PREFACE

This special issue of Acta Mathematica Scientia is dedicated to the memory of Professor Jia-Rong Yu on the occasion of his hundredth anniversary.

Professor Jia-Rong Yu, born November 16, 1920, passed away on October 14, 2020, at the age of one hundred. He is known as the founder of the Sino-French Mathematical Center in Wuhan University,and was the director of this center from 1980 to 1994. In 1991,thanks to his colossal investment in Franco-Chinese cooperation,he was made officer in the order of academic palms by the French Government.

Professor Jia-Rong Yu’s mathematical works were influenced by Georges Valiron and Szolem Mandelbrojt. His French state doctoral thesis, entitled “Sur les droites de Borel de certaines fonctions enti´eres”, was completed under the supervision of Georges Valiron and defended in 1950. The thesis was published in the following year (1951) in Annales de l’´Ecole Normale Sup´erieure, after which he then joined Wuhan University as professor in the same year.

Professor Jia-Rong Yu was an internationally renowned expert on Dirichlet series and random Dirichlet series. His scientific works had impacted the development of his domain and were greatly appreciated by his peers, including Jean-Pierre Kahane, Paul Malliavin and Szolem Mandelbrojt. Jean-Pierre Kahane even said: “I have devoted a whole book to random series of functions, but Jia-Rong Yu preceded me in the application of this subject to Dirichlet series”.

Despite the absence of research structures in China for a lengthy period lasting until the 1970s, Professor Jia-Rong Yu succeeded in pursuing his research and began publishing again in 1976. At that time, he studied the uniqueness theorem of Szolem Mandelbrojt, Norbert Wiener and Paul Malliavin for analytical functions of several variables. He applied his results to moment problems, including the Stieltjes-Hamburger moment problem, the approximation problem,and the quasi-analyticity. In spite of the heavy administrative burden that came with his role as the director of the Sino-French Mathematical Center, the time he devoted to his students and time required for the extreme care he brought to his teaching,he always practiced mathematics. Even as a retiree he continued to do research, evidenced by an article published in Acta Mathematica Scientia in 2012. This last publication also witnesses Professor Jia-Rong Yu’s consistent support to our journal.

When China reopened to the world in the late 1970s,Professor Jia-Rong Yu recalled friendships he made during his studies in France. He therefore naturally contacted his French friends such as Jean-Pierre Kahane and Paul Malliavin. He visited Orsay University in 1979 to develop a cooperation project. Indeed, many things needed to be built and Chinese universities needed help. This project culminated with the visit to China of the French President Giscard d’Estaing. A Sino-French center was established at Wuhan University. He was the director and under his leadership this center flourished. For a little over ten years, each year, students who followed courses taught in French in Wuhan, were selected to continue their studies in France.The results are impressive. More than seventy theses in mathematics have been defended.About half of them returned to China, thus irrigating the best Chinese universities with young talent. Other countries, notably France, have also benefited: a number of professors in French universities come from of this operation.

Professor Jia-Rong Yu has earned the respect,esteem and the admiration of his peers,of his students, of all those who frequented him, not only because of his qualities as an organizer and his scientific works, but also because of the mixture of cultures that he embodied: an oriental culture of humility and politeness combined with a western culture of elegance and franchise. In the sense of Taoism,the supreme goodness acts like water,seeking to make good for everything without benefiting from it.

Professor Jia-Rong Yu is a symbol of a Chinese mathematical era. He was a man of conviction and action, a caring person, a beloved sage.

Standing Editors: Shaoji FENG Caiheng OUYANG Quanhua XU

Lixin YAN Xiangyu ZHOU

Shaoji FENG, fsj@amss.ac.cn

Caiheng OUYANG, ouyang@wipm.ac.cn

Quanhuo XU, qxu@univ-fcomte.fr

Lixin YAN, mcsylx@mail.sysu.edu.cn

Xiangyu ZHOU, xyahou@math.ac.cn