scholarly journals Strong gravity signatures in the polarization of gravitational waves

2019 ◽  
Vol 28 (14) ◽  
pp. 1944020 ◽  
Author(s):  
S. Shankaranarayanan
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Modified Gravity ◽  
Strong Field ◽  
Normal Modes ◽  
Strong Gravity ◽  
Modified Gravity Theories ◽  
Gravitational Wave Detectors ◽  
Gravity Theories

General Relativity is a hugely successful description of gravitation. However, both theory and observations suggest that General Relativity might have significant classical and quantum corrections in the Strong Gravity regime. Testing the strong field limit of gravity is one of the main objectives of the future gravitational wave detectors. One way to detect strong gravity is through the polarization of gravitational waves. For quasi-normal modes of black-holes in General Relativity, the two polarization states of gravitational waves have the same amplitude and frequency spectrum. Using the principle of energy conservation, we show that the polarizations differ for modified gravity theories. We obtain a diagnostic parameter for polarization mismatch that provides a unique way to distinguish General Relativity and modified gravity theories in gravitational wave detectors.

scholarly journals Relic gravitational waves in cosmological models based on the modified gravity theories

2021 ◽  
Vol 2081 (1) ◽  
pp. 012002
Author(s):  
I V Fomin ◽  
S V Chervon
Keyword(s):  
Energy Density ◽  
Gravitational Waves ◽  
Modified Gravity ◽  
Direct Detection ◽  
Cosmological Models ◽  
Observational Constraints ◽  
Cosmological Perturbations ◽  
Modified Gravity Theories ◽  
Relic Gravitational Waves ◽  
Gravity Theories

Abstract We consider cosmological models based on the generalized scalar-tensor gravity, which correspond to the observational constraints on the parameters of cosmological perturbations for any model’s parameters. The estimates of the energy density of relic gravitational waves for such a cosmological models were made. The possibility of direct detection of such a gravitational waves using modern and prospective methods was discussed as well.

The laser gravitational compass: A spheroidal interferometric gravitational observatory

2020 ◽  
Vol 35 (02n03) ◽  
pp. 2040020
Author(s):  
Ivan S. Ferreira ◽  
C. Frajuca ◽  
Nadja S. Magalhaes ◽  
M. D. Maia ◽  
Claudio M. G. Sousa
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
Gravitational Wave Detectors ◽  
Alternative Theories ◽  
Theories Of Gravitation

Using the observational properties of Einstein’s gravitational field it is shown that a minimum of four non-coplanar mass probes are necessary for a Michelson and Morley interferometer to detect gravitational waves within the context of General Relativity. With fewer probes, some alternative theories of gravitation can also explain the observations. The conversion of the existing gravitational wave detectors to four probes is also suggested.

scholarly journals Blackhole in nonlocal gravity: comparing metric from Newmann–Janis algorithm with slowly rotating solution

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Utkarsh Kumar ◽  
Sukanta Panda ◽  
Avani Patel
Keyword(s):  
General Relativity ◽  
Gravitational Field ◽  
Modified Gravity ◽  
Kerr Metric ◽  
Slow Rotation ◽  
Field Equations ◽  
External Region ◽  
Modified Gravity Theories ◽  
Spacetime Metric ◽  
Gravity Theories

Abstract The strong gravitational field near massive blackhole is an interesting regime to test General Relativity (GR) and modified gravity theories. The knowledge of spacetime metric around a blackhole is a primary step for such tests. Solving field equations for rotating blackhole is extremely challenging task for the most modified gravity theories. Though the derivation of Kerr metric of GR is also demanding job, the magical Newmann–Janis algorithm does it without actually solving Einstein equation for rotating blackhole. Due to this notable success of Newmann–Janis algorithm in the case of Kerr metric, it has been being used to obtain rotating blackhole solution in modified gravity theories. In this work, we derive the spacetime metric for the external region of a rotating blackhole in a nonlocal gravity theory using Newmann–Janis algorithm. We also derive metric for a slowly rotating blackhole by perturbatively solving field equations of the theory. We discuss the applicability of Newmann–Janis algorithm to nonlocal gravity by comparing slow rotation limit of the metric obtained through Newmann–Janis algorithm with slowly rotating solution of the field equation.

scholarly journals Testing dispersion of gravitational waves from eccentric extreme-mass-ratio inspirals

2019 ◽  
Vol 28 (15) ◽  
pp. 1950166
Author(s):  
Shu-Cheng Yang ◽  
Wen-Biao Han ◽  
Shuo Xin ◽  
Chen Zhang
Keyword(s):  
General Relativity ◽  
Gravitational Waves ◽  
Modified Gravity ◽  
Arrival Time ◽  
Graviton Mass ◽  
Mass Ratio ◽  
Dispersion Effect ◽  
Intermediate Mass ◽  
Modified Gravity Theories ◽  
Better Than

In general relativity, there is no dispersion in gravitational waves, while some modified gravity theories predict dispersion phenomena in the propagation of gravitational waves. In this paper, we demonstrate that this dispersion will induce an observable deviation of waveforms if the orbits have large eccentricities. The mechanism is that the waveform modes with different frequencies will be emitted at the same time due to the existence of eccentricity. During the propagation, because of the dispersion, the arrival time of different modes will be different, then produce the deviation and dephasing of waveforms compared with general relativity. This kind of dispersion phenomena related with extreme-mass-ratio inspirals could be observed by space-borne detectors, and the constraint on the graviton mass could be improved. Moreover, we find that the dispersion effect may also be constrained by ground detectors better than the current result if a highly eccentric intermediate-mass-ratio inspirals be observed.

scholarly journals Generic off-diagonal solutions and solitonic hierarchies in (modified) gravity

2015 ◽  
Vol 30 (19) ◽  
pp. 1550090 ◽  
Author(s):  
Sergiu I. Vacaru
Keyword(s):  
General Relativity ◽  
Exact Solutions ◽  
Modified Gravity ◽  
Field Equations ◽  
Physical Data ◽  
Modified Gravity Theories ◽  
De Vries ◽  
Einstein Spaces ◽  
Curve Flows ◽  
Gravity Theories

We have summarized our recent results on encoding exact solutions of field equations in Einstein and modified gravity theories into solitonic hierarchies derived for nonholonomic curve flows with associated bi-Hamilton structure. We argue that there is a canonical distinguished connection for which the fundamental geometric/physical equations decouple in general form. This allows us to construct very general classes of generic off-diagonal solutions determined by corresponding types of generating and integration functions depending on all (spacetime) coordinates. If the integral varieties are constrained to zero torsion configurations, we can extract solutions for the general relativity (GR) theory. We conclude that the geometric and physical data for various classes of effective/modified Einstein spaces can be encoded into multi-component versions of the sine-Gordon, or modified Korteweg–de Vries equations.

scholarly journals The Polarizations of Gravitational Waves

Universe ◽  
2018 ◽  
Vol 4 (8) ◽  
pp. 85 ◽  
Author(s):  
Yungui Gong ◽  
Shaoqi Hou
Keyword(s):  
General Relativity ◽  
Gravitational Wave ◽  
Gravitational Waves ◽  
High Speed ◽  
Strong Field ◽  
Alternative Theories Of Gravity ◽  
Pulsar Timing ◽  
Theories Of Gravity ◽  
Alternative Theories

The gravitational wave provides a new method to examine General Relativity and its alternatives in the high speed, strong field regime. Alternative theories of gravity generally predict more polarizations than General Relativity, so it is important to study the polarization contents of theories of gravity to reveal the nature of gravity. In this talk, we analyze the polarization contents of Horndeski theory and f(R) gravity. We find out that in addition to the familiar plus and cross polarizations, a massless Horndeski theory predicts an extra transverse polarization, and there is a mix of pure longitudinal and transverse breathing polarizations in the massive Horndeski theory and f(R) gravity. It is possible to use pulsar timing arrays to detect the extra polarizations in these theories. We also point out that the classification of polarizations using Newman–Penrose variables cannot be applied to massive modes. It cannot be used to classify polarizations in Einstein-æther theory or generalized Tensor-Vector-Scalar (TeVeS) theory, either.

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