Vacuum fluctuations in axion-dilaton cosmologies

Journal Article · Tue Jul 01 04:00:00 EDT 1997 · Physical Review, D

DOI:https://doi.org/10.1103/PhysRevD.56.874· OSTI ID:527074

Copeland, E J ^[1]; Easther, R ^[2]; Wands, D ^[3]

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1. Centre for Theoretical Physics, University of Sussex, Brighton, BN1 9QH (United Kingdom)
2. Newman Laboratory of Nuclear Studies, Cornell University, Ithaca, New York 14853 (United States)
3. School of Mathematical Studies, University of Portsmouth, Portsmouth, PO1 2EG (United Kingdom)

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{lt}n{le}4) which allows scale-invariant (n=1) spectra. We note that for n{le}1 the metric is nonsingular in the conformal frame in which the axion is minimally coupled. {copyright} {ital 1997} {ital The American Physical Society}

• OSTI ID: 527074
• Journal Information: Physical Review, D, Journal Name: Physical Review, D Journal Issue: 2 Vol. 56; ISSN PRVDAQ; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
AXIONS
CONFORMAL INVARIANCE
COSMOLOGY
DUALITY
FLUCTUATIONS
PERTURBATION THEORY
SCALE INVARIANCE
SEMICLASSICAL APPROXIMATION
SINGULARITY
STRING MODELS
VACUUM STATES