Tilted ekpyrosis

J. Fonseca, David Wands

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We consider a simple model of cosmological collapse driven by canonical fields with exponential potentials. We generalize the two-field ekpyrotic collapse to consider nonorthogonal or tilted potentials and give the general condition for isocurvature field fluctuations to have a scale-invariant spectrum in this model. In particular we show that tilted potentials allow for a slightly red spectrum of perturbations as required by current observations. However a red spectrum of fluctuations implies that the two-field ekpyrotic phase must have a finite duration and requires a preceding phase which sets the initial conditions for what otherwise appears to be a fine-tuned trajectory in the phase space.
Original languageEnglish
Pages (from-to)101303
Number of pages1
JournalPhysical Review D
Issue number10
Publication statusPublished - Nov 2011


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