  Fractal grains have large surface area, which leads to more efficient
condensation. The special limit case where the volume-area ratio is constant
(corresponding to, e.g., a very rough grain surface or non-compacts aggregates)
is particularly interesting, as well as convenient, from a mathematical point
of view. If dust grains from AGB stars have `rough surfaces', it may have
important implications for our understanding of dust and wind formation in AGB
stars.
