Thin-shell wormholes with a double layer in quadratic F(R) gravity
  We present a family of spherically symmetric Lorentzian wormholes in quadratic F(R) gravity, with a thin shell of matter corresponding to the throat. At each side of the shell the geometry has a different constant value of the curvature scalar R. The junction conditions determine the equation of state between the pressure and energy density at the throat, where a double layer is also located. We analyze the stability of the configurations under perturbations preserving the spherical symmetry. In particular, we study thin-shell wormholes with mass and charge. We find that there exist values of the parameters for which stable static solutions are possible. 
Ernesto F. Eiroa, Griselda Figueroa-Aguirre
gr-qc