Baryon Acoustic Oscillation Data Research Articles

Cosmological constraints on Horndeski gravity in light of GW170817

The discovery of the electromagnetic counterpart to GW170817 severely constrains the tensor mode propagation speed, eliminating a large model space of Horndeski theory. We use the cosmic microwave background data from Planck and the joint analysis of the BICEP2/Keck Array and Planck, galaxy clustering data from the SDSS LRG survey, BOSS baryon acoustic oscillation data, and redshift space distortion measurements to place constraints on the remaining Horndeski parameters. We evolve the Horndeski parameters as power laws with both the amplitude and power law index free. We find a 95% CL upper bound on the present-day coefficient of the Hubble friction term in the cosmological propagation of gravitational waves is 2.38, whereas General Relativity gives 2 at all times. While an enhanced friction suppresses the amplitude of the reionization bump of the primordial B-mode power spectrum at ℓ<10, our result limits the suppression to be less than 0.8%. This constraint is primarily due to the scalar integrated Sachs-Wolfe effect in temperature fluctuations at low multipoles.

Model independentH(z) reconstruction using the cosmic inverse distance ladder

Recent distance ladder determinations of the Hubble constant $H_0$ disagree at about the $3.5\sigma$ level with the value determined from Planck measurements of the cosmic microwave background (CMB) assuming a $\Lambda$CDM cosmology. This discrepancy has prompted speculation that new physics might be required beyond that assumed in the $\Lambda$CDM model. In this paper, we apply the inverse distance ladder to fit a parametric form of $H(z)$ to baryon acoustic oscillation (BAO) and Type Ia supernova data together with priors on the sound horizon at the end of the radiation drag epoch, $r_d$. We apply priors on $r_d$, based on inferences from either Planck or the Wilkinson Microwave Anistropy Probe (WMAP), and demonstrate that these values are consistent with CMB-independent determinations of $r_d$ derived from measurements of the primordial deuterium abundance, BAO and supernova data assuming the $\Lambda$CDM cosmology. The $H(z)$ constraints that we derive are independent of detailed physics within the dark sector at low redshifts, relying only on the validity of the Friedmann-Robertson-Walker (FRW) metric of General Relativity. For each assumed prior on $r_d$, we find consistency with the inferred value of $H_0$ and the Planck $\Lambda$CDM value and corresponding tension with the distance ladder estimate.

Measuring the spectral running from cosmic microwave background and primordial black holes

We constrain the spectral running by combining cosmic microwave background (CMB) data, baryon acoustic oscillation (BAO) data and the constraint from primordial black holes (PBHs). We find that the constraint from PBHs has a significant impact on the running of running of scalar spectral index, and a power-law scalar power spectrum without running is consistent with observational data once the constraint from PBHs is taken into account. In addition, from the constraints on the slow-roll parameters, the derived tensor spectral index in the single-field slow-roll inflation model is quite small, namely |n_t|lesssim 9.3times 10^{-3} which will be very difficult to be measured by CMB data only in the future, and the absolute value of derived running of tensor spectral index is not larger than 2.1times 10^{-4} at 95% confidence level.

Analysis with observational constraints in Lambda -cosmology in f(R,\xa0T) gravity

An exact cosmological solution of Einstein’s field equations (EFEs) is derived for a dynamical vacuum energy in f(R, T) gravity for Friedmann–Lemaitre–Robertson–Walker (FLRW) space-time. A parametrization of the Hubble parameter is used to find a deterministic solution of the EFE. The cosmological dynamics of our model is discussed in detail. We have analyzed the time evolution of the physical parameters and obtained their bounds analytically. Moreover, the behavior of these parameters are shown graphically in terms of the redshift ‘z’. Our model is consistent with the formation of structure in the Universe. The role of the f(R, T) coupling constant lambda is discussed in the evolution of the equation of state parameter. The statefinder and Om diagnostic analysis is used to distinguish our model with other dark energy models. The maximum likelihood analysis has been reviewed to obtain the constraints on the Hubble parameter H_0 and the model parameter n by taking into account the observational Hubble data set H(z), the Union 2.1 compilation data set SNeIa, the Baryon Acoustic Oscillation data BAO, and the joint data set H(z) + mathrm{SNeIa} and H(z) + mathrm{SNeIa} + mathrm{BAO} . It is demonstrated that the model is in good agreement with various observations.

Constraints on brane inflation after Planck 2015: Impacts of the latest local measurement of the Hubble constant

We investigate the observational constraints on three typical brane inflation models by considering the latest local measurement of the Hubble constant in the global fit. We also employ other observational data, including the Planck 2015 CMB data, the BICEP2/Keck Array B-mode data, and the baryon acoustic oscillations data, in our analysis. Previous studies have shown that the addition of the latest local $H_{0}$ measurement favors a larger spectral index, and can exert a significant influence on the model selection of inflation. In this work, we investigate its impacts on the status of brane inflation models. We find that, when the direct $H_{0}$ measurement is considered, the prototype model of brane inflation is still in good agreement with the current observational data within the $2\sigma$ level range. For the KKLMMT model, the consideration of the $H_{0}$ measurement allows the range of the parameter $\beta$ to be amplified to ${\cal O}(10^{-2})$, which slightly alleviates the fine-tuning problem. For the IR DBI model, the addition of the $H_{0}$ measurement does not provide a better fit. These results show that the consideration of the new $H_{0}$ prior can exert a considerable influence on the brane inflation models. At last, we show that, when $\beta \lesssim 1.1$, the equilateral non-Gaussianity in the IR DBI inflation model is compatible with the current CMB data at the 1$\sigma$ level.

An improved model-independent assessment of the late-time cosmic expansion

In the current work, we have implemented an extension of the standard Gaussian Process formalism, namely the Multi-Task Gaussian Process with the ability to perform a joint learning of several cosmological data simultaneously. We have utilised the “low-redshift” expansion rate data from Supernovae Type-Ia (SN), Baryon Acoustic Oscillations (BAO) and Cosmic Chronometers (CC) data in a joint analysis. We have tested several possible models of covariance functions and find very consistent estimates for cosmologically relevant parameters. In the current formalism, we also find provisions for heuristic arguments which allow us to select the best-suited kernel for the reconstruction of expansion rate data. We also utilised our method to account for systematics in CC data and find an estimate of H0 = 68.52+0.94 + 2.51 (sys)−0.94 km/s Mpc−1 and a corresponding rd = 145.61+2.82 − 2.82 − 4.3 (sys) Mpc as our primary result. Subsequently, we find constraints on the present deceleration parameter q0 = −0.52 ± 0.06 and the transition redshift zT = 0.64+0.12−0.09. All the estimated cosmological parameters are found to be in good agreement with the standard ΛCDM scenario. Including the local model-independent H0 estimate to the analysis we find H0 = 71.40 + 0.30 + 1.65 (sys)− 0.30 km/s Mpc−1 and the corresponding rd = 141.29 + 1.31 −1.31−2.63 (sys) Mpc. Also, the constraints on rd H0 remain consistent throughout our analysis and also with the model-dependent CMB estimate. Using the \U0001d4aam(z) diagnostic, we find that the concordance model is very consistent within the redshift range z ≲ 2 and mildly discrepant for z ≳ 2.

Cosmological implications of scale-independent energy-momentum squared gravity: Pseudo nonminimal interactions in dark matter and relativistic relics

In this paper, we introduce a scale-independent energy-momentum squared gravity (EMSG) that allows different gravitational couplings for different types of sources, which may lead to scenarios with many interesting applications/implications in cosmology. In the present study, to begin with, we study a modification of the $\Lambda$ cold dark matter ($\Lambda$CDM) model, where photons and baryons couple to the spacetime as in general relativity, while the cold dark matter and relativistic relics (neutrinos and any other relativistic relics) couple to the spacetime in accordance with EMSG. This scenario induces pseudo nonminimal interactions on these components, leading to modification at both the background and perturbative levels. A consequence of this scenario is that the dimensionless free parameter of the theory may induce direct changes on the effective number of the relativistic species, without the need to introduce new extra species. In order to quantify the observational consequences of the cosmological scenario, we use the cosmic microwave background Planck data (temperature, polarization, and lensing power spectrum) and baryonic acoustic oscillations data. We find that the free model parameter is too small to induce statistically significant corrections on the $\Lambda$CDM model due to EMSG. We deduce that the model presented here is quite rich with promising cosmological applications/implications that deserve further investigations.

Cosmological Constraints from Low-Redshift Data

In this paper we summarise the constraints that low-redshift data --such as supernovae Ia (SN Ia), baryon acoustic oscillations (BAO) and cosmic chronometers (CC)-- are able to set on the concordance model and its extensions, as well as on inhomogeneous but isotropic models. We provide a broad overlook into these cosmological scenarios and several aspects of data analysis. In particular, we review a number of systematic issues of SN Ia analysis that include magnitude correction techniques, selection bias and their influence on the inferred cosmological constraints. Furthermore, we examine the isotropic and anisotropic components of the BAO data and their individual relevance for cosmological model-fitting. We extend the discussion presented in earlier works regarding the inferred dynamics of cosmic expansion and its present rate from the low-redshift data. Specifically, we discuss the cosmological constraints on the accelerated expansion and related model-selections. In addition, we extensively talk about the Hubble constant problem, then focus on the low-redshift data constraint on $H_0$ that is based on CC. Finally, we present the way in which this result compares the two of high-redshift $H_0$ estimate and local (redshift zero) measurements that are in tension.

New constraints on the distance duality relation from the local data

The cosmic distance duality relation (DDR), which connects the angular diameter distance and luminosity distance through a simple formula $D_A(z)(1+z)^2/D_L(z)\equiv1$, is an important relation in cosmology. Therefore, testing the validity of DDR is of great importance. In this paper, we test the possible violation of DDR using the available local data including type Ia supernovae (SNe Ia), galaxy clusters and baryon acoustic oscillations (BAO). We write the modified DDR as $D_A(z)(1+z)^2/D_L(z)=\eta(z)$, and consider two different parameterizations of $\eta(z)$, namely $\eta_1(z)=1+\eta_0 z$ and $\eta_2(z)=1+\eta_0 z/(1+z)$. The luminosity distance from SNe Ia are compared with the angular diameter distance from galaxy clusters and BAO at the same redshift. Two different cluster data are used here, i.e. elliptical clusters and spherical clusters. The parameter $\eta_0$ is obtained using the Markov chain Monte Carlo methods. It is found that $\eta_0$ can be strictly constrained by the elliptical clusters + BAO data, with the best-fitting values $\eta_0=-0.04\pm 0.12$ and $\eta_0=-0.05\pm 0.22$ for the first and second parametrizations, respectively. However, the spherical clusters + BAO data couldn't strictly constrain $\eta_0$ due to the large intrinsic scatter. In any case studied here, no evidence for the violation of DDR is found.

Exploring neutrino mass and mass hierarchy in the scenario of vacuum energy interacting with cold dark matter**Supported by National Natural Science Foundation of China (11522540, 11690021), the Top-Notch Young Talents Program of China and the Provincial Department of Education of Liaoning (L2012087)

We investigate the constraints on total neutrino mass in the scenario of vacuum energy interacting with cold dark matter. We focus on two typical interaction forms, i.e., Q = βH ρc and Q = βH ρΛ. To avoid the occurrence of large-scale instability in interacting dark energy cosmology, we adopt the parameterized post-Friedmann approach to calculate the perturbation evolution of dark energy. We employ observational data, including the Planck cosmic microwave background temperature and polarization data, baryon acoustic oscillation data, a JLA sample of type Ia supernovae observation, direct measurement of the Hubble constant, and redshift space distortion data. We find that, compared with those in the ΛCDM model, much looser constraints on Σmν are obtained in the Q = βH ρc model, whereas slightly tighter constraints are obtained in the Q = βH ρΛ model. Consideration of the possible mass hierarchies of neutrinos reveals that the smallest upper limit of Σmν appears in the degenerate hierarchy case. By comparing the values of , we find that the normal hierarchy case is favored over the inverted one. In particular, we find that the difference in the Q = βH ρc model. In addition, we find that β = 0 is consistent with the current observations in the Q = βH ρc model, and β < 0 is favored at more than the 1 σ level in the Q = βH ρΛ model.

The H0 and σ8 tensions and the scale invariant spectrum

In a previous communication [1] it was shown that a joint analysis of Cosmic Microwave Background (CMB) data and the current measurement of the local expansion rate favours a model with a scale invariant spectrum (HZP) over the minimal ΛCDM scenario provided that the effective number of relativistic degrees of freedom, Neff, is taken as a free parameter. Such a result is basically obtained due to the Hubble Space Telescope (HST) value of the Hubble constant, H0 = 73.24 ± 1.74 km . s−1.Mpc−1 (68% C.L.), as the CMB data alone discard the HZP+Neff model. Although such a model is not physically motivated by current scenarios of the early universe, observations pointing to a scale invariant spectrum may indicate that the origin of cosmic perturbations lies in an unknown physical process. Here, we extend the previous results performing a Bayesian analysis using joint CMB, HST, and Baryon Acoustic Oscillations (BAO) measurements. In order to take into account the well-known tension on the value of the fluctuation amplitude parameter, σ8, we also consider Cluster Number counts (CN) and Weak Lensing (WL) data. We use two different samples of BAO data, which are obtained using two-point spatial (BAO 2PCF) and angular (BAO 2PACF) correlation functions. Our results show that the joint CMB+HST+WL+NC dataset favor the extensions of the ΛCDM model over its minimal parameterization. Also, analysis with the BAO 2PCF always discard the HZP+Neff model with respect to standard scenario, whereas the combinations using BAO 2PACF favor the former model. We, therefore, find that all dataset disfavor the ΛCDM model with respect to the HZP+Neff extension, the only exception being the joint analysis with BAO (2PCF).

Dark Matter Equation of State through Cosmic History

Cold dark matter is a crucial constituent of the current concordance cosmological model. Having a vanishing equation of state (EOS), its energy density scales with the inverse cosmic volume and is thus uniquely described by a single number, its present abundance. We test the inverse cosmic volume law for dark matter (DM) by allowing its EOS to vary independently in eight redshift bins in the range z=10^{5} and z=0. We use the latest measurements of the cosmic microwave background radiation from the Planck satellite and supplement them with baryon acoustic oscillation (BAO) data from the 6dF and SDSS-III BOSS surveys and with the Hubble Space Telescope (HST) key project data. We find no evidence for nonzero EOS in any of the eight redshift bins. With Planck data alone, the DM abundance is most strongly constrained around matter-radiation equality ω_{g}^{eq}=0.1193_{-0.0035}^{+0.0036} (95%C.L.), whereas its present-day value is more weakly constrained: ω_{g}^{(0)}=0.16_{-0.10}^{+0.12} (95%C.L.). Adding BAO or HST data does not significantly change the ω_{g}^{eq} constraint, while ω_{g}^{(0)} tightens to 0.160_{-0.065}^{+0.069} (95%C.L.) and 0.124_{-0.067}^{+0.081} (95%C.L.), respectively. Our results constrain for the first time the level of "coldness" required of the DM across various cosmological epochs and show that the DM abundance is strictly positive at all times.

Do cosmological data rule out f(R) with w≠−1 ?

We review the equation of state (EoS) approach to dark sector perturbations and apply it to $f(\mathcal{R})$ gravity models of dark energy. We show that the EoS approach is numerically stable and use it to set observational constraints on designer models. Within the EoS approach we build an analytical understanding of the dynamics of cosmological perturbations for the designer class of $f(\mathcal{R})$ gravity models, characterized by the parameter ${B}_{0}$ and the background equation of state of dark energy $w$. When we use the Planck cosmic microwave background temperature anisotropy, polarization, and lensing data as well as the baryonic acoustic oscillation data from SDSS and WiggleZ, we find ${B}_{0}&lt;0.006$ (95% C.L.) for the designer models with $w=\ensuremath{-}1$. Furthermore, we find ${B}_{0}&lt;0.0045$ and $|w+1|&lt;0.002$ (95% C.L.) for the designer models with $w\ensuremath{\ne}\ensuremath{-}1$. Previous analyses found similar results for designer and Hu-Sawicki $f(\mathcal{R})$ gravity models using the effective field theory approach [Raveri et al., Phys. Rev. D 90, 043513 (2014); Hu et al., Mon. Not. R. Astron. Soc. 459, 3880 (2016)]; therefore this hints for the fact that generic $f(\mathcal{R})$ models with $w\ensuremath{\ne}\ensuremath{-}1$ can be tightly constrained by current cosmological data, complementary to solar system tests [Brax et al., Phys. Rev. D 78, 104021 (2008); Faulkner et al., Phys. Rev. D 76, 063505 (2007)]. When compared to a $w\mathrm{CDM}$ fluid with the same sound speed, we find that the equation of state for $f(\mathcal{R})$ models is better constrained to be close to $\ensuremath{-}1$ by about an order of magnitude, due to the strong dependence of the perturbations on $w$.

Isotropic vs. anisotropic components of BAO data: a tool for model selection

We conduct a selective analysis of the isotropic (DV) and anisotropic (AP) components of the most recent Baryon Acoustic Oscillations (BAO) data. We find that these components provide significantly different constraints and could provide strong diagnostics for model selection, also in view of more precise data to arrive. For instance, in the ΛCDM model we find a mild tension of ∼ 2 σ for the Ωm estimates obtained using DV and AP separately. Considering both Ωk and w as free parameters, we find that the concordance model is in tension with the best-fit values provided by the BAO data alone at 2.2σ. We complemented the BAO data with the Supernovae Ia (SNIa) and Observational Hubble datasets to perform a joint analysis on the ΛCDM model and its standard extensions. By assuming ΛCDM scenario, we find that these data provide H0 = 69.4 ± 1.7 km/s Mpc−1 as the best-fit value for the present expansion rate. In the kΛCDM scenario we find that the evidence for acceleration using the BAO data alone is more than ∼ 5.8σ, which increases to 8.4 σ in our joint analysis.

Test of the cosmic transparency with the standard candles and the standard ruler

In this paper, the cosmic transparency is constrained by using the latest baryon acoustic oscillation (BAO) data and the type Ia supernova data with a model-independent method. We find that a transparent universe is consistent with observational data at the [Formula: see text] confidence level, except for the case of BAO+ Union 2.1 without the systematic errors where a transparent universe is favored only at the [Formula: see text] confidence level. To investigate the effect of the uncertainty of the Hubble constant on the test of the cosmic opacity, we assume [Formula: see text] to be a free parameter and obtain that the observations favor a transparent universe at the [Formula: see text] confidence level.

Future Cosmological Constraints From Fast Radio Bursts

Abstract We consider the possible observation of fast radio bursts (FRBs) with planned future radio telescopes, and investigate how well the dispersions and redshifts of these signals might constrain cosmological parameters. We construct mock catalogs of FRB dispersion measure (DM) data and employ Markov Chain Monte Carlo analysis, with which we forecast and compare with existing constraints in the flat ΛCDM model, as well as some popular extensions that include dark energy equation of state and curvature parameters. We find that the scatter in DM observations caused by inhomogeneities in the intergalactic medium (IGM) poses a big challenge to the utility of FRBs as a cosmic probe. Only in the most optimistic case, with a high number of events and low IGM variance, do FRBs aid in improving current constraints. In particular, when FRBs are combined with CMB+BAO+SNe+H 0 data, we find the biggest improvement comes in the constraint. Also, we find that the dark energy equation of state is poorly constrained, while the constraint on the curvature parameter, Ω k , shows some improvement when combined with current constraints. When FRBs are combined with future baryon acoustic oscillation (BAO) data from 21 cm Intensity Mapping, we find little improvement over the constraints from BAOs alone. However, the inclusion of FRBs introduces an additional parameter constraint, , which turns out to be comparable to existing constraints. This suggests that FRBs provide valuable information about the cosmological baryon density in the intermediate redshift universe, independent of high-redshift CMB data.

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.

Towards New Constraints in Extended Theories of Gravity: Cosmography and Gravitational-Wave Signals from Neutron Stars

Combined cosmological, astrophysical and numerical tests may shed some light on the viability of theories of gravity beyond Einsteinian relativity. In this letter, we present two different techniques providing complementary ways of testing new physics beyond the Λ CDM cosmological paradigm. First, we shall present some of the latest progress and shortcomings in the cosmographic model-independent approach for several modified gravity theories using supernovae catalogues, baryonic acoustic oscillation data and H ( z ) differential age compilations. Second, we shall show how once the Einsteinian paradigm is abandoned, the phenomenology of neutron stars changes dramatically since neutron-star masses can be much larger than their General Relativity counterparts. Consequently, the total energy available for radiating gravitational waves could be of the order of several solar masses, and thus a merger of these stars constitutes a privileged wave source. Unfortunately at the present time our persisting lack of understanding in the strong interaction sector does not allow to distinguish the alternative theories from the usual General Relativity predictions.

Measuring growth index in a universe with massive neutrinos: A revisit of the general relativity test with the latest observations

We make a consistency test for the general relativity (GR) through measuring the growth index γ in a universe with massive (sterile/active) neutrinos. We employ the redshift space distortion measurements to do the analysis. To constrain other cosmological parameters, we also use other cosmological measurements, including the Planck 2015 cosmic microwave background temperature and polarization data, the baryon acoustic oscillation data, the type Ia supernova JLA data, the weak lensing galaxy shear data, and the Planck 2015 lensing data. In a universe with massive sterile neutrinos, we obtain γ=0.624−0.050+0.055, with the tension with the GR prediction γ=0.55 at the 1.48σ level, showing that the consideration of sterile neutrinos still cannot make the true measurement of γ be well consistent with the GR prediction. In a universe with massive active neutrinos, we obtain γ=0.663±0.045 for the normal hierarchy case, γ=0.661−0.050+0.044 for the degenerate hierarchy case, and γ=0.668−0.051+0.045 for the inverted hierarchy case, with the tensions with GR all at beyond the 2σ level. We find that the consideration of massive active neutrinos (no matter what mass hierarchy is considered) almost does not influence the measurement of the growth index γ.

Elucidating ΛCDM: Impact of Baryon Acoustic Oscillation Measurements on the Hubble Constant Discrepancy

Abstract We examine the impact of baryon acoustic oscillation (BAO) scale measurements on the discrepancy between the value of the Hubble constant (H 0) inferred from the local distance ladder and that from Planck cosmic microwave background (CMB) data. While the BAO data alone cannot constrain H 0, we show that combining the latest BAO results with WMAP, Atacama Cosmology Telescope (ACT), or South Pole Telescope (SPT) CMB data produces values of H 0 that are lower than the distance ladder, independent of Planck, and that this downward pull was less apparent in some earlier analyses that used only angle-averaged BAO scale constraints rather than full anisotropic information. At the same time, the combination of BAO and CMB data also disfavors the lower values of H 0 preferred by the Planck high-multipole temperature power spectrum. Combining galaxy and Lyα forest BAO with a precise estimate of the primordial deuterium abundance produces km s−1 Mpc−1 for the flat model. This value is completely independent of CMB anisotropy constraints and is lower than the latest distance ladder constraint, although tension also exists between the galaxy BAO and Lyα BAO. These results show that it is not possible to explain the H 0 disagreement solely with a systematic error specific to the Planck data. The fact that tensions remain even after the removal of any single data set makes this intriguing puzzle all the more challenging to resolve.