Noether symmetry analysis for novel gravitational wave-like spacetimes and their conservation laws

2020 ◽  
Vol 35 (28) ◽  
pp. 2050234
Author(s):  
Amir Sultan Khan ◽  
Israr Ali Khan ◽  
Saeed Islam ◽  
Farhad Ali
Keyword(s):  
Black Holes ◽  
Conservation Laws ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Hawking Radiation ◽  
Conformal Factor ◽  
Noether Symmetries ◽  
Plane Symmetric ◽  
Symmetric Spacetimes ◽  
Symmetric Structure

The phenomena-like Hawking radiation, the collapse of black holes, and neutron stars decrease the curvature of spacetime continuously with the passage of time. The time conformal factor adds some curvature to nonstatic spacetime. In this article, some novel classes of nonstatic plane-symmetric spacetimes are explored by introducing a time conformal factor in the exact plane-symmetric spacetimes in such a way that their symmetric structure remains conserved. This technique re-scales the energy contents of the corresponding spacetimes, which comes with a re-scaled part in each spacetime. The invariant quantities corresponding to the Noether symmetries are also calculated.

Correction to the conservation laws in plane symmetric gravitational wave-like spacetimes

2018 ◽  
Vol 33 (21) ◽  
pp. 1850123 ◽  
Author(s):  
Farhad Ali ◽  
Wali Khan Mashwani ◽  
Muhammad Asif Jan
Keyword(s):  
Conservation Laws ◽  
Gravitational Wave ◽  
Conformal Factor ◽  
Time Dependent ◽  
Noether Symmetries ◽  
Plane Symmetric ◽  
Energy And Momentum ◽  
Symmetric Spacetime

This paper discusses the approximate Noether symmetries of the action of plane symmetric spacetime. A time-dependent conformal factor is introduced in the plane symmetric metric in such a way so as to obtain the same number of Noether symmetries as for the exact plane symmetric spacetime. The corresponding approximate conservation is obtained to discuss the conservation laws of the energy and momentum during the formation of gravitational wave.

scholarly journals Approximate Noether symmetries from geodetic Lagrangian for plane symmetric spacetimes

2015 ◽  
Vol 12 (10) ◽  
pp. 1550124 ◽  
Author(s):  
Farhad Ali ◽  
Tooba Feroze
Keyword(s):  
Conformal Factor ◽  
Noether Symmetries ◽  
Plane Symmetric ◽  
First Order ◽  
Symmetric Spacetimes ◽  
General Plane ◽  
Symmetric Spacetime ◽  
Conformal Plane ◽  
General Time

Noether symmetries from geodetic Lagrangian for time-conformal plane symmetric spacetime are presented. Here, time-conformal factor is used to find the approximate Noether symmetries. This is a generalization of the idea discussed,5–6 where they obtained approximate Noether symmetries from Lagrangian for a particular plane symmetric static spacetime. In the present paper, the most general plane symmetric static spacetime is considered and perturbed it by introducing a general time-conformal factor eϵf(t), where ϵ is very small which causes the perturbation in the spacetime. Taking the perturbation up to the first-order, we find all Lagrangian for plane symmetric spacetimes for which approximate Noether symmetries exist.

The stellar graveyard

2019 ◽  
pp. 177-206
Author(s):  
Nils Andersson
Keyword(s):  
Black Holes ◽  
General Relativity ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Stellar Evolution ◽  
White Dwarfs ◽  
Supermassive Black Holes ◽  
Compact Objects ◽  
Fermi Gases ◽  
The 1950S

This chapter introduces the different classes of compact objects—white dwarfs, neutron stars, and black holes—that are relevant for gravitational-wave astronomy. The ideas are placed in the context of developing an understanding of the likely endpoint(s) of stellar evolution. Key ideas like Fermi gases and the Chandrasekhar mass are discussed, as is the emergence of general relativity as a cornerstone of astrophysics in the 1950s. Issues associated with different formation channels for, in particular, black holes are considered. The chapter ends with a discussion of the supermassive black holes that are found at the centre of galaxies.

Dynamical versus isolated formation channels of gravitational wave sources

2018 ◽  
Vol 14 (S346) ◽  
pp. 397-416
Author(s):  
Michela Mapelli
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Theoretical Models ◽  
Stellar Winds ◽  
Core Collapse ◽  
Dynamical Processes ◽  
New Approach ◽  
The Impact

AbstractWhat are the formation channels of merging black holes and neutron stars? The first two observing runs of Advanced LIGO and Virgo give us invaluable insights to address this question, but a new approach to theoretical models is required, in order to match the challenges posed by the new data. In this review, I discuss the impact of stellar winds, core-collapse and pair instability supernovae on the formation of compact remnants in both isolated and dynamically formed binaries. Finally, I show that dynamical processes, such as the runaway collision scenario and the Kozai-Lidov mechanism, leave a clear imprint on the demography of merging systems.

Conservation laws corresponding to the Noether symmetries of the geodetic Lagrangian in spherically symmetric spacetimes

2017 ◽  
Vol 26 (05) ◽  
pp. 1741006 ◽  
Author(s):  
Bismah Jamil ◽  
Tooba Feroze
Keyword(s):  
Conservation Laws ◽  
Noether Symmetry ◽  
Complete List ◽  
Spherically Symmetric ◽  
Conserved Quantities ◽  
Noether Symmetries ◽  
Symmetric Spacetimes ◽  
Spherically Symmetric Spacetimes

In this paper, we present a complete list of spherically symmetric nonstatic spacetimes along with the generators of all Noether symmetries of the geodetic Lagrangian for such metrics. Moreover, physical and geometrical interpretations of the conserved quantities (conservation laws) corresponding to each Noether symmetry are also given.

Classification of Variational Conservation Laws of General Plane Symmetric Spacetimes

2017 ◽  
Vol 68 (3) ◽  
pp. 335 ◽  
Author(s):  
Usamah S. Al-Ali ◽  
Ashfaque H. Bokhari ◽  
A. H. Kara ◽  
Ghulam Shabbir
Keyword(s):  
Conservation Laws ◽  
Plane Symmetric ◽  
Symmetric Spacetimes ◽  
General Plane

scholarly journals Gravitational-wave astronomy: delivering on the promises

2018 ◽  
Vol 376 (2120) ◽  
pp. 20170279 ◽  
Author(s):  
B. F. Schutz
Keyword(s):  
Black Holes ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Binary Black Holes ◽  
Frequency Bands ◽  
The Future ◽  
Binary Neutron Stars ◽  
The Universe

Now that LIGO and Virgo have begun to detect gravitational-wave events with regularity, the field of gravitational-wave astronomy is beginning to realize its promise. Binary black holes and, very recently, binary neutron stars have been observed, and we are already learning much from them. The future, with improved sensitivity, more detectors and detectors like LISA in different frequency bands, has even more promise to open a completely hidden side of the Universe to our exploration. This article is part of a discussion meeting issue ‘The promises of gravitational-wave astronomy’.

IMPULSIVE LIGHT-LIKE SIGNALS

2002 ◽  
Vol 17 (20) ◽  
pp. 2746-2746
Author(s):  
C. BARRABÈS ◽  
P. A. HOGAN
Keyword(s):  
Black Holes ◽  
Neutron Star ◽  
Neutron Stars ◽  
Gravitational Wave ◽  
Gravitational Radiation ◽  
High Speed ◽  
Compact Objects ◽  
Speed Of Light ◽  
Gravitational Fields ◽  
Multipole Source

A general characterisation of an impulsive light–like signal was given1,2. The signal may consist of a shell of null matter and/or an impulsive gravitational wave. Both parts of the signal can be unambiguously identified3,4. The signals can be used to model bursts of gravitational radiation and light– like matter accompanying cataclysmic events such as supernovae and neutron star collisions. Also in high speed collisions of compact objects such as black–holes or neutron stars the gravitational fields of these objects resemble those of impulsive light–like signals when the objects are boosted to the speed of light. Several examples of impulsive light–like signals were presented, in particular those produced by recoil effects5 and by the Aichelburg–Sexl boost of an isolated gravitating multipole source6. The detection of these signals was also discussed7.

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