Spacetime, spin and Gravity Probe B

Overduin, James

doi:10.1088/0264-9381/32/22/224003

Cited by 12 publications

(11 citation statements)

References 94 publications

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“…Gravity Probe B is a gyroscope experiment in orbit around the Earth, that monitors the spin dynamics of four cryogenic gyroscopes onboard, relative to a remote guiding star. The analysis revealed a geodetic-precessing drift and a frame-dragging drift at precision of 0.3% and 19%, respectively, in agreement with GR [125,126].…”

supporting

confidence: 54%

Tests of gravitational symmetries with radio pulsars

Shao

Wex

2016

Sci. China Phys. Mech. Astron.

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Symmetries play important roles in modern theories of physical laws. In this paper, we review several experimental tests of important symmetries associated with the gravitational interaction, including the universality of free fall for self-gravitating bodies, time-shift symmetry in the gravitational constant, local position invariance and local Lorentz invariance of gravity, and spacetime translational symmetries. Recent experimental explorations for post-Newtonian gravity are discussed, of which, those from pulsar astronomy are highlighted. All of these tests, of very different aspects of gravity theories, at very different length scales, favor to very high precision the predictions of the strong equivalence principle (SEP) and, in particular, general relativity which embodies SEP completely. As the founding principles of gravity, these symmetries are motivated to be promoted to even stricter tests in future.Comment: 23 pages, 9 figures. Invited review article, minor modifications to match published versio

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supporting

confidence: 54%

Tests of gravitational symmetries with radio pulsars

Shao

Wex

2016

Sci. China Phys. Mech. Astron.

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“…These quantities have proved useful in, for example, classifying metrics [3,4] and deciding whether or not they are equivalent [5,6]. They have been applied to speed up the estimation of gravitational-wave signatures from black-hole collisions [7], to distinguish between "gravito-electrically" versus "gravito-magnetically dominated" regions of spacetime [8][9][10], to measure the mass and spin and locate the horizons of black holes [11][12][13][14], and to study perturbations of the Kerr metric [15], Lorentzian wormholes [16], and others [17].…”

Section: Introductionmentioning

confidence: 99%

Curvature Invariants for Charged and Rotating Black Holes

et al. 2020

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Riemann curvature invariants are important in general relativity because they encode the geometrical properties of spacetime in a manifestly coordinate-invariant way. Fourteen such invariants are required to characterize four-dimensional spacetime in general, and Zakhary and McIntosh showed that as many as seventeen can be required in certain degenerate cases. We calculate explicit expressions for all seventeen of these Zakhary–McIntosh curvature invariants for the Kerr–Newman metric that describes spacetime around black holes of the most general kind (those with mass, charge, and spin), and confirm that they are related by eight algebraic conditions (dubbed syzygies by Zakhary and McIntosh), which serve as a useful check on our results. Plots of these invariants show richer structure than is suggested by traditional (coordinate-dependent) textbook depictions, and may repay further investigation.

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“…In the proposed experiment, the parameter g is the gyrogravitational ratio: the ratio between intrinsic spin and angular momentum coefficients in the theoretical description of relativistic precession. If gravity affects intrinsic spin identically to orbital angular momentum, then g = 1, as expected based on Einstein's equivalence principle applied to intrinsic spin [19,[36][37][38][39]. In other approaches g differs from unity: for example, g = 2 in Refs.…”

mentioning

confidence: 77%

“…In principle, the projected measurement sensitivity of such a "Gravity Probe Spin" experiment is sufficient to measure the de Sitter and Lense-Thirring effects for g = 1. Consequently, stringent bounds will result on parametrized post-Newtonian (PPN) physics, scalar-tensor theories, and other standard-model extensions [36]. By comparing the sensitivity of Gravity Probe Spin to existing experimental bounds on anomalous gravity-induced spinprecession [76][77][78] as shown in Fig.…”

mentioning

confidence: 99%

Gravity Probe Spin: Prospects for measuring general-relativistic precession of intrinsic spin using a ferromagnetic gyroscope

Fadeev,

Wang,

Band

et al. 2020

Preprint

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An experimental test at the intersection of quantum physics and general relativity is proposed: measurement of relativistic frame dragging and geodetic precession using intrinsic spin of electrons. The behavior of intrinsic spin in spacetime dragged and warped by a massive rotating body is an experimentally open question, hence the results of such a measurement could have important theoretical consequences. Such a measurement is possible by using mm-scale ferromagnetic gyroscopes in orbit around the Earth. Under conditions where the rotational angular momentum of a ferromagnet is sufficiently small, a ferromagnet's angular momentum is dominated by atomic electron spins and is predicted to exhibit macroscopic gyroscopic behavior. If such a ferromagnetic gyroscope is sufficiently isolated from the environment, rapid averaging of quantum uncertainty via the spin-lattice interaction enables readout of the ferromagnetic gyroscope dynamics with sufficient sensitivity to measure both the Lense-Thirring (frame dragging) and de Sitter (geodetic precession) effects due to the Earth.

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Spacetime, spin and Gravity Probe B

Cited by 12 publications

References 94 publications

Tests of gravitational symmetries with radio pulsars

Tests of gravitational symmetries with radio pulsars

Curvature Invariants for Charged and Rotating Black Holes

Gravity Probe Spin: Prospects for measuring general-relativistic precession of intrinsic spin using a ferromagnetic gyroscope

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