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Monday, April 2nd 2018

12:15 pm:

At present, there is a 3σ-
discrepancy between the local measurements of *H*_{0}-
and those derived from CMB observations. To explore whether or not this is significant, the current goal is to constrain *H*_{0}-
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 *H*_{0}-
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.

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