More On Cosmological Gravitational Waves And Their Memories

Abstract

We extend recent theoretical results on the propagation of linear gravitational waves (GWs), including their associated memories, in spatially flat Friedmann--Lemaître--Robertson--Walker (FLRW) universes, for all spacetime dimensions higher than 3. By specializing to a cosmology driven by a perfect fluid with a constant equation-of-state $w$ -- conformal re-scaling, dimension-reduction and Nariai's ansatz may then be exploited to obtain analytic expressions for the graviton and photon Green's functions, allowing their causal structure to be elucidated. When $0<w\le 1$, the gauge-invariant scalar mode admits wave solutions, and like its tensor counterpart, likely contributes to the tidal squeezing and stretching of the space around a GW detector. In addition, scalar GWs in 4D radiation dominated universes -- like tensor GWs in 4D matter dominated ones -- appear to yield a tail signal that does not decay with increasing spatial distance from the source. We then solve electromagnetism in the same cosmologies, and point out a tail-induced electric memory effect. Finally, in even dimensional Minkowski backgrounds higher than 2, we make a brief but explicit comparison between the linear GW memory generated by point masses scattering off each other on unbound trajectories and the linear Yang-Mills memory generated by color point charges doing the same -- and point out how there is a "double copy" relation between the two.

84 pages, 1 figure

References in corpus (6)

• GW151226: Observation of Gravitational Waves from a 22-Solar-Mass Binary Black Hole Coalescence
• New Relations for Gauge-Theory Amplitudes
• Black holes and the double copy
• The Cosmological Memory Effect
• Generating exact solutions to Einstein's equation using linearized approximations
• The not-so-nonlinear nonlinearity of Einstein's equation

Cited by in corpus (22)

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• Spinning particles, axion radiation, and the classical double copy
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• Gravitational Memory in Higher Dimensions
• Gravitational radiation from the classical spinning double copy
• Charge Algebra in Al(A)dS${}_n$ Spacetimes
• The Radiative Double Copy for Einstein-Yang-Mills Theory
• BMS-like symmetries in cosmology
• Radiation of scalar modes and the classical double copy
• Gravitational wave memory and its tail in cosmology
• Memory effect in Yang-Mills theory
• Charges, conserved quantities and fluxes in de Sitter spacetime
• Gravitational wave cosmology I: high frequency approximation
• Holography and black holes in asymptotically flat FLRW
• Asymptotic symmetries and memories of gauge theories in FLRW spacetimes
• Asymptotic dynamics and charges for FLRW spacetimes
• Gravitational Tensor and Acoustic Waves in A Radiation Dominated Universe: Weyl Curvature and Polarization Patterns
• Gravitational wave memory in conformally flat spacetimes
• Laser Interferometer in Presence of Scalar field on Gravitational Wave Background
• Electromagnetic and Gravitational Radiation in All Dimensions: A Classical Field Theory Treatment
• Inflationary gravitational wave background as a tail effect
• Cherenkov Gravitational Radiation During the Radiation Era