University of Minnesota
School of Physics & Astronomy

Cosmology Lunchtime Seminar

Monday, April 2nd 2018
12:15 pm:
Speaker: Matt Gomer, UMN
Subject:  Lensing degeneracies and their effect on H_0 measurements

At present, there is a 3σ discrepancy between the local measurements of H0 and those derived from CMB observations. To explore whether or not this is significant, the current goal is to constrain H0 to within 1%, optimally using methods independent from these two. One potential method is to use the time delays between multiple images of gravitationally lensed system as an absolute measure of distance independent of either the distance ladder or CMB modelling. In order to accomplish this at the 1% level, it is critical that the lens system is modelled to similar precision. Unfortunately, there exist lensing degeneracies such as the mass sheet degeneracy which can result in the same set of observables using different mass distributions. Unless these degeneracies can be broken, measurements of H0 will be biased by an unknown amount. In this talk, I detail current efforts to quantify these biases and explore what the future holds for this method.

Faculty Host: Liliya L.R. Williams

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