Curvature perturbations from ekpyrotic collapse with multiple fields

Kazuya Koyama, Shuntaro Mizuno, David Wands

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A scale-invariant spectrum of isocurvature perturbations is generated during collapse in the ekpyrotic scaling solution in models where multiple fields have steep negative exponential potentials. The scale invariance of the spectrum is realized by a tachyonic instability in the isocurvature field. This instability drives the scaling solution to the late-time attractor that is the old ekpyrotic collapse dominated by a single field. We show that the transition from the scaling solution to the single-field-dominated ekpyrotic collapse automatically converts the initial isocurvature perturbations about the scaling solution to comoving curvature perturbations about the late-time attractor. The final amplitude of the comoving curvature perturbation is determined by the Hubble scale at the transition
Original languageEnglish
Pages (from-to)3919-3931
Number of pages13
JournalClassical and Quantum Gravity
Issue number15
Publication statusPublished - 7 Aug 2007


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