Astrophysics

By creating an ultra-clean underground location with a highly reduced radioactive background, otherwise impossible measurements can be performed to study fundamental physics, astrophysics and cosmology. The Sudbury Neutrino Observatory (SNO) was a 1,000 tonne heavy-water-based neutrino detector created 2 km underground in a mine near Sudbury, Canada. SNO has used neutrinos from 8B decay in the Sun to observe one neutrino reaction sensitive only to solar electron neutrinos and others sensitive to all active neutrino flavors. It found clear evidence for neutrino flavor change that also requires that neutrinos have non-zero mass. This requires modification of the Standard Model for Elementary Particles and confirms solar model calculations with great accuracy. The 2015 Nobel Prize in Physics and the 2016 Breakthrough Prize in Fundamental Physics were awarded for these measurements. Future measurements at the expanded SNOLAB facility will search for Dark Matter particles thought to make up 26% of our Universe and rare forms of radioactivity that can tell us further fundamental properties of neutrinos potentially related to the origin of our matter-dominated Universe.

I will discuss the cosmology of galileon models with a Minkowski limit and discuss whether they can account for the currently observed cosmological model. The full galileon model predicts the speed of gravitational waves to be different from that of photons. I will discuss this and compare with observations. I will then discuss a subdominant galileon model which is compatible. Finally I will discuss the shape dependence of screening in galileon models, showing that the fifth force is unscreened for planar objects.