Effects of a gravitomagnetic field on pure superconductors
Ning Li · D. Torr
Summary and citation · read the original at the source
In one page
A superconductor throws magnetic field out of its interior. That is the Meissner effect, and it is one of the first things anyone learns about superconductivity. Ning Li and Douglas Torr, working at the University of Alabama in Huntsville, asked what happens when a superconductor sits in a gravitomagnetic field as well. Gravitomagnetism is the part of general relativity that behaves like magnetism: a rotating mass drags the space near it, and the equations describing that drag look like the equations for a magnetic field. Li and Torr solve Maxwell's equations, the general-relativistic field equations and the London equations together, and find that the expulsion is not complete. A small residual uniform magnetic field pervades the superconductor, the external magnetic and gravitomagnetic fields induce further small internal fields in one another, and the two are tied together through the mass-to-charge ratio of the Cooper pairs that carry the supercurrent. It is a short paper, and it is the theoretical seed of chapter 11.
Why it matters hereThis is the peer-reviewed origin of the idea that a superconductor is not merely a place where gravity happens but a material that can act on a gravitomagnetic field. Chapter 11 runs the line forward from here to Podkletnov's spinning disc and Tajmar's measurements, and back to Gravity Probe B, which fixes how large a natural gravitomagnetic field actually is.
What it claims
01Li and Torr solve the coupled Maxwell, general-relativistic and London equations for the internal magnetic and gravitomagnetic fields of a pure superconductor exposed to external gravitomagnetic and magnetic fields.Abstract; theory sections
Published and peer-reviewed02The internal fields are given by expressions involving the gravitomagnetic and magnetic permeabilities of the superconductor, so the material's own properties set how strongly it responds.Abstract; results
Published and peer-reviewed03Although the Meissner effect ordinarily excludes all magnetic field from the interior of a superconductor, the analysis finds that a small residual uniform magnetic field will pervade the superconductor.Abstract
Published and peer-reviewed04The external gravitomagnetic and magnetic fields mutually induce additional small internal perturbation fields, and the two internal fields are related to one another through the Cooper-pair mass-to-charge ratio.Abstract; results
Published and peer-reviewed05The combined field expression decays exponentially over a characteristic distance, consistent with the requirement that the sum vanishes deep inside the superconductor; the gravitomagnetic penetration depth is larger than the ordinary magnetic penetration depth.Abstract; discussion
Published and peer-reviewed06Because the response is fixed by the superconductor's gravitomagnetic and magnetic permeabilities, how large an induced gravitomagnetic field can be made is a materials question rather than a question of principle — and a laboratory detection at the size the theory allows is the measurement that would settle it.Abstract; results
What to watch
The way in
https://doi.org/10.1103/PhysRevD.43.457Published by the American Physical Society as Phys. Rev. D 43, 457 (15 January 1991); the full text is behind the publisher's paywall. The record and abstract are free at OSTI (biblio 5986002). Both authors were at the Center for Space Plasma and Aeronomic Research, University of Alabama in Huntsville.
How to cite it
Ning Li, D. Torr (1991) Effects of a gravitomagnetic field on pure superconductors. doi:10.1103/PhysRevD.43.457
Where it sits in the curriculum
Gravity control and superconductorsInertia and gravity from the vacuum