scholarly journals Gravitational Waves from Inflation

2020 ◽  
Author(s):  
◽  
Maria Mylova
Keyword(s):  
Gravitational Wave ◽  
Gravitational Waves ◽  
Parity Violation ◽  
Background Radiation ◽  
Effective Field ◽  
Energy Scale ◽  
Mode Analysis ◽  
Strongly Coupled ◽  
Short Period ◽  
Microwave Background Radiation

The focus of this work is on the topic of gravitational wave cosmology. We look for new observational signatures for primordial gravitational waves and especially for frameworks that can produce an enhanced tensor spectrum. In such cases, the gravitational wave energy density can enter within the sensitivity curves of gravi-tational wave detectors or it could leave a measurable imprint in the polarization pattern of the Cosmic Microwave Background radiation. This is very important as more sensitive, next generation experiments are expected to make indirect and direct measurements of the primordial stochastic gravitational wave background.Our investigation showed that an enhanced tensor amplitude can be achieved, within the framework of the Horndeski theory, if there is a short period where slow-roll inflation is violated. We considered a model of kinetically driven inflation where for a short time the scalar field velocity is heavily time-dependent. During that time the would-be decaying tensor mode becomes a growing mode. Analysis of the bispectrum showed that this can lead to sizeable tensor non-Gaussianities.We also considered possible realizations of the effective field theory of Scalar-Tensor gravity. In particular, we looked for a setup up of operators that could lead to the enhancement of parity violating effects for tensors. We introduced modifications to gravity which enabled us to parametrically approach the scale at which maximal parity violation occurs. Using the mathematical machinery for effective field theories we showed that sub-leading quadratic operators can become important signalling the presence of the Chern Simons instability. This inevitably implies the existence of non-trivial cubic interactions which could stand the theory strongly coupled at energies not far above the energy scale of inflation. Consequently, this can lead to large parity violation in tensor non-Gaussianity.

scholarly journals Gravitational-Wave Implications for the Parity Symmetry of Gravity at GeV Scale

2020 ◽  
Author(s):  
Yifan Wang ◽  
Rui Niu ◽  
Wen Zhao ◽  
Tao Zhu
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Particle Physics ◽  
Energy Region ◽  
High Energy ◽  
Energy Scale ◽  
High Energy Region ◽  
Parity Symmetry ◽  
Parity Conservation

Abstract Einstein's general relativity, as the most successful theory of gravity, is one of the cornerstones of modern physics. However, the experimental tests for gravity in the high energy region are limited. The emerging gravitational-wave astronomy has opened an avenue for probing the fundamental properties of gravity in strong and dynamical field, and in particular, high energy regime. In this work, we focus on the parity symmetry of gravity. For broken parity, the left- and right-handed modes of gravitational waves would follow different equations of motion, dubbed as birefringence. We perform the first full Bayesian inference of the parity conservation of gravity by comparing the state-of-the-art waveform with the compact binary coalescence data released by LIGO and Virgo collaboration. We do not find any violations of general relativity, thus obtain the lower bound of the parity-violating energy scale to be $0.09$ GeV through the velocity birefringence of gravitational waves. This provides the most stringent experimental test of gravitational parity symmetry up to date, and for the first time, in the high energy region, which ushers in a new era of using gravitational waves to test the ultraviolet behavior of gravity. We also find third-generation gravitational-wave detectors can enhance this bound to $\mathcal{O}(10^2)$ GeV if there is still no violation, comparable to the current LHC energy scale in particle physics.

scholarly journals ON THE CONTRIBUTION OF DENSITY PERTURBATIONS AND GRAVITATIONAL WAVES TO THE LOWER ORDER MULTIPOLES OF THE COSMIC MICROWAVE BACKGROUND RADIATION

2002 ◽  
Vol 11 (02) ◽  
pp. 259-297 ◽  
Author(s):  
A. DIMITROPOULOS ◽  
L. P. GRISHCHUK
Keyword(s):  
Dipole Moment ◽  
Gravitational Waves ◽  
Lower Order ◽  
Background Radiation ◽  
Infrared Divergence ◽  
Red Shift ◽  
Horizontal Line ◽  
Microwave Background ◽  
Microwave Background Radiation ◽  
Density Perturbations

The important studies of Peebles, and Bond and Efstathiou have led to the formula Cℓ= const. /[ℓ(ℓ+1)] aimed at describing the lower order multipoles of the CMBR temperature variations caused by density perturbations with the flat spectrum. Clearly, this formula requires amendments, as it predicts an infinitely large monopole C0, and a dipole moment C1 only 6/2 times larger than the quadrupole C2, both predictions in conflict with observations. We restore the terms omitted in the course of the derivation of this formula, and arrive at a new expression. According to the corrected formula, the monopole moment is finite and small, while the dipole moment is sensitive to short-wavelength perturbations, and numerically much larger than the quadrupole, as one would expect on physical grounds. At the same time, the function ℓ(ℓ+1)Cℓ deviates from a horizontal line and grows with ℓ, for ℓ≥2. We show that the inclusion of the modulating (transfer) function terminates the growth and forms the first peak, recently observed. We fit the theoretical curves to the position and height of the first peak, as well as to the observed dipole, varying three parameters: red-shift at decoupling, red-shift at matter-radiation equality, and slope of the primordial spectrum. It appears that there is always a deficit, as compared with the COBE observations, at small multipoles, ℓ~10. We demonstrate that a reasonable and theoretically expected amount of gravitational waves bridges this gap at small multipoles, leaving the other fits as good as before. We show that the observationally acceptable models permit somewhat "blue" primordial spectra. This allows one to avoid the infrared divergence of cosmological perturbations, which is otherwise present.

scholarly journals Gapped Goldstones at the cut-off scale: a non-relativistic EFT

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
G. Cuomo ◽  
A. Esposito ◽  
E. Gendy ◽  
A. Khmelnitsky ◽  
A. Monin ◽  
...  
Keyword(s):  
Effective Field Theory ◽  
Chemical Potential ◽  
Effective Field ◽  
Energy Scale ◽  
Field Theories ◽  
Conformal Field Theories ◽  
Strongly Coupled ◽  
Conformal Field ◽  
Charge Sector ◽  
Large Charge

Abstract At finite density, the spontaneous breakdown of an internal non-Abelian symmetry dictates, along with gapless modes, modes whose gap is fixed by the algebra and proportional to the chemical potential: the gapped Goldstones. Generically the gap of these states is comparable to that of other non-universal excitations or to the energy scale where the dynamics is strongly coupled. This makes it non-straightforward to derive a universal effective field theory (EFT) description realizing all the symmetries. Focusing on the illustrative example of a fully broken SU(2) group, we demonstrate that such an EFT can be constructed by carving out around the Goldstones, gapless and gapped, at small 3-momentum. The rules governing the EFT, where the gapless Goldstones are soft while the gapped ones are slow, are those of standard nonrelativistic EFTs, like for instance nonrelativistic QED. In particular, the EFT Lagrangian formally preserves gapped Goldstone number, and processes where such number is not conserved are described inclusively by allowing for imaginary parts in the Wilson coefficients. Thus, while the symmetry is manifestly realized in the EFT, unitarity is not. We comment on the application of our construction to the study of the large charge sector of conformal field theories with non-Abelian symmetries.

scholarly journals Analysis of Birefringence and Dispersion Effects from Spacetime-Symmetry Breaking in Gravitational Waves

Universe ◽  
2021 ◽  
Vol 7 (10) ◽  
pp. 380
Author(s):  
Kellie O’Neal-Ault ◽  
Quentin G. Bailey ◽  
Tyann Dumerchat  ◽  
Leïla Haegel ◽  
Jay Tasson
Keyword(s):  
Symmetry Breaking ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
New Physics ◽  
Effective Field ◽  
Cpt Violation ◽  
Cpt Symmetry ◽  
Spacetime Symmetry ◽  
Sensitivity Studies ◽  
Theory Framework

In this work, we review the effective field theory framework to search for Lorentz and CPT symmetry breaking during the propagation of gravitational waves. The article is written so as to bridge the gap between the theory of spacetime-symmetry breaking and the analysis of gravitational-wave signals detected by ground-based interferometers. The primary physical effects beyond General Relativity that we explore here are dispersion and birefringence of gravitational waves. We discuss their implementation in the open-source LIGO-Virgo algorithm library suite, and we discuss the statistical method used to perform a Bayesian inference of the posterior probability of the coefficients for symmetry-breaking. We present preliminary results of this work in the form of simulations of modified gravitational waveforms, together with sensitivity studies of the measurements of the coefficients for Lorentz and CPT violation. The findings show the high potential of gravitational wave sources across the sky to sensitively probe for these signals of new physics.

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