Session Q1: Plenary Session II: Treasures From the Cosmic Frontier

Cosmic Neutrinos in the IceCube Detector

High-energy neutrinos are thought to be emitted by astronomical objects such as active galactic nuclei, gamma-ray bursts, and supernova remnants. However, due to their small predicted flux and large backgrounds from neutrinos and muons made in the Earth's atmosphere, they had not been observed until now. The IceCube Neutrino Observatory instruments a cubic kilometer of ice at the South Pole to detect neutrinos mostly above 100 GeV. In a dataset from the first couple of years of the completed detector, a new veto technique was employed to find a pure sample of very high energy neutrinos (above 30 TeV). An excess is observed above atmosphere-created backgrounds that is incompatible in energy spectrum and arrival direction, leading to the first observation of astrophysical neutrinos. Studies on the arrival direction were performed to search for clustering of events that would indicate individual sources, signaling the birth of neutrino astronomy.   

Tales from the Twitterverse

The public's access to science has historically occurred through traditional conduits of communication such as television documentaries, and media reports. But in the past five years social media has arisen as a means of attracting people who would have never imagined they had an interest in the universe, or in science at all. The results are stunning and unexpected, with millions of people responding to various offerings of the universe made in these media. Twitter and Facebook lead the way, but other internet social media have proven potent as well, including YouTube, Reddit, Google+, and more broadly, the blogosphere. We give first-hand stories and accounts of forays on this landscape and offer suggestions on how such efforts may benefit the long-term health of science in America, by cultivating public support at its deepest levels.   

Probing the First Instants and the Rest of the Universe with Polarized Signatures in the Cosmic Microwave Background

The cosmic microwave background (CMB) radiation reports the initial conditions in the universe for the formation of large scale structures (galaxies and their dark matter halos, clusters of galaxies). The rich angular power spectrum of the CMB's intensity traces the primordial power spectrum of density fluctuations, but also encodes details of the CMB's interactions with the rest of the universe in its 13-billion-year flight. The CMB is slightly polarized by Thomson scattering whenever there is any local quadrupolar anisotropy in the distribution of the scattering electron population. Acoustic oscillations in the primordial plasma lead to finite local quadrupoles, but the ensuing polarization from this process exhibits an even parity symmetry. We refer to the angular power spectrum of this even-parity polarization as the E-mode spectrum, and name the odd-parity patterns B-modes. A tantalizing fact is that the gravitational wave background left after inflation also produces local quadrupoles, yet the ensuing CMB polarization is not constrained in its parity. Inflation is the only primordial source of B-modes yet proposed, and CMB B-modes are the only proposed avenue for measurement of the energy scale of inflation! Moreover, the inflationary signature in the B-modes is confined to large angular scales. The vanishing of the primordial B-mode spectrum at fine angular scales sets up excellent initial conditions for tracing the subsequent evolution of large scale structure in the universe, since that structure's mass deflects the CMB photons, re-arranging some of the E-mode patterns into B-modes. I will elaborate on the present state of CMB polarization measurements at both large and small angles in the context of their potential discovery space.