Inflationary predictions in scalar-tensor DBI inflation

Abstract

The scalar-tensor Dirac-Born-Infeld (DBI) inflation scenario provides a simple mechanism to reduce the large values of the boost factor associated with single field models with DBI action, whilst still being able to drive 60 efolds of inflation. Using a slow-roll approach, we obtain an analytical expression for the spectral index of the perturbations and, moreover, determine numerically the regions of the parameter space of the model capable of giving rise to a power spectrum with amplitude and spectral index within the observed bounds. We find that regions that exhibit significant DBI effects throughout the inflationary period can be discarded by virtue of a blue-tilted spectral index, however, there are a number of viable cases --- associated with a more red-tilted spectral index --- for which the boost factor is initially suppressed by the effect of the coupling between the fields, but increases later to moderate values.

Analytical discussion clarified, matches published version. (23 pages incl. appendices, 9 figures)

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Cited by in corpus (13)

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• Tsallis holographic dark energy for inflation
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• Observational constraints on DBI constant-roll inflation
• DBI Galileon inflation in the light of Planck 2015
• Holographic warm inflation
• Inflation with exotic kinetic terms in Einstein-Chern-Simons gravity
• Tsallis holographic inflation in $f(R,T)$ gravity: CMB constraints, reheating, and swampland implications
• The Non-Adiabatic Pressure Perturbation and Non-Canonical Kinetic Terms in Multifield Inflation
• Spinflation with backreaction
• Non-trivial Extension of Starobinsky Inflation
• Constraining parameters of effective field theory of inflation from Planck data
• Bouncing cosmologies in the presence of a Dirac-Born-Infeld field