The p-Laplacian as a framework for generalizing Newtonian gravity and Milgromian gravitation

¹ Universität Bonn, 53115 Bonn, Germany
² Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, Nussallee 14-16, 53115 Bonn, Germany
³ Astronomical Institute, Charles University, V Holesovickach 2, 18000 Praha, Czech Republic
⁴ School of Astronomy and Space Science, Nanjing University, Nanjing 210093, People's Republic of China
⁵ Key Laboratory of Modern Astronomy and Astrophysics (Nanjing University), Ministry of Education, Nanjing 210093, People's Republic of China

^⋆ Corresponding author: s6dvsche@uni-bonn.de

Received: 27 March 2025
Accepted: 21 April 2025

Abstract

Context. The radial acceleration relation (RAR) follows from Milgromian gravitation (MoND) and velocity dispersion data of many dwarf spheroidal galaxies (dSphs) and galaxy clusters have been reported to be in tension with it.

Aims. We consider the generalized Poisson equation (GPE), expressed in terms of the p-Laplacian, which has been applied in electrodynamics, and investigate whether it can address these tensions.

Methods. From the GPE we derive a generalized RAR characterized by the p parameter from the p-Laplacian and a velocity dispersion formula for a Plummer model. We apply these models to Milky Way and Andromeda dSphs and HIFLUGS galaxy clusters and derive a p parameter for each dSph and galaxy cluster. We explore a relation of p to the mass density of the bound system, and alternatively a relation of p to the external field predicted from Newtonian gravity

Results. This ansatz allows the deviations of dSphs and galaxy clusters from the RAR without the need of introducing dark matter. Data points deviate from the Milgromian case, p = 3, with up to 5σ-confidence. Also, we find the model predicts velocity dispersions, each of which lies in the 1σ-range of their corresponding data point allowing the velocity dispersion to be predicted for early-type dwarf satellite galaxies from their baryonic density. The functional relation between the mass density of the bound system and p suggests p to increase with decreasing density. We find for the critical cosmological density p(ρ_crit) = 12.27±0.39. This implies significantly different behaviour of gravitation on cosmological scales. Alternatively, the functional relation between p and the external Newtonian gravitational field suggests p to decrease with increasing field strength.

Conclusions. The GPE fits the RAR data of dSphs and galaxy clusters, reproduces the velocity dispersions of the dSphs, gives a prediction for the velocity dispersion of galaxy clusters from their baryonic density and may explain the non-linear behaviour of galaxies in regions beyond the Newtonian regime.