A new kind of alternative gravity theory could explain measurements of the cosmic microwave background radiation. This could make the so-called MOND theory a formidable competitor to the dark matter theory.
The new MOND model, called relMOND, was developed last year by Constantinos Skordis employment Tom Złiciel The Czech Academy of Sciences in Prague. It was published last month in the Physics Journal physical review messages.
The main advantage of the new model is that it allows patterns to be measured in cosmic microwave background explains. This radiation is a kind of afterglow of the Big Bang that is found everywhere in the universe. Small differences in radiation temperature indicate how matter is distributed in the universe.
So far, MOND theory has failed to explain these patterns. As a result, the theory can’t really live up to the current description of the universe. The new model might change that; Although there are basic objections to be raised.
According to most cosmologists, most of the matter in the universe is made up of invisible particles that are different from all the particles we know. In particular, the rapid rotation of galaxies indicates the existence of these galaxies dark matter.
So some physicists believe that dark matter does not exist at all. They believe that the effects we see are actually due to a lack of understanding gravity. Therefore, according to them, we should adapt our theory of gravity, rather than create a new form of matter.
The most common alternative to dark matter is mouth theory, which means Modified Newtonian Dynamics. This theory of gravity made quite a stir in the 1980s. The formulas have proven to be able to explain the rotation of disk-shaped galaxies without dark matter.
However, the MOND theory has not been fully penetrated since then. With the exception of disk galaxies, the theory applies to very few phenomena. Because that’s the tricky part in developing an alternative theory of gravity: you have to be able to describe every phenomenon in the universe with it. With a few exceptions, standard theory can do this, provided you consider the existence of dark matter (and dark energy) accept.
For years, the MOND theory, among other things, had no explanation for the observations Gravity lensesThe phenomenon by which light is deflected by the gravitational pull of a galaxy. This changed at the beginning of this century with the development of so-called relativistic MOND models. But even with these models, the patterns in the cosmic microwave background cannot be reproduced.
In addition, the MOND theory was dealt a blow when gravitational waves first originated from them in 2017. Two neutron stars collide been measured. “One major relativistic MOND model predicted that gravitational waves would move slightly slower than the speed of light,” explains Margot Brewer, until recently an astronomer at the University of Groningen and the University of Amsterdam. But these measurements showed that the gravitational waves and light from the collision were equal in speed to fifteen decimal places.
The “Czech alternative” relMOND solves both problems in one fell swoop. Skordis and Złośnik’s model assumes two additional fields. One of the fields is similar to Higgs, which traverses the entire universe and gives particles their mass. The other field can be considered as a type of magnetic field. Together, the two injections generate an additional form of attraction.
In this way, the model explains the rotation of galaxies, the presence of gravitational lenses, the speed of gravitational waves and the patterns measured in the cosmic microwave background radiation. Fantastic result, says theoretical physicist hand visor from the University of Geneva. It is surprising that there is a theory of relativity similar to the MOND theory that works on the scale of galaxies as well as on the scale of cosmology. This is certainly an advance in the landscape of MOND theories,” he says.
Brouwer is also surprised. “I never thought the Mund model could explain the cosmic microwave background radiation,” she says. In standard theory, dark matter has a significant influence on the formation of patterns in this radiation. So a very complex model is needed to explain the same patterns without dark matter.
This is also the drawback of the new model: it is too complex. In physics, if the results are identical, then the simplest theorem is usually true. Currently, dark matter models are much less complex than relMOND.
Additionally, you might ask: Two additional fields together simulating the effects of dark matter, isn’t this a greater trick than entering dark matter itself? Skordis doesn’t think so. Every cosmological theory simply presents something unknown, as stated in an article on . news site physical review messages. But American cosmologist David Spiergel calls the new model “baroque” in the same article, accusing the Czechs of introducing a “complex form of dark matter.”
Another point of criticism is that the new model lacks a fundamental theoretical foundation. The formulas describe reality, but there is no deeper reason why these formulas do so. On the other hand, dark matter models are often based on physical laws of symmetry.
“I understand the lack of enthusiasm among theorists,” says Breuer. But the researchers also did not aim to develop a new theory. They just wanted to show that you can do without dark matter.
Moreover, such a basic theory can also be discovered later. alternative The theory of gravity by physicist Eric Verlind From the University of Amsterdam, for example, is based in part on the original MOND formulas from the 1980s, which had no theoretical basis.
Could the current relMOND model be an inspiration for it, too? Not immediately, Verlind thinks. “I think it’s interesting work,” he says. But I am trying to find a basic explanation for the MOND equations as well as the measurements of the cosmic microwave background radiation. Therefore, the most important questions I am working on have a precise theoretical basis.
For Visser, the lack of a theoretical basis is not the main obstacle. “What ultimately matters is whether the model matches all the observations,” he says. Could you also explain the observations of galaxy clusters, and the various measurements of The rate of expansion of the universe?“
According to Skordes, the new model can be tested with detailed measurements of gravitational waves, among other things, which can contain markers for the two additional fields.
Preferably this year Search by Brouwer It shows that astronomical observations are better explained using dark matter than with MOND theory. However, a “traditional” MOND model was used. In the same study, Ferlind’s theory was tested. It also lost to dark matter.
In general, dark matter still has an advantage over all alternatives at the moment. But as long as the dark particles are not detected, everything is still possible for Visser. “Personally, I think more people should work on new theories, because dark matter is one of the biggest unsolved problems in physics,” he says. Brouwer is also open to new approaches. “As long as dark matter is not found, we should try everything.”
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