title: Dynamical selection of the primordial density fluctuation amplitude.
abstract: In inflationary models, the predicted amplitude of primordial density perturbations Q is much larger than the observed value (∼10(-5)) for natural choices of parameters. To explain the requisite exponential fine-tuning, anthropic selection is often invoked, especially in cases where microphysics is expected to produce a complex energy landscape. By contrast, we find examples of ekpyrotic models based on heterotic M theory for which dynamical selection naturally favors the observed value of Q.
authors.affiliation: Perimeter Institute for Theoretical Physics, 31 Caroline Street N, Waterloo, Ontario N2L 2Y5, Canada.
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Lehners
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Steinhardt