Gauged M-flation after BICEP2

In view of the recent BICEP2 results [arXiv: 1403.3985] which may be attributed to the observation of B-modes polarization of the CMB with tensor-to-scalar ratio r = 0.2(-0.05)(+0.07), we revisit M-flation model. Gauged M-flation is a string theory motivated inflation model with Matrix valued scalar inflaton fields in the adjoint representation of a U(N) Yang-Mills theory. In continuation of our previous works, we show that for a class of M-flation models the action for these inflaton fields can be such that the effective inflaton field phi has a double-well Higgs-like potential, with minima at phi = 0, mu. We focus on the phi > mu, symmetry-breaking region. We thoroughly examine predictions of the model for r in the 2 sigma region allowed for n(S) by the Planck experiment. As computed in [arXiv: 0903.1481], for N-e = 60 and n(S) = 0.96 we find r similar or equal to 0.2, which sits in the sweet spot of BICEP2 region for r. We find that with increasing mu arbitrarily, n(S) cannot go beyond similar or equal to 0.9670, the scalar spectral index for the quadratic chaotic potential. As n(S) varies in the 2 sigma range which is allowed by Planck and could be reached by the model, r varies in the range [0.13, 0.26]. Future cosmological experiments, like the CMBPOL, that confines n(S) with sigma(n(S)) = 0.0029 can constrain the model further. Also, in this region of potential, for n(S) = 0.9603, we find that the largest isocurvature mode, which is uncorrelated with curvature perturbations, has a power spectrum with the amplitude of order 10(-11) at the end of inflation. We also discuss the range of predictions of r in the hilltop region, phi < mu. (C) 2014 The Authors. Published by Elsevier B.V.