postscript
3 Results...
Abstract...
Acknowledgements...
Rarefications such as stretching the cluster along the line of sight to twice
the apparent diameter or breaking it up into two clusters aligned along the
line of sight lower the X-ray limits by factors of roughly 2, corresponding to
changes in redshift of 
. Higher factors can be gained in principle
with these ideas, but at the cost of further reducing the observational
probability.
Changing the cosmology to the extreme case of an open model 
reduces the redshift limit only by 
. But since cluster formation
occurs earlier in an open model our result if interpreted as indication for a
very high-redshift cluster could imply a low matter content of the universe
(see, for example, Bartlett, these
proceedings).
We can not completely rule out the possibility of a hot, high redshift cluster in the vicinity of two quasars, a redshift of 3.8 is excluded at the 85% confidence level with our fairly conservative assumptions. But there is a good chance that the CMB decrement is not caused by a galaxy cluster. In any case the object can not be typical compared to known clusters. We therefore suggest to also investigate other explanations for the CMB decrement.