LCDM Research Articles

Resolving the Hubble Tension with a Late Dark Energy Modification to the ΛCDM Model

Resolving the Hubble Tension with a Late Dark Energy Modification to the ΛCDM Model

Cosmic Chronometers, Pantheon+ Supernovae, and Quasars Favor Coasting Cosmologies over the Flat ΛCDM Model

Cosmic Chronometers, Pantheon+ Supernovae, and Quasars Favor Coasting Cosmologies over the Flat ΛCDM Model

Measuring the matter fluctuations in the Local Universe with the ALFALFA catalogue

Abstract The standard model of cosmology describes the matter fluctuations through the matter power spectrum, where σ8 ≡ σ8, 0 ≡ σ8(z = 0), defined at the scale of 8 h−1 Mpc, acts as a normalisation parameter. Currently, the literature reports measurements of σ8 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 HI 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 σ8 using the 3-dimensional distances of the HI sources determined by the ALFALFA survey without assuming a fiducial cosmology, resulting in a robust model-independent measurement of σ8. Our methodology involves the construction of suitable mock catalogues to simulate the large scale structure features observed in the data, applying the 2-point correlation function, and making use of Markov Chain Monte Carlo methods to estimate the parameters. Analysing these data we measure σ8 = 0.78 ± 0.04 for h = 0.6727, σ8 = 0.80 ± 0.05 for h = 0.698, and σ8 = 0.83 ± 0.05 for h = 0.7304. Considering the data pairs (σ8, H0) from the Planck CMB and ACT CMB-lensing analyses, our measurement agrees with them within 1 σ 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.

Revisiting the cosmological time dilation of distant quasars: Influence of source properties and evolution

Abstract After decades of searching, cosmological time dilation was recently identified in the timescale of variability seen in distant quasars. Here, we expand on the previous analysis to disentangle this cosmological signal from the influence of the properties of the source population, specifically the quasar bolometric luminosity and the rest-frame emission wavelength at which the variability was observed. Furthermore, we consider the potential influence of the evolution of the quasar population over cosmic time. We find that a significant intrinsic scatter of 0.288 ± 0.021 dex in the variability timescales, which was not considered in the previous analysis, is favoured by the data. This slightly increases the uncertainty in the results. However, the expected cosmological dependence of the variability timescales is confirmed to be robust to changes in the underlying assumptions. We find that the variability timescales increase smoothly with both wavelength and bolometric luminosity, and that black hole mass has no effect on the variability timescale once rest wavelength and bolometric luminosity are accounted for. Moreover, if the standard cosmological model is correct, governed by relativistic expansion, we also find very little cosmological evolution in the intrinsic variability timescales of distant quasars.

A flexible parameterization to test early physics solutions to the Hubble tension with future CMB data

One approach to reconciling local measurements of a high expansion rate with observations of acoustic oscillations in the CMB and galaxy clustering (the “Hubble tension”) is to introduce additional contributions to the ΛCDM model that are relevant before recombination. While numerous possibilities exist, none are currently well-motivated or preferred by data. However, future CMB experiments, which will measure acoustic peaks to much smaller scales and resolve polarization signals with higher signal-to-noise ratio over large sky areas, should detect almost any such modification at high significance.We propose a method to capture most relevant possible deviations from ΛCDM due to additional non-interacting components, while remaining sufficiently constraining to enable detection across various scenarios. The phenomenological model uses a fluid model with four parameters governing additional density contributions that peak at different redshifts, and two sound speed parameters. We forecast possible constraints with Simons Observatory, explore parameter degeneracies that arise in ΛCDM, and demonstrate that this method could detect a range of specific models. Which of the new parameters gets excited can give hints about the nature of any new physics, while the generality of the model allows for testing with future data in a way that should not be plagued by a posteriori choices and would reduce publication bias.When testing our model with Planck data, we find good consistency with the ΛCDM model, but the data also allows for a large Hubble parameter, especially if the sound speed of an additional component is not too different from that of radiation. The analysis with Planck data reveals significant volume effects, requiring careful interpretation of results. We demonstrate that Simons Observatory data will mitigate these volume effects, so that any indicated solution to the Hubble tension using our model cannot be mimicked by volume effects alone, given the significance of the tension.

ΛsCDM cosmology: alleviating major cosmological tensions by predicting standard neutrino properties

In this work, we investigate a two-parameter extension of the ΛsCDM model, as well as the ΛCDM model for comparison, by allowing variations in the effective number of neutrino species (N eff) and their total mass (∑mν). Our motivation is twofold: (i) to examine whether the ΛsCDM framework retains its success in fitting the data and addressing major cosmological tensions, without suggesting a need for a deviation from the standard model of particle physics, and (ii) to determine whether the data indicate new physics that could potentially address cosmological tensions, either in the post-recombination universe through the late-time (z ∼ 2) mirror AdS-to-dS transition feature of the ΛsCDM model, or in the pre-recombination universe through modifications in the standard values of N eff and ∑mν , or both. Within the extended ΛsCDM model, referred to as ΛsCDM+N eff+∑mν , we find no significant tension when considering the Planck-alone analysis. We observe that incorporating BAO data limits the further success of the ΛsCDM extension. However, the weakly model-dependent BAOtr data, along with Planck and Planck+PP&SH0ES, favor an H 0 value of approximately 73 km s-1 Mpc-1, which aligns perfectly with local measurements. In cases where BAOtr is part of the combined dataset, the mirror AdS-dS transition is very effective in providing enhanced H 0 values, and thus the model requires no significant deviation from the standard value of N eff = 3.044, remaining consistent with the standard model of particle physics. Both the H 0 and S 8 tensions are effectively addressed, with some compromise in the case of the Planck+BAO dataset. Finally, the upper bounds obtained on total neutrino mass, ∑mν ≲ 0.50 eV, are fully compatible with neutrino oscillation experiments. Our findings provide evidence that late-time physics beyond ΛCDM, such as ΛsCDM, without altering the standard description of the pre-recombination universe, can suffice to alleviate the major cosmological tensions, as indicated by our analysis of ΛsCDM+N eff+∑mν .

Phase space analysis and cosmography of a two-fluid cosmological model

Abstract In the framework of spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time, we investigate a two-fluid cosmological model where a tachyon scalar field with self-interacting potential and a modified chaplygin gas with non-linear equation of state are taken as the background fluids. We perform phase space analysis of the autonomous system obtained from the cosmological governing equations by a suitable transformation of variables. Linear stability theory is employed to characterise the stability criteria for hyperbolic critical points. Numerical investigation is carried out for non-hyperbolic points. Our study reveals that modified chaplygin fluid dominated solutions cannot provide the late-time evolution. Late-time accelerated evolution is obtained only when the solution is dominated by tachyon fluid. This study also yields a late-time scaling attractor providing similar order of energy densities in its evolution. The adiabatic sound speed is evaluated for both the fluids and test the stability of the models independently. Further, we perform cosmographic analysis in the model independent way by evaluating all the cosmographic parameters and then Om diagnostic is also found to compare our model with ΛCDM model.

EPOCHS. IV. SED Modeling Assumptions and Their Impact on the Stellar Mass Function at 6.5 ≤ z ≤ 13.5 Using PEARLS and Public JWST Observations

We utilize deep JWST Near Infrared Camera (NIRCam) observations for the first direct constraints on the Galaxy Stellar Mass Function (GSMF) at z > 10. Our EPOCHS v1 sample includes 1120 galaxy candidates at 6.5 < z < 13.5 taken from a consistent reduction and analysis of publicly available deep JWST NIRCam data covering the Prime Extragalactic Areas for Reionization Science, CEERS, GLASS, JADES GOOD-S, NGDEEP, and SMACS0723 surveys, totaling 187 arcmin2. We investigate the impact of spectral energy distribution fitting methods, assumed star formation histories (SFHs), dust laws, and priors on galaxy masses and the resultant GSMF. While our fiducial GSMF agrees with the literature at z < 13.5, we find that the assumed SFH model has a large impact on the GSMF and stellar mass density (SMD), finding a 0.75 dex increase in the SMD at z = 10.5 between a flexible nonparametric and standard parametric SFH. Overall, we find a flatter SMD evolution at z ≥ 9 than some studies predict, suggesting a rapid buildup of stellar mass in the early Universe. We find no incompatibility between our results and those of standard cosmological models, as suggested previously, although the most massive galaxies may require a high star formation efficiency. We find that the “little red dot” galaxies dominate the z = 7 GSMF at high masses, necessitating a better understanding of the relative contributions of active galactic nucleus and stellar emission. We show that assuming a theoretically motivated top-heavy initial mass function (IMF) reduces stellar mass by 0.5 dex without affecting fit quality, but our results remain consistent with existing cosmological models with a standard IMF.

Fundamental plane distances and peculiar velicities of 140 groups and clusters of galaxies at low redshifts: the Hubble diagram

We used the fundamental plane (FP) of early-type galaxies (data from the Sloan Digital Sky Survey) to measure the relative distances and peculiar velocities of 140 groups and clusters of galaxies at low redshifts ( z0.12). We have constructed the Hubble diagram between the distances of galaxy groups/clusters and their radial velocities in the CMB reference frame in the flat ΛCDM model ( Ωm=0.3, H0=70km · s –1 Mpc –1 ). We found that the standard logarithmic scatter of groups and clusters of galaxies on the Hubble diagram (minus peculiar velocities) is ± 0.0173 ( N = 140), which corresponds to the deviation of the Hubble constant 70 ± 2.8 km · s –1 Mpc –1 . For a sample of galaxy systems ( N = 63) with X-ray luminosity in the interval 0.151÷4×1044erg/s we got 70 ± 2.1 km · s –1 Mpc –1 . The standard deviations of peculiar velocities with quadratic allowance for errors are equal to null714 ± 7 km/s and 600 ± 7 km/s, respectively. Five large superclusters of galaxies from the SDSS region show an average peculiar velocity relative to the CMB reference frame +240 ± 250 km/s. We did not detect the outflow of galactic systems from the void (Giant Void, α≈13h, δ≈40°, z≈0.107) formed by groups and clusters of galaxies.

Stability of f(Q, B) Gravity via Dynamical System Approach: A Comprehensive Bayesian Statistical Analysis

Abstract In this work, we explore the cosmological stability of f(Q, B) gravity using a dynamical system approach, where Q denotes the nonmetricity scalar and B represents the boundary term. We determine the model parameters of f(Q, B) through Bayesian statistical analysis, employing Markov Chain Monte Carlo techniques. This analysis incorporates numerical solutions and observational data from cosmic chronometers, the extended Pantheon+ data set, and baryonic acoustic oscillation measurements. Our findings reveal a stable critical point within the dynamical system of the model, corresponding to the de Sitter phase, which is consistent with current observations of the Universe dominated by dark energy and undergoing late-time accelerated expansion. Additionally, we utilize center manifold theory to examine the stability of this critical point, providing deeper insights into the behavior of the model. The cosmological implications of f(Q, B) gravity indicate a smooth transition in the deceleration parameters from deceleration to the acceleration phase, underscoring the potential of the model to describe the evolution of the Universe. Our results suggests that the f(Q, B) model presents a viable alternative to the standard ΛCDM model, effectively capturing the observed acceleration of the Universe and offering a robust framework for explaining the dynamics of cosmic expansion.

The Redshift-space Momentum Power Spectrum. III. Measuring the Growth Rate from the SDSSv Survey Using the Auto- and Cross-power Spectrum of the Galaxy Density and Momentum Fields

The large-scale structure of the Universe and its evolution over time contains an abundance of cosmological information. One way to unlock this is by measuring the density and momentum power spectrum from the positions and peculiar velocities of galaxies and fitting the cosmological parameters from these power spectra. In this paper, we will explore the cross-power spectrum between the density and momentum fields of galaxies. We derive the estimator of the density–momentum cross-power spectrum multipoles. The growth rate of the large-scale structure, f σ 8, is measured from fitting the combined density monopole, momentum monopole, and cross-dipole power spectrum. The estimators and models of the power spectrum as well as our fitting method have been tested using mock catalogs; we find that they perform well in recovering the fiducial values of the cosmological parameters of the simulations, and we also find that the errors of the parameters can be largely reduced by including the cross-power spectrum in the fit. We measure the autodensity, automomentum, and cross-power spectrum using the Sloan Digital Sky Survey Data Release 14 peculiar velocity catalog. The fit result of the growth rate f σ 8 is fσ8=0.413−0.058+0.050 at effective redshift z eff = 0.073, and our measurement is consistent with the prediction of the Lambda cold dark matter cosmological model, assuming general relativity.

Euclid preparation. Simulations and non-linearities beyond Lambda cold dark matter. I. Numerical methods and validation

To constrain cosmological models beyond Lambda CDM, the development of the analysis pipeline requires simulations that capture the non-linear phenomenology of such models. We present an overview of numerical methods and $N$-body simulation codes developed to study the non-linear regime of structure formation in alternative dark energy and modified gravity theories. We review a variety of numerical techniques and approximations employed in cosmological $N$-body simulations to model the complex phenomenology of scenarios beyond Lambda CDM. This includes discussions on solving non-linear field equations, accounting for fifth forces, and implementing screening mechanisms. Furthermore, we conduct a code comparison exercise to assess the reliability and convergence of different simulation codes across a range of models. Our analysis demonstrates a high degree of agreement among the outputs of different simulation codes, typically within 2&lt;!PCT!&gt; for the predicted modification of the matter power spectrum and within 4&lt;!PCT!&gt; for the predicted modification of the halo mass function, although some approximations degrade accuracy a bit further. This provides confidence in current numerical methods of modelling cosmic structure formation beyond Lambda CDM. We highlight recent advances made in simulating the non-linear scales of structure formation, which are essential for leveraging the full scientific potential of the forthcoming observational data from the mission.

Interacting Dark Energy after DESI Baryon Acoustic Oscillation Measurements

We investigate the implications of the baryon acoustic oscillations measurement released by the Dark Energy Spectroscopic Instrument for interacting dark energy (IDE) models characterized by an energy-momentum flow from dark matter to dark energy. By combining Planck-2018 and Dark Energy Spectroscopic Instrument data, we observe a preference for interactions, leading to a nonvanishing interaction rate ξ=−0.32−0.14+0.18, which results in a present-day expansion rate H0=70.8−1.7+1.4 km/s/Mpc, reducing the tension with the value provided by the SH0ES Collaboration to less than ∼1.3σ. The preference for interactions remains robust when including measurements of the expansion rate H(z) obtained from the relative ages of massive, early-time, and passively evolving galaxies, as well as when considering distance moduli measurements from Type Ia supernovae sourced from the Pantheon-plus catalog using the SH0ES Cepheid host distances as calibrators. Overall, the IDE framework provides an equally good, or better, explanation of both high- and low-redshift observations compared to the lambda cold dark matter model, while also yielding higher H0 values that align more closely with the local distance ladder estimates. However, a limitation of the IDE model is that it predicts lower Ωm and higher σ8 values, which may not be fully consistent with large-scale structure data at the level. Published by the American Physical Society 2024

Dark energy reconstructions combining baryonic acoustic oscillation data with galaxy clusters and intermediate-redshift catalogs

Cosmological parameters and dark energy (DE) behavior are generally constrained assuming a priori models. We work out a model-independent reconstruction to bind the key cosmological quantities and the DE evolution. Through the model-independent Bézier interpolation method, we reconstructed the Hubble rate from the observational Hubble data and derived analytic expressions for the distances of galaxy clusters, type Ia supernovae, and uncorrelated baryonic acoustic oscillation (BAO) data. In view of the discrepancy between Sloan Digital Sky Survey (SDSS) and Dark Energy Spectroscopic Instrument (DESI) BAO data, they were kept separate in two distinct analyses. Correlated BAO data were employed to break the baryonic--dark matter degeneracy. All these interpolations enable us to single out and reconstruct the DE behavior with the redshift $z$ in a totally model-independent way. In both analyses, with SDSS-BAO or DESI-BAO datasets, the constraints agree at a $1$--sigma confidence level (CL) with the flat Lambda CDM model. The Hubble constant tension appears solved in favor of the Planck satellite value. The reconstructed DE behavior exhibits deviations at small $z$ ($&gt;1$--sigma CL), but agrees ($&lt;1$--sigma CL) with the cosmological constant paradigm at larger $z$. Our method hints at a slowly evolving DE, consistent with a cosmological constant at early times.

Testing consistency of cosmological parameters in spatially flat ΛCDM model from observational data in different redshift regions

The Hubble tension has become the most significant crisis in modern cosmology, suggesting that the [Formula: see text]CDM model may not accurately describe cosmic evolution. In this paper, we test the spatially flat [Formula: see text]CDM model by comparing constraints on cosmological parameters from observational data across different redshift regions. Utilizing Pantheon[Formula: see text] SN Ia sample, cosmic chronometer data, and baryon acoustic oscillation data, we derive six distinct sets of constraints within the redshift range [Formula: see text]. At the first three and the last redshift points, the observed values of the present matter density parameter, [Formula: see text], are consistent with those from the full dataset within [Formula: see text] confidence level (CL), whereas values at [Formula: see text] and [Formula: see text] are not, and the maximum deviation occurring at [Formula: see text] reaches [Formula: see text]. The data indicate a decreasing trend in the Hubble constant, [Formula: see text], and the SN Ia absolute magnitude, M, with increasing redshift. Despite the variation of both [Formula: see text] and [Formula: see text] across different redshifts, the values of [Formula: see text] remain consistent within [Formula: see text] CL across all regions.

Cosmological Constraints from Combining Photometric Galaxy Surveys and Gravitational Wave Observatories

Spatial variations in survey properties due to selection effects generate substantial systematic errors in large-scale structure measurements in optical galaxy surveys on very large scales. On such scales, the statistical sensitivity of optical surveys is also limited by their finite sky coverage. By contrast, gravitational wave (GW) sources appear to be relatively free of these issues, provided the angular sensitivity of GW experiments can be accurately characterized. We quantify the expected cosmological information gain from combining the forecast LSST 3x2pt analysis (combination of three 2-point correlations of galaxy density and weak lensing shear fields) with the large-scale auto-correlation of GW sources from proposed next-generation GW experiments. We find that in ΛCDM and wCDM models, there is no significant improvement in cosmological constraints from combining GW with LSST 3x2pt over LSST alone, due to the large shot noise for the former; however, this combination does enable a ∼6% constraint on the linear galaxy bias of GW sources. More interestingly, the optical-GW data combination provides tight constraints on models with primordial non-Gaussianity (PNG), due to the predicted scale-dependent bias in PNG models on large scales. Assuming that the largest angular scales that LSST will probe are comparable to those in Stage III surveys (), the inclusion of next-generation GW measurements could improve constraints on the PNG parameter by up to a factor of ≃6.6 compared to LSST alone, yielding . These results assume the expected capability of a network of Einstein Telescope-like GW observatories, with a detection rate of 106 events/year. We investigate the sensitivity of our results to different assumptions about future GW detectors as well as different LSST analysis choices.

Suppression without Thawing: Constraining Structure Formation and Dark Energy with Galaxy Clustering.

We present a new perturbative full-shape analysis of BOSS galaxy clustering data, including the full combination of the galaxy power spectrum and bispectrum multipoles, baryon acoustic oscillations, and cross-correlations with the gravitational lensing of cosmic microwave background measured from Planck. Assuming the ΛCDM model, we constrain the matter density fraction Ω_{m}=0.3138±0.0086, the Hubble constant H_{0}=68.23±0.78 km s^{-1} Mpc^{-1}, and the mass fluctuation amplitude σ_{8}=0.688±0.026 (equivalent to S_{8}=0.703±0.029). Cosmic structure at low redshifts appears suppressed with respect to the Planck ΛCDM concordance model at 4.5σ. We explore the implications of this dataset for the recent DESI BAO preference for dynamical dark energy (DDE): the BOSS data combine with DESI BAO and PantheonPlus supernovae competitively compared to the CMB, yielding no preference for DDE, but the same ∼10% suppression of structure, with dark energy being consistent with a cosmological constant at 68% CL. Our results suggest that either the data contains residual systematics, or more model-building efforts may be required to restore cosmological concordance.

Emulation of f(R) modified gravity from ΛCDM using conditional GANs

Abstract A major aim of cosmological surveys is to test deviations from the standard ΛCDM model, but the full scientific value of these surveys will only be realised through efficient simulation methods that keep up with the increasing volume and precision of observational data. N-body simulations of modified gravity (MG) theories are computationally expensive since highly non-linear equations must be solved. This represents a significant bottleneck in the path to reach the data volume and resolution attained by equivalent ΛCDM simulations. We develop a field-level neural network-based emulator that generates density and velocity divergence fields under the f(R) gravity MG model from the corresponding ΛCDM simulated fields. Using attention mechanisms and a complementary frequency-based loss function, our model is able to learn this intricate mapping. We use the idea of latent space extrapolation to generalise our emulator to f(R) models with differing field strengths. The predictions of our emulator agree with the f(R) simulations to within 5% for matter density and to within 10% for velocity divergence power spectra up to k ∼ 2 h Mpc−1. But for a few select cases, higher-order statistics are reproduced with ≲10% agreement. Latent extrapolation allows our emulator to generalise to different parameterisations of the f(R) model without explicitly training on those variants. Given a ΛCDM simulation, the GPU-based emulator can reproduce the equivalent f(R) realisation ∼600 times faster than full N-body simulations. This lays the foundations for a valuable tool for realistic yet rapid mock field generation and robust cosmological analyses.

Distinguishing coupled dark energy models with neural networks

Aims. We investigate whether neural networks (NNs) can accurately differentiate between growth-rate data of the large-scale structure (LSS) of the Universe simulated via two models: a cosmological constant and Λ cold dark matter (CDM) model and a tomographic coupled dark energy (CDE) model. Methods. We built an NN classifier and tested its accuracy in distinguishing between cosmological models. For our dataset, we generated fσ8(z) growth-rate observables that simulate a realistic Stage IV galaxy survey-like setup for both ΛCDM and a tomographic CDE model for various values of the model parameters. We then optimised and trained our NN with Optuna, aiming to avoid overfitting and to maximise the accuracy of the trained model. We conducted our analysis for both a binary classification, comparing between ΛCDM and a CDE model where only one tomographic coupling bin is activated, and a multi-class classification scenario where all the models are combined. Results. For the case of binary classification, we find that our NN can confidently (with &gt; 86% accuracy) detect non-zero values of the tomographic coupling regardless of the redshift range at which coupling is activated and, at a 100% confidence level, detect the ΛCDM model. For the multi-class classification task, we find that the NN performs adequately well at distinguishing ΛCDM, a CDE model with low-redshift coupling, and a model with high-redshift coupling, with 99%, 79%, and 84% accuracy, respectively. Conclusions. By leveraging the power of machine learning, our pipeline can be a useful tool for analysing growth-rate data and maximising the potential of current surveys to probe for deviations from general relativity.

Cosmography from accurate mass modeling of the lens group SDSS J0100+1818: Five sources at three different redshifts

Systems where multiple sources at different redshifts are strongly lensed by the same deflector allow one to directly investigate the evolution of the angular diameter distances as a function of redshift, and thus to learn about the geometry of the Universe. We present measurements of the values of the total matter density, Ωm, and of the dark energy equation of state parameter, w, through a detailed strong lensing analysis of SDSS J0100+1818, a group-scale system at z = 0.581 with five lensed sources, from z = 1.698 to 4.95. We take advantage of new spectroscopic data from the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope to securely measure the redshift of 65 sources, including the 5 multiply imaged background sources (lensed into a total of 18 multiple images) and 19 galaxies on the deflector plane, all employed to build robust strong lensing models with the software GLEE. The total mass distribution of the deflector is described in a relatively simple way, and includes an extended halo, the brightest group galaxy (BGG) with a measured stellar velocity dispersion of (380.5 ± 4.4) km s−1, and fainter members. We measure Ωm = 0.14−0.09+0.16 in a flat Λ cold dark matter (CDM) model, and Ωm = 0.19−0.10+0.17 and w = −1.27−0.48+0.43 in a flat wCDM model. Given the presence of different sources angularly close in projection, we quantify through a multiplane approach their impact on the inferred values of the cosmological parameters. We obtain consistent median values, with uncertainties for only Ωm increasing by approximately a factor of 1.5. Thanks to the remarkably wide radial interval where the multiple images are observed, ranging from 15 to 77 kpc from the BGG, we accurately measure the total mass profile and infer the stellar over total mass profile of the deflector. They result in a total mass of (1.55 ± 0.01)×1013 M⊙ within 50 kpc and a stellar over total mass profile decreasing from 45.6−8.3+8.7% at the BGG effective radius to (6.6 ± 1.1)% at R ≈ 77 kpc. Our results confirm that SDSS J0100+1818 is one of the most massive (lens) galaxies known at intermediate redshift and one of the most distant candidate fossil systems. We also show that group-scale systems that act as lenses for ≥3 background sources at different redshifts enable one to estimate the values of the cosmological parameters Ωm and w with an accuracy that is competitive with that obtained from lens galaxy clusters.