Testing modified gravity using a marked correlation function.

In theories of modified gravity with the chameleon screening mechanism, the strength of the fifth forcedepends on environment. This induces an environment dependence of structure formation, which differs from Λ- cold-dark-matter(ΛCDM). We show that these differences could be captured by the marked correlation function. With the galaxy correlation functionsand number densitiescalibrated to match between f(R) and ΛCDM models in simulations, we show that the marked correlation functionsby using either the local galaxy number densityor halo mass as the marks encode extra information, which can be used to test these theories. We discuss possible applications of these statistics in observations.