Ringing of dark energy

Ten days ago, a sensation swept over the Internet - to the headings of K and one more beautiful: “Scientists believe that the expansion of the universe will never stop,” “The Universe will die as a result of an endless expansion,” etc.

The trigger for this journalistic avalanche was an article published in the Science journal on August 20, or rather, not a very cautious interview given by one of the co -authors not very competent journalists.

The article is called modestly: “Cosmological restrictions following the strong gravitational lensing in the accumulations of galaxies” (Cosmological Constraints from Strong Gravitational Lensing In Clusters of Galaxies). Authors: Eric Jullo, Priyamvada Natarajan, Jean-Paul Kneib, Anson d'Aloisio, Marceau Limousin, Johan Richard, Carlo Schimd (Different workplaces: Pasadena (JPL), Yale University, Marcel, Nielsa Institute Bora, Darem University). The work is technically complex, important, but not containing fundamentally new results. Nevertheless, an important one, since a new method is confirmed by a previously known fact that has a huge scientific and worldview significance: the Universe is expanding with acceleration under the exponential law. This is due to new physics, the so -called dark energy, the existence of which does not follow from previous experiments and theories. It is clear that such important facts require confirmation in all possible ways. Something about the background. The first swallow appeared in 1998. Two groups of researchers engaged in the search for distant supernova, published according to the article, which stated that supernovae type IA with great red displacement is further than prescribing the standard law of expansion of the universe (Friedman Law). The tops of this type are all the same and associated with exploding white dwarfs, they are used in cosmology as standard candles. If, thanks to the close supernova, we know their absolute brightness, then we can assess the distance at which the star explodes. Knowing the red displacement (it is very accurately and relatively easily measured) and, independently, the distance, we can get the kinematics of the expansion of the universe. It turned out that the data can be explained only by its accelerated expansion.

One fact is not enough. It was said that supernova IA is not so good standard candles that light is absorbed along the road with dust, that before the stars had a different chemical composition and this influenced the brightness of supernova - maybe they were weaker. But new independent evidence appeared. For example, the angular dimensions of the clusters of the galaxies were evaluated, and their dependence on red displacement was built. This also indicated an accelerated expansion. The strongest certificate is the results of the American WMAP station, which removed receusal cards of relict radiation. Relict radiation (more precisely, its heterogeneity) gives us a “line” of the known length in the earliest universe (Sakharovsky peak on the scale of fluctuations) and many other clockwork, which can be restored both the law of expansion and a number of cosmological parameters.

Accelerated expansion not only received confirmation, but also a good quantitative description. In particular, it became clear that our space, with good accuracy, is flat (that is, it is described by the geometry of Mingkovsky and not Riman or Lobachevsky) that about 30 % gravitating content of the Universe is matter (most of which is dark, that is, not interacting with our devices and therefore has an unknown nature), but about 70 % - the so -called dark energy. What is it?

The fact of accelerated expansion of the Universe lay down on well -prepared soil. Einstein also considered the opportunity to introduce an additional L-member into his equations of the general theory of relativity, which leads to the “self-growing” of the universe. The irony of fate lies in the fact that Einstein tried with the help of this member to “build” the Universe: the non -stationaryness of the Universe, proven by Alexander Friedman, initially caused moral discomfort.

It turned out that L-member could just do amazing things with the universe. Deiter built a cosmological model (the world of de-tester), where L-member leads to the exponential expansion of the universe. In the time of Einstein and De-Tester, the L-Minh was an arbitrary abstraction and the world of de-Titter was built as a purely speculative opportunity. However, subsequently people realized that l-member could not appear from the ceiling, but as a result of real physical phenomena. In other words, it can appear in the equations of the general theory of relativity not by the arbitrariness of the theorist, but through the tensor of energy-pulse, which is an integral part of the theory.

Suppose the universe is filled with a certain simple (scalar) homogeneous field. We do not feel this field, since it is the same everywhere and constantly in time - in fact it is indistinguishable from the vacuum. The field has a positive energy density, like all normal physical fields. But the whole focus is that it has negative pressure, in other words, with a tension similar to the tension of the surface film of water. In Einstein’s equations, such a field, being inscribed in the tensor of energy-pulse, leads to the appearance of a member, absolutely identical to the famous l-member. If the Universe is filled with a homogeneous substance, then its contribution to self -teague is proportional to E + 3 P, where E is the energy density, P is pressure. The three of P is stems from the three -dimensionality of space. Further, the result depends on the equation of the state, which can be recorded as p = w e. If the universe is filled with dust, then W = 0 (this applies to modern ordinary and dark matters); If light, then w = 1/3. In these cases, the universe is self -gust. In the case of a homogeneous scalax field w = -1 and we have self -growing! And the Universe expands with acceleration under the exponential law.

In the 70s and 80s, a very beautiful concept of a swollen universe appeared, based on this effect. It belongs to the very first moments of the existence of the universe, when it was a very strong field in it, and the scale of the Universe for the insignificant fraction of a second grew by many orders of magnitude due to the strongest gravitational self-growing. Further, this is a strong faning field, forming a huge long -lived universe, disappeared, moving into particles of matter. Further expansion continued by inertia. Such is in the most general terms the almost generally accepted picture of the birth of the Universe.

Against this background, the discovery of the exponential expansion of the modern universe does not look completely fantastic. In the first moments, the swelling was very fast, then the scale simply changed: instead of the strong, a very weak field was left, and swelling went many orders more slowly. But still, the fact requires new fundamental physical entities. The presence of such a field and its strange scale (insignificant density of energy) from modern theory do not follow. The new work, which caused so much noise, is associated with an independent determination of the distance to objects with a well -known red displacement. Actually, previous works are based on this principle, only in this case a new method of determining the distance was used - gravitational lensing. One of the most massive clusters of the galaxies, Abell 1689 was chosen as a lens, and the initial data used pictures of the Hubble space telescope and additional spectroscopic observations in ground telescopes. A massive cluster distorts the images of galaxies that are far behind, turning them into arcs and Serpiki, as well as breeds double, triple (and more) images of the same galaxy. These multiple images are data that must be adjusted by the method of maximum credibility. The fitting parameters include the distribution of mass in the cluster (described by a model with 21 free parameters tested on 58 clusters), as well as the position of each leve-in -ized galaxy, the distance to it and the distance from us to the lens itself. The distances are the desired data from which the law of expansion of the universe and the related cosmological parameters are directly pulled out.

The results obtained are well consistent with the previous ones. The declared accuracy of determining the WA parameter (see above) is 30 % better than the accuracy achieved according to the WMAP station. The value w = -0.97 ± 0.07 is consistent with the assumption that dark energy is a homogeneous constant scalar field. True, there were no tricks: the authors recorded the value of the constant hubbla and put the curvature of the universe equal to zero. In the results of WMAP, these parameters are released, so it is not known whose accuracy is actually higher. Nevertheless, this is certainly a good job, reinforcing the modern cosmological picture.

Another thing is that she did not bring any new revelations. A stormy sensation is a consequence of the small education of journalists who did not know that we are talking about long -known things. Perhaps part of the fault lies with one of the authors who did not bother to explain this clearly in an interview. When borrowing news, one media in absurdity accumulated and sometimes took grotesque forms. The most striking pearl was found in the news AIF ( www.aif.ru/techno/news/65524 ): “The astronomers came to this conclusion, exploring the giant“ galactic lens ” - one of the most famous galaxies in the constellation of the Virgin - which (i.e. Linza . Expanding faster and faster. ”

There was an opinion that all these bad sensations are more useful than harmful, since they attract the attention of the layman to science, and there, you see, someone will really be interested and figure it out. For example, they say, the noise of the threat of the end of the world because of the big collide-ra was fueled by the interest of the general public in the new accelerator. I don’t know, maybe this is so, but on one condition: if all this ringing takes off some relatively competent people so much that they will take up the pen. So there was an occasion to remind readers of dark energy ...

Boris Stern

The author is grateful to Oleg Verdradanov,
Pavel Ivanov and Sergey Popov
For useful comments.