Disformally coupled inflation

Abstract

A disformal coupling between two scalar fields is considered in the context of cosmological inflation. The coupling introduces novel derivative interactions mixing the kinetic terms of the fields but without introducing superluminal or unstable propagation of the two scalar fluctuation modes. Though the typical effect of the disformal coupling is to inhibit one of the fields from inflating the universe, the energy density of the other field can drive viable near Sitter -inflation in the presence of nontrivial disformal dynamics, in particular when one assumes exponential instead of power-law form for the couplings. The linear perturbation equations are written for the two-field system, its canonical degrees of freedom are quantised, their spectra are derived and the inflationary predictions are reported for numerically solved exponential models. A generic prediction is low tensor-to-scalar ratio.

25 pages, 5 figures, updated to match published version, typos corrected

References in corpus (19)

• Primordial perturbations and non-Gaussianities in DBI and general multi-field inflation
• Perturbations in generalized multi-field inflation
• Screening Modifications of Gravity through Disformally Coupled Fields
• Inflation and String Theory
• Disformal couplings and the dark sector of the universe
• Disformal Theories of Gravity: From the Solar System to Cosmology
• Constraining Disformally Coupled Scalar Fields
• Disformal transformation of cosmological perturbations
• Towards Viable Cosmological Models of Disformal Theories of Gravity
• Shaken, not stirred: kinetic mixing in scalar-tensor theories of gravity
• Untangling features in the primordial spectra
• The effect of varying sound velocity on primordial curvature perturbations
• Non-minimally coupled dark matter: effective pressure and structure formation
• The variation of the fine-structure constant from disformal couplings
• Disformal quintessence
• Disformal vectors and anisotropies on a warped brane
• Combined features in the primordial spectra induced by a sudden turn in two-field DBI inflation
• Astrophysical Tests of Modified Gravity
• Studies of inflation and dark energy with coupled scalar fields

Cited by in corpus (22)

• Relativistic stars in scalar-tensor theories with disformal coupling
• Palatini-Higgs inflation with non-minimal derivative coupling
• Invertible disformal transformations with higher derivatives
• Inflation, the Hubble Tension and Early Dark Energy: an alternative overview
• Implications of Palatini gravity for inflation and beyond
• Anisotropic Inflation with Derivative Couplings
• Running of the Running and Entropy Perturbations During Inflation
• Induced Gravitational Waves from Multi-Sound Speed Resonances during Cosmological Inflation
• Tracking the Multifield Dynamics with Cosmological Data: A Monte Carlo approach
• Disformally Coupled Quintessence
• Dark D-Brane Cosmology: from background evolution to cosmological perturbations
• Vacuum Cherenkov radiation and bremsstrahlung from disformal couplings
• Anisotropic Scalar Field Dark Energy with a Disformally Coupled Yang-Mills Field
• Non-Gaussianity in multi-sound-speed disformally coupled inflation
• A first-order approach to conformal gravity
• Stars disformally coupled to a shift-symmetric scalar field
• Disformally self-tuning gravity
• Potential-driven Inflation with Disformal Coupling to Gravity
• Cosmological attractors to general relativity and spontaneous scalarization with disformal coupling
• Preheating in an inflationary model with disformal coupling
• The adiabatic/entropy decomposition in $P({\varphi }^I,X^{IJ})$ theories with multiple sound speeds
• Cosmic evolution in DHOST theories with scaling solutions