(no subject)

[leblon]

Attending a workshop on the recent results of the BICEP2 experiment about the B-modes in the polarization of the Cosmic Microwave Background. These were interpreted as evidence from primordial gravitational waves whose properties are consistent with inflating cosmology. However, recently there appeared rumors that the results may be affected by the "foreground subtraction", and perhaps the whole signal will go away. The first talk was by a member of BICEP2. He said that the main problem is with estimating the contribution to polarization from dust. They used models to estimate it, and all models predict a very small contribution, but nobody knows how reliable these models are. Apparently, a competing experiment (PLANCK) has observational data which would allow to estimate the dust foreground, but PLANCK refused to share their data with BICEP2, despite repeated requests. The relevant PLANCK data remain unpublished. Then Mattias Zaldarriaga gave a talk where he tried, among other things, to estimate the size of the dust signal in the patch of the sky studied by BICEP2. He said that the dust foreground estimated in a particular way could explain away the BICEP2 result. But we will know with any certainty only when PLANCK chooses to release their data, which will probably happen in a few months.