Cosmological structure formation under MOND: A new numerical solver for Poisson's equation

We present a novel solver for an analogue to Poisson's equation in the framework of modified Newtonian dynamics (MOND). This equation is highly non-linear and hence standard codes based upon tree structures and/or fast Fourier transforms in general are not applicable; one needs to defer to multigrid relaxation techniques. After a detailed description of the necessary modifications to the cosmological N-body code amiga (formerly known as mlapm) we utilize the new code to revisit the issue of cosmic structure formation under MOND. We find that the proper (numerical) integration of a MONDian Poisson's equation has some noticeable effects on the final results when compared against simulations of the same kind but based upon rather ad hoc assumptions about the properties of the MONDian force field. Namely, we find that the large-scale structure evolution is faster in our revised MOND model leading to an even stronger clustering of galaxies, especially when compared to the standard Λ cold dark matter paradigm.