In the context of scalar tensor theories for gravity, there is a universally adopted hypothesis when running $N$-body simulations that time derivatives in the equation of motion for the scalar field are negligible. In this work we propose to test this assumption for one specific scalar-tensor model with a gravity screening mechanism: the symmetron. To this end, we implemented the necessary modifications to include the nonstatic terms in the $N$-body code Ramses. We present test cases and results from cosmological simulations. Our main finding when comparing static vs nonstatic simulations is that the global power spectrum is only slightly modified when taking into account the inclusion of nonstatic terms. On the contrary, we find that the calculation of the local power spectrum gives different measurements. Such results imply one must be careful when assuming the quasistatic approximation when investigating the environmental effects of modified gravity and screening mechanisms in structure formation of halos and voids distributions.

• Received 21 December 2013

DOI:https://doi.org/10.1103/PhysRevD.89.084023