It is interesting that in recent months two new theories have been proposed that run counter to conventional theories of dark matter that depend upon exotic baryonic matter.
One such paper on dark matter has arisen from M-Theory, suggesting that dark matter is not a particle in our spacetime but rather is in a hidden sector. B.S. Acharaya, et al. in The lightest visible-sector supersymmetric particle is likely to be unstable, suggests that what has been known as dark matter is not a particle with Standard Model quantum numbers, such as a WIMP, but rather is due to hidden sectors that interact with our visible sector via gravitational interactions only.
As quoted in PhysOrg,”In the proposed scenario, dark matter consists of particles in the hidden sector that communicate through a portal from the hidden sector to the visible sector, and in this way exert the gravitational effects that scientists have long observed.”
Also in PhysOrg, string theorist Erik Verlinde’s theory of emergent gravity is another outlier theory that runs counter to more traditional view of dark matter. As described in PhysOrg by the Netherlands based Delta Institute for Theoretical Physics, “Emergent gravity, as the new theory is called, predicts the exact same deviation of motions that is usually explained by invoking dark matter… In 2010, [Prof] Erik Verlinde surprised the world with a completely new theory of gravity. According to Verlinde, gravity is not a fundamental force of nature, but an emergent phenomenon.” In his paper, Verlinde states that, “the standard gravitational laws are modified on galactic and larger scales due to the displacement of dark energy by baryonic matter”. See https://arxiv.org/abs/1611.02269
The first test of Verlinde’s theory of emergent gravity has been found to agree with his predictions. As also mentioned in PhysOrg, “A team led by astronomer Margot Brouwer (Leiden Observatory, The Netherlands) has tested the new theory of theoretical physicist Erik Verlinde (University of Amsterdam) for the first time through the lensing effect of gravity. Brouwer and her team measured the distribution of gravity around more than 33,000 galaxies to put Verlinde’s prediction to the test. She concludes that Verlinde’s theory agrees well with the measured gravity distribution. The results have been accepted for publication in the British journal Monthly Notices of the Royal Astronomical Society.” See https://arxiv.org/abs/1612.03034
Yet these theories are not the first claimants to pose such alternatives to explaining dark matter without exotic baryonic matter. The first was Extended Heim Theory and its proponents Walter Dröscher and Jochem Hauser. Two years ago Walter Dröscher published Reality of Gravity-Like Fields? Part I: Recents experiments that challenge conventional physics and made a similar proposal about the nature of dark matter and its relationship to dark energy.
A year later in their book “Introduction to Physics, Astrophysics, and Cosmology of Gravity-Like Fields,” Dröscher and Hauser detailed a discussion in Secs. 9.10.4 Dark Energy and Dark Matter and 9.10.5 MOND Acceleration (pp. 366-374) where they talk about the polarization effect of baryonic (visible) matter on the distribution of dark energy. Such polarization is similar to one of the claims made by Verlinde.
Brouwer’s paper supporting Verlinde’s theory of emergent gravity found that “the lensing profile of apparent [dark matter] in [emergent gravity] is the same as that of the excess gravity in MOND…” The MOND (MOdified Newtonian Dynamics) hypothesis, proposed by Milgrom in 1983, correctly describes the dynamics of stars and gas within galaxies, without providing any physical argument. The numerical predictions of MOND are correct, but in the meantime dark matter has been discovered, so that the original intention of MOND is no longer valid. However, any valid theory of gravity must be able to match the MOND predictions, because they reproduce the observed data, including the most recent data by S. S. McGaugh.
A new paper in preparation by Hauser and Dröscher, Gravity Beyond Einstein? Part I: Physics and the trouble with experiments, provides a review of the latest experimental results in quantum physics and astrophysics, discussing their repercussions on the advanced physical theories that go beyond both SMs (standard models) of particle physics and cosmology.
In their paper they address a series of papers S. S. McGaugh, et al. that found corroboration of MOND. McGaugh found that the distribution of dark matter, characterized by its radial acceleration value (toward the galactic center) gdm, follows directly from the baryonic mass (stars and gas), reflecting a strong coupling between dark and baryonic mass, but is independent of dark halo models.
Hauser and Dröscher’s paper states,
Their (McGaugh, et al.) data are based on the Spitzer Photometry and Accurate Rotation Curves (SPARC) database of 175 galaxies of widely different type and show only very little scatter. That is, the connection between baryonic mass and rotation velocity is pronounced and no adjustable parameters were used. Indeed, the one-to-one correspondence between the acceleration resulting from the baryonic mass, gbar, and the observed acceleration gobs, may be considered as a hint that the baryons only are the source of the gravitational potential. In this case, the laws of dynamics need to be altered, replacing the dark matter concept. However, according to EHT, this is not the case, Newtonian dynamics prevails, but, instead, dark matter particles, which are of negative mass, do reside in the so-called dual space (imaginary time coordinate, see above) rather than in four-dimensional spacetime. Only their gravitational potential is experienced in our spacetime, but there are no dark matter particles present.
They continue, “The deviation from Newton’s law of gravitation as observed by McGaugh et al. may be explained by the polarization effect on the dark energy distribution by the high matter density within galaxies …”
So in one statement, Hauser and Dröscher suggest not only a mechanism for MOND, but also give an alternative explanation to Verlinde’s proposal that baryonic matter impacts the displacement of dark energy (see previous blog postings in this website on the relationship with dark matter according to EHT) and that, similar to B.S. Acharaya, dark matter interactions with our spacetime occur only through gravitational interactions. The question therefore remains: what is the gravitational phenomenon responsible for the MOND acceleration as measured by McGaugh? For that insight the discussion will be resumed in their subsequent companion paper.
Here is the conclusion of their paper (which addresses much more than reported here):
Weighing the experimental evidence presented, we think that a paradigm shift in our understanding of the Cosmos is mandatory, paving the road to a different age (as pointed out in Chap. 11 of [their book]), marked by an overthrow of the present Weltbild of physics, in particular, concerning the nature of matter as well as physical reality.
Before the next collider generation actually is being built, the relatively simple gravitational experiments discussed above should be repeated at several laboratories applying much more sophisticated equipment. If the results of these experiments can be confirmed, then it is evident that Nature has chosen a different path than utilizing extra dimensions.
The physical alternative proposed to the extension of spatial dimensions could be the extension of the system of numbers, first suspected by Pythagoras and extensively discussed by Sir Roger Penrose in his comprehensive œvre, e.g. [“The Large, theSmall and the Human Mind“] etc. As will be presented in [their upcoming paper] this approach should be leading to both different types of symmetries (groups) and matter.
In 1946, the U.S. government funded a comprehensive feasibility report, prior to any hardware activities, termed Preliminary Design of an Experimental World-Circling Spaceship by F. H. Clauser et al., Douglas Aircraft Company that marked the beginning of the era of spaceflight. Given the current theoretical and experimental hints, we seem to be in a similar situation today regarding the preliminary design of a gravitational-field propulsion device. Whether the success story will turn out to be similar cannot be decided at the moment. On the other hand, it is evident that for a risk averse society the chance of success is close to zero.
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