Wen-Bin Zhang died in Evanston, Illinois, on February 22, 2022, following surgery. Zhang held academic appointments at several institutions in the western hemisphere and China, including an adjunct position in the Department of Mathematics at Illinois. Before his death, he and his wife, Kun-Ming Luo, lived in Chicago and made frequent trips to visit their daughter, Denise, and grandchildren in the Boston suburbs.
Zhang was born in Hong Kong, China, in 1940. He earned a diploma, equivalent to a Master of Science in Mathematics, from Peking (today Beijing) University in China. Upon graduating, he taught at the Tianjin Norma University and the South China University of Technology before coming to the University of Illinois in Fall 1982 for graduate study. He earned his Ph.D. at Illinois in 1986 under Professor Harold Diamond with a thesis on analytic number theory. He and Diamond later wrote a monograph on the theme of his thesis.
Zhang was a very successful teacher as an assistant in the Department of Mathematics at Illinois, and students flocked to his classes in spite of his having a heavy accent. He wrote complete details neatly on the board, held extensive office hours, and showed his great commitment to students' learning---indeed, he ended each semester with more students than were originally enrolled. After a brief postdoctoral stint in the United States, Zhang returned to the South China University of Technology to teach and research full time and was promoted to full professor in 1988.
In 1989, the Department of Mathematics organized a conference at Allerton Park in honor of Paul Bateman, and we invited Zhang. His attendance had both personal and mathematical consequences: While he was here, the Tiananmen Square Massacre occurred, and the United States allowed any Chinese in the country at that time to apply for citizenship. Zhang did this promptly, and in due course became a citizen.
After the conference, a proceedings volume was organized, and Zhang was asked to referee an article on an analogue of the prime number theorem for additive arithmetical semigroups. He reported that the piece had a fundamental error. It turned out that, over a couple of decades, everyone writing on the subject (including distinguished people!) had assumed that the relevant generating function had no zero at the point -1, and Zhang had produced an example in which this occurred. We rejected the first paper, and accepted in its place one that Zhang wrote. This work led to an invitation to write the bible on this topic, with John Knopfmacher.
After holding visiting appointments at Ilinois and the University of Texas at Austin, Zhang joined the University of the West Indies, in Kingston, Jamaica, and was subsequently promoted to professor there as well. During his long career he collaborated with colleagues at renowned institutions in Asia, Europe, and South Africa. He loved the UIUC Math Library, which led to his being one of the few people who, every Christmas, traveled from Jamaica to Urbana. He retired from UWI in 2010 and enjoyed continuing to work on mathematics, particularly trying to prove the Riemann hypothesis.
Denise Zhang wrote Diamond about his last day:
My father was still thinking about the Riemann conjecture from the hospital bed the day before he passed away. We were visiting him that day and he told us that he had some new ideas. He seemed excited that it might be a breakthrough. You know how he would be if he thought he had a new lead. He had this smirk, this twinkle in his eyes, this hopefulness in his tone ... My mom asked him to write it down in a notebook so he wouldn't forget but he assured us it was all in his head. I have not met anyone more passionate and dedicated about math than he.
--Harold Diamond