Konstantinos Dimopoulos, George Lazarides, Jacques M. Wagstaff
It is shown that, when the inflaton field modulates the gauge kinetic
function of the gauge fields in supergravity realisations of inflation, the
dynamic backreaction leads to a new inflationary attractor solution, in which
the inflaton's variation suffers additional impedance. As a result, slow-roll
inflation can naturally occur along directions of the scalar potential which
would be too steep and curved to support it otherwise. This provides a generic
solution to the infamous eta-problem of inflation in supergravity. Moreover, it
is shown that, in the new inflationary attractor, the spectral index of the
generated curvature perturbations is kept mildly red despite eta of order
unity. The above findings are applied to a model of hybrid inflation is
supergravity with a generic K\"{a}hler potential. The spectral index of the
generated curvature perturbations is found to be 0.97 - 0.98, in excellent
agreement with observations. The gauge field can play the role of the vector
curvaton after inflation but observable statistical anisotropy requires
substantial tuning of the gauge coupling.
View original:
http://arxiv.org/abs/1111.1929
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