gravitational waves
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Luca Baiotti

AbstractI review the current global status of research on gravitational waves emitted from mergers of binary neutron star systems, focusing on general-relativistic simulations and their use to interpret data from the gravitational-wave detectors, especially in relation to the equation of state of compact stars.

Junlang Li ◽  
Teng Zhang

Abstract Position-meter and speed-meter interferometers have been analysed for detecting gravitational waves. Speed-meter is proposed to reduce the radiation pressure noise, which is dominant at low frequency. We introduce the concept of acceleration measurement in comparison with position and speed measurement. In this paper, we describe a general acceleration measurement and derive its standard quantum limit. We provide an example of an acceleration-meter interferometer configuration. We show that shot noise dominates at low frequency following a frequency dependence of $1/\Omega^2$, while radiation pressure noise is constant. The acceleration-meter has even a stronger radiation pressure noise suppression than speed-meter.

2022 ◽  
Vol 105 (2) ◽  
Qiang Wu ◽  
Tao Zhu ◽  
Rui Niu ◽  
Wen Zhao ◽  
Anzhong Wang

Universe ◽  
2022 ◽  
Vol 8 (1) ◽  
pp. 41
Viktor D. Stasenko ◽  
Alexander A. Kirillov ◽  
Konstantin M. Belotsky

The PBH clusters can be sources of gravitational waves, and the merger rate depends on the spatial distribution of PBHs in the cluster which changes over time. It is well known that gravitational collisional systems experience the core collapse that leads to significant increase of the central density and shrinking of the core. After core collapse, the cluster expands almost self-similarly (i.e., density profile extends in size without changing its shape). These dynamic processes affect the merger rate of PBHs. In this paper, the dynamics of the PBH cluster is considered using the Fokker–Planck equation. We calculate the merger rate of PBHs on cosmic time scales and show that its time dependence has a unique signature. Namely, it grows by about an order of magnitude at the moment of core collapse which depends on the characteristics of the cluster, and then decreases according to the dependence R∝t−1.48. It was obtained for monochromatic and power-law PBH mass distributions with some fixed parameters. Obtained results can be used to test the model of the PBH clusters via observation of gravitational waves at high redshift.

2022 ◽  
Vol 105 (2) ◽  
Toshiya Namikawa ◽  
Anton Baleato Lizancos ◽  
Naomi Robertson ◽  
Blake D. Sherwin ◽  
Anthony Challinor ◽  

Rabinarayan Swain ◽  
Priyasmita Panda ◽  
Hena Priti Lima ◽  
Bijayalaxmi Kuanar ◽  
Biswajit Dalai

Detection of Gravitational waves opened a new path for cosmological study in a new approach. From the detection of gravitational waves signal by advanced LIGO, its research climbed the peak. After the collaboration of LIGO and Virgo, several observations get collected from different sources of binary systems like black holes, binary neutron stars even both binary black hole and neutron star. The rigorous detection of gravitational signals may provide an additional thrust in the study of complex binary systems, dark matter, dark energy, Hubble constant, etc. In this review paper, we went through multiple research manuscripts to analyze gravitational wave signals. Here we have reviewed the history and current situation of gravitational waves detection, and we explained the concept and process of detection. Also, we go through different parts of a detector and their working. Then multiple gravitational wave signals are focused, originated from various sources and then found correlation between them. From this, the contribution of gravitational waves in different fields like complex binary systems (black holes, neutron stars), dark matter, dark energy and Hubble Constant have been discussed in this manuscript.

2022 ◽  
Vol 105 (2) ◽  
Rong-Gen Cai ◽  
Pei-Ze Ding ◽  
Zong-Kuan Guo ◽  
Chengjie Fu ◽  
Jing Liu

Symmetry ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 87
Júlio C. Fabris ◽  
Marcelo H. Alvarenga ◽  
Mahamadou Hamani Daouda ◽  
Hermano Velten

Unimodular gravity is characterized by an extra condition with respect to general relativity, i.e., the determinant of the metric is constant. This extra condition leads to a more restricted class of invariance by coordinate transformation: The symmetry properties of unimodular gravity are governed by the transverse diffeomorphisms. Nevertheless, if the conservation of the energy–momentum tensor is imposed in unimodular gravity, the general relativity theory is recovered with an additional integration constant which is associated to the cosmological term Λ. However, if the energy–momentum tensor is not conserved separately, a new geometric structure appears with potentially observational signatures. In this text, we consider the evolution of gravitational waves in a nonconservative unimodular gravity, showing how it differs from the usual signatures in the standard model. As our main result, we verify that gravitational waves in the nonconservative version of unimodular gravity are strongly amplified during the evolution of the universe.

2022 ◽  
Vol 105 (2) ◽  
Qi Chu ◽  
Manoj Kovalam ◽  
Linqing Wen ◽  
Teresa Slaven-Blair ◽  
Joel Bosveld ◽  

Tony Yuan

The relative velocity between objects with finite velocity affects the reaction between them. This effect is known as general Doppler effect. The Laser Interferometer Gravitational-Wave Observatory (LIGO) discovered gravitational waves and found their speed to be equal to the speed of light c. Gravitational waves are generated following a disturbance in the gravitational field; they affect the gravitational force on an object. Just as light waves are subject to the Doppler effect, so are gravitational waves. This article explores the following research questions concerning gravitational waves: What is the spatial distribution of gravitational waves? Can the speed of a gravitational wave represent the speed of the gravitational field (the speed of the action of the gravitational field upon the object)? What is the speed of the gravitational field? Do gravitational waves caused by the revolution of the Sun affect planetary precession? Can we modify Newton’s gravitational equation through the influence of gravitational waves?

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