The role of fixed scalars in scattering off a 5D black hole

We discuss the role of fixed scalars($\nu,\lambda$) in scattering off a five-dimensional balck hole. The issue is to explain the disagreement of the greybody factor for $\lambda$ between the semiclassical and effective string calculations. In the effective string approach, this is related to the operators with dimension (3,1) and (1,3). On the semiclassical calculation, this originates from a complicated mixing between $\lambda$ and other fields. Hence it may depend on the decoupling procedure. It is shown that $\lambda$ depends on the gauge choices such as the harmonic, dilaton gauges, and the Krasnitz-Klebanov setting for $h_{\mu\nu}$. It turns out that $\nu$ plays a role of test field well, while the role of $\lambda$ is obscure.