- #1
thecommexokid
- 70
- 2
I've been trying to understand the whole BICEP story. Here's what I think I understand so far:
- Inflation produces primordial gravitational waves.
- During recombination, photons decouple from matter and the CMB is formed.
- Propagating gravity waves stretch space in one direction and squeeze it in an orthogonal direction.
- The presence of gravity waves during CMB formation would therefore redshift the wavelength of the photons in one direction and blueshift it in an orthogonal direction.
- Thus, gravity waves cause quadrupole anisotropies in the CMB temperature.
- Quadrupole temperature anisotropies lead to differing intensities of photons incident on any given electron from orthogonal directions, which in turn leads to the Thomson-scattered outgoing radiation having a linear polarization.
- This is one of several mechanisms to produce polarization in the CMB, but only this mechanism produces polarization patterns with nonzero curl ("B-mode" polarization).