Gravitational Waves and the Scale of Inflation

Abstract

We revisit alternative mechanisms of gravitational wave production during inflation and argue that they generically emit a non-negligible amount of scalar fluctuations. We find the scalar power is larger than the tensor power by a factor of order $1/{\epsilon }^2$. For an appreciable tensor contribution the associated scalar emission completely dominates the zero-point fluctuations of inflaton, resulting in a tensor-to-scalar ratio $r\sim {\epsilon }^2$. A more quantitative result can be obtained if one further assumes that gravitational waves are emitted by localized sub-horizon processes, giving $r_{\max }\simeq 0.3{\epsilon }^2$. However, $\epsilon$ is generally time dependent, and this result for $r$ depends on its instantaneous value during the production of the sources, rather than just its average value, somewhat relaxing constraints from the tilt $n_s$. We calculate the scalar 3-point correlation function in the same class of models and show that non-Gaussianity cannot be made arbitrarily small, i.e. $f_{NL}\ge 1$, independently of the value of $r$. Possible exceptions in multi-field scenarios are discussed.

arXiv comment12 pages

References in corpus (26)

• An All-Sky Analysis of Polarization in the Microwave Background
• The Effective Field Theory of Inflation
• Statistics of Cosmic Microwave Background Polarization
• A General Analytic Formula for the Spectral Index of the Density Perturbations produced during Inflation
• Monodromy in the CMB: Gravity Waves and String Inflation
• Gravity Waves and Linear Inflation from Axion Monodromy
• An Effective Field Theory of Gravity for Extended Objects
• Effective Field Theory for Inflation
• Oscillations in the CMB from Axion Monodromy Inflation
• Non-Gaussianities in Single Field Inflation and their Optimal Limits from the WMAP 5-year Data
• Limits on non-Gaussianities from WMAP data
• Large Nongaussianity in Axion Inflation
• Particle production during inflation and gravitational waves detectable by ground-based interferometers
• Parity violation in the Cosmic Microwave Background from a pseudoscalar inflaton
• Suppression of Bremsstrahlung and Pair Production due to Environmental Factors
• The Effective Field Theory of Multifield Inflation
• Inflation Physics from the Cosmic Microwave Background and Large Scale Structure
• Gravity waves and non-Gaussian features from particle production in a sector gravitationally coupled to the inflaton
• Gauge Fields and Inflation: Chiral Gravitational Waves, Fluctuations and the Lyth Bound
• Resilience of the standard predictions for primordial tensor modes
• Trapped Inflation
• Blue Tensor Spectrum from Particle Production during Inflation
• New Sources of Gravitational Waves during Inflation
• (Small) Resonant non-Gaussianities: Signatures of a Discrete Shift Symmetry in the Effective Field Theory of Inflation
• Unwinding Inflation
• Non-Gaussianity after BICEP2

Cited by in corpus (46)

• The Quest for B Modes from Inflationary Gravitational Waves
• Gravitational waves at interferometer scales and primordial black holes in axion inflation
• Scale-dependent gravitational waves from a rolling axion
• Exploring Cosmic Origins with CORE: Inflation
• Productive Interactions: heavy particles and non-Gaussianity
• A model with cosmological Bell inequalities
• Rolling axions during inflation: perturbativity and signatures
• Higgsed Chromo-Natural Inflation
• Questions on calculation of primordial power spectrum with large spikes: the resonance model case
• Signals of a Quantum Universe
• On the validity of the perturbative description of axions during inflation
• Tensor Squeezed Limits and the Higuchi Bound
• Large-Field Inflation and the Cosmological Collider
• Multi-wavelength constraints on the inflationary consistency relation
• Does the detection of primordial gravitational waves exclude low energy inflation?
• Propagating Speed of Primordial Gravitational Waves
• Testing statistics of the CMB B-mode polarization toward unambiguously establishing quantum fluctuation of vacuum
• Implications of Gravitational-wave Production from Dark Photon Resonance to Pulsar-timing Observations and Effective Number of Relativistic Species
• Large Field Inflation from Axion Mixing
• Gravitational Waves in Bouncing Cosmologies from Gauge Field Production
• On Synthetic Gravitational Waves from Multi-field Inflation
• Beating the Lyth bound by parametric resonance during inflation
• Shapes of non-Gaussianity in warm inflation
• Observable Chiral Gravitational Waves from Inflation in String Theory
• Higher N-point function data analysis techniques for heavy particle production and WMAP results
• Gaugid inflation
• Higher-Curvature Corrections and Tensor Modes
• LiteBIRD Science Goals and Forecasts. A Case Study of the Origin of Primordial Gravitational Waves using Large-Scale CMB Polarization
• New constraints on axion-gauge field dynamics during inflation from $Planck$ and BICEP/Keck data sets
• Fisher Forecasts for Primordial non-Gaussianity from Persistent Homology
• Probing the inflationary background of gravitational waves from large to small scales
• Bound on Induced Gravitational Waves during Inflation Era
• Parity Violating Non-Gaussianity from Axion-Gauge Field Dynamics
• The Effective Planck Mass and the Scale of Inflation
• Primordial perturbations from dilaton-induced gauge fields
• Is Trans-Planckian Censorship a Swampland Conjecture?
• The Inflated Chern-Simons Number in Spectator Chromo-Natural Inflation
• Universality of linear perturbations in SU($N$)-natural inflation
• Curvature Perturbations From Stochastic Particle Production During Inflation
• Effective Planck Mass and the Scale of Inflation
• Fate of global symmetries in the Universe: QCD axion, quintessential axion and trans-Planckian inflaton decay-constant
• Synthetic Gravitational Waves from a Rolling Axion Monodromy
• Inflation in string theory confronts data/Les modèles d'inflation en théorie des cordes face aux observations
• Cherenkov in the Sky: Measuring the Sound Speed of Primordial Scalar Fluctuations
• The spectrum of tensor perturbations in warm inflation
• Gravitational Waves from Gauge Quanta Produced during Inflation