Properties Of Dark Energy Research Articles

Dark energy and inflation invoked in CCGG by locally contorted space-time

The cosmological implications of the covariant canonical gauge theory of gravity (CCGG) are investigated. We deduce that, in a metric-compatible geometry, the requirement of covariant conservation of matter invokes torsion of space-time. In the Friedman model, this leads to a scalar field built from contortion and the metric with the property of dark energy, which transforms the cosmological constant to a time-dependent function. Moreover, the quadratic, scale-invariant Riemann–Cartan term in the CCGG Lagrangian endows space-time with kinetic energy, and in the field equations adds a geometrical curvature correction to Einstein gravity. Applying in the Friedman model the standard Lambda hbox {CDM} parameter set, those equations yield a cosmological field depending just on one additional, dimensionless “deformation” parameter of the theory that determines the strength of the quadratic term, viz. the deviation from the Einstein–Hilbert ansatz. Moreover, the apparent curvature of the universe differs from the actual curvature parameter of the metric. The numerical analysis in that parameter space yields three cosmology types: (1) a bounce universe starting off from a finite scale followed by a steady inflation, (2) a singular Big Bang universe undergoing a secondary inflation–deceleration phase and (3) a solution similar to standard cosmology but with a different temporal profile. The common feature of all scenarios is the graceful exit to the current dark energy era. The value of the deformation parameter can be deduced by comparing theoretical calculations with observations, namely with the SNeIa Hubble diagram and the deceleration parameter. That comparison implies a considerable admixture of scale-invariant quadratic gravity to Einstein gravity. This theory also sheds new light on the resolution of the cosmological constant problem and of the Hubble tension.

Cosmological Model Insensitivity of Local H0 from the Cepheid Distance Ladder

Abstract The observed tension (∼9% difference) between the local distance ladder measurement of the Hubble constant, H 0, and its value inferred from the cosmic microwave background could hint at new, exotic, cosmological physics. We test the impact of the assumption about the expansion history of the universe ( ) on the local distance ladder estimate of H 0. In the fiducial analysis, the Hubble flow Type Ia supernova (SN Ia) sample is truncated to z < 0.15, and the deceleration parameter (q 0) is fixed to −0.55. We create realistic simulations of the calibrator and Pantheon samples, and account for a full systematics covariance between these two sets. We fit several physically motivated dark-energy models, and derive combined constraints from calibrator and Pantheon SNe Ia and simultaneously infer H 0 and dark-energy properties. We find that the assumption on the dark-energy model does not significantly change the local distance ladder value of H 0, with a maximum difference (ΔH 0) between the inferred value for different models of 0.47 km , i.e., a 0.6% shift in H 0, significantly smaller than the observed tension. Additional freedom in the dark-energy models does not increase the error in the inferred value of H 0. Including systematics covariance between the calibrators, low-redshift SNe, and high-redshift SNe can induce small shifts in the inferred value for H 0. The SN Ia systematics in this study contribute ≲0.8% to the total uncertainty of H 0.

The Square Kilometre Array and 21 cm cosmology

Detecting the 21 cm signals of neutral hydrogen atoms is crucial to understanding the physics of the Universe during its first billion years, and can also provide an important cosmological probe to the expansion history of the late universe, the properties of dark matter and dark energy, and the formation and evolution of various structures. The Square Kilometre Array (SKA) is an international big-science project, and it will be the largest radio telescope in the world after its completion of construction. In the forthcoming decades, the SKA will undoubtedly push the 21 cm cosmology into a new era.

Cosmology from the Chinese Space Station Optical Survey (CSS-OS)

Abstract The Chinese Space Station Optical Survey (CSS-OS) is a planned full sky survey operated by the Chinese Space Station Telescope (CSST). It can simultaneously perform the photometric imaging and spectroscopic slitless surveys, and will probe weak and strong gravitational lensing, galaxy clustering, individual galaxies and galaxy clusters, active galactic nucleus, and so on. It aims to explore the properties of dark matter and dark energy and other important cosmological problems. In this work, we focus on two main CSS-OS scientific goals, i.e., the weak gravitational lensing (WL) and galaxy clustering surveys. We generate the mock CSS-OS data based on the observational COSMOS and zCOSMOS catalogs. We investigate the constraints on the cosmological parameters from the CSS-OS using the Markov Chain Monte Carlo method. The intrinsic alignments, galaxy bias, velocity dispersion, and systematics from instrumental effects in the CSST WL and galaxy clustering surveys are also included, and their impacts on the constraint results are discussed. We find that the CSS-OS can improve the constraints on the cosmological parameters by a factor of a few (even one order of magnitude in the optimistic case), compared to the current WL and galaxy clustering surveys. The constraints can be further enhanced when performing joint analysis with the WL, galaxy clustering, and galaxy–galaxy lensing data. Therefore, the CSS-OS is expected to be a powerful survey for exploring the universe. Since some assumptions may be still optimistic and simple, it is possible that the results from the real survey could be worse. We will study these issues in detail with the help of simulations in the future.

Exploring neutrino mass and mass hierarchy in interacting dark energy models

We investigate how the dark energy properties impact the constraints on the total neutrino mass in interacting dark energy (IDE) models. In this study, we focus on two typical interacting dynamical dark energy models, i.e., the interacting $w$ cold dark matter (I$w$CDM) model and the interacting holographic dark energy (IHDE) model. To avoid the large-scale instability problem in IDE models, we apply the parameterized post-Friedmann approach to calculate the perturbation of dark energy. We employ the Planck 2015 cosmic microwave background temperature and polarization data, combined with low-redshift measurements on baryon acoustic oscillation distance scales, type Ia supernovae, and the Hubble constant, to constrain the cosmological parameters. We find that the dark energy properties could influence the constraint limits on the total neutrino mass. Once dynamical dark energy is considered in the IDE models, the upper bounds of $\sum m_\nu$ will be changed. By considering the values of $\chi^2_{\rm min}$, we find that in these IDE models the normal hierarchy case is slightly preferred over the inverted hierarchy case; for example, $\Delta\chi^2=2.720$ is given in the IHDE+$\sum m_\nu$ model. In addition, we also find that in the I$w$CDM+$\sum m_\nu$ model $\beta=0$ is consistent with current observational data inside the 1$\sigma$ range, and in the IHDE+$\sum m_\nu$ model $\beta>0$ is favored at more than 2$\sigma$ level.

Models and Simulations for the Photometric LSST Astronomical Time Series Classification Challenge (PLAsTiCC)

We describe the simulated data sample for the Photometric Large Synoptic Survey Telescope (LSST) Astronomical Time Series Classification Challenge (PLAsTiCC), a publicly available challenge to classify transient and variable events that will be observed by the LSST, a new facility expected to start in the early 2020s. The challenge was hosted by Kaggle, ran from 2018 September 28 to December 17, and included 1094 teams competing for prizes. Here we provide details of the 18 transient and variable source models, which were not revealed until after the challenge, and release the model libraries at https://doi.org/10.5281/zenodo.2612896. We describe the LSST Operations Simulator used to predict realistic observing conditions, and we describe the publicly available SNANA simulation code used to transform the models into observed fluxes and uncertainties in the LSST passbands (ugrizy). Although PLAsTiCC has finished, the publicly available models and simulation tools are being used within the astronomy community to further improve classification, and to study contamination in photometrically identified samples of SN Ia used to measure properties of dark energy. Our simulation framework will continue serving as a platform to improve the PLAsTiCC models, and to develop new models.

Cosmological Constraints from Multiple Probes in the Dark Energy Survey

The combination of multiple observational probes has long been advocated as a powerful technique to constrain cosmological parameters, in particular dark energy. The Dark Energy Survey has measured 207 spectroscopically confirmed type Ia supernova light curves, the baryon acoustic oscillation feature, weak gravitational lensing, and galaxy clustering. Here we present combined results from these probes, deriving constraints on the equation of state, w, of dark energy and its energy density in the Universe. Independently of other experiments, such as those that measure the cosmic microwave background, the probes from this single photometric survey rule out a Universe with no dark energy, finding w=-0.80_{-0.11}^{+0.09}. The geometry is shown to be consistent with a spatially flat Universe, and we obtain a constraint on the baryon density of Ω_{b}=0.069_{-0.012}^{+0.009} that is independent of early Universe measurements. These results demonstrate the potential power of large multiprobe photometric surveys and pave the way for order of magnitude advances in our constraints on properties of dark energy and cosmology over the next decade.

Low redshift observational constraints on tachyon models of dark energy

The background evolution of an accelerated, dark energy dominated universe is aptly described by non-canonical tachyon scalar field models. The accelerated expansion of the universe is determined by the choice of a suitable scalar field potential; in the case of a tachyon field, a `runaway' potential. In the absence of a fundamental theory, dark energy properties are studied in a phenomenological approach. This includes determining the model parameters using observations and to probe the allowed deviation from the cosmological constant model. In this paper, we present constraints on tachyon scalar field parameters from low redshift data for two different scalar field potentials. These scalar field potentials have been crucial in tachyon dark energy studies. The datasets considered in this paper include the supernova type Ia data, independent measurements of the Hubble parameter and the Baryon Acoustic Oscillation data. In this paper, we present constraints on tachyon field parameters using these observations and their combination. A combination of the datasets indicates that those model parameters are preferred which emulate the cosmological constant model. The initial value of the scalar field, in the unit of the Hubble constant, is bounded from below and does not require fine-tuning at larger values.

Structure formation in dark energy cosmologies described by PADE parametrization

We study the imprints on the formation of cosmic structures of a particular class of dark energy parameterizations dubbed PADE parameterization. Here we investigate how dark energy can affect the growth of large scale structures of the universe in framework of spherical collapse model. The dynamics of the spherical collapse of a dark matter halo depends on the properties of the dark energy model. We show that the properties of spherical collapse scenario are directly affected by the evolution of dark energy. We obtain the main parameters of spherical collapse for two different DE parameterizations in two different approaches: first the homogeneous DE approach, in which dark energy does not exhibit fluctuations on cluster scales and the other, clustered DE scenario in which, dark energy components inside the overdense region collapses similar to dark matter. Using the Sheth-Tormen mass function, we investigate the abundance of virialized halos in the framework of PADE parameterizations. Specifically, the present analysis shows that the number count of dark matter halos depends on the evolution of DE parameterizations and clustering properties of dark energy. Also we show that perturbations in phantom DE components enhance the growth of matter perturbations. This result were obtained in the literature for dark energy parameterizations that are phantom at all redshifts. But we obtained same results for dark energy parameterizations which are in phantom regime and enter in quintessence region at relatively low redshifts. We also show that in parameterizations under study, low mass halos were formed before massive halos.

An Analogy between the Properties of “Dark Energy” and Physical Vacuum Consisting of Quantum Harmonic Oscillators Characterized by Zero-Point Energy

In quantum field theory, the physical vacuum, free from magnetic and electric fields (without regard to gravitational energy), is defined not as an empty space but as the ground state of the field consisting of quantum harmonic oscillators (QHOs) characterized by zero-point energy. The aim of this work is to show that such physical vacuum may possess the properties similar to the properties of dark energy: the positive density, the negative pressure, and the possibility of so-called accelerated expansion. In the model discussed, the mass of QHOs determines the positive density of dark energy. The observed electric polarization of physical vacuum in an electric field means the existence of electric dipole moment of QHO, which, in turn, suggests the existence inside the QHO of a repulsive force between unlike charges compensating the attractive Coulomb force between the charges. The existence of such repulsive force may be treated as the existence of omniradial tensions inside every QHO. In terms of hydrodynamics, it means that the vacuum with this property may be regarded as a medium with negative pressure. The electric dipole-dipole interaction of QHOs under some condition may result in the expansion of physical vacuum consisting of QHOs. It is shown also that the physical vacuum consisting of QHOs is a luminiferous medium, and based on this concept the conditions are discussed for the emergence of invisiblity of any objects (in particular, dark matter). The existence of luminiferous medium does not contradict the second postulate of special relativity (the principle of constancy of the velocity of light in inertial systems), if to take into account the interaction of photons with QHOs and with virtual photons (the virtual particles pairs) created by quantum entities that constitute the inertial systems.

The gravitational and lensing-ISW bispectrum of 21 cm radiation

Cosmic Microwave Background experiments from COBE to Planck, have launched cosmology into an era of precision science, where many cosmological parameters are now determined to the percent level. Next generation telescopes, focussing on the cosmological 21cm signal from neutral hydrogen, will probe enormous volumes in the low-redshift Universe, and have the potential to determine dark energy properties and test modifications of Einstein's gravity. We study the 21cm bispectrum due to gravitational collapse as well as the contribution by line of sight perturbations in the form of the lensing-ISW bispectrum at low-redshifts ($z \sim 0.35-3$), targeted by upcoming neutral hydrogen intensity mapping experiments. We compute the expected bispectrum amplitudes and use a Fisher forecast model to compare power spectrum and bispectrum observations of intensity mapping surveys by CHIME, MeerKAT and SKA-mid. We find that combined power spectrum and bispectrum observations have the potential to decrease errors on the cosmological parameters by an order of magnitude compared to Planck. Finally, we compute the contribution of the lensing-ISW bispectrum, and find that, unlike for the cosmic microwave background analyses, it can safely be ignored for 21cm bispectrum observations.

Note on Tsallis holographic dark energy

We explore the effects of considering various infrared (IR) cutoffs, including the particle horizon, the Ricci horizon and the Granda–Oliveros (GO) cutoffs, on the properties of Tsallis holographic dark energy (THDE) model, proposed inspired by Tsallis generalized entropy formalism (Tavayef et al. in Phys Lett B 781:195, 2018). Interestingly enough, we find that for the particle horizon as IR cutoff, the obtained THDE model can describe the late time accelerated universe. This is in contrast to the usual HDE model which cannot lead to an accelerated universe, if one considers the particle horizon as the IR cutoff. We also investigate the cosmological consequences of THDE under the assumption of a mutual interaction between the dark sectors of the Universe. It is shown that the evolution history of the Universe can be described by these IR cutoffs and thus the current cosmic acceleration can also be realized. The sound instability of the THDE models for each cutoff are also explored, separately.

Dark energy reconstruction based on the Pad\xe9 approximation; an expansion around the varLambda CDM

We study the dynamical properties of dark energy based on a large family of Padé parameterizations for which the dark energy density evolves as the ratio between two polynomials in the scale factor of the universe. Using the latest cosmological data we perform a standard likelihood analysis in order to place constraints on the main cosmological parameters of different Padé models. We find that the basic cosmological parameters, namely ({varOmega _{m0}},h,{sigma _{8}}) are practically the same for all Padé parametrizations explored here. Concerning the free parameters which are related to dark energy we show that the best-fit values indicate that the equation of state parameter at the present time is in the phantom regime (w<-1); however, we cannot exclude the possibility of w>-1 at 1sigma level. Finally, for the current family of Padé parametrizations we test their ability, via AIC, BIC and Jeffreys’ scale, to deviate from varLambda CDM cosmology. Among the current Padé parametrizations, the model which contains two dark energy parameters is the one for which a small but non-zero deviation from varLambda CDM cosmology is slightly allowed by the AIC test. Moreover, based on Jeffreys’ scale we show that a deviation from varLambda CDM cosmology is also allowed and thus the possibility of having a dynamical dark energy in the form of Padé parametrization cannot be excluded.

The effect of inhomogeneities on dark energy constraints

Constraints on models of the late time acceleration of the universe assume the cosmological principle of homogeneity and isotropy on large scales. However, small scale inhomogeneities can alter observational and dynamical relations, affecting the inferred cosmological parameters. For precision constraints on the properties of dark energy, it is important to assess the potential systematic effects arising from these inhomogeneities. In this study, we use the Type Ia supernova magnitude-redshift relation to constrain the inhomogeneities as described by the Dyer-Roeder distance relation and the effect they have on the dark energy equation of state (w), together with priors derived from the most recent results of the measurements of the power spectrum of the Cosmic Microwave Background and Baryon Acoustic Oscillations. We find that the parameter describing the inhomogeneities (η) is weakly correlated with w. The best fit values w = −0.933 ± 0.065 and η = 0.61 ± 0.37 are consistent with homogeneity at < 2 σ level. Assuming homogeneity (η =1), we find w = −0.961 ± 0.055, indicating only a small change in w. For a time-dependent dark energy equation of state, w0 = −0.951 ± 0.112 and wa = 0.059 ± 0.418, to be compared with w0 = −0.983 ± 0.127 and wa = 0.07 ± 0.432 in the homogeneous case, which is also a very small change. We do not obtain constraints on the fraction of dark matter in compact objects, fp, at the 95% C.L. with conservative corrections to the distance formalism. Future supernova surveys will improve the constraints on η, and hence, fp, by a factor of ∼10.

Measuring Dark Energy Properties with Photometrically Classified Pan-STARRS Supernovae. II. Cosmological Parameters

Abstract We use 1169 Pan-STARRS supernovae (SNe) and 195 low-z (z &lt; 0.1) SNe Ia to measure cosmological parameters. Though most Pan-STARRS SNe lack spectroscopic classifications, in a previous paper we demonstrated that photometrically classified SNe can be used to infer unbiased cosmological parameters by using a Bayesian methodology that marginalizes over core-collapse (CC) SN contamination. Our sample contains nearly twice as many SNe as the largest previous SN Ia compilation. Combining SNe with cosmic microwave background (CMB) constraints from Planck, we measure the dark energy equation-of-state parameter w to be −0.989 ± 0.057 (stat+sys). If w evolves with redshift as w(a) = w 0 + w a (1 − a), we find w 0 = −0.912 ± 0.149 and w a = −0.513 ± 0.826. These results are consistent with cosmological parameters from the Joint Light-curve Analysis and the Pantheon sample. We try four different photometric classification priors for Pan-STARRS SNe and two alternate ways of modeling CC SN contamination, finding that no variant gives a w differing by more than 2% from the baseline measurement. The systematic uncertainty on w due to marginalizing over CC SN contamination, , is the third-smallest source of systematic uncertainty in this work. We find limited (1.6σ) evidence for evolution of the SN color-luminosity relation with redshift, a possible systematic that could constitute a significant uncertainty in future high-z analyses. Our data provide one of the best current constraints on w, demonstrating that samples with ∼5% CC SN contamination can give competitive cosmological constraints when the contaminating distribution is marginalized over in a Bayesian framework.

Searching for sterile neutrinos in dynamical dark energy cosmologies

We investigate how the dark energy properties change the cosmological limits on sterile neutrino parameters by using recent cosmological observations. We consider the simplest dynamical dark energy models, the wCDM model and the holographic dark energy (HDE) model, to make an analysis. The cosmological observations used in this work include the Planck 2015 CMB temperature and polarization data, the baryon acoustic oscillation data, the type Ia supernova data, the Hubble constant direct measurement data, and the Planck CMB lensing data. We find that, mv,terileff < 0.2675 eV and Ne f f < 3.5718 for ACDM cosmology, mv,terileff < 0.5313 eV and Ne f f < 3.5008 for wCDM cosmology, and raffterile < 0.1989 eV and Ne f f < 3.6701 for HDE cosmology, from the constraints of the combination of these data. Thus, without the addition of measurements of growth of structure, only upper limits on both mv,terileff and Ne f f can be derived, indicating that no evidence of the existence of a sterile neutrino species with eV-scale mass is found in this analysis. Moreover, compared to the ACDM model, in the wCDM model the limit on mv,terileff becomes much looser, but in the HDE model the limit becomes much tighter. Therefore, the dark energy properties could significantly influence the constraint limits of sterile neutrino parameters.

Curvature from Strong Gravitational Lensing: A Spatially Closed Universe or Systematics?

Abstract Model-independent constraints on the spatial curvature are not only closely related to important problems, such as the evolution of the universe and properties of dark energy, but also provide a test of the validity of the fundamental Copernican principle. In this paper, with the distance sum rule in the Friedmann–Lemaître–Robertson–Walker metric, we achieve model-independent measurements of the spatial curvature from the latest type Ia supernovae and strong gravitational lensing (SGL) observations. We find that a spatially closed universe is preferred. Moreover, by considering different kinds of velocity dispersion and subsamples, we study possible factors that might affect model-independent estimations for the spatial curvature from SGL observations. It is suggested that the combination of observational data from different surveys might cause a systematic bias, and the tension between the spatially flat universe and SGL observations is alleviated when the subsample only from the Sloan Lens ACS Survey is used or a more complex treatment for the density profile of lenses is considered.

Bias to CMB lensing reconstruction from temperature anisotropies due to large-scale galaxy motions

Gravitational lensing of the cosmic microwave background (CMB) is expected to be amongst the most powerful cosmological tools for ongoing and upcoming CMB experiments. In this work, we investigate a bias to CMB lensing reconstruction from temperature anisotropies due to the kinematic Sunyaev-Zel'dovich (kSZ) effect, that is, the Doppler shift of CMB photons induced by Compton-scattering off moving electrons. The kSZ signal yields biases due to both its own intrinsic non-Gaussianity and its non-zero cross-correlation with the CMB lensing field (and other fields that trace the large-scale structure). This kSZ-induced bias affects both the CMB lensing auto-power spectrum and its cross-correlation with low-redshift tracers. Furthermore, it cannot be removed by multifrequency foreground separation techniques because the kSZ effect preserves the blackbody spectrum of the CMB. While statistically negligible for current datasets, we show that it will be important for upcoming surveys, and failure to account for it can lead to large biases in constraints on neutrino masses or the properties of dark energy. For a Stage 4 CMB experiment, the bias can be as large as $\approx$ 15% or 12% in cross-correlation with LSST galaxy lensing convergence or galaxy overdensity maps, respectively, when the maximum temperature multipole used in the reconstruction is $\ell_{\rm max} = 4000$, and about half of that when $\ell_{\rm max} = 3000$. Similarly, we find that the CMB lensing auto-power spectrum can be biased by up to several percent. These biases are many times larger than the expected statistical errors. Reducing $\ell_{\rm max}$ can significantly mitigate the bias at the cost of a decrease in the overall lensing reconstruction signal-to-noise. Polarization-only reconstruction may be the most robust mitigation strategy.

A Model of Dark Matter and Dark Energy Based on Relativizing Newton’s Physics

The nature and properties of dark matter and dark energy in the universe are among the outstanding open issues of modern cosmology. Despite extensive theoretical and empirical efforts, the question “what is dark matter made of?” has not been answered satisfactorily. Candidates proposed to identify particle dark matter span over ninety orders of magnitude in mass, from ultra-light bosons, to massive black holes. Dark energy is a greater enigma. It is believed to be some kind of negative vacuum energy, responsible for driving galaxies apart in accelerated motion. In this article we take a relativistic approach in theorizing about dark matter and dark energy. Our approach is based on our recently proposed Information Relativity theory. Rather than theorizing about the identities of particle dark matter candidates, we investigate the relativistic effects on large scale celestial structures at their recession from an observer on Earth. We analyze a simplified model of the universe, in which large scale celestial bodies, like galaxies and galaxy clusters, are non-charged compact bodies that recede rectilinearly along the line-of-sight of an observer on Earth. We neglect contributions to dark matter caused by the rotation of celestial structures (e.g., the rotation of galaxies) and of their constituents (e.g., rotations of stars inside galaxies). We define the mass of dark matter as the complimentary portion of the derived relativistic mass, such that at any given recession velocity the sum of the two is equal to the Newtonian mass. The emerging picture from our analysis could be summarized as follows: 1) At any given redshift, the dark matter of a receding body exists in duality to its observable matter. 2) The dynamical interaction between the dark and the observed matter is determined by the body’s recession velocity (or redshift). 3) The observable matter mass density decreases with its recession velocity, with matter transforming to dark matter. 4) For redshifts z 0.5 the universe is dominated by dark matter. 5) Consistent with observational data, at redshift z = 0.5, the densities of matter and dark matter in the universe are predicted to be equal. 6) At redshift equaling the Golden Ratio (z ≈ 1.618), baryonic matter undergoes a quantum phase transition. The universe at higher redshifts is comprised of a dominant dark matter alongside with quantum matter. 7) Contrary to the current conjecture that dark energy is a negative vacuum energy that might interact with dark matter, comparisons of our theoretical results with observational results of ΛCDM cosmologies, and with observations of the relative densities of matter and dark energy at redshift z ≈ 0.55, allow us to conclude that dark energy is the energy carried by dark matter. 8) Application of the model to the case of rotating bodies, which will be discussed in detail in a subsequent paper, raises the intriguing possibility that the gravitational force between two bodies of mass is mediated by the entanglement of their dark matter components.

Statistical Hierarchy of Varying Speed of Light Cosmologies

Abstract Many varying speed of light (VSL) theories have been developed recently. Here we address the issue of their observational verification in a fully comprehensive way. By using the most updated cosmological probes, we test three different candidates for a VSL theory (Barrow &amp; Magueijo, Avelino &amp; Martins, and Moffat). We consider many different Ansätze for both the functional form of c(z) and the dark energy dynamics. We compare these results using a reliable statistical tool such as the Bayesian evidence. We find that the present cosmological data are perfectly compatible with any of these VSL scenarios, but for the Moffat model there is a higher Bayesian evidence ratio in favor of VSL rather than the c = constant ΛCDM scenario. Moreover, in such a scenario, the VSL signal can help to strengthen constraints on the spatial curvature (with indication toward an open universe), to clarify some properties of dark energy (exclusion of a cosmological constant at level), and is also falsifiable in the near future owing to peculiar issues that differentiate this model from the standard one. Finally, we apply an information prior and entropy prior in order to put physical constraints on the models, though still in favor Moffat’s proposal.