Extended-body motion in black hole spacetimes: What is possible?
arXiv:2011.00110 · doi:10.1103/PhysRevD.102.124075
Abstract
Free-fall is only approximately universal in general relativity. Different extended bodies can fall in different ways, depending on their internal dynamics. Nevertheless, certain aspects of their motion are universal. This paper examines the universal constraints on extended-body motion in vacuum type D spacetimes. Working in the quadrupole approximation, we show that in addition to the (previously-known) constraints imposed by Killing vectors, two components of the gravitational torque must vanish. Furthermore, of the ten components of a body's quadrupole moment, four are found to be irrelevant, two can affect only the force, and the remaining four can affect both forces and torques. As an application, we consider the capabilities of a hypothetical spacecraft which controls its motion by controlling its internal structure. In the Schwarzschild spacetime, such a spacecraft can control its mass, and in doing so, it can stabilize unstable orbits, escape from bound orbits, and more -- all without a rocket.
20 pages, 5 figures, minor changes
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Cited by in corpus (7)
- Circular equatorial orbits of extended bodies with spin-induced quadrupole around a Kerr black hole: Comparing spin-supplementary conditions
- On the integrability of extended test body dynamics around black holes
- Symplectic mechanics of relativistic spinning compact bodies II.: Canonical formalism in the Schwarzschild spacetime
- Free-falling motion of an elastic rigid rod towards a Schwarzschild black hole
- Extended body dynamics in general relativity: hyperelastic models
- Extended bodies with spin induced quadrupoles on circular equatorial orbits in Kerr spacetime
- Encounter between an extended hyperelastic body and a Schwarzschild black hole with quadrupole-order effects