TY - JOUR

T1 - Realizing scale-invariant density perturbations in low-energy effective string theory

AU - Guo, Zong Kuan

AU - Ohta, Nobuyoshi

AU - Tsujikawa, Shinji

PY - 2007

Y1 - 2007

N2 - 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.

AB - 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.

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U2 - 10.1103/PhysRevD.75.023520

DO - 10.1103/PhysRevD.75.023520

M3 - Article

AN - SCOPUS:33846416904

VL - 75

JO - Physical Review D - Particles, Fields, Gravitation and Cosmology

JF - Physical Review D - Particles, Fields, Gravitation and Cosmology

SN - 1550-7998

IS - 2

M1 - 023520

ER -