A Modified Gravity against Dark Matter

[Floyd_13]

TL;DR Summary

Theories of modified gravity aiming to dispense dark matter

I am looking for examples of Modified Gravity theories that have been developed with the aim of dispensing dark matter, besides Milgrom's [MOND][1], Bekenstein's [TeVeS][2], and the recent relativistic version of MOND ([RMOND][3]) by Skordis and Zlosnik.

Are there any other examples of similar attempts in the recent history of physics? Or is there a good source summarizing and discussing these kind of attempts?

Thanks! [1]: https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics
[2]: https://en.wikipedia.org/wiki/Tensor–vector–scalar_gravity
[3]: https://arxiv.org/abs/2007.00082

 

[Structure seeker]

Notable other MOND theories are BIMOND, by Milgrom himself, and the not fully understood and hard to compute SI gravity by Alexandre Deur, see for instance http://dispatchesfromturtleisland.blogspot.com/p/deurs-work-on-gravity-and-related.html?m=1
The interesting thing is that Deur's theory, although his calculations are not yet very well understood, does not really modify gravity but assumes the graviton as a self-interacting particle. The self interaction ensures that gravitons arise also from gravitons and stay 'near' the bulk of gravitons as second order (thus weak) effect, leading to MOND for galaxies whose mass is sort of distributed as a disk (2D). This leads to probably better predictions for the regions where MOND is less succesful, especially for clusters.

Also there is a framework called Einstein-Aether theories, of which RMOND is an example. In fact BIMOND is also more of a framework of theories than a theory.

 

[Structure seeker]

Note that there is not a general aim to "dispense of" dark matter. The aim is to make models that predict reality instead of only explaining it. Dark matter lacks predictive power since it cannot be observed and has an unknown particle type if it even exists. IMO there's lots of talk about dark matter that would be better dispensed of, but that's just a side effect if MOND succeeds.

 

[Structure seeker]

https://arxiv.org/abs/2110.06936 gives a review of many experimental types of data comparing MOND to dark matter. I'm not sure if it goes deep for specific MOND theories though.

 

[ohwilleke]

John Moffat has proposed several similar modified gravity theories sometimes given the acronym "MOG". These include Moffat's STVG theory, and MSTG which is another iteration of Moffat's gravity modification theory work.

There are a variety of specific changes to classical Einstein gravity that have been proposed. For example, f(R) gravity, and gravitational theories that treat torsion differently. The Palatini f(R) gravity and Eddington-inspired-Born-Infeld (EiBI) are theories that modify General Relativity in ways that tweak add and/or modify Einstein's field equations in ways that make plausible hypotheses to adjust them in a theoretically consistent manner and do lead to some explanation of dark matter phenomena, but very well, as this paper notes. Palatini f(R) gravity replaces the Ricci tensor and scalar with a function that has higher order terms not present in Einstein's field equations. The Eddington-inspired-Born-Infeld theory starts with the "Lagrangian of GR, with an effective cosmological constant Λ = 𝜆−1 𝜖 , and with additional added quadratic curvature corrections. Essentially, it is a particular 𝑓 (𝑅) case that fits the Palatini 𝑓 (𝑅) case that was presented in the previous section, together with a squared Ricci tensor term[.]" See also f(R,Lm), f(T), f(R,T), f(Q) and "Energy-Momentum Squared Gravity" gravity modifications (many of which are discussed here), quadratic gravity, massive gravity theories, and a "type-II minimally modified gravity theory called VCDM." Some of these replicated dark matter with the right parameters, some don't, and I couldn't tell you precisely which ones do and do not.

A number of proposals have been made that fall under the rubric of "conformal gravity".

Verlinde's "Emergent Gravity" and kindred theories are notable. It has been contradicted in its original version. See Federico Lelli, Stacy S. McGaugh, and James M. Schombert "Testing Verlinde's Emergent Gravity with the Radial Acceleration Relation"(February 14, 2017). But, variants of its that work better have been proposed. See also Jungjai Lee, Hyun Seok Yang, "Dark Energy and Dark Matter in Emergent Gravity" arXiv:1709.04914 (September 14, 2017, last revised November 1, 2022 ) and 81(9) Journal of the Korean Physical Society 910-920 (2022).

Lee Smolin has a new paper [as of 2018] on quantum gravity including the proposition that modified gravity rules giving rise to the effects summarized in the MOND toy-model should arise in Loop Quantum Gravity theories based upon a couple of different arguments, neither of which are rock solid, but both of which are basically plausible. Sabine Hossenfelder discusses the paper and related issues in a recent post at her blog, and also wrote an article for the general public on a hybrid of a gravity modification and dark matter proposal.

There is a review with additional speculation about a person theory of modified gravity in Eugene Oks, "Brief Review of Recent Advances in Understanding Dark Matter and Dark Energy" arXiv:2111.00363 (October 30, 2021) (93 New Astronomy Reviews 101632) DOI: 10.1016/j.newar.2021.101632

Another effort, that like Deur, tries to use GR effects to explain dark matter is W.M. Stuckey, Timothy McDevitt, A.K. Sten, Michael Silberstein, "The Missing Mass Problem as a Manifestation of GR Contextuality" arXiv:1509.09288 and W.M. Stuckey, Timothy McDevitt, A.K. Sten, Michael Silberstein, "End of a Dark Age?" arXiv:1605.09229.

Yet another gravity modification theory to explain dark matter phenomena is called RGGR (Renormalization Group corrected General Relativity), developed by D.C. Rodrigues and others in 2010, that modifies General Relativity by tweaking the gravitational coupling constant in a manner analogous to renormalization of coupling constants in the Standard Model. RGGR also has more parameters than MOND, but claims to produce tighter fits to galactic rotation curves than leading gravity modfication alternatives to dark matter like MOND and SVTG.

(Note that parts of this post quote previous blog posts that I have written without attribution.)

 

[kodama]

Refracted Gravity, arXiv:2301.07115