We study the dynamical behavior of the dilaton in the background of
three-dimensional Kerr-de Sitter space which is inspired from the low-energy
string effective action. The perturbation analysis around the cosmological
horizon of Kerr-de Sitter space reveals a mixing between the dilaton and other
fields. Introducing a gauge (dilaton gauge), we can disentangle this mixing
completely and obtain one decoupled dilaton equation. However it turns out that
this belongs to the tachyon. The stability of de Sitter solution with J=0 is
discussed. Finally we compute the dilaton absorption cross section to extract
information on the cosmological horizon of de Sitter space.Comment: 11 pages, reference added and a version to appear in PL
