What Is Theoretical Physics?

Theoretical Physics is a discipline that theoretically explores the basic laws of matter structures, interactions, and movements of matter unknown in nature. The research field of theoretical physics involves particle physics and nuclear physics, statistical physics, condensed matter physics, cosmology, etc., and includes basic theoretical issues in almost all branches of physics.

Theoretical physics

Physics is an important part of modern human civilization. It continues to develop along with the progress of civilization. It is the fruit of human material creation and spiritual thinking. At the same time, it strongly promotes the further development of human civilization. It can be said that physics is one of the most important shaping forces in modern human society. It is not only the direct basis of various grand and precise material achievements, but also profoundly affects human philosophical, political, economic and cultural activities. In this way, we have reshaped human understanding of ourselves and the universe. Theoretical physics plays a fundamental role as an important branch of physics, and its functions and meanings not only fully meet the above aspects, but also have its own characteristics.

Research Scope of Theoretical Physics

Theoretical physics is based on experimental phenomena, using theoretical methods and models to study the basic laws of the movement of basic particles, nuclei, atoms, molecules, plasmas and condensed matter, and to solve basic theoretical problems raised in the discipline itself and in high-tech exploration . Research scope includes particle physics theory, atomic nucleus theory, condensed matter theory, statistical physics, photonics theory, atomic molecule theory, plasma theory, quantum field theory and quantum mechanics, gravity theory, mathematical physics, theoretical biophysics, nonlinear physics , Computational physics, etc.

Theoretical physics particle physics and quantum field theory

Particle physics is a frontier subject in physics that studies the microstructure of matter and the laws of basic interactions. As the basic theory of quantum field, particle physics theory has achieved great success. The establishment of a standard model of particle physics is one of the major achievements of physics in the twentieth century. It can uniformly describe the smallest "particles" currently known to mankind (quark, lepton, photon, gluon, intermediate boson, Higgs particles). Nature and strong, electric, weak three basic interactions. There are many research directions in particle physics, for example: hadron physics, heavy physics, leptonic physics, neutrino physics, exact test of standard model, symmetry and symmetry destruction, standard model extension, and so on.

Theoretical physics superstring theory and field theory

Quantum field theory is a basic tool for studying the microcosm and belongs to an important frontier. Its research results directly affect the progress of many branches of theoretical physics. String theory is a new physical model developed on the basis of quantum field theory. It avoids problems such as ultraviolet divergence encountered in field theory and is an important attempt to unify the four interaction theories.

Gravitational theory of theoretical physics and cosmology

Einstein's general theory of relativity is a very successful classical theory of gravity. The establishment of a self-consistent quantum theory of gravity by atomizing gravity is an important task of current theoretical physics. Compared with general relativity, scalar-tensor gravitational theory is very competitive. The application of general relativity in cosmology and astrophysics (including the prediction of the Big Bang universe model, neutron stars and black holes, gravitational lenses, and gravitational waves) has achieved great success, but many difficult problems remain to be solved. For example, singularity difficulties, the composition of dark matter and its existence form, physical properties, its proportion in the universe and its effect on the evolution of the universe, the asymmetry of matter antimatter, issues of cosmic constants and dark energy, primary nuclear synthesis, universe Topological defects in the early phase transition process, the establishment of an early inflation model of the universe, the quantum mechanics of black holes, and the holographic nature of gravity.

Several large-scale international space and ground astronomical observation devices (including large telescopes, gravitational wave astronomical stations, equivalent principle inspection devices, etc.) will be put into use in the next few years. This will affect existing cosmological models, gravitational wave The predictions and the correctness of the equivalence principle provide a more accurate test, and the rapid development of cosmology and gravity theory will follow, which will provide more opportunities for theoretical work to obtain important results.

Theoretical Physics Condensed Matter Theory and Computational Condensed Matter Physics

Complexity and diversity are the basic characteristics of the multi-body micro-quantum world. The exploration of its regularity is the core of condensed matter theory research. Every breakthrough in this area, such as the establishment of the band theory and superconducting BCS theory, has profoundly changed the application of quantum multibody physics and the understanding of the microworld, and its achievements have cross-penetrated into mathematics, chemistry, materials, and information. , Computer and many other disciplines and fields. A large number of anomalous physical phenomena found in ceramic materials, semiconductor heterojunctions and other low-dimensional solid materials call for the birth of a new electron theory. Research on these new physical phenomena is a central task for researchers. The main research directions include:

Physical mechanism, quantum liquid and quantum criticality of strong correlation systems such as quantum Hall effect, high temperature superconductivity, and giant magnetoresistance;

Exploration and application of quantum multibody theory methods, especially numerical calculation methods. Calculation methods include density matrix renormalization group, quantum Monte-Carlo calculation, ab initio calculation, etc .;

Non-equilibrium quantum transport and spin electronics in nanomaterials such as quantum dots, wires, carbon tubes, semiconductor materials or structures

Research on quantum backscatter and integrability in lattice systems.

Theoretical Physics, Statistical Physics and Theoretical Life Sciences

The research methods of statistical physics are extremely common and have a wide range of research objects. It is a micro-to-macro bridge, simple to complex ladder, and theory to application. From sequence analysis of biological macromolecules to understanding its spatial structure to understanding the physical and chemical processes in life activities, life sciences have raised a number of challenging statistical and physical problems. The study of these issues will deepen the understanding of the nature of life phenomena, and will also promote the development of statistical physics itself.

Theoretical physics

Amphiphilic molecular membranes are the frontier research objects of condensed-state physical soft substances, or complex fluids, and are the research subjects of the interdisciplinary fields of physics, chemistry, and biology. The research in this direction is expanding towards the theoretical exploration of single molecular membranes, biological macromolecules and their biological functions (DNA single molecule elasticity, protein folding, etc.).

Theory of nuclear physics

From the mid-1990s to the beginning of this century, a number of very large nuclear physics experimental devices have been put into operation internationally, such as TJNAF (CEBAF), RIB, RHIC, etc., the development of nuclear physics has entered a new stage. These new giant devices provide a good opportunity to study nucleus-nucleus interactions, short-range behavior and structure within the nucleus, nuclear phenomena under various extreme conditions, nuclear properties, and multibody theoretical methods at a deeper level. .

Theoretical physics, quantum physics, quantum information, and atomic molecular theory

The development of high technology enables extreme physical conditions that were not available in the past (such as extreme strong fields, ultra-low temperatures, and controllable mesoscopic scales) to be realized in the laboratory. Under these special conditions, the process of interaction between matter and light field will present a series of brand-new physical phenomena, making people re-understand the basic problems of physics, leading to the establishment of emerging branches of science (such as quantum information).

Quantum information is based on the basic principles of quantum mechanics and makes full use of the unique properties of quantum coherence (quantum parallelism and quantum entanglement) to explore the possibility of computing, encoding and information transmission in a completely new way, providing a breakthrough to the limit of the chip component scale New concepts, new ideas and new approaches. The combination of quantum mechanics and information science fully shows the importance of interdisciplinarity, which may lead to major changes in information science concepts and models.

Theoretical physics computational physics

The symplectic algorithm and the structure-preserving algorithm were proposed, improved and developed systematically by the famous mathematician Feng Kang and his school in the mid-1980s. Their work in this field has not only been leading, but also holds a very important position in the field of computational mathematics and has gained international recognition. In computational mathematics and computational physics, it is very important to introduce the idea of maintaining the symplectic structure of the calculated Hamilton system, or the geometry of the retaining system, such as a contact system. There are new developments in the related fields along the lines of international structural protection. For example, the polysymplectic algorithm and the Lie group algorithm are proposed, etc. They are an algorithm to maintain the polysymple structure of an infinite-dimensional system and an algorithm of the Lie group symmetry of the system.