Special Physics Seminar

Fundamental Physics with Cosmic Microwave Background Polarimetry

Kam Arnold

University of California, San Diego

The polarization of the cosmic microwave background (CMB) offers a unique window onto cosmology that can provide information about neutrinos, dark matter, dark energy, large-scale structure formation, and physics at 10¹⁶ GeV energy scales. Several important measurements of CMB polarization were reported last year, including the first-season results from POLARBEAR. With those measurements, we showed the gravitational lensing of the CMB by large-scale structure using CMB polarization data alone, and a measurement of a non-zero B-mode polarization angular power spectrum.

Going forward, our expansion of POLARBEAR - the Simons Array - will produce more precise observations in multiple spectral bands over a large fraction of the sky. The Simons Array, powerful as a standalone experiment, is also a technological pathfinder for both the CMB-S4 experiment described in the Particle Physics Project Prioritization Panel report, and for the LiteBIRD satellite, which we recently proposed to NASA as a partner mission with JAXA. Together, the Simons Array and LiteBIRD will measure the sum of the neutrino masses with the precision necessary to determine their mass hierarchy, and make a deep search for the inflationary B-mode signal, producing a detection with significance > 10 sigma of the B-modes predicted by all large-field inflation models.