# The image separation source redshift relation for gravitational lenses

Recently, it was noted by Park \& Gott (1997) that there is a statistically significant, strong, negative correlation between the image separation $\Delta\theta$ and source redshift $z_{\mathrm{s}}$ for gravitational lenses. This is somewhat puzzling if one believes in a flat ($k=0$) universe. Here, I look at possible causes of this effect and whether or not it is useful as a general cosmological test, using some data from the JVAS and CLASS surveys.

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Phillip Helbig's publications
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