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

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{sub 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{sub 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{sub s}<10{sup -4.5}.

Authors:
;  [1]
  1. Physics Department, McGill University, 3600 University Street, Montreal, Quebec, H3A 2T8. (Canada)
Publication Date:
OSTI Identifier:
20774757
Resource Type:
Journal Article
Journal Name:
Physical Review. D, Particles Fields
Additional Journal Information:
Journal Volume: 73; Journal Issue: 10; Other Information: DOI: 10.1103/PhysRevD.73.106012; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0556-2821
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; COSMIC RADIATION; COSMOLOGY; COUPLING; DISTURBANCES; GAUGE INVARIANCE; INFLATIONARY UNIVERSE; INSTABILITY; MASS; MEMBRANES; NONLINEAR PROBLEMS; QUANTUM FIELD THEORY; RADIOWAVE RADIATION; RELICT RADIATION; STRING MODELS; TACHYONS

Citation Formats

Barnaby, Neil, and Cline, James M. Non-Gaussian and nonscale-invariant perturbations from tachyonic preheating in hybrid inflation. United States: N. p., 2006. Web. doi:10.1103/PhysRevD.73.106012.
Barnaby, Neil, & Cline, James M. Non-Gaussian and nonscale-invariant perturbations from tachyonic preheating in hybrid inflation. United States. https://doi.org/10.1103/PhysRevD.73.106012
Barnaby, Neil, and Cline, James M. 2006. "Non-Gaussian and nonscale-invariant perturbations from tachyonic preheating in hybrid inflation". United States. https://doi.org/10.1103/PhysRevD.73.106012.
@article{osti_20774757,
title = {Non-Gaussian and nonscale-invariant perturbations from tachyonic preheating in hybrid inflation},
author = {Barnaby, Neil and Cline, James M},
abstractNote = {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{sub 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{sub 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{sub s}<10{sup -4.5}.},
doi = {10.1103/PhysRevD.73.106012},
url = {https://www.osti.gov/biblio/20774757}, journal = {Physical Review. D, Particles Fields},
issn = {0556-2821},
number = 10,
volume = 73,
place = {United States},
year = {2006},
month = {5}
}