After years of relative dryness, the scientific world seems to have discovered a new star: Juan Maldesena, a 32-year-old physics professor from Harvard, shows how the reality we live in may contain "folded" dimensions that we cannot discern
Bischem Azgad
Prof. Juan Maldesana, born in Argentina, who is currently considered the greatest promise in the theoretical physics of the elementary particles of matter, is also considered to be the one who managed to return and place the feet of theoretical physics on the ground of reality. Maldsena managed to bring string theory to heights that drew admiration from his colleagues. Most of his fame came to him when he showed - in a detailed calculation - how string theory can contain phenomena that occur in our universe.
Like politicians who hope to unite forces, trade union businessmen who call to close the ranks and businessmen who dream of company mergers, physicists also strive to show that the world is fundamentally built of one type of particles between which one and only force operates. To take a quick look at this simple, symmetrical and aesthetic dream world, they search, above and below the ground, for different ways to go deeper into the intricacies of matter. And when technology confronts them with its irritating limits, physicists return to the basics: paper, pencil, thought. If it is impossible to obtain proof "in sight", they will be satisfied with circumstantial proof. But even such proofs are not so easy to obtain. This is a tough game against an opponent (Hateva) who enjoys a decisive home advantage, but here and there our forces also manage to extract encouraging original insights.
But sometimes it is quite difficult to internalize these insights. For example, in 1985, a rumor spread at the Institute for Advanced Studies in Princeton about a "revolutionary lecture" that the young physicist Ed Witten was going to give. Thus, when Witten went up to the lecture stand, he discovered a full auditorium in front of him. In the audience sat physicists with world names, some of them Nobel laureates. Everyone held their breath when Witten managed, in spectacular mathematical tricks, to justify the arguments of two physicists who had not received much publicity until then, Michael Green and John Schwartz, about the properties of string theory. Witten's "Blessing of the Way" succeeded in renewing the days of this Torah, which until then was considered a failure, but, as the physicist Freeman Dyson commented in his book "Infinite to all directions": "Everyone left the room with a certain sadness and asked themselves what a 'superstring' actually is, And if there is a connection between this vague concept and the material reality of the world we live in."
The superstrings were actually born out of a predicament that arose from experiments that showed that there are many hadron particles in nature (such as the proton and the neutron). For those who aspire to see a world of one particle and one force, this is a clearly intolerable situation. A similar situation previously led to the assumption of the existence of elementary and smaller particles that make up the protons and neutrons (quarks). This is how, more or less, the "standard model" was born, the most accepted and up-to-date theory based on the structure of matter, which divides the particles of matter into several "families" and describes four forces: gravity, the "color force", the electromagnetic force and the weak force (the last two actually stem from an ancient and more basic force called the "electro-weak force").
The successes in formulating the standard model increased the enormous appetite of the physicists, who began to believe that the material reality we know is nothing more than a broken symmetry whose roots lie in a more symmetrical fundamental state, in which the universe looks the same from every point of view from which one looks at it, so that in fact there is not such a great difference between the various particles and Not among the forces acting on them. As a religious Jew says in the Mincha prayer on Shabbat: You are one and your name is one. That is, all the material difference in the universe, all the particles we know today, are actually manifestations and products of one "primitive element"; And all the forces operating in nature are but different aspects of one and the same primordial force, which from different points of view can look like gravity, the weak force or the electro-weak force. Just like the elephant that a group of blind people try to describe based on the feel of its various limbs.
This "primitive element", called "string", differs from all the particles we have known so far in several ways. First, it is smaller. Freeman Dyson says that a string is smaller than an atom as the ratio of a single atom to the solar system. Second, all "normal" particles are (from the physicists' point of view) "points" in the geometric sense of the word. meaning dimensionless. They have no length, no width, and no depth. The material nature of these particles results from "dressing" processes in which the particles are wrapped in different fields and adhere to other particles. On the other hand, the string, according to the descriptions of its proponents, has a characteristic structure and one dimension (length). It is only able to exist in systems with very high energy, such as the one that existed in the first fractions of a second after the Big Bang, and since it is unlikely that we will be able to reproduce the conditions of this system on Earth, it seems that in the foreseeable future it will be very difficult for us to prove the existence of the strings.
According to this concept, all the particles of matter that make up the universe are created following the vibration of the strings at their lowest resonance, as they move, coalesce, separate and rush through space-time. In other words: material reality is the "music" played by the strings. The string can be closed (annular) or open (straight or coiled), and when it moves in space-time, it "unfolds" a sheet and imposes various constraints on it.
All well and good, except that the attempts to explain the multiplicity of the hadronic particles using string theory were unsuccessful, and it was abandoned. Although, one feature of this theory seemed particularly attractive: in systems of relatively low energies, the strings have properties that up until that time were considered the "property" of only one particle that is supposed to carry the force of gravity: the graviton (which has not yet been directly observed); On the other hand, it would seem that she is suffering from a "terminal illness" that does not allow her to exist for a long time in our world.
At this point, Schwartz and Green came and showed that, despite everything, this theory has a "right to exist in our world". Witten, as mentioned, gave these findings the "official confirmation", and thus, string theory, which failed in its attempt to explain the multiplicity and properties of the hadronic particles, "jumped to a higher league" and offered a rather convincing description of the elusive force in nature, gravity, in accordance with the theory of general relativity of Einstein.
This exciting insight was overshadowed by two clouds. One is the theory of supersymmetry, according to which strings can only exist and move in a world in which there exist many particles that have not yet been discovered, and the other stems from calculations according to which string theory can exist and correctly describe reality only in a universe that has 26 dimensions. Later it turned out that if you combine the string in the supersymmetry (which gives rise to the nickname "superstring"), the number of dimensions drops from 26 to 10.
How can a theory that talks about a ten-dimensional universe describe the four-dimensional reality of our lives? Is it possible that in reality there are more dimensions than we see? Physicists studying string theory show in their calculations that such a situation is absolutely possible, if only we are willing to assume that alongside the four known dimensions (which, for the sake of abstraction, each of them can be seen as a line) six other dimensions are "folded". According to these calculations, if the diameter of the "folding" of these additional dimensions is very small, their existence will not contradict the picture of material reality as it appears to us. To understand what "folded dimensions" are, you can think of an ant on a pipe with a diameter of, say, half a meter. If she walks along the tube she will notice one dimension of her world: length. If she goes around its diameter, she will return to the place from which she set out on her journey and notice another, different dimension. But, if the diameter of the tube is very small, much smaller than the size of the ant itself, it will not be able to walk on it and will not notice it. Physicists studying string theory offer a picture of reality in which six dimensions exist "folded" and "shrunk" to such an extent that we cannot distinguish them. In other words, if this theory is correct, then in some ways, our world is as narrow as an ant's world.
Encouraged by these calculations, the physicists began to try to show how a picture of reality that fits the "standard model", i.e. the world we live in, can be created and exist within the framework (more precisely, on the margins) of string theory. The inevitable result of this activity was the appearance of many string theories, which created a feeling among the physicists that they were moving away from the goal (one universe, one particle, one force and one theory that describes all of these). In one of the attempts to show how realistic or near-realistic "things" can exist within the framework of string theory, the Iranian physicist Kamron Vaffa and the Jewish physicist Andy Strominger (both from Harvard) showed how a certain string theory could allow the existence of special black holes (which do not exist in the universe we live in it). A rather narrow argument.
At this point Prof. Maldsana entered the arena. He was born in 1968 in Buenos Aires. His father was an engineer and as a child he thought he would also be an engineer when he matured. "I didn't know anything about physics then", he recalls. In 1992, after receiving a bachelor's and master's degree in Argentina, the young star landed at Princeton University and in '96 received his doctorate. Already in his doctoral thesis, supervised by Kurt Callan, Maldsena managed to get out of the unknown universe of Vappa and Strominger and show how string theory might allow the existence of "real" black holes.
"He is the best doctoral student in his cohort and in all the cohorts before him," stated his supervisor at Princeton, Kurt Callan, in the evaluation form he was asked to fill out. A short time later, only 30 years old, he was accepted as a professor at Harvard University, where he still serves today. Only two years have passed since then, and Maldsena managed to bring string theory to heights that elicited exclamations of admiration from his colleagues. Most of his fame came to him when he showed - in a detailed calculation - how string theory can contain phenomena that occur in the universe in which we live. As a natural continuation of his doctoral work, Maldsana chose a phenomenon called "holography", which manifests itself near black holes. This phenomenon, which was first described by Prof. Jacob Bekenstein from the Hebrew University, manifests itself in the compression of three-dimensional information (volume) into a two-dimensional surface.
Maldsana went further and showed two ways in which "holography" can exist within the framework of string theory. The first option is based on a special universe that includes ten dimensions, five of which are "folded" dimensions so that we cannot distinguish them, and five "large" dimensions (such as the three dimensions of space and time that we know). In other words, in our immediate environment there may exist another "big" dimension, waiting for us to discover it. The second option is even more amazing. It describes a four-dimensional universe in which there exists both gravity and a theory very similar to the theory of the color force, through which the physicists in our world were able to explain the multiplicity of the hadronic particles and formulate the standard model theory. Thus closes a plot circle reminiscent of the story of Rambo, who returns to the battlefields of Vietnam to close some open matters. String theory, which at the beginning of its journey failed to explain the multiplicity of hadron particles in our world, and due to its failure was thrown out the window, thanks to Maldesena, returned to the center of the scientific arena and showed that in the end it is the basis for the solution found to the problem of the multiplicity of hadrons in the past (the theory of the color force), but then not We managed to discover this connection.
Maldsana won many international prizes and grants for this work, including the prestigious MacArthur grant (physicists call it the "genius grant"), and recently won the Sackler Prize from Tel Aviv University with Michael Douglas from Rutgers University. Physicists at scientific conferences have already composed a song of praise in his honor to the tune of the Brazilian hit "Macarena", and then competed among themselves in musical-verbal performances above the lecturer's podium. The words of this scientific hit were written by Prof. Jeffrey Harvey from the University of Chicago. Prof. Eliezer Rabinowitz of the Hebrew University, whose research group contributed some insights into the "ambiguity" properties of string theories, says that physicists who participated in a scientific conference in Santa Barbara faithfully sang Harvey's words, when the chorus "Ahhh from Akarna" they replace with "Ahhh from Aldesana" ” while their feet stomp the floor of the assembly hall in what appears to be quite a bit like dancing. From all of these it seems that the scientific world has gained, after quite a few years of relative dryness, a new star, who for a change is even young, healthy, and comparatively even quite rich.
But is everything we see really nothing more than the "music" of the strings? Are we approaching the bottom of the barrel of nature's secrets? Will we ever be able to truly understand what everything is made of? Maldsana, introverted, quiet, adheres to modest manners, although it is evident that he knows his own value: "To answer these questions, it will take at least 20 and maybe even 30 years," he says. "We have fairly good indications that we are on the right track. But maybe not."
{Appeared in Haaretz newspaper, 23/6/2000}
