Probing Cosmic Acceleration with Galaxy Clusters
Abstract: The acceleration of the Universe is one of the biggest puzzles in physics: is it due to acosmological constant, dynamical dark energy, or modification of gravity? Galaxy clusters provide a unique opportunity to answer this question. In this talk, I will first discuss how we use cluster abundances to constrain cosmic acceleration, and how the weak gravitational lensing by clusters plays a key role. I will then focus on the covariance matrices for future ground- and space-based missions, including the effects of galaxy intrinsic ellipticities, large-scale structure, and variation in halo density profiles.
The Quest for Ultra-High Energy Neutrinos
Abstract: Ultra-high energy neutrinos (>10 PeV) are unique messengers to the distant high energy universe, as cosmic rays and gamma rays are destroyed en-route to earth from cosmic accelerators. Due to low-cross sections and low-fluxes, detecting UHE neutrinos requires enormous volumes. In this talk, I will review the status and recent upgrades to the Askaryan Radio Array—an experiment at the South Pole seeking to detect neutrinos through the radio-Cherenkov effect. I will then present the optimization of a search for ultra-high energy neutrinos in four-years of data from ARA station 2, which is the largest period of lifetime yet analyzed by the collaboration.