scholarly journals Non-Gaussianity of inflationary gravitational waves from the field equation

2019 ◽  
Vol 28 (02) ◽  
pp. 1950036 ◽  
Author(s):  
Aniket Agrawal
Keyword(s):  
Field Equation ◽  
Green’S Function ◽  
Gravitational Waves ◽  
Green's Function ◽  
Tree Level ◽  
Gauge Fields ◽  
Vacuum Fluctuations ◽  
Scale Invariant ◽  
Left Handed ◽  
Primordial Gravitational Waves

We demonstrate equivalence of the in–in formalism and Green’s function method for calculating the bispectrum of primordial gravitational waves generated by vacuum fluctuations of the metric. The tree-level bispectrum from the field equation, [Formula: see text], agrees with the results obtained previously using the in–in formalism exactly. Characterizing non-Gaussianity of the fluctuations using the ratio [Formula: see text] in the equilateral configuration, where [Formula: see text] is the power spectrum of scale-invariant gravitational waves, we show that it is much weaker than in models with spectator gauge fields. We also calculate the tree-level bispectrum of two right-handed and one left-handed gravitational wave using Green’s function, reproducing the results from in–in formalism, and show that it can be as large as the bispectrum of three right-handed gravitational waves.

scholarly journals A New Inflationary Universe Scenario with Inhomogeneous Quantum Vacuum

2018 ◽  
Vol 2018 ◽  
pp. 1-15
Author(s):  
Yilin Chen ◽  
Jin Wang
Keyword(s):  
Green’S Function ◽  
Potential Barrier ◽  
Green's Function ◽  
Inflationary Universe ◽  
Quantum Vacuum ◽  
Vacuum Fluctuations ◽  
Inflationary Scenario ◽  
Slowing Down ◽  
The Universe ◽  
Inhomogeneous Quantum

We investigate the quantum vacuum and find that the fluctuations can lead to the inhomogeneous quantum vacuum. We find that the vacuum fluctuations can significantly influence the cosmological inhomogeneity, which is different from what was previously expected. By introducing the modified Green’s function, we reach a new inflationary scenario which can explain why the Universe is still expanding without slowing down. We also calculate the tunneling amplitude of the Universe based on the inhomogeneous vacuum. We find that the inhomogeneity can lead to the penetration of the Universe over the potential barrier faster than previously thought.

scholarly journals On the zero-crossing of the three-gluon Green’s function from lattice simulations

2018 ◽  
Vol 175 ◽  
pp. 12012 ◽  
Author(s):  
Andreas Athenodorou ◽  
Philippe Boucaud ◽  
Feliciano de Soto ◽  
José Rodríguez-Quintero ◽  
Savvas Zafeiropoulos
Keyword(s):  
Green’S Function ◽  
Green's Function ◽  
Large Volume ◽  
Form Factors ◽  
Tree Level ◽  
Zero Crossing ◽  
Zero Momentum ◽  
Made In

We report on some efforts recently made in order to gain a better understanding of some IR properties of the 3-point gluon Green’s function by exploiting results from large-volume quenched lattice simulations. These lattice results have been obtained by using both tree-level Symanzik and the standard Wilson action, in the aim of assessing the possible impact of effects presumably resulting from a particular choice for the discretization of the action. The main resulting feature is the existence of a negative log-aritmic divergence at zero-momentum, which pulls the 3-gluon form factors down at low momenta and, consequently, yields a zero-crossing at a given deep IR momentum. The results can be correctly explained by analyzing the relevant Dyson-Schwinger equations and appropriate truncation schemes.

scholarly journals The tilt of primordial gravitational waves spectra from BICEP2

2014 ◽  
Vol 29 (33) ◽  
pp. 1450185 ◽  
Author(s):  
Cheng Cheng ◽  
Qing-Guo Huang
Keyword(s):  
Gravitational Waves ◽  
Scale Invariant ◽  
Significance Level ◽  
High Significance ◽  
Alternative Models ◽  
Inflation Model ◽  
Primordial Gravitational Waves

In this paper we constrain the tilt of the spectrum of primordial gravitational waves from Background Imaging of Cosmic Extragalactic Polarization (BICEP2) data only. We find [Formula: see text] and [Formula: see text] (at 68% C.L.) which implies that a scale-invariant primordial gravitational waves spectra is consistent with BICEP2 nicely. Our results provide evidence for supporting inflation model, and the alternative models, for example the ekpyrotic model which predicts nt = 2, are ruled out at high significance level.

scholarly journals Cosmological correlators, In–In formalism and double copy

2020 ◽  
Vol 35 (11) ◽  
pp. 2050076 ◽  
Author(s):  
A. R. Fazio
Keyword(s):  
Scattering Amplitudes ◽  
Scalar Curvature ◽  
Gravitational Waves ◽  
Gauge Theories ◽  
Three Dimensional ◽  
Tree Level ◽  
Tensor Factor ◽  
Dimensional Minkowski Space ◽  
Primordial Gravitational Waves ◽  
Double Copy

We are investigating if the double copy structure as product of scattering amplitudes of gauge theories applies to cosmological correlators computed, in a class of theories for inflation, by the operatorial version of the In–In formalism of Schwinger–Keldysh. We consider tree-level momentum–space correlators involving primordial gravitational waves with different polarizations and the scalar curvature fluctuations on a three-dimensional fixed spatial slice. The correlators are sum of terms factorized in a time-dependent scalar factor, which takes into account the curved background where energy is not conserved, and in a so-called tensor factor, constructed by polarization tensors. In the latter, we recognize scattering amplitudes in four-dimensional Minkowski space spanned by three points gravitational amplitudes related by double copy to those of gauge theories. Our study indicates that gravitational waves are double copy of gluons and the primordial scalar curvature is double copy of a scalar with Higgs-like interactions.

scholarly journals Primordial gravitational waves from axion-gauge fields dynamics

2017 ◽  
Vol 2017 (01) ◽  
pp. 019-019 ◽  
Author(s):  
Emanuela Dimastrogiovanni ◽  
Matteo Fasiello ◽  
Tomohiro Fujita
Keyword(s):  
Gravitational Waves ◽  
Gauge Fields ◽  
Primordial Gravitational Waves

Particle Physics in the Sky: the Current Status of Inflation

2007 ◽  
Vol 22 (31) ◽  
pp. 5725-5734
Author(s):  
William H. Kinney
Keyword(s):  
Gravitational Waves ◽  
Particle Physics ◽  
Current Data ◽  
Current Status ◽  
Inflationary Cosmology ◽  
Scale Invariant ◽  
Slow Roll ◽  
Primordial Gravitational Waves ◽  
Data Release ◽  
Near Future

I discuss the current status of inflationary cosmology in light of the recent WMAP 3-year data release. The basic predictions of inflation are all supported by the data. Inflation also makes predictions which are have not been well tested by current data but can be by future experiments, most notably a deviation from a scale-invariant power spectrum and the production of primordial gravitational waves. A scale-invariant spectrum is disfavored by current data, but not conclusively. Tensor modes are currently poorly constrained, and slow-roll inflation does not make an unambiguous prediction of the expected amplitude of primordial gravitational waves. A tensor/scalar ratio of r ≃ 0.01 is within reach of near-future measurements.

scholarly journals Gravitational wave trispectrum in the axion-SU(2) model

2022 ◽  
Vol 2022 (01) ◽  
pp. 007
Author(s):  
Tomohiro Fujita ◽  
Kai Murai ◽  
Ippei Obata ◽  
Maresuke Shiraishi
Keyword(s):  
Gauge Theory ◽  
Power Spectrum ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Parameter Space ◽  
Tree Level ◽  
Gauge Fields ◽  
Abelian Gauge ◽  
Abelian Gauge Theory ◽  
Unique Signal

Abstract We study the trispectrum of the gravitational waves (GWs) generated through the dynamics of an axionic spectator field and SU(2) gauge fields during inflation. In non-Abelian gauge theory, the gauge fields have four-point self-interactions, which induce the tree-level GW trispectrum. We formulate this type of the GW trispectrum including the non-dynamical contributions and evaluate it in the equilateral limit as a unique signal of this model. We find that the ratio of the GW trispectrum to the cube of the scalar power spectrum can be as large as 𝒪(106) in the viable parameter space, which could be captured in the CMB observations.

PARTICLE PHYSICS IN THE SKY: THE CURRENT STATUS OF INFLATION

2008 ◽  
Vol 17 (05) ◽  
pp. 904-913 ◽  
Author(s):  
WILLIAM H. KINNEY
Keyword(s):  
Gravitational Waves ◽  
Particle Physics ◽  
Current Data ◽  
Current Status ◽  
Inflationary Cosmology ◽  
Scale Invariant ◽  
Slow Roll ◽  
Primordial Gravitational Waves ◽  
Data Release ◽  
Near Future

I discuss the current status of inflationary cosmology in light of the recent WMAP 3-year data release. The basic predictions of inflation are all supported by the data. Inflation also makes predictions which are have not been well tested by current data but can be by future experiments, most notably a deviation from a scale-invariant power spectrum and the production of primordial gravitational waves. A scale-invariant spectrum is disfavored by current data, but not conclusively. Tensor modes are currently poorly constrained, and slow-roll inflation does not make an unambiguous prediction of the expected amplitude of primordial gravitational waves. A tensor/scalar ratio of r ≃ 0.01 is within reach of near-future measurements.

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