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Scientists conducted a simulation of galaxy formation.
An international group of scientists came to the conclusion that in the Multiverse there must be other living beings populated the universes with other values of the cosmological constant. This result is contrary to the anthropic principle, according to which humanity lives in a Universe with an exceptionally favourable “settings”. The article was published in the journal the Monthly Notices of the Royal Astronomical Society.
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According to the hypothesis of the Multiverse, there are an infinite number of domains (universes) where the physical constants vary widely. Despite the fact that to prove this assumption at the moment is impossible, the hypothesis successfully explains the fine tuning of the Metagalaxy making it suitable for the emergence and evolution of biological organisms. For example, the cosmological constant (Λ) characterizing the density of energy of vacuum and influence the Universe to expand with acceleration, takes a very small value equal to 10 to the minus 53 degree per square meter. With a larger Λ Metagalaxy will expand too quickly, and it will not be able to form stars and galaxies, and negative values the universe collapses.
The strong anthropic principle indicates that the existence of an observer is possible only in a domain with fine tuning. It can be assumed, however, that in the Multiverse there are domains with slightly different values of the cosmological constant, which are also habitable. To predict typical whether our Metagalaxy in many of the inhabited universes, that is, its cosmological constant characteristic for most other domains, it is necessary to know how the values of Λ affect physical processes such as the formation of galaxies.
Scientists have conducted hydrodynamic simulations of the formation of galaxies and black holes in the framework of the project EAGLE (Evolution and Assembly of GaLaxies and their Environments), which takes into account the standard cosmological model ΛCDM. The input data consisted of a set of the cosmological constant from zero to the number of three hundred times greater than the observed value. During the simulation Λ is influenced by such factors of the formation and evolution of galaxies as radiation cooling 11 elements, star formation, stellar mass loss, black holes formation and accretion of gas in the galactic halo.
The simulation results allow to answer the question, what fraction of the observers in the Multiverse inhabits a domain with a certain value of Λ, i.e. what is the probability of observing a given cosmological constant. The researchers were able to deduce the approximate rate of appearance of observers and their number in the Universe based on the rate of birth of main sequence stars, their life time and the synthesis of chemical elements in them.It turned out that the probability to observe a cosmological constant present in our Metagalaxy, equal to two percent. Thus, the model refutes the strong anthropic principle, which suggests that this probability should be much more. However, scientists themselves do not rush to reject this possibility and explain the result of the fact that fine tuning is not limited to the influence of the cosmological constant on galactic structure, and should consider other physical constants.