b_Q(z_ eff=2.04)=3.29^+0.52_-0.62, and b_Q(z_ eff=2.38)=4.05^+0.71_-0.86. These measurements are consistent with previous analyses in the literature. Moreover, the evolution of the bias agrees well with the b(z) parameterization proposed by . Our measurements constitute the first cosmological study of the tomographic clustering of photometric quasars provided by the S-PLUS dataset, contributing to the mapping of the evolution of linear bias and paving the way for future analyses of data releases with larger datasets. In addition, our study also serves as a consistency test for the calibration procedure of the photometric redshift probability distributions of the quasars in the QuCatS catalog.

We employ a model-independent approach in both the correlation function estimation and the angular BAO feature estimation by computing the angular two-point correlation function. First, we conducted a series of tests to the available DESI tracers to check their representativeness to angular clustering; the result was that, considering the completeness of the first data release across the footprint, we could only make use of the BGS sample for the effective redshifts 0.21 (BGS1) and 0.25 (BGS2). For a reliable analysis in such low redshift, we consider Lagrangian Perturbation Theory at first order on our mocks, which approximately reproduces the expected non-linearities, and generate the corresponding random catalogues. We use a purely statistical method to correct the projection effects and find that our results show reasonable agreement with the $θ_{\rm BAO}$ expected by the CPL parameters obtained by DESI DR1, being BGS1 $11.78 \pm 1.12$ degrees and BGS2 $11.81 \pm 1.20$ degrees. This means a tension at the $1.5σ$ ($2.6σ$) level for BGS1 (BGS2) CPL parametrization, while a $2σ$ ($3.3σ$) discrepancy within the predicted by $Λ$CDM. We conclude that, with the current sample available, the use of an angular correlation function serving as the BAO probe, although prefers the CPL parametrization, does not provide conclusive results regarding the best cosmological model.

Aims. We investigated the large-angle distribution of the gamma-ray bursts (GRBs) from the updated FERMI/GBM catalog to probe the statistical isotropy of these astrophysical transient events. We also studied the angular distribution of the GRB fluence as a way to explore whether this radiative feature shows some preferred direction on the sky that suggest their origin. Methods. Our model-independent approach performed a directional analysis of the updated FERMI/GBM catalog. The statistical significance of our results is obtained by comparison with a large set of statistically isotropic samples of cosmic objects, with the same features of the FERMI data. Results. Our analyses confirm that the angular distribution of the FERMIGRB is statistically isotropic on the celestial sphere. Moreover, analyzing the directional distribution of the FERMIGRB fluence, that is, the median GRB fluence in a set of directions that scans the celestial sphere, we found that this astrophysical property exhibits a net dipolar structure with a directional preference for latitudes near the Galactic plane. However, additional studies show that this directional preference is not correlated with the Milky Way Galactic plane, which suggests that the GRB dataset, and its fluence dipolar structure, are extra-Galactic in origin. Interestingly, the analyses of the BATSE Channel 4 fluence data, that is, those GRBs from BATSE with energy > 300 keV, reveal that its dipole direction is very well aligned with the cosmic microwave background dipole.

Transverse Baryon Acoustic Oscillation (BAO) measurements offer a robust geometric probe of the Universe expansion, presenting minimal dependence on fiducial cosmological models. In this work, we analyze the SDSS-DR16 quasar catalog to search for the 2D BAO signal in the unexplored redshift interval 1.5 ≤ z ≤ 2.0. Performing a fine tomographic analysis in 50 thin disjoint redshift shells (Δz = 0.01), to suppress line-of-sight projection smearing, and incorporating a full analytical covariance matrix, we detect the acoustic peak in two uncorrelated redshift shells: θ_ BAO = 1.911^∘± 0.062^∘ and θ_ BAO = 1.727^∘± 0.081^∘ centered at z_ eff = 1.725 and z_ eff = 1.775, with statistical significances of 3.4 σ and 3.0 σ, respectively. By introducing a dimensionless shift parameter α in our empirical parameterization procedure, we then obtain two scaled angular diameter distances: D_A/r_d = 11.00 ± 0.36 at z_ eff=1.725 and D_A/r_d = 11.96 ± 0.56 at z_ eff=1.775. Incorporating these two novel data points into a literature compilation of 16 transverse BAO measurements, we perform a flat-ΛCDM parameter estimation, obtaining Ω_m,0 = 0.41 ± 0.06 and h r_d = 99.3 ± 2.0 Mpc. Our measurements successfully bridge a significant observational gap at high redshift, which remain highly consistent with the constraints reported by the Planck and DESI collaborations, demonstrating the potential of quasar tomographic surveys for dynamical dark energy studies.

We test the validity of the cosmic distance duality relation (CDDR) by combining angular diameter distance and luminosity distance measurements from recent cosmological observations. For the angular diameter distance, we use data from transverse baryon acoustic oscillations and galaxy clusters. On the other hand, the luminosity distance is obtained from Type Ia supernovae in the Pantheon+ sample and from quasar catalogs. To reduce the large dispersion in quasar luminosity distances, we apply a selection criterion based on their deviation from the ΛCDM model and implement a binning procedure to suppress statistical noise. We reconstruct the CDDR using Gaussian Processes, a non-parametric supervised machine learning method. Our results show no significant deviation from the CDDR within the 2σ confidence level across the redshift range explored, supporting its validity even at high redshifts.

The standard model of cosmology describes the matter fluctuations through the matter power spectrum, where sigma 8 equivalent to sigma 8,0 equivalent to sigma 8(z=0), defined at the scale of 8h-1 Mpc, acts as a normalization parameter. Currently, the literature reports measurements of sigma 8 analysing different cosmic tracers, where some of these results were obtained assuming a fiducial cosmology. In this study, we measure, in a model-independent approach, the matter fluctuations in the Local Universe using H i extragalactic sources mapped by the ALFALFA survey. Our analyses allow us to test the standard cosmological model under extreme conditions in the highly non-linear Local Universe, quantifying the amplitude of the matter fluctuations there. Our work directly measures sigma 8 using the three-dimensional distances of the H i sources determined by the ALFALFA survey without assuming a fiducial cosmology, resulting in a robust model-independent measurement of sigma 8. Our methodology involves the construction of suitable mock catalogues to simulate the large-scale structure features observed in the data, applying the two-point correlation function, and making use of Markov chain Monte Carlo methods to estimate the parameters. Analysing these data, we measure sigma 8=0.78 +/- 0.04 for h=0.6727, sigma 8=0.80 +/- 0.05 for h=0.698, and sigma 8=0.83 +/- 0.05 for h=0.7304. Considering the data pairs (sigma 8,H0) from the Planck cosmic microwave background (CMB) and Atacama Cosmology Telescope (ACT) CMB-lensing analyses, our measurement agrees with them within 1 sigma confidence level. From a model-independent perspective, we find that the scale where the matter fluctuation is 1 is R=7.2 +/- 1.5 Mpc.

We present a model-independent estimate of the angular homogeneity scale in the Local Universe by analysing data from the Southern Photometric Local Universe Survey (S-PLUS). Two complementary estimators are employed: (i) a parametric approach fitting the power-law of the two-point angular correlation function, which yields the homogeneity scale θ_H = 9.01_-3.61^+8.43 deg; and (ii) a non-parametric fractal correlation dimension method, computing 𝒟_2(θ) directly from the correlation function, which results in θ_H = 6.28_-4.43^+8.72 deg. From the mock catalogues generated with the GLASS algorithm, we find that the estimates from both methods are within 1 σ of the median values obtained by applying both methodologies to the mocks. The transition scale to homogeneity, according to the ΛCDM model, is defined for matter, i.e. b = 1. Measurements of this scale with observational data clearly depends on the cosmic tracer analysed, and a calibration is necessary. Our study with blue galaxies, with bias b ≃ 1, provides a suitable estimate for comparison. Indeed, the results obtained in both approaches are compared with the value expected in the ΛCDM model, obtaining a good concordance.

The DESI collaboration just obtained a set of precise BAO measurements, that combined with CMB and SNIa datasets show that the ω_0 ω_aCDM model is preferred over ΛCDM, at more than 4 σ, to describe the dynamics of the expanding Universe. This raises the question whether this model also suitably describes the clumpy Universe. Also lately, detailed analyses of diverse cosmic tracers resulted in a new dataset of measurements of an observable from the clumpy Universe: σ_8(z), spanning a high-redshift data z ∈ [0.013, 3.8]. In this work we use this dataset of 15 σ_8(z_i) measurements to study the viability of the ω_0 ω_aCDM cosmological model to explain the clustered Universe. Our analyses compare the ω_0 ω_aCDM model with the σ_8(z) function reconstructed from the data points using Gaussian Process. Moreover, we perform a similar evaluation of the ΛCDM model considering Planck and DESI best-fit parameters. In addition, we implemented robustness tests regarding Gaussian Process reconstruction to support our results.

Several models based on General Relativity and Modified Gravity aim to reproduce the observed universe with precision comparable to the flat-ΛCDM cosmological model. In this study, we investigate the consistency of some of these models with current high-redshift cosmic data, assessing their ability to simultaneously describe both the background expansion and matter clustering, using measurements of the Hubble parameter H(z), the luminosity distance D_L(z), and the growth rate of structures [fσ_8](z) through parametric and non-parametric methods. Our results indicate that background observables alone offer limited capacity to distinguish between models, while the inclusion of growth of structures data proves useful in revealing deviations, even if small. An F(Q) model, the non-flat ΛCDM and the ωCDM emerge as alternatives well supported by data, closely matching the growth data and showing performance comparable to ΛCDM, as revealed by the Akaike Information Criterion. In contrast, F(R) models are strongly disfavored compared to ΛCDM and F(Q). However, according to the Bayesian Information Criterion, ΛCDM remains the preferred model among the models analysed. These analyses illustrate the usefulness of both parametric and non-parametric approaches to explore the observational viability of alternative cosmological models.

In this work, we perform a statistical inference of the classical background law governing the evolution of the temperature of the cosmic microwave background radiation (CMB), given by TCMB(z)=T0(1+z). To this end, we employ Gaussian Process (GP) regression techniques to reconstruct the temperature evolution based on two observational datasets: (i) CMB–Sunyaev-Zel'dovich (SZ) cluster measurements and (ii) CMB–interstellar medium (ISM) interaction data. Our analysis reveals interesting results that may suggest potential deviations from the standard temperature-redshift relation, particularly at low redshifts (z<0.5), where discrepancies up to ∼2σ are observed. Additionally, we identify a mild but noteworthy tension, also at the ∼2σ level, between our GP inferred value of the present-day CMB temperature, TCMB(z=0), and the precise direct measurement from the COBE/FIRAS experiment. We also explore possible phenomenological implications of our findings, including interpretations associated with possible variations in fundamental constants, such as the fine-structure constant α, which could provide a physical explanation for the observed deviations at low redshift.

Understanding the large-scale structure of the Universe requires analyses of cosmic clustering and its evolution over time. In this work, we investigate the clustering properties of Sloan Digital Sky Survey blue galaxies, which are excellent tracers of dark matter, along two distinct epochs of the Universe, utilizing estimators like the two-point angular correlation function (2PACF), the angular power spectra, among others. Considering a model-independent approach, we perform analyses in two disjoint redshift shells, 0 ≤ z < 0.06 and 0.06 ≤ z < 0.12, to investigate the distribution of large cosmic structures. Using Bayesian inference methods, we constrain the parameter that quantifies the galaxy clustering in the 2PACF, enabling us to perform comparisons among different regions on the sky and between different epochs in the Universe regarding the gravitational action on matter structures. Our analyses complement previous efforts to map large-scale structures in the Local Universe. In addition, this study reveals differences regarding the clustering of large cosmic structures, comparing two epochs of the Universe, and analyses done with diverse estimators. Results reveal, clearly, distinct evolutionary signatures between the two redshift shells. Moreover, we had the opportunity to test the concordance cosmological model under extreme conditions in the highly nonlinear Local Universe, computing the amplitude of the angular power spectrum at very small scales. Ultimately, all our analyses serve as a set of consistency tests of the concordance cosmological model, the ΛCDM.

Aims. We study the angular distribution of temperature fluctuations in the cosmic microwave background (CMB) to probe the statistical isotropy of the universe by using precise full-sky CMB data with a model-independent approach. Methods. We investigated the temperature-temperature angular correlations in the four Planck foreground-cleaned CMB maps that were released recently. We performed a directional analysis on the CMB sphere to search directions in which the temperature-temperature angular correlations are extreme. Results. Our analyses confirm a preferred axis in the CMB sphere, pointing in the direction ( l , b )≃(260° ,130° ), at the 98%−99% confidence level. In this direction, the CMB angular correlations exceed the antipodal direction most strongly. This preferred direction is unexpected in the ΛCDM cosmological model and represents a significant deviation from results obtained by applying the same procedure to simulated statistically isotropic CMB maps. This result confirms the north-south asymmetry in the most recent Planck data. This phenomenon is one of the previously reported CMB anomalies. Conclusions. We performed a robust detection of the north-south asymmetry in the temperature-temperature angular correlations, with a slightly different statistical significance, in the four Planck foreground-cleaned CMB maps. Moreover, we performed consistency tests by adding foreground and noise, both Planck data products, to the CMB map we studied, and we also investigated and discarded possible bias in our method. After these detailed analyses, we conclude that the north-south asymmetry phenomenon is present with a high statistical significance in the Planck CMB maps we studied. This result confirms previous reports in the literature in the past 20 years.

O Modelo ΛCDM-plano (Λ é a constante cosmológica e CDM, cold dark matter) é o que melhor se ajusta aos dados observacionais atualmente. Ele se fundamenta no Princípio Cosmológico, que assume a homogeneidade e a isotropia estatísticas do universo em larga escala. Estudando as propriedades desta última no Universo Local (UL) por meio do catálogo ALFALFA (Arecibo Legacy Fast ALFA Survey) – um levantamento que cobre ∼ 7000 deg2 do céu e conta com 31502 fontes extragalácticas de HI, distribuídas no intervalo 0 < z < 0.06 e divididas entre os hemisférios Norte e Sul Galácticos – encontramos resultados que indicam a existência de uma região contendo poucas galáxias, e que foi descrita pela primeira vez por Tully & Fischer (1987), ficando conhecida como Local Cosmic Void. Nossas análises são independentes de modelo e usam a função de correlação angular de dois pontos (2PACF) como aferidor estatístico, além de simulações do tipo lognormal (que consideram os parâmetros cosmológicos) para a estimativa das incertezas dos resultados. Para entender as propriedades e a morfologia da estrutura encontrada, fizemos testes com voids simulados, além de investigações comparativas com as descrições de voids do UL disponíveis na literatura. Nossos resultados indicam que o LCV possui contraste de densidade numérica δ ≃ −0.3, correspondente a uma subdensidade de ∼ 150 Mpc de comprimento e ∼ 60 Mpc de largura, características que concordam com a literatura.

The bulk flow in the Local Universe is a collective phenomenon due to the peculiar motions of matter structures, which, instead of moving in random directions, appears to follow an approximate dipole velocity flow. We apply a directional analysis to investigate, through the Hubble-Lema & icirc;tre diagram, the angular dependence of the Hubble constant H 0 of a sample of Type Ia supernovae from the Pantheon+ catalog in the Local Universe (0.015 <= z <= 0.06). We perform a directional analysis that reveals a statistically significant dipole variation of H 0, at more than 99.9% confidence level, showing that matter structures follow a dipole bulk flow motion toward (l, b) = (326.degrees 1 +/- 11.degrees 2, 27.degrees 8 +/- 11.degrees 2), close to the Shapley supercluster (l Shapley, b Shapley) = (311.degrees 5, 32.degrees 3), with velocity 132.14 +/- 109.3 km s-1 at the effective distance 102.83 +/- 10.2 Mpc. Interestingly, the antipodal direction of this dipole points close to the Dipole Repeller structure. Our analyses confirm that the gravitational dipole system Shapley-Dipole Repeller explains well the observed bulk flow velocity field in the Local Universe. Furthermore, we performed robustness tests that support our results. Additionally, our approach provides a measurement of the Hubble constant H 0 = 70.39 +/- 1.4 km s-1 Mpc-1, at the effective distance 102.8 Mpc, z similar or equal to 0.025.

Nowadays, efforts are being devoted to the study of alternative cosmological scenarios, in which, modifications of the General Relativity theory have been proposed to explain the late cosmic acceleration without assuming the existence of the dark energy component. In this scenario, we investigate the R^2 - corrected Appleby–Battye model , or R^2 -AB model, which consists of an f ( R ) model with only one extra free parameter b , besides the cosmological parameters of the flat- CDM model: H_0 and _m,0 . Regarding this model, it was already shown that a positive value for b is required for the model to be consistent with Solar System tests, moreover, the condition for the existence of a de Sitter state requires b ≥ 1.6 . To impose observational constraints on the R^2 -AB model we consider three datasets: 31 H ( z ) measurements from Cosmic Chronometers (CC), 20 [fσ_8](z) measurements from Redshift-Space Distortion (RSD), and the most recent type Ia Supernovae (SNe Ia) sample from Pantheon+. Next, we perform two diferent analyses: we have cosidered only SNe Ia data and the combined likelihood SNe + CC + RSD. The first one has provided b=2.28^+6.52_-0.55 , while the second one b=2.18^+5.41_-0.55 . In the first case it was necessary to set the absolute magnitude M_B = -19.253 from SH0ES collaboration, while in the second we did a marginalization over the Hubble constant H_0 in the normalized growth function. We have also observed that the H_0-M_B degenerecency was broken by adding CC data to the SNe data. Additionally, we perform illustrative analyses that compare this f ( R ) model with the flat- CDM model, considering several values of the parameter b , for diverse cosmological functions like the Hubble function H ( z ), the equation of state w_eff(z) , the parametrized growth rate of cosmic structures [f σ _8](z) , and σ _8(z) . From our results, we conclude that the R^2 -AB model fits well current observational data, although the model parameter b was not unambiguously constrained in the analyses.

ABSTRACT This is a model-independent analysis that investigates the statistical isotropy in the Local Universe using the Arecibo Legacy Fast ALFA (ALFALFA) survey data (0 < z < 0.06). We investigate the angular distribution of H i extragalactic sources from the ALFALFA catalogue and study whether they are compatible with the statistical isotropy hypothesis using the two-point angular correlation function (2PACF). Aware that the Local Universe is plenty of clustered structures and large voids, we compute the 2PACF with the Landy–Szalay estimator performing directional analyses to inspect 10 sky regions. We investigate these 2PACF using power-law best-fitting analyses, and determine the statistical significance of the best-fitting parameters for the 10 ALFALFA regions by comparison with the ones obtained through the same procedure applied to a set of mock catalogues produced under the homogeneity and isotropy hypotheses. Our conclusion is that the Local Universe, as mapped by the H i sources of the ALFALFA survey, is in agreement with the hypothesis of statistical isotropy within $2\sigma$ confidence level, for small- and large-angle analyses, with the only exception of one region – located near the Dipole Repeller – that appears slightly outlier ($2.4\sigma$). Interestingly, regarding the large angular distribution of the H i sources, we found three regions where the presence of cosmic voids reported in the literature left their signature in our 2PACF, suggesting projected large underdensities there, with number-density contrast δ ≃ −0.7. According to the current literature, these regions correspond, partially, to the sky position of the void structures known as Local Cosmic Void and Dipole Repeller.