University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Wednesday, September 10th 2014
3:35 pm:
Speaker: Greg Aldering, Lawrence Berkeley Laboratory, University of California
Subject: Some Fault is in our Stars: Bias on the Road to Cosmological Concordance
Refreshments served in Room 216 Physics after colloquium

The discovery of the accelerating expansion of the Universe, driven by a mysterious ``dark energy'', was based on measurements of the relative brightnesses of stellar explosion known as Type Ia supernovae (SNe Ia). SNe Ia remain the leading tool for measuring the dark energy equation of state, w, due to their statistical power, the great distances to which they can be measured, and the complementarity of SNe Ia and cosmic microwave background (CMB) constraints. In this talk I will describe current efforts to hone SNe Ia as cosmological tools. These efforts have found new ways to improve the statistical power of SNe Ia, but have also unearthed previously unrecognized biases due to the behavior of SNe Ia. Correction for one of these biases reduces the Hubble Space Telescope (HST) measurement of the Hubble constant, bringing it significantly closer to the value inferred from Planck and WMAP CMB measurements. It also is likely that current measurements of w are affected by these biases at the level of several percent. I will close with a description of a new large HST program that will significantly increase the number of SNe Ia in the redshift range 1 < z < 2, with the goal of measuring time variation in w such as that suggested by recent Lyman-alpha forest baryon acoustic oscillation measurements.

Faculty Host: Roberta Humphreys

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