Natural braneworld inflation in light of recent results from Planck and BICEP2

Ishwaree P. Neupane
Phys. Rev. D 90, 123502 – Published 2 December 2014

Abstract

In this paper we report on a major theoretical observation in cosmology. We present a concrete cosmological model for which inflation has a natural beginning and natural ending. Inflation is driven by a cosine-form potential, V(ϕ)=Λ4(1cos(ϕ/f)), which begins at ϕπf and ends at ϕ=ϕend5f/3. The distance traversed by the inflaton field ϕ is sub-Planckian. The Gauss-Bonnet term R2 arising as leading curvature corrections in the action S=d5xg5M3(6λM2+R+αM2R2)+d4xg4(ϕ˙2/2V(ϕ)σ+Lmatter) (where α and λ are constants and M is the five-dimensional Planck mass) plays a key role to terminate inflation. The model generates appropriate tensor-to-scalar ratio r and inflationary perturbations that are consistent with Planck and BICEP2 data. For example, for N*=5060 and ns0.960±0.005, the model predicts that M5.64×1016GeV and r(0.140.21) [N* is the number of e-folds of inflation and ns (nt) is the scalar (tensor) spectrum spectral index]. The ratio nt/r is (13%–24%) less than its value in 4D Einstein gravity, nt/r=1/8. The upper bound on the energy scale of inflation V1/4=2.37×1016GeV (r<0.27) implies that (λα)75×105 and Λ<2.17×1016GeV, which thereby rule out the case α=0 (Randall-Sundrum model). The true nature of gravity is holographic as implied by the braneworld realization of string and M theory. The model correctly predicts a late-epoch cosmic acceleration with the dark energy equation of state wDE1.

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  • Received 30 September 2014

DOI:https://doi.org/10.1103/PhysRevD.90.123502

© 2014 American Physical Society

Authors & Affiliations

Ishwaree P. Neupane1,2,3,*

  • 1Theory Division, CERN, CH-1211 Geneva 23, Switzerland
  • 2Department of Physics and Astronomy, University of Canterbury, Private Bag 4800, Christchurch 8041, New Zealand
  • 3Centre for Cosmology and Particle Physics, Tribhuvan University, Kirtipur, Kathmandu 44618, Nepal

  • *ish.neupane@cern.ch

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Vol. 90, Iss. 12 — 15 December 2014

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