Ordinary and Dilatonic Domain Walls: Solutions and Induced Space-Times

Recent developments in unifying treatment of domain wall configurations and their global space-time structure is presented. Domain walls between vacua of non-equal cosmological constant fall in three classes depending on the value of their energy density $\sigma$: (i) extreme walls with $\sigma=\sigma_{ext}$ are planar, static walls corresponding to the supersymmetric configurations, (ii) non-extreme walls with $\sigma>\sigma_{ext}$ are expanding bubbles with two insides, (iii) ultra-extreme walls with $\sigma<\sigma_{ext}$ are bubbles of false vacuum decay. As a prototype exhibiting all three types of configurations vacuum walls between Minkowski and anti-deSitter vacua are discussed. Space-times associated with these walls exhibit non-trivial causal structure closely related to the one of the corresponding extreme and non-extreme charged black holes, however, without singularities. Recently discovered extreme dilatonic walls, pertinent to string theory, are also addressed. They are static, planar domain walls with metric in the string frame being {\it flat} everywhere. Intriguing similarities between the global space-time of dilatonic walls and that of charged dilatonic black holes are pointed out.