The Standard Cosmic Model, which has become a reference over the past century, can be relegated to the background. A study conducted by an international team led by Moritz Halspur from the University of Bonn in Germany, published on February 4, 2022 in Astrophysics messages Ask about this model Eye cold lambda dark matter (LCDM, for “lambda – Cold Dark Matter.” By comparing the theoretical assertions made by LCDM with analysis of observational data from galaxies scattered in the universe, astrophysicists discovered “irregularities.” In fact, a large portion of galactic systems would have the shapes of flat disks , with a prominent center, which is in contrast to the aforementioned model, which predicted a small percentage of these formations.

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© NASA

A representation of the timeline of the creation of the universe, from the Big Bang to today.

Dark matter is the cause of uncertainty?

The LCDM model is a theoretical model that emerged in the 1990s and achieved rapid success in the astrophysics community, sometimes renamed the “Standard Big Bang Model”. With LCDM, galaxies sink into halos of dark matter, the latter making up 27% of the universe, exceeding the presence of classical matter called baryonic in the universe, estimated at 5%. The gravitational effect exerted by dark matter will in fact cause galaxies, of varying sizes, to merge, thickening the system. ” The main point of our study is the observation of a large number of galaxies whose consistency turns out to be more brittle than suggested by the LCDM model. ‘,” researcher Moritz Halsbohr explains to Science and Life.

Galactic mergers of the Standard Cosmological Model will also affect what physicists call “angular momentum” or “angular momentum”. Angular momentum is a vector quantity that determines the amount of motion of a mass according to its velocity. With regard to galaxies, the angular moment makes it possible to maintain the shape of the disk thanks to the speed of rotation of matter around the galactic nucleus. However, in the LCDM model, there are many galactic mergers that may disturb the angular momentum. From the gravitational interaction between the two systems, a phenomenon called Chandrasekhar friction occurs: the moving matter will gradually slow down, causing the circular dynamics to distort.

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© ESA, NASA

These two galaxies, nicknamed “The Mice”, are currently in the process of merging and should transform into a more massive galaxy at the end of the process.

Alternative: the world

Faced with observing many galaxies with relatively thin disks, Halspur’s team realized this The LCDM model may not work. According to the postdoc: It is clear that we need a new cosmic paradigm. The LCDM has proven to be suboptimal. We have to get rid of the variable that dark matter can represent, be it hot or cold. It would also be necessary to rethink some of the laws of gravity. In this, the theory showed promise in the face of the infinite expanse that the universe represents: the MOND . model “.

© NASA Plank

The cosmic microwave background as imaged by the Planck satellite, which makes it possible to distinguish hot and cold regions of the universe.

Born in 1983 from the mind of Israeli astrophysicist Mordihai Milgrom, Mond (l Modified Newtonian Dynamics“Modified Newtonian dynamics”) is A real alternative to the standard cosmic system. This theory reconsiders the laws of celestial mechanics established by Isaac Newton, especially Newton’s second law, which contains the motion of bodies. By developing MOND, Milgrom gets rid of the modulus of dark matter by modifying its gravitational properties. Thus, the gravitational force experienced by the stars of the outer regions of the galaxy is proportional to the square of the so-called centripetal acceleration, that is, the acceleration of mass in revolving around a fixed center. If little work came to adopt the MOND theory until 2010, a progressively larger proportion of astrophysicists came to the defense of this new cosmological model. Thus, studies published by scholars Stacy McGaugh, Constantinos Skordis, and Tom Zlosnik brought some credibility to the creation of Mordechai Milgrom.

© ESA, NASA

Spiral galaxy ESO 373-8 is located 25 million light-years away and has been referred to by NASA as “flat as a pie.”

Several observations will still be necessary to demonstrate the prevalence of the MOND model and the obsolescence of the LCDM standard cosmological model. ” In the future, we will need a framework based exclusively on MOND and “Milgromian” gravity, regardless of dark matter, hot or cold. All MOND-based simulations are currently being studied and analyzed by a joint research group of the Universities of Bonn and Prague, under the direction of Professor Pavel Krupa. Moritz Halsbourg concludes.

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