On Witten's instability and winding tachyons

We investigate, from a spacetime perspective, some aspects of Horowitz'srecent conjecture that black strings may catalyze the decay of Kaluza-Kleinspacetimes into a bubble of nothing. We identify classical configurations thatinterpolate between flat space and the bubble, and discuss the energetics ofthe transition. We investigate the effects of winding tachyons on the size andshape of the barrier and find no evidence at large compactification radius thattachyons enhance the tunneling rate. For the interesting radii, of order thestring scale, the question is difficult to answer due to the failure of the$\alpha^\prime$ expansion.Comment: 15 pages, 2 figures, Late