Tachyonic compactification

The geometry generated by a tachyon of (mass)2=-m2, which crosses the Universe along the z axis, is analyzed. By the same token that a black hole is stationary and hot, the analogous tachyonic geometry is z independent and z periodic (z=8m), respectively, inside the Cherenkov cylinder. Generalized to five dimensions, the tachyonic motion generates the Witten geometry, with the effective four-geometry being Lorentz but notably not Poincaré invariant. The generalized Kruskal analysis is explicitly performed.