Neil Ashby
Professor. Ph.D. Harvard University, 1961.

The principal emphasis of Prof. Ashby's research is on theoretical general relativity with practical applications. For example, studies of relativistic effects within navigational satellite systems such as the Global Positioning System (a set of 24 satellites carrying atomic clocks) show that several relativistic effects must be accounted for in order for the system work properly.

Another application is to the study of relativistic perturbations of the motion of earth-orbiting satellites, and to the interpretation of the results of accurate laser ranging experiments from the earth to such satellites as LAGEOS. Accounting for relativistic effects due to motion of the earth around the sun, such as the effects of Lorentz contraction and breakdown of simulataneity, on the higher order multipole gravitational potentials of the earth, is important in the determination of the earth's mass. Simulation of accurate ranging between the Earth and an orbiter or lander on the planet Mercury show that ranging experiments are among the best available techniques to test alternative theories of gravitation. Another area of current active interest is the generation of gravitation waves by compact objects such as neutron stars, spiraling into, and being captured by, very massive black holes.

A secondary area of interest is statistical mechnics. In particular, solutions of the Uehling-Uhlenbeck equations are being studied with the aid of a set of orthogoanl polynomials, analagous to Sonine polynomials, but constructed to provide convenient solutions to the problem of transport in situations where quantum effects are important. Applications being looked at included transport in mixtures of liquid Helium II, liquid helium IV, and dilute gases at low temperatures.

Selected Publications

* "Canonical Planetary Perturbation Equations for Velocity-Dependent Forces, and the Lense-Thirring Precession," N. Ashby, T. Allison, Celestial Mechanics and Dynamical Astronomy 57, 537-585 (1993).
* "Mercury Relativity Orbiter Mission," N. Ashby, P.L. Bender, I. Ciufolini, L. Iess, Proceedings of the Symposium on Future Fundamental Physics Missions in Space and Enabling Technologies, 5-7 April 1994, El Escorial, Spain (Eds. J. Leon And J. Perez-Mercader, Instituto Nacional de Tecnica Aeroespacial, Madrid.)
* "Relativity in the Future of Engineering," N. Ashby, IEEE Transactions on Instrumentation and Measurement 43, 505-514 (1994).
* "Introduction to Relativistic Effects in the Global Positioning System," N. Ashby, J.J. Spilker, Jr., Ch. 18 in The Global Positioning System--Theory and Application, Eds B.W. Parkinson, J.J. Spilker, Jr., American Institute of Aeronautics and Astronautics, (1995).