Generating cosmological perturbations in non-singular Horndeski cosmologies

Abstract

We construct a concrete model of Horndeski bounce with strong gravity in the past. Within this model we show that the correct spectra of cosmological perturbations may be generated at early contracting epoch, with mild fine-tuning ensuring that the scalar spectral tilt $n_S$ and tensor-to-scalar ratio $r$ are consistent with observations. The smallness of $r$ is governed by the smallness of the scalar sound speed. Arbitrarily small values of $r$ are forbidden in our setup because of the strong coupling in the past. Nevertheless, we show that it is possible to generate perturbations in a controllable way, i.e. in the regime where the background evolution and perturbations are legitimately described within classical field theory and weakly coupled quantum theory.

51 pages, 14 figures

References in corpus (62)

• k-Inflation
• Generalized G-inflation: Inflation with the most general second-order field equations
• Perturbations in k-inflation
• Healthy theories beyond Horndeski
• Imperfect Dark Energy from Kinetic Gravity Braiding
• Degenerate higher derivative theories beyond Horndeski: evading the Ostrogradski instability
• Horndeski theory and beyond: a review
• Transforming gravity: from derivative couplings to matter to second-order scalar-tensor theories beyond the Horndeski Lagrangian
• G-inflation: inflation driven by the Galileon field
• Towards a Nonsingular Bouncing Cosmology
• Essential Building Blocks of Dark Energy
• Bouncing Cosmologies: Progress and Problems
• Ekpyrotic and Cyclic Cosmology
• A Critical Review of Classical Bouncing Cosmologies
• Galilean Genesis: an alternative to inflation
• G-Bounce
• Kasner and Mixmaster behavior in universes with equation of state w \ge 1
• The Null Energy Condition and its violation
• Bouncing Galileon Cosmologies
• Inflationary non-Gaussianities in the most general second-order scalar-tensor theories
• Primordial fluctuations and non-Gaussianities in multi-field DBI inflation
• Generic instabilities of non-singular cosmologies in Horndeski theory: a no-go theorem
• A Cosmological Super-Bounce
• Classically stable non-singular cosmological bounces
• Generalized Galileons: instabilities of bouncing and Genesis cosmologies and modified Genesis
• Inflation and primordial non-Gaussianities of "generalized Galileons"
• Enhancing the tensor-to-scalar ratio in simple inflation
• Primordial non-Gaussianities in general modified gravitational models of inflation
• Bouncing Cosmology made simple
• Towards Anisotropy-Free and Non-Singular Bounce Cosmology with Scale-invariant Perturbations
• Cosmological Perturbations Through a Non-Singular Ghost-Condensate/Galileon Bounce
• A covariant Lagrangian for stable nonsingular bounce
• Subluminal Galilean Genesis
• Primordial non-Gaussianities of gravitational waves in the most general single-field inflation model
• Implication of the Hubble tension for the primordial Universe in light of recent cosmological data
• Cosmological bounce and Genesis beyond Horndeski
• G-Bounce Inflation: Towards Nonsingular Inflation Cosmology with Galileon Field
• DBI Realizations of the Pseudo-Conformal Universe and Galilean Genesis Scenarios
• Cosmic Bounces and Cyclic Universes
• DHOST Bounce
• Non-perturbative methods for a chiral effective field theory of finite density nuclear systems
• Coupled-channel approach in hadron-hadron scattering
• Generalized multi-Galileons, covariantized new terms, and the no-go theorem for non-singular cosmologies
• Galilean Creation of the Inflationary Universe
• A chiral covariant approach to $\rho \rho$ scattering
• Inflation from Minkowski Space
• From Satisfying to Violating the Null Energy Condition
• Scalar and Tensor Perturbations in DHOST Bounce Cosmology
• Cosmological bounces and Lorentzian wormholes in Galileon theories with an extra scalar field
• Galileon bounce after ekpyrotic contraction
• Generalized Galilean Genesis
• Nonsingular cosmological models with strong gravity in the past
• Genesis with general relativity asymptotics in beyond Horndeski theory
• Non-Gaussian inflationary shapes in $G^3$ theories beyond Horndeski
• Toward evading the strong coupling problem in Horndeski genesis
• Bounce in GR and higher-order derivative operators
• Horndeski genesis: consistency of classical theory
• Note on Reheating in G-inflation
• Bounce from Inflation
• Superluminality in DHOST theory with extra scalar
• Stability of a viable non-minimal bounce
• Bouncing Cosmologies

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• Cuscuton Bounce Beyond the Linear Regime: Bispectrum and Strong Coupling Constraints
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• The primordial non-Gaussianities for non-singular Horndeski cosmologies
• Smoking-gun signatures of bounce cosmology from echoes of relic gravitational waves
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