Absorption by extremal D3-branes

The absorption in the extremal D3-brane background is studied for a class ofmassless fields whose linear perturbations leave the ten-dimensional backgroundmetric unperturbed, as well as the minimally-coupled massive scalar. We findthat various fields have the same absorption probability as that of thedilaton-axion system, which is given exactly via the Mathieu equation. Weanalyze the features of the absorption cross-sections in terms of effectiveSchr\"odinger potentials, conjecture a general form of the dual effectivepotentials, and provide explicit numerical results for the whole energy range.As expected, all partial-wave absorption probabilities tend to zero (one) atlow (large) energies, and exhibit an oscillatory pattern as a function ofenergy. The equivalence of absorption probabilities for various modes hasimplications for the correlation functions on the field, including subleadingcontributions on the field-theory side. In particular, certain half-integer andinteger spin fields have identical absorption probabilities, thus providingevidence that the corresponding operator pairs on the field theory side belongto the same supermultiplets.Comment: Latex, 9 figures and 17 page