Day 1411

Tuesday.

1805.04716
Are $H_0$ and $\sigma_8$ tensions generic to present cosmological data?
Bhattacharyya, et al

Yes, for a wide range of cosmological models (LCDM, non-interacting w_zCDM or models with possible interactions between DE and DM, in either phantom or non-phantom regimes).  In the recent past there have been many attempts to solve the tension between direct measurements of H_0 and sigma_8 sqrt(Omega_0m} from the respective low z observables and indirect measurements of these quantities from the CMB.  In this work, reconstruct a model independent approach that boils down to different classes of cosmological models under suitable parameters choices.  Test this parameterization against the latest Planck CMB data combined with recent BAO, SNeIa datasets and the R16 direct H_0 measurements, and compare among different cosmological models.  The analysis reveals that a strong positive correlation between H_0 and sigma_8 is more or less generic, irrespective of the choice of cosmological models.  Also find that present data slightly prefers a phantom equation of state for DE and a slight negative value for effective equation of state for DM (which is a direct signature of interaction models) with a relatively high value for H_0 consistent with R16 and simultaneously, a consistent value for Omega_0m.  Thus, even though the tensions cannot be fully resolved, interaction models with phantom equation of state get a slight edge over the others for currently available data.  Also see that allowing interaction between DE and DM may resolve the tension between the high z CMB data and individual low z datasets, but the low z datasets have inconsistencies between them (e.g. between BAO and H_0, SNeIa and BAO, and cluster counts and H_0) that are practically independent of the cosmological model.


1805.05037
Chemical characterization of the inner galactic bulge:North-South symmetry
Nandakumar, et al

...With the caveat of a relatively small sample, do not find significant differences in the chemical abundance between the Norther and the Southern fields, hence the evidence is consistent with symmetry in chemistry between North and South.


1805.05146
Breaking degeneracies in modified gravity with higher (than 2nd) order weak-lensing statistics
Peel, Pettorino, Giocoli, Starck, Baldi

GR has been well tested up to solar system scales, but it is much less certain that standard gravity remains an accurate description on the largest, i.e. cosmological, scales.  Many extensions to GR have been studied that are not yet ruled out by the data, including by that of the recent direct gravitational wave detections.  Degeneracies among the standard model (LCDM) and modified gravity (MG) models, as well as among different MG parameters, need to be addressed in order to best exploit information from current and future surveys and to unveil the nature of DE.  Propose various higher-order statistics in the WL signal as a new set of observables able to break degeneracies between massive neutrinos and MG parameters.  Test the methodology on so-called f(R) models, which constitute a class of viable models that can explain the accelerated universal expansion by a modification of the fundamental gravitational interaction.  Explore a range of these models that still fit current observations at the background and linear level, and show using numerical simulations that certain models which include massive neutrinos are able to mimic LCDM in terms of the 3d PS of matter density fluctuations.  Find that depending on the redshift and angular scale of observations, non-Gaussian information accessed by higher-order WL statistics can be used to break the degeneracy between f(R) models and LCDM.  In particular, peak counts computed in aperture mass maps outperform third- and fourth-order moments.