Polarization of the Cosmic Microwave Background : Current Status and Future Prospects(New Developments in Cosmic Microwave Background)

Abstract

The cosmic microwave background is polarized, and the pattern formed by polarization directions in the sky can be decomposed into the so-called "E-mode" and "B-mode" patterns. Motion of plasmas falling into gravitational potential wells at the photon decoupling epoch generates E-mode polarization, whereas it cannot generate B-modes. There are two sources of B-mode polarization within the context of the standard cosmological model: one is the gravitational lensing effect converting E-modes to B-modes; and the other is the primordial gravitational waves generated during cosmic inflation. The E-mode polarization has been measured repeatedly over the past years, and we have witnessed a revolutionary growth in the quality and quantity of the B-mode measurements from the summer 2013 to the spring 2014. We review the current status of the polarization measurements and discuss future prospects.