Physics Colloquium - The Discovery of B-mode Polarization

Event Date: 

Tuesday, April 29, 2014 - 4:00pm

Event Location: 

  • Broida 1640

Event Contact: 


Brian Keating, Center for Astrophysics & Space Sciences, UCSD


The era of Cosmic Microwave Background B-mode polarization cosmology has recently begun 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 range 30 < ell < 150 with >5 sigma significance. 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 any angular scale. The sub-degree scales probed by POLARBEAR are caused by gravitational lensing of the CMB’s E-modes by large scale structure at comparatively low-redshift. The combination of POLARBEAR results at small angular scales with the BICEP2 results at degree angular scales pave the way forward for precision probes of the inflationary model as well as other aspects of fundamental physics, including primordial magnetic fields and measuring the number, and masses, of cosmological neutrinos.