Cosmological Structure Formation under MOND: a new numerical solver for Poisson's equation

TL;DR

This paper introduces a new multi-grid solver for the non-linear Poisson's equation in MOND, enabling more accurate simulations of cosmic structure formation that show faster evolution and stronger galaxy clustering than previous models.

Contribution

The authors develop and implement a novel multi-grid solver for MOND's non-linear Poisson's equation within a cosmological N-body code, improving the accuracy of structure formation simulations.

Findings

Faster large-scale structure evolution in MOND simulations.

Stronger galaxy clustering compared to previous MOND models.

Differences highlighted against standard LCDM paradigm.

Abstract

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 FFT's in general are not applicable; one needs to defer to multi-grid 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 noticable 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 LCDM paradigm.