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Testing gravity and the concordance model of cosmology, $\Lambda$CDM, at large scales is a key goal of this decade's largest galaxy surveys. Here we present a comparative study of dark matter power spectrum predictions from different numerical codes in the context of three popular theories of gravity that induce scale-independent modifications to the linear growth of structure: nDGP, Cubic Galileon and K-mouflage. In particular, we compare the predictions from full $N$-body simulations, two $N$-body codes with approximate time integration schemes, a parametrised modified $N$-body implementation and the analytic halo model reaction approach. We find the modification to the $\Lambda$CDM spectrum is in $2\%$ agreement for $z\leq1$ and $k\leq 1~h/{\rm Mpc}$ over all gravitational models and codes, in accordance with many previous studies, indicating these modelling approaches are robust enough to be used in forthcoming survey analyses under appropriate scale cuts. We further make public the new code implementations presented, specifically the halo model reaction K-mouflage implementation and the relativistic Cubic Galileon implementation., Comment: 20 pages, 4 figures, 4 tables

To fully exploit the data from next generation surveys, we need an accurate modelling of the matter power spectrum up to non-linear scales. Therefore in this work we present the halo model reaction framework for the Generalized Cubic Covariant Galileon (GCCG) model, a modified gravity model within the Horndeski class of theories which extends the cubic covariant Galileon (G3) by including power laws of the derivatives of the scalar field in the K-essence and cubic terms. We modify the publicly available software ReACT for the GCCG in order to obtain an accurate prediction of the non-linear power spectrum. In the limit of the G3 model we compare the modified ReACT code to $N$-body simulations and we find agreement within 5\% for a wide range of scales and redshifts. We then study the relevant effects of the modifications introduced by the GCCG on the non-linear matter power spectrum. Finally, we provide forecasts from spectroscopic and photometric primary probes by next generation surveys using a Fisher matrix method. We show that future data will be able to constrain at 1$\sigma$ the two additional parameters of the model at the percent level and that considering non-linear corrections to the matter power spectrum beyond the linear regime is crucial to obtain this result., Comment: 17 pages, 7 figures, code available at https://github.com/nebblu/ACTio-ReACTio

We study a symmetric teleparallel gravity with a Lagrangian of logarithmic form. The full model leads to an accelerated universe and for specific values of the free parameters the Hubble rate reduces to the well-known Dvali-Gabadadze-Porrati model, though the evolution of the gravitational potentials are different. We consider different branches of the logarithmic model, among which are self-accelerated branch and normal branch. The phenomenology of both the background and linear perturbations is discussed, including all the relevant effects on cosmic microwave background radiation (CMB) angular power spectrum, lensing and matter power spectra. To this purpose, we modified the Einstein-Boltzmann code mgcamb. Finally, we derive bounds on the free parameters which are in agreement with early dark energy constraint from CMB and big bang nucleosynthesis constraint on the helium abundance., Comment: 24 pages, 14 figures

Within the $f(Q)$-gravity framework we perform a phenomenological study of the cosmological observables in light of the degeneracy between neutrinos physics and the modified gravity parameter and we identify specific patterns which allow to break such degeneracy. We also provide separately constraints on the total mass of the neutrinos, $\Sigma m_{\nu}$, and on the effective number of neutrino species, $N_{\rm eff}$, using cosmic microwave background (CMB), baryon acoustic oscillation (BAO), redshift space distortion (RSD), supernovae (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements. The strongest upper bound on the total mass of the neutrinos is found for the combination of CMB+BAO+RSD+SNIa and it is $\Sigma m_\nu<0.277$ eV at 95\% C.L. For the same combination of data we find $N_{\rm eff}=2.93^{+0.31}_{-0.34}$ at 95\% C.L. We also find that all combinations of data we consider, prefer a stronger gravitational interaction than $\Lambda$CDM. Finally, we consider the $\chi^2$ and deviance information criterion statistics and find the $f(Q)+\Sigma m_\nu$ model to be statistically supported by data over the standard scenario. On the contrary $f(Q)+N_{\rm eff}$ is supported by CMB+BAO+RSD+SNIa but a moderate evidence against it is found with GC and WL data., Comment: 11 pages; 5 figures; 4 tables, accepted for publication in PRD

We study observational constraints on the non-metricity $f(Q)$-gravity which reproduces an exact $\Lambda$CDM background expansion history while modifying the evolution of linear perturbations. To this purpose we use Cosmic Microwave Background (CMB) radiation, baryonic acoustic oscillations (BAO), redshift-space distortions (RSD), supernovae type Ia (SNIa), galaxy clustering (GC) and weak gravitational lensing (WL) measurements. We set stringent constraints on the parameter of the model controlling the modifications to the gravitational interaction at linear perturbation level. We find the model to be statistically preferred by data over the $\Lambda$CDM according to the $\chi^2$ and deviance information criterion statistics for the combination with CMB, BAO, RSD and SNIa. This is mostly associated to a better fit to the low-$\ell$ tail of CMB temperature anisotropies., Comment: 5 pages, 1 figure, 2 tables, accepted for publication in PRD

We investigate the generalized cubic covariant Galileon model, a kinetically driven dark energy model within the Horndeski class of theories. The model extends the cubic covariant Galileon by including power laws of the field derivatives in the K-essence and cubic terms which still allow for tracker solutions. We study the shape of the viable parameter space by enforcing stability conditions which include the absence of ghost, gradient and tachyon instabilities and the avoidance of strong coupling at early time. We study here the relevant effects of the modifications induced by the model on some cosmological observables such as the cosmic microwave background (CMB), the lensing potential auto-correlation and the matter power spectrum. For this goal, we perform parameter estimation using data of CMB temperature and polarization, baryonic acoustic oscillations (BAO), redshift-space distortions (RSD), supernovae type Ia (SNIa) and Cepheids. Data analysis with CMB alone finds that the today's Hubble parameter $H_0$ is consistent with its determination from Cepheids at $1\sigma$, resolving the famous tension of the cosmological standard models. The joint analysis of CMB, BAO, RSD and SNIa sets a lower bound for the sum of neutrino masses which is $\Sigma m_\nu >0.11$ eV at 1$\sigma$, in addition to the usual upper limit. The model selection analysis based on the effective $\chi_\text{eff}^2$ and Deviance Information Criterion is not able to clearly identify the statistically favored model between $\Lambda$CDM and the generalized cubic covariant Galileon, from which we conclude that the latter model deserves further studies., Comment: 13 pages, 10 figures, 3 tables