Post-Newtonian reference-ellipsoid for relativistic geodesy

Abstract

We apply general relativity to construct the post-Newtonian background manifold that serves as a reference spacetime in relativistic geodesy for conducting relativistic calculation of the geoid's undulation and the deflection of the plumb line from the vertical. We chose an axisymmetric ellipsoidal body made up of perfect homogeneous fluid uniformly rotating around a fixed axis, as a source generating the reference geometry. We, then, reformulate and extend hydrodynamic calculations of rotating fluids done by previous researchers to the realm of relativistic geodesy to set up algebraic equations defining the shape of the post-Newtonian reference ellipsoid. To complete this task, we explicitly perform all integrals characterizing gravitational field inside the fluid body and represent them in terms of the elementary functions depending on its eccentricity. We fully explore the coordinate freedom of the equations describing the post-Newtonian ellipsoid and demonstrate that the fractional deviation of the post-Newtonian level surface from the Maclaurin ellipsoid can be made much smaller than the previously anticipated estimate based on the coordinate gauge advocated by Bardeen and Chandrasekhar. We also derive the gauge-invariant relations of the post-Newtonian mass and the angular velocity of the rotating fluid with the parameters characterizing the shape of the post-Newtonian ellipsoid. We formulate the post-Newtonian theorems of Pizzetti and Clairaut that are used in geodesy to connect the geometric parameters of the reference ellipsoid to the physically measurable force of gravity at the pole and equator. Finally, we expand the post-Newtonian geodetic equations to the Taylor series with respect to the eccentricity of the ellipsoid and discuss their practical applications.

32 pages, 2 figures, 71 references. Text improved and extended, one more figure included

References in corpus (7)

• The Confrontation between General Relativity and Experiment
• Systematic evaluation of an atomic clock at 2e-18 total uncertainty
• A strontium lattice clock with $3\times 10^{-17}$ inaccuracy and its frequency
• Geophysical applicability of atomic clocks: direct continental geoid mapping
• Atomic clocks as a tool to monitor vertical surface motion
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Cited by in corpus (6)

• High Performance Clocks and Gravity Field Determination
• Chronometric geodesy: methods and applications
• Definition of the relativistic geoid in terms of isochronometric surfaces
• National Report to the International Association of Geodesy of the International Union of Geodesy and Geophysics 2015-2019
• Normal gravity field in relativistic geodesy
• Post-Newtonian Lagrangian of an N-body System with Arbitrary Mass and Spin Multipoles