scholarly journals Gravitational waves from preheating in Gauss–Bonnet inflation

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
K. El Bourakadi ◽  
M. Ferricha-Alami ◽  
H. Filali ◽  
Z. Sakhi ◽  
M. Bennai
Keyword(s):  
Energy Density ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Coupling Term ◽  
Microwave Background ◽  
Density Spectrum ◽  
Inflation Model ◽  
Good Consistency ◽  
Inflationary Parameters ◽  
Bonnet Term

AbstractWe study gravitational wave production in an expanding Universe during the first stages following inflation, and investigate the consequences of the Gauss–Bonnet term on the inflationary parameters for a power-law inflation model with a GB coupling term. Moreover, we perform the analyses on the preheating parameters involving the number of e-folds $$N_{pre}$$ N pre , and the temperature of thermalization $$T_{th},$$ T th , and show that it’s sensitive to the parameters n, and $$\gamma $$ γ , the parameter $$\gamma $$ γ is proposed to connect the density energy at the end of inflation to the preheating energy density. We set a correlation of gravitational wave energy density spectrum with the spectral index $$n_{s}$$ n s detected by the cosmic microwave background experiments. The density spectrum $$\varOmega _{gw}$$ Ω gw shows good consistency with observation for $$\gamma =$$ γ = $$10^{3}$$ 10 3 and $$10^{6}$$ 10 6 . Our findings suggest that the generation of gravitational waves (GWs) during preheating can satisfy the constraints from Planck’s data.

scholarly journals Measuring the scalar induced gravitational waves from observations

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Jun Li ◽  
Guang-Hai Guo
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Cosmological Parameters ◽  
Numerical Results ◽  
Microwave Background ◽  
High Frequencies ◽  
Special Cases ◽  
Relic Density

AbstractWe consider the scalar induced gravitational waves from the cosmic microwave background (CMB) observations and the gravitational wave observations. In the $$\Lambda $$ Λ CDM+r model, we constrain the cosmological parameters within the evolution of the scalar induced gravitational waves by the additional scalar power spectrum. The two special cases called narrow power spectrum and wide power spectrum have influence on the cosmological parameters, especially the combinations of Planck18+BAO+BK15+LISA. We also compare these numerical results from four datasets within LIGO, LISA, IPTA and FAST projects, respectively. The constraints from FAST have a significant impact on tensor-to-scalar ratio. Besides, we only consider the relic density of induced gravitational waves with respect to different frequencies from CMB scale to high frequencies including the range of LIGO and LISA.

THE POLARIZATION OF THE COSMIC MICROWAVE BACKGROUND DUE TO PRIMORDIAL GRAVITATIONAL WAVES

2006 ◽  
Vol 21 (12) ◽  
pp. 2459-2479 ◽  
Author(s):  
BRIAN G. KEATING ◽  
ALEXANDER G. POLNAREV ◽  
NATHAN J. MILLER ◽  
DEEPAK BASKARAN
Keyword(s):  
Cosmic Microwave Background ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Microwave Background ◽  
Primordial Gravitational Waves ◽  
Cmb Polarization ◽  
Cosmological Inflation ◽  
Gravitational Wave Background ◽  
Review Current ◽  
Rule Out

We review current observational constraints on the polarization of the Cosmic Microwave Background (CMB), with a particular emphasis on detecting the signature of primordial gravitational waves. We present an analytic solution to the Polanarev approximation for CMB polarization produced by primordial gravitational waves. This simplifies the calculation of the curl, or B-mode power spectrum associated with gravitational waves during the epoch of cosmological inflation. We compare our analytic method to existing numerical methods and also make predictions for the sensitivity of upcoming CMB polarization observations to the inflationary gravitational wave background. We show that upcoming experiments should be able either detect the relic gravitational wave background or completely rule out whole classes of inflationary models.

scholarly journals Nonminimal coupling inflation with constant slow roll

2021 ◽  
pp. 2150070
Author(s):  
Mehdi Shokri ◽  
Jafar Sadeghi ◽  
Mohammad Reza Setare ◽  
Salvatore Capozziello
Keyword(s):  
Scalar Field ◽  
Equations Of Motion ◽  
Nonminimal Coupling ◽  
Coupling Term ◽  
Microwave Background ◽  
First Order ◽  
Slow Roll ◽  
Wide Range ◽  
Single Field ◽  
Inflationary Parameters

In this paper, we study a single-field inflationary model modified by a nonminimal coupling term between the Ricci scalar [Formula: see text] and the scalar field [Formula: see text] in the context of constant-roll inflation. The first-order formalism is used to analyze the constant-roll inflation instead of the standard methods used in the literature. In principle, the formalism considers two functions of the scalar field, [Formula: see text] and [Formula: see text], which lead to the reduction of the equations of motion to first-order differential equations. The approach can be applied to a wide range of cosmological situations since it directly relates the function [Formula: see text] with Hubbles parameter [Formula: see text]. We perform the inflationary analysis for power-law and exponential couplings, separately. Then, we investigate the features of constant-roll potentials as inflationary potentials. Finally, we compare the inflationary parameters of the models with the observations of Cosmic Microwave Background (CMB) anisotropies in view of realizing a physically motivated model.

scholarly journals PROPOSED OBSERVATIONS OF GRAVITATIONAL WAVES FROM THE EARLY UNIVERSE VIA "MILLIKAN OIL DROPS"

2007 ◽  
Vol 16 (12a) ◽  
pp. 2309-2318 ◽  
Author(s):  
RAYMOND Y. CHIAO
Keyword(s):  
Cosmic Microwave Background ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Early Universe ◽  
Superfluid Helium ◽  
Magnetic Trap ◽  
Microwave Background ◽  
Planck Mass

Pairs of Planck-mass drops of superfluid helium coated by electrons (i.e. "Millikan oil drops"), when levitated in a superconducting magnetic trap, can be efficient quantum transducers between electromagnetic (EM) and gravitational (GR) radiation. This leads to the possibility of a Hertz-like experiment, in which EM waves are converted at the source into GR waves, and then back-converted at the receiver from GR waves into EM waves. Detection of the gravitational-wave analog of the cosmic microwave background using these drops can discriminate between various theories of the early Universe.

scholarly journals A CMB B-mode Search with Three Years of BICEP Observations

2012 ◽  
Vol 8 (S288) ◽  
pp. 61-67
Author(s):  
Colin Bischoff ◽  
Keyword(s):  
Cosmic Microwave Background ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Final Analysis ◽  
Integration Time ◽  
South Pole ◽  
Microwave Background ◽  
Promising Technique ◽  
Primordial Gravitational Waves ◽  
Gravitational Wave Background

AbstractThe search for B-mode, or curl-type, polarization in the Cosmic Microwave Background is the most promising technique to constrain or detect primordial gravitational waves predicted by the theory of inflation. The Bicep telescope, which observed from the South Pole for three years from 2006 through 2008, is the first experiment specifically designed to target this signal. We review the observational motivations for inflation, the advantages of B-mode observations as a technique for detecting the gravitational wave background, and the design features of Bicep that optimize it for this search. The final analysis of all three seasons of Bicep data is in progress, representing a 50% increase in integration time compared to the result from Chiang et al. (2010). A preview of the three year result includes E-mode and B-mode maps, as well as the projected constraint on r, the tensor-to-scalar ratio.

scholarly journals Non-Gaussian stochastic gravitational waves from phase transitions

2021 ◽  
Vol 2021 (11) ◽  
Author(s):  
Soubhik Kumar ◽  
Raman Sundrum ◽  
Yuhsin Tsai
Keyword(s):  
Phase Transitions ◽  
Cosmic Microwave Background ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Large Scale ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Microwave Background ◽  
Gravitational Wave Detectors ◽  
Non Gaussian

Abstract Cosmological phase transitions in the primordial universe can produce anisotropic stochastic gravitational wave backgrounds (GWB), similar to the cosmic microwave background (CMB). For adiabatic perturbations, the fluctuations in GWB follow those in the CMB, but if primordial fluctuations carry an isocurvature component, this need no longer be true. It is shown that in non-minimal inflationary and reheating settings, primordial isocurvature can survive in GWB and exhibit significant non-Gaussianity (NG) in contrast to the CMB, while obeying current observational bounds. While probing such NG GWB is at best a marginal possibility at LISA, there is much greater scope at future proposed detectors such as DECIGO and BBO. It is even possible that the first observations of inflation-era NG could be made with gravitational wave detectors as opposed to the CMB or Large-Scale Structure surveys.

scholarly journals Modifications to gravitational wave equation from canonical quantum gravity

2020 ◽  
Vol 80 (8) ◽  
Author(s):  
Andrea Dapor ◽  
Klaus Liegener
Keyword(s):  
Wave Equation ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Hamiltonian Operator ◽  
Microwave Background ◽  
Tensor Power ◽  
Modified Dispersion Relation ◽  
Semiclassical States ◽  
Effective Wave ◽  
Canonical Quantum Gravity

Abstract It is expected that the quantum nature of spacetime leaves its imprint in all semiclassical gravitational systems, at least in certain regimes, including gravitational waves. In this paper we investigate such imprints on gravitational waves within a specific framework: space is assumed to be discrete (in the form of a regular cubic lattice), and this discrete geometry is quantised following Dirac’s canonical quantisation scheme. The semiclassical behavior is then extracted by promoting the expectation value of the Hamiltonian operator on a semiclassical state to an effective Hamiltonian. Considering a family of semiclassical states representing small tensor perturbations to Minkowski background, we derive a quantum-corrected effective wave equation. The deviations from the classical gravitational wave equation are found to be encoded in a modified dispersion relation and controlled by the discreteness parameter of the underlying lattice. For finite discretisations, several interesting effects appear: we investigate the thermodynamical properties of these modified gravitons and, under certain assumptions, derive the tensor power spectrum of the cosmic microwave background. The latter is found to deviate from the classical prediction, in that an amplification of UV modes takes place. We discuss under what circumstances such effect can be in agreement with observations.

scholarly journals High frequency background gravitational waves from spontaneous emission of gravitons by hydrogen and helium

2021 ◽  
Vol 81 (5) ◽  
Author(s):  
Jiawei Hu ◽  
Hongwei Yu
Keyword(s):  
Energy Density ◽  
Gravitational Waves ◽  
Spontaneous Emission ◽  
High Frequency ◽  
Energy State ◽  
Direct Consequence ◽  
Density Spectrum ◽  
Spontaneous Transition ◽  
Quantization Of Gravity ◽  
The Universe

AbstractA direct consequence of quantization of gravity would be the existence of gravitons. Therefore, spontaneous transition of an atom from an excited state to a lower-lying energy state accompanied with the emission of a graviton is expected. In this paper, we take the gravitons emitted by hydrogen and helium in the Universe after recombination as a possible source of high frequency background gravitational waves, and calculate the energy density spectrum. Explicit calculations show that the most prominent contribution comes from the $$3d-1s$$ 3 d - 1 s transition of singly ionized helium $$\mathrm {He}^{+}$$ He + , which gives a peak in frequency at $$\sim 10^{13}$$ ∼ 10 13 Hz. Although the corresponding energy density is too small to be detected even with state-of-the-art technology today, we believe that the spontaneous emission of $$\mathrm {He}^{+}$$ He + is a natural source of high frequency gravitational waves, since it is a direct consequence if we accept that the basic quantum principles we are already familiar with apply as well to a quantum theory of gravity.

SUPERQUINTESSENCE

2002 ◽  
Vol 11 (04) ◽  
pp. 471-481 ◽  
Author(s):  
VALERIO FARAONI
Keyword(s):  
Scalar Field ◽  
Energy Density ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Ricci Curvature ◽  
Wave Spectra ◽  
Scalar Field Models ◽  
Acceleration Of The Universe ◽  
The Universe

There is marginal evidence that the quintessential form of matter responsible for the acceleration of the universe observed today has ratio between pressure and energy density w < -1. Such a regime, called superacceleration, cannot be achieved with conventional scalar field models. The simplest nonexotic model achieving superacceleration is that of a scalar field nonminimally coupled to the Ricci curvature. This model is studied for general potentials and an exact superaccelerating solution is presented. In quintessential inflation, the model can have blue gravitational wave spectra, improving the prospects for the detection of cosmological gravitational waves.

DETECTION OF GRAVITATIONAL WAVES FROM INFLATION

2001 ◽  
Vol 16 (supp01a) ◽  
pp. 116-128 ◽  
Author(s):  
MARC KAMIONKOWSKI ◽  
ANDREW H. JAFFE
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Large Scale ◽  
Planck Scale ◽  
New Physics ◽  
Energy Scale ◽  
Grand Unification ◽  
Microwave Background ◽  
The Right ◽  
Gravitational Wave Background

Recent measurements of temperature fluctuations in the cosmic microwave background (CMB) indicate that the Universe is flat and that large-scale structure grew via gravitational infall from primordial adiabatic perturbations. Both od these observations seem to indicate that we are on the right track with inflation. But what is the new physics responsible for inflation? This question can be answered with observations of the polarization of the CMB. Inflation predicts robustly the existence of a stochastic background of cosmological gravitational waves with an amplitude proportional to the square of the energy scale of inflation. This gravitational-wave background induces a unique signature in the polarization of the CMB. If inflation took place at an energy scale much smaller than that of grand unification, then the signal will be too small to be detectable. However, if inflation had something to do with grand unification or Planck-scale physics, then the signal is conceivably detectable in the optimistic case by the Planck satellite, or if not, then by a dedicated post-Planck CMB polarization experiment. Realistic developments in dector technology as well as a proper scan strategy could produce such a post-Planck experiment that would improve on Planck's sensitivity to the gravitational-wave background by several orders of magnitude in a decade timescale.

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