Geodesics for the Painleve-Gullstrand form of Lense-Thirring spacetime

Joshua Baines; Thomas Berry; Alex Simpson; Matt Visser

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arXiv · 2112.05228

Geodesics for the Painleve-Gullstrand form of Lense-Thirring spacetime

Joshua Baines·Thomas Berry·Alex Simpson·Matt Visser

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Abstract

Recently, the current authors have formulated and extensively explored a rather novel Painleve-Gullstrand variant of the slow-rotation Lense-Thirring spacetime, a variant which has particularly elegant features -- including unit lapse, intrinsically flat spatial 3-slices, and a separable Klein-Gordon equation (wave operator). This spacetime also possesses a non-trivial Killing tensor, implying separability of the Hamilton-Jacobi equation, the existence of a Carter constant, and complete formal integrability of the the geodesic equations. Herein we investigate the geodesics in some detail, in the general situation demonstrating the occurrence of "ultra-elliptic" integrals. Only in certain special cases can the complete geodesic integrability be explicitly cast in terms of elementary functions. The model is potentially of astrophysical interest both in the asymptotic large-distance limit and as an example of a "black hole mimic", a controlled deformation of the Kerr spacetime that can be contrasted with ongoing astronomical observations.

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Joshua Baines, Thomas Berry, Alex Simpson, Matt Visser. 2021-12-09. Geodesics for the Painleve-Gullstrand form of Lense-Thirring spacetime. https://arxiv.org/abs/2112.05228

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