Blueshift of a tachyon in the charged two-dimensional black hole.

Abstract

We study the propagation of string fields (metric ${\mathit{G}}_{\mathrm{\ensuremath{\mu}}\ensuremath{\nu}}$, Maxwell gauge potential ${\mathit{A}}_{\mathrm{\ensuremath{\mu}}}$, dilaton \ensuremath{\Phi}, and tachyon T) in a two-dimensional charged black hole. It is shown that the tachyon is a propagating field both inside and outside the black hole. This becomes infinitely blueshifted at the inner horizon. We confirm that the inner horizon is unstable, whereas the outer horizon is stable.