Fitting BICEP2 with defects, primordial gravitational waves and dust
  In this work we discuss the possibility of cosmic defects being responsible for the B-mode signal measured by the BICEP2 collaboration. We also allow for the presence of other cosmological sources of B-modes such as inflationary gravitational waves and polarized dust foregrounds, which might contribute to or dominate the signal. On the one hand, we find that defects alone give a poor fit to the data points. On the other, we find that defects help to improve the fit at higher multipoles when they are considered alongside inflationary gravitational waves or polarized dust. Finally, we derive new defect constraints from models combining defects and dust. This proceeding is based on previous works [1,2]. 
Joanes Lizarraga, Jon Urrestilla, David Daverio, Mark Hindmarsh,   Martin Kunz, Andrew R. Liddle
astro-ph.CO hep-ph hep-th