  We introduce a set of scalar fields as test fields to study the dynamical
behaviors of the BTZ (Banados-Teitelboim-Zanelli) black hole. These include
minimally coupled scalar, conformally coupled scalar, dilaton, and tachyon. To
calculate the decay rate of the BTZ black hole, we consider both the Dirichlet
boundary condition at spatial infinity and the stability condition. It turns
out that the tachyon may be a relevant field to get information of the BTZ
black hole.
