The "Swiss cheese" cosmological model has no extrinsic curvature   discontinuity: A comment on the paper by G.A. Baker, Jr. (astro-ph/0003152)
  Contrary to a claim, the Schwarzschild solution insertion in an expanding universe model, the so called "Swiss cheese" model, does not possess an extrinsic curvature discontinuity. We show that both the intrinsic metric and the extrinsic curvature are continuous, and point out the error that led to the claim. 
Charles C. Dyer, Chris Oliwa