There have been two important revolutions in physics in this century: relativity and quantum mechanics. Recently, the development of superstring theory has been predicted by many famous physicists as the beginning of the third revolution in physics. The achievements of these developments will change people's concept of time and space, and the unified theory will fundamentally solve a series of problems such as infinity in quantum field theory, quark confinement in the standard model of particle physics, and too many arbitrary parameters.
The most basic purpose of physics is to seek the unified law of material movement in nature. This purpose has never changed since the birth of physics. Newton's gravity theory and the mechanical law of object motion unify the movement of celestial bodies with the movements often seen in daily life, such as the fall of apples; Maxwell's electromagnetic theory unifies two different phenomena: electricity and magnetism. Einstein spent the rest of his life seeking a unified theory of the interaction between gravity and electromagnetic force, but failed; The unified theory of electromagnetic interaction and weak interaction was put forward in the late 1960s, and the standard model in particle physics is the most successful theory. It is theoretically predicted that the anomalous magnetic moment of phonon is1.001159652193 Bohr magneton, and the experimental value is 1.05438+063. There are many attempts to seek a larger and more perfect unified theory including strong interaction and gravity. These attempts, such as grand unification theory, high-dimensional Kaluza-Klein theory and supersymmetric supergravity theory, have all failed, and only superstring theory is the most promising. The theoretical basis of the standard model is quantum field theory. Because quantum field theory has infinite degrees of freedom, it is very difficult to accurately solve the interaction quantum field theory, which is considered impossible. In this case, people can only use perturbation theory (a small amount of expansion) to find approximate solutions to solve the problem. Obviously, in those cases where there is no small expansion and strong interaction, the perturbation method is powerless. There are many problems involving strong interaction in particle physics, the most famous of which is quark confinement: many experiments and theoretical discoveries require the existence of a class of elementary particles called quarks. These quarks are not very heavy and should be easily produced on the accelerator. Strangely, no single free quark was observed in the experiment. The theoretical explanation is that the interaction between two quarks becomes stronger with the increase of distance. The energy of separating two quarks also increases with the distance. Therefore, the interaction involved in quark confinement is very strong at a great distance, and the usual perturbation theory can not be used to approximate the solution.
1994, a series of works by American physicists Seeberger and Witten made a breakthrough in solving quantum field theory strictly, and proved theoretically for the first time that the condensation of magnetic monopoles gave quarks confinement.
Seiberg and Witten's work mainly discusses the problem of solving N =2 supersymmetric gauge theory. The basic particles in nature are divided into two categories: bosons and fermions, which are completely different in statistical properties. Supersymmetry is a symmetry about bosons and fermions, and N =2 supersymmetry is stronger than the most basic N = 1 supersymmetry. The standard model of particle physics mentioned above is not supersymmetric theory (N =0, the results of Seiberg-Witten can not be used to solve practical theoretical problems immediately. In the theory considered by Seiberg-Witten, magnetic monopole plays a very important role. Magnetic monopole was first discussed theoretically by British physicist Dirac in the early 1930s. Later, in the mid-1970s, it aroused great interest because of its appearance in the grand unified model and other models. Because no magnetic monopoles were found in the experiment, it is generally believed that magnetic monopoles are very heavy, and they only came into being and played a role when the universe was formed in the early days. In the supersymmetric gauge theory with N =2, the properties of magnetic monopole are very strange: with the change of theoretical parameters, the intensity of interaction becomes stronger and stronger, and the magnetic monopole will be transformed into particles with zero mass. Seiberg-Witten proved that the theory actually has another equivalent dual description. Under the dual description, electricity and magnetism are the magnetism and electricity in the original theory, and they are interchangeable. Electrons and magnetic monopoles are interchangeable, and so are strong interactions and weak interactions. Therefore, we can use this dual transformation to turn the strong interaction problem into a weak interaction problem, and then use perturbation theory to solve the approximate solution. In duality theory, quark confinement is actually a common superconducting phenomenon. At this time, two magnetic monopoles combine to give a gauge field with mass and form an energy gap. In the original theory, this leads to the confinement of electric flux, which is given by charged quarks, and the confinement of electric flux is quark confinement. Because the combination of magnetic monopoles is given by a supersymmetric mass term from N=2 to N= 1, the above results actually prove that N= 1 is supersymmetric.
This theory has quark confinement.
By using Seiberg-Witten theory, a large number of supersymmetric gauge theories with N= 1 and N=2 can be solved and discussed qualitatively. Undoubtedly, these results and methods will be partially applied to common asymmetric theories such as the standard model. Mathematically, by using the results of Seiberg-Witten, a set of powerful and effective new methods for studying the differential topological properties of four-dimensional manifolds have been successfully developed. In addition, the study of duality has triggered a new understanding of superstring theory, and these breakthroughs have been speculated by many famous physicists as another important revolution in physics after relativity and quantum mechanics in this century.
Superstring theory is a self-consistent theory that people abandon the assumption that the basic particle is a point particle and replace it with the assumption that the basic particle is a one-dimensional chord. All kinds of particles in nature are different vibration modes of strings. String theory was put forward about 30 years ago to solve the problem of strong interaction. Later, people found that superstring theory is actually a unified theory, which naturally needs the existence of gravity, including electromagnetism, weak interaction and strong interaction described by gauge field. It is also found that there are only five self-consistent superstring theories in theory, and it is speculated that these theories are still related. The research on various forms of duality in recent two years proves that these five different superstring theories are interrelated, and the sixth theory is not superstring. Presumably, there should be a complete theory called M theory. The above six theories are only approximations of M theory, and can only be used to describe some properties of the same phenomenon, because these properties have become prominent under the consideration of approximation theory.
At present, a complete M theory has not been established, and people's understanding of M theory is still at the stage of collecting phenomena. American physicist Polczynski introduced D film two years ago, which simplified the discussion of parity. Subsequently, Wafa and Ster Luo Ming successfully applied quantum mechanics by using D film.
Moreover, the entropy of black holes is calculated according to the basic principles of statistical mechanics, which is completely consistent with the results of black hole thermodynamics, indicating that black holes actually have internal structures, and their properties are not contradictory to the basic principles of quantum mechanics. At the end of 1996, four American physicists put forward the expression of M theory, from which many previously known and unknown results can be deduced, which is encouraging. Physicists engaged in the study of superstring theory generally feel that they are in an era very similar to the eve of the establishment of quantum theory in the 1920s. The establishment of complete M theory and unified theory will fundamentally change people's concept of time and space, and its revolutionary significance is unpredictable.