3 research outputs found
Tidal Dynamics in Cosmological Spacetimes
We study the relative motion of nearby free test particles in cosmological
spacetimes, such as the FLRW and LTB models. In particular, the influence of
spatial inhomogeneities on local tidal accelerations is investigated. The
implications of our results for the dynamics of the solar system are briefly
discussed. That is, on the basis of the models studied in this paper, we
estimate the tidal influence of the cosmic gravitational field on the orbit of
the Earth around the Sun and show that the corresponding temporal rate of
variation of the astronomical unit is negligibly small.Comment: 12 pages, no figures, REVTeX 4.0; appendix added, new references, and
minor changes throughout; to appear in Classical and Quantum Gravity; v4:
error in (A24) of Appendix A corrected, results and conclusions unchanged. We
thank L. Iorio for pointing out the erro
Cosmological expansion and local physics
The interplay between cosmological expansion and local attraction in a
gravitationally bound system is revisited in various regimes. First, weakly
gravitating Newtonian systems are considered, followed by various exact
solutions describing a relativistic central object embedded in a Friedmann
universe. It is shown that the ``all or nothing'' behaviour recently discovered
(i.e., weakly coupled systems are comoving while strongly coupled ones resist
the cosmic expansion) is limited to the de Sitter background. New exact
solutions are presented which describe black holes perfectly comoving with a
generic Friedmann universe. The possibility of violating cosmic censorship for
a black hole approaching the Big Rip is also discussed.Comment: 17 pages, LaTeX, to appear in Phys. Rev.