WEAK INTERACTION- one of the four known funds. interactions between . S. v. much weaker than strong and e-magn. interactions, but much stronger than gravitational. In the 80s. found that weak and e-magn. interactions - dec. manifestations of a single electroweak interaction.
The intensity of interactions can be judged by the speed of the processes it causes. Usually, the rates of processes are compared with each other at GeV energies, which are characteristic of elementary particle physics. At such energies, the process due to the strong interaction takes place in s, e-magn. process in time s, while the characteristic time of processes occurring due to S. v. (weak processes), much more: c, so that in the world of elementary particles, weak processes proceed extremely slowly.
Another characteristic of interaction is particles in matter. Strongly interacting particles (hadrons) can be stopped by an iron plate several times thick. tens of cm, while a neutrino with only SV would pass without experiencing a single collision through an iron plate about a billion kilometers thick. Gravity is even weaker. interaction, the strength of which at an energy of ~1 GeV is 10 33 times less than that of S. v. However, usually the role of gravitational interactions are much more noticeable than the role of S. in. This is due to the fact that gravitational interaction, like electromagnetic, has an infinitely large radius of action; therefore, for example, gravity acts on bodies located on the surface of the Earth. the attraction of all the atoms that make up the Earth. The weak interaction has a very small radius of action: approx. 2 * 10 -16 cm (which is three orders of magnitude smaller than the radius of strong interaction). As a result, for example, S. century. between the nuclei of two neighboring atoms, located at a distance of 10 -8 cm, is negligible, incomparably weaker not only electromagnetic, but also gravitational. interactions between them.
However, despite the small size and short-acting, S. century. plays a very important role in nature. So, if it were possible to “turn off” the S. century, then the Sun would go out, since the process of converting a proton into a neutron, a positron and a neutrino would be impossible, as a result of which four protons turn into 4 He, two positrons and two neutrinos. This process serves as the source of energy for the sun and most stars Hydrogen cycle). Processes of S. in. with the emission of neutrinos in general are exceptionally important in evolution of stars, since they cause energy losses by very hot stars, in supernova explosions with the formation of pulsars, etc. If there were no S. v., muons, mesons, strange and charmed, would be stable and widespread in ordinary matter particles, to-rye disintegrate as a result of S. century. Such a large role of S. E. is connected with the fact that it does not obey a number of prohibitions characteristic of a strong and el-magn. interactions. In particular, S. century. turns charged leptons into neutrinos, and one type (flavor) into quarks of other types.
The intensity of weak processes grows rapidly with increasing energy. So, neutron beta decay, the energy release in Krom is small (~ 1 MeV), lasts approx. 10 3 s, which is 10 13 times longer than the lifetime of a hyperon, the energy release during the decay of which is ~100 MeV. The cross section of interaction with nucleons for neutrinos with an energy of ~100 GeV is approx. a million times more than for neutrinos with an energy of ~1 MeV. According to the theoretical representations, the growth of the cross section will last up to energies of the order of several. hundreds of GeV (in the system of the center of mass of colliding particles). At these energies and at large momentum transfers, effects associated with the existence intermediate vector bosons. At distances between colliding particles much smaller than 2 x 10 -16 cm (the Compton wavelength of intermediate bosons), the S. v. and el-magn. interactions have almost the same intensity.
Naib. a common process due to S. century, - beta decay radioactive atomic nuclei. In 1934, E. Fermi (E. Fermi) built a theory of decay, to-paradise with certain creatures. modifications formed the basis of the subsequent theory of the so-called. universal local four-fermion S. v. (Fermi interactions). According to Fermi's theory, an electron and a neutrino (more precisely, ), emitted from a radioactive nucleus, were not in it before, but arose at the moment of decay. This phenomenon is analogous to the emission of low-energy photons (visible light) from excited atoms or high-energy photons (-quanta) from excited nuclei. The reason for such processes is the interaction of electric. particles with e-magn. field: a moving charged particle creates an electromagnetic current, which perturbs the e-mag. field; as a result of the interaction, the particle transfers energy to the quanta of this field - photons. Interaction of photons with e-magn. current is described by the expression BUT. Here e- elementary electric charge, which is a constant e-magn. interactions (see Interaction constant), A- operator of the photon field (i.e., the operator of the creation and destruction of a photon), j em - the operator of the density of the e-mag. current. (Often, the expression for the electric magnetic current also includes a multiplier e.) In j em all the charges contribute. particles. For example, the term corresponding to an electron has the form: [Above, for simplification, it is not shown that j uh, as well as BUT, is a four-dimensional vector. More precisely, instead, you should write a set of four expressions where - Dirac matrix,= 0, 1, 2, 3. Each of these expressions is multiplied by the corresponding component of the four-dimensional vector.]
The interaction describes not only the emission and absorption of photons by electrons and positrons, but also processes such as the production of electron-positron pairs by photons (see Fig. Birth of couples)or annihilation these pairs into photons. The exchange of a photon between two charges. particles leads to their interaction with each other. The result is, for example, the scattering of an electron by a proton, which is schematically depicted Feynman diagram shown in fig. 1. During the transition of a proton in the nucleus from one level to another, the same interaction can lead to the creation of an electron-positron pair (Fig. 2).
Fermi's decay theory is essentially analogous to the el-magn theory. processes. Fermi based his theory on the interaction of two "weak currents" (see Fig. Current in quantum field theory), but interacting with each other not at a distance by exchanging a particle - a field quantum (a photon in the case of an el-magnet interaction), but by contact. This is the interaction between four fermion fields (four fermions p, n, e and neutrino v) in modern. notation looks like: 
. Here G F- Fermi constant, or weak four-fermion interaction constant, experiment. swarm 
erg * cm 3 (the value has the dimension of the square of the length, and in units the constant 
, where M- proton mass), - proton creation operator (antiproton annihilation), - neutron annihilation operator (antineutron production), - electron creation operator (positron annihilation), v
- neutrino annihilation operator (antineutrino generation). (Here and in what follows, the operators for the creation and annihilation of particles are denoted by the symbols of the corresponding particles in bold type.) The current converting a neutron into a proton was later called nucleon, and the current - lepton. Fermi postulated that, like e-magn. current, weak currents are also four-dimensional vectors: Therefore, the Fermi interaction is called. vector. 
Like the creation of an electron-positron pair (Fig. 2), the decay of a neutron can be described by a similar diagram (Fig. 3) [antiparticles are marked with a tilde above the symbols of the corresponding particles]. The interaction of lepton and nucleon currents should also lead to other processes, for example. to reaction 
(Fig. 4), k steam (Fig. 5) and 
etc.
Creatures. the difference between weak currents and electromagnetic is that a weak current changes the charge of particles, while e-magn. the current does not change: a weak current turns a neutron into a proton, an electron into a neutrino, and an electromagnetic current turns a proton into a proton, and an electron into an electron. Therefore, weak currents ev are called. charged currents. According to such a term of logic, ordinary e-mag. her current is neutral current.
Fermi's theory was based on the results of research in three different ways. areas: 1) experimental. researches actually S. of century. (-decay), which led to the hypothesis of the existence of neutrinos; 2) experiment. studies of the strong force (), which led to the discovery of protons and neutrons and to the understanding that nuclei are composed of these particles; 3) experiment. and theoretical research e-magn. interactions, as a result of which the foundation of quantum field theory was laid. Further development Physics of elementary particles has repeatedly confirmed the fruitful interdependence of studies of the strong, weak and e-magn. interactions.
The theory of universal four-fermion S. v. differs from Fermi's theory in a number of beings, items. These differences, established in subsequent years as a result of the study of elementary particles, were reduced to the following.
The hypothesis that S. in. does not preserve parity, was put forward by Lee Tsung-Dao and Yang Chen Ning in 1956 at the theoretical decay research K-mesons; soon non-conservation R- and C-parities were found experimentally in the decay of nuclei [Wu Chien-Shiung et al], in the decay of the muon [R. Garvin (R. Garwin), L. Lederman (L. Lederman), V. Telegdi (V. Telegdi), J. Friedman (J. Friedman) and others] and in the decays of other particles.
Summarizing a huge experiment. material, M. Gell-Mann (M. Gell-Mann), P. Feynman (R. Feynman), P. Marshak (R. Marshak) and E. Sudarshan (E. Sudarshan) in 1957 proposed the theory of universal S. in. - so-called. V- BUT-theory. In a formulation based on the quark structure of hadrons, this theory is that the total weak charged current j u is the sum of lepton and quark currents, each of these elementary currents containing the same combination of Dirac matrices:
As it turned out later, the charge. the lepton current, represented in the Fermi theory by one term, is the sum of three terms: 
and each of the known charges. leptons (electron, muon and heavy lepton) is included in the charge. current with his neutrino.
Charge the hadronic current, represented in the Fermi theory by the term, is the sum of the quark currents. By 1992 five types of quarks were known , from which all known hadrons are built, and the existence of a sixth quark is assumed ( t With Q=+ 2 / 3). Charged quark currents, like lepton currents, are usually written as the sum of three terms: 
However, here are linear combinations of operators d, s, b, so the quark charged current consists of nine terms. Each of the currents is the sum of the vector and axial currents with coefficients equal to one.
The coefficients of nine charged quark currents are usually presented as a 3x3 matrix, which is parameterized by three angles and a phase factor characterizing the violation CP invariance in weak decays. This matrix is called matrices Kobayashi - Maskawa (M. Kobayashi, T. Maskawa).
Lagrangian S. v. charged currents has the form: 
Edetok, conjugate, etc.). Such an interaction of charged currents quantitatively describes a huge number of weak processes: leptonic, semileptonic ( 
etc.) and non-leptonic ( 
,, etc.). Many of these processes were discovered after 1957. During this period, two fundamentally new phenomena were also discovered: CP violation and neutral currents. 
Violation of CP invariance was discovered in 1964 in the experiment of J. Christepson, J. Cronin, V. Fitch, and R. Turley, who observed decay of long-lived K° mesons into two mesons. Later, CP violation was also observed in semileptonic decays. To elucidate the nature of the CP-noninvariant interaction, it would be extremely important to find a k-l. CP-noninvariant process in decays or interactions of other particles. In particular, of great interest are the searches for the dipole moment of the neutron (the presence of which would mean the violation of invariance with respect to reversal of time, and therefore, according to the theorem SRT, and CP-invariance).
The existence of neutral currents was predicted by a unified theory of weak and el-magn. interactions, created in the 60s. Sh. Glashow, S. Weinberg, A. Salam and others, and later called. standard theory of the electroweak interaction. According to this theory, S. century. is not a contact interaction of currents, but occurs through the exchange of intermediate vector bosons ( W + , W - , Z 0) - massive particles with spin 1. In this case, bosons carry out the interaction of the charge. currents (Fig. 6), and Z0-bosons - neutral (Fig. 7). In the standard theory, three intermediate bosons and a photon are vector quanta, the so-called. calibration fields, appearing at asymptotically large transfers of the four-dimensional momentum ( , mz, where m w , m z- masses W- and Z-bosons in energetic. units) is completely equal. Neutral currents were discovered in 1973 in the interaction of neutrinos and antineutrinos with nucleons. Later, the processes of scattering of a muon neutrino by an electron were found, as well as the effects of parity nonconservation in the interaction of electrons with nucleons, due to the electron neutral current (these effects were first observed in experiments on parity nonconservation during atomic transitions, carried out in Novosibirsk by L.M. Barkov and M. S. Zolotorev, as well as in experiments on the scattering of electrons by protons and deuterons in the USA).
The interaction of neutral currents is described by the corresponding term in the S. v. Lagrangian:
where is a dimensionless parameter. In the standard theory (the experimental value of p coincides with 1 within one percent of the experimental accuracy and the accuracy of the calculation radiative corrections). The total weak neutral current contains contributions from all leptons and all quarks: 
Highly important property neutral currents is that they are diagonal, that is, they transfer leptons (and quarks) into themselves, and not into other leptons (quarks), as in the case of charged currents. Each of the 12 quark and lepton neutral currents is a linear combination of the axial current with a coefficient. I 3 and vector current with coefficient. 
, where I 3- the third projection of the so-called. weak isotopic spin, Q is the charge of the particle, and - Weinberg angle.
Necessity for the existence of four vector fields of intermediate bosons W+, W-, Z0 and photon BUT can explain the following. manner. As you know, in e-magn. electrical interaction. charge plays a dual role: on the one hand, it is a conserved quantity, and on the other hand, it is a source of e-mag. field that carries out the interaction between charged particles (interaction constant e). Such a role is electric. charge is provided by the gauge, which consists in the fact that the equations of the theory do not change when the wave functions of charged particles are multiplied by an arbitrary phase factor depending on the space-time point [local symmetry U(1)], and at the same time e-magn. the field, which is the gauge field, undergoes a transformation . Local group transformations U(1) with one type of charge and one gauge field commute with each other (such a group is called Abelian). The specified property of the electric. charge served as a starting point for constructing theories and other types of interactions. In these theories, conserved quantities (for example, isotopic spin) are simultaneously sources of certain gauge fields that transfer the interaction between particles. In the case of several types of "charges" (eg, different projections of isotopic. spin), when separate. transformations do not commute with each other (a non-Abelian group of transformations), it turns out that it is necessary to introduce several calibration fields. (Multiplets of gauge fields corresponding to local non-Abelian symmetries, called Young - Mills fields.) In particular, to isotopic. spin [to which the local group corresponds SU(2)] acted as the interaction constant, three gauge fields with charges 1 and 0 are needed. charged currents of pairs of particles are involved 
etc., then it is assumed that these pairs are doublets of the weak isospin group, i.e., the group SU(2). Invariance of the theory under local group transformations SU(2) requires, as noted, the existence of a triplet of massless gauge fields W+, W - , W 0, the source of which is weak isospin (the interaction constant g). By analogy with the strong interaction, in which hypercharge Y particles included in the isotopic. multiplet, determined by f-loy Q = I 3 + Y/2(where I 3- third isospin projection, a Q- electric charge), along with a weak isospin, a weak hypercharge is introduced. Then the conservation of electric. charge and weak isospin corresponds to the conservation of a weak hypercharge [group [ U(one)]. A weak hypercharge is a source of a neutral gauge field At 0(interaction constant g"). Two Mutually Orthogonal Linear Superpositions of Fields В° and W° describe the photon field BUT and the Z-boson field: 
where 
. It is the magnitude of the angle that determines the structure of neutral currents. It also defines the connection between the constant g characterizing the interaction of bosons with a weak current, and the constant e characterizing the interaction of a photon with an electric. current: 
In order for S. to. had a short-range character, the intermediate bosons must be massive, while the quanta of the initial gauge fields - 
- massless. According to the standard theory, the formation of mass in intermediate bosons occurs when spontaneous symmetry breaking SU(2) X U(1)before U(1) uh. In this case, one of the superpositions of fields At 0 and W0- photon ( BUT) remains massless, and the a- and Z-bosons acquire masses:
Experiment. data on neutral currents gave 
. This corresponded to the expected masses W- and Z-bosons, respectively, and
To discover W- and Z-bosons created special. installations in which these bosons are produced in collisions of high-energy colliding beams. The first installation went into operation in 1981 at CERN. In 1983, reports appeared on the detection at CERN of the first cases of the production of intermediate vector bosons. Birth data published in 1989 W- and Z-bosons at the American Proton-Antiproton Collider - Tevatron, at the Fermi National Accelerator Laboratory (FNAL). To con. 1980s total number W- and Z-bosons observed at the proton-antiproton colliders at CERN and FNAL numbered in the hundreds.
In 1989, the LEP electron-positroin colliders at CERN and the SLC at the Stanford Linear Accelerator Center (SLAC) became operational. The work of the LEP was especially successful, where by the beginning of 1991 more than half a million cases of the creation and decay of Z-bosons had been registered. The study of the decays of Z-bosons showed that no other neutrinos, except for the previously known ones, exist in nature. FROM high precision the mass of the Z-boson was measured: t z = 91.173 0.020 GeV (the mass of the W boson is known with much worse accuracy: mw= 80.220.26 GeV). Exploring properties W- and Z-bosons confirmed the correctness of the basic (gauge) idea of the standard theory of the electroweak interaction. However, to test the theory in full, it is also necessary to experimentally investigate the mechanism of spontaneous symmetry breaking. In the framework of the standard theory, the source of spontaneous symmetry breaking 
is a special iso-doublet scalar field with a specific. self-action 
, where is a dimensionless constant, and the constant h has the dimension of mass 
. The minimum interaction energy is achieved at, and, t, o., the lowest energy. the state - vacuum - contains a non-zero vacuum value of the field. If this mechanism of symmetry breaking really occurs in nature, then there must be elementary scalar bosons - the so-called. Higgs boson(quanta of the Higgs field). The standard theory predicts the existence of at least one scalar boson (it must be neutral). In more complex versions of the theory, there are several. such particles, and some of them are charged (it is possible). Unlike the intermediate bosons, the masses of the Higgs bosons are not predicted by theory.
The gauge theory of the electroweak interaction is renormalizable: this means, in particular, that the amplitudes of the weak and e-magn. processes can be calculated using perturbation theory, and the higher corrections are small, as in ordinary quantum theory (see Fig. Renormalizability). (In contrast to this, the four-fermion theory of S. V. is non-renormalizable and is not an internally consistent theory.)
There are theoretical models Grand Unification, in which as a group 
electroweak interaction, and the group SU(3) of a strong interaction are subgroups of a single group characterized by a single gauge interaction constant. In even more funds. models, these interactions are combined with gravitational (so-called. superunification).
Lit.: In at Ts. S., Moshkovsky S. A., Beta decay, trans. from English, M., 1970; Weinberg S., Unified theories of interaction of elementary particles, trans. from English, UFN, 1976, v. 118, c. 3, p. 505; Taylor, J., Gauge theories of weak interactions, trans. from English, M., 1978; Towards a unified field theory. Sat. Art., translations, M., 1980; Okun L. B., Leptons and Quarks, 2nd ed., M., 1990. L. B. Okun.
This is the third fundamental interaction that exists only in the microcosm. It is responsible for the transformation of some fermion particles into others, while the color of weakly interacting peptons and quarks does not change. A typical example of a weak interaction is the beta decay process, during which a free neutron decays into a proton, an electron, and an electron antineutrino in an average of 15 minutes. The decay is caused by the transformation of a flavor quark d into a flavor quark u inside the neutron. The emitted electron ensures the conservation of the total electric charge, and the antineutrino allows the conservation of the total mechanical momentum of the system.
The main function of the strong force is to combine quarks and antiquarks into hadrons. The theory of strong interactions is in the process of creation. It is a typical field theory and is called quantum chromodynamics. Its starting position is the postulate of the existence of three types of color charges (red, blue, green), expressing the ability inherent in matter to combine quarks in a strong interaction. Each of the quarks contains some combination of such charges, but their full mutual compensation does not occur, and the quark has a resulting color, that is, it retains the ability to interact strongly with other quarks. But when three quarks, or a quark and an antiquark, combine to form a hadron, the total combination of color charges in it is such that the hadron as a whole is color neutral. Color charges create fields with their inherent quanta - bosons. The exchange of virtual color bosons between quarks and (or) antiquarks serves as the material basis for the strong interaction. Before the discovery of quarks and color interaction, nuclear interaction was considered fundamental, uniting protons and neutrons in the nuclei of atoms. With the discovery of the quark level of matter, the strong interaction began to be understood as color interactions between quarks that combine into hadrons. Nuclear forces are no longer considered fundamental, they must somehow be expressed through colored forces. But this is not easy to do, because the baryons (protons and neutrons) that make up the nucleus are generally color neutral. By analogy, we can recall that atoms as a whole are electrically neutral, but at the molecular level, chemical forces appear, which are considered as echoes of electrical atomic forces.
The considered four types of fundamental interactions underlie all other known forms of motion of matter, including those that have arisen at the highest stages of development. Any complex forms of motion, when decomposed into structural components, are found as complex modifications of these fundamental interactions.
The Grand Unified Theory is a theory that combines electromagnetic, strong and weak interactions. Mentioning the theory of "Grand Unification", it comes to the fact that all the forces that exist in nature are a manifestation of one universal fundamental force. There are a number of considerations that give reason to believe that at the moment of the Big Bang that gave birth to our universe, only this force existed. However, over time, the universe expanded, which means it cooled down, and the single force split into several different ones, which we are now observing. The theory of "Grand Unification" should describe the electromagnetic, strong, weak and gravitational forces as a manifestation of one universal force. There is already some progress: scientists have managed to build a theory that combines the electromagnetic and weak interactions. However, the main work on the theory of "Great Unification" is still ahead.
Modern particle physics is forced to discuss issues that, in fact, worried even ancient thinkers. What is the origin of particles and chemical atoms built from these particles? And how can the Cosmos, the Universe we see, be built from particles, no matter how we call them? And one more thing - was the Universe created, or has it existed from eternity? If this is the right question, what are the ways of thought that can lead to convincing answers? All these questions are similar to the search for the true principles of being, questions about the nature of these principles.
Whatever we say about the Cosmos, one thing is clear that everything in the natural world is somehow composed of particles. But how is this composition to be understood? It is known that particles interact - they attract or repel each other. Particle physics studies various interactions. [Popper K. On the sources of knowledge and ignorance // Vopr. history of natural science and technology, 1992, no. 3, p. 32.]
Electromagnetic interaction attracted special attention in the 18th–19th centuries. Similarities and differences between electromagnetic and gravitational interactions were found. Like gravity, electromagnetic interaction forces are inversely proportional to the square of the distance. But, unlike gravity, electromagnetic "gravity" not only attracts particles (different in sign of charge), but also repels them from each other (equally charged particles). And not all particles are carriers of an electric charge. For example, the photon and neutron are neutral in this respect. In the 50s of the XIX century. the electromagnetic theory of D. C. Maxwell (1831–1879) unified electrical and magnetic phenomena and thereby clarified the action of electromagnetic forces. [Grunbaum A. Origin versus creation in physical cosmology (theological distortions of modern physical cosmology). - Q. philosophy, 1995, no. 2, p. 19.]
The study of the phenomena of radioactivity led to the discovery of a special kind of interaction between particles, which was called the weak interaction. Since this discovery is related to the study of beta radioactivity, one could call this interaction beta decay. However, in the physical literature it is customary to talk about weak interaction - it is weaker than the electromagnetic one, although it is much stronger than the gravitational one. The discovery was facilitated by the research of W. Pauli (1900–1958), who predicted that during beta decay, a neutral particle emerges, compensating for the apparent violation of the law of conservation of energy, called the neutrino. And besides, the discovery of weak interactions was facilitated by the studies of E. Fermi (1901–1954), who, along with other physicists, suggested that electrons and neutrinos, before they leave the radioactive nucleus, do not exist in the nucleus, so to speak, in finished form, but are formed during the radiation process. [Grunbaum A. Origin versus creation in physical cosmology (theological distortions of modern physical cosmology). - Q. philosophy, 1995, no. 2, p. 21.]
Finally, the fourth interaction turned out to be related to intranuclear processes. Called the strong interaction, it manifests itself as an attraction of intranuclear particles - protons and neutrons. Due to its large size, it turns out to be a source of enormous energy.
The study of four types of interactions followed the path of searching for their deep connection. On this obscure, largely obscure path, only the principle of symmetry guided the investigation and led to the identification of the alleged connection. various types interactions.
To reveal such connections, it was necessary to turn to the search for a special type of symmetry. A simple example This type of symmetry can be the dependence of the work done when lifting the load on the height of the lift. The energy expended depends on the height difference, but does not depend on the nature of the ascent path. Only the height difference is significant and it does not matter at all from what level we start the measurement. It can be said that we are dealing here with symmetry with respect to the choice of reference point.
Similarly, you can calculate the energy of movement of an electric charge in an electric field. The analog of the height here is the field voltage or, otherwise, the electric potential. The energy expended during the movement of the charge will depend only on the potential difference between the end and start points in the space of the field. We are dealing here with the so-called gauge or, in other words, with scale symmetry. Gauge symmetry referred to electric field, is closely related to the law of conservation of electric charge.
Gauge symmetry turned out to be the most important tool that gives rise to the possibility of resolving many difficulties in the theory of elementary particles and in numerous attempts to unify various types of interactions. In quantum electrodynamics, for example, various divergences arise. These divergences can be eliminated because the so-called renormalization procedure, which eliminates the difficulties of the theory, is closely related to gauge symmetry. The idea appears that the difficulties in constructing the theory of not only electromagnetic, but also other interactions can be overcome if it is possible to find other, hidden symmetries.
Gauge symmetry can take on a generalized character and can be related to any force field. In the late 1960s S. Weinberg (b. 1933) from Harvard University and A. Salam (b. 1926) from Imperial College in London, relying on the work of S. Glashow (b. 1932), undertook a theoretical unification of the electromagnetic and weak interactions. They used the idea of gauge symmetry and the concept of a gauge field related to this idea. [Yakushev A. S. Basic concepts of modern natural science. - M., Fact-M, 2001, p. 29.]
Applicable for electromagnetic interaction simplest form gauge symmetry. It turned out that the symmetry of the weak interaction is more complicated than that of the electromagnetic one. This complexity is due to the complexity of the process itself, so to speak, the mechanism of weak interaction.
In the process of weak interaction, for example, the decay of a neutron occurs. Such particles as neutron, proton, electron and neutrino can participate in this process. Moreover, due to the weak interaction, the mutual transformation of particles occurs.
Conceptual provisions of the theory of "Great Unification"
In modern theoretical physics, two new conceptual schemes set the tone: the so-called "Grand Unified" theory and supersymmetry.
These scientific directions together lead to a very attractive idea, according to which all of nature is ultimately subject to the action of some kind of superpower, which manifests itself in various "persons". This force is powerful enough to create our Universe and endow it with light, energy, matter and structure. But superpower is more than just a creative principle. In it, matter, space-time and interaction are merged into an inseparable harmonious whole, generating such a unity of the Universe that no one had previously imagined. The purpose of science is, essentially, to seek such unity. [Ovchinnikov N. F. Structure and symmetry // System Research, M., 1969, p. 137.]
Based on this, there is a certain confidence in the unification of all phenomena of animate and inanimate nature within the framework of a single descriptive scheme. To date, four fundamental interactions or four forces in nature are known, responsible for all known interactions of elementary particles - strong, weak, electromagnetic and gravitational interactions. Strong interactions bind quarks together. Weak interactions are responsible for some types of nuclear decays. Electromagnetic forces act between electric charges, and gravitational forces act between masses. The presence of these interactions is a sufficient and necessary condition for the construction of the world around us. For example, without gravity, not only would there be no galaxies, stars and planets, but the Universe could not have arisen - after all, the very concepts of the expanding Universe and the Big Bang, from which space-time originates, are based on gravity. Without electromagnetic interactions, there would be no atoms, no chemistry or biology, and no solar heat and light. Without strong nuclear interactions, the nucleus would not exist, and consequently, atoms and molecules, chemistry and biology, and stars and the Sun could not generate heat and light due to nuclear energy.
Even weak nuclear forces play a role in the formation of the universe. Without them, nuclear reactions in the Sun and stars would be impossible, apparently, supernova explosions would not occur, and the heavy elements necessary for life could not spread in the Universe. Life might as well not exist. If we agree with the opinion that all these four completely different interactions, each of which is necessary in its own way for the emergence of complex structures and determining the evolution of the entire Universe, are generated by a single simple superpower, then the presence of a single fundamental law that operates both in living and in inanimate nature, is beyond doubt. Modern research shows that at one time these four forces could have been combined into one.
This was possible at the enormous energies characteristic of the era of the early universe shortly after the Big Bang. Indeed, the theory of unification of electromagnetic and weak interactions has already been confirmed experimentally. Theories of "Grand Unification" should combine these interactions with strong ones, and theories of "All That Is" should describe all four fundamental interactions in a unified way as manifestations of one interaction. Thermal history of the Universe, starting from 10–43 sec. after the Big Bang and up to the present day, shows that most of the helium-4, helium-3, deuterons (nuclei of deuterium - a heavy isotope of hydrogen) and lithium-7 were formed in the Universe approximately 1 minute after the Big Bang.
Heavier elements appeared inside stars tens of millions or billions of years later, and the emergence of life corresponds to the final stage of the evolving Universe. Based on the theoretical analysis carried out and the results of computer simulation of dissipative systems operating far from equilibrium, under the action of a code-frequency low-energy flow, we concluded that there are two parallel processes in the Universe - entropy and information. Moreover, the entropy process of transformation of matter into radiation is not dominant. [Soldatov VK Theory of the "Great Unification". - M., Postscript, 2000, p. 38.]
Under these conditions, a new type of evolutionary self-organization of matter arises, linking the coherent space-time behavior of the system with dynamic processes within the system itself. Then, on the scale of the Universe, this law will be formulated as follows: "If the Big Bang led to the formation of 4 fundamental interactions, then the further evolution of the space-time organization of the Universe is connected with their unification." Thus, in our view, the law of entropy increase must be applied not to individual parts of the Universe, but to the entire process of its evolution. At the moment of its formation, the Universe turned out to be quantized according to the space-time levels of the hierarchy, each of which corresponds to one of the fundamental interactions. The resulting fluctuation, perceived as an expanding picture of the Universe, at a certain moment proceeds to restore its equilibrium. The process of further evolution takes place in a mirror image.
In other words, two processes take place simultaneously in the observable universe. One process - anti-entropy - is associated with the restoration of disturbed equilibrium, by self-organization of matter and radiation into macroquantum states (as a physical example, such well-known states of matter as superfluidity, superconductivity and the quantum Hall effect can be cited). This process, apparently, determines the consistent evolution of thermonuclear fusion processes in stars, the formation of planetary systems, minerals, flora, unicellular and multicellular organisms. This automatically follows the self-organizing orientation of the third principle of the progressive evolution of living organisms.
Another process is purely entropic in nature and describes the processes of cyclic evolutionary transition of self-organizing matter (decay - self-organization). It is possible that these principles can serve as the basis for creating a mathematical apparatus that allows you to combine all four interactions into one superpower. As already noted, it is precisely this problem that the majority of theoretical physicists are currently occupied with. Further argumentation of this principle goes far beyond the scope of this article and is connected with the construction of the theory of the Evolutionary Self-Organization of the Universe. Therefore, let us make the main conclusion and see how applicable it is to biological systems, the principles of their control, and most importantly, to new technologies for the treatment and prevention of pathological conditions of the body. First of all, we will be interested in the principles and mechanisms of maintaining the self-organization and evolution of living organisms, as well as the causes of their violations, manifested in the form of various pathologies.
The first of them is the principle of code-frequency control, the main purpose of which is to maintain, synchronize and control energy flows within any open self-organizing dissipative system. The implementation of this principle for living organisms requires the presence at each structural hierarchical level of a biological object (molecular, subcellular, cellular, tissue, organoid, organismic, population, biocenotic, biotic, landscape, biospheric, cosmic) the presence of a biorhythmological process associated with the consumption and consumption of transformable energy, which determines the activity and sequence of processes within the system. This mechanism occupies a central place in the early stages of the emergence of life in the formation of the DNA structure and the principle of reduplication of discrete codes of hereditary information, as well as in such processes as cell division and subsequent differentiation. As you know, the process of cell division always occurs in a strict sequence: prophase, metaphase, telophase, and then anaphase. You can violate the conditions of division, prevent it, even remove the nucleus, but the sequence will always be preserved. Without a doubt, our body is equipped with the most perfect synchronizers: a nervous system that is sensitive to the slightest changes in the external and internal environment, a slower humoral system. At the same time, the infusoria-shoe, in the complete absence of the nervous and humoral systems, lives, feeds, excretes, reproduces, and all these complex processes do not proceed randomly, but in strict sequence: any reaction predetermines the next, and that, in turn, allocates products needed to start the next reaction. [Soldatov VK Theory of the "Great Unification". - M., Postscript, 2000, p. 59.]
It should be noted that even Einstein's theory marked such an important progress in understanding nature that soon a revision of views on other forces of nature also became inevitable. At this time, the only "other" force whose existence was firmly established was the electromagnetic force. However, outwardly it did not look like gravity at all. Moreover, a few decades before the creation of Einstein's theory of gravity, Maxwell's theory successfully described electromagnetism, and there was no reason to doubt the validity of this theory.
Throughout his life, Einstein dreamed of creating a unified field theory in which all the forces of nature would merge together on the basis of pure geometry. Einstein devoted most of his life to the search for such a scheme after the creation of the general theory of relativity. However, ironically, the closest thing to the realization of Einstein's dream came the little-known Polish physicist Theodor Kaluza, who, back in 1921, laid the foundations for a new and unexpected approach to unifying physics, which still boggles the imagination with its audacity.
With the discovery of weak and strong interactions in the 1930s, the ideas of unifying gravity and electromagnetism largely lost their appeal. A consistent unified field theory was supposed to include not two, but four forces. Obviously, this could not be done without achieving a deep understanding of the weak and strong interactions. In the late 1970s, thanks to a fresh breeze brought by the Grand Unified Theories (GUT) and supergravity, the old Kaluza-Klein theory was remembered. She was "dusted off, dressed in fashion" and included in it all the interactions known today.
In the GUT, the theorists managed to collect three very different types of interactions within the framework of one concept; this is due to the fact that all three interactions can be described using gauge fields. The main property of gauge fields is the existence of abstract symmetries, thanks to which this approach acquires elegance and opens up wide possibilities. The presence of force field symmetries quite definitely indicates the manifestation of some hidden geometry. In the Kaluza-Klein theory brought back to life, the symmetries of gauge fields acquire concreteness - these are geometric symmetries associated with additional dimensions of space.
As in the original version, interactions are introduced into the theory by adding additional spatial dimensions to space-time. However, since we now have to accommodate three types of interactions, we have to introduce a few extra dimensions. A simple count of the number of symmetry operations involved in the GUT leads to a theory with seven additional spatial dimensions (so that their total number reaches ten); if time is taken into account, then the whole space-time has eleven dimensions. [Soldatov VK Theory of the "Great Unification". - M., Postscript, 2000, p. 69.]
The main provisions of the theory of "Grand Unification" from the point of view of quantum physics
In quantum physics, each length scale is associated with an energy (or equivalent mass) scale. The smaller the length scale under study, the higher the energy required for this. To study the quark structure of the proton requires energies equivalent to at least ten times the mass of the proton. Much higher on the energy scale is the mass corresponding to the Great Unification. If we ever manage to achieve such a huge mass (energy), which we are very far from today, then it will be possible to study the world of X-particles, in which the distinctions between quarks and leptons are erased.
What kind of energy is needed to penetrate "inside" the 7-sphere and explore additional dimensions of space? According to the Kaluza-Klein theory, it is required to exceed the scale of the Grand Unification and reach energies equivalent to 10 19 proton masses. Only with such unimaginably huge energies would it be possible to directly observe the manifestations of additional dimensions of space.
This huge value - 10 19 proton masses - is called the Planck mass, since it was first introduced by Max Planck, the creator of quantum theory. With an energy corresponding to the Planck mass, all four interactions in nature would merge into a single superforce, and ten spatial dimensions would be completely equal. If it were possible to concentrate a sufficient amount of energy, "ensuring the achievement of the Planck mass, then the full dimension of space would manifest itself in all its splendor. [Yakushev A. S. Basic concepts of modern natural science. - M., Fact-M, 2001, p. 122. ]
Giving free rein to the imagination, one can imagine that one day humanity will master the superpower. If this happened, then we would gain power over nature, since superpower ultimately gives rise to all interactions and all physical objects; in this sense, it is the fundamental principle of all things. Having mastered the superpower, we could change the structure of space and time, bend the void in our own way and put matter in order. By controlling the superpower, we could create or transform particles at will, generating new exotic forms of matter. We could even manipulate the dimensionality of space itself, creating bizarre artificial worlds with unthinkable properties. We would truly be masters of the universe!
But how can this be achieved? First of all, you need to get enough energy. To give an idea of what we are talking about, recall that the linear accelerator at Stanford, 3 km long, accelerates electrons to energies equivalent to 20 proton masses. To achieve the Planck energy, the accelerator would have to be extended by a factor of 1018, making it the size of the Milky Way (about a hundred thousand light years). Such a project is not one of those that can be implemented in the foreseeable future. [Wheeler J.A. Quantum and Universe // Astrophysics, quanta and theory of relativity, M., 1982, p. 276.]
There are three distinct thresholds, or scales, of energy in the Grand Unified Theory. First of all, this is the Weinberg–Salam threshold, equivalent to almost 90 proton masses, above which the electromagnetic and weak interactions merge into a single electroweak one. The second scale, corresponding to 10 14 proton masses, is characteristic of the Great Unification and the new physics based on it. Finally, the ultimate scale, the Planck mass, equivalent to 10 19 proton masses, corresponds to the complete unification of all interactions, as a result of which the world is amazingly simplified. One of the biggest unresolved problems is explaining the existence of these three scales, as well as the reasons for such a strong difference between the first and second of them. [Soldatov VK Theory of the "Great Unification". - M., Postscript, 2000, p. 76.]
Modern technology is capable of achieving only the first scale. The decay of the proton could give us an indirect means to study the physical world on the scale of the Grand Unification, although at present there seems to be no hope of directly reaching this limit, let alone on the scale of the Planck mass.
Does this mean that we will never be able to observe the manifestations of the original superpower and the invisible seven dimensions of space. Using such technical means as the superconducting supercollider, we are rapidly moving up the scale of energies achievable under terrestrial conditions. However, the technology created by people by no means exhausts all the possibilities - there is nature itself. The Universe is a gigantic natural laboratory in which the greatest experiment in the field of elementary particle physics was "carried out" 18 billion years ago. We call this experiment the Big Bang. As will be discussed later, this initial event was enough to release - albeit for a very short moment - superpower. However, this, apparently, was enough for the ghostly existence of a superpower to forever leave its mark. [Yakushev A. S. Basic concepts of modern natural science. - M., Fact-M, 2001, p. 165.]
In 1896, the French scientist Henri Becquerel discovered the radioactivity of uranium. This was the first experimental signal about previously unknown forces of nature - the weak interaction. We now know that the weak force is behind many familiar phenomena - for example, it takes part in some thermonuclear reactions that support the radiation of the Sun and other stars.
The name "weak" went to this interaction due to a misunderstanding - for example, for a proton it is 1033 times stronger gravitational interaction(see Gravity, Unity of the forces of nature). Rather, it is a destructive interaction, the only force of nature that does not hold matter together, but only destroys it. One could also call it "unprincipled", since in destruction it does not take into account the principles of spatial parity and temporal reversibility, which other forces observe.
The basic properties of the weak interaction became known as early as the 1930s, mainly due to the work of the Italian physicist E. Fermi. It turned out that, unlike gravitational and electrical forces, weak forces have a very small radius of action. In those years, it seemed that there was no radius of action at all - the interaction takes place at one point in space, and, moreover, instantly. This interaction is virtual a short time) turns each proton of the nucleus into a neutron, a positron into a positron and a neutrino, and each neutron into a proton, an electron and an antineutrino. In stable nuclei (see atomic nucleus) these transformations remain virtual, like the virtual production of electron-positron pairs or proton-antiproton pairs in vacuum. If the difference in the masses of nuclei that differ by one in charge is large enough, these virtual transformations become real, and the nucleus changes its charge by 1, throwing out an electron and an antineutrino (electron β-decay) or a positron and neutrino (positron β-decay). Neutrons have a mass that is approximately 1 MeV greater than the sum of the masses of a proton and an electric wave. Therefore, a free neutron decays into a proton, an electron, and an antineutrino with an energy release of approximately 1 MeV. The lifetime of a free neutron is about 10 minutes, although in a bound state, for example, in a deuteron, which consists of a neutron and a proton, these particles live indefinitely.
A similar event occurs with the muon (see Leptons) - it decays into an electron, a neutrino and an antineutrino. Before decaying, the muon lives for about 10 -6 s - much less than the neutron. Fermi's theory explained this by the difference in the masses of the particles involved. The more energy released during decay, the faster it goes. The release of energy during μ-decay is about 100 MeV, approximately 100 times greater than during neutron decay. The lifetime of a particle is inversely proportional to the fifth power of this energy.
As it turned out in recent decades, the weak interaction is nonlocal, i.e., it does not occur instantly and not at one point. According to modern theory, weak interaction is not transmitted instantly, and a virtual electron-antineutrino pair is born 10 -26 s after the muon passes into a neutrino, and this happens at a distance of 10 -16 cm. Not a single ruler, not a single microscope can , of course, to measure such a small distance, just as no stopwatch can measure such a small interval of time. As is almost always the case, in modern physics we must be content with circumstantial evidence. Physicists build various hypotheses about the mechanism of the process and test all possible consequences of these hypotheses. Those hypotheses that contradict at least one reliable experiment are swept aside, and new experiments are put to verify the remaining ones. This process in the case of the weak interaction continued for about 40 years, until physicists came to the conclusion that the weak interaction is carried by supermassive particles - 100 times heavier than the proton. These particles have spin 1 and are called vector bosons (discovered in 1983 at CERN, Switzerland - France).
There are two charged vector bosons W + , W - and one neutral Z 0 (the icon at the top, as usual, indicates the charge in proton units). The charged vector boson W - "works" in the decays of the neutron and muon. The course of muon decay is shown in Fig. (above, right). Such drawings are called Feynman diagrams, they not only illustrate the process, but also help to calculate it. This is a kind of shorthand formula for the probability of a reaction; it is used here for illustration only.
The muon turns into a neutrino, emitting a W-boson, which decays into an electron and an antineutrino. The released energy is not enough for the real birth of the W-boson, so it is born virtually, i.e., for a very short time. AT this case this is 10 -26 s. During this time, the field corresponding to the W-boson does not have time to form a wave, or otherwise, a real particle (see Fields and particles). A field bunch 10 -16 cm in size is formed, and after 10 -26 s an electron and an antineutrino are born from it.
For the decay of the neutron, one could draw the same diagram, but here it would already mislead us. The fact is that the size of a neutron is 10 -13 cm, which is 1000 times greater than the radius of action weak forces. Therefore, these forces act inside the neutron, where the quarks are located. One of the three quarks of the neutron emits a W-boson, while passing into another quark. The quark charges in the neutron are -1/3, -1/3, and +2/3, so that one of the two quarks with a negative charge of -1/3 goes over to a quark with a positive charge of +2/3. The result will be quarks with charges -1/3, 2/3, 2/3, which together make up the proton. The reaction products - an electron and an antineutrino - freely fly out of the proton. But after all, the quark that emitted the W-boson received a recoil and began to move in opposite direction. Why doesn't he fly?
It is held by the strong force. This interaction will drag its two inseparable satellites behind the quark, resulting in a moving proton. The weak decays (associated with the weak interaction) of the remaining hadrons occur according to a similar scheme. All of them come down to the emission of a vector boson by one of the quarks, the transition of this vector boson into leptons (μ-, e-, τ- and ν-particles) and further expansion of the reaction products.
Sometimes, however, hadronic decays also occur: a vector boson can decay into a quark-antiquark pair, which will turn into mesons.
So, a large number of various reactions is reduced to the interaction of quarks and leptons with vector bosons. This interaction is universal, that is, it is the same for quarks and leptons. The universality of the weak interaction, in contrast to the universality of the gravitational or electromagnetic interaction, has not yet received an exhaustive explanation. In modern theories, the weak interaction is combined with the electromagnetic interaction (see Unity of the Forces of Nature).
For symmetry breaking by the weak interaction, see Parity, Neutrino. The article The unity of the forces of nature tells about the place of weak forces in the picture of the microworld.
In 1896, the French scientist Henri Becquerel discovered the radioactivity of uranium. This was the first experimental signal about previously unknown forces of nature - the weak interaction. We now know that the weak force is behind many familiar phenomena - for example, it takes part in some thermonuclear reactions that support the radiation of the Sun and other stars.
The name "weak" went to this interaction due to a misunderstanding - for example, for a proton it is 1033 times stronger than the gravitational interaction (see Gravitation, Unity of this nature). Rather, it is a destructive interaction, the only force of nature that does not hold matter together, but only destroys it. One could also call it "unprincipled", since in destruction it does not take into account the principles of spatial parity and temporal reversibility, which other forces observe.
The basic properties of the weak interaction became known as early as the 1930s, mainly due to the work of the Italian physicist E. Fermi. It turned out that, unlike gravitational and electrical forces, weak forces have a very small radius of action. In those years, it seemed that there was no radius of action at all - the interaction takes place at one point in space, and, moreover, instantly. This interaction virtually (for a short time) turns each proton of the nucleus into a neutron, a positron into a positron and a neutrino, and each neutron into a proton, an electron and an antineutrino. In stable nuclei (see atomic nucleus) these transformations remain virtual, like the virtual production of electron-positron pairs or proton-antiproton pairs in vacuum.
If the difference in the masses of nuclei that differ by one in charge is large enough, these virtual transformations become real, and the nucleus changes its charge by 1, throwing out an electron and an antineutrino (electron-decay) or a positron and a neutrino (positron-decay). Neutrons have a mass that is approximately 1 MeV greater than the sum of the masses of a proton and an electron. Therefore, a free neutron decays into a proton, an electron, and an antineutrino with an energy release of approximately 1 MeV. The lifetime of a free neutron is about 10 minutes, although in a bound state, for example, in a deuteron, which consists of a neutron and a proton, these particles live indefinitely.
A similar event occurs with the muon (see Peptons) - it decays into an electron, a neutrino and an antineutrino. Before decaying, the muon lives about c - much less than the neutron. Fermi's theory explained this by the difference in the masses of the particles involved. The more energy released during decay, the faster it goes. The release of energy during -decay is about 100 MeV, approximately 100 times greater than during the decay of a neutron. The lifetime of a particle is inversely proportional to the fifth power of this energy.
As it turned out in recent decades, the weak interaction is nonlocal, i.e., it does not occur instantly and not at one point. According to modern theory, weak interaction is not transmitted instantly, and a virtual electron-antineutrino pair is born in c after the muon passes into a neutrino, and this happens at a distance of cm. Not a single ruler, not a single microscope, of course, can measure such a small distance, just as no stopwatch can measure such a small interval of time. As is almost always the case, in modern physics we must be content with circumstantial evidence. Physicists build various hypotheses about the mechanism of the process and test all possible consequences of these hypotheses. Those hypotheses that contradict at least one reliable experiment are swept aside, and new experiments are put to verify the remaining ones. This process in the case of the weak interaction continued for about 40 years, until physicists came to the conclusion that the weak interaction is carried by supermassive particles - 100 times heavier than the proton. These particles have spin 1 and are called vector bosons (discovered in 1983 at CERN, Switzerland - France).
There are two charged vector bosons and one neutral (the icon at the top, as usual, indicates the charge in proton units). A charged vector boson "works" in the decays of a neutron and a muon. The course of muon decay is shown in Fig. (above, right). Such drawings are called Feynman diagrams, they not only illustrate the process, but also help to calculate it. This is a kind of shorthand formula for the probability of a reaction; it is used here for illustration only.
The muon transforms into a neutrino, emitting a -boson, which decays into an electron and an antineutrino. The released energy is not enough for the real production of -boson, so it is born virtually, ie, for a very short time. In this case it is s. During this time, the field corresponding to the -boson does not have time to form a wave, or otherwise, a real particle (see Fields and particles). A cm-sized field bunch is formed, and after c an electron and an antineutrino are born from it.
For the decay of the neutron, one could draw the same diagram, but here it would already mislead us. The fact is that the size of a neutron is cm, which is 1000 times greater than the range of weak forces. Therefore, these forces act inside the neutron, where the quarks are located. One of the three quarks of the neutron emits a -boson, while passing into another quark. Charges of quarks in a neutron: -1/3, - 1/3 and so one of the two quarks with a negative charge -1/3 passes into a quark with a positive charge. The result will be quarks with charges - 1/3, 2/3, 2/3, which together make up the proton. The reaction products - an electron and an antineutrino - freely fly out of the proton. But it's a quark that emitted a -boson. received feedback and began to move in the opposite direction. Why doesn't he fly?
It is held by the strong force. This interaction will drag its two inseparable satellites behind the quark, resulting in a moving proton. The weak decays (associated with the weak interaction) of the remaining hadrons occur according to a similar scheme. All of them are reduced to the emission of a vector boson by one of the quarks, the transition of this vector boson into leptons (, and -particles) and the further expansion of the reaction products.
Sometimes, however, hadronic decays also occur: a vector boson can decay into a quark-antiquark pair, which will turn into mesons.
So, a large number of different reactions are reduced to the interaction of quarks and leptons with vector bosons. This interaction is universal, that is, it is the same for quarks and leptons. The universality of the weak interaction, in contrast to the universality of the gravitational or electromagnetic interaction, has not yet received an exhaustive explanation. In modern theories, the weak interaction is combined with the electromagnetic interaction (see Unity of the Forces of Nature).
For symmetry breaking by the weak interaction, see Parity, Neutrino. The article The unity of the forces of nature tells about the place of weak forces in the picture of the microworld
This interaction is the weakest of the fundamental interactions experimentally observed in the decays of elementary particles, where quantum effects are fundamentally significant. Recall that quantum manifestations of gravitational interaction have never been observed. The weak interaction is distinguished by next rule: if an elementary particle, called a neutrino (or antineutrino), participates in the interaction process, then this interaction is weak.
The weak interaction is much more intense than the gravitational one.
The weak interaction, in contrast to the gravitational one, is short-range. This means that the weak interaction between particles only comes into play if the particles are close enough to each other. If the distance between the particles exceeds a certain value, called the characteristic radius of interaction, the weak interaction does not manifest itself. It has been experimentally established that the characteristic radius of the weak interaction of the order of 10-15 cm, that is, the weak interaction, is concentrated at distances smaller sizes atomic nucleus.
Why can we talk about the weak interaction as an independent form of fundamental interactions? The answer is simple. It has been established that there are processes of transformations of elementary particles that cannot be reduced to gravitational, electromagnetic and strong interactions. Good example, showing that there are three qualitatively different interactions in nuclear phenomena, is associated with radioactivity. Experiments indicate the presence of three various kinds radioactivity: a-, b and g-radioactive decays. In this case, a-decay is due to strong interaction, g-decay - electromagnetic. The remaining b-decay cannot be explained by the electromagnetic and strong interactions, and we are forced to accept that there is another fundamental interaction called the weak one. In the general case, the need to introduce a weak interaction is due to the fact that processes occur in nature in which electromagnetic and strong decays are prohibited by conservation laws.
Although the weak interaction is essentially concentrated inside the nucleus, it has certain macroscopic manifestations. As we have already noted, it is associated with the process of b-radioactivity. In addition, the weak interaction plays an important role in the so-called thermonuclear reactions responsible for the mechanism of energy release in stars.
The most amazing property of the weak interaction is the existence of processes in which mirror asymmetry is manifested. At first glance, it seems obvious that the difference between the concepts of left and right is arbitrary. Indeed, the processes of gravitational, electromagnetic, and strong interactions are invariant with respect to spatial inversion, which implements mirror reflection. It is said that in such processes the spatial parity P is conserved. However, it has been experimentally established that weak processes can proceed with nonconservation of spatial parity and, therefore, seem to feel the difference between left and right. At present, there is solid experimental evidence that parity nonconservation in weak interactions is of a universal nature; it manifests itself not only in the decays of elementary particles, but also in nuclear and even atomic phenomena. It should be recognized that mirror asymmetry is a property of Nature at the most fundamental level.
All charged bodies, all charged elementary particles participate in electromagnetic interaction. In this sense, it is quite universal. The classical theory of electromagnetic interaction is Maxwellian electrodynamics. The electron charge e is taken as the coupling constant.
If we consider two resting point charge q1 and q2, then their electromagnetic interaction will be reduced to a known electrostatic force. This means that the interaction is long-range and slowly decreases with increasing distance between charges. A charged particle emits a photon, whereby the state of its motion changes. Another particle absorbs this photon and also changes the state of its motion. As a result, the particles seem to feel the presence of each other. It is well known that electric charge is a dimensional value. It is convenient to introduce the dimensionless coupling constant of the electromagnetic interaction. To do this, we need to use the fundamental constants and c. As a result, we arrive at the following dimensionless coupling constant, called in atomic physics fine structure constant
It is easy to see that this constant significantly exceeds the constants of the gravitational and weak interactions.
From a modern point of view, the electromagnetic and weak interactions are various parties unified electroweak interaction. A unified theory of the electroweak interaction has been created - the Weinberg-Salam-Glashow theory, which explains from a unified position all aspects of electromagnetic and weak interactions. Is it possible to understand at a qualitative level how the unified interaction is divided into separate, as it were, independent interactions?
As long as the characteristic energies are small enough, the electromagnetic and weak interactions are separated and do not affect each other. As the energy increases, their mutual influence begins, and at sufficiently high energies these interactions merge into a single electroweak interaction. The characteristic unification energy is estimated in order of magnitude as 102 GeV (GeV is short for gigaelectronvolt, 1 GeV = 109 eV, 1 eV = 1.6 10-12 erg = 1.6 1019 J). For comparison, we note that the characteristic energy of an electron in the ground state of a hydrogen atom is about 10-8 GeV, the characteristic binding energy of an atomic nucleus is about 10-2 GeV, the characteristic binding energy solid body about 10-10 GeV. Thus, the characteristic energy of the unification of electromagnetic and weak interactions is enormous compared to the characteristic energies in atomic and nuclear physics. For this reason, electromagnetic and weak interactions do not manifest their common essence in ordinary physical phenomena.
The strong force is responsible for the stability of atomic nuclei. Since the atomic nuclei of most chemical elements stable, it is clear that the interaction that keeps them from breaking up must be strong enough. It is well known that nuclei are made up of protons and neutrons. To prevent positively charged protons from scattering into different sides, it is necessary to have attractive forces between them that exceed the forces of electrostatic repulsion. It is the strong interaction that is responsible for these attractive forces.
A characteristic feature of the strong interaction is its charge independence. The nuclear forces of attraction between protons, between neutrons, and between a proton and a neutron are essentially the same. From this it follows that from the point of view of strong interactions, the proton and neutron are indistinguishable and the single term nucleon is used for them, that is, a particle of the nucleus.
So, we have made a review of the basic information concerning the four fundamental interactions of Nature. The microscopic and macroscopic manifestations of these interactions and the picture of physical phenomena in which they play an important role are briefly described.
