Thank you for explaining more fully, and especially for the attached files (I almost missed them) illustrating transverse and longitudinal EM waves and the chart illustrating their suggested conceptual application to galactic rotation. IMO, this chart continues to perpetuate the misconception that galactic gravitation can be evaluated using simple Keplerian methods of approximation suitable for two-body gravitational systems.
In the terms put forward in the galactic rotation chart you supplied, I argue that gravitation is also 'interactive'. While Keplerian methods ignore the perturbances produces by orbitals other than the one being evaluated, gravitational interactions occur continuously among the massive stars and other objects within a galactic disk. That Kepler's methods chose to ignore them in the interest of simplicity (and specifically their inherent insignificance within the Sun dominated Solar system) - does not physically eliminate their effects. There are an estimated several hundred billion stars and other masses within the Galaxy that, inarguably, continuously gravitationally interact with the Solar system...
I think that the discrepancy between observed 'flat' galactic rotation and the expected Keplerian diminishment of rotational velocity at increasing radii can most simply be understood by complex gravitational interactions. Each planet orbiting the Sun can effectively be described as a two-body problem - in fact Kepler's equations do so by ignoring all gravitational effects imparted by any other planets, considering only two objects.
That works fine in the sparse Solar system, where the Sun contains 99.86% of total system mass. Here any perturbances produced by other relatively distant, low mass objects are not often significant. It is primarily the mass of the Sun, through its resulting gravitational effects, that determines the motions of each planet.
In contrast, from the perspective of each star in the disk of a spiral galaxy, for example, its motions are primarily determined by the vast 'sea' of gravitational effects produced by perhaps millions if not billions of nearby masses. There is no dominating single mass solely determining the motions of all 'orbital' bodies (supermassive black holes comprise a very small fraction of total system mass). Even the collective gravitation of a central bulge does not solely determine the motions of each disk object (some spiral galaxies do not even have a central bulge).
The complex dynamics of galactic motions simply cannot be solved with a two-body equation! There was no basis for presuming that Keplerian relations should apply to the vast distribution of masses, and vast distribution of resulting gravitational effects, within spiral galaxies.
I'm quite certain that if the Solar system's mass configuration and spatial distribution could simply be scaled up by a factor of ~200 billion that its rotational characteristics would generally comply with Keplerian expectations. However, discrete stars of nearly 200 billion solar masses cannot exist.
So, please consider that galaxies are not similar to planetary systems and cannot be expected to behave similarly. It seems to me that there is no justification for inventing some unidentified, undetectable form of mass to reconcile the discrepancy in their rotational characteristics - that should have been expected based on a casual evaluation of their disparate mass distributions!
In my essay, I've included a "Supplemental Information" section that, under the heading of "Describing Spiral Galaxy rotation without dark matter or modified gravity" lists several reports detailing more appropriate methods of evaluating the dynamics of galaxy rotation, generally representing spiral galaxy disks as - thin disks!
I do not see any need to look for any metaphysical explanations for the relatively flat rotation curves of spiral galaxies - as I understand, the physics are quite straightforward.
I can't really evaluate the possibility that longitudinal EM waves account for the observed discrepancy between the relations of rotational velocities and radial distances for planetary systems and spiral galaxies: I think that can be most simply explained by the greater proportions of mass at increasing radii in spiral galaxies. At any rate, if simplistic computational representations of planetary systems are applied to galaxies I suspect the results will be incorrect no matter what forces might be at work.
However, I am not a physicist - I can only to some extent assess information processes... Personally, I do not find it satisfying that the law of universal gravitation presumes some gravitational force that can be instantaneously imparted at great distances. I also do not find fulfillment in the idea that some curvature is metaphysically imparted to some abstract dimensional coordinates of the 'void' by local aggregations of potential mass-energy. I think that these approaches merely provide useful mathematical representations of unknown physical conditions that allow their evaluation. I think physics should be more physical than that...
The intent of my essay is to rectify past misinterpretations of observations that have profoundly shaped to future, and now present, of physics. I prefer to reduce requirements for imaginary elements whenever possible.
P.S. Frank, sorry if I misunderstood your comment.
Best wishes to you both!