Silvia Galli, IAP
Curiosities in Planck
October 4, 2018 (2:25 PM - 2:45 PM)
Dragan Huterer, University of Michigan
Sample variance in local measurements of H0
October 5, 2018 (11:20 AM - 11:40 AM)
We explore whether the H0 tension can be alleviated by the sample variance in the local measurements, which use a small fraction of the Hubble volume. We explicitly take into account the inhomogeneous spatial distribution of type Ia supernovae. Despite the faithful modeling of the observations, our results confirm previous findings that sample variance in local Hubble constant measurements is small and falls short by a factor of ~20 in explaining the difference between the local and CMB H0 measurements. While the H0 tension could in principle be explained by our local neighborhood being a underdense region of radius 150 Mpc, the extreme required underdensity of such a void makes it very unlikely in a LCDM Universe. Therefore, sample variance cannot appreciably alleviate the H0 tension.
Kirit Karkare, KICP
Expansion History Measurements with Line Intensity Mapping
October 5, 2018 (9:55 AM - 10:10 AM)
I will discuss the prospects for constraining the expansion history using line intensity mapping at redshifts above those accessible by galaxy surveys. Using moderate-resolution radio and millimeter spectrometers to measure the large-scale integrated emission from high-redshift galaxies, constraints on the BAO scale from 3 < z < 6 could be obtained with next-generation instruments. Such measurements would provide a valuable link between the local and CMB-derived H0 estimates. Intensity mapping measurements at lower redshifts, overlapping with galaxy surveys, would also provide a valuable cross-check on the local measurements and moreover have completely different systematics.
Lloyd E Knox, UC Davis
Sounds Discordant: Classical Distance Ladder & LCDM Determinations of the Cosmological Sound Horizon
October 5, 2018 (12:10 PM - 12:30 PM)
KEY, 5.12 MB
We compare the constraints on the sound horizon from the combination of Cepheid, Supernova, and BAO data with the LCDM model predictions given various data inputs, mostly CMB ones. We discuss various model adjustments that can decrease the sound horizon, thereby improving concordance, and the challenges to doing so without upsetting the agreement the standard model enjoys with the observed CMB power spectra.
Marco Raveri, KICP
Concordance and Discordance in Cosmology
October 5, 2018 (11:00 AM - 11:20 AM)
Adam Riess, JHU/STScI
The Local Determination of H-naught, Hints of New Physics?
October 4, 2018 (9:20 AM - 9:50 AM)
PDF, 37.99 MB
The steady advance in precision of Hubble constant measurements show the Universe to now be expanding significantly faster (3.5-4 sigma) than expected from the LambdaCDM model calibrated by observations from the early Universe. The higher, local value has been confirmed by 5 independent, geometric calibrations of Cepheids now including by Gaia DR2 parallaxes. Cepheid relative distances have been confirmed by those from TRGB and Miras. At the other end, the low expected value of H_0 predicted from the early Universe is corroborated by independent measurements of the CMB or Omega_B with BAO data. This "H_0 Tension'', as it is widely known, offers the exciting and best opportunity in decades of discovering new fundamental physics such as exotic dark energy, a new relativistic particle, dark matter-radiation interactions or a small curvature, each producing a different sized shift. Pinpointing the cause of the tension requires continued focus on precision and accuracy in the local measurements. I will discuss recent and expected progress in measuring the local value of H-naught by the SHOES Team.
Kimmy Wu, Kavli Institute for Cosmological Physics
Next Steps on H0 from South Pole CMB experiments
October 4, 2018 (4:10 PM - 4:25 PM)