A Generalized MOND Paradigm For Weak Gravitational Fields And Experimental Confirmation Of GR In Strong Gravitational Fields

This new (published) paper is a provocative generalization of the MOND paradigm, although still not a true "FundaMOND" in the sense of providing a rigorous, fundamental physical explanation for why the phenomenological MOND paradigm is observed in Nature. 

Notably, MOND addresses gravity in the extremely weak gravitational field regime.

The primary author, Robin Eappen, who is a doctoral student in astrophysics, is not well know. But Pavel Kroupa is one of the leading MOND proponents (and is perhaps a little less mainstream in his scientific positions and his manner of advocating for them, than either Mordehai Milgrom who devised MOND in 1983, his now deceased colleague in astrophysics, Jacob Bekenstein, or Stacey McGaugh, one of MOND's leading proponents in the current generation of astrophysicists).

Mass discrepancies in galaxies are empirically known to appear only below a characteristic acceleration scale a(0). 

Here we show that this behaviour is not limited to galaxies: it extends continuously across the full hierarchy of self-gravitating stellar systems, from gas-rich dwarfs and spirals to massive early-type galaxies, and further down to compact stellar clusters. 

We introduce the Milgromian dynamics (MOND) depth index DM, together with dynamical maturity index T = t(cross)/t(H), dynamical collisionality index T(1) = t(cross)/t(relax), with t(cross) being the crossing time, t(H) the Hubble time and t(relax) the median two-body relaxation time, and the MOND acceleration index A = a(bar)/a(0). 

We uncover a well-defined two-dimensional dividing surface in dynamical space. The "dark matter phenomenon" is found only in systems that are both in the deep-MOND regime (a(bar) < a(0)) and collisionless (t(relax) > t(H)), while high-acceleration, collisional systems (a(bar) > a(0), t(relax) << t(H)), including globular clusters and UCDs, show no evidence for a mass discrepancy. 

This clean dynamical separation defines a new, physically motivated classification scheme for stellar systems, unifying galaxies and clusters under one framework. The observed division emerges naturally within the MOND framework and provides a useful diagnostic for examining how different gravitational paradigms account for the origin of the mass discrepancy.

Robin Eappen, Pavel Kroupa, "The MOND Depth Index and Dynamical Maturity Clock: Toward a Universal Classification of Galaxies and Star Clusters" arXiv:2603.18135 (March 18, 2026) (published in 14(2) Galaxies 22 (2026)).

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In other gravity news, a series of three papers (one, two and three) look at gravitational wave observations of extremely strong gravitational fields created by black holes and/or neutron star binary systems to test General Relativity (GR) in this regime in various ways. 

All of this evidence is consistent with GR and more tightly constrains deviations from GR in this strong field context than prior tests of GR.