1997/01/31 by E. J. Copeland, Edmund J. Copeland, Richard Easther +1 · 4 citations
Physics and Astronomy · #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #gr-qc #hep-th
paper · pdf · doi:10.1103/physrevd.56.874
published as Phys.Rev. D56 (1997) 874-888 · LaTeX, 23 pages plus 6 figures, minor typos corrected and references updated. To appear in Phys Rev D
arxiv created 1997/05/27 · openalex publication_date 1997/07/15 · arxiv updated 2009/11/30 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We study axion-dilaton cosmologies derived from the low-energy string effective action. We present the classical homogeneous Friedmann-Robertson-Walker solutions and derive the semiclassical perturbation spectra in the dilaton, axion, and moduli fields in the pre-big-bang scenario. By constructing the unique S-duality-invariant field perturbations for the axion and dilaton fields we derive S-duality-invariant solutions, valid when the axion field is time dependent as well as in a dilaton-vacuum cosmology. Whereas the dilaton and moduli fields have steep blue perturbation spectra (with spectral index n=4) we find that the axion spectrum depends upon the expansion rate of the internal dimensions (0.54<n<~4) which allows scale-invariant (n=1) spectra. We note that for n<~1 the metric is nonsingular in the conformal frame in which the axion is minimally coupled.