Phenomenology of Dbrane inflation with general speed of sound
Abstract
A characteristic of Dbrane inflation is that fluctuations in the inflaton field can propagate at a speed significantly less than the speed of light. This yields observable effects that are distinct from those of singlefield slowroll inflation, such as a modification of the inflationary consistency relation and a potentially large level of nonGaussianities. We present a numerical algorithm that extends the inflationary flow formalism to models with general speed of sound. For an ensemble of Dbraneinflation models parametrized by the Hubble parameter and the speed of sound as polynomial functions of the inflaton field, we give qualitative predictions for the key inflationary observables. We discuss various consistency relations for Dbrane inflation, and compare the qualitative shapes of the warp factors we derive from the numerical models with analytical warp factors considered in the literature. Finally, we derive and apply a generalized microphysical bound on the inflaton field variation during brane inflation. While a large number of models are consistent with current cosmological constraints, almost all of these models violate the compactification constraint on the field range in fourdimensional Planck units. If the field range bound is to hold, then models with a detectable level of nonGaussianity predict a blue scalar spectral index, and a tensor component that is far below the detection limit of any future experiment.
 Publication:

Physical Review D
 Pub Date:
 November 2007
 DOI:
 10.1103/PhysRevD.76.103517
 arXiv:
 arXiv:0706.1240
 Bibcode:
 2007PhRvD..76j3517P
 Keywords:

 98.80.Bp;
 11.25.Wx;
 98.80.Cq;
 98.80.Es;
 Origin and formation of the Universe;
 String and brane phenomenology;
 Particletheory and fieldtheory models of the early Universe;
 Observational cosmology;
 Astrophysics;
 High Energy Physics  Theory
 EPrint:
 23 pages, 11 figures, v2: version accepted by PRD