Adiabatic and Isocurvature Perturbations for Multifield Generalized Einstein Models

Abstract

Low energy effective field theories motivated by string theory will likely contain several scalar moduli fields which will be relevant to early Universe cosmology. Some of these fields are expected to couple with non-standard kinetic terms to gravity. In this paper, we study the splitting into adiabatic and isocurvature perturbations for a model with two scalar fields, one of which has a non-standard kinetic term in the Einstein-frame action. Such actions can arise, e.g., in the Pre-Big-Bang and Ekpyrotic scenarios. The presence of a non-standard kinetic term induces a new coupling between adiabatic and isocurvature perturbations which is non-vanishing when the potential for the matter fields is nonzero. This coupling is un-suppressed in the long wavelength limit and thus can lead to an important transfer of power from the entropy to the adiabatic mode on super-Hubble scales. We apply the formalism to the case of a previously found exact solution with an exponential potential and study the resulting mixing of adiabatic and isocurvature fluctuations in this example. We also discuss the possible relevance of the extra coupling in the perturbation equations for the process of generating an adiabatic component of the fluctuations spectrum from isocurvature perturbations without considering a later decay of the isocurvature component.

11 pages, 3 figures, one equation corrected, typos fixed, conclusions unchanged

References in corpus (41)

• Cosmology and the Fate of Dilatation Symmetry
• Coupled Quintessence
• The Ekpyrotic Universe: Colliding Branes and the Origin of the Hot Big Bang
• Generating the curvature perturbation without an inflaton
• Pre-Big-Bang in String Cosmology
• Adiabatic CMB perturbations in pre-big bang string cosmology
• Effects of Cosmological Moduli Fields on Cosmic Microwave Background
• Nongaussian Isocurvature Perturbations from Inflation
• Adiabatic and entropy perturbations from inflation
• Superstring Cosmology
• Assisted inflation
• Dynamics of Anti-de Sitter Domain Walls
• On the Generation of a Scale-Invariant Spectrum of Adiabatic Fluctuations in Cosmological Models with a Contracting Phase
• Density Perturbations in the Ekpyrotic Scenario
• Mirage Cosmology
• Cosmology With Negative Potentials
• On the Construction of Nonsingular Pre-Big-Bang and Ekpyrotic Cosmologies and the Resulting Density Perturbations
• The primordial curvature perturbation in the ekpyrotic Universe
• Pyrotechnic Universe
• Parametric Amplification of Metric Fluctuations During Reheating in Two Field Models
• Cosmology with positive and negative exponential potentials
• Cosmological perturbations from multi-field inflation in generalized Einstein theories
• On the Spectrum of Fluctuations in an Effective Field Theory of the Ekpyrotic Universe
• Metric Perturbations in Dilaton-Driven Inflation
• Vacuum fluctuations in axion-dilaton cosmologies
• Dynamics of Assisted Inflation
• Adiabatic perturbations in pre big bang models: matching conditions and scale invariance
• Constraints from Inflation on Scalar-Tensor Gravity Theories
• Isocurvature perturbations in the Ekpyrotic universe
• Cosmological structure problem of the ekpyrotic scenario
• Assisted Contraction
• Density perturbations in the Ekpyrotic Universe and string-inspired generalizations
• S-duality Invariant Perturbations in String Cosmology
• Preheating and the Einstein Field Equations
• Assisting pre-big bang phenomenology through short-lived axions
• Gravity, Parametric Resonance and Chaotic Inflation
• On The Varying Speed of Light in a Brane-Induced FRW Universe
• Metric perturbations at reheating: the use of spherical symmetry
• Large metric perturbations from rescattering
• Moving Five-Branes in Low-Energy Heterotic M-Theory
• On ekpyrotic brane collisions

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