Realizing scale-invariant density perturbations in low-energy effective string theory
- Department of Physics, Kinki University, Higashi-Osaka, Osaka 577-8502 (Japan)
- Department of Physics, Gunma National College of Technology, Gunma 371-8530 (Japan)
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 {phi} 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 {phi} and a kinetic term ({nabla}{phi}){sup 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 ({nabla}{phi}){sup 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.
- OSTI ID:
- 20933273
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 75, Issue 2; Other Information: DOI: 10.1103/PhysRevD.75.023520; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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