UNC-CH Physics and Astronomy Colloquium

Martin Bucher, Université Paris 7

“Exploring the Primordial Universe with the Cosmic Microwave Background and Beyond”

Cosmology endeavors to characterize, and furthermore to explain, the origin of the universe from the putative big-bang, its evolution to the present epoch, and its structure on very large scales. Early on, cosmology was primarily speculative and theoretical, but with the present observations of the Cosmic Microwave Background (CMB), a highly constrained characterization of the initial conditions of our universe has emerged. I will explain how observations of the CMB from the European Space Agency’s Planck mission seem to favor simple models of Cosmic Inflation. I will also survey efforts to discover the primordial B mode of the CMB polarization, which could be the tell-tale sign of primordial gravitational waves generated during Cosmic Inflation. As the initial conditions of the Universe are now more or less known, emphasis is shifting toward understanding Cosmic Dawn, when the first stars and quasars came into being, and the nature of the Dark Energy, which unexpectedly is causing the expansion of the Universe to accelerate. I will describe efforts to constrain the Dark Energy using observations of the 21 cm hyperfine transition of hydrogen with the forthcoming 1024-dish HIRAX radio telescope in the Karoo Desert in South Africa.