December 14 marked the anniversary of the death of Andrei Sakharov (21.05.1921 - 14.12.1989), Nobel Peace Prize winner, academician of the USSR Academy
In memory of society, he remained as an outstanding physicist, "father" of the hydrogen bomb, as well as a humanist, an implacable fighter against social and political injustice. However, few people remember that one of the favorite destinations of scientific Sakharov was cosmology. About it, and told his close friend, a senior fellow at the LPI, Candidate of Physical and Mathematical Sciences Boris L. Altshuler.
Twenty years of his artistic career, from 1948 to 1968. Andrei Dmitrievich, dedicated work to develop nuclear weapons and restore the strategic balance of the USSR and the USA. After removal of the Sakharov secret theme he has 21 years, until his retirement from life, following the moral duty, to the struggle for nuclear disarmament, human rights, the elimination of the threat of self-destruction of humanity in a thermonuclear war. At the same time he idolized theoretical physics, "pure" science classes which in the circumstances is not always enough time.
From the memoirs of Boris L. Altshuler:
"When do you prefer science?" - I asked him in rapid socio-political period of the late 1980s after returning from exile.
"When I was again exiled to Gorky," - said Andrei smiled.
Work "Cosmological transitions with a change metric signature" was written in exile in 1983, and published in August 1984 for AD Sakharov was a difficult time for the fourth month he held an indefinite hunger strike, demanding to allow his wife traveled to the US for heart surgery. The appearance of this work was as if news of his friends and acquaintances. He seemed to be saying: "I - alive, I - I work».
This work was a logical continuation and development of the earlier works of Andrei Dmitrievich, "Cosmological models of the universe with the rotation of the arrow of time" (1980) and "Multivalent model of the Universe" (1982).
The word "signature of the metric" Simplification is the number of time axes of a Riemannian manifold, or Riemann space, in small areas which holds approximately Euclidean geometry, although in general this space can not be Euclidean. In our universe - at one time, then the signature is equal to one. In his article, AD Sakharov would take the signature (as well as the number of spatial dimensions) is not pre-specified value, and the dynamic variable that can be changed during the evolution of quantum space-time. He proposed a quantum dynamical principle to be taken into account metrics of arbitrary signature.
Review of the problem of the baryon asymmetry of the universe led Sakharov to the idea of cosmological CPT-symmetry of the universe, from which it follows that if the direction of flow of time (T-transformation) is necessary to make a mirror image of the space (P-conversion) with the replacement of all particles by antiparticles (C- conversion). It is because of this CPT-symmetry and followed the conclusion of the non-conservation of baryon charge and, as a consequence, the baryon asymmetry of the universe.
Developing the idea of CPT-symmetry, Andrei Dmitrievich was faced with the question: what about the postulate of irreversibility of time in the present world? Irreversibility of time Sakharov associated exclusively with the second law of thermodynamics and entropy growth. However, if the entropy increases, it means that it has been less than previously, and before that - is minimal or zero. But here's the question: is there a "before that?" Sakharov said that if the arrow of time is determined by an increase in entropy, the "earlier" can not be. There is a certain starting point from the moment of minimum entropy, from which the different sides time to develop a "later". This phenomenon is called Sakharov and "turn the arrow of time." In fact, it is a fact that in parallel to our "right-hand" the world begins to exist and "left-handed" world, in some ways mirror.
And turn the arrow of time can be carried out not only through the mechanism of CPT-symmetry, it is only a special case. There is another scenario. One of the most popular cosmological models of the universe - is a model of a pulsating or as he called it, Sakharov multisheeted universe. According to this model, the universe undergoes a cycle of expansion and contraction. At the moment of maximum compression is minimal entropy of the universe - it is the point of "zero", from which the arrow of time begins to run up to any of the parties. Then the universe begins to expand, entropy increases, the arrow of time is running "forward" (in the chosen direction). But at the moment maximize entropy of the universe also becomes minimal - space "empty" - and, therefore, has all the prerequisites to turn the arrow of time. Sakharov said that is what is happening: the universe ceases to expand and begins to shrink, turning "backwards" in all of its processes ...
According to the assumptions AD Sakharov, in fact there are many universes, radically different from each other and have arisen from some initial state, "the primary space" in the words of Sakharov. Unlike our universe consisting of three spatial and one temporal dimension (space (3 + 1) -Measurements), "other" of the universe, as well as the primary space will vary according to the number of space-time coordinates, ie it will be, so to speak, (m + n) -dimensional space.
Such a structure is called Andrei Dmitrievich Megavselennoy. The language of the Sakharov Megavselennaya - set of universes different number of dimensions, different signatures of different topologies, and possibly the existence of quantum superposition of these aggregates.
At the same time, Sakharov said that, despite the differences in the measurements and, accordingly, the conditions of development in different parts of Megavselennoy, the laws of nature must remain united. However, he stressed, referring to the work of P. Ehrenfest, and others, it is possible that it is the conditions that are available "our" 4-dimensional universe, contribute to the development of those forms of life that we have. This principle is called the anthropic sugars or anthropological (from the Ancient Greek. Anthropos - people). The essence of the principle is that we should not be surprised by some special characteristics of our universe, as their numerical values are due to the very fact of our existence.
The value of the work described Sakharov, however, is not only in the formation of these grandiose and fantastic, from the point of view of the common man, hypothesis formation, existence and development of the universe. Cosmological model of boom time allowed to solve one of the major paradoxes of physics, called "Global reversibility paradox" that had existed since the XIX century. Until a bold model Sakharov this paradox is explained by the initial conditions of the universe. That is "so - because it is so." Theory Swing Time unslung physicists heavy stone called "reverse flow of time».
Developing ideas Swing time multisheeted universe and finally Megavselennoy, AD Sugars showed that the "new" of the universe formed in the next cycle of tension and compression, need not necessarily be similar to the previous or inherit their "history". Against this background, as well as the calculations, Andrei Dmitrievich showed that the number of cycles of pulsation can be infinite, thus removing the problem of finite-dimensionality of pulsations of the universe.
Requires separate comments and correlation Sakharov anthropological principle and the cosmological constant.
The cosmological constant - a physical constant characterizing the properties of the vacuum, which was introduced by Einstein in the general theory of relativity to preserve the spatial homogeneity of statistical solutions of the gravitational field, binding metric of curved space-time with the filling of his mother. Practical confirmation of the existence of the cosmological constant was obtained after 1997. According to current estimates, its value is 5, 98 × 10-10 J / m3. This value is so small that the theoretical studies allows to neglect its influence on a scale smaller than cosmological.
In his paper "Cosmological transitions with change of metric signature" AD Sakharov wrote:
As is known, the cosmological constant Λ = 0 or abnormally low, and, more surprisingly, & lt; ... & gt; in a state of "true" vacuum with broken symmetries. The smallness or equal to zero Λ - is one of the main factors ensuring the duration of the universe - sufficient for the development of life and intelligence. Therefore it is natural to try to attract to solve the problem of the cosmological constant anthropological principle. & Lt; ... & gt;
We note in conclusion that in the space P (purely topological space that does not have the time and therefore not permitted to travel) should be considered an infinite number of U-inclusions (from Universe - field space-time continuum with signature 1, "our" universe), while parameters of an infinite number of them can be arbitrarily close to the parameters of the observable universe.
And finally, the fantastic, grand conclusion that Andrei Dmitrievich did conclude his thoughts: we can assume that the number of similar to our universe in which possible structure, life and mind - forever. This does not exclude the fact that life and intelligence are also possible in an infinite number of essentially different universes forming a finite or infinite number of classes of "similar" universes, including universes with different than ours signature.
This - the sugar: the man who loved life in all its unpredictability, multifaceted, "multivalence." The scientist who seemingly abstract theoretical hypotheses, saw the greatness of life, its fantastic, grandeur and infinity.
Since then, science has moved forward strongly. However, the solution of basic fundamental problems agitated Sakharov when he wrote his article in 1984, remains elusive, like the horizon.
Over the years, in observational astrophysics truly revolutionary events, pose new problems. In 1992, the oscillations were discovered cosmic microwave background radiation, called "Sakharov oscillations" theoretically described by him in 1965
And at the end of the 1990s it was discovered that in remote galaxies, the distance to which it was determined by the Hubble law, Type Ia supernovae have a brightness lower than that they're supposed to. As a result of analysis, it was concluded that the universe simply expands, it expands with acceleration. Then, these observations were supported by other sources: measurements of the CMB, gravitational lensing, during the Big Bang nucleosynthesis. All the data are well described by the inclusion of the Einstein equations extremely small positive cosmological constant, called "dark energy».
All visible to us and our devices substance ('Light' matter), accounts for only 5% of the mass of the universe; another 25% is occupied concentrated in galaxies so-called "dark matter", the existence of which is known only indirectly - from its gravitational effects on the dynamics of the expansion of the universe and the movement of the stars visible to us. The remaining 70% of the mass of the universe are hidden in a mysterious, evenly distributed in space "dark energy", which manifests itself, as has been said, in general, the acceleration of the universe. Pre-existing cosmological model assumed that the expansion of the universe is slowing down, eventually replaced by compression and ultimate collapse («Big Cranch»), which will inevitably burn everything animate and inanimate. On the contrary, the presence of a small positive cosmological constant guarantees perpetual expansion of the universe and saves us from the said universal catastrophe.
BL Altschuler: "Call theorists is that modern theoretical physics can not offer even a hypothetical natural explanations experimenters discovered the cosmological constant (" vacuum energy "), the magnitude of which is comparable with the average density of matter in the universe. But if the density of matter is computable, and a little due to the large volume of modern expanding universe, the cosmological constant - a parameter of the original theory. Ask, as they say, "hands" ultra low value of the fundamental constants of the world is absurd. And that's where it came from, such as remains a great mystery. Of course, in an attempt to find a solution there were many different models and theories. But all this is still very artificial. It is a pity that Andrei Dmitrievich did not live up to this interesting situation. Perhaps he would suggest something totally unexpected for out of this theoretical impasse. "