Cosmologists and physicists from the Institute for Theoretical Physics of the Russian Academy of Sciences have suggested that the discrepancies in the expansion rate of the Universe, calculated from supernova explosions and the "echo" of the Big Bang, can be explained by the fact that dark energy is unstable and gradually turns into dark matter, according to an article published in the journal MNRAS.
“If Einstein is 100% right, then dark energy is unchanging and eternal. But what if he's only, say, 99.99% right? There is so much dark energy in nature that if even a tiny fraction of it in the 14 billion years that have passed since the Big Bang, disintegrated into known elementary particles, including photons, it would be a colossal new source of energy useful for mankind - says Alexei Starobinsky from the ITF RAS, whose words are quoted by the press service of the institute.
Dark Deeds of the Universe
Back in 1929, the famous astronomer Edwin Hubble proved that our Universe does not stand still, but gradually expands, observing the movement of galaxies far from us. At the end of the 20th century, astrophysicists discovered, observing type I supernovae, that it was not expanding at a constant speed, but with acceleration. The reason for this, as scientists today believe, is "dark energy" - a mysterious substance that acts on matter as a kind of "antigravity".
In June 2016, Nobel laureate Adam Reiss and colleagues who discovered this phenomenon calculated the exact rate of expansion of the universe today using variable Cepheid stars in nearby galaxies, the distance to which can be calculated with ultra-high precision.
This refinement gave an extremely unexpected result - it turned out that two galaxies, separated by a distance of about 3 million light years, scatter at a speed of about 73 kilometers per second. Such a figure is noticeably higher than the data obtained with the WMAP and Planck orbital telescopes show - 69 kilometers per second, and it cannot be explained using our ideas about the nature of dark energy and the mechanism of the birth of the Universe.
These discrepancies made scientists, including Academician Starobinsky, think about two possible ways to explain this anomaly. On the one hand, it is quite possible that the measurements by Planck or Riesz and his colleagues are erroneous or incomplete. On the other hand, it is quite admissible that the properties of dark matter or dark energy have noticeably changed during the lifetime of the Universe, which could change the rate of its expansion.
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The simplest and most logical variant of such changes, as suggested by Starobinsky and his colleagues, is the unstable nature of dark energy or dark matter. Similar ideas, as the academician notes, had already been presented by Soviet scientists in the mid-1930s, but they then assumed that "dark" substances should decay into visible forms of matter.
The end of cosmological eternity
Now Russian cosmologists believe that the decay of their particles leads to the formation of new "dark" components of the Universe. In this case, their decay is not affected by external conditions, including the current rate of expansion of the universe, its age and other characteristics, but only the internal properties of dark matter and energy, as a result of which the rate of expansion of the Universe and its other properties, depending on the ratio of their shares in the universe will smoothly change.
Such decays, as the physicist explains, can go in three ways - as a result of a process similar to the destruction of the nuclei of "ordinary" unstable elements, the direct transformation of dark energy into dark matter, and the conversion of dark energy into "dark radiation" - a stream of light particles and peculiar " dark "photons that do not interact with visible matter.
“The analysis showed that the second model better than the others allows explaining both the existing cosmological parameters of the observed Universe and its evolution in the past. It follows from it that the half-life of dark energy through this channel is no less than 17 times the age of the Universe. In other words, if the decay of dark energy into dark matter does occur, then it goes very slowly,”continues Starobinsky.
Such a scenario, as the scientist notes, well describes the discrepancies in the expansion rates of the Universe that were discovered by Riess and his team, and similar data obtained as part of the BOSS project, aimed at searching for traces of the Big Bang in the distribution of galaxies in the Universe.
If these data are confirmed in the near future, then they can be considered a confirmation of the model of Starobinsky and colleagues and the first evidence that dark matter is not constant and stable, as postulated by the standard cosmological model.