Can Self-Ordering Scalar Fields explain the BICEP2 B-mode signal?

Understand

We show that self-ordering scalar fields (SOSF), i.e.

• non-topological cosmic defects arising after a global phase transition, cannot explain the B-mode signal recently announced by BICEP2.
• We compute the full $C_\ell^{B}$ angular power spectrum of B-modes due to the vector and tensor perturbations of SOSF, modeled in the large-N limit of a spontaneous broken global O(N) symmetry.
• We conclude that the low-$\ell$ multipoles detected by BICEP2 cannot be due mainly to SOSF, since they have the wrong spectrum at low multipoles.