  The absorption in the extremal D3-brane background is studied for a class of
massless fields whose linear perturbations leave the ten-dimensional background
metric unperturbed, as well as the minimally-coupled massive scalar. We find
that various fields have the same absorption probability as that of the
dilaton-axion system, which is given exactly via the Mathieu equation. We
analyze the features of the absorption cross-sections in terms of effective
Schr\"odinger potentials, conjecture a general form of the dual effective
potentials, and provide explicit numerical results for the whole energy range.
As expected, all partial-wave absorption probabilities tend to zero (one) at
low (large) energies, and exhibit an oscillatory pattern as a function of
energy. The equivalence of absorption probabilities for various modes has
implications for the correlation functions on the field, including subleading
contributions on the field-theory side. In particular, certain half-integer and
integer spin fields have identical absorption probabilities, thus providing
evidence that the corresponding operator pairs on the field theory side belong
to the same supermultiplets.
