Dark negative matter floods the Universe (probably)

This research has been already mentioned on Steem. But I want to present it in more details because it is a really cool idea and seems to solve many problems at once.

Dr. Farnes from the University of Oxford offered a unified explanation for the effects of dark energy and dark matter - negative mass particles distributed across the Universe and constantly created from vacuum.

Dark energy is what is attributed to be responsible for the expansion of our Universe. Vacuum has a non-zero energy density, which causes spacetime to expand. This density is represented in the equations with the cosmological constant "lambda" (Λ).

Dark matter is postulated to explain the speed of rotation of stars in galaxies. At the edge of galaxies, stars spin at a much faster rate than General Relativity predicts. In fact, the rotational speed of all stars in the galaxy is more or less the same, although it should fall with the distance from the center. This can be explained if we assume the presence in the galaxy of so-called dark matter - a substance that does not emit light and interacts with the rest of the matter only gravitationally. Several variants of “dark” particles were proposed, but so far none of them have been found.

Together, dark energy and dark matter form the ΛCDM model and are responsible for 95% of the Universe.

Dr. Farnes proposes that both effects can be explained by the presence of a large amount of negative mass in the Universe. Negative particles repel each other, which leads to galaxies flying away from each other, i. e. to the expansion of the Universe. For the same reason, they are not combined into complex structures such as atoms, which are necessary to emit light. So they remain "dark." On the other hand, negative particles are attracted to positive ones, which leads to the fact that they accumulate around galaxies and speed up stars in their periphery.

I will give the key points of his work.

As the universe expands, the negative mass density should fall, and the expansion should slow down. To explain the observed accelerated expansion, Farnes postulates the emission of negative mass - a continuous creation of new negative particles from vacuum. At a constant frequency of particle production, we obtain an analog of the cosmological constant Λ. However, this model assumes that the frequency can be time and location dependent. This could explain the discrepancies in measuring the Hubble constant and galaxies with different amount of dark matter.

Strange as it may seem, negative mass is an analog of a negative cosmological constant Λ. On the one hand, this is logical because the negative mass is equivalent to the negative vacuum energy. But on the other hand, a negative Λ means compression of the Universe and not expansion! In the current model, where we observe the expansion of the Universe, Λ is considered positive.

However, solving the Friedmann equations for the universe with the dominant negative mass gives a cyclic universe with negative Λ, variable Hubble parameter and negative curvature. At first, the Universe expands, but at some point expansion gives way to compression and it collapses back. The smaller Λ (in absolute value), the longer the lifetime of the Universe. For example, if Λ is equal in magnitude to the current measured value (but negative in sign), one cycle will be 105 billion years, so we might be simply still in the young expanding phase.

Another interesting fact is that the only possible solution in this case is a spacetime with negative curvature, and this is exactly the famous anti-de Sitter space, which is very much loved in string theory and other quantum gravity theories. In anti-de Sitter space, there is a so-called AdS/CFT correspondence, which allows connecting gravity to the quantum field theory. Due to that, such a space is a good toy model for testing various theories of quantum gravity, but it has always remained a mystery how to apply these models to our real Universe. But If our Universe is really an anti-de Sitter universe, then "theories of everything" can take on a new life.

Farnes conducted a computer simulation of a galaxy of 50 thousand particles (5 thousand positive and 45 thousand negative with a total mass ratio of 1 to 3 in favor of the negative one) and confirmed, firstly, that the negative mass accumulates around a positive one, creating a cloud of negative mass of several radii of the galaxy, and secondly, that this in fact leads the rotational speed of positive particles not to fall with the radius. By the way, the explanation of this phenomenon with the help of a negative Λ has already been proposed but was rejected because of the observation of the redshift in supernovae, which hinted at a positive Λ.

Another remarkable result is that in this case the density of negative dark matter is approximately uniform throughout the galaxy, which agrees well with the observations, but so far has not corresponded to any model with positive dark matter. Positive matter, whatever it is, tend to accumulate in the center of the galaxy, while negative matter, due to the repulsive forces, is distributed more evenly.

In addition, another simulation was conducted with an equal number (25 thousand) of positive and negative particles (and an equal mass) in order to check whether complex structures such as galaxies would form in such a universe. The simulation showed that they indeed would, and the modeled universe, which at the beginning was uniform, eventually became split into clusters and voids. The Python simulation code is available on Github.

Another important point is that a runaway motion (i. e. infinitely accelerated dipoles of particles of positive and negative mass, which is predicted by the theory) was not found in the model. Probably, external forces quickly destroy a pseudo-equilibrium state of such dipoles, so even if they occur, it is very rare. By the way, ultra-high energy cosmic rays and so-called Oh-my-God particles can be a manifestation of this phenomenon.

But what about the observations? After all, they suggest that we have a positive Λ and a flat universe with zero curvature. The fact is that all the models explaining the observations (in particular, a redshift of supernovae and cosmic microwave background radiation) were based on the assumption that all the mass is positive. And to reconsider them in the view of the possibility of negative mass is still an open task. By the way, in one of the papers on supernovae, it was already shown that if Λ is set to zero, then the equations converge only if the total mass of the Universe is negative.

In addition, the author cites about a dozen references to other works in which, one way or another, the negative mass follows from observations. For example, the measured mass of one of the groups of galaxies decreases with the addition of new outer layers.

And finally, we can say that negative energy can be associated either with matter or with vacuum. This is a matter of interpretation. Negative particles can be considered as the quantized energy of spacetime itself. By the way, this can solve the cosmological constant problem. Its value, calculated on the basis of quantum theory, is at least 120 orders of magnitude greater than the observed value. According to Lee Smolin, this is the worst prediction ever made by a scientific theory. But with the appearance of negative mass, the vacuum energy density now can have any value, depending on how much it compensates for the positive one.

All this seems to be way too good to be true. I would appreciate any comments pointing to the potential weaknesses of this theory.

My original post in Russian.

References:

Farnes, J. S. (2018). A unifying theory of dark energy and dark matter: Negative masses and matter creation within a modified ΛCDM framework. Astronomy & Astrophysics, 620, A92.

Whitehouse, S. B., & Kraniotis, G. V. (1999). A possible explanation of Galactic Velocity Rotation Curves in terms of a Cosmological Constant. arXiv preprint astro-ph/9911485.

Riess, A. G., Filippenko, A. V., Challis, P., Clocchiatti, A., Diercks, A., Garnavich, P. M., ... & Leibundgut, B. R. U. N. O. (1998). Observational evidence from supernovae for an accelerating universe and a cosmological constant. The Astronomical Journal, 116(3), 1009.

O’Sullivan, E., Vrtilek, J. M., Harris, D. E., & Ponman, T. J. (2007). On the anomalous temperature distribution of the intergalactic medium in the NGC 3411 group of galaxies. The Astrophysical Journal, 658(1), 299.

Smolin L. (2007). The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next. HMH, 2007.

Picture source: Pixabay.