A Fast Route to Non-Linear Clustering Statistics in Modified Gravity   Theories
  We propose a simple and computationally fast method for performing N-body simulations for a large class of modified gravity theories with a screening mechanism such as chameleons, symmetrons and galileons. By combining the linear Klein-Gordon equation with a screening factor, calculated from analytical solutions of spherical symmetric configurations, we obtain a modified field equation whose solution is exact in the linear regime while at the same time takes screening into account on non-linear scales. The resulting modified field equation remains linear and can be solved just as quickly as the Poisson equation without any of the convergence problems that can arise when solving the full equation. We test our method with N-body simulations and find that it compares remarkably well with full simulations well into the non-linear regime. 
Hans A. Winther, Pedro G. Ferreira
astro-ph.CO gr-qc