Gravitomagnetic Effects on Collective Plasma Oscillations in Compact Stars

The effects of gravitomagnetic force on plasma oscillations are investigated using the kinetic theory of homogeneous electrically neutral plasma in the absence of external electric or magnetic field. The random phase assumption is employed neglecting the thermal motion of the electrons with respect to a fixed ion background. It is found that the gravitomagnetic force reduces the characteristic frequency of the plasma thus enhancing the refractive index of the medium. The estimates for the predicted effects are given for a typical white dwarf, pulsar, and neutron star.     

Comments on “Gravitoelectric-Electric Coupling via Superconductivity“ by Douglas G. Torr and Ning Li

Torr and Li claim to have shown that experimentally detectable gravitomagnetic and gravitoelectric fields can be generated in a superconductor. We review their calculations and show that because of unrealistic assumptions the fields that they calculate are too large by many orders of magnitude.     

Letter: Coupling Gravitomagnetism—Spin and Berry's Phase

Resorting to Berry's phase, a new idea to detect, at quantum level, the gravitomagnetic field of any metric theory of gravity, is put forward. It is found in this proposal that the magnitude of the gravitomagnetic field appears only in the definition of the adiabatic regime, but not in the magnitude of the emerging geometric phase. In other words, the physical parameter to be observed does not involve, in a direct way, (as in the usual proposals) the tiny magnitude of the gravitomagnetic field.     

Frame Dragging and Lense-Thirring Effect

We first describe some phenomena due to spin and mass-energy currents on clocks and photons, in particular we derive the delay in the travel time of photons due to the spin of a body both inside a rotating shell and outside a rotating body. We then review the 1995–2001 measurements of the gravitomagnetic field of Earth and Lense-Thirring effect obtained by analyzing the orbits of the two laser-ranged satellites LAGEOS (LAser GEOdynamics Satellite) and LAGEOS II. Finally, we report the latest measurement of the Lense-Thirring effect, obtained in 2003 with the two LAGEOS satellites over more than 10 years of data. This 2003 result fully confirms and improves our previous measurements of the Earth frame-dragging: the Lense-Thirring effect exists and its experimental value is within ~20% of what is predicted by Einstein's theory of general relativity.     

Gravitoelectric-electric coupling via superconductivity

Recently we demonstrated theoretically that the carriers of quantized angular momentum in superconductors are not the Cooper pairs but the lattice ions, which must execute coherent localized motion consistent with the phenomenon of superconductivity. We demonstrate here that in the presence of an external magnetic field, the free superelectron and bound ion currents largely cancel providing a self-consistent microscopic and macroscopic interpretation of near-zero magnetic permeability inside superconductors. The neutral mass currents, however, do not cancel, because of the monopolar gravitational charge. It is shown that the coherent alignment of lattice ion spins will generate a detectable gravitomagnetic field, and in the presence of a time-dependent applied magnetic vector potential field, a detectable gravitoelectric field.     

Gravitomagnetic Effects

The paper summarizes the most important effects in Einsteinian gravitomagnetic fields related to propagating light rays, moving clocks and atoms, orbiting objects, and precessing spins. Emphasis is put onto the gravitational interaction of spinning objects. The gravitomagnetic field lines of a rotating or spinning object are given in analytic form.     

Gravitomagnetism in Metric Theories: Analysis of Earth Satellites Results, and Its Coupling with Spin

Employing the PPN formalism the gravitomagnetic field in different metheories is considered in the analysis of the LAGEOS results. It will be shown that there are several models that predict exactly the same effect that general relativity comprises. In other words, these Earth satellites results can be taken as experimental evidence that the orbital angular momentum of a body does indeed generate space–time geometry, nevertheless they do not endow general relativity with an outstanding status among metric theories. Additionally the coupling spin–gravitomagnetic field is analyzed with the introduction of the Rabi transitions that this field produces on a quantum system with spin 1/2. Afterwards, a continuous measurement of the energy of this system is introduced, and the consequences upon the corresponding probabilities of the involved gravitomagnetic field will be obtained. Finally, it will be proved that these proposals allows us, not only to confront against future experiments the usual assumption of the coupling spin–gravitomagnetism, but also to measure some PPN parameters and to obtain functional dependences among them.     

Gravitomagnetic and Gravitoelectric Waves in General Relativity: II

Well-known linearizations of Einstein's field equations and isomorphisms with electromagnetic theory allow one to demonstrate, in principle, the existence of gravitomagnetic (GM) and gravitoelectric (GE) wavefields generated by transient nongravitational sources—as in the spin-up of a rigid sphere by an external torque (Tolstoy, I. (2001). International Journal of Theoretical Physics 40(5), 1021–1031). Whereas such effects are currently too small to be measured in the laboratory, order of magnitude estimates suggest that major astrophysical events could generate signals (strains in the metric) observable by LIGO systems. GM/GE modes are entirely uncoupled from the quadrupole radiation of classic gravitational wave theory. However, both travel at light velocity c and, since quadrupole waves may be generated by, or in the neighborhood of, similar events, it is essential to demonstrate that LIGO array geometries can discriminate between them. This can be accomplished by determining arrival directions and polarization planes.     

Concerning Measurement of Gravitomagnetism in Electromagnetic Systems

Measurement of gravitomagnetic field is of fundamental importance as a test of general relativity. Here we present a new theoretical project for performing such a measurement based on detection of the electric field arising from the interplay between the gravitomagnetic and magnetic fields in the stationary axial-symmetric gravitational field of a slowly rotating massive body. Finally it is shown that precise magnetometers based on superconducting quantum interferometers could not be designed for measurement of the gravitomagnetically induced magnetic field in the cavity of a charged capacitor since they measure the circulation of a vector potential of electromagnetic field, i.e., an invariant quantity including the sum of electric and magnetic fields, and the general-relativistic magnetic part will be totally cancelled by the electric one which is in good agreement with the experimental results.