Assisted Contraction

Abstract

We consider the dynamics of a contracting universe ruled by two minimally coupled scalar fields with general exponential potentials. This model describes string-inspired scenarios in the Einstein frame. Both background and perturbations can be solved analytically in this model. Curvature perturbations are generated with a scale invariant spectrum only for a dust-like collapse, as happens for a single field model with an exponential potential. We find the conditions for which a scale invariant spectrum for isocurvature perturbation is generated.

13 pages, 3 figures, revised version, conclusions unchanged

References in corpus (9)

• The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang
• On the Generation of a Scale-Invariant Spectrum of Adiabatic Fluctuations in Cosmological Models with a Contracting Phase
• The primordial curvature perturbation in the ekpyrotic Universe
• Pyrotechnic Universe
• On the Spectrum of Fluctuations in an Effective Field Theory of the Ekpyrotic Universe
• Cosmological structure problem of the ekpyrotic scenario
• The failure of cosmological perturbation theory in the new ekpyrotic and cyclic ekpyrotic scenarios
• Density perturbations in the Ekpyrotic Universe and string-inspired generalizations
• Moving Five-Branes in Low-Energy Heterotic M-Theory

Cited by in corpus (85)

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