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The Twisted Universe: The discovery of B-mode polarization
Brian Keating (UCSD)

Dark Universe Science Center Seminar

Date: Wednesday, May 13, 2015 3:00 PM
Location: PAT C-520

The era of Cosmic Microwave Background B-mode polarization cosmology began in March 2014 with two landmark papers released within a week of each other. The BICEP2 telescope observed from the South Pole for three seasons (2010–2012) and released results showing an excess of B-modes in the degree angular scale range with >5 sigma significance. We find that this excess could not be explained by instrumental systematics and it was confirmed in cross-correlation with BICEP1 (at 100 and 150 GHz) and preliminary data from the Keck Array. The observed B-mode power spectrum was well-fit by a lensed-LCDM cosmological model with the addition of primordial tensor fluctuations. However, it is impossible to rule out foreground contamination. I will discuss recent developments in the ongoing joint analysis with Planck.
One week before the BICEP2 announcement, the POLARBEAR telescope (which observed from the Atacama Desert, Chile for one season 2012-2013) announced the first evidence for B-modes at sub-degree scales caused by gravitational lensing of the CMB’s E-modes by large scale structure at low-redshift. The combination of the BICEP2 and POLARBEAR results paves the way towards precision tests of inflation, foreground contamination as well as other aspects of fundamental physics, including cosmological neutrino masses and constraints on exotic physics such as cosmic birefringence.