Wayne A. Christiansen, David J. E. Floyd, Y. Jack Ng, Eric S. Perlman. Limits on Spacetime Foam
Submitted on: Aug 26, 2012, 06:26:23
Natural Sciences / Astronomy / Cosmology
Description: Plausibly spacetime is "foamy" on small distance scales, due to quantum fluctuations. We elaborate on the proposal to detect spacetime foam by looking for seeing disks in the images of distant quasars and AGNs. This is a null test in the sense that the continued presence of unresolved "point" sources at the milli-arc second level in samples of distant compact sources puts severe constraints on theories of quantized spacetime foam at the Planckian level. We discuss the geometry of foamy spacetime, and the appropriate distance measure for calculating the expected angular broadening. We then deal with recent data and the constraints they put on spacetime foam models. While time lags from distant pulsed sources such as GRBs have been posited as a possible test of spacetime foam models, we demonstrate that the time-lag effect is rather smaller than has been calculated, due to the equal probability of positive and negative fluctuations in the speed of light inherent in such models.
The abstract of this article will be published in the August 2012 issue of "Intellectual Archive Bulletin", ISSN 1929-1329.
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