Ontological analysis of fundamental cosmology-forming objects (strings, branes, etc.). Cosmological models associated with field string theory Bulatov, Nikolai Vladimirovich Cosmological models associated with field string theory
A factor that greatly complicates the understanding of string cosmology is the understanding of string theories. String theories and even M-theory are only limiting cases of some larger, more fundamental theory.
As already said, string cosmology asks several important questions:
1. Can string theory make any predictions about the physics of the Big Bang?
2. What happens to extra dimensions?
3. Is there inflation within string theory?
4. What can string theory tell us about quantum gravity and cosmology?
Low energy string cosmology
Most of the matter in the Universe is in the form of dark matter unknown to us. One of the main candidates for the role of dark matter are the so-called WIMPs, weakly interacting massive particles ( WIMP - W eakly I interacting M passive P article). The main candidate for the role of a WIMP is the candidate from supersymmetry. Minimal Supersymmetric Standard Model (MSSM, or in English transcription MSSM - M minimal S supersymmetric S tandard M odel) predicts the existence of a particle with spin 1/2 (fermion) called neutralino, which is a fermionic superpartner of electrically neutral gauge bosons and Higgs scalars. Neutralinos must have a large mass, but at the same time interact very weakly with other particles. They can make up a significant portion of the density in the Universe without emitting light, making them a good candidate for dark matter in the UniverseString theories require supersymmetry, so in principle, if neutralinos are discovered and it turns out that they are what dark matter is made of, that would be nice. But if supersymmetry is not broken, then fermions and bosons are identically equal to each other, and this is not the case in our world. The really tricky part of all supersymmetric theories is how to break supersymmetry without losing all the benefits it provides.
One of the reasons why string and elementary physicists love supersymmetric theories is that supersymmetric theories produce zero total vacuum energy because the fermion and bosonic vacua cancel each other out. And if supersymmetry is broken, then bosons and fermions are no longer identical to each other, and such mutual cancellation no longer occurs.
From observations of distant supernovae, it follows with good accuracy that the expansion of our Universe (at least for now) is accelerated due to the presence of something like vacuum energy or a cosmological constant. So no matter how supersymmetry is broken in string theory, it must end up with the "right" amount of vacuum energy to describe the current accelerated expansion. And this is a challenge for theorists, since so far all methods of breaking supersymmetry provide too much vacuum energy.
Cosmology and extra dimensions
String cosmology is very messy and complex, largely due to the presence of six (or even seven in the case of M-theory) extra spatial dimensions that are required for the quantum consistency of the theory. represent a challenge even within the framework of string theory itself, and from the point of view of cosmology, these additional dimensions evolve in accordance with the physics of the Big Bang and what came before it. Then what keeps the extra dimensions from expanding and becoming as large as our three spatial dimensions?However, there is a correction factor to the correction factor: superstring duality known as T-duality. If the space dimension is collapsed to a circle of radius R, the resulting string theory turns out to be equivalent to another other string theory with the space dimension collapsed to a circle of radius L st 2 /R, where L st is the string length scale. For many of these theories, when the radius of the extra dimension satisfies the condition R = L st, the string theory gains additional symmetry with some massive particles becoming massless. It is called self-dual point and it is important for many other reasons.
This dual symmetry leads to a very interesting assumption about the Universe before the Big Bang - such a string Universe begins with flat, cold and very small state instead of being twisted, hot and very small. This early Universe is very unstable and begins to collapse and contract until it reaches a self-dual point, at which point it heats up and begins to expand, resulting in the current observable Universe. The advantage of this theory is that it includes the string behavior of T-duality and self-dual point described above, so this theory is quite a theory of string cosmology.
Inflation or collision of giant branes?
What does string theory predict about the source of vacuum energy and pressure needed to cause accelerated expansion during an inflationary period? Scalar fields that could cause the inflationary expansion of the Universe at Grand Unified Theory scales may be involved in the process of breaking symmetry at scales slightly above the electroweak, determining the coupling constants of gauge fields, and maybe even through them obtaining the vacuum energy for the cosmological constant. String theories have the building blocks to build models with supersymmetry breaking and inflation, but it is necessary to put all these building blocks together so that they work together, which is still said to be a work in progress.Now one of the alternative models to inflation is the model with collision of giant branes, also known as Ecpyrotic Universe or Big Cotton. In this model, everything starts with a cold, static five-dimensional space-time that is very close to being completely supersymmetric. Four spatial dimensions are limited by three-dimensional walls or three-branes, and one of these walls is the space in which we live. The second brane is hidden from our perception.
According to this theory, there is another three-brane, "lost" somewhere between the two boundary branes in the four-dimensional ambient space, and when this brane collides with the brane on which we live, the energy released from this collision heats up our brane and in our Universe the Big Bang begins according to the rules described above.
This assumption is fairly new, so we'll see if it stands up to more rigorous testing.
Acceleration problem
The problem with the accelerated expansion of the Universe is a fundamental problem not only within the framework of string theory, but even within the framework of traditional particle physics. In models of eternal inflation, the accelerated expansion of the Universe is unlimited. This unlimited expansion leads to a situation where a hypothetical observer forever traveling through the Universe will never be able to see parts of the events in the Universe.The boundary between a region that an observer can see and one that he cannot see is called event horizon observer. In cosmology, an event horizon is similar to a particle horizon, except that it is in the future rather than in the past.
From the point of view of human philosophy or the internal consistency of Einstein's theory of relativity, the problem of a cosmological event horizon simply does not exist. So what if we will never be able to see some corners of our Universe, even if we live forever?
But the cosmological event horizon problem is a major technical problem in high energy physics due to the definition of relativistic quantum theory in terms of a set of scattering amplitudes called S-matrix. One of the fundamental assumptions of quantum relativistic and string theories is that incoming and outgoing states are infinitely separated in time, and that they thus behave as free, non-interacting states.
The presence of an event horizon implies a finite Hawking temperature, so the conditions for determining the S-matrix can no longer be met. The absence of an S-matrix is that formal mathematical problem, and it arises not only in string theory, but also in theories of elementary particles.
Some recent attempts to solve this problem have involved quantum geometry and changing the speed of light. But these theories are still in development. However, most experts agree that everything can be resolved without resorting to such radical measures.
The Myth of the Beginning of Time Gabriel Veneziano
According to string theory, the Big Bang was not the beginning of the formation of the Universe, but only a consequence of its previous state.
Was the Big Bang the beginning of time or did the Universe exist before it? Ten years ago such a question seemed ridiculous. Cosmologists saw no more sense in thinking about what happened before the Big Bang than in searching for a path going north from the North Pole. But the development of theoretical physics and, in particular, the emergence of string theory forced scientists to think again about the pre-primary era.
The question of the beginning has occupied philosophers and theologians since ancient times. It is intertwined with many fundamental problems, reflected in the famous painting by Paul Gauguin "D"ou venons-nous? Que sommes-nous? Ou allons-nous?" ("Where do we come from? Who are we? Where are we going?"). The canvas depicts the eternal cycle: birth, life and death - the origin, identification and purpose of each individual. Trying to understand our origins, we we trace our ancestry back to past generations, early forms of life and proto-life, chemical elements that arose in the young Universe, and, finally, to the amorphous energy that once filled space.Does our family tree go back to infinity or is space as not eternal as And we?
| REVIEW: STRING COSMOLOGY
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Even the ancient Greeks argued fiercely about the origin of time. Aristotle rejected the idea of the existence of a certain beginning, explaining this by the fact that nothing arises from nothing. And since the Universe could not arise from nothingness, it means that it has always existed. Thus time must extend endlessly into the past and into the future. Christian theologians defended the opposite point of view. Thus, St. Augustine argued that God exists outside of space and time and can create them in the same way as other aspects of our world. To the question “What did God do before he created the world?” the famous theologian answered: “Time itself is part of God’s creation, it simply didn’t exist before!”
Modern cosmologists have reached a similar conclusion based on Einstein's theory of general relativity, according to which space and time are soft, malleable entities. On a universal scale, space is dynamic in nature: over time it expands or contracts, carrying matter along with it. In the 1920s Astronomers have confirmed that our Universe is currently expanding: galaxies are moving away from each other. It follows from this that time cannot extend endlessly into the past - back to the 1960s. this was proven by Steven Hawking and Roger Penrose. If we look through cosmic history in reverse order, we will see how all the galaxies seem to fall into a black hole and are compressed into a single infinitesimal point - a singularity. In this case, the density of matter, its temperature and the curvature of space-time turn to infinity. At the singularity, our cosmic lineage ends and cannot extend further into the past.
Strange coincidence
The inevitable singularity poses a serious cosmological problem. In particular, it does not fit well with the high degree of homogeneity and isotropy that characterizes the Universe on a global scale. Since space in the broad sense of the word became the same everywhere, it means that there was some kind of connection between distant regions of space that coordinated its properties. However, this contradicts the old cosmological paradigm.
Let's look at what happened in the 13.7 billion years that have passed since the origin of the cosmic microwave background radiation. Due to the expansion of the Universe, the distance between galaxies has increased by 10 thousand times, while the radius of the observable Universe has increased significantly more - approximately 1 million times (because the speed of light exceeds the speed of expansion). Today we see areas of the Universe that we could not see 13.7 billion years ago. For the first time in cosmic history, light from the most distant galaxies has reached the Milky Way.
However, the properties of the Milky Way are essentially the same as those of distant galaxies. If you meet two people dressed identically at a party, it can be explained by a simple coincidence. However, if there are ten people in similar outfits, it means that they have agreed in advance on the form of clothing. Today we observe tens of thousands of independent sections of the celestial sphere with statistically identical characteristics of the relict background. Perhaps such areas of space were already the same at birth, i.e. The homogeneity of the Universe is a mere coincidence. However, physicists have come up with two more plausible explanations: in the early stages of its development, the Universe was either much smaller or much older than previously thought.
Most often, preference is given to the first alternative. It is believed that the young Universe went through a period of inflation, i.e. accelerating expansion. Before him, the galaxies (more precisely, their progenitors) were very densely packed and therefore became similar to each other. During inflation, they lost contact because the light could not keep up with the frantic expansion. When the inflation ended, the expansion began to slow and the galaxies came back into view of each other.
Physicists believe that the culprit of the rapid inflationary surge is the potential energy accumulated 10-35 s after the Big Bang in a special quantum field - the inflaton. Potential energy i, in contrast to rest mass and kinetic energy i, leads to gravitational repulsion. The gravity of ordinary matter would slow down the expansion, and the inflaton, on the contrary, would accelerate it. The theory of inflation, which appeared in 1981, accurately explains the results of a number of observations (see special report “Four Keys to Cosmology,” “In the World of Science,” No. 5, 2004). However, it is still not clear what the inflaton was and where it got so much potential energy from.
The second alternative involves rejecting the singularity. If time did not begin at the moment of the Big Bang, and the Universe arose long before the current cosmic expansion began, then matter would have had enough time to smoothly organize itself. Therefore, scientists decided to reconsider the reasoning leading to the idea of singularity.
| TWO VERSIONS OF THE BEGINNING |
| In our expanding Universe, galaxies scatter like a crowd that disperses. They move away from each other at a speed proportional to the distance between them: galaxies separated by 500 million light years move away twice as fast as galaxies separated by 250 million light years. Thus, all the galaxies we observed must have simultaneously started from the same place at the moment of the Big Bang. This is true even if cosmic expansion goes through periods of acceleration and deceleration. In space-time diagrams (see below), galaxies move along winding paths in and out of the observable part of space (yellow wedge). However, it is not yet known exactly what happened at the moment when the galaxies (or their predecessors) began to fly apart. |
The assumption that the theory of relativity is always valid seems very doubtful. After all, it does not take into account quantum effects that should have dominated near the singularity. To finally understand everything, you need to include the general theory of relativity in the quantum theory of gravity. Theorists have been struggling with this problem since the time of Einstein, but only in the mid-1980s. the matter got off the ground.
Evolution of the revolution
Two approaches are being considered today. In the theory of loop quantum gravity, the theory of relativity remains essentially intact, only the procedure for its application in quantum mechanics changes (see Lee Smolin's article "Atoms of Space and Time", "In the World of Science", No. 4, 2004). In recent years, proponents of loop quantum gravity have made great strides and achieved great understanding, but their approach is not radical enough to solve the fundamental problems of quantizing gravity. Elementary particle theorists faced a similar problem. In 1934, Enrico Fermi proposed an effective theory of the weak nuclear force, but attempts to construct a quantum version of it initially failed. What was needed was not a new technique, but a conceptual change, which was embodied in the theory of electroweak force proposed by Sheldon Glashow, Steven Weinberg and Abdus Salam in the late 1960s.
The second approach seems more promising to me - string theory, a truly revolutionary modification of Einstein's theory. It grew out of a model I proposed in 1968 to describe nuclear particles (protons and neutrons) and their interactions. Unfortunately, the model was not entirely successful, and after a few years it was abandoned, preferring quantum chromodynamics, according to which protons and neutrons consist of quarks. The latter behave as if connected by elastic strings. Initially, string theory was devoted to describing the string properties of the nuclear world. However, it soon began to be considered as a possible option for combining the general theory of relativity and quantum mechanics.
The basic idea is that elementary particles are not point-like particles, but infinitely thin one-dimensional objects called strings. The vast family of diverse elementary particles is reflected by the many possible modes of vibration of the string. How does such a simple theory describe the complex world of particles and their interactions? The secret is in the so-called magic and quantum strings. Once the rules of quantum mechanics are applied to a vibrating string along which vibrations propagate at the speed of light, it develops new properties that are closely related to particle physics and cosmology.
First, quantum strings have a finite size. An ordinary (non-quantum) violin string could be cut in half, then one of the halves could be broken into two again, and so on, until a point particle with zero mass would be obtained. However, the Heisenberg uncertainty principle does not allow us to divide the string into parts less than approximately 10-34 m long. The smallest quantum of length is denoted ls and is a natural constant, which in string theory is on par with the speed of light c and Planck's constant h.
Second, even massless quantum strings can have angular momentum. In classical physics, a body with zero mass cannot have angular momentum, since it is defined as the product of speed, mass and distance to the axis. But quantum fluctuations change the situation. The angular momentum of a tiny string can reach 2h even if its mass is zero, which exactly matches the properties of the carriers of all known fundamental forces, such as the photon and graviton. Historically, it was this feature of angular momentum that attracted attention to string theory as a candidate theory of quantum gravity.
Third, quantum strings require the existence of additional spatial dimensions. A classical violin string will vibrate no matter what the properties of space and time are. A quantum string is more finicky: the equations that describe its oscillations remain consistent only if spacetime is highly curved (which contradicts observations) or contains six extra dimensions.
Fourthly, the physical constants that determine the properties of nature and are included in the equations reflecting Coulomb's law and the law of universal gravitation cease to be independent, fixed constants. In string theory, their values are dynamically set by fields similar to electromagnetic fields. Perhaps the field strengths were not the same over different cosmological eras or in distant regions of space. String theory will receive serious experimental confirmation if scientists manage to register even a slight change in physical constants.
One such field, the dilaton, occupies a central place in string theory. It determines the overall strength of all interactions. The size of the dilaton can be interpreted as the size of an additional spatial dimension - the 11th in a row.
| STRING THEORY |
| String theory is the most promising (though not the only) theory that attempts to describe what happened at the Big Bang. Strings are material objects much like the strings of a violin. When a violinist moves his fingers along the soundboard of the instrument, he reduces the length of the strings and causes an increase in the frequency of vibrations and, therefore, their energy and. If the string is shortened to subatomic dimensions, quantum effects begin to operate, preventing further reduction in length.
A subatomic string can not only move as a whole or oscillate, but also curl like a spring. Let's assume that space is cylindrical. If the circumference is greater than the minimum permissible length of the string, increasing the speed of movement requires a small increment of energy, and each turn requires a large one. However, if the circle is shorter than the minimum length, less energy is expended on the additional turn than on the speed increment. Therefore, the total effective energy I remains unchanged. A string cannot be shorter than a quantum of length, so matter, in principle, cannot be infinitely dense.
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Tying up loose ends
Finally, quantum strings have helped physicists discover a new kind of natural symmetry—dualism—that changes our intuitive understanding of what happens when objects become extremely small. I have already referred to one form of dualism: usually a long string is heavier than a short one, but if we try to make it shorter than the fundamental length ls, it starts to get heavier again.
Because strings can move in more complex ways than point particles, there is another form of symmetry called T-dualism, which states that small and large extra dimensions are equivalent. Consider a closed string (loop) located in a cylindrical space, the circular section of which represents one finite additional dimension. The string can not only vibrate, but also rotate around the cylinder or wrap around it (see figure above).
The energy cost of both states of the string depends on the size of the extra dimension. The winding energy is directly proportional to its radius: the larger the cylinder, the more the string stretches and the more energy it stores. On the other hand, the energy associated with rotation is inversely proportional to the radius: cylinders of larger radius correspond to longer waves, and therefore lower frequencies and lower energy values. If a large cylinder is replaced by a small one, the two states of motion can exchange roles: the energy associated with rotation can be provided by winding and vice versa. An external observer notices only the magnitude of the energy and, and not its origin, therefore for him the major and minor radii are physically equivalent.
Although T-dualism is usually described in terms of cylindrical spaces in which one of the dimensions (the circle) is finite, one variant of it applies to the ordinary three dimensions, which seem to extend infinitely. One must speak with caution about the expansion of infinite space. Its total size cannot change and remains infinite. But it is still capable of expanding in the sense that the bodies located in it (for example, galaxies) can move away from each other. In this case, what matters is not the size of space as a whole, but its scale factor, according to which the distances between galaxies and their clusters change, noticeable by the red shift. According to the principle of T-dualism, universes with both small and large scale factors are equivalent. There is no such symmetry in Einstein's equations; it is a consequence of the unification contained in string theory, with the dilaton playing a central role here.
There was once an opinion that T-dualism is inherent only in closed strings, since open strings cannot be wound, since their ends are free. In 1995, Joseph Polchinski of the University of California, Santa Barbara, showed that the principle of T-dualism applies to open strings when the transition from large to small radii is accompanied by a change in conditions at the ends of the string. Before this, physicists believed that no forces acted on the ends of the strings and that they were absolutely free. At the same time, T-dualism is ensured by the so-called Dirichlet boundary conditions, under which the ends of the strings are fixed.
Conditions at the string boundary can be mixed. For example, electrons may turn out to be strings whose ends are fixed in seven spatial dimensions but move freely within the other three, forming a subspace known as a Dirichlet membrane, or D-membrane. In 1996, Petr Horava of the University of California and Edward Witten of the Institute for Advanced Studies in Princeton, New Jersey, suggested that our Universe is located on just such a membrane (see the articles "Information in holographic Universe", "In the world of science", No. 11, 2003 and "Who violated the law of gravity?", "In the world of science", No. 5, 2004). Our inability to perceive the full 10-dimensional splendor of space is due to the limited mobility of electrons and other particles.
| PRE-EXPLOSION SCENARIO | ||||||||||||
 The first attempt to apply string theory to cosmology was the development of the so-called pre-explosion scenario, according to which the Big Bang was not the moment of the origin of the Universe, but simply a transitional stage. Before it, expansion accelerated, and after it, it slowed down (at least at the beginning). The galaxy's path through spacetime (right) is shaped like a glass.
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Taming the Infinity
All the magical properties of quantum strings indicate that they hate infinity. Strings cannot shrink to an infinitesimal point, and therefore they are not subject to the paradoxes associated with collapse. The difference in their size from zero and new types of symmetry set upper limits for increasing physical quantities and lower limits for decreasing ones. String theorists believe that if we play back the history of the universe, the curvature of spacetime will increase. However, it will not become infinite, as in the traditional Big Bang singularity: at some point its value will reach a maximum and begin to decrease again. Before string theory, physicists desperately tried to come up with a mechanism that could eliminate the singularity so cleanly.
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| Attracted to each other, two almost empty membranes are compressed in a direction perpendicular to the direction of movement. | The membranes collide and their kinetic energy is converted into matter and radiation. This collision is the Big Bang. |
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Conditions near time zero, which corresponds to the beginning of the Big Bang, are so extreme that no one yet knows how to solve the corresponding equations. Nevertheless, string theorists take the liberty of speculating about what the Universe was like before the Big Bang. There are currently two models in use.
The first of these, known as the pre-explosion scenario, we began developing in 1991. It combines the principle of T-dualism with the more familiar time-reversal symmetry, whereby physical equations work equally well regardless of the direction of time. This combination allows us to talk about new possible versions of cosmology, in which the Universe, say, 5 s before the Big Bang expanded at the same speed as 5 s after it. However, the change in the rate of expansion at these moments occurred in opposite directions: if after the Big Bang the expansion slowed down, then before it it accelerated. In short, the Big Bang may not have been the moment the universe began, but simply a sudden transition from acceleration to deceleration.
The beauty of this picture is that it automatically implies a deeper understanding of inflation theory: the Universe must have gone through a period of acceleration to become so homogeneous and isotropic. In the standard theory, acceleration after the Big Bang occurs under the influence of the inflaton introduced specifically for this purpose. In the pre-explosion scenario, it occurs before the explosion as a natural consequence of new types of symmetries in string theory.
According to this model, the Universe before the Big Bang was an almost perfect mirror image of itself after it (see figure above). If the Universe rushes boundlessly into the future, in which its contents are liquefied into a meager pulp, then it also extends boundlessly into the past. For an infinitely long time, it was almost empty: it was filled only with an incredibly rarefied, chaotic gas of radiation and matter. The forces of nature controlled by dilaton were so weak that the particles of this gas practically did not interact with each other.
But time passed, the forces increased and pulled the matter together. Matter randomly accumulated in some areas of space. There, its density eventually became so high that black holes began to form. The matter inside such areas turned out to be cut off from the surrounding space, i.e. The universe was breaking into separate parts.
Inside a black hole, space and time change roles: its center is not a point in space, but a moment in time. Matter falling into a black hole becomes increasingly dense as it approaches the center. But, having reached the maximum values allowed by string theory, the density, temperature and curvature of space-time suddenly begin to decrease. The moment of such reversal is what we call the Big Bang. The interior of one of the described black holes became our Universe.
It is not surprising that such an unusual scenario caused a lot of controversy. Thus, Andrei Linde from Stanford University argues that in order for such a model to be consistent with observations, the Universe must have arisen from a black hole of gigantic dimensions, much larger than the length scale in string theory. But our equations do not impose any restrictions on the size of black holes. It just happened that the Universe formed inside a fairly large hole.
A more serious objection comes from Thibault Damour of the Institute of Higher Scientific Research in Bourg-sur-Yves in France and Marc Henneaux of the Free University of Brussels: matter and space-time near the moment of the Big Bang should have behaved chaotically, which certainly contradicts the observed regularity of the early Universe. I recently proposed that such chaos could produce a dense gas of miniature "string holes" - extremely small and massive strings on the verge of becoming black holes. This may be the key to solving the problem described by Damour and Annaud. A similar suggestion was made by Thomas Banks of Rutgers and Willy Fischler of the University of Texas at Austin. There are other critical considerations, but it remains to be seen whether they reveal any fundamental flaws in the model described.
| OBSERVATIONS | ||
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Membrane collision
Another popular model that implies the existence of the Universe before the Big Bang is the ekpyrotic scenario (from the Greek ekpyrotic - “coming from fire”), developed three years ago by Justin Khoury of Columbia University and Paul Steinhardt of Princeton University , Burt A. Ovrut of the University of Pennsylvania, Nathan Seiberg of the Institute for Advanced Study, and Neil Turok of the University of Cambridge. It is based on the assumption that our Universe is one of many D-membranes drifting in multidimensional space. The membranes are attracted to each other, and when they collide, they can create what we call the Big Bang (see figure above).
It is possible that collisions occur cyclically. Two membranes can collide, bounce off each other, move apart, be attracted to each other, collide again, and so on. Diverging after the impact, they stretch a little, and when they approach each other again, they compress again. When the direction of motion of the membrane is reversed, it expands with acceleration, so the observed accelerating expansion of the Universe may indicate an impending collision.
The pre-explosive and ecpyrotic scenarios have common features. They both start with a big, cold, nearly empty universe, and both have the difficult (and as yet unsolved) problem of transitioning from before the Big Bang to after it. Mathematically, the main difference between the two models is the behavior of the dilaton. In the pre-explosion scenario, this field and, accordingly, all the forces of nature are initially very weak and gradually strengthen, reaching a maximum at the moment of the Big Bang. For the ekpyrotic model, the opposite is true: a collision occurs when the forces are minimal.
The developers of the ekpyrotic scheme initially hoped that the weakness of the forces would make it easier to analyze the collision, but they have to deal with the high curvature of space-time, so it is not yet clear whether they will be able to avoid the singularity. Moreover, this scenario must occur under very specific circumstances. For example, just before the collision, the membranes must be almost perfectly parallel to each other, otherwise the resulting Big Bang will not be homogeneous enough. In the cyclic version, this problem is not so acute: successive impacts would allow the membranes to align.
Leaving aside for now the difficulties of fully mathematically substantiating both models, scientists must figure out whether they will ever be able to be tested experimentally. At first glance, the described scenarios are very similar to exercises not in physics, but in metaphysics: a lot of interesting ideas that can never be confirmed or refuted by observational results. This view is too pessimistic. Both the inflation stage and the pre-explosion era should have left behind artifacts that can still be seen today, for example, in small variations in the temperature of the cosmic microwave background radiation.
First, observations show that temperature deviations were formed by acoustic waves over several hundred thousand years. The regularity of fluctuations indicates the coherence of sound waves. Cosmologists have already rejected a number of cosmological models that cannot explain wave synchronicity. The inflation, pre-Big Bang, and membrane collision scenarios pass this first test. In them, in-phase waves are created by quantum processes that have intensified during the accelerating cosmic expansion.
Secondly, each model predicts a different distribution of temperature fluctuations depending on their angular size. It turned out that large and small fluctuations have the same amplitude. (Deviations from this rule are observed only on very small scales, in which the initial deviations have changed under the influence of later processes.) Inflationary models reproduce this distribution with high accuracy. During inflation, the curvature of space changed relatively slowly, so that fluctuations of different sizes arose under almost identical conditions. According to both string models, the curvature changed rapidly. As a result, the amplitude of small-scale fluctuations increased, but other processes amplified large-scale temperature deviations, leveling the overall distribution. In the ecpyrotic scenario, this is facilitated by an additional spatial dimension separating the colliding membranes. In the pre-explosion scheme, the axion, a quantum field associated with the dilaton, is responsible for leveling the distribution of fluctuations. In short, all three models are consistent with the observed results.
Third, in the early Universe, temperature variations could arise due to fluctuations in the density of matter and due to weak fluctuations caused by gravitational waves. In inflation, both causes are equally important, and in string scenarios, density variations play a major role. Gravitational waves should have left their mark on the polarization of the cosmic microwave background radiation. It may be possible to detect it in the future using space observatories such as the European Space Agency's Planck satellite.
The fourth check is related to the distribution of fluctuations. In the inflationary and ekpyrotic scenarios, it is described by Gauss's law. At the same time, the pre-explosion model allows significant deviations from the normal distribution.
Analysis of the cosmic microwave background radiation is not the only way to test the theories discussed. The pre-Big Bang scenario involves the emergence of a random background of gravitational waves in a certain frequency range, which in the future can be detected using gravitational observatories. In addition, since string models vary the dilaton, which is closely related to the electromagnetic field, they should both exhibit large-scale magnetic field fluctuations. It is possible that their remains can be found in galactic and intergalactic magnetic fields.
So when did time begin? Science does not yet provide a definitive answer. Yet according to two potentially testable theories, the universe—and therefore time—existed long before the Big Bang. If one of these scenarios is true, then space has always existed. It may collapse again one day, but it will never disappear.
ABOUT THE AUTHOR:
Gabriel Veneziano Gabriele Veneziano, a theoretical physicist at CERN, created string theory in the late 1960s. However, it was soon recognized as erroneous, since it did not explain all the properties of the atomic nucleus. Therefore, Veneziano took up quantum chromodynamics, to which he made major contributions. When in the 1980s String theory began to be talked about as a theory of quantum gravity; Veneziano was the first to apply it to black holes and cosmology.
ADDITIONAL LITERATURE
Perhaps scientists are closer to solving the most intriguing mystery of the universe: are there other universes besides ours?
Albert Einstein throughout his life tried to create a “theory of everything” that would describe all the laws of the universe. Did not have time.
Today, astrophysicists suggest that the best candidate for this theory is superstring theory. It not only explains the processes of expansion of our Universe, but also confirms the existence of other universes located next to us. "Cosmic strings" represent distortions of space and time. They may be larger than the Universe itself, although their thickness does not exceed the size of an atomic nucleus.
However, despite its amazing mathematical beauty and integrity, string theory has not yet found experimental confirmation. All hope lies in the Large Hadron Collider. Scientists are waiting for him not only to discover the Higgs particle, but also some supersymmetric particles. This will be a serious support for string theory, and therefore for other worlds. In the meantime, physicists are building theoretical models of other worlds.
Science fiction writer Herbert Wells was the first to tell earthlings about parallel worlds in 1895 in his story “The Door in the Wall.” 62 years later, Princeton University graduate Hugh Everett amazed his colleagues with the topic of his doctoral dissertation on the splitting of worlds.
Here is its essence: every moment, every universe is split into non-
an imaginable number of their own kind, and the very next moment each of these newborns is split in exactly the same way. And in this huge multitude there are many worlds in which you exist. In one world, while reading this article, you are traveling on the subway, in another, you are flying on an airplane. In one you are a king, in another you are a slave.
The impetus for the proliferation of worlds is our actions, Everett explained. As soon as we make any choice—“to be or not to be,” for example—how in the blink of an eye two universes turn out from one. We live in one, and the second is on its own, although we are present there too.
Interesting, but... Even the father of quantum mechanics, Niels Bohr, remained indifferent to this crazy idea.
1980s. Linde's worlds
The theory of many worlds could have been forgotten. But again a science fiction writer came to the aid of scientists. Michael Moorcock, on some whim, settled all the inhabitants of his fairy-tale city of Tanelorn in the Multiverse. The term Multiverse immediately appeared in the works of serious scientists.
The fact is that in the 1980s, many physicists had already become convinced that the idea of parallel universes could become one of the cornerstones of a new paradigm in the science of the structure of the universe. The main proponent of this beautiful idea was Andrei Linde, a former employee of the Physical Institute. Lebedev Academy of Sciences, and now a professor of physics at Stanford University.
Linde bases his reasoning on the basis of the Big Bang model, as a result of which a lightning-fast expanding bubble appeared - the embryo of our Universe. But if some cosmic egg turned out to be capable of giving birth to the Universe, then why cannot we assume the possibility of the existence of other similar eggs? Asking this question, Linde built a model in which inflationary universes arise continuously, budding off from their parents.
To illustrate, you can imagine a certain reservoir filled with water in all possible states of aggregation. There will be liquid zones, blocks of ice and bubbles of steam - they can be considered analogues of parallel universes of the inflationary model. It represents the world as a huge fractal, consisting of homogeneous pieces with different properties. Moving around this world, you will be able to smoothly move from one universe to another. True, your journey will last a long time - tens of millions of years.
1990s. Worlds of Rhys
The logic of the reasoning of Martin Rees, professor of cosmology and astrophysics at the University of Cambridge, is approximately as follows.
The probability of the origin of life in the Universe is a priori so small that it looks like a miracle, argued Professor Rees. And if we do not proceed from the Creator hypothesis, then why not assume that Nature randomly gives birth to many parallel worlds, which serve as a field for experiments in creating life.
According to the scientist, life arose on a small planet orbiting an ordinary star in one of the ordinary galaxies of our world for the simple reason that its physical structure was favorable for this. Other worlds in the Multiverse are most likely empty.
2000s. Worlds of Tegmark
Professor of physics and astronomy at the University of Pennsylvania Max Tegmark is convinced that universes can differ not only in location, cosmological properties, but also in the laws of physics. They exist outside of time and space and are almost impossible to depict.
Consider a simple universe consisting of the Sun, Earth and Moon, the physicist suggests. For an objective observer, such a universe appears to be a ring: the Earth’s orbit, “smeared” in time, seems to be wrapped in a braid - it is created by the trajectory of the Moon around the Earth. And other forms personify other physical laws.
The scientist likes to illustrate his theory using the example of playing Russian roulette. In his opinion, every time a person pulls the trigger, his universe splits into two: where the shot occurred, and where it did not. But Tegmark himself does not risk conducting such an experiment in reality - at least in our Universe.
Andrei Linde is a physicist, creator of the theory of an inflating (inflationary) Universe. Graduated from Moscow State University. Worked at the Physical Institute named after. Lebedev Academy of Sciences (FIAN). Since 1990, he has been a professor of physics at Stanford University. Author of more than 220 works in the field of particle physics and cosmology.
Gurgling space
— Andrey Dmitrievich, in what part of the multifaceted Universe are we, earthlings, “registered”?
- Depending on where we ended up. The Universe can be divided into large regions, each of which, in all its properties, looks locally like a huge Universe. Each of them is enormous in size. If we live in one of them, then we will not know that other parts of the Universe exist.
— Are the laws of physics the same everywhere?
- I think they are different. That is, in reality, the law of physics may be the same. It is just like water, which can be liquid, gaseous and solid. However, fish can only live in liquid water. We are in a different environment. But not because there are no other parts of the Universe, but because we can only live in
convenient segment of the “many-faced Universe”.
— What is this segment of ours like?
- On the bubble.
— It turns out that, in your opinion, when people appeared, they were all sitting in one bubble?
- No one has sat yet. People were born later, after inflation ended. Then the energy that was responsible for the rapid expansion of the Universe turned into the energy of ordinary elementary particles. This happened due to the fact that the Universe boiled, bubbles appeared, like in a boiling kettle. The walls of the bubbles hit each other, released their energy, and due to the release of energy, normal particles were born. The universe became hot. And after that people appeared. They looked around and said: “Oh, what a big Universe!”
Can we get from one bubble universe to another?
— Theoretically, yes. But along the way we will stumble upon a barrier. This will be a domain wall, energetically very large. To reach the wall, you need to be a long-liver, because the distance to it is about 10 millionths of light years. And in order to cross the border, we need to have a lot of energy to accelerate well and jump over it. Although it is likely that we will die right there, because particles of our earthly type can decay in another universe. Or change your properties.
— Do bubble universes appear constantly?
- This is an eternal process. The universe will never have an end. In different parts of it, different pieces of the Universe of different types arise. It happens like this. Two bubbles appear, for example. Each of them expands very quickly, but the Universe between them continues to inflate, so the distance between the bubbles remains very large, and they almost never collide. More bubbles appear and the Universe expands even further. Some of these bubbles do not have any structure - they have not formed. And in another part, galaxies arose from these bubbles, one of which we live in. And there are about 10 to the thousandth power or 10 to the hundredth power of these different types of the Universe. Scientists are still counting.
—What happens in these many copies of the same Universe?
“The Universe has now entered a new stage of inflation, but a very slow one. This will not affect our Galaxy yet. Because the matter inside our Galaxy is gravitationally very strongly attracted to each other. And other galaxies will fly away from us, and we will no longer see them.
-Where will they fly to?
- To the so-called horizon of the world, which is located at a distance of 13.7 billion light years from us. All these galaxies will stick to the horizon and fade away for us, becoming flat. The signal from them will no longer come, and only our Galaxy will remain. But this won't last long. Over time, the energy resources in our Galaxy will gradually dry up, and a sad fate will befall us.
- When will this happen?
“Fortunately, we won’t break up anytime soon.” In 20 billion years, or even more. But because the Universe is self-regenerating, because it produces more and more new parts in all its possible combinations, the Universe as a whole and life as a whole will never disappear.
Ontological analysis of fundamental cosmology-forming objects (strings, branes, etc.)
To build quantum cosmology it is necessary to create a quantum theory of gravity. It is believed that the quantum theory of gravity can be built precisely on the Planck scale. But in cosmological terms (the moment the expansion of the Universe begins), on this scale all 4 fundamental interactions are possibly unified, therefore, united the theory must gain strength at the Planck level. It follows that in a certain sense the quantum theory of gravity, the unified theory, and Planck cosmology are identical.
Work on creating a quantum theory of gravity has been going on for more than half a century, and enough variants of such a theory have been proposed. Currently, two theories are considered the most promising for the role of such a theory: superstring theory (TST) and the theory of loop quantum gravity (LQG). There is an extensive literature devoted to these theories. In this section, we will be interested in the question of the ontology of the fundamental, cosmology-forming objects of these theories. Relevance of ontological analysis in quantum cosmology is determined by the need to clarify the nature of extreme states of matter, primarily the Planck state, and also in connection with the deep mediation of modern physical knowledge.
At the Planck level, we are dealing with a fundamentally new type of material existence, which has no analogues in modern physics. This circumstance greatly complicates the construction of a theory of quantum cosmology. Therefore, before discussing the cosmological models themselves, in our opinion, it is necessary to analyze the objectivity that will represent the meaningful basis of these models. Indeed, the fundamental object of the TSS, the string, will form one cosmology, and the loop or Planck cell of space in the TPCG will form another. Moreover, as K. Rovelli notes, both theories are designed to describe the Planck scale, and it is at this level that they differ significantly in relation to, for example, the problem of the nature of space-time.
Let us consider the fundamental cosmology-forming objects of string theory.
Superstring as a fundamental object of quantum cosmology .
In TSS the main object is string. Let us briefly describe the main features of this object that we need in the future. A string is a one-dimensional physical object of the Planck length scale (lPl = 10-33 cm), but research shows the possibility of the existence of strings of cosmological sizes. Research has shown that strings have supersymmetry, therefore they are called superstrings, and the theory is accordingly called TSS. In the future, a string will always be understood as a superstring. According to the theory, various modes of string vibrations represent elementary particles and produce not only their entire set, but also many other particles. The latter is one of the difficulties of the theory. TSS is a theory with background dependence. This means that the strings are in an independently existing space-time in which they can move. Since, unlike TSS, the general theory of relativity is background-independent, in which space and time are dynamic characteristics, one of the most important tasks is to construct TSS as a background-independent theory if we build a quantum theory of gravity by quantizing GTR. This strategy further aggravates the problem of clarifying the nature of space and time and their role in physical theory.
Ontologically fundamental is the search for answers to the following three questions: 1) are strings material, 2) do they represent only a geometric structure, the ontology of which still needs to be determined, 3) or are they just some kind of abstract mathematical means, a mathematical construction introduced for theoretical a more effective (and perhaps purely pragmatic) solution to some physical problems? Researchers are divided on the answers to these questions.
Are strings material? One of the arguments of supporters of a positive answer to the first question (in particular, the accidental discoverer of string theory G. Veneziano) is, for example, that different modes of string vibrations produce physically real elementary particles. Indeed, it is logical to assume that real particles can be generated by real physical objects. At the same time, there is no doubt that the physical nature of the string differs from the nature of an elementary particle, since the nature of the latter, according to TSS, is contained in the oscillatory process. It follows that the nature of the known elementary particles is purely phenomenological. In the language of metaphysics, their essence is vibrations, which (the essence) for the observer manifests itself in the form of a phenomenon of “elementary” material objectivity. But within the framework of the same metaphysical language, all this means that elementary particles (electrons, quarks, photons) do not possess some primary substantiality, they are only phenomena.
At the same time, the question arises: do the strings themselves have substance? And which? It seems natural, if the answer is positive, to associate with them a fundamentally new type of matter. Moreover, perhaps this should be a type of materiality no less fundamental and radical than the fundamentality of the electromagnetic field introduced during the period of dominance of the mechanistic picture of the world, or the discovery of a curved 4-dimensional space-time. Apparently, it should be of an even higher degree of fundamentality. The search for a physical ontology of this scale is, in our opinion, the most pressing problem of Planck cosmology and all physics.
Geometric nature of strings. This and a number of other arguments represent the position of supporters of a positive answer to the second question. A non-trivial image in this regard was proposed by S. Weinberg. From his point of view, “Strings can be thought of as tiny one-dimensional cuts in the smooth fabric of space.” Proponents of a purely geometric interpretation of strings are faced with the task of ontologizing their approach. Is it possible to give some other physical meaning to such a geometric structure as a superstring? Is it possible to add some new physical interpretation to the already existing content of the global program, which is paradoxically formulated in the following words: “Physics is geometry”?
Let us note that within the framework of a positive answer to this question, space and time become the fundamental and global physical substance. Alternatively, we should talk about substantiality structures space and time, which expresses greater certainty and localization of this nature of substantiality: geometric, topological, topos, etc.
Within the framework of the geometric approach to the nature of strings, the latter can also manifest themselves as known material objects in the form of, for example, elementary particles only phenomenologically. The fact is that, within the framework of the geometrization program of physics, attempts have been and are being made to represent all elementary particles in the form of pure structures of the geometry of space-time (not necessarily 4-dimensional), for example, in the form of local microscopic regions of highly curved space-time. These geometric structures are perceived as real phenomenological physical objects, in particular particles, only in relation to a macroscopic observer of an anthropomorphic nature.
Strings as an abstract aid to physical description? Is a string a formal auxiliary mathematical construct such as a wave function, Lagrangian, trajectories in phase space, etc.? This option is hardly adequate in the literal sense, since the vibration modes of the string give rise to all real elementary particles. In connection with the latter, the string, apparently, should be a fundamentally new elementary object of physics and nature.
On the physical elementality of strings. Within the framework of TSS, a string is an elementary, primary physical object. But - extended! The latter is believed to make it possible to bypass the most difficult problem of quantum field theory - the problem of infinite values of physical quantities, which arises due to the postulation of the point nature of elementary particles. However, the combination of elementarity and extension leads to some conceptual difficulties.
On the one hand, conceptually and metaphysically, one can see here a return to the Cartesian substantiality of extension. It is unlikely that in modern physics the metric property of extension can be considered as a substance or even a special substance. In a program of complete geometrization of physics, it is much easier to imagine geometry as a substance as a richer entity. But perhaps extension could be considered as an attribute (of matter)? And perhaps this would be nice at a new, modern stage in the evolution of knowledge, however, how philosophically correct is it today to consider extension as an attribute? An attribute in terms of a universal property, at least of nature? Quantum mechanics taught us exactly the opposite - the attribution of discreteness, the quantization of the physical world. And it is precisely this attribution that is radicalized at the Planck cosmological level, at the level of the merging of the minimally (ultimately) discrete and the maximally large (of the entire Universe). Apparently, the principle of complementarity and those philosophical concepts that propose to consider the unity of the continuous-discrete binary are valid. But does continuity reduce to discreteness? Apparently, the question regarding the elementarity of an extended string is something like this: how can ontologically understand the elementarity (indivisibility) of extension? How can we understand such extended elementarity in the case if the extension reaches cosmic scales, that is, in the case of the possible existence of cosmic (cosmological) strings?
Our pre-string-paradigm consciousness really wants to ask the question: is it not extended string made of parts? Just like a line consists of points. But a line is made of points and is not made of them. This understanding of the line is underdetermined, since here the theory of continuums intervenes in the theoretical game, which, for example (geometric uncertainty or underdetermination), states that a straight line and a square have the same continuum power. In other words, the number of points on a (1-dimensional) line is equal to the number of points in a (2-dimensional) square. So what is the elementality of the string in physical and geometric terms?
On the conceptual status of branes in TSS. Recently it turned out that in string theory, along with one-dimensional strings, there can also exist objects of other dimensions - branes: two-dimensional (2-branes or membranes), 3-branes, which play an important role in cosmology, and in general p-branes (where p is any dimension ). There are also 0-branes, an analogue of a point. They also play a certain role in the theory, since the ends of open (unclosed) strings are precisely 0-branes. Strings, for example, can be attached at their ends to branes and thus move along them, which has an important physical meaning.
So maybe a string consists of a 0-brane, and it is they that play the primary fundamental role? It would seem that this is the simplest and most obvious approach. However, TCC is in no hurry to reach such a conclusion. String theorists so far prefer the option according to which all branes are fundamental. Obviously, this view also requires further clarification and clarification.
Conceptually, perhaps the worst thing is that in this approach, from the existence of the primary element of physical existence - strings - they return again to the diversity of “primacy”. But the multi-element nature of existence is difficult to reconcile with the unity of physical existence, unless, of course, we consider it in the spirit of V. S. Solovyov, or one of the variants of interpretation of dialectical materialism as the unity of diversity. It seems that conceptually and methodologically modern fundamental physics is still set up to search for some primary objectivity, be it the geometry of empty space-time, a superstring, space and time quanta in TPCG, etc.
Space made of strings. One of the most interesting, but at the same time the most conceptually difficult models in string theory is the model of space as a total coherent ensemble of strings. The essence of this idea is as follows. In the most general case, the strings can be directed in different directions, they can vibrate completely arbitrarily, chaotically. But under certain conditions they can synchronize and begin to vibrate in the same phase, becoming a coherent set. To an outside observer they will be perceived as a continuous variety. Often such a picture is compared to a piece of fabric in which individual threads are intertwined in a strictly geometric order.
According to this approach, no space exists as a kind of reality. Space becomes not only relational, but also phenomenological in nature. However, here a difficulty arises with the interpretation of the nature of space and TSS as a background-dependent theory. And indeed, if the strings themselves in a coherent state form space, then what about the independence of the existence of space itself (against the background of which the strings move)?
Further, within the framework of this approach, space loses its attribution and universality, because space can only arise where there is a coherent set of strings. It is quite logical to assume that strings can be locally coherent. This leads to a far-reaching conclusion: in this case we can talk about the existence of local spaces in a wider “area of reality” in which there is no space! This should give rise to a new cosmological ontology of local existence in space.
Finally, cosmic strings, becoming coherent, must also create a new kind (type) of space! In this case, the phenomenological string fabric of space is “stitched” by cosmological “threads”-strings. It can be hypothesized that the different types of coherence that strings can exhibit can give rise to different types of spaces. The natural question is: what exactly, and above all, how exactly are all these possible types of spaces conceptually different? It is likely that spaces of different natures may exist, and not only different in geometric terms, but also in ontological terms. In fact this means that objectivity generates space. Let us emphasize once again that this is a far-reaching not only physical-theoretical, but also philosophical conclusion. On the one hand, it closely correlates with the relational concept of space, on the other, it has significant specificity, since space is formed not by all objects of reality (as in the relational approach), but only by objects of the Planck scale or, perhaps, by the primary elements of reality, which in this case represented by strings. To somewhat specify the principle of ontological pluralism, we can also propose principle of ontological spatial pluralism. Moreover, an important philosophical conclusion is that space(and apparently time) are being created! They are created in large quantities and of different nature. True, it’s good that everything is still natural...
On the nature of string coherence. It is also important to answer the difficult question of what causes a huge number of strings to begin to vibrate in one phase and become coherent? On the one hand, this force (or cause) must be total in order to act in the entire space of the Universe existing today, on the other hand, it must be local (quantized) in order to influence every string. Essentially, it must be either some kind of metaforce (metacause) that determines (essentially creates) the entire space of the entire universe, and in this case the principle of short-range action is unlikely to be valid.
As a hypothesis, we can assume that quantum correlations, which were discovered in the analysis of the EPR paradox and numerous Bell experiments, can function here. As such a force or cause, one can also consider, for example, the dilaton field existing in the TSS, which “determines the overall strength of all interactions” (G. Veneziano). The above words of G. Veneziano, if taken literally, should require the existence of many interactions, which, in turn, should mean a situation far from a unified theory. On the other hand, if the dilaton field determines the force everyone interactions, then this field has a certain function associated with the unity of all forces. This means that on the Planck scale, where the unification of all forces occurs, this field should play a central, fundamental role. Apparently, the presence of such a field on the Planck scale, as well as its nature, still needs to be clarified. The fact is that any quantized field consists of quanta of this field, which are elementary particles. But elementary particles (quanta of the corresponding fields) are modes of string vibrations. It follows that any field, including the dilaton one, is not a fundamental physical object. Within the framework of TSS, they are left with only strings.
It is interesting that “The magnitude of the dilaton can be interpreted as the size of an additional spatial dimension - the 11th in a row” (G. Veneziano). This is undoubtedly an interesting result of the theory. If the theorists' conclusion is correct, then the deeper nature of such a physical identification remains to be clarified: the field and one of the dimensions of space. This result can be expressed as new equivalence principle: the magnitude of the physical field is equivalent to the measurement of space. But, as is easy to see, many questions remain here. Is any field equivalent to any dimension? If not, what is a more specific formulation of equivalence? Does the 11th dimension of space have any physical meaningful distinction? Isn't there something more hidden behind this equivalence, some new physical content? Etc.
Ontology of collapsed dimensions. String theory continues to develop Kaluza's idea of the multidimensionality of space and the folded (compactified) nature of additional dimensions, which, nevertheless, lead to observable physical effects. But do all extra dimensions have to be collapsed? The choice of the collapsed nature of the measurements explains their unobservability and makes it possible to describe them mathematically. But is compactification the only option? Additional dimensions or even parallel worlds could, in principle, exist in an unfolded form. The whole question is how to explain their unobservability and learn to describe them effectively.
In particular, the reason for the 3-dimensionality of space may lie in the fact that the observer himself is three-dimensional. If he were of a different spatial-geometric nature, for example, if he were spatially 4-dimensional, then perhaps he would perceive the space surrounding him as also 4-dimensional. This hypothesis can be considered as a kind of extension of the anthropic principle: space is such (namely, 3-dimensional) precisely because the person existing in it is 3-dimensional.
On the search for new principles. A philosopher of science cannot but rejoice at the fact that leading physicists, when working on creating a theory, do not forget about conceptual things. Thus, B. Green in his books repeatedly and persistently calls for looking for some fundamental principle in string theory: “... is string theory itself a necessary consequence of some broader principle, perhaps, but not necessarily, the principle of symmetry, in the same sense, in which the equivalence principle inevitably leads to general relativity, and gauge symmetries lead to non-gravitational interactions? At the time of writing this book, no one knows the answer to this question.” He expresses the hope that such a principle exists: “... a central organizing principle that embraces these discoveries, as well as other properties of the theory, within one universal and systematic approach, which makes the existence of each ingredient absolutely inevitable, has not yet been found. The discovery of this principle would be a central event in the development of string theory, as it would likely reveal the inner workings of the theory with previously unattainable clarity. Of course, there is no guarantee that such a fundamental principle exists, but the evolution of physics over the last century gives theorists reason to hope that it does exist. As we consider the next stage of development of string theory, finding its “principle of no alternative”—that basic idea from which the entire theory will necessarily emerge—has the highest priority.” A similar point of view is supported in a unique form by S. Weinberg. From his point of view, "Although it is not difficult to imagine a final theory which doesn't have explanations in terms of deeper principles, it is very difficult to imagine a definitive theory that does not need in such an explanation."
The material is part of the article:
Erekaev of quantum cosmology // Modern cosmology: philosophical horizons. - M
Among them: superstring theory, loop theory of quantum gravity, dynamic triangulation models, Regge calculus models, causal set models, twistor theory, non-commutative geometry, models inspired by condensed matter physics, induced gravity, etc.
Extensive lists of literature on these issues can be found, for example, in the already mentioned books by B. Green.
See the words of S. Hawking already quoted above, as well as: Forts of the state of matter on Earth and in space. – Advances in physical sciences. – 2009. - T. 179, No. 6. – p. 653-687.
A description of the creation of string theory and its features can be read in the books published by us:
1) Weinberg S. Dreams of a final theory (summary)
2) Green B. Elegant Universe
3) Green B. Fabric of space
Today we can already say that this statement is not generally accepted, since the string is a special case p-brane, i.e. 1-brane.
Achucarro A., Martins C. J.A. P. Cosmic strings - arXiv: 0811.1277. – Vol.1. – 8 Nov, 2008; Meyerovich properties of cosmic strings. – Advances in physical sciences. – T.171., No. 10. – 2001. – S..
The latter represents one of the problems of the theory. A critical analysis of string theory can be found, for example, in: Smolin L. Trouble with physics: the rise of string theory, the decline of science and what follows. - Penguin Book, London, 2007. – Translation and other works.
S. Weinberg: “The young theorist from CERN Gabriele Veneziano was able to simply guess the formula that determined the scattering probabilities...” (Dreams about the final theory. - p. 166).
“Strings represent material objects...” Veneziano G. The myth of the beginning of time - In the world of science. – 2www. *****/article/2296).
True, now the predicate of elementaryity passes to the strings themselves.
Weinberg S. Dreams about the final theory. – M., 2004. – p. 167.
These words belong to A. Wheeler.
This program dates back to a policy article by V. Clifford and has a rich history.
Modern fundamental physics, apparently, should emphasize more and more clearly anthropomorphic nature its observer, who is its source. This is, among other things, driven by one of the fairly fundamental research disciplines - the search for new forms of life in the Universe, in particular, within the framework of the ongoing SETI project.
Polchinski J. Dirichlet Branes and Ramond-Ramond Charges - Phys. Rev. Lett., 75(26): 4724
Green B. Elegant Universe - M., 2005. - p.242
In this case, it does not matter what the scale of this locality is.
This option is possible only in the above case of the possible total quantum nature of the Universe, including its modern large-scale state.
And in an inflationary scenario, it should be even more global (larger-scale) and act within the entire inflationary inflated metaspace.
This is the case, at least within the framework of quantum field theory.
And branes in the latest versions of TSS.
Kaluza proposed to consider the 5th folded dimension as a source of electric charge.
It is possible that it is such, and maybe even of a greater number of dimensions.
Green B. Elegant Universe - M., 2005. - p.241.
Right there. – P.242.
Weinberg S. Dreams about the final theory - M., 2004. - p. 184.
