On reaching the adiabatic limit in multi-field inflation

Abstract

We calculate the scalar spectral index $n_s$ and the tensor-to-scalar ratio $r$ in a class of recently proposed two-field no-scale inflationary models in supergravity. We show that, in order to obtain correct predictions, it is crucial to take into account the coupling between the curvature and the isocurvature perturbations induced by the noncanonical form of the kinetic terms. This coupling enhances the curvature perturbation and suppresses the resulting tensor-to-scalar ratio to the per mille level even for values of the slow-roll parameter $\epsilon \sim 0.01$. Beyond these particular models, we emphasise that multifield models of inflation are a priori not predictive, unless one supplies a prescription for the post-inflationary era, or an adiabatic limit is reached before the end of inflation. We examine the conditions that enabled us to actually derive predictions in the models under study, by analysing the various contributions to the effective isocurvature mass in general two-field inflationary models. In particular, we point out a universal geometrical contribution that is important at the end of inflation, and which can be directly extracted from the inflationary Lagrangian, independently of a specific trajectory. Eventually, we point out that spectator fields can lead to oscillatory features in the time-dependent power spectra at the end of inflation. We demonstrate how these features can be model semi-analytically as well as the theoretical uncertainties they can entail.

arXiv comment26 pages. 13 figures. One additional author. Substantially reworked and extended

References in corpus (59)

• BICEP2 I: Detection Of B-mode Polarization at Degree Angular Scales
• Generating the curvature perturbation without an inflaton
• Planck 2013 results. XXII. Constraints on inflation
• A Joint Analysis of BICEP2/Keck Array and Planck Data
• A General Analytic Formula for the Spectral Index of the Density Perturbations produced during Inflation
• A new approach to the evolution of cosmological perturbations on large scales
• Adiabatic and entropy perturbations from inflation
• Quasi-Single Field Inflation and Non-Gaussianities
• A new mechanism for generating density perturbations from inflation
• Nonperturbative Dynamics Of Reheating After Inflation: A Review
• Super-Horizon Scale Dynamics of Multi-Scalar Inflation
• Features of heavy physics in the CMB power spectrum
• Instant Preheating
• First CMB Constraints on the Inflationary Reheating Temperature
• Large non-Gaussianities with Intermediate Shapes from Quasi-Single Field Inflation
• Non-Gaussianities in two-field inflation
• Metric perturbations in two-field inflation
• Scalar perturbations during multiple-field slow-roll inflation
• Inflation after WMAP3: Confronting the Slow-Roll and Exact Power Spectra with CMB Data
• Primordial perturbations and non-Gaussianities in DBI and general multi-field inflation
• An Observational Test of Two-field Inflation
• Correlated adiabatic and isocurvature perturbations from double inflation
• Perturbations in generalized multi-field inflation
• The Gelaton Scenario: Equilateral non-Gaussianity from multi-field dynamics
• The Separate Universe Approach and the Evolution of Nonlinear Superhorizon Cosmological Perturbations
• Curvature and isocurvature perturbations in two-field inflation
• Observing the Inflationary Reheating
• Isocurvature Perturbations in Multiple Inflationary Models
• Inflation and the Scale Dependent Spectral Index: Prospects and Strategies
• A joint analysis of Planck and BICEP2 B modes including dust polarization uncertainty
• Large non-Gaussianity in multiple-field inflation
• Multi-brid inflation and non-Gaussianity
• Bayesian Analysis of Inflation II: Model Selection and Constraints on Reheating
• Strongly Coupled Perturbations in Two-Field Inflationary Models
• Evolution of non-linear cosmological perturbations
• Conserved non-linear quantities in cosmology
• Modulated fluctuations from hybrid inflation
• Quantitative bispectra from multifield inflation
• Evolution of fNL to the adiabatic limit
• The Imaginary Starobinsky Model
• Correlation-consistency cartography of the double inflation landscape
• Nonlinear perturbations of cosmological scalar fields
• A Statistical Approach to Multifield Inflation: Many-field Perturbations Beyond Slow Roll
• Curvature perturbation from symmetry breaking the end of inflation
• Results from the Wilkinson Microwave Anisotropy Probe
• Multifield Cosmological Perturbations at Third Order and the Ekpyrotic Trispectrum
• Resurrecting Quadratic Inflation in No-Scale Supergravity in Light of BICEP2
• Inflationary perturbation theory is geometrical optics in phase space
• Two-Field Analysis of No-Scale Supergravity Inflation
• Is Imaginary Starobinsky Model Real?
• Complexified Starobinsky Inflation in Supergravity in the Light of Recent BICEP2 Result
• Calculating Non-adiabatic Pressure Perturbations during Multi-field Inflation
• Non-Gaussianities in Multifield Inflation: Superhorizon Evolution, Adiabaticity, and the Fate of fnl
• The Importance of Slow-roll Corrections During Multi-field Inflation
• Perturbative Reheating After Multiple-Field Inflation: The Impact on Primordial Observables
• The Imaginary Starobinsky Model and Higher Curvature Corrections
• Reheating, Multifield Inflation and the Fate of the Primordial Observables
• Adiabaticity and the Fate of Non-Gaussianities: The Trispectrum and Beyond
• Influence of Reheating on the Trispectrum and its Scale Dependence

Cited by in corpus (34)

• Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution
• Calculations of Inflaton Decays and Reheating: with Applications to No-Scale Inflation Models
• Preheating after Multifield Inflation with Nonminimal Couplings, I: Covariant Formalism and Attractor Behavior
• Black hole formation from a general quadratic action for inflationary primordial fluctuations
• Preheating after multifield inflation with nonminimal couplings, III: Dynamical spacetime results
• Accelerating Cosmology and Phase Structure of F(R) Gravity with Lagrange Multiplier Constraint: Mimetic Approach
• Bootstrapping Multi-Field Inflation: non-Gaussianities from light scalars revisited
• Preheating after multifield inflation with nonminimal couplings, II: Resonance Structure
• Universality of multi-field $\alpha$-attractors
• Revisiting small-scale fluctuations in $\alpha$-attractor models of inflation
• Attractor Behaviour in Multifield Inflation
• Phenomenological Aspects of No-Scale Inflation Models
• A manifestly covariant theory of multifield stochastic inflation in phase space: solving the discretisation ambiguity in stochastic inflation
• Angular inflation in multi-field $\alpha$-attractors
• Nonlinear Dynamics of Preheating after Multifield Inflation with Nonminimal Couplings
• Shift-Symmetric Orbital Inflation: single field or multi-field?
• Time-Scales for Nonlinear Processes in Preheating after Multifield Inflation with Nonminimal Couplings
• The simplest extension of Starobinsky inflation
• Multifield inflation beyond $N_{\mathrm{field}}=2$: non-Gaussianities and single-field effective theory
• Inflation with an extra light scalar field after Planck
• On the initial conditions for inflation with plateau potentials: the $R+R^2$ (super)gravity case
• Multifield Dynamics in Higgs-otic Inflation
• On backreaction effects in geometrical destabilisation of inflation
• Isocurvature Constraints on Scalar Dark Matter Production from the Inflaton
• Quantum Cosmological Perturbations of Multiple Fluids
• On Supersymmetric Geometric Flows and ${\mathcal{R}}^2$ Inflation From Scale Invariant Supergravity
• Probing the BSM physics with CMB precision cosmology: an application to supersymmetry
• Observational Constraints on Two-field Warm Inflation
• Multi-chaotic inflation with and without spectator field
• The two-field regime of natural inflation
• Covariant evolution of perturbations during reheating in two-field inflation
• Anatomy of geometrical destabilization of inflation
• Ultra slow-turn inflation
• Separate universe in multifield inflation: a phase-space approach