For example—
phase transformation theory
Statistical mechanics is one of the main research directions of Yang Zhenning. His characteristic in statistical mechanics is to solve and analyze the general model rooted in physical reality strictly, so as to grasp the essence and essence of the problem beautifully. From 65438 to 0952, Yang Zhenning and his collaborators published three important papers on phase transition. The first paper is about the spontaneous magnetization of two-dimensional Ising model, which he independently completed the year before last, and obtained the critical exponent of 1/8. This is the longest calculation that Yang Zhenning has ever done. Ising model is the most basic but extremely important model in statistical mechanics, but its importance in theoretical physics was not widely recognized until 1960s.
1952, Yang Zhenning also cooperated with Li Zhengdao to complete and publish two papers on phase transition theory. Two articles were submitted and published at the same time, which aroused Einstein's interest. In this paper, the analytic properties of giant partition function are studied by analytic continuation method, and it is found that the distribution of its roots determines the state equation and phase transition properties, which eliminates the suspicion that different thermodynamic phases can exist under the same interaction. The climax of these two papers is the unit circle theorem in the second paper, which points out that the zero point of the giant partition function of the lattice gas model attracting interaction lies on the unit circle on the complex plane. In statistical mechanics and field theory, this theoretical masterpiece is like a small and exquisite shell, and its charm is undiminished.
Young-Baxter equation
In 1960s, Yang Zhenning found the strict solution of quantum statistical model by trying to find off-diagonal long program model. 1967, it was found that the fermion quantum many-body problem in the repulsive potential of 1 dimensional δ function could be transformed into a matrix equation, which was later called Yang-Baxter equation (because Baxter also found this equation in another problem of 1972). In 1967, Yang Zhenning also wrote an article published in the following year, which further discussed the problem of S matrix. Later, it was found that Young-Baxter equation is an extremely important equation in mathematics and physics, which is closely related to kink theory, braid group, Hopf algebra and even string theory. The 1 dimensional fermion problem discussed by Yang Zhenning is very important in the experimental study of cold atoms in recent years, and the nested Bethe hypothesis method he invented in this paper was used by Lieb and Wu Fayue to solve the 1 dimensional Hubbard model the following year. Hubbard model later became the basis of many theoretical studies on high temperature superconductivity.
In addition to his outstanding achievements in physics, Yang Zhenning has done many great things for his motherland: for example-
(1) Yang Zhenning made many reports on China after his first visit to China. Because of his fame and position, his style and personality, his speeches and reports have played a great role in American society. At that time, Sino-American relations had not been completely thawed, so he took considerable risks.
He often goes to Europe, South America, Southeast Asia and Japan to give lectures or visit. Wherever he goes, people ask him to give a report on China. His report also had a great influence on the local overseas Chinese. Many Americans, especially scientists, are friendly to China and are willing to get close to China. Mr. Yang has made great contributions. At that time, various pressures from the authorities of the United States, the Soviet Union and Taiwan Province Province in China never wavered Yang Zhenning's determination and confidence. He insisted on coming to China at least once a year to show his innocence.
(2) For the development of education and science and technology in China, Yang Zhenning went back and forth tirelessly and visited dozens of universities in China. He has been employed as honorary professor or part-time professor by dozens of universities such as Fudan University, Sun Yat-sen University, Shanghai Jiaotong University, East China Normal University, China University of Science and Technology, Nankai University, Yunnan University, Peking University and Tsinghua University. Since 1998, the accumulation of physics research in China is largely related to the establishment of IAS by Yang Zhenning and Tsinghua in the teaching mode of science classes in Tsinghua University Physics Base, and the fields of condensed matter and cold atoms, especially those papers around 2008, which have made great contributions to the training of theoretical physics research teams in China. Condensed matter and cold atoms are just one of the areas where China bends to overtake and catch up with the world level.
Yang Zhenning's annual salary in Tsinghua University is 6,543,800 yuan, but he didn't donate anything to Tsinghua University Advanced Research Center. He also sold a big house in new york, USA, and donated $65,438+0,000 to Tsinghua. He also donated part of the Nobel Prize to Tsinghua.
Yang Zhenning has done so many things and made so many contributions to the motherland. What reason do we have to criticize such an excellent old man?