Realizing scale-invariant density perturbations in low-energy effective string theory

Zong Kuan Guo*, Nobuyoshi Ohta, Shinji Tsujikawa

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)


We discuss the realization of inflation and resulting cosmological perturbations in the low-energy effective string theory. In order to obtain nearly scale-invariant spectra of density perturbations and a suppressed tensor-to-scalar ratio, it is generally necessary that the dilaton field is effectively decoupled from gravity together with the existence of a slowly varying dilaton potential. We also study the effect of second-order corrections to the tree-level action which are the sum of a Gauss-Bonnet term coupled to and a kinetic term ( )4. We find that it is possible to realize observationally supported spectra of scalar and tensor perturbations provided that the correction is dominated by the ( )4 term even in the absence of the dilaton potential. When the Gauss-Bonnet term is dominant, tensor perturbations exhibit violent negative instabilities on small scales about a de Sitter background in spite of the fact that scale-invariant scalar perturbations can be achieved.

Original languageEnglish
Article number023520
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number2
Publication statusPublished - 2007
Externally publishedYes

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Physics and Astronomy (miscellaneous)


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