Tuesday, September 12, 2017

Deur Considers Dark Energy As A Form Of Gravitational Shielding

Completing The Proof Of Concept

Deur's basic thesis is that dark matter and perhaps dark energy as well can arise from the self-interaction of gravitons, using the analogy of quantum chromodynamics (QCD) as a model and starting with a static/high temperature scalar case as a first approximation. He claims that this is consistent with general relativity, but given canonical results in the field, I suspect that his theory is a subtle modification of GR.

Earlier papers worked out, to a back of napkin level of precision, that his hypothesis can explain dark matter in both galaxies and galactic clusters, and can explain why elliptical galaxies that are less spherical appear to have more dark matter. The self-interaction effects cancel out in spherically symmetric systems and grow stronger as the total mass of the system grows.

His latest pre-print, for which the abstract and citation are below, makes a similar back of napkin precision estimate of the dark energy effects of his hypothesis to see if it can be fit to the cosmology data in the absence of dark energy entirely, and he concludes that it can, with dark energy effects initially being minimal, but growing as large scale structure gives rise to dark matter effects that screen gravitons from exiting those structures.

Taken together, his several papers on the topic argue that his theory can, to back of napkin precision, describe all significant dark matter and dark energy effects by correctly modeling the self-interaction of the graviton in a way that other dark matter and dark energy theorists have neglected.

If correct, the only beyond the Standard Model particle that needs to exist is the graviton, and a graviton based theory can dispense with the cosmological constant, at least in principle. In short, "core theory" would pretty much completely describe all observed phenomena except short range, extremely strong gravitational field quantum gravity phenomena, and the right path to studying that would be established. This could all play out on the Standard Model's flat Minkowski space background that recognizes the existing of special relativity but does not have a curved space-time in which the mathematics of quantum mechanics doesn't work.

For what it is worth, I think he is right, even though he is currently a lone voice in the wilderness without the time, funding, or community of colleagues who buys into his hypothesis to rigorously and thoroughly implement this paradigm in a way that is sufficient to achieve a scholarly consensus in the field. Particle dark matter theories are in trouble. There are a few modified gravity theories that rise to the occasion, but none as elegant, simple and as broad in their domains of applicability as this one. He hasn't worked out a way to get all of the constants from first principles, but the vision is there and it is a powerful one.

Gone are the epicycles. Gone are unobservable substances that in the mainstream lambda CDM model account for something like 93%-95% of the stuff in the universe. Vexing aspects of ordinary GR, like the inability to localize gravitational energy and the seeming irrelevance of its self-interactions are gone. The "coincidence problem" is solved. Fundamentally, one coupling constant is sufficient to describe it all, even if it is easier to empirically estimate some of the constants derived from it in the meantime. We have a complete set of fundamental particles (without ruling out the possibility that they might derive from something even more fundamental). We have strong analogies between QCD and GR, some of which have long been observed, to guide us. We have a theory that is corroborated by original predictions that empirical evidence supports that aren't easily explained by other theories.

It doesn't address matter-antimatter asymmetry (for which I have identified another paper with a good explanation). It isn't clear how it interacts with "inflation" theories. But, it would be a huge, unifying step forward in gravity theory, the greatest since general relativity was devised a century ago.

There is so much to like about this approach that it deserves dramatically more resources than it has received to develop further, because it is the most promising avenue to a fundamental break through in physics in existence today. If it pans out, it is work far more significant than typical Nobel prize material.

The Pre-Print
Numerical calculations have shown that the increase of binding energy in massive systems due to gravity's self-interaction can account for galaxy and cluster dynamics without dark matter. Such approach is consistent with General Relativity and the Standard Model of particle physics. The increased binding implies an effective weakening of gravity outside the bound system. In this article, this suppression is modeled in the Universe's evolution equations and its consequence for dark energy is explored. Observations are well reproduced without need for dark energy. The cosmic coincidence appears naturally and the problem of having a de Sitter Universe as the final state of the Universe is eliminated.

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