Day 1464

Monday.

1809.02180
Astrophysical validation
Calder, Townsley

Present examples of validating components of an astrophysical simulation code.  Problems of stellar astrophysics are multi-dimensional and involve physics acting on large ranges of length and time scales that are impossible to include in macroscopic models on present computational resources.  Simulating these events thus necessitates the development of sub-grid-scale models and the capacity to post-process simulations with higher-fildelity methods.  Present an overview of the problem of validating astrophysical models and simulations illustrated with two examples.  First, present a study aimed at validating hydrodynamics with high energy density laboratory experiments probing shocks and fluid instabilities.  Second, present an effort at validating code modules for use in both macroscopic simulations of astrophysical events and for post processing Lagrangian tracer particles to calculate detailed abundances from thermonuclear reactions occurring during an event.


1809.02340
Can the $H_0$ tension be resolved in extensions to $\Lambda$CDM cosmology?
Guo, Zhang, Zhang

Investigate whether there is an extension to the base LCDM cosmology that can resolve the tension between the Planck observation of the CMB anisotropies and the local measurement of H0.  Consider various plausible extended models in this work, and use the Planck 2015 observations, combined with BAO data, the JLA type Ia SNe data, and the local measurement of H0 (by Riess+ 2016) to make an analysis.  Find that the holographic DE plus sterile neutrino model can reduce the tension to be at the 1.11 sigma level, but this model is obviously not favored by the current observations.  Among these extended models, the LCDM+N_eff model is the most favored by the current observations, and this model can reduce the tension to be at the 1.89 sigma level.  By a careful test, conclude that none of these extended models can convincingly resolve the H0 tension.