Non-Gaussian and nonscale-invariant perturbations from tachyonic preheating in hybrid inflation

2006/01/31 by Neil Barnaby, James M. Cline · 6 citations
Physics and Astronomy · #Anisotropy #Black Holes and Theoretical Physics #Cosmic microwave background #Cosmology and Gravitation Theories #Curvature #Dimensionless quantity #Galaxies: Formation, Evolution, Phenomena #Gauge theory #Geometry #Inflation (cosmology) #Inflaton #Mathematical physics #Non-Gaussianity #Physics #Quantum electrodynamics #Quantum mechanics #Spectral index #Spectral line #Tachyon #Tachyonic field #Trispectrum #astro-ph #hep-ph #hep-th

paper · pdf · doi:10.1103/physrevd.73.106012

published as Phys.Rev. D73 (2006) 106012 · 31 pages, 15 figures. Typos corrected. References added. Discussion added about the accuracy of the approximate solutions for the tachyon mode functions. Appendix added detailing the calculation of the curvature perturbation and the cancellation of nonlocal terms

arxiv created 2006/05/12 · openalex publication_date 2006/05/31 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05

Abstract

We show that in hybrid inflation it is possible to generate large second-order perturbations in the cosmic microwave background due to the instability of the tachyonic field during preheating. We carefully calculate this effect from the tachyon contribution to the gauge-invariant curvature perturbation, clarifying some confusion in the literature concerning nonlocal terms in the tachyon curvature perturbation; we show explicitly that such terms are absent. We quantitatively compute the non-Gaussianity generated by the tachyon field during the preheating phase and translate the experimental constraints on the nonlinearity parameter f_NL into constraints on the parameters of the model. We also show that nonscale-invariant second-order perturbations from the tachyon field with spectral index n=4 can become larger than the inflaton-generated first-order perturbations, leading to stronger constraints than those coming from non-Gaussianity. The width of the excluded region in terms of the logarithm of the dimensionless coupling g, grows linearly with the log of the ratio of the Planck mass to the tachyon VEV, log(M_p/v); hence very large regions are ruled out if the inflationary scale v is small. We apply these results to string-theoretic brane-antibrane inflation, and find a stringent upper bound on the string coupling, g_s<10^\ensuremath-4.5.

Citations

• Dirac-Born-Infeld action on the tachyon kink and vortex
• Inflation dynamics and reheating
• Scales and hierarchies in warped compactifications and brane worlds
• Non-Gaussian features of primordial fluctuations in single field inflationary models
• Non-Gaussianity from Inflation: Theory and Observations
• Caustics in Tachyon Matter and Other Born-Infeld Scalars
• Field Theory of Tachyon Matter
• Towards inflation in string theory
• Evolution of second-order cosmological perturbations and non-Gaussianity
• Non-Gaussianity in braneworld and tachyon inflation
• Primordial density perturbation in the curvaton scenario
• de Sitter Vacua in String Theory
• Cosmological constraints on string scale and coupling arising from tachyonic instability
• Non-Gaussianity from instant and tachyonic preheating
• Parametric amplification of metric fluctuations during reheating in two field models
• Non-Gaussianity from the second-order cosmological perturbation
• Brane inflation

Cited by

• A geometrical approach to nonlinear perturbations in relativistic cosmology
• Curvature perturbation spectra from waterfall transition, black hole constraints and non-Gaussianity
• Non-Gaussian inflationary perturbations from the dS/CFT correspondence
• Formation of primordial black holes from non-Gaussian perturbations produced in a waterfall transition
• Mass function and bias of dark matter halos for non-Gaussian initial conditions
• Non‐Gaussianity from Particle Production during Inflation