Formal iteration scheme for scalar fields in some spherically symmetric spaces

The characteristic initial-value problem for the scalar wave equation in some spherically symmetrical geometries, including Reissner-Nordstrom exterior geometry, is considered. A modified Picard iteration making explicit use of the (known) static solutions yields a formula for the fields. The formulas extend in to the outer horizon, and from them are obtained useful expressions for the reflection and transmission amplitudes in terms of the static solutions. (author)