http://arstechnica.com/science/2014/...gravity-waves/
Gravitational radiation contributes to E-mode as well, but it is the
only source of B-mode polarization.
Only a small fraction of CMB photons are polarized, and of those, most are E-mode in any reasonable prediction. The goal of polarization observations involves measuring the ratio of the two modes, which would allow cosmologists to separate the contributions of gravitational waves from other effects.
That ratio (written as "r") is known prosaically as the "tensor-to-scalar" ratio, where "tensor" refers to the B-mode and "scalar" to the E-mode. A ratio of 0 means no primordial gravitational radiation exists—a result that would potentially rule inflation out."....
http://www.skyandtelescope.com/astro...e-cosmic-dawn/
The icosahedrons 31 great circles have left and right skew versions also.
B-modes spin left or right