Nonlinear Structure Formation and "Apparent" Acceleration: an   Investigation
  We present an analytically solvable nonlinear model of structure formation in a Universe with only dust. The model is an LTB solution (of General Relativity) and structures are shells of different density. We show that the luminosity distance-redshift relation has significant corrections at low redshift when the density contrast becomes nonlinear. A minimal effect is a correction in apparent magnitudes of order 0.15. We discuss different possibilities that could further enhance this effect and mimick Dark Energy. 
Tirthabir Biswas (McGill U.), Reza Mansouri (Sharif U.), Alessio   Notari (McGill U.)