Kazuya Koyama et al 2007 Class. Quantum Grav. 24 3919 doi:10.1088/0264-9381/24/15/010
Kazuya Koyama1, Shuntaro Mizuno2 and David Wands1
Show affiliationsA 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.
04.20.Dw Singularities and cosmic censorship
04.25.Nx Post-Newtonian approximation; perturbation theory; related approximations
83C05 Einstein's equations (general structure, canonical formalism, Cauchy problems)
Issue 15 (7 August 2007)
Received 23 April 2007, in final form 11 May 2007
Published 17 July 2007
Kazuya Koyama et al 2007 Class. Quantum Grav. 24 3919
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