Response to Fackerell's Article
  E. D. Fackerell claims: 1) that Alley and Yilmaz treatment of parallel slabs in general relativity is wrong because the Yilmaz metric used is not a solution of the field equations of general relativity; 2) he also claims that the correct treatment of the parallel slab problem in general relativity must be based on the so-called Taub metric. We show below that both of Fackerell's claims are false. His first claim is based on his failure to distinguish the matter-free regions and the regions with matter. His second claim is based on his failure to recognize that for the Taub metric the left-hand side, hence also the right-hand side of the field equations, are identically zero everywhere. Thus no material systems can be treated via the Taub metric. 
Carroll O. Alley (University of Maryland at College Park), Huseyin   Yilmaz (Hamamatsu Photonics and Tufts University)