M-flation: Inflation From Matrix Valued Scalar Fields
  We propose an inflationary scenario, M-flation, in which inflation is driven
by three $N\times N$ hermitian matrices $\Phi_i, i=1,2,3$. The inflation
potential of our model, which is strongly motivated from string theory, is
constructed from $\Phi_{i}$ and their commutators. We show that one can
consistently restrict the classical dynamics to a sector in which the $\Phi_i$
are proportional to the $N\times N$ irreducible representations of SU(2). In
this sector our model effectively behaves as an N-flation model with $3 N^2$
number of fields and the effective inflaton field has a super-Planckian field
value. Furthermore, the fine-tunings associated with unnaturally small
couplings in the chaotic type inflationary scenarios are removed. Due to the
matrix nature of the inflaton fields there are $3N^2-1$ extra scalar fields in
the dynamics. These have the observational effects such as production of
iso-curvature perturbations on cosmic microwave background. Moreover, the
existence of these extra scalars provides us with a natural preheating
mechanism and exit from inflation. As the effective inflaton field can traverse
super-Planckian distances in the field space, the model is capable of producing
a considerable amount of gravity waves that can be probed by future CMB
polarization experiments such as PLANCK, QUIET and CMBPOL.
