UNITED STATES, WASHINGTON (OBSERVATORY) — Physicists have long been concerned about the mystery of vacuum energy. According to existing theories, it should be 120 orders of magnitude (!) More than follows from astronomical observations. A fresh idea makes it possible to reconcile with facts this “worst forecast in the history of science.”
The new model is described in a scientific article published in the journal Physical Review Letters by Steven Carlip of the University of California.
The 20th century gave the world two of the greatest physical theories. One of them is the general theory of relativity (GR). She interprets gravity as a curvature of space-time. Its effects are measurable when the gravitational field is created by a very massive body (planet, star, and so on). With rare exceptions, they appear only in astronomical observations.
Another is quantum field theory (QFT), which describes the quantum properties of matter. They appear for very small objects, such as elementary particles and atoms. With great difficulty, quantum effects are observed in large molecules.
It is easy to see that the region where quantum effects are observed almost does not intersect with the estate of GR. And this is, in a sense, a great success, since GR and KTP are incompatible with each other. An attempt to apply them simultaneously to the same object often leads to internally contradictory and meaningless results.
However, physicists do not abandon attempts, so to speak, to glue the two theories in manual mode. Leaving alone cases where the incompatibility of the two approaches is striking, they are exploring the possibility of applying them to other situations.
Such work has been ongoing for a long time and in different directions. For example, one of such hybrid models led the famous Stephen Hawking to the discovery of radiation, later named after him (black holes should emit him). Although it has never been directly observed, experiments have confirmed the reality of its analogues .
Also, one of such “docking” theories in the mid-20th century led the eminent theoretician John Wheeler to the concept of quantum, or space-time, foam.
The fact is that, according to KTP, in vacuum all the time pairs of virtual particles and their antiparticles are born, which are immediately mutually destroyed (annihilate). The smaller the scale of the considered space-time region, the greater the energy of these particles. It turns out that if an arbitrarily small region can be distinguished in space-time, then the energy concentrated there will be arbitrarily large.
This is where GTR comes into play. The fact is that according to this theory, gravity is created not by mass as such, but by any energy. Just under ordinary conditions, the rest energy of any body is immeasurably greater than any other supply of its energy. In fact, the rest energy is calculated by the sacramental formula E 0 = mc 2, where c is the speed of light in vacuum. And, for example, the kinetic energy of the body – of formula E k = mv 2 /2 Where v – velocity of the body.
Let’s say a bullet flying at a speed of one kilometer per second moves 300 thousand times slower than light. This means that its kinetic energy is less than the rest energy by 45 billion times. Yes, according to GR, kinetic energy contributes to gravity. But this correction for the bullet (and other bodies familiar to us) is negligible compared to the rest energy. Therefore, we can usually assume that gravity depends only on the rest energy, that is, ultimately on the mass.
But, as we have already said, in a rather small region of space-time, the energy of the generated virtual particles can reach arbitrarily large values. This energy should give rise to gravity, that is, the curvature of space-time.
The calculations led Wheeler and other scientists to the idea that, on a scale of Planck length (10 -35 meters), space-time is a seething mass of black holes and mole holes that arise and disappear in Planck time (10 -44 seconds).
However, this means that the vacuum has tremendous energy. Theorists have calculated that it should manifest itself as a cosmological constant, which Vesti.Nauka (nauka.vesti.ru) described in detail . Recall that this is the quantity responsible for accelerating the expansion (or contraction) of the Universe.
Today, the accelerated expansion of space is a reliably confirmed observational fact that is associated with mysterious dark energy . However, judging by the pace of this acceleration, the amount of dark energy is 10 120 times less than that predicted by the model of quantum foam (one and 120 zeros after it). The famous theoretician Lee Smolin at one time called this forecast of theory the worst in the entire history of science.
Many researchers tried to reconcile the concept of quantum foam with observations, but none of these attempts were recognized by the scientific community as successful enough. Now Karlip has proposed his option to the court of experts.
The physicist suggested that space is actually expanding with the tremendous acceleration that quantum foam theory requires. It’s just that in different areas of the Planck volume this acceleration has different signs. Simply put, some areas expand and others shrink. When averaging over a plurality of sections of the Planck volume (and in one cubic femtometer they are already on the order of 10 60 ), an almost zero result is obtained.
However, how will such a system evolve over time? It would seem that expanding areas of space will expand more and more, and soon nothing will remain of the shrinking ones. Thus, soon the whole Universe will consist only of expanding regions, and again the question will be asked why astronomers do not see this bloat with incredible acceleration.
However, Karlip showed that this “obvious” scenario is incorrect. For this, he took into account the fact that quantum foam again appears inside the expanded regions of space. In addition, the researcher relied on the assumption that all equations are reversible in time, that is, the past state of the system can be unambiguously restored from its current state.
He also needed a special technique for gluing expanding and collapsing regions of space-time along the edges. Finally, he resorted to some mathematical simplifications of the model.
Thus, in the author’s model, a huge acceleration of the expansion of space, predicted by the theory of quantum foam, does exist, but at a micro level that is currently inaccessible for observation and experimentation. At the macro level, it does not appear, which astronomers have long witnessed.
As clarifies the publication Physics, Karlip states that at the moment his model is not a detailed cosmological theory. In particular, she does not specify where the non-zero amount of dark energy comes from, which leads to the observed acceleration of the expansion of the Universe.
In addition, the conclusions of the researcher, of course, should be checked by the expert community.
Finally, it is worth remembering that attempts to combine GTR and KTP in their current form are walks on thin ice. No one can guarantee that two theories, the incompatibility of which is shown in many cases, in some other example will give a meaningful result together.
Many physicists believe that such a model could be provided by a reliable foundation only by a model containing general relativity and quantum transient theory as its simplified cases. Such a candidate is, for example, string theory.
This article is written and prepared by our foreign editors writing for OBSERVATORY NEWS from different countries around the world – material edited and published by OBSERVATORY staff in our newsroom.
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