Tachyon and fixed scalars of D5(+/-)-D1(+/-) black hole in type 0B string theory

In the type 0B string theory, we discuss the role of tachyon (T) and fixed scalars (nu, lambda). The issue is to explain the difference between tachyo n and fixed scalars in the D5(+/-)-D1(+/-) black hole background. For this purpose, we perform the semiclassical calculation. Here one finds a mixing between (nu, lambda, T) and the other fields. Using the decoupling procedur e, one finds the linearized equation for the tachyon. From the potential an alysis, it turns out that nu plays a role of test field well, while the tac hyon induces an instability of Minkowski space vacuum. But the roles of nu and T are the same in the near-horizon geometry. Finally we discuss the sta bility problem.