Primordial perturbations from dilaton-induced gauge fields

Abstract

We study the primordial scalar and tensor perturbations in inflation scenario involving a spectator dilaton field. In our setup, the rolling spectator dilaton causes a tachyonic instability of gauge fields, leading to a copious production of gauge fields in the superhorizon regime, which generates additional scalar and tensor perturbations through gravitational interactions. Our prime concern is the possibility to enhance the tensor-to-scalar ratio $r$ relative to the standard result, while satisfying the observational constraints. To this end, we allow the dilaton field to be stabilized before the end of inflation, but after the CMB scales exit the horizon. We show that for the inflaton slow roll parameter $\epsilon \gtrsim 10^{-3}$, the tensor-to-scalar ratio in our setup can be enhanced only by a factor of $\mathcal{O}(1)$ compared to the standard result. On the other hand, for smaller $\epsilon$ corresponding to a lower inflation energy scale, a much bigger enhancement can be achieved, so that our setup can give rise to an observably large $r\gtrsim 10^{-2}$ even when $\epsilon \ll 10^{-3}$. The tensor perturbation sourced by the spectator dilaton can have a strong scale dependence, and is generically red-tilted. We also discuss a specific model to realize our scenario, and identify the parameter region giving an observably large $r$ for relatively low inflation energy scales.

39 pages, 8 figures; minor revision, version published in JCAP

References in corpus (24)

• A Joint Analysis of BICEP2/Keck Array and Planck Data
• Inflationary Universe with Anisotropic Hair
• Large Nongaussianity in Axion Inflation
• Generation of Large-Scale Magnetic Fields in Single-Field Inflation
• Magnetic fields from inflation?
• The Nature of Primordial Fluctuations from Anisotropic Inflation
• Scalar-Scalar, Scalar-Tensor, and Tensor-Tensor Correlators from Anisotropic Inflation
• Curvature and isocurvature perturbations from two-field inflation in a slow-roll expansion
• Probing polarization states of primordial gravitational waves with CMB anisotropies
• Blue Tensor Spectrum from Particle Production during Inflation
• Universal upper limit on inflation energy scale from cosmic magnetic field
• Universal Constraints on Axions from Inflation
• Parity-violating and anisotropic correlations in pseudoscalar inflation
• Gravitational Waves and the Scale of Inflation
• On the non-Gaussian correlation of the primordial curvature perturbation with vector fields
• Gravitational Waves and Scalar Perturbations from Spectator Fields
• Suppressing the impact of a high tensor-to-scalar ratio on the temperature anisotropies
• How Well Can We Really Determine the Scale of Inflation?
• Can a spectator scalar field enhance inflationary tensor mode?
• Detecting Primordial $B$-Modes after Planck
• Scalar-tensor correlations and large-scale power suppression
• Inflationary dynamics of kinetically-coupled gauge fields
• Scalar-Tensor Anti-Cross-Correlation does not Help to Reconcile the Tension between BICEP2 and Planck
• Vector field instability and the primordial tensor spectrum

Cited by in corpus (18)

• Scale-dependent gravitational waves from a rolling axion
• Primordial Gravitational Waves from Axion-Gauge Fields Dynamics
• Rolling axions during inflation: perturbativity and signatures
• Chiral Primordial Gravitational Waves from Dilaton Induced Delayed Chromo-natural Inflation
• Anisotropic Constant-roll Inflation
• Possible detection of nonclassical primordial gravitational waves with Hanbury Brown - Twiss interferometry
• Nonclassical primordial gravitational waves from the initial entangled state
• Anisotropic constant-roll inflation with noncommutative model and swampland conjectures
• Mixed Non-Gaussianity from Axion-Gauge Field Dynamics
• Statistically Anisotropic Tensor Modes from Inflation
• Generation of Primordial Black Holes and Gravitational Waves from Dilaton-Gauge Field Dynamics
• Scalar perturbations from inflation in the presence of gauge fields
• 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
• Stochastic Effects in Anisotropic Inflation
• Gravitational wave trispectrum in the axion-SU(2) model
• On the primordial correlation of gravitons with gauge fields
• Synthetic Gravitational Waves from a Rolling Axion Monodromy