The upcoming Winston Ko Professorship in Science Leadership Lecture will explore the work of a medieval Italian mathematician and its lasting impacts on number theory.

Kenneth A. Ribet, a professor emeritus of mathematics at UC Berkeley, will present “Fibonacci, congruent numbers and elliptic curves” on Thursday, May 16 at 6 p.m. at Putah Creek Lodge. The event is free. 

“The perfect squares (1, 4, 25, 36 and so forth) were studied extensively by Leonardo Fibonacci in his thirteenth-century publication "The Book of Squares," said Ribet, who specializes in number theory and algebraic geometry. “Fibonacci studied triples of squares such as 1, 25, 49 for which the middle number is the average of the other two. Notice that 24, the difference between 1 and 25, is the same as the difference between 25 and 49.”

According to Ribet, Fibonacci used the word “congruum” to describe such numbers.

“Deciding whether or not a given number is a congruum remains an open problem,” he added. “This problem is illuminated by conjectures in number theory that have been central for the last 60 years. I will describe the conjectures and explain their relation with Fibonacci's work.” 

An esteemed mathematician, Ribet is a member of both the American Academy of Arts and Sciences and the U.S. National Academy of Sciences. He is also the recipient of the Fermat Prize and the Royal Dutch Mathematical Society’s Brouwer Medal, among other honors and awards. 

“I heard a version of Professor Ribet’s number theory talk in Berkeley last year and it was quite fabulous, entertaining and accessible,” said Distinguished Professor of Chemistry R. David Britt, who is also the Winston Ko Chair.

The Ko Professorship in Science Leadership was endowed by the late Professor Emeritus Winston Ko and his wife Katy Ko. The endowment honors Ko’s 41 years of service to UC Davis and his leadership in research and education. Ko served as chair of the Department of Physics from 1998 to 2003 and dean of the Division of Mathematical and Physical Sciences (MPS) from 2003 to 2013. MPS was one of three separate divisions that eventually united to form the College of Letters and Science. 

Register to attend the Winston Ko Professorship in Science Leadership Lecture.