Fundamental interactions 1. Types of fundamental interactions in physics

The ability to interact is the most important and integral property of matter. It is interactions that ensure the unification of various material objects of the mega-, macro- and microworld into systems. All famous modern science forces are reduced to four types of interactions, which are called fundamental: gravitational, electromagnetic, weak and strong.

Gravitational interaction first became the object of study of physics in the 17th century. I. Newton's theory of gravity, which is based on the law universal gravity, became one of the components classical mechanics. The law of universal gravitation states: between two bodies there is an attractive force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them (2.3). Any material particle is a source of gravitational influence and experiences it on itself. As the mass increases, gravitational interactions increase, i.e., the greater the mass of the interacting substances, the stronger the gravitational forces. The forces of gravity are forces of attraction. Recently, physicists have suggested the existence of gravitational repulsion, which acted in the very first moments of the existence of the Universe (4.2), but this idea has not yet been confirmed. Gravitational interaction is the weakest currently known. The gravitational force acts on very long distances, its intensity decreases with increasing distance, but does not disappear completely. It is believed that the carrier of gravitational interaction is hypothetical particle graviton. In the microworld, gravitational interaction does not play a significant role, but in macro- and especially mega-processes it plays a leading role.

Electromagnetic interaction became the subject of study in physics of the 19th century. The first unified theory of the electromagnetic field was the concept of J. Maxwell (2.3). Unlike the gravitational force, electromagnetic interactions exist only between charged particles: the electric field is between two stationary charged particles, the magnetic field is between two moving charged particles. Electromagnetic forces can be either attractive or repulsive forces. Likely charged particles repel, oppositely charged particles attract. The carriers of this type of interaction are photons. Electromagnetic interaction manifests itself in the micro-, macro- and mega-worlds.

In the middle of the 20th century. was created quantum electrodynamics – a theory of electromagnetic interaction that satisfied the basic principles quantum theory and the theory of relativity. In 1965, its authors S. Tomanaga, R. Feynman and J. Schwinger were awarded the Nobel Prize. Quantum electrodynamics describes the interaction of charged particles - electrons and positrons.

Weak interaction was discovered only in the 20th century, in the 1960s. a general theory of weak interaction was constructed. The weak force is associated with the decay of particles, so its discovery followed only after the discovery of radioactivity. When observing the radioactive decay of particles, phenomena were discovered that seemed to contradict the law of conservation of energy. The fact is that during the decay process, part of the energy “disappeared.” Physicist W. Pauli suggested that during the process of radioactive decay of a substance, a particle with high penetrating power is released along with an electron. This particle was later named "neutrino". It turned out that as a result of weak interactions, the neutrons that make up the atomic nucleus decay into three types of particles: positively charged protons, negatively charged electrons and neutral neutrinos. The weak interaction is much smaller than the electromagnetic interaction, but greater than the gravitational interaction, and unlike them, it spreads over small distances - no more than 10-22 cm. That is why the weak interaction was not observed experimentally for a long time. The carriers of the weak interaction are bosons.

In the 1970s a general theory of electromagnetic and weak interaction was created, called theory of electroweak interaction. Its creators S. Weinberg, A. Salam and S. Glashow received the Nobel Prize in 1979. The theory of electroweak interaction considers two types of fundamental interactions as manifestations of a single, deeper one. Thus, at distances of more than 10-17 cm, the electromagnetic aspect of phenomena predominates, at smaller distances of to the same degree Both the electromagnetic and weak aspects are important. The creation of the theory under consideration meant that, united in classical physics XIX century, within the framework of the Faraday-Maxwell theory, electricity, magnetism and light in the last third of the XX century. supplemented by the phenomenon of weak interaction.

Strong interaction was also discovered only in the 20th century. It holds protons in the nucleus of an atom, preventing them from scattering under the influence of electromagnetic repulsive forces. Strong interaction occurs at distances of no more than 10-13 cm and is responsible for the stability of nuclei. The nuclei of elements at the end of the periodic table are unstable because their radius is large and, accordingly, the strong interaction loses its intensity. Such nuclei are subject to decay, which is called radioactive. Strong interaction is responsible for the formation of atomic nuclei; only heavy particles participate in it: protons and neutrons. Nuclear interactions do not depend on the particle charge; the carriers of this type of interaction are gluons. Gluons are combined into a gluon field (similar to an electromagnetic field), due to which the strong interaction occurs. In its power, the strong interaction surpasses other known ones and is a source of enormous energy. An example of strong interaction is thermonuclear reactions in the Sun and other stars. The principle of strong interaction was used to create hydrogen weapons.

The theory of strong interaction is called quantum chromodynamics. According to this theory, the strong interaction is the result of the exchange of gluons, which results in the connection of quarks in hadrons. Quantum chromodynamics continues to develop, and although it cannot yet be considered a complete concept of the strong interaction, nevertheless, this physical theory has a solid experimental basis.

In modern physics the search continues unified theory, which would make it possible to explain all four types of fundamental interactions. Creation similar theory would also mean the construction of a unified concept of elementary particles. This project was called the “Great Unification”. The basis for the belief that such a theory is possible is the fact that at short distances (less than 10-29 cm) and at high energies (more than 1014 GeV) electromagnetic, strong and weak interactions are described in the same way, which means their nature is common. However, this conclusion is still only theoretical; it has not yet been possible to verify it experimentally.

Various competing Grand Unified theories interpret cosmology (4.2) differently. For example, it is assumed that at the moment of the birth of our Universe, conditions existed in which all four fundamental interactions manifested themselves in the same way. Creating a theory that explains all four types of interactions on a unified basis will require a synthesis of the theory of quarks, quantum chromodynamics, modern cosmology and relativistic astronomy.

However, the search for a unified theory of four types of fundamental interactions does not mean that the emergence of other interpretations of matter is impossible: the discovery of new interactions, the search for new elementary particles, etc. Some physicists express doubts about the possibility of a unified theory. Thus, the creators of synergetics I. Prigogine and I. Stengers in the book “Time, Chaos, Quantum” write: “the hope for building such a “theory of everything” from which a complete description could be derived physical reality, will have to be abandoned,” and justify their thesis by the laws formulated within the framework of synergetics (7.2).

Conservation laws played an important role in understanding the mechanisms of interaction of elementary particles, their formation and decay. In addition to the conservation laws operating in the macroworld (the law of conservation of energy, the law of conservation of momentum and the law of conservation of angular momentum), new ones were discovered in the physics of the microworld: the law of conservation of baryon, lepton charges, strangeness, etc.

Each conservation law is associated with some kind of symmetry in the surrounding world. In physics, symmetry is understood as invariance, the immutability of a system relative to its transformations, that is, relative to changes in a number of physical conditions. German mathematician Emma Noether established a connection between the properties of space and time and the conservation laws of classical physics. A fundamental theorem of mathematical physics, called Noether's theorem, states that from the homogeneity of space the law of conservation of momentum follows, from the homogeneity of time the law of conservation of energy follows, and from the isotropy of space the law of conservation of angular momentum follows. These laws are fundamental in nature and are valid for all levels of existence of matter.

The law of conservation and transformation of energy states that energy does not disappear and does not appear again, but only passes from one form to another. The law of conservation of momentum postulates the constant momentum of a closed system over time. The law of conservation of angular momentum states that the angular momentum of a closed-loop system remains constant over time. Conservation laws are a consequence of symmetry, i.e. invariance, immutability of the structure of material objects relative to transformations, or changes in the physical conditions of their existence.

The ability to interact is the most important and integral property of matter. It is interactions that ensure the unification of various material objects of the mega-, macro- and microworld into systems. All forces known to modern science come down to four types of interactions, which are called fundamental: gravitational, electromagnetic, weak and strong.

Gravitational interaction first became the object of study of physics in the 17th century. I. Newton's theory of gravity, which is based on the law of universal gravitation, has become one of the components of classical mechanics. Any material particle is a source of gravitational influence and experiences it on itself. As mass increases, gravitational interactions increase, i.e. The greater the mass of interacting substances, the stronger the gravitational forces. The forces of gravity are forces of attraction. Gravitational interaction is the weakest currently known. The gravitational force acts over very large distances; its intensity decreases with increasing distance, but does not disappear completely. It is believed that the carrier of gravitational interaction is the hypothetical particle graviton. In the microworld, gravitational interaction does not play a significant role, but in macro- and especially mega-processes it plays a leading role.

Electromagnetic interaction became the subject of study in physics of the 19th century. The first unified theory of the electromagnetic field was the concept of J. Maxwell. Electromagnetic interactions exist only between charged particles: the electric field is between two stationary charged particles, the magnetic field is between two moving charged particles. Electromagnetic forces can be either attractive or repulsive forces. Likely charged particles repel, oppositely charged particles attract. The carriers of this type of interaction are photons. Electromagnetic interaction manifests itself in the micro-, macro- and mega-worlds.

In the middle of the 20th century. was created quantum electrodynamics– the theory of electromagnetic interaction, which describes the interaction of charged particles - electrons and positrons. In 1965, its authors S. Tomanaga, R. Feynman and J. Schwinger were awarded the Nobel Prize.

Weak interaction was discovered only in the 20th century, in the 60s. a general theory of weak interaction was constructed. The weak force is associated with the decay of particles, so its discovery followed only after the discovery of radioactivity. Physicist W. Pauli suggested that during the process of radioactive decay of a substance, a particle with high penetrating power is released along with an electron. This particle was later named "neutrino". It turned out that as a result of weak interactions, the neutrons that make up the atomic nucleus decay into three types of particles: positively charged protons, negatively charged electrons and neutral neutrinos. The weak interaction is much smaller than the electromagnetic interaction, but greater than the gravitational one, and unlike them, it propagates over small distances - no more than 10–22 cm. That is why the weak interaction has not been observed experimentally for a long time. The carriers of the weak interaction are bosons.

In the 70s XX century a general theory of electromagnetic and weak interaction was created, called theory of electroweak interaction. Its creators S. Weinberg, A. Sapam and S. Glashow received the Nobel Prize in 1979. The theory of electroweak interaction considers two types of fundamental interactions as manifestations of a single, deeper one. Thus, at distances greater than 10–17 cm, the electromagnetic aspect of phenomena predominates; at shorter distances, both the electromagnetic and weak aspects are equally important. The creation of the theory under consideration meant that, united in classical physics of the 19th century, within the framework of the Faraday–Maxwell theory, electricity, magnetism and light, in the last third of the 20th century. supplemented by the phenomenon of weak interaction.

Strong interaction was also discovered only in the 20th century. It holds protons in the nucleus of an atom, preventing them from scattering under the influence of electromagnetic repulsive forces. Strong interaction occurs at distances of no more than 10–13 cm and is responsible for the stability of nuclei. The kernels of the elements located at the end of the table D.I. Mendeleev are unstable because their radius is large and, accordingly, the strong interaction loses its intensity. Such nuclei are subject to decay, which is called radioactive. Strong interaction is responsible for the formation of atomic nuclei; only heavy particles participate in it: protons and neutrons. Nuclear interactions do not depend on the charge of particles; the carriers of this type of interaction are gluons. Gluons are combined into a gluon field (similar to an electromagnetic field), due to which the strong interaction occurs. In its power, the strong interaction surpasses other known ones and is a source of enormous energy. An example of strong interaction is thermonuclear reactions in the Sun and other stars. The principle of strong interaction was used to create hydrogen weapons.

The theory of strong interaction is called quantum chromodynamics. According to this theory, the strong interaction is the result of the exchange of gluons, which results in the connection of quarks in hadrons. Quantum chromodynamics continues to develop; it cannot yet be considered a complete concept of the strong interaction, but it has a solid experimental basis.

In modern physics, the search continues for a unified theory that would explain all four types of fundamental interactions. The creation of such a theory would also mean the construction of a unified concept of elementary particles. This project was called the “Great Unification”. The basis for the belief that such a theory is possible is the fact that at short distances (less than 10–29 cm) and at high energies (more than 10 14 GeV), electromagnetic, strong and weak interactions are described in the same way, which means their nature is common. However, this conclusion is only theoretical; it has not yet been possible to verify it experimentally.

Conservation laws played an important role in understanding the mechanisms of interaction of elementary particles, their formation and decay. In addition to the conservation laws operating in the macroworld (the law of conservation of energy, the law of conservation of momentum and the law of conservation of angular momentum), new ones were discovered in the physics of the microworld: the law of conservation of baryon, lepton charges, etc.

In the second half of the 20th century, with the creation of charged particle accelerators, truly amazing results were obtained in physics. Many new subatomic particles have been discovered. New particles are usually discovered by observing the scattering reactions of already known particles. To do this, accelerators collide particles with as much energy as possible, and then study the products of their interaction.

The world of subatomic particles is truly diverse. To the already known particles from which atoms and molecules are built (protons, neutrons, electrons), many others were added: muons, mesons, hyperons, antiparticles, various neutral particles, etc. Among subatomic particles, particles were also discovered that are in the matter around us practically never occur - resonances. Their life time is the smallest fractions of a second. After this extremely short time, they disintegrate into ordinary particles.

In the 1950s–1970s. physicists were completely baffled by the number, variety and strangeness of the newly discovered subatomic particles. If in the late 1940s. While 15 elementary particles were known, at the end of the 1970s there were already about 400. It is completely unclear why there are so many particles. Are elementary particles just random fragments of matter, or is there perhaps some order hidden behind their interactions? The development of physics in subsequent decades has shown that the world of subatomic particles is characterized by a deep structural order. This order is based on fundamental physical interactions.

10.1. Fundamental physical interactions

10.1.1. The concept of fundamental physical interaction.

In his Everyday life a person is faced with many forces acting on bodies: the force of wind or water flow; air pressure; powerful burst of explosive chemical substances; human muscular strength; weight of objects; pressure of light quanta; attraction and repulsion of electrical charges; seismic waves, sometimes causing catastrophic destruction; volcanic eruptions that led to the death of civilizations

tions, etc. Some forces act directly upon contact with the body, others, such as gravity, act at a distance, through space. But, as it turned out as a result of the development of natural science, despite such great diversity, all forces operating in nature can be reduced to four fundamental interactions.

In order of increasing intensity, these fundamental interactions are represented in the following way: gravitational interaction; weak interaction; electromagnetic interaction; strong interaction. It is these interactions that are ultimately responsible for all changes in nature; they are the source of all transformations of material bodies and processes. Each of the four fundamental interactions has similarities with the other three and at the same time its differences.

First of all, it should be said about what is common to these fundamental interactions. In other words: how does modern physics understand the essence of interaction? As already noted, back in the middle of the 19th century. with the creation of the theory of the electromagnetic field, it became clear that the transfer of interaction does not occur instantly (the principle of long-range action), but at a finite speed through some intermediary - a field continuously distributed in space (the principle of short-range action). The speed of propagation of the electromagnetic field is equal to the speed of light (see 8.1.4).

However, already in the first quarter of the 20th century, with the advent of quantum mechanics, the understanding of the physical field deepened significantly. In the light of quantum-wave dualism, any field is not continuous, but has a discrete structure; certain particles, quanta of this field, must correspond to it. For example, the quanta of the electromagnetic field are photons. When charged particles exchange photons with each other, this results in the appearance of an electromagnetic field. Photons are carriers of electromagnetic interaction.

Similarly, other types of fundamental interactions have their own fields and corresponding particles that carry this field interaction. The study of specific properties, patterns of these fields and particles - carriers of fundamental interactions - is the main task modern physics.

10.1.2. Gravity.

Gravity was the first of the four fundamental interactions to become the subject of scientific research. Created in the 17th century. Newton's theory of gravity (law of universal gravitation) made it possible for the first time to understand the true role of gravity as a force of nature (see 6.4.1). The relativistic theory of gravity is General Relativity, which in the region of weak gravitational fields transforms into Newton's theory of gravitation.

Gravity has a number of features that sharply distinguish it from other fundamental interactions. The most surprising feature of gravity is its low intensity. Gravitational interaction is 1039 times less than the force of interaction of electric charges. Therefore, it is usually not taken into account in describing the interactions of elementary particles. In the microworld, gravity is negligible.

1 If the dimensions of a hydrogen atom were determined by gravity, and not by the interaction between electric charges, then the radius of the lowest (closest to the nucleus) electron orbit would exceed the radius of the observable part of the Universe.

How can such a weak force become the dominant force in the Universe? It's all about the second amazing feature of gravity - its universality. Nothing in the Universe can escape gravity. Each particle experiences the action of gravity and is itself a source of gravity, causing gravitational attraction. Gravity increases as larger and larger accumulations of matter form. And although the attraction of one atom is negligible, the resulting force of attraction from all atoms can be significant. This also manifests itself in everyday life: we feel gravity because all the atoms of the Earth together attract us.

In addition, gravity is a long-range force of nature. This means that, although the intensity of gravitational interaction decreases with distance, it spreads in space and can affect bodies very distant from the source. On an astronomical scale, gravitational interactions tend to play a major role. Thanks to long-range action, gravity prevents the Universe from falling apart: it holds planets in orbits, stars in galaxies, galaxies in clusters, clusters in the Metagalaxy.

The gravitational force acting between particles is always an attractive force: it tends to bring the particles closer together. Gravitational repulsion has never been observed before.

1 Although in the traditions of quasi-scientific mythology there is a whole area called levitation - the search for “facts” of antigravity.

It is very difficult to develop ideas about the quantization of gravity. Nevertheless, according to general theoretical and physical concepts, gravitational interaction should obey quantum laws just like electromagnetic. (Otherwise, multiple contradictions arise in the foundations of modern physics, including those related to the uncertainty principle, etc.) In this case, the gravitational interaction must correspond to a field with a gravitational quantum - the graviton (a neutral particle with zero rest mass and spin 2). Quantum gravity leads to the emergence of the idea of ​​discrete properties of space-time, the concepts of elementary length, space quantum r ≈ 10-33 cm, and an elementary time interval, time quantum t ≈ 10-43 s. A consistent quantum theory of gravity has not yet been created.

Unfortunately, the capabilities of modern experimental gravitational physics and astronomy do not allow us to detect quantum effects gravity due to their extreme weakness. Nevertheless, phenomena in which the quantum properties of gravity are manifested apparently exist. They manifest themselves in very strong gravitational fields, where quantum processes of particle creation occur (singularity point, initial moments the origin of the Universe, gravitational collapse, black holes (see 11.4 and 11.7)).

10.1.3. Electromagnetism.

Electrical forces are much larger than gravitational forces, so, unlike the weak gravitational interaction, electrical forces acting between bodies of normal size can be easily observed. Electromagnetism has been known to people since time immemorial ( auroras, lightning flashes, etc.). But for a long time, electrical and magnetic phenomena were studied independently of each other. And only in the middle of the 19th century. J. C. Maxwell combined the teachings of electricity and magnetism into a unified theory of electromagnetic

no field. And the existence of the electron (a unit of electrical charge) was firmly established in the 1890s. But not all elementary particles are carriers of electric charge. Electrically neutral, for example, photon and neutrino. This is how electricity differs from gravity. All material particles create a gravitational field, while with electrical magnetic field Only charged particles are bound.

Like electric charges, like magnetic poles repel, and opposite ones attract. But unlike electric charges, magnetic poles do not occur individually, but only in pairs - a north pole and a south pole. Since ancient times, attempts have been known to obtain, by dividing a magnet, only one isolated magnetic pole - a monopole. But they all ended in failure. Perhaps the existence of isolated magnetic poles in nature is excluded? There is no definite answer to this question yet. Some modern theories allow the possibility of the existence of a magnetic monopole (see 10.3.5).

The electromagnetic field of stationary or uniformly moving charged particles is inseparable from these particles. But when accelerated movement particles, the electromagnetic field “breaks away” from them and participates in an independent form electromagnetic waves. In this case, radio waves (103-1012 Hz), infrared radiation(1012 - 3.7 1014 Hz), visible light (3.7 1014 - 7.5 1014 Hz), ultraviolet radiation (7.5 1014 - 3 1017 Hz), X-ray radiation (3 1017 - 3 1020 Hz) and gamma -radiation (3 102-1023 Hz) are electromagnetic waves of various frequencies. Moreover, there are no sharp boundaries between neighboring ranges (the length of an electromagnetic wave and its frequency are related by the relation: λ = c/v, where λ is the wavelength, v is the frequency, c is the speed of light).

Electromagnetic interaction (like gravity) is long-range, it is noticeable at large distances from the source. Like gravity, it obeys the law inverse squares. Electromagnetic interaction manifests itself at all levels of matter - in the megaworld, macroworld and microworld.

The Earth's electromagnetic field extends far into outer space, the powerful field of the Sun fills the entire Solar System; There are also galactic electromagnetic fields. At the same time, electromagnetic interaction determines the structure of atoms and molecules (positively charged nucleus and negatively charged electrons). It is responsible for the vast majority of physical and chemical phenomena and processes (with the exception of nuclear ones): elastic forces, friction, surface tension, it determines the properties states of aggregation substances, chemical transformations, optical phenomena, ionization phenomena, many reactions in the world of elementary particles, etc.

10.1.4. Weak interaction.

Physics has moved slowly towards identifying the existence of the weak interaction. The weak interaction is responsible for particle decays. Therefore, its manifestation was encountered during the discovery of radioactivity and the study of beta decay (see 8.1.5).

Beta decay was found to be highly strange feature. It seemed that in this decay the law of conservation of energy was violated, that part of the energy disappeared somewhere. To “save” the law of conservation of energy, W. Pauli suggested that during beta decay, another particle flies out along with the electron, taking with it the missing energy. It is neutral and has an unusually high penetrating ability, as a result of which it could not be observed. E. Fermi called the invisible particle “neutrino”.

But predicting neutrinos is only the beginning of the problem, its formulation. It was necessary to explain the nature of neutrinos; there remained a lot of mystery here. The fact is that electrons and neutrinos were emitted by unstable nuclei, but it was known that there were no such particles inside the nuclei. How did they arise? It turned out that the neutrons included in the nucleus, left to their own devices, after a few minutes decay into a proton, electron and neutrino. What forces cause such disintegration? The analysis showed that known forces cannot cause such a disintegration. It was apparently generated by some other, unknown force, which corresponds to some “weak interaction”.

The weak interaction is much smaller in magnitude than all interactions except gravitational interaction. Where it is present, its effects are overshadowed by the electromagnetic and strong interactions. In addition, the weak interaction extends over very small distances. Radius of the weak

interaction is very small (10-16 cm). Therefore, it cannot influence not only macroscopic, but even atomic objects and is limited to subatomic particles. In addition, compared to the electromagnetic and strong interactions, the weak interaction is extremely slow.

When the avalanche-like discovery of many unstable subnuclear particles began, it was discovered that most of them participate in weak interactions. The weak interaction plays a very important role in nature. It is an integral part of thermonuclear reactions in the Sun and stars, providing the synthesis of pulsars and explosions supernovae, synthesis of chemical elements in stars, etc.

The theory of weak interaction was created in the late 1960s. (see 10.3.3). The creation of this theory was a major step towards the unity of physics.

10.1.5. Strong interaction.

The last in the series of fundamental interactions is the strong interaction, which is a source of enormous energy. The most typical example of the energy released strong interaction, - Sun. In the depths of the Sun and stars, thermonuclear reactions continuously occur, caused by strong interaction (with significant participation of weak interaction). But man has also learned to cause strong interaction: created H-bomb, controlled thermonuclear reaction technologies have been designed and improved.

Physics came to the idea of ​​the existence of strong interaction during the study of the structure of the atomic nucleus. Some force must hold the positively charged protons in the nucleus, preventing them from flying away under the influence of electrostatic repulsion. Gravity is too weak to provide this; Obviously, some kind of interaction is necessary, and stronger than electromagnetic. It was subsequently discovered and called the “strong interaction.”

It turned out that, although the strong interaction significantly exceeds all other fundamental interactions in its magnitude, it is not felt outside the nucleus. The strong interaction manifests itself at a distance determined by the distance

core measures, i.e. approximately 10-13 cm. Main function strong interaction in nature - the creation of strong bonds between nucleons (protons and neurons) in the nuclei of atoms. In this case, the collision of nuclei or nucleons with high energies leads to a variety of nuclear reactions, including reactions thermonuclear fusion on the Sun, which is the main source of energy on Earth.

At the same time, it turned out that not all particles experience strong interaction. Thus, protons and neutrons experience it, but electrons, neutrinos and photons are not subject to it. Usually only heavy particles participate in strong interactions.

The theoretical explanation of the nature of the strong interaction has been difficult to develop. A breakthrough appeared only in the early 1960s, when the quark model was proposed. In this theory, neutrons and protons are considered not as elementary particles, but as composite systems built from quarks (see 10.3.2).

Thus, in fundamental physical interactions the difference between long-range and short-range forces is clearly visible. On the one hand, interactions of an unlimited radius (gravity, electromagnetism), and on the other, of a small radius (strong and weak). The world of physical processes unfolds within the boundaries of these two polarities and embodies the unity of the extremely small and the extremely large - the microworld and the megaworld, elementary particle and the entire Universe.

10.1.6. The problem of the unity of physics.

Knowledge is a generalization of reality, and therefore the goal of science is the search for unity in nature, linking disparate fragments of knowledge into a single picture. In order to create such unified system, you need to open the deep connecting link between various industries knowledge. Finding such connections is one of the main tasks of scientific research. Whenever it is possible to establish such new connections, the understanding of the surrounding world deepens significantly, new ways of knowing are formed that point the way to previously unknown phenomena.

Establishing deep connections between different areas of nature is both a synthesis of knowledge and new method, guiding Scientific research on unbeaten roads. Thus, Newton’s identification of the connection between the attraction of bodies in terrestrial conditions and the movement of planets marked the birth of classical mechanics, on the basis of which the technological basis of modern civilization is built. The establishment of a connection between the thermodynamic properties of gas and the chaotic movement of molecules put the atomic-molecular theory of matter on a solid basis. In the middle of the last century, Maxwell created a single electromagnetic theory, covering both electrical and magnetic phenomena. Then in the 1920s. Einstein attempted to combine electromagnetism and gravity into a single theory.

But by the middle of the 20th century. The situation in physics changed radically: two new fundamental interactions were discovered - strong and weak. While creating unified physics we no longer have to reckon with two, but with four fundamental interactions. This somewhat cooled the ardor of those who hoped for a quick solution to the problem of the unity of physics. However, the plan itself was not seriously questioned.

In modern theoretical physics, the dominant point of view is that all four (or at least three) interactions are phenomena of the same nature and their unified nature can be found theoretical description. The prospect of creating a unified theory of the world of physical elements (based on a single fundamental interaction) is the highest ideal of modern physics. This main dream physicists. But for a long time it remained only a dream, and a very vague one.

However, in the second half of the 20th century. there were prerequisites for the fulfillment of a dream and the confidence that this was by no means a matter of the distant future. It looks like it could soon become a reality. The decisive step towards a unified theory was taken in the 1960s and 1970s. with the creation first of the theory of quarks, and then of the theory of electroweak interaction. There is reason to believe that we are on the threshold of a more powerful and deeper unification than ever before. There is a growing belief among physicists that the contours of a unified theory of strong, weak and electromagnetic interactions—the Grand Unification—are beginning to emerge. And just around the corner is a unified theory of all fundamental interactions - Supergravity.

10.2. Classification of elementary particles

10.2.1. Characteristics of subatomic particles.

In the 20th century, especially in its second half, a new deep layer of the structural organization of matter was discovered - the world of elementary particles. This name is not, however, accurate. Under the elementary particle in exact value further understand the indecomposable “building blocks” of matter that make up its structural organization. In fact, most of the discovered particles turned out to be systemic formations consisting of even more elementary particles. Therefore, it is more correct to say that “the world of elementary particles is a special level of organization of matter - subnuclear matter, from the forms of which the nuclei and atoms of matter, physical fields are structured. But since the term “elementary particles” is established and widely used, we will use it in the meaning of “subnuclear matter”.

The study of elementary particles has shown that they are born and destroyed when interacting with other elementary particles. In addition, they can spontaneously disintegrate. All these transformations of particles (decay, birth, destruction) are realized through successive acts of absorption and emission of particles.

The properties of elementary particles are diverse. Thus, each particle has its own antiparticle, which differs from it only in the sign of its charge. For particles with zero values ​​of all charges, the antiparticle coincides with the particle (for example, a photon). Each elementary particle is characterized by its own set of values ​​of certain physical quantities. These quantities include: mass, electric charge, spin, particle lifetime, magnetic moment, spatial parity, lepton charge, baryon charge, etc.

General characteristics of all particles: mass, lifetime, spin. When they talk about the mass of a particle, they mean its rest mass, since it does not depend on the state of motion. A particle with zero rest mass moves at the speed of light (photon). No two particles have the same mass. The electron is the lightest particle with a non-zero rest mass. The proton and neutron are almost 2000 times heavier than the electron. And the heaviest elementary particle produced in accelerators (Z-boson) has a mass 200,000 times greater than the mass of an electron.

An important characteristic of a particle is spin—the particle’s own angular momentum. Thus, a proton, neutron and electron have a spin of 1/2, and the spin of a photon is 1. Particles with a spin of 0.3/2.2 are known. A particle with spin 0 looks the same at any angle of rotation. A particle with spin 1 takes the same form after a full rotation of 360°. A particle with spin 1/2 takes on its previous appearance after a rotation of 720°, etc. A particle with spin 2 (hypothetical graviton) returns to its previous position after half a turn (180°). Depending on the spin, all particles are divided into two groups: bosons - particles with integer spins 0, 1 and 2; fermions are particles with half-integer spins (1/2, 3/2). Particles with spin greater than 2 may not exist at all.

Particles are also characterized by their lifetime. Based on this criterion, particles are divided into stable and unstable. Stable particles are the electron, proton, photon and neutrino. (The question of the stability of the proton has not yet been fully resolved. It is possible that it decays in t = 1031 years.) The neutron is stable when it is in the nucleus of an atom, but a free neutron decays in about 15 minutes. All other known particles are unstable; their lifetime ranges from a few microseconds to 10-24 s. The most unstable particles are resonances. Their life time is 10-22—10-24 s.

A major role in the physics of elementary particles is played by conservation laws that establish equality between certain combinations of quantities characterizing the initial and final states of the system. The arsenal of conservation laws in quantum physics is greater than in classical physics. It was replenished with laws of conservation of various parities (spatial, charge), charges (leptonic, baryon, etc.), internal symmetries characteristic of one or another type of interaction. Moreover, the more intense the interaction, the more conservation laws it corresponds to, i.e. Moreover, it is symmetrical. In quantum physics, conservation laws are always prohibition laws. But if some process is allowed by conservation laws, then it necessarily occurs in reality.

The pinnacle of the development of ideas about conservation laws in quantum physics is the concept of spontaneous symmetry breaking, i.e. the existence of stable asymmetric solutions for certain types of problems. In the 1960s the so-called violation of the combined

clarity. In other words, it was discovered that in the microcosm there are absolute differences between particles and antiparticles, between “right” and “left”, between past and future (the arrow of time, or the irreversibility, of microprocesses, and not just macroprocesses).

Isolation and knowledge of the characteristics of individual subatomic particles is an important, but only the initial stage of understanding their world. At the next stage, we still need to understand what the role of each individual particle is, what its functions are in the structure of matter.

Physicists have found that, first of all, the properties of a particle are determined by its ability (or inability) to participate in strong interactions. Particles participating in strong interactions form a special class and are called hadrons. Particles that participate predominantly in weak interactions and do not participate in strong interactions are called leptons. In addition, there are particles that are carriers of interactions.

Let's consider the properties of these main types of particles.

10.2.2. Leptons.

Leptons behave like point objects, showing no internal structure even at ultra-high energies. They appear to be elementary (in the proper sense of the word) objects, i.e. they are not made up of any other particles. Although leptons may or may not have an electrical charge, they all have a spin of 1/2.

Among leptons, the most famous is the electron. The electron is the first elementary particle to be discovered. The electron is the carrier of the smallest mass and the smallest electric charge (not counting quarks) in nature.

Another well-known lepton is the neutrino. Neutrinos, along with photons, are the most common particles in the Universe. The Universe can be imagined as a boundless photon-neutrino ocean, in which islands of atoms are occasionally found. But despite the prevalence of neutrinos, they are very difficult to study. As we have already noted, neutrinos are almost elusive and have enormous penetrating power, especially at low energies. Without participating in either strong or electromagnetic interactions, they penetrate through matter as if it were not there at all. Neutrinos are some kind of “ghosts” physical world. On the one hand, this complicates their detection, and on the other, it creates the opportunity to study the internal structure of stars, galactic nuclei, quasars, etc.

One of the interesting pages in the history of the study of neutrinos is related to the question of their mass: whether or not a neutrino has a rest mass. The theory allows that, unlike a photon, a neutrino can have a small rest mass. If the neutrino really has a rest mass (estimated from 0.1 eV to 10 eV), then this entails fundamental consequences in the theory of the Grand Unification, cosmology, and astrophysics. The “chase” of physicists for the mass of an elusive particle, which has been going on for almost 60 years, seems to be coming to an end. There is reason to believe that the issue will be finally resolved at new experimental facilities (Japan, Italy) in the coming years.

Muons are quite widespread in nature, accounting for a significant portion of cosmic radiation. The muon is one of the first known unstable subatomic particles, discovered in 1936. In all respects, the muon resembles an electron: it has the same charge and spin, participates in the same interactions, but has a larger mass and is unstable. In about two millionths of a second, the muon decays into an electron and two neutrinos. Penetrating into matter, muons interact with the nuclei and electrons of atoms and form unusual compounds. A positive muon, attaching an electron to itself, forms a system similar to the hydrogen atom - muonium, the chemical properties of which are in many ways similar to the properties of hydrogen. And a negative muon can replace one of the electrons on the electron shell, forming a so-called mesoatom. In a mesoatom, muons are located hundreds of times closer to the nucleus than electrons. This allows the mesoatom to be used to study the shape and size of the nucleus.

At the end of the 1970s. A third charged lepton was discovered, called the tau lepton. This is a very heavy particle. Its mass is about 3500 that of an electron, but in all other respects it behaves like an electron and a muon.

The list of leptons expanded significantly in the 1960s. It was found that there are several types of neutrinos: electron neutrinos, muon neutrinos and may neutrinos. Thus, the total number of neutrino varieties is three, and the total number of leptons is six. Of course, each lepton has its own antiparticle; thus the total number of different leptons is 12. Neutral leptons participate only in the weak interaction; charged - in the weak and electromagnetic (see table).

10.2.3. Hadrons.

If there are only 12 leptons, then there are hundreds of hadrons. The vast majority of them are resonances, i.e. extremely unstable particles. The fact that there are hundreds of hadrons suggests that hadrons themselves are built from more fine particles.

All hadrons are found in two varieties - electrically charged and neutral. The most famous and widespread hadrons are the neutron and proton. The remaining hadrons quickly decay. Hadrons are divided into two classes. This is a class of baryons (heavy particles) (proton, neutron, hyperons and baryon resonances) and a large family of lighter mesons (muons, bosonic resonances, etc.).

The existence and properties of most known hadrons were established in accelerator experiments. Discovery of a wide variety of hadrons in the 1950s and 1960s. physicists were extremely puzzled. But over time, particles were classified by mass, charge and spin. Gradually a more or less clear picture began to emerge. Specific ideas have emerged on how to systematize the chaos of empirical data and reveal the mystery of hadrons in a holistic way. scientific theory. The decisive step was taken in 1963, when the quark model of hadrons was proposed.

10.2.4. Particles are carriers of interactions.

The list of known particles is not limited to leptons and hadrons, which form the building material of matter. There is another type of particles that are not the building material of matter, but directly provide fundamental interactions, i.e. form a kind of “glue” that prevents matter from falling apart.

The carrier of electromagnetic interaction is the photon. The theory of electromagnetic interaction is represented by quantum electrodynamics (see 10.3.1).

Gluons (there are eight of them) are carriers of the strong interaction between quarks. The latter, thanks to gluons, are associated in pairs or triplets (see 10.3.2 and 10.3.4).

The carriers of the weak interaction are three particles - W± and Z° -bosons (see 10.3.3). They were discovered only in 1983. The radius of the weak interaction is extremely small, so its carriers must be particles with large masses peace. According to the uncertainty principle, the lifetime of particles with such a large rest mass should be extremely short - only about 10-26 s.

It is suggested that the existence of a carrier of the gravitational field, the graviton, is also possible (see 10.1.2). Like photons, gravitons travel at the speed of light; therefore, these are particles with zero rest mass. But while a photon has spin 1, a graviton has spin 2. This important difference determines the direction of the force: during electromagnetic interaction, similarly charged particles (electrons) repel, and during gravitational interaction, all particles are attracted to each other.

It is especially important that each group of these interaction carriers is characterized by its own specific conservation laws. And each conservation law can be represented as a manifestation of a certain internal symmetry of the field (motion) equations. This circumstance is used to construct a unified theory of fundamental interactions.

The classification of particles into hadrons, leptons and carriers of interactions exhausts the world of subnuclear particles known to us. Each type of particle plays its role in the formation of the structure of matter, the Universe.

10.3. Particle theories

10.3.1. Quantum electrodynamics.

Quantum mechanics allows us to describe the movement of elementary particles, but not their creation or destruction, i.e. is used only to describe systems with a constant number of particles. A generalization of quantum mechanics is quantum field theory - this is the theory of systems with infinite number degrees of freedom (physical fields), taking into account the requirements of both quantum mechanics and the theory of relativity. The need for such a theory is generated by quantum-wave dualism, the existence wave properties for all particles. In quantum field theory, interaction is represented as a result of the exchange of field quanta, and field quantities are declared by operators that are associated with the acts of birth and destruction of field quanta, i.e. particles.

In the middle of the 20th century. a theory of electromagnetic interaction was created - quantum electrodynamics (QED). This is a theory of interaction of the electromagnetic field and charged particles, as well as charged particles (primarily electrons or positrons) with each other, thought out to the smallest detail and equipped with a perfect mathematical apparatus. This theory satisfies the basic principles of both quantum theory and relativity.

In QED, to describe electromagnetic interaction, the concept of a virtual photon is used, which is “seen” only by charged particles undergoing scattering. If in the classical description electrons are represented as a solid point ball, then in QED the electromagnetic field surrounding the electron is considered as a cloud of virtual photons that relentlessly follows the electron, surrounding it with energy quanta. Photons appear and disappear very quickly, and electrons do not move in space along well-defined trajectories. You can also determine the initial and end point paths - before and after scattering, but the path itself in the interval between the beginning and end of the movement remains uncertain.

Consider, for example, the act of emitting a (virtual) photon from an electron. After an electron emits a photon, it produces a (virtual) electron-positron pair, which can annihilate to form a new photon. The latter can be absorbed by the original electron, but can generate new pair etc. Thus, the electron is covered with a cloud of virtual photons, electrons and positrons, which are in a state of dynamic equilibrium.

In QED, the interaction of an electromagnetic field and a charged particle appears in the form of emission and absorption of virtual photons by the particle. And the interaction between charged particles is interpreted as the result of their exchange of photons: each charged particle emits photons, which are then absorbed by another charged particle. In addition, QED considers effects that did not exist at all in classical electrodynamics. Firstly, this is the effect of light scattering by light, i.e. interactions of photons with each other. From the QED point of view, such scattering is possible due to the interaction of photons with fluctuations of the electron-positron vacuum. And, secondly, QED predicted the birth of particle-antiparticle pairs in strong electromagnetic and gravitational fields, among which there may be a nucleon-antinucleon.

QED has been tested in a large number of very subtle experiments. Theoretical predictions and experimental test results coincide with highest precision- sometimes up to nine decimal places. Such a striking correspondence gives the right to consider QED the most advanced of the existing ones. natural science theories. For the creation of QED, S. Tomonaga, R. Feynman and J. Schwinger were awarded the Nobel Prize in 1965. Our outstanding theoretical physicist L.D. also made a great contribution to the development of QED. Landau.

Following this triumph, QED was adopted as a model for the quantum description of the other three fundamental interactions. (Of course, fields associated with other interactions must correspond to other carrier particles.) Currently, QED acts as an integral part of more general theory— a unified theory of weak and electromagnetic interactions (see 10.3.3).

10.3.2. Quark theory.

The theory of quarks is a theory of the structure of hadrons. The main idea of ​​this theory is very simple: all hadrons are built from smaller particles - quarks. Quarks carry a fractional electric charge, which is either -1/3 or +2/3 of the charge of an electron. A combination of two and three quarks can have a net charge equal to zero or unit. All quarks have spin 1/2, therefore, they are classified as fermions. The founders of the quark theory were Gell-Mann and Zweig, in order to take into account everything known in the 1960s. hadrons, introduced three types (flavors) of quarks: and (from up - upper), d (from down - lower) and s (from strange - strange).

1 The term “quark” was chosen completely arbitrarily. In the novel Finnegans Wake by J. Joyce, the hero has a dream in which seagulls rushing over a stormy sea shout in sharp voices: “Three quarks for Mr. Mark!” This approach fully corresponds to the extremely abstract nature of the concepts of modern physical theories.

In addition, each quark has an analogue of electric charge, which serves as a source of the gluon field. It was called color. If the electromagnetic field is generated by a charge of only one type, then the more complex gluon field is created by three different color charges. Each quark is “colored” in one of three possible colors, which (quite arbitrarily) were called red, green and blue. And accordingly, antiquarks are anti-red, anti-green and anti-blue.

1 As with the term “quark,” the term “color” here is chosen arbitrarily and has nothing to do with ordinary color.

Quarks can combine with each other in one of two possible ways: either in triplets or in quark-antiquark pairs. Relatively heavy particles—baryons—are made up of three quarks; The most famous baryons are the neutron and proton. For example, a proton consists of two u-quarks and one d-quark (uud), and a neutron consists of two d-quarks and one u-quark (udd). Lighter quark-antiquark pairs form particles called mesons. For example, a positive pi meson consists of a u-quark and a d¯-quark, and a negative pi-meson consists of a u¯-quark and a d-quark. To prevent this “trio” of quarks from decaying, a holding force, a kind of “glue”, is needed. And the “color charges” of the quarks are collectively compensated so that, as a result, the hadrons turn out to be “white” (or colorless).

It turned out that the interaction between neutrons and protons in the nucleus is a residual effect of the more powerful interaction between the quarks themselves. This explained why the strong force seemed so complex and why free quarks had not been discovered. When a proton “sticks” to a neutron or another proton, the interaction involves six quarks, each of which interacts with all the others. A significant part of the energy is spent on firmly “gluing” a trio of quarks, and a small part is spent on attaching two trios of quarks to each other.

The fact that all known hadrons could be obtained from various combinations of the three fundamental particles was a triumph for quark theory. But in the 1970s. New hadrons were discovered (psi particles, upsilon meson, etc.). This dealt a severe blow to the first version of the quark theory, since there was no room for a single new particle in it. All possible combinations of quarks and their antiquarks have already been exhausted. The problem was solved by introducing three new flavors. They were called charm (charm), or with; b (from beauty - beauty or charm) and t (from top - top).

So, quarks are held together as a result of strong interaction. The carriers of the latter are gluons (color charges). The field of particle physics that studies the interaction of quarks and gluons is called quantum chromodynamics. Just as quantum electrodynamics is the theory of electromagnetic interaction, quantum chromodynamics is the theory of strong interaction (see 10.3.4).

Currently, most physicists consider quarks to be truly elementary particles - point-like, indivisible and without internal structure. In this respect they resemble leptons, and it has long been assumed that there must be a deep relationship between these two distinct but structurally similar families.

1 In 1969, it was possible to obtain direct physical evidence of the existence of quarks in a series of experiments on the scattering of electrons (accelerated to high energies) by protons. The experiment showed that electron scattering occurred as if the electrons struck tiny solid inclusions and bounced off them at the most incredible angles. Such solid inclusions inside protons are quarks.
2 True, some physicists (since the number of quarks turns out to be excessively large) are tempted to assume that quarks consist of even smaller particles.

Thus, at the end of the 20th century. the most probable number of truly elementary particles (not counting carriers of fundamental interactions) is 48: leptons (6. 2) = 12 plus quarks (b. 3). 2 = 36. These 48 particles are the true “building blocks” of matter, the basis of the material organization of the world.

10.3.3. Theory of electroweak interaction.

Concepts of gauge field and spontaneous symmetry breaking. In the 1960s An outstanding event occurred in natural science: two fundamental interactions out of four in physics were combined into one. Electromagnetic and weak interactions, seemingly very different in nature, appeared as varieties of a single electroweak interaction. The picture of fundamental interactions has become somewhat simpler.

The theory of electroweak interaction in its final form was created by two independently working physicists - S. Weinberg and A. Salam. An integral part of this theory is the theory of weak interaction, which was developed simultaneously and in close connection with the theory of electroweak interaction.

The creation of the theory of electroweak interaction had a profound and decisive influence on the development of elementary particle physics in the second half of the 20th century. The main idea of ​​this theory was to describe the weak interaction in terms of the concept of a gauge field, the key to which is the concept of symmetry. It should be especially noted here that one of the fundamental ideas of physics of the second half of the 20th century. is the belief that all interactions exist only to maintain a certain set of abstract symmetries in nature. But, it would seem, what does symmetry have to do with fundamental interactions? After all, at first glance, the statement about the existence of such a connection looks far-fetched, speculative, and artificial. Let's consider this issue in more detail.

First of all, what is meant by symmetry? It is generally accepted that an object is symmetrical if it remains unchanged after one or another operation to transform it. In other words, in the very in a general sense symmetry means the invariance of the structure of an object with respect to its transformations. In relation to physics, this means that symmetry is invariance physical system(laws characterizing it, and corresponding quantities) regarding some specific transformations. (For example, the laws of electricity are symmetrical with respect to the replacement positive charges negative, and vice versa; and closed mechanical systems are symmetrical with respect to time, etc.)

It follows that a physical system in its essential properties is determined by the set (group) of its symmetric transformations. If a group of transformations is associated with a certain space endowed with a symmetric structure corresponding to the transformations, then the object itself can be represented as an element of such a space (since the transformations of the object are in this case transformations of space). In this case, the study of the symmetries of an object comes down to the study of the invariant characteristics of a given space.

A mathematical tool for analyzing symmetric transformations is group theory. So, to solve specific tasks The following approach is used. First of all, the equation specifies some vector space. Then the group of invariant transformations of such an equation is studied. Each element of the group can be associated with some transformation into vector space solutions to this equation. Knowledge of the relationships between the elements of the group and this kind of transformation allows in many cases to find solutions to the equation. And this means determining the existence of real symmetrical properties of the object with which a given space can be correlated.

1 A group in the most general sense in mathematics is understood as a non-empty set on which some binary algebraic operation is defined, the elementary unit of this set and its inverse element are defined. (In particular, in geometry, a group is the set of all orthogonal (mirror) transformations that combine a figure with itself.) Group theory as an independent field of mathematics took shape in turn of the 19th century— XX centuries (M.S. Lee and others) based on ideas that developed in the 19th century. in solution theory algebraic equations in radicals (N. Abel, E. Galois), “Erlangen program” by F. Klein, number theory (K. Gauss, etc.).

The study of symmetries of field theory equations played an important role in the development of relativistic quantum theory. In the most general terms, such symmetries are divided into external, associated with the properties of space-time, and internal, associated with the properties of elementary particles. An example of external symmetry is the symmetry of the laws of quantum objects with respect to spatial inversion (P), time reversal (T) and charge conjugation (C), i.e. replacing particles with the corresponding antiparticle. The important “CPT theorem” was proven, according to which the equations of quantum field theory do not change their form if the following transformations are simultaneously carried out:

thread a particle into an antiparticle, carry out spatial inversion (replace the particle coordinate r with -r), reverse time (replace t with -t). The experimental discovery of individual violations of this theorem for weak interactions is a prerequisite for the idea of ​​the possibility of spontaneous breaking of symmetries in the microcosm in general.

But, in addition to external ones, there are also internal symmetries associated with the properties of the particles themselves, and not with the properties of space-time. As we have already noted, each group of particles is characterized primarily by its own specific conservation laws. And each of the conservation laws is considered as a manifestation of a certain internal symmetry of the field equations. By connecting certain internal symmetries, one can, as it were, make a transition from describing the characteristics of one particle to describing the characteristics of another. Thus, by “turning off” the conservation laws inherent in electromagnetic and weak interactions in the field equations, we come to a complete identification of the proton and the neuron; they become indistinguishable from each other.

Among the internal symmetries of field equations corresponding to conservation laws, gauge symmetries play a special role. A few words about gauge symmetries in general. A system has gauge symmetry if its essential properties remain unchanged when the level, scale, or value of some physical quantity changes. For example, in physics, work depends on differences in heights, not on absolute heights; voltage - from the potential difference, and not from their absolute values, etc.

Gauge symmetry transformations can be global or local. Global transformations change the system as a whole, in its entire spatiotemporal volume. In quantum physics, this is expressed in the fact that at all points in space-time, the values ​​of the wave function undergo the same change. Local gauge transformations are transformations that vary from point to point. In this case wave function at each point is characterized by its own special phase, which corresponds to a specific particle.

The analysis showed that in quantum field theory the global gauge transformation can be turned into a local one. In this case, a term necessarily appears in the equations of motion that takes into account the interaction of particles. This means that to communicate and maintain symmetry at each point in space, new force fields are needed - gauge ones. In other words, gauge symmetry presupposes the existence of vector gauge fields, the quanta of which particles exchange, realizing this interaction. Thus, force fields can be considered as a means by which local gauge symmetries inherent in nature are created in nature. The significance of the concept of gauge symmetry is that on its basis all four fundamental interactions, considered as gauge fields, are theoretically modeled.

Electromagnetism has the simplest gauge symmetry. In other words, the electromagnetic field is not just a certain type of force field existing in nature, but a manifestation of the simplest (compatible with the principles special theory relativity) gauge symmetry, in which gauge transformations correspond to changes in potential from point to point.

The doctrine of electromagnetism has evolved over centuries on the basis of painstaking empirical research, but it turns out that the results of these studies can be deduced purely theoretically, based on knowledge of only two symmetries - the simplest local gauge symmetry and the so-called Lorentz-Poincaré symmetry of the special theory of relativity. Based only on the existence of these two symmetries, without conducting a single experiment on electricity and magnetism, one can construct Maxwell’s equations, derive all the laws of electromagnetism, prove the existence of radio waves, the possibility of creating a dynamo, etc.

To represent the weak interaction field as a gauge field, it was first necessary to establish the exact form of the corresponding gauge symmetry. The fact is that the symmetry of the weak interaction is much more complex than that of the electromagnetic interaction, since the weak interaction itself is more complex. This is illustrated by a number of circumstances. Thus, weak interactions often involve particles of at least four different types (in the decay of a neutron, for example, neutron, proton, electron and neutrino). In addition, the action of weak forces leads to a change in their nature (the transformation of some particles into others due to weak interaction). On the contrary, electromagnetic interaction does not change the nature of the particles participating in it.

It turned out that to maintain the symmetry of the weak interaction, three new force fields are needed, in contrast to a single electromagnetic field. This means that there must be three new types of particles - carriers of interaction, one for each field. They are called spin-1 heavy vector bosons and are carriers of the weak force. W+ and W- particles are carriers of two of the three fields associated with the weak interaction. The third field corresponds to an electrically neutral carrier particle, called the Z° particle. The existence of a Z° particle means that weak interaction may not be accompanied by electric charge transfer.

The concept of spontaneous symmetry breaking played a key role in the creation of the theory of electroweak interaction. Some physical systems that have a certain symmetry may lose it in cases where the symmetric state is energetically unfavorable (it does not have a minimum energy), and the energetically favorable state does not have the original symmetry and is ambiguous. This ambiguity is expressed mathematically in the fact that the equation of motion of a given physical system is represented not by one solution, but by a series of solutions that do not have the original symmetry. Eventually, from this series of solutions, one is implemented. After all, not every solution to a problem must have all the properties of its original level. And therefore, particles that are completely different at low energies, at high energies may actually turn out to be one and the same particle, but located in different states. Thus, Weinberg and Salam's idea of ​​spontaneous symmetry breaking unified electromagnetism and the weak force into a unified gauge field theory.

The Weinberg-Salam theory presents only four fields: electromagnetic and three fields corresponding to weak interactions. In this theory, photons and heavy vector bosons (W± and Z°) have a common origin and are closely related to each other. In addition, a permanent nationwide

This is a scalar field (the so-called Higgs field), with which photons and vector bosons interact differently, which determines the difference in their masses. Scalar field quanta are massive elementary particles with zero spin. They are called Higgs (named after the physicist P. Higgs, who suggested their existence). The number of such Higgs bosons can reach several dozen.

1 The experimental detection of Higgs bosons has recently been reported. The results of this experiment are currently being verified.

Why do electromagnetic and weak interactions have such different properties? The Weinberg-Salam theory explains these differences by breaking symmetry. If the symmetry were not broken, then both interactions would be comparable in magnitude. Initially, W and Z quanta have no mass, but due to symmetry breaking, some Higgs particles merge with W and Z particles, giving them mass. But the photon does not participate in this process of merging with Higgs particles and therefore does not have a rest mass. Symmetry breaking entails a sharp decrease in the weak interaction, since it is directly related to the masses of W and Z particles. We can say that the weak interaction is so small because the W and Z particles are very massive.

Leptons rarely approach such small distances (r = 10-18 m) at which the exchange of heavy vector bosons becomes possible. But at high energies (more than 100 GeV), when W and Z particles can be freely produced, the exchange of W- and Z-bosons is as easy as the exchange of photons (massless particles), the difference between photons and bosons is erased. Under these conditions, there should be complete symmetry between the electromagnetic and weak interactions—the electroweak interaction.

Most convincing experimental verification The new theory was to confirm the existence of the hypothetical W- and Z-particles. Their discovery in 1983 became possible only with the creation of very powerful accelerators newest type and meant the triumph of the Weinberg-Salam theory. It was conclusively proven that the electromagnetic and weak forces are two components of a single electroweak force.

In 1979, S. Weinberg, A. Salam and S. Glashow were awarded the Nobel Prize for creating the theory of electroweak interaction.

10.3.4. Quantum chromodynamics.

The next step on the path to understanding fundamental interactions is the creation of a theory of strong interaction. To do this, it is necessary to give the features of a gauge field to the strong interaction. The latter can be represented as a result of the exchange of gluons, which ensures the connection of quarks (in pairs or triplets) into hadrons (see 10.3.2). The exchange of gluons changes the “color” of quarks, but leaves other characteristics unchanged, i.e. preserves their variety (“aroma”).

The theory of strong interaction was created according to the same scheme as the theory of weak interaction. The requirement of local gauge symmetry (i.e., invariance with respect to changes in “color” at each point in space) leads to the need to introduce compensating force fields. A total of eight new compensating force fields are required. The carrier particles of these fields are gluons. Thus, the theory implies that there must be as many as eight different types of gluons.

Like photons, gluons have zero rest mass and spin 1. Gluons also have various colors, but not pure, but mixed; gluons consist of a "color" and an "anticolor" (for example, blue-anti-green). Therefore, the emission or absorption of a gluon is accompanied by a change in the color of the quark (“play of colors”). For example, a red quark, losing a red-anti-blue gluon, turns into a blue quark, and a green quark, absorbing a blue-anti-green gluon, turns into a blue quark.

From the point of view of quantum chromodynamics (quantum color theory), strong interaction is nothing more than the desire to maintain a certain abstract symmetry of nature: maintaining the white color of all hadrons when their color changes components- quarks. In a proton, for example, three quarks constantly exchange gluons, changing their color. However, that

These changes are not arbitrary in nature, but are subject to a strict rule: at any moment of time, the “total” color of three quarks must be white light, i.e. the sum “red + green + blue”. This also applies to mesons consisting of a quark-antiquark pair. Since an antiquark is characterized by an anticolor, such a combination is obviously colorless (“white”), for example, a red quark in combination with an antired quark forms a colorless (“white”) meson.

1 Leptons, photons and intermediate bosons (W- and Z-particles) do not carry color and therefore do not participate in the strong interaction).

Quantum chromodynamics perfectly explains the rules that all combinations of quarks obey, the interaction of gluons with each other (a gluon can decay into two gluons or two gluons merge into one - that’s why nonlinear terms appear in the gluon field equation), the interaction of quarks and gluons like QED (quarks covered with clouds of virtual gluons and quark-antiquark pairs), the complex structure of a hadron consisting of quarks “dressed” in clouds, etc.

It may be premature to assess quantum chromodynamics as a definitive and complete theory of the strong interaction, but its experimental status is quite strong and its achievements are promising.

10.3.5. On the way to the Great Unification.

With the creation of quantum chromodynamics, hope arose for the construction of a unified theory of all (or at least three out of four) fundamental interactions. Models that describe three (strong, weak, electromagnetic) of the four fundamental interactions in a unified way are called Grand Unified models.

The experience of successfully combining weak and electromagnetic interactions based on the idea of ​​gauge fields suggested possible ways further development of the principle of unity of physics, unification of fundamental physical interactions. One of them is based on amazing fact, that the interaction constants of the electroweak and strong interactions upon transition to small distances (i.e., to high energies) become equal to each other at the same energy. This energy was called the energy of unification. It is approximately 1014-1016 GeV; it corresponds to a distance = 10-29 cm.

At energies above 1014-1016 GeV, or at distances less than 10-29 cm, strong, weak and electromagnetic interactions are described by a single constant, i.e. have a common nature. Quarks and leptons are practically indistinguishable here, and gluons, photons and vector bosons W± and Z° are quanta of gauge fields with a single gauge symmetry. After all, if the electroweak and strong interactions are in fact only two sides of the Great Unified Interaction, then the latter must also correspond to a gauge field with some complex symmetry. It must be general enough to cover all gauge symmetries contained in both quantum chromodynamics and the theory of electroweak interaction. At the same time, its spontaneous breakdown should lead to the separation of the electroweak and strong interactions. Finding such symmetry is the main task towards creating a unified theory of electroweak and strong interactions.

There are different approaches that give rise to competing versions of Grand Unified theories. However, all these hypothetical versions of the Great Unification have a number of common features. Firstly, in all hypotheses, quarks and leptons - carriers of the electroweak and strong interactions - are included in a single theoretical scheme. Until now they have been considered as completely different objects. Secondly, the use of abstract gauge symmetries leads to the discovery of new types of fields that have new properties, for example the ability to transform quarks into leptons.

In the simplest version of the Grand Unified theory, 24 fields are required to transform quarks into leptons, and 12 of the quanta of these fields are already known: a photon, two W particles, a Z° particle and eight gluons. The remaining 12 quanta are new superheavy intermediate bosons, combined common name X- and Y-particles (having color and electrical charge). These quanta correspond to fields that maintain broader gauge symmetry and mix quarks with leptons. Consequently, X and Y particles can transform quarks into leptons (and vice versa).

There is no talk yet about direct experimental detection of X- and Y-bosons. After all, Grand Unified theories deal with particle energies above 1014 GeV. This is very high energy. It is difficult to say when it will be possible to obtain particles of such high energies at acceleration.

retailers. This possibility is not envisaged in the foreseeable future. Modern accelerators struggle to reach 100 GeV. And therefore, the main area of ​​testing the theories of the Grand Unification is its consequences (for cosmology and for low-energy regions). Thus, without Grand Unification theories it is impossible to describe the early stage of the evolution of the Universe, when the temperature of the primary plasma reached 10 27 K. It was under such conditions that superheavy X and Y bosons could be created and annihilated.

In addition, based on Grand Unified theories, two important patterns are predicted in low-energy regions that can be tested experimentally. First, quark-lepton transitions should cause proton decays. This means it is unstable: the lifetime of a proton should be approximately 1031 years. Secondly, the inevitable consequence of these theories is the existence of a magnetic monopole - a stable and very heavy (108 proton mass) particle that carries one magnetic pole. Experimental detection of proton decay and magnetic monopoles could provide a strong argument in favor of Grand Unified theories. Experimental efforts are aimed at testing these predictions. Detection of proton decay will be the greatest physical experiment XXI century! But there is still no firmly established data on this matter.

10.3.6. Supergravity.

But unifying three of the four fundamental interactions is not yet a unified theory in in every sense words. After all, gravity still remains. Theoretical schemes, within which all known types of interactions (strong, weak, electromagnetic and gravitational) are combined, are called supergravity models. Theoretical models that combine all four interactions (supergravity) are based on the idea of ​​supersymmetry, i.e. such a transition from global gauge symmetry to local, which would allow the transition from fermions (carriers of the substrate of matter) to bosons (carriers of the structure of matter, carriers of interactions), and vice versa.

Therefore, supergravity is a theory not only of the carriers of all fundamental interactions, but also of the particles that make up matter (quarks and leptons). In supergravity they are all united in a single theory of matter (substance and field). One of theoretical models brings together 70 particles with spin 0; 56 particles with spin 1/2; 28 particles with spin 1; 8 particles with spin 3/2 (they were called gravitino) and 1 particle with spin 2 (graviton). All these particles were formed in the first moments of our Universe.

Supergravity is the culmination theoretical physics, that very general and abstract theory that crowns the long and intense, and often dramatic search for the unity of physics. At the level of supersymmetry, there is a need to substantiate abstract symmetries of gauge fields. In other words, the need again arises to substantiate physics with geometry (see 9.2.3), in particular, to represent gauge fields as geometric symmetries, associated with additional dimensions of space. This led to the revival of ideas about the multidimensionality of our world.

Models of supersymmetry are emerging in which our world is viewed as 11-dimensional (or 10-dimensional, or even 26-dimensional) space-time. Of the 11 dimensions, only four appear in our world, and the remaining 7 remain twisted and closed. These " hidden dimensions"exist on a scale of r = 10-33 cm. To penetrate such scales, energy is required comparable to the entire energy of our Galaxy! Of course, projects to penetrate such small areas of our world in the foreseeable future are unrealistic for humanity. (Perhaps they are unreal in principle.)

An undoubted advantage and evidence of the promise of the supergravity program is that under its influence a new approach to unifying fundamental interactions has emerged - superstring theory. In this theory, a particle is considered as a string - an oscillatory system with distributed parameters. At low energies, the string behaves like a particle, and at high energies, parameters characterizing its vibration must be introduced into the description of the string’s motion. The mathematical side of superstring theory turns out to be simpler than in the standard theory: unwanted infinities disappear. One of the important cosmological consequences of superstring theory is the possibility of a multiplicity of universes, each of which has its own set of fundamental interactions.

So, let's summarize some results. The unification of fundamental interactions essentially began in the 19th century. from the synthesis of electricity and magnetism in Maxwell's theory of the electromagnetic field. Attempts to synthesize gravity and electromagnetism made by A. Einstein in the “unified field theory” failed. But the theoretical unification of weak and electromagnetic interactions received reliable confirmation in 1983 thanks to the experimental detection of W- and Z-bosons. There is no solid evidence confirming the Great Unification (proton decay, the existence of a magnetic monopole), but they are expected. Supergravity program - shining example how theory can significantly outstrip practice, experience, and experimental possibilities. But even here we can expect indirect empirical substantiations of supergravity models by data from extragalactic astronomy, astrophysics and cosmology. Thus, physics is on the threshold of creating a unified theory of matter, i.e. all fundamental interactions (fields) and structure of matter. It is possible that already in the first half of the 21st century. this greatest task in the entire history of science will be solved. In a sense this means the end physical science as knowledge of the fundamental principles of matter.

True, there are still many serious problems to be solved along this path. Thus, we must verify the existence of a number of elementary particles that are predicted by modern theory (primarily Higgs bosons). In addition, a quantum theory of gravity must be created, without which the implementation of the supersymmetry program is impossible. Only with the creation of a quantum theory of gravity, apparently, will it be possible to answer the following questions: why is our space three-dimensional and time one-dimensional? Why are there only four fundamental interactions, and exactly the ones we have? Why are we given exactly this set of elementary particles? How is the mass of elementary particles determined? Why do world constants have exactly these values ​​and not others? Why does an elementary electric charge exist in nature and what does its magnitude depend on? Why is the neutrino mass so small? and etc.

Much in solving these problems will depend on the capabilities of experiments in the field of elementary particle physics. Current accelerators (colliders), in which clusters of elementary particles (electrons, protons, etc.) accelerating towards each other collide, provide the energy of the colliding

particles about 200 GeV. Projects of accelerators that increase this energy by 2-3 orders of magnitude are being discussed. But the technical possibilities here are not unlimited. Increasing energy requires the creation of strong energy fields. And there is a limit to this, because it is very strong fields will destroy atoms of any substance; this means that in such a field the accelerator will destroy itself! Currently, projects are being discussed to create accelerators using nanotechnology, which make it possible to quickly regenerate material cells destroyed by a strong electromagnetic field. The implementation of such a program, if it is possible at all, is a matter of the very distant future. True, it remains possible to study cosmic rays (neutrino fluxes, gravitons, etc.) with high energy. To do this, you need to learn how to confidently register them. However, other options for the development of physics in the 21st century cannot be ruled out. Science must always be ready for revolutionary turns. And therefore, for example, the discovery of new fundamental interactions, subquark particles, etc. may require a radical revision of modern (relativistic and quantum) physics, putting on the agenda the issue of creating a fundamentally “new physics”. The area where the Microworld turns out to be connected with the Megaworld, the ultrasmall with the ultralarge, the elementary particle with the Universe as a whole, physics with astronomy brings a lot of unusual and unexpected things to the knowledge of the physical world.
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To understand whether it is worth continuing to write short sketches that literally explain different physical phenomena and processes. The result dispelled my doubts. I'll continue. But in order to approach rather complex phenomena, you will have to make separate sequential series of posts. So, in order to get to the story about the structure and evolution of the Sun and other types of stars, you will have to start with a description of the types of interaction between elementary particles. Let's start with this. No formulas.
In total, four types of interaction are known in physics. Everyone is well known gravitational And electromagnetic. And almost unknown to the general public strong And weak. Let us describe them sequentially.
Gravitational interaction . People have known it since ancient times. Because it is constantly in the gravity field of the Earth. And from school physics we know that the force of gravitational interaction between bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. Under the influence of gravitational force, the Moon revolves around the Earth, the Earth and other planets revolve around the Sun, and the latter, together with other stars, revolves around the center of our Galaxy.
The rather slow decrease in the strength of gravitational interaction with distance (inversely proportional to the square of the distance) forces physicists to talk about this interaction as long-range. In addition, the forces of gravitational interaction acting between bodies are only forces of attraction.
Electromagnetic interaction . In the simplest case of electrostatic interaction, as we know from school physics, the force of attraction or repulsion between electrically charged particles is proportional to the product of their electric charges and inversely proportional to the square of the distance between them. Which is very similar to the law of gravitational interaction. The only difference is that electric charges with the same signs repel, and those with different signs attract. Therefore, electromagnetic interaction, like gravitational interaction, is called by physicists long-range.
At the same time, electromagnetic interaction is more complex than gravitational interaction. From school physics we know that the electric field is created by electric charges, magnetic charges do not exist in nature, but the magnetic field is created electric currents.
In fact, an electric field can also be created by a time-varying magnetic field, and a magnetic field can also be created by a time-varying magnetic field electric field. The latter circumstance makes it possible to exist electromagnetic field without any electrical charges or currents at all. And this possibility is realized in the form of electromagnetic waves. For example, radio waves and light quanta.
Because electrical and gravitational forces are equally dependent on distance, it is natural to try to compare their intensities. So, for two force protons gravitational attraction turn out to be 10 to the 36th power of times (a billion billion billion billion times) weaker than the forces of electrostatic repulsion. Therefore, in the physics of the microworld, gravitational interaction can quite reasonably be neglected.
Strong interaction . This - short-range strength. In the sense that they act at distances of only about one femtometer (one trillionth of a millimeter), and at large distances their influence is practically not felt. Moreover, at distances of the order of one femtometer, the strong interaction is about a hundred times more intense than the electromagnetic one.
This is why equally electrically charged protons in the atomic nucleus are not repelled from each other by electrostatic forces, but are held together by strong interactions. Because the dimensions of a proton and a neutron are about one femtometer.
Weak interaction . It is really very weak. Firstly, it operates at distances a thousand times smaller than one femtometer. And at long distances it is practically not felt. Therefore, like the strong one, it belongs to the class short-range. Secondly, its intensity is approximately one hundred billion times less than the intensity of electromagnetic interaction. The weak force is responsible for some decays of elementary particles. Including free neutrons.
There is only one type of particle that interacts with matter only through weak interaction. This is a neutrino. Almost a hundred billion solar neutrinos pass through every square centimeter of our skin every second. And we don’t notice them at all. In the sense that during our lifetime, it is unlikely that a few neutrinos will interact with the matter of our body.
We will not talk about theories that describe all these types of interactions. For what is important to us is a high-quality picture of the world, and not the delights of theorists.

For a long time, man has sought to know and understand the physical world around him. It turns out that all the infinite variety of physical processes occurring in our world can be explained by the existence in nature of a very small number of fundamental interactions. Their interaction with each other explains the orderly arrangement of celestial bodies in the Universe. They are the “elements” that move celestial bodies, generate light and make life itself possible (see. Application ).
Thus, all processes and phenomena in nature, be it an apple falling, a supernova explosion, a penguin jumping, or the radioactive decay of substances, occur as a result of these interactions.
The structure of the substance of these bodies is stable due to the bonds between its constituent particles.

1. TYPES OF INTERACTIONS

Despite the fact that matter contains a large number of elementary particles, there are only four types of fundamental interactions between them: gravitational, weak, electromagnetic and strong.
The most comprehensive is gravitational interaction . All material interactions, without exception, are subject to it - both microparticles and macrobodies. This means that all elementary particles participate in it. It manifests itself in the form of universal gravity. Gravity (from Latin Gravitas - heaviness) controls the most global processes in the Universe, in particular, ensures the structure and stability of our solar system. According to modern concepts, each of the interactions arises as a result of the exchange of particles called carriers of this interaction. Gravitational interaction is carried out through exchange gravitons .
, like gravitational, is long-range in nature: the corresponding forces can manifest themselves at very significant distances. Electromagnetic interaction is described by charges of one type (electric), but these charges can already have two signs - positive and negative. Unlike gravity, electromagnetic forces can be both attractive and repulsive forces. The physical and chemical properties of various substances, materials and living tissue itself are determined by this interaction. It also powers all electrical and electronic equipment, i.e. connects only charged particles with each other. The theory of electromagnetic interaction in the macrocosm is called classical electrodynamics.
Weak interaction less known outside narrow circle physicists and astronomers, but this does not in any way detract from its significance. Suffice it to say that if it were not there, the Sun and other stars would go out, because in the reactions that ensure their glow, the weak interaction plays a very important role. The weak interaction is short-range: its radius is approximately 1000 times smaller than that of nuclear forces.
Strong interaction – the most powerful of all the others. It defines connections only between hadrons. Nuclear forces acting between nucleons in an atomic nucleus are a manifestation of this type of interaction. It is about 100 times stronger than electromagnetic energy. Unlike the latter (and also gravitational), it is, firstly, short-range at a distance greater than 10–15 m (on the order of the size of the nucleus), the corresponding forces between protons and neutrons, sharply decreasing, cease to bind them to each other. Secondly, it can be described satisfactorily only by means of three charges (colors) forming complex combinations.
Table 1 roughly presents the most important elementary particles belonging to the main groups (hadrons, leptons, interaction carriers).

Table 1

Participation of basic elementary particles in interactions

The most important characteristic of a fundamental interaction is its range of action. The radius of action is the maximum distance between particles, beyond which their interaction can be neglected (Table 2). At a small radius the interaction is called short-acting , with large – long-range .

table 2

Main characteristics of fundamental interactions

Strong and weak interactions are short-range . Their intensity decreases rapidly with increasing distance between particles. Such interactions occur at a short distance, inaccessible to perception by the senses. For this reason, these interactions were discovered later than others (only in the 20th century) using complex experimental facilities. Electromagnetic and gravitational interactions are long-range . Such interactions decrease slowly with increasing distance between particles and do not have a finite range of action.

2. INTERACTION AS A CONNECTION OF STRUCTURES OF MATTER

In the atomic nucleus, the bond between protons and neutrons determines strong interaction . It provides exceptional core strength, which underlies the stability of the substance under terrestrial conditions.

Weak interaction a million times less intense than strong. It acts between most elementary particles located at a distance of less than 10–17 m from each other. Weak interaction The radioactive decay of uranium and thermonuclear fusion reactions in the Sun are determined. As you know, it is the radiation of the Sun that is the main source of life on Earth.

Electromagnetic interaction , being long-range, determines the structure of matter beyond the range of the strong interaction. The electromagnetic force binds electrons and nuclei in atoms and molecules. It combines atoms and molecules into various substances, determines chemical and biological processes. This interaction is characterized by forces of elasticity, friction, viscosity, and magnetic forces. In particular, the electromagnetic repulsion of molecules located at short distances causes a ground reaction force, as a result of which we, for example, do not fall through the floor. Electromagnetic interaction does not have a significant effect on the mutual motion of macroscopic bodies large mass, since each body is electrically neutral, i.e. it contains approximately equal numbers of positive and negative charges.

Gravitational interaction directly proportional to the mass of interacting bodies. Due to the small mass of elementary particles, the gravitational interaction between particles is small compared to other types of interaction, therefore, in the processes of the microworld, this interaction is insignificant. As the mass of interacting bodies increases (i.e., as the number of particles they contain increases), the gravitational interaction between the bodies increases in direct proportion to their mass. In this regard, in the macrocosm, when considering the movement of planets, stars, galaxies, as well as the movement of small macroscopic bodies in their fields, gravitational interaction becomes decisive. It holds the atmosphere, seas and everything living and nonliving on Earth, the Earth revolving in orbit around the Sun, the Sun within the Galaxy. Gravitational interaction plays a major role in the formation and evolution of stars. Fundamental interactions of elementary particles are depicted using special diagrams, in which a real particle corresponds to a straight line, and its interaction with another particle is depicted either by a dotted line or a curve (Fig. 1).

Diagrams of interactions of elementary particles

Modern physical concepts of fundamental interactions are constantly being refined. In 1967 Sheldon Glashow, Abdus Salam And Steven Weinberg created a theory according to which the electromagnetic and weak interactions are a manifestation of a single electroweak interaction. If the distance from an elementary particle is less than the radius of action of weak forces (10–17 m), then the difference between electromagnetic and weak interactions disappears. Thus, the number of fundamental interactions was reduced to three.

The theory of the "Great Unification".
Some physicists, in particular G. Georgi and S. Glashow, suggested that during the transition to higher energies another merger should occur - the unification of the electroweak interaction with the strong one. The corresponding theoretical schemes are called the “Grand Unification” Theory. And this theory is currently being tested experimentally. According to this theory, which combines strong, weak and electromagnetic interactions, there are only two types of interactions: unified and gravitational. It is possible that all four interactions are only partial manifestations of a single interaction. The premises of such assumptions are considered when discussing the theory of the origin of the Universe (the Big Bang theory). Theory " Big Bang” explains how the combination of matter and energy gave birth to stars and galaxies.