Intermediate scalars and the effective string model of black holes

We consider five-dimensional black holes modeled by D-strings bound to D5-branes, with momentum along the D-strings, We study the greybody factors for the non-minimally coupled scalars which originate from the gravitons and R-R antisymmetric tensor particles polarized along the 5-brane, with one index along the string and the other transverse to the string. These scalars, which we call intermediate, couple to the black holes differently from the minimal and the fixed scalars which were studied previously, Analysis of their fluctuations around the black hole reveals a surprising mixing between these NS-NS and R-R scalars. We disentangle this mixing and obtain two decoupled scaler equations. These equations have some new features, and we are able to calculate the greybody factors only in certain limits. The results agree with corresponding calculations in the effective string model provided one of the intermediate scalars couples to an operator of dimension (1,2), while the other to an operator of dimension (2,1). Thus, the intermediate scalars are sensitive probes of the chiral operators in the effective string action. (C) 1997 Elsevier Science B.V. PACS: 04.70.Dy; 04.65.+e; 11.25.-w; 11.25.Pm.