Search

We test the usual hypothesis that the cosmic microwave background (CMB) dipole, its largest anisotropy, is due to our peculiar velocity with respect to the Hubble flow by measuring independently the Doppler and aberration effects on the CMB using Planck 2018 data. We remove the spurious contributions from the conversion of intensity into temperature and arrive at measurements that are independent from the CMB dipole itself for both temperature and polarization maps and both SMICA and NILC component-separation methods. Combining these new measurements with the dipole one, we get the first constraints on the intrinsic CMB dipole. Assuming a standard dipolar lensing contribution, we can put an upper limit on the intrinsic amplitude: 3.7 mK (95% confidence interval). We estimate the peculiar velocity of the Solar System without assuming a negligible intrinsic dipole contribution: v=(300_{-93}^{+111})  km/s with (l,b)=(276±33,51±19)° (SMICA), and v=(296_{-88}^{+111})  km/s with (l,b)=(280±33,50±20)° (NILC) with negligible systematic contributions. These values are consistent with the peculiar velocity hypothesis of the dipole.

We reanalyze the supernova data from the Union Compilation including the weak-lensing effects caused by inhomogeneities. We compute the lensing probability distribution function for each background solution described by the parameters Ω(M), Ω(Λ), and w in the presence of inhomogeneities, approximately modeled with a single-mass population of halos. We then perform a likelihood analysis in the parameter space of Friedmann-Lemaître-Robertson-Walker models and compare our results with the standard approach. We find that the inclusion of lensing can move the best-fit model significantly towards the cosmic concordance of the flat Lambda-Cold Dark Matter model, improving the agreement with the constraints coming from the cosmic microwave background and baryon acoustic oscillations.

Several authors have argued that self-consistent f(R) gravity models distinct from the cold dark matter model with a cosmological constant (LambdaCDM) are almost ruled out. Confronting such claims, we present a particular two-parameter f(R) model that (a) is cosmologically viable and distinguishable from LambdaCDM, (b) is compatible with the existence of relativistic stars, (c) is free of singularities of the Ricci scalar during the cosmological evolution, and (d) allows the addition of high-curvature corrections that could be relevant for inflation.

Refined astrometry measurements allow us to detect large-scale deviations from isotropy through real-time observations of changes in the angular separation between sources at cosmic distances. This "cosmic parallax" effect is a powerful consistency test of the Friedmann-Robertson-Walker metric and may set independent constraints on cosmic anisotropy. We apply this novel general test to Lemaitre-Tolman-Bondi cosmologies with off-center observers and show that future satellite missions such as Gaia might achieve accuracies that would put limits on the off-center distance which are competitive with cosmic microwave background dipole constraints.