Observable Spectra of Induced Gravitational Waves from Inflation

Abstract

Measuring the primordial power spectrum on small scales is a powerful tool in inflation model building, yet constraints from Cosmic Microwave Background measurements alone are insufficient to place bounds stringent enough to be appreciably effective. For the very small scale spectrum, those which subtend angles of less than 0.3 degrees on the sky, an upper bound can be extracted from the astrophysical constraints on the possible production of primordial black holes in the early universe. A recently discovered observational by-product of an enhanced power spectrum on small scales, induced gravitational waves, have been shown to be within the range of proposed space based gravitational wave detectors; such as NASA's LISA and BBO detectors, and the Japanese DECIGO detector. In this paper we explore the impact such a detection would have on models of inflation known to lead to an enhanced power spectrum on small scales, namely the Hilltop-type and running mass models. We find that the Hilltop-type model can produce observable induced gravitational waves within the range of BBO and DECIGO for integral and fractional powers of the potential within a reasonable number of e-folds. We also find that the running mass model can produce a spectrum within the range of these detectors, but require that inflation terminates after an unreasonably small number of e-folds. Finally, we argue that if the thermal history of the Universe were to accomodate such a small number of e-folds the Running Mass Model can produce Primordial Black Holes within a mass range compatible with Dark Matter, i.e. within a mass range 10^{20}g< M_{BH}<10^{27}g.

32 pages, 12 figures and 4 appendices

References in corpus (21)

• Improved Dark Energy Constraints from ~100 New CfA Supernova Type Ia Light Curves
• Gravitational Wave Spectrum Induced by Primordial Scalar Perturbations
• The cosmological gravitational wave background from primordial density perturbations
• Upper bounds on the low-frequency stochastic gravitational wave background from pulsar timing observations: current limits and future prospects
• Relating gravitational wave constraints from primordial nucleosynthesis, pulsar timing, laser interferometers, and the CMB: implications for the early universe
• Generalised constraints on the curvature perturbation from primordial black holes
• Probing reheating temperature of the universe with gravitational wave background
• Second-order Gauge Invariant Cosmological Perturbation Theory: -- Einstein equations in terms of gauge invariant variables --
• Primordial seeds of supermassive black holes
• Constraints on the induced gravitational wave background from primordial black holes
• Minimally Parametric Power Spectrum Reconstruction from the Lyman-alpha Forest
• Unified treatment of cosmological perturbations from super-horizon to small scales
• Prospects for direct detection of primordial gravitational waves
• More hilltop inflation models
• Black hole formation and slow-roll inflation
• Space laser interferometers can determine the thermal history of the early Universe
• Imprints of Relic Gravitational Waves in Cosmic Microwave Background Radiation
• Gamma-rays from ultracompact minihalos: potential constraints on the primordial curvature perturbation
• Generating Primordial Black Holes Via Hilltop-Type Inflation Models
• Hilltop Supernatural Inflation and Gravitino Problem
• Constraints on small-scale cosmological perturbations from gamma-ray searches for dark matter