Abstract:

Polarization of the cosmic microwave background radiation is a powerful probe of the early universe. In particular, the so called B-mode polarization, a swirly spatial pattern in linear polarization, is a unique probe of primordial gravitational waves generated during inflation. After an overview of these concepts, I will give an update on the recent results from the BICEP/Keck experiments. These measurements made at the South Pole clearly detect a very significant B-mode signal at the relevant angular scales. Subsequent Planck high-frequency data, however, suggest that astronomical dust foregrounds could also produce a signal at this level. Regardless of existing uncertainties, I will argue that we are right at an important threshold of this exciting field. The recently deployed BICEP3 experiment will provide ground breaking sensitivity at a frequency that is much less affected by dust emission, using technologies and methodologies already vindicated by BICEP2 and Keck.