The status of experimental tests of general relativity and of theoretical frameworks for analyzing them is reviewed and updated. Einstein’s equivalence principle (EEP) is well supported by experiments such as the Eotvos experiment, tests of local Lorentz invariance and clock experiments. Ongoing tests of EEP and of the inverse square law are searching for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light deflection, the Shapiro time delay, the perihelion advance of Mercury, the Nordtvedt effect in lunar motion, and frame-dragging. Gravitational wave damping has been detected in an amount that agrees with general relativity to better than half a percent using the Hulse-Taylor binary pulsar, and a growing family of other binary pulsar systems is yielding new tests, especially of strong-field effects. Current and future tests of relativity will center on strong gravity and gravitational waves.

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The Confrontation Between General Relativity and Experiment

Cosmology and the fate of dilatation symmetry

We discuss the cosmological constant problem in the light of dilatation symmetry and its possible anomaly. For dilatation symmetric quantum theories realistic asymptotic cosmology is obtained provided the effective potential has a non-trivial minimum. For theories with dilatation anomaly one needs as a non-trivial "cosmon condition" that the energy-momentum tensor in the vacuum is purely anomalous. Such a condition is related to the short-distance renormalization group behavior of the fundamental theory. Observable deviations from the standard hot big bang cosmology are possible.

Cosmology and the Fate of Dilatation Symmetry

Metric affine gauge theory of gravity: Field equations, Noether identities, world spinors, and breaking of dilation invariance

Advances in atomic physics, such as cooling and trapping of atoms and molecules and developments in frequency metrology, have added orders of magnitude to the precision of atom-based clocks and sensors. Applications extend beyond atomic physics and this article reviews using these new techniques to address important challenges in physics and to look for variations in the fundamental constants, search for interactions beyond the standard model of particle physics, and test the principles of general relativity.

Search for New Physics with Atoms and Molecules

We have carefully reexamined the results of the experiment of E\"otv\"os, Pek\'ar, and Fekete, which compared the accelerations of various materials to the Earth. We find that the E\"otv\"os-Pek\'ar-Fekete data are sensitive to the composition of the materials used, and that their results support the existence of an intermediate-range coupling to baryon number or hypercharge.

Reanalysis of the Eo uml tvös experiment

We have carefully reexamined the results of the experiment of Eotvos, Pekar, and Fekete, which compared the accelerations of various materials to the Earth. We find that the Eotvos-Pekar-Fekete data are sensitive to the composition of the materials used, and that their results support the existence of an intermediate-range coupling to baryon number or hypercharge.

Reanalysis of the Eötvös Experiment.

Long-range forces and the Eötvös experiment

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Fischbach et al. respond.

We present a phenomenological description of the ''fifth force'' which focuses on the implications of the existing data from satellite and geophysical measurements of gravity, the Eoetvoes experiment, decays into hyperphotons, and the energy-dependence of the K/sup 0/ - anti K/sup 0/ parameters.

Aaron Szafer

Papers

Reanalysis of the Eo uml tvös experiment

Reanalysis of the Eötvös Experiment.

Long-range forces and the Eötvös experiment

Fischbach et al. respond.

The fifth force