Speaker
Dr
Martin Tajmar
(Austrian Research Centers)
Description
The search for frame dragging around massive rotating objects such as the
Earth is an important test for general relativity and is actively pursued
with the LAGEOS and Gravity Probe-B satellites. Within the classical
framework, frame dragging is independent of the state (normal or coherent)
of the test mass. This was recently challenged by proposing that a large
frame-dragging field could be responsible for a reported anomaly of the
Cooper-pair mass found in Niobium superconductors. In 2003, a test program
was initiated at the Austrian Research Centers to investigate this conjecture
using sensitive accelerometers and fiber optic gyroscopes in the close
vicinity of fast spinning superconducting rings. The sensors are mounted
in close proximity to the superconductor in a separate evacuated,
mechanically and thermally de-coupled chamber. Recently obtained
high-precision data show that the angular velocity and acceleration applied
to the superconductor can indeed be seen on the sensors. The signal
amplitude is about 8 orders of magnitude below the values applied to the
ring for the case of Niobium at 4 Kelvin. The origin of the observed signals
so far is not clear. Our measurements and analysis suggest that the signal
can not be explained by mechanical influence or by carefully monitored
magnetic fields surrounding the sensors. If the frame dragging-like signals
are confirmed, their explanation must be sought outside of general
relativity. This talk will give an overview of the initial motivations and
the experimental program and discuss in particular the latest measurements
using fiber optic gyroscopes. Possible error sources as well as the
experimental difficulties are reviewed and discussed.
