Friday, July 5, 2013

1307.1202 (James M. Overduin et al.)

Expanded limits on violations of the equivalence principle from solar-system observations    [PDF]

James M. Overduin, Jack Mitcham, Zoey Warecki
Most attempts to bring gravity within the framework of the standard model of particle physics involve new fields that couple non-universally to standard-model fields, giving rise to composition-dependent "fifth forces" that violate the equivalence principle at small but potentially detectable levels. We use observational uncertainties in the positions and motions of solar-system bodies to constrain such violations, assuming that that the ratio of gravitational to inertial mass for each body differs from unity by a factor \Delta\ that can in principle differ from object to object. For suitable pairs of objects, it is possible to constrain three different linear combinations of \Delta\ using Kepler's third law, the migration of stable Lagrange points, and orbital polarization (the Nordtvedt effect). Limits of order 10^-10-10^-6 on \Delta\ for individual bodies can then be derived from planetary and lunar ephemerides, Cassini observations of the Saturn system, and observations of Jupiter's Trojan asteroids as well as recently discovered Trojan companions around the Earth, Mars, Neptune, and Saturnian moons. These results can be combined with models for elemental abundances in each body to test for composition-dependent violations of the universality of free fall in the solar system. The case of Dione and Tethys is particularly interesting, as one possesses a significant rocky core while the other is almost entirely ice.
View original:

No comments:

Post a Comment