Gauged M-flation After BICEP2

A. Ashoorioon; M. M. Sheikh-Jabbari

doi:10.1016/j.physletb.2014.11.018

paper

Gauged M-flation After BICEP2

arXiv:1405.1685 · doi:10.1016/j.physletb.2014.11.018

Abstract

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 in the M-flation model induced from a supersymmetric 10d background probed by a stack of $N$ D3-branes, the "effective inflaton" $ϕ$ has a double-well Higgs-like potential, with minima at $ϕ = 0, μ$ . We focus on the $ϕ > μ$ , symmetry-breaking region. We thoroughly examine predictions of the model for $r$ in the $2 σ$ 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 $r ≃ 0.2$ , which sits in the sweet spot of BICEP2 region for $r$ . We find that with increasing $μ$ arbitrarily, $n_{S}$ cannot go beyond $≃ 0.9670$ . As $n_{S}$ varies in the $2 σ$ range which is allowed by Planck and could be reached by the model, $r$ varies in the range $[0.1322, 0.2623]$ . Future cosmological experiments, like the CMBPOL, that confines $n_{S}$ with $σ (n_{S}) = 0.0029$ 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 $1 0^{- 11}$ at the end of inflation. We also discuss the range of predictions of $r$ in the hilltop region, $ϕ < μ$ .

v1:16 pages, 9 figures; v2: matched the published version

Gauged M-flation After BICEP2

Abstract

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