**Lecturer: You Jiangong**

**Abstract:**

Mathematics is a science focusing on the relationship between spatial form and quantity. "Same or different" and "more or less" are naturally two basic problems in Mathematics. The lecture mainly discusses the problems of "more and less" and "big and small". The concept of "more and less" is relatively clear in finite sets, but fuzzy in infinite sets. In infinite sets, the sense in which the concept is talked about shall be confirmed, and the concept may refer to "more" in one sense but "less" in another sense sometimes (both conditions are reasonable).

**Introduction to the Lecturer:**

You Jiangong received a doctorate from Peking University in 1989 and is now a professor at Chern Institute of Mathematics, Nankai University. He has been committed to developing mathematical theories and methods for dealing with small divisor resonance for a long time. He has made a series of achievements in the undisturbed reducibility theory of quasi-periodic linear system, spectral theory of pseudo-periodic Schrodinger operator, regularity of Liapunov exponent, KAM theory and its application in differential equations, and issued more than 60 papers in international famous academic journals such as*Invent. Math.*,*Duke Math. J*,*GAFA*and*PRL*. He has won the first prize of Natural Science Award of the Ministry of Education, the second prize of National Natural Science Award, and the Outstanding Youth Scholar, by Hongkong Qiushi Scientific and Technological Foundation. He was supported by the National Science Fund for Distinguished Young Scholars. In addition, he was invited to give a 45 minute academic report at the 2018 International Congress of Mathematicians.

**Invitee:**

Hu Xijun, Professor from School of Mathematics

**Time:**

14:15-15:15, November 25 (Thursday)

**Venue:**

Academic Hall #924, Block B, Zhixin Building, Central Campus

**Hosted by School of Mathematics, Shandong University**