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Joseph John Kohn, professor of arithmetic, emeritus, a 1956 Ph.D. alumnus and a frontrunner within the area of a number of complicated variables, died on Sept. 13. He was 91.
Born in Prague in Could 1932, Kohn emigrated to Ecuador in 1939 earlier than transferring to New York Metropolis in 1945. After graduating from Brooklyn Technical Excessive Faculty and the Massachusetts Institute of Know-how, Kohn got here to Princeton in 1954 for graduate faculty, then joined Princeton’s college as an teacher for one yr. He was a professor at Brandeis College for practically a decade, then returned to Princeton as a full professor in 1968. He taught at Princeton for 40 years, with a number of years away as visiting college across the globe. He held the Henry Burchard Tremendous analysis chair from 2002 to 2003, and he transferred to emeritus standing in 2008.
“Joe was among the many most pleasant, widespread and influential mathematicians of his era,” stated John D’Angelo, a 1976 Ph.D. graduate and an emeritus math professor on the College of Illinois Urbana-Champaign. “His mathematical legacy is gigantic. I talked with Joe many instances within the final six months. He remained engaged with arithmetic till the tip.”
Charles Fefferman, Princeton’s Herbert E. Jones, Jr. ’43 College Professor of Arithmetic, labored with Kohn for many years, together with collaborating on a number of papers.
“Joe was very influential and authentic,” Fefferman stated. “He was very centered on a really, very basic downside in arithmetic. He and his grad college students — whom he mentored and nurtured very properly — made nice progress. The concepts that they got here up with have been used not solely on that downside and associated issues, but additionally on seemingly utterly unrelated topics.”
Kohn additionally spoke many languages fluently, which served him properly on the many establishments and conferences he visited all through his profession. He was a visiting professor at Harvard College, the College of Mexico, the College of Buenos Aires, the College of Florence, the Institut des Hautes Études Scientifiques in Paris, and the Charles College in Prague. He was additionally a visiting scholar at the Institute for Superior Research 4 instances over his profession, as a postdoctoral researcher in 1957-58 and 1961-62, then throughout his 1976-77 and 1988-89 sabbatical years.
Along with his accomplishments in arithmetic, Kohn was a standout division chair, first at Brandeis (1963 to 1966) after which throughout a number of phrases at Princeton, the place he advocated most successfully for bringing in nice mathematicians and receiving elevated funding for the division, in addition to being an advisor to colleagues and college students alike. Kohn led the maths division from 1973 to 1976 and from 1993 to 1996, plus he served as appearing chair in spring 2002.
“He was a particularly efficient chairman,” stated Fefferman. “Many of the senior college take one flip as chair, nevertheless it’s uncommon to do multiple. I believe folks acknowledged that Joe had a really nice expertise for this. …. It’s truthful to say that Princeton has the most effective math program within the nation. Not ‘among the finest,’ the finest. Joe introduced in very, very sturdy folks. This sounds self-serving — he introduced me in — however apart from me, he did magnificent hiring. He introduced in Invoice Thurston, who was one of many nice mathematicians of the century. He additionally performed a job in retaining hires. He was simply excellent in all points of that.”
Ngaiming Mok, who’s now the Edmund and Peggy Tse Professor in Arithmetic on the College of Hong Kong, was on the Princeton college with Kohn from 1980 to 1985.
“Apart from being impressed by his great management within the area of a number of complicated variables, I’ve a lot benefited from Joe Kohn’s openness and friendliness to junior researchers of various cultural backgrounds. This made me really feel far more at house throughout my years in Princeton,” he stated. “We’ve misplaced an elder statesman of our area and an expensive friend.”
Kohn’s groundbreaking work dominated his area for greater than half a century. He mentored 16 Ph.D. college students, plus postdoctoral students and junior college members. Many recalled what a big function he performed of their lives and careers.
“He was a really nice mathematician whose contributions drastically modified the panorama of the sector,” stated Yum-Tong Siu, a 1966 Ph.D. graduate who’s now the William Elwood Byerly Professor of Arithmetic at Harvard College. “Within the final 5 many years, his work has been taking part in such an indispensable function within the analysis of an entire era of mathematicians in his area. To youthful researchers, he was most inspiring, supportive and beneficiant. He was all the time the particular person to show to for recommendation mathematically, professionally and personally. We are going to all sorely miss him.”
“Joe Kohn was an enormous within the area of research of a number of complicated variables,” stated Andreea Nicoara, a 2002 Ph.D. pupil of Kohn’s who’s now the Accenture Affiliate Professor in Arithmetic on the College of Dublin. “For the Princeton math division, he was a vital determine not simply professionally however socially. Joe had a really sharp wit and heat persona. He all the time attended tea, so even graduate college students working in numerous fields of math received to know him. He and his spouse Anna Rosa entertained quite a bit and have been very caring at any time when somebody wanted assist. My grandfather was killed whereas I used to be doing my Ph.D. at Princeton with Joe, and he and Anna Rosa helped me get via that tough time.”
She continued: “Sooner or later in my third yr, I confirmed up at my weekly assembly with Joe and advised him that I couldn’t get something performed as a result of I had sprained some fingers on my writing hand. Joe’s eyes twinkled, and he stated, ‘You sprained your hand, not your mind, proper?’ I then found that I didn’t want paper, so I did a lot of the work on my thesis strolling alongside the canal. Joe labored on this means as properly; he would stroll round slowly for some time after which come again and scribble a number of issues down. Though counterintuitive, it’s a higher means of doing arithmetic as a result of one sees the large image this manner and doesn’t get slowed down in particulars.”
Gerald Folland, a 1976 Ph.D. graduate, the creator of a number of math textbooks, and an emeritus professor on the College of Washington, stated, “I owe Joe Kohn quite a bit. I used to be his first Ph.D. pupil at Princeton, and the analysis downside he proposed was an ideal match for me. Then he took me on as a collaborator to jot down up his 1970-71 lectures and switch them right into a ebook, which launched me on one other necessary side of my profession.
“He wasn’t afraid to deal with laborious mathematical issues, and he had the endurance and persistence to maintain engaged on them till he received good outcomes. Joe’s mathematical work was nearly all in an space that lies on the intersection of complicated evaluation in a number of variables and partial differential equations. He was a number one world knowledgeable in that specialised space, and a few of the strategies he helped develop have a lot broader functions.”
“Assembly Joe was one of many luckiest issues in my life,” stated Charles Epstein, a former Princeton postdoctoral researcher who’s now a senior analysis scientist on the Flatiron Institute’s Middle for Computational Arithmetic and the Thomas A. Scott Professor Emeritus on the College of Pennsylvania.
“After I arrived in Princeton as a postdoc, I knew nothing by any means about a number of complicated variables, and was at a loss for what I ought to do,” Epstein stated. “Joe sensed that I used to be floundering and took it upon himself to assist me to get pleasure from my time at Princeton and discover a route for my work. He requested me to run the departmental colloquium and sometimes took me to lunch on the IAS or College Membership, throughout which era we mentioned arithmetic and a terrific many different issues. As a consequence of Joe’s kindness and the presence of a terrific group of postdocs working with Joe in severall complicated variables, I additionally ended up working on this area.”
Amongst his many honors, Kohn gained a Guggenheim Fellowship in 1976, the Leroy P. Steele Prize of the American Mathematical Society (AMS) in 1979, the Balzano Medal from the Czechoslovak Arithmetic and Physics Society in 1990, and the Stefan Bergman Prize for Influential Analysis from the AMS in 2004. He was elected to the American Academy of Arts and Sciences in 1966 and to the Nationwide Academy of Science in 1988.
He served as editor or on the editorial boards of Advances in Arithmetic, the Annals of Arithmetic, the Journal of Differential Geometry, and the Transactions of the American Mathematical Society. He served as a member of the Board of Trustees of the American Mathematical Society and the Board of the Mathematical Sciences of the Nationwide Academy of Science.
He was a member of the primary delegation of American scientists to go to China, in 1976, and he participated in scientific trade packages with the USSR (1965) and Czechoslovakia (1967 and 1977). When the College of Bologna celebrated its 900th anniversary, they awarded Kohn an honorary doctorate, calling him “one of the crucial eminent dwelling mathematicians.”
Kohn is survived by his spouse, Anna Rosa Di Capua, of Quito, Ecuador; their kids, Eduardo, Emma, and Alicia; daughter-in-law Lisa Stevenson; and grandchildren Benjamin and Milo. Donations in reminiscence of Joseph J. Kohn could be made to HIAS, the Nationwide Museum of Arithmetic, and the Jewish Middle of Princeton.
View or share feedback on a memorial web page supposed to honor Kohn’s life and legacy.
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