We derive the low energy absorption cross section of minimal scalars for a
very generic class of geometries, that includes, among others, black holes,
strings, p-branes, as well as intersecting brane configurations. The scalar
field can be absorbed across a regular surface (a horizon) of finite area, or
across a zero area throat, which may be singular or regular. Then we focus on
some particular cases and compare with the results obtained using microscopic
models at weak coupling. Exact agreement is found for the absorption by the
non-degenerate ground state of effective strings. For geometries where the
throat is singular, we show that absorption through the stretched horizon
yields correct results for degenerate states. For non-degenerate (ground)
states we introduce a stretched throat, and show that it accounts for the
correct dependence on frequency, charges, and moduli for the absorption by
ground states of BPS fundamental strings. It is also shown to lead to the
correct dependence on frequency for extremal D-branes.Comment: 20 pages, LaTe