Thin shells around traversable wormholes
  Applying the Darmois-Israel thin shell formalism, we construct static and dynamic thin shells around traversable wormholes. Firstly, by applying the cut-and-paste technique we apply a linearized stability analysis to thin-shell wormholes in the presence of a generic cosmological constant. We find that for large positive values of the cosmological constant, i.e., the Schwarzschild-de Sitter solution, the regions of stability significantly increase relatively to the Schwarzschild case, analyzed by Poisson and Visser. Secondly, we construct static thin shell solutions by matching an interior wormhole solution to a vacuum exterior solution at a junction surface. In the spirit of minimizing the usage of exotic matter we analyze the domains in which the weak and null energy conditions are satisfied at the junction surface. The characteristics and several physical properties of the surface stresses are explored, namely, we determine regions where the sign of tangential surface pressure is positive and negative (surface tension). An equation governing the behavior of the radial pressure across the junction surface is deduced. Specific dimensions of the wormhole, namely, the throat radius and the junction interface radius, are found by taking into account the traversability conditions, and estimates for the traversal time and velocity are also determined. 
Francisco S.N. Lobo