ROLE OF FIXED SCALARS IN SCATTERING OFF A 5D BLACK-HOLE - ART. NO. 104006

We discuss the role of fixed scalars (nu,lambda) in scattering off a f ive-dimensional black hole. The issue is to explain the disagreement o f the greybody factor for lambda between the semiclassical and effecti ve string calculations. In the effective string approach, this is rela ted to the operators with dimension (3,1) and (1,3). In the semiclassi cal calculation this originates from a complicated mixing between lamb da and other fields. Hence it may depend on the decoupling procedure. It is shown that lambda depends on gauge choices such as the harmonic, dilaton gauges, and the Krasnitz-Klebanov setting for h(mu nu). It tu rns out that nu plays a role of test field well, while the role of lam bda is obscure. [S0556-2821(98)03920-4].