Observable Primordial Gravitational Waves from Non-minimally Coupled $R^2$ Palatini Modified Gravity

Abstract

We probe the spectrum of primordial gravitational waves (GWs) produced during the eras of hyperkination, kination, and reheating in a non-minimally coupled, $\mathcal{L}\propto (1+\xi \chi /M_{\text{Pl}}{)}^t(R+\alpha R^2)$, modified gravity using the Palatini formulation. We consider a runaway potential, which gives an era of kinetic domination after the end of inflation. The coupling order $t$ is varied to examine a large class of theories up to ${\chi }^2{R}^2$. For models with $t>0$, reheating is not achieved naturally; hence, we supplement such theories with a reheating mechanism based on the interaction of inflaton and radiation produced at the end of inflation due to cosmological expansion. We demonstrate that the energy density of the GWs is enhanced as a function of the coupling during kination for all considered theories, and a short-lived phase of hyperkination truncates the boost and avoids the over-production of GWs. Hyperkination, and thus the $R^2$ term, should be deemed necessary in all theories with a runaway potential as it prevents the GW enhancement during kination from destabilizing the Big Bang Nucleosynthesis. The spectrum remains flat for the period of hyperkination and reheating. We examine the available parameter space for which the theories remain valid and place bounds on the Hubble parameter ($H$) and radiation energy density (${\Omega }_r^{\text{end}}$) at the end of inflation. We find that as we decrease the order of the coupling, the spectra shift towards a more observable regime of future GW experiments. The observation of the plateau during reheating will constrain the $H$ and ${\Omega }_r^{\text{end}}$ values, while the spectral shape of the boost obtained during kination will confirm the nature of the theory. The bounds from hyperkination lie in the kHz-GHz frequency range.

42 pages, 11 figures

References in corpus (73)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Array Programming with NumPy
• Planck 2015 results. XIII. Cosmological parameters
• f(R) Theories Of Gravity
• Unified cosmic history in modified gravity: from F(R) theory to Lorentz non-invariant models
• Advanced Virgo: a 2nd generation interferometric gravitational wave detector
• f(R) theories
• Advanced LIGO
• Modified Gravity Theories on a Nutshell: Inflation, Bounce and Late-time Evolution
• Planck 2018 results. X. Constraints on inflation
• Reheating after Inflation
• Planck 2018 results. I. Overview and the cosmological legacy of Planck
• Laser Interferometer Space Antenna
• BICEP / Keck XIII: Improved Constraints on Primordial Gravitational Waves using Planck, WMAP, and BICEP/Keck Observations through the 2018 Observing Season
• Beyond LISA: Exploring Future Gravitational Wave Missions
• BICEP2 / Keck Array VI: Improved Constraints On Cosmology and Foregrounds When Adding 95 GHz Data From Keck Array
• Sensitivity curves for searches for gravitational-wave backgrounds
• Avoiding Dark Energy with 1/R Modifications of Gravity
• The International Pulsar Timing Array: First Data Release
• The North American Nanohertz Observatory for Gravitational Waves
• Science with the space-based interferometer LISA. IV: Probing inflation with gravitational waves
• Challenges and Opportunities of Gravitational Wave Searches at MHz to GHz Frequencies
• AEDGE: Atomic Experiment for Dark Matter and Gravity Exploration in Space
• Cosmology with the Laser Interferometer Space Antenna
• AION: An Atom Interferometer Observatory and Network
• The International Pulsar Timing Array: Second data release
• New Sensitivity Curves for Gravitational-Wave Signals from Cosmological Phase Transitions
• Production and detection of relic gravitons in quintessential inflationary models
• Reconstructing the spectral shape of a stochastic gravitational wave background with LISA
• The Parkes Pulsar Timing Array
• Relic Gravity Waves from Braneworld Inflation
• Detectability of inflation-produced gravitational waves
• Relating gravitational wave constraints from primordial nucleosynthesis, pulsar timing, laser interferometers, and the CMB: implications for the early universe
• Inflation and Preheating in NO models
• Higgs-Palatini Inflation and Unitarity
• Planck intermediate results. LI. Features in the cosmic microwave background temperature power spectrum and shifts in cosmological parameters
• Inflation, braneworlds and quintessence
• Turning Around the Sphaleron Bound: Electroweak Baryogenesis in an Alternative Post-inflationary Cosmology
• Reheating After Quintessential Inflation and Gravitational Waves
• Quintessence and Gravitational Waves
• Spikes in the Relic Graviton Background from Quintessential Inflation
• Reheating in $R^2$ Palatini inflationary models
• ASTROD-GW: Overview and Progress
• Kination Dominated Reheating and Cold Dark Matter Abundance
• On the violent preheating in the mixed Higgs-$R^2$ inflationary model
• Quintessential Kination and Cold Dark Matter Abundance
• Dynamically induced Planck scale and inflation in the Palatini formulation
• Spectrum of Primordial Gravitational Waves in Modified Gravities: A Short Overview
• Electromagnetic Antennas for the Resonant Detection of the Stochastic Gravitational Wave Background
• On the Construction of Quintessential Inflation Models
• Starobinsky-like two-field inflation
• Scale-Invariant Quadratic Gravity and Inflation in the Palatini Formalism
• Inflation in Metric-Affine Quadratic Gravity
• Constraints on Cosmic Quintessence and Quintessential Inflation
• Gravitational reheating in quintessential inflation
• The evolution of gravitons in accelerating cosmologies: the case of extended gravity
• Standard Model Meets Gravity: Electroweak Symmetry Breaking and Inflation
• Inconsistency of an inflationary sector coupled only to Einstein gravity
• Towards a model of Quintessential Inflation
• Palatini $R^2$ Quintessential Inflation
• Implications of Palatini gravity for inflation and beyond
• The NANOGrav Program for Gravitational Waves and Fundamental Physics
• Sub-Planckian ${\varphi }^2$ Inflation in the Palatini Formulation of Gravity with an $R^2$ term
• Gravitational wave signals and cosmological consequences of gravitational reheating
• On UV-completion of Palatini-Higgs inflation
• Tree-level unitarity in Higgs inflation in the metric and the Palatini formulation
• Quintessential Kination and Thermal Production of Gravitinos and Axinos
• Does Palatini Higgs Inflation Conserve Unitarity?
• Inflation and Reheating in f(R,h) theory formulated in the Palatini formalism
• Constant-Roll Inflation in modified $f(R,\varphi )$ gravity model using Palatini Formalism
• Observable Gravitational Waves from Hyperkination in Palatini Gravity and Beyond
• Inflation and reheating in quadratic metric-affine gravity with derivative couplings
• Ultraviolet Unitarity Violations in Non-minimally Coupled Scalar-Starobinsky Inflation

Cited by in corpus (5)

• Inflationary attractors and radiative corrections in light of ACT data
• String-inspired Gauss-Bonnet Gravity Inflation and ACT
• Reconstructing ACT-compatible and GW170817-compatible Einstein-Gauss-Bonnet Inflation from the Observational Indices
• Natural inflation in Palatini $F(R)$
• Scalar-Induced Gravitational Waves in Palatini $f(R)$ Gravity