Observational constraints on tachyon and DBI inflation

Abstract

We present a systematic method for evaluation of perturbation observables in non-canonical single-field inflation models within the slow-roll approximation, which allied with field redefinitions enables predictions to be established for a wide range of models. We use this to investigate various non-canonical inflation models, including Tachyon inflation and DBI inflation. The Lambert $W$ function will be used extensively in our method for the evaluation of observables. In the Tachyon case, in the slow-roll approximation the model can be approximated by a canonical field with a redefined potential, which yields predictions in better agreement with observations than the canonical equivalents. For DBI inflation models we consider contributions from both the scalar potential and the warp geometry. In the case of a quartic potential, we find a formula for the observables under both non-relativistic and relativistic behaviour of the scalar DBI inflaton. For a quadratic potential we find two branches in the non-relativistic case, determined by the competition of model parameters, while for the relativistic case we find consistency with results already in the literature. We present a comparison to the latest Planck satellite observations. Most of the non-canonical models we investigate, including the Tachyon, are better fits to data than canonical models with the same potential, but we find that DBI models in the slow-roll regime have difficulty in matching the data.

36 pages, 3 figures. Revisions to title, additional motivation, inclusion of some numerical tests of our results

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• Tachyon inflation in the Large-$N$ formalism
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• DBI Galileon inflation in the light of Planck 2015
• Theoretical and observational constraints on Tachyon Inflation
• Tachyon inflation in the holographic braneworld
• Mimetic DBI Inflation in Confrontation with Planck2018 data
• Tachyon inflation in an AdS braneworld with back-reaction
• Particle creation and reheating in a braneworld inflationary scenario
• Numerical Calculation of Hubble Hierarchy Parameters and Observational Parameters of Inflation
• Quantum Gravity Effects on the Tachyon Inflation from Thermodynamic Perspective
• Viable Intermediate Inflation in the Mimetic DBI Model
• Primordial perturbations and inflation in a holography inspired Gauss-Bonnet cosmology
• Primordial black hole formation in k-inflation models