CONSTRAINING COSMOLOGICAL TOPOLOGY VIA HIGHLY LUMINOUS X-RAY-CLUSTERS

The topology of the observable Universe is not yet known. The most sig nificant observational sign of a non-trivial topology would be multipl e images ('ghosts') of a single object at (in general) different sky p ositions and redshifts. It is pointed out that the previous search by Gott for ghost images of the Coma cluster can be extended by using hig hly X-ray-luminous clusters of galaxies. This is likely to be more eff icient than with other astrophysical objects viewable on these scales, since (1) X-ray clusters would be at least as easy to identify if vie wed from other angles as any other objects, and (2) the evolution of t he X-ray-emitting, thermally heated gas is likely to be simpler than f or other objects. Possibilities that the highly luminous cluster RX J1 347.5 - 1145 (z = 0.45) has a 'ghost image' at lower redshift are anal ysed. It is noted that RX J1347.5 - 1145, the Coma cluster and the clu ster CL 09104 + 4109 form nearly a right angle (approximate to 88 degr ees) with arms of nearly identical length (970 and 960 h(-1) Mpc respe ctively) for Omega(0) = 1, lambda(0) = 0 ghost images of one and the s ame cluster, for a hypertoroidal T-3 topology However, several argumen ts are presented that this relation is not physical.