MG11 
Talk detail
 

 Participant 

Institution

Session

Talk

Abstract

The Equivalence Principle and its tests in the context of Gravity, Quantum Mechanics and Cosmology

This paper is an overview of the tests, validity and meaning of the equivalence principle. I will review the empirical evidence and possible gaps in the classical context as well as in the context of quantum dynamics. I will discuss the possibility of direct and indirect tests of the equivalence principle for the Casimir energy, and for energy in quantum vacuum in general. Closely related is the question of the active gravitational mass of the quantum vacuum. A reliable strategy for drawing empirical conclusions in such experimentally difficult situations based on conservation principles and supplementary experiments will be outlined. The equivalence principle will be analyzed in the context of cosmology, and will be shown to be directly related to the properties of the universe. This implies the need for a revision of the meaning of the results from high sensitivity tests of the equivalence principle.

New measurements on the one-way speed of light and its relation to clock-comparison experiments

I report on new measurements on the one-way speed of light relative to an inertially moving source-detector combination using an interferometric technique that does not require synchronization of distant clocks using light signals, thus avoiding the circularity in the logic of the special relativistic assertion of the absolute constancy of the speed of light relative to inertially moving observers. The technique also disentangles the Doppler shift and the issue of the speed of light, unlike in several other experiments where these two gets mixed up. It will be shown that these measurements are closely related to experiments on clock comparison, and I will draw some general conclusions regarding the overall consistency and empirical basis for the special theory of relativity. The results have important implications and interpretation in the context of our present day cosmology.

Einstein’s analysis of the twin-clock problem and the role of gravity: A surprise

Einstein wrote a paper in 1918 criticizing the “inadequate” resolutions till then of the twin-paradox in relativity, and suggesting the correct resolution, under pressure from his friends and the friendly editor of Naturwissenschaften, to answer his severe and vocal critics in Germany. This paper is almost never referred to, except in a few writings, in the vast literature on the twin-clock problem. It contained two surprises: it explicitly stated that the twins age symmetrically in the special relativistic analysis. Then it invoked the general theory of relativity and the gravitational time dilation to resolve the paradox that arose in special relativity, confirming earlier criticisms that within special relativity there was no resolution of the paradox. I have recently analyzed the paper by Einstein, and reconstructed the derivation that Einstein mentioned but did not include in the paper. It turns out that there is a further a surprise in that Einstein’s resolution also fails for realistic clocks. In this talk, I will discuss the twin-clock problem in the context of Einstein’s historically and politically important paper in 1918.

Measurement of the Casimir force in the range above 5 microns employing a torsion balance

I will report on a new measurement of the Casimir force between a plane conducting surface and spherical conducting surface, in the range of separation 3-10 microns, employing a torsion balance. The results show a deviation from the zero temperature force law and this deviation is consistent with the finite temperature corrections, indicating that this could be the first measurement in which the finite temperature correction is seen. The need to subtract out large electrostatic effects limits the accuracy of our measurements.