BLACK-HOLE GREYBODY FACTORS AND D-BRANE SPECTROSCOPY

Black holes do not Hawking-radiate strictly blackbody radiation due to well-known frequency-dependent greybody factors. These factors arise from frequency-dependent potential barriers outside the horizon which filter the initially blackbody spectrum emanating from the horizon. D- brane bound states, in a thermally excited state corresponding to near -extremal black holes, also do not emit blackbody radiation: The bound state radiation spectrum encodes the energy spectrum of its excitatio ns. We study a near-extremal five-dimensional black hole. We show that in a wide variety of circumstances including both neutral and charged emission, the effect of the greybody filter is to transform the black body radiation spectrum precisely into the bound state radiation spect rum. Implications of this result for the information puzzle in the con text of near-extremal black hole dynamics are discussed.