  A recently proposed approach to the construction of the Vaidya metric in
double-null coordinates for generic mass functions is extended to the
$n$-dimensional $(n>2)$ case and to allow the inclusion of a cosmological
constant. The approach is based on a qualitative study of the null-geodesics,
allowing the description of light-cones and revealing many features of the
underlying causal structure. Possible applications are illustrated by explicit
examples. Some new exact solutions are also presented and discussed. The
results presented here can simplify considerably the study of spherically
symmetric gravitational collapse and mass accretion in arbitrary dimensions.

General Relativity and Quantum Cosmology