Day 1349

Monday.

1712.02886
Cosmological constraints from galaxy clustering in the presence of massive neutrinos
Zennaro, Bel, Dossett, Carbone, Guzzo

The clustering ratio is defined as the ratio between the correlation function and the variance of the smoothed overdensity field.  In LCDM cosmologies not accounting for massive neutrinos, it has already been proved to be independent from bias and redshift space distortions on a range of linear scales.  It therefore allows for a direct comparison of measurements (from galaxies in z space) to predictions (for matter in real space).  In this paper, first extend the applicability of such properties of the clustering ratio to cosmologies that include massive neutrinos, by performing tests against simulated data.  Then investigate the constraining power of the clustering ratio when cosmological parameters such as the total neutrino mass and the equation of state of dark energy are left free.  Analyze the joint posterior distribution of the parameters that must satisfy, at the same time, the measurements of the galaxy clustering ratio in the SDSS DR12, and the angular power spectrum of temperature and polarization anisotropies of the CMB measured by the Planck satellite.  Find the clustering ratio to be very sensitive to the CDM density parameter, but nut very much so to the total neutrino mass.  Lastly, forecast the constraining per the clustering ratio will achieve with forthcoming surveys, predicting the amplitude of its errors in a Euclid-like galaxy survey.  In this case, find it is expected to improve the constraint at 95% level on the CDM density by 40% and on the total neutrino mass by 14%.


1712.02967
Emerging spatial curvature can resolve the conflict between high-redshift (CMB) and low-redshift (distance ladder) measurements of $H_0$
Bolejko

The measurements of the Hubble constant reveal a tension between high-redshift (CMB) and low-z (distance ladder) constraints.  So far neither observational systematics nor new physics has been successfully implemented to explain this tension away.  This paper present a new solution to the Hubble constant problem.  It uses a relativistic simulation of the large scale structure of the Universe (the Simsilun Simulation) together with the ray-tracing algorithm.  The Simsilun simulation allows for relativistic and nonlinear evolution of cosmic structures, which results with a phenomenon of emerging spatial curvature, where the spatial curvature evolves from spatial flatness of the early universe towards slightly curved present-day universe.  This phenomenon speeds up the expansion rate compared to the spatially flat LCDM model.  The results of the ray-tracing analysis show that the universe which starts with initial conditions consistent with the Planck constraints should have the Hubble constant H_0=72.5±2.1 km/s/Mpc.  If the relativistic corrections are not included then the results of the simulation and ray-tracing point towards H_0=68.1±2.0 km/s/Mpc.  Thus, the inclusion of relativistic effects that lead to emergence of the spatial curvature can explain why the low-z measurements favor higher values compared to high-z constraints and alleviate the tension between the CMB and distance ladder measurements of the Hubble constant.