Metrically Stationary, Axially Symmetric, Isolated Systems in Quasi-Metric Gravity

Abstract

The gravitational field exterior respectively interior to an axially symmetric, metrically stationary, isolated spinning source made of perfect fluid is examined within the quasi-metric framework. (A metrically stationary system is defined as a system which is stationary except for the direct effects of the global cosmic expansion on the space-time geometry.) Field equations are set up and an attempt is made to find an approximate series solution for the exterior part. However, the result is that no stationary solution corresponding to a spinning source can exist when considering terms beyond a certain order in small quantities. That is, except for metrically static systems, axially symmetric systems must necessarily be non-stationary in quasi-metric gravity. However, sufficiently weak, axially symmetric gravitational fields associated with slowly rotating sources, may still be considered as stationary as an excellent approximation. Thus a truncated, approximately stationary solution is found for the exterior field. To lowest order in small quantities, the gravito-magnetic part of the found metric family corresponds with the Kerr metric in the metric approximation. On the other hand, the gravito-electric part of the found metric family also includes a tidal term characterized by the free quadrupole-moment parameter $J_2$ describing the effect of source deformation due to the rotation. This term has no counterpart in the Kerr metric. Finally, the geodetic effect for a gyroscope in orbit is calculated. There is a correction term, unfortunately barely too small to be detectable by Gravity Probe B, to the standard expression.