A Proposal for Determining the Energy Content of Gravitational Waves by Using Approximate Symmetries of Differential Equations

Abstract

Since gravitational wave spacetimes are time-varying vacuum solutions of Einstein's field equations, there is no unambiguous means to define their energy content. However, Weber and Wheeler had demonstrated that they do impart energy to test particles. There have been various proposals to define the energy content but they have not met with great success. Here we propose a definition using "slightly broken" Noether symmetries. We check whether this definition is physically acceptable. The procedure adopted is to appeal to "approximate symmetries" as defined in Lie analysis and use them in the limit of the exact symmetry holding. A problem is noted with the use of the proposal for plane-fronted gravitational waves. To attain a better understanding of the implications of this proposal we also use an artificially constructed time-varying non-vacuum metric and evaluate its Weyl and stress-energy tensors so as to obtain the gravitational and matter components separately and compare them with the energy content obtained by our proposal. The procedure is also used for cylindrical gravitational wave solutions. The usefulness of the definition is demonstrated by the fact that it leads to a result on whether gravitational waves suffer self-damping.

26 pages, 6 figures

References in corpus (6)

• General Formula for the Momentum Imparted to Test Particles in Arbitrary Spacetimes
• Approximate Killing Vectors on S^2
• Approximate Noether Symmetries of the Geodesic Equations for the Charged-Kerr Spacetime and Rescaling of Energy
• A modification of the Chen-Nester quasilocal expressions
• Towards a wave-extraction method for numerical relativity. V. Extracting the Weyl scalars in the quasi-Kinnersley tetrad from spatial data
• Gravitational Wave Sources May Be "Further" Than We Think

Cited by in corpus (8)

• Charged Perfect Fluid Cylindrical Gravitational Collapse
• Effect of quintessence on the energy of the Reissner-Nordstrom black hole
• Killing and Noether Symmetries of Plane Symmetric Spacetime
• Noether Symmetries and Some Exact Solutions in $f(R,T^2)$ Theory
• A study of positive energy condition in Bianchi V spacetimes via Noether symmetries
• Energy Content of Colliding Plane Waves using Approximate Noether Symmetries
• Integration of the geodesic equations via Noether Symmetries
• Gravitational Wave Sources May Be "Further" Than We Think