On the evolution of tachyonic perturbations at super-Hubble scales

Abstract

In the slow-roll inflationary scenario, the amplitude of the curvature perturbations approaches a constant value soon after the modes leave the Hubble radius. However, relatively recently, it was shown that the amplitude of the curvature perturbations induced by the canonical scalar field can grow at super-Hubble scales if there is either a transition to fast roll inflation or if inflation is interrupted for some period of time. In this work, we extend the earlier analysis to the case of a non-canonical scalar field described by the Dirac-Born-Infeld action. With the help of a specific example, we show that the amplitude of the tachyonic perturbations can be enhanced or suppressed at super-Hubble scales if there is a transition from slow roll to fast roll inflation. We also illustrate as to how the growth of the entropy perturbations during the fast roll regime proves to be responsible for the change in the amplitude of the curvature perturbations at super-Hubble scales. Furthermore, following the earlier analysis for the canonical scalar field, we show that the power spectrum evaluated in the long wavelength approximation matches the exact power spectrum obtained numerically very well. Finally, we briefly comment on an application of this phenomenon.

v1: 15 pages, 4 figures; v2: 16 pages, 5 figures, power spectrum included, discussion in section 5 enlarged, references added; v3: 17 pages, 5 figures, enhancement AS WELL AS suppression of modes at super-Hubble scales pointed out, title changed, discussions enlarged, references added, to appear in JCAP

References in corpus (5)

• Inflation and WMAP three year data: Features have a Future!
• New Constraints on Oscillations in the Primordial Spectrum of Inflationary Perturbations
• Non-Gaussianity from Instant and Tachyonic Preheating
• Features in the Primordial Spectrum from WMAP: A Wavelet Analysis
• Cosmological constraints on string scale and coupling arising from tachyonic instability

Cited by in corpus (20)

• Perturbations in generalized multi-field inflation
• PBHs and secondary GWs from ultra slow roll and punctuated inflation
• Single-field inflation, anomalous enhancement of superhorizon fluctuations, and non-Gaussianity in primordial black hole formation
• On Features and Nongaussianity from Inflationary Particle Production
• An analytic approach to non-slow-roll inflation
• On the scalar consistency relation away from slow roll
• Small scale induced gravitational waves from primordial black holes, a stringent lower mass bound, and the imprints of an early matter to radiation transition
• Generating primordial features at large scales in two field models of inflation
• Observational imprints of enhanced scalar power on small scales in ultra slow roll inflation and associated non-Gaussianities
• Large curvature perturbations near horizon crossing in single-field inflation models
• A note on perfect scalar fields
• Non-Gaussianity of superhorizon curvature perturbations beyond $\delta$ N formalism
• Examining the consistency relations describing the three-point functions involving tensors
• Changes in the halo formation rates due to features in the primordial spectrum
• Tracking the Multifield Dynamics with Cosmological Data: A Monte Carlo approach
• Constraints on the generalized tachyon field models from latest observational data
• Nonlinear superhorizon perturbations of non-canonical scalar field
• Perturbed dark energy: classical scalar field versus tachyon
• Understanding large scale CMB anomalies with the generalized non-minimal derivative coupling during inflation
• Suppression of scalar power on large scales and associated bispectra