27 research outputs found
Interpretation of the Global Anisotropy in the Radio Polarizations of Cosmologically Distant Sources
We present a detailed statistical study of the observed anisotropy in radio
polarizations from distant extragalactic objects. This anisotropy was earlier
found by Birch (1982) and reconfirmed by Jain and Ralston (1999) in a larger
data set. A very strong signal was seen after imposing the cut
rad/m, where is the rotation measure and
its mean value. In this paper we show that there are several indications that
this anisotropy cannot be attributed to bias in the data.
We also find that a generalized statistic shows a very strong signal in the
entire data without imposing the RM dependent cut. Finally we argue that an
anisotropic background pseudoscalar field can explain the observations.Comment: 13 pages, 6 figure
Astrometry and geodesy with radio interferometry: experiments, models, results
Summarizes current status of radio interferometry at radio frequencies
between Earth-based receivers, for astrometric and geodetic applications.
Emphasizes theoretical models of VLBI observables that are required to extract
results at the present accuracy levels of 1 cm and 1 nanoradian. Highlights the
achievements of VLBI during the past two decades in reference frames, Earth
orientation, atmospheric effects on microwave propagation, and relativity.Comment: 83 pages, 19 Postscript figures. To be published in Rev. Mod. Phys.,
Vol. 70, Oct. 199