The year 2021 marks the 110th anniversary of the birth of Professor Shiing-Shen Chern. For celebrating "The Year of Shiing-Shen Chern", the Chern Institute of Mathematics (CIM) organized a series of commemorative activities. On December 3, 2021, Academician Weiping Zhang from CIM delivered a Special Lecture titled "Professor Shiing-Shen Chern's Academic Achievements" at 4 p.m. in Shiing-Shen Building. The Lecture was hosted by Director and Professor of CIM Chengming Bai. Academician Mo-Lin Ge, Academician William Y.C. Chen and Professor Zixin Hou, former president of Nankai University, were present at the lecture. Attendees also included leaders, teachers and students of mathematics and statistics disciplines. More than 800 people watched online.

*The Special Lecture takes place at CIM*

*Professor Weiping Zhang delivering lecture*

**Imprint of Professor Chern'****s Academic Achievements**

Professor Weiping Zhang started the lecture with a famous poem by Professor Chen-Ning Yang, the last five words of which refer to five great geometers in the history: Euclid, Gauss, Riemann, Cartan and Shiing-Shen Chern. The names show a development process of geometry: Euclid proved that the sum of the internal angles of triangles on the plane is 180 degrees. Gauss has the theorem for the sum of the internal angles of triangles surrounded by geodesics on the surface. Riemann introduced the concept of high-dimensional Riemannian space. When differential geometry began to study manifolds, which was also described as the period of "modern man" (see the picture below) according to Chern, Cartan was the representative of the first to generalize the theory of calculus to manifolds. Learning from his teacher Cartan, Chern introduced the concept of "transgression", gave a high-dimensional intrinsic proof of the Gauss-Bonnet theorem, innovated and introduced a characteristic class named after him.

*Professor Weiping Zhang**’**s handwritten lecture notes*

By citing the classics collected from professional literature and news reports, Professor Weiping Zhang introduced Professor Chern's achievements that lie in many famous research results. For example, as one of the most important mathematical theorems in the 20th century, the Atiyah-Singer index theorem has the elements of Chern class. Others such as Calabi conjecture, Yau-Tian-Donaldson conjecture, and Fu-Yau's pioneering work on non-Kähler manifolds are inseparable from Chern class; the topological phase transition research that won the Nobel Prize in Physics in 2016 also borrowed from "Chern number". Many renowned scientists honor Professor Chern as their role model: Professor Atiyah has a photograph of Professor Chern in his own study; Professor Singer once said "To most of us Professor S. S. Chern is modern differential geometry"; Professor Chen-Ning Yang even compared Professor Chern to a "new bodhisattva" in the Great Buddha Hall on the celestial mountain of mathematics.

**Professor Chern'****s Contributi****on to Chinese Mathematics**

During the Republic of China (1912-1949), the most important papers of Professor Chern were published when he was at The National SouthWest Associated University, and in his affiliations there was always a Chinese University. In the three years at "Academia Sinica", he cultivated a wealth of young talent, among whom Professor Wen-tsün Wu was the most outstanding one.

After the founding of the People's Republic of China (PRC), Professor Chern returned home and put forward a series of suggestions for the development of Chinese mathematics:

First of all, he helped young mathematicians visit overseas, providing opportunities for Chinese mathematics to see the world. Secondly, he organized seven consecutive Symposium on Differential Geometry and Differential Equations in 1980-1986, which largely promoted the development of differential equations and differential geometry in China. During the symposiums, apart from well-known foreign mathematicians invited to offer courses, many excellent Chinese scholars also shone at the conference and later became the mainstay of Chinese mathematics. Thirdly, he created the Mathematics Summer Institute and started the "Shiing-Shen Chern Project" (for studying in the United States), most scholars who benefited from the project all returned to China to serve the country. Finally, and the one that is most associated with Nankai University (NKU), Professor Chern founded the Nankai Institute of Mathematics (currently the Chern Institute of Mathematics) with the support of Professor Guoding Hu. In August, 1984, appointed by the Ministry of Education of PRC, Chern became the first director of Nankai Institute of Mathematics. During his term, in 1985-1995, activities of the 12 consecutive Special Academic Year held by the Institute had made far-reaching influences. In 1988, at the Conference on Prospect of Chinese Mathematics in the 21st Century, the "Shiing-Shen Chern conjecture" was first proposed which assumed that China would become a leading math nation in the 21st century. Professor Chern also helped on getting the Tianyuan Fund for Mathematics of NSFC, inviting the president of the People's Republic of China to present at the International Congress of Mathematicians 2002 which was held in China, and the establishment of the NKU Mathematics Special Class (Chern class) upon the approval of the Ministry of education of PRC in 1985, etc.

**Prospect of Chinese Mathematics**

*Words from Professor Chern**’**s speech, originally recorded in Chinese Journal of Nature, Volume 4, Issue 1, 1981*

For honoring Professor Shiing-Shen Chern's great achievements, in 2005, Nankai Institute of Mathematics was renamed Chern Institute of Mathematics. Comrade Jiang Zemin inscribed the name of the Institute (see the picture below).

*Nankai Institute of Mathematics renamed as Chern Institute of Mathematics upon approval*

*The full view of Shiing-Shen Building*

A man of sincerity attracts admiration. Professor Chern had made an indelible contribution to the development of mathematics at NKU and in China. It should be the best consolation for him to see Chinese mathematics flourishing.

*Professor Weiping Zhang**’**s lecture notes*

Professor Weiping Zhang expressed his hope to all the young students, that only by laying a solid foundation and making continuous efforts can we reconcile different fields and then come up with new ideas.

**I****nteraction**** ****After the Lecture**

"It's a great honour for me to be here and listen to Professor Zhang's lecture. The lecture is full of scientific knowledge as well as humor and fun that impressed me from the beginning to the end. I learned a lot about Professor Chern's contribution to differential geometry and the development of Chinese mathematical education and research. Professor Zhang also introduced some of Professor Chern's daily life which also can show a lot of his good qualities. As college students, we shall follow the example set by Professor Chern, study hard and work hard in each of our own field for making contribution to our country." said Jiacheng Li, an undergraduate student of mathematics and applied mathematics from School of Mathematical Sciences of NKU.

"Professor Chern has always been a leading authority in world mathematical circles, and he's always my role model. Today by listening to Professor Weiping Zhang's lecture, I'm totally impressed by Professor Chern's sincere love towards Nankai's mathematics as well as his devotion to seeking welfare for the masses. For us, his virtue and academic achievements are always admirable and worth learning." said Peixuan Li, a master student of computational mathematics from School of Mathematical Sciences of NKU.

"Professor Weiping Zhang's lecture is very impressive. He introduced Professor Chern's great contribution to modern geometry, especially "Chern class" which has had extensive and profound influences to mathematics. Professor Chern said that for making China a leading math nation he would give his all till his heart ceased to beat, and he never break his promise. Nowadays, as a younger generation of scholars, we need to follow Professor Chern's steps and spare no effort to fulfill his dream." said Yuanchang Lin, a doctoral student from Chern Institute of Mathematics of NKU.

"By listening to Professor Weiping Zhang's lecture, now I know more clearly about Professor Chern's work and its significance. Professor Chern once said that research on mathematics needs repetition, so that we can take the best of it and then come up with new ideas. Now I have realised that repetition must be an essential step in making progress on mathematics learning." said Rui Tian, a doctoral student from Chern Institute of Mathematics of NKU.

"Professor Weiping Zhang took us on a journey of reviewing Professor Chern's academic achievements. Professor Chern cultivated many excellent scholars, helped young mathematicians visit overseas, founded the Nankai Institute of Mathematics, and kept teaching students in his later years. His attitude towards life and scientific research is very thought-provoking and makes me think about where the value of life should lie in. His passion and support for mathematics also have been inspiring us to keep going forward and making contribution to the development of mathematics." said Yihan Ji, a master student from Chern Institute of Mathematics of NKU.

**Bonus Stories**

*A photo used by the Chinese liquor giant Moutai for advertising. The **“**honoured guest**”** *mentioned in the words below refers to Professor Shiing-Shen Chern

After returning back to China, Professor Chern had been received by Chinese leaders for many times. In 1986, Comrade Deng Xiaoping invited Professor Chern and his wife Shih-Ning Cheng for lunch. It was this meeting that brought about the measures of raising salaries of Chinese intellectuals and providing the special government allowances of the State Council.

*Louis Nirenberg** visiting Nankai University*

Professor Louis Nirenberg was a Abel Prize laureate and the first recipient of the Chern Medal. He mentioned that the experience of eating with Professor Chern at a Chinese restaurant was unforgettable, but he could never feel the same when he later eating there alone. Professor Weiping Zhang also recalled that once he came across Professor Chern at a Chinese restaurant in America. Professor Chern agreed with his order and said to him, "About math, I don't know how much you can learn from me; but about food, I'm pretty sure that you have a lot to learn." With the look of self-satisfaction, it seemed that Professor Chern was really enjoying being a gourmet.