  A new approach to vacuum decay in quantum field theory, based on a simple
variational formulation in field space using a tunneling potential, is ideally
suited to study the effects of gravity on such decays. The method allows to
prove in new and simple ways many results, among others, that gravitational
corrections tend to make Minkowski or Anti de Sitter false vacua more stable
semiclassically or that higher barriers increase vacuum lifetime. The approach
also offers a very clean picture of gravitational quenching of vacuum decay and
its parametric dependence on the features of a potential and allows to study
the BPS domain-walls between vacua in critical cases. Special attention is
devoted to supersymmetric potentials and to the discussion of near-critical
vacuum decays, for which it is shown how the new method can be usefully applied
beyond the thin-wall approximation.
