Models where dark matter and dark energy interact with each other have been proposed to solve the coincidence problem. We review the motivations underlying the need to introduce such interaction, its influence on the background dynamics and how it modifies the evolution of linear perturbations. We test models using the most recent observational data and we find that the interaction is compatible with the current astronomical and cosmological data. Finally, we describe the forthcoming data sets from current and future facilities that are being constructed or designed that will allow a clearer understanding of the physics of the dark sector.

https://iopscience.iop.org/article/10.1088/0034-4885/79/9/096901/pdf

Dark matter and dark energy interactions: theoretical challenges, cosmological implications and observational signatures

Cosmology Intertwined: A Review of the Particle Physics, Astrophysics, and Cosmology Associated with the Cosmological Tensions and Anomalies

MontePython 3: Boosted MCMC sampler and other features

MontePython is a parameter inference package for cosmology. We present the latest development of the code over the past couple of years. We explain, in particular, two new ingredients both contributing to improve the performance of Metropolis-Hastings sampling: an adaptation algorithm for the jumping factor, and a calculation of the inverse Fisher matrix, which can be used as a proposal density. We present several examples to show that these features speed up convergence and can save many hundreds of CPU-hours in the case of difficult runs, with a poor prior knowledge of the covariance matrix. We also summarise all the functionalities of MontePython in the current release, including new likelihoods and plotting options.

MontePython 3: boosted MCMC sampler and other features.

Models where Dark Matter and Dark Energy interact with each other have been proposed to solve the coincidence problem. We review the motivations underlying the need to introduce such interaction, its influence on the background dynamics and how it modifies the evolution of linear perturbations. We test models using the most recent observational data and we find that the interaction is compatible with the current astronomical and cosmological data. Finally, we describe the forthcoming data sets from current and future facilities that are being constructed or designed that will allow a clearer understanding of the physics of the dark sector.

Dark Matter and Dark Energy Interactions: Theoretical Challenges, Cosmological Implications and Observational Signatures

The 2-point angular correlation function $w(\ensuremath{\theta})$ (2PACF), where $\ensuremath{\theta}$ is the angular separation between pairs of galaxies, provides the transversal baryon acoustic oscillation (BAO) signal almost model independently. In this paper we use 409 337 luminous red galaxies in the redshift range $z=[0.440,0.555]$ obtained from the tenth data release of the Sloan Digital Sky Survey (SDSS DR10) to estimate ${\ensuremath{\theta}}_{\mathrm{BAO}}(z)$ from the 2PACF at six redshift shells. Since noise and systematics can hide the BAO signature in the $w\text{\ensuremath{-}}\ensuremath{\theta}$ plane, we also discuss some criteria to localize the acoustic bump. We identify two sources of model dependence in the analysis, namely, the value of the acoustic scale from cosmic microwave background (CMB) measurements and the correction in the ${\ensuremath{\theta}}_{\mathrm{BAO}}(z)$ position due to projection effects. Constraints on the dark energy equation-of-state parameter $\mathrm{w}(z)$ from the ${\ensuremath{\theta}}_{\mathrm{BAO}}(z)$ diagram are derived, as well as from a joint analysis with current CMB measurements. We find that the standard $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model as well as some of its extensions are in good agreement with these ${\ensuremath{\theta}}_{\mathrm{BAO}}(z)$ measurements.

Baryon acoustic oscillations from the SDSS DR10 galaxies angular correlation function

Following a quasi model-independent approach we measure the transversal BAO mode at high redshift using the two-point angular correlation function (2PACF). The analyses done here are only possible now with the quasar catalogue from the twelfth data release (DR12Q) from the Sloan Digital Sky Survey, because it is spatially dense enough to allow the measurement of the angular BAO signature with moderate statistical significance and acceptable precision. Our analyses with quasars in the redshift interval z [2.20,2.25] produce the angular BAO scale θBAO = 1.77° ± 0.31° with a statistical significance of 2.12 σ (i.e., 97% confidence level), calculated through a likelihood analysis performed using the theoretical covariance matrix sourced by the analytical power spectra expected in the ΛCDM concordance model. Additionally, we show that the BAO signal is robust—although with less statistical significance—under diverse bin-size choices and under small displacements of the quasars' angular coordinates. Finally, we also performed cosmological parameter analyses comparing the θBAO predictions for wCDM and w(a)CDM models with angular BAO data available in the literature, including the measurement obtained here, jointly with CMB data. The constraints on the parameters ΩM, w0 and wa are in excellent agreement with the ΛCDM concordance model.

https://iopscience.iop.org/article/10.1088/1475-7516/2018/04/064/pdf

Angular Baryon Acoustic Oscillation measure at z=2.225 from the SDSS quasar survey

The transverse baryonic acoustic scale from the SDSS DR11 galaxies

The Baryon Acoustic Oscillations (BAO) imprinted a characteristic correlation length in the large-scale structure of the universe that can be used as a standard ruler for mapping out the cosmic expansion history. Here, we discuss the application of the angular two-point correlation function, $w(\theta )$, to a sample of luminous red galaxies of the Sloan Digital Sky Survey (SDSS) and derive two new measurements of the BAO angular scale at $z = 0.235$ and $z = 0.365$. Since noise and systematics may hinder the identification of the BAO signature in the $w - \theta $ plane, we also introduce a potential new method to localize the acoustic bump in a model-independent way. We use these new measurements along with previous data to constrain cosmological parameters of dark energy models and to derive a new estimate of the acoustic scale $r_s$.

Measuring baryon acoustic oscillations with angular two-point correlation function

A non-minimal coupling between the dark matter and dark energy components may offer a way of solving the so-called coincidence problem. In this paper we propose a low-$z$ test for such hypothesis using measurements of the gas mass fraction $f_{\rm{gas}}$ in relaxed and massive galaxy clusters. The test applies to any model whose dilution of dark matter is modified with respect to the standard $a^{-3}$ scaling, as usual in interacting models, where $a$ is the cosmological scale factor. We apply the test to current $f_{\rm{gas}}$ data and perform Monte Carlo simulations to forecast the necessary improvements in number and accuracy of upcoming observations to detect a possible interaction in the cosmological dark sector. Our results show that improvements in the present relative error $\sigma_{\rm{gas}}/f_{\rm{gas}}$ are more effective to achieve this goal than an increase in the size of the $f_{\rm{gas}}$ sample.

G. C. Carvalho

Papers

Baryon acoustic oscillations from the SDSS DR10 galaxies angular correlation function

Angular Baryon Acoustic Oscillation measure at z=2.225 from the SDSS quasar survey

The transverse baryonic acoustic scale from the SDSS DR11 galaxies

Measuring baryon acoustic oscillations with angular two-point correlation function

A low-$z$ test for interacting dark energy