More than 300 coffee mugs once lined the shelves of Robert “Bob” Devaney’s office in the former Mathematics & Statistics Department on Cummington Avenue—souvenirs from lectures delivered around the world. The mugs were not trophies of travel so much as reminders of the people behind the journeys: the students, teachers, and colleagues he believed mathematics belonged to.

Devaney, professor emeritus of mathematics at Boston University and an internationally renowned leader in dynamical systems and chaos theory, died November 16, 2025, at his home in Charlestown, Massachusetts. He was 77. Throughout his career, he devoted his life to proving that “mathematics is a living, breathing subject”—and, through research, teaching, and outreach, to ensuring that others could see its beauty, accessibility, and joy.

A native of Methuen, Massachusetts, Devaney was born in nearby Lawrence and attended Central Catholic High School. He earned his bachelor’s degree from the College of the Holy Cross in 1969 and his Ph.D. from the University of California, Berkeley, in 1973, where he worked under Fields Medalist Stephen Smale. After appointments at Northwestern University and Tufts University, Devaney joined the faculty of Boston University in 1980. He served as department chair from 1983 to 1986, was named the College of Arts & Sciences’ inaugural Feld Family Professor of Teaching Excellence in 2010, and became professor emeritus in 2018.

Over the course of his career, Devaney made foundational contributions to the field of dynamical systems. He authored more than 125 papers and 16 books, including An Introduction to Chaotic Dynamical Systems, which introduced a clear and intuitive definition of chaos that became a widely accepted standard. At a moment when mathematicians were grappling with how to formalize an emerging concept, Devaney offered a definition that was both rigorous and accessible—an approach that reflected his broader philosophy of mathematics itself.

“Bob’s timing in 1985 was perfect,” said Professor Emeritus Paul Blanchard, who started at BU the same day as Devaney. “He decided to write an introductory textbook on discrete dynamical systems with as few prerequisites as possible while at the same time discussing many of the most modern aspects of the subject including chaotic systems. His goal was a text that is accessible to junior and senior math majors, as well as graduate students and scientists in other disciplines.”

Later, Devaney turned his attention to transcendental dynamics, revitalizing the study of rational families through singular perturbations, and laying the foundations for what is now a robust area of study. The fractal structures known as “Devaney hairs” stand as a testament to his legacy.

Yet even these achievements tell only part of his story. “Bob is one of the most inspirational people I’ve ever met,” said Tasso J. Kaper, professor and chair of the Department of Mathematics and Statistics. “He inspired young people—high school students, undergraduates, graduate students—by showing them that math is alive. It’s exciting. It’s fun to be part of.”

Kaper first met Devaney during a faculty interview in February 1992. Having used Devaney’s textbook as a graduate student, he began with an unexpected question: how to pronounce Devaney’s name. Bob replied instantly: “Devaney—rhymes with fanny.” It was classic Bob—disarmingly simple, gently self‑mocking, and entirely without pretense. “He was one of the deepest thinkers in his field,” Kaper said, “but he didn’t take himself too seriously. He just shared the enthusiasm and excitement of doing math.”

That blend of intellectual depth and clarity defined not only Devaney’s personality, but also his approach to mathematics. His graduate texts were known for their care and transparency, with proofs written out fully and arguments developed step by step. “He wrote exactly why the results are true—clear, transparent, constructive,” Kaper said. Whether addressing research mathematicians or fourth graders, Devaney brought the same conviction: mathematics was for everyone.

Devaney was deeply committed to rethinking how mathematics is taught. At Boston University, he co‑led an NSF‑funded effort to revitalize the sophomore‑level ordinary differential equations course, integrating ideas from dynamical systems into a class taken by thousands of students nationwide. That led to a long-awaited text book, Differential Equations, co-authored with Blanchard and Glen R. Hall, which has been printed in five editions. Late in his career, he returned to collaborate with Stephen Smale—his former advisor—and Morris Hirsch on a revised edition of their classic text, Differential Equations, Dynamical Systems, and an Introduction to Chaos, bringing decades of insight full circle.

He was an advocate for inclusion in mathematics, mentoring generations of students who went on to lead influential careers, including many women who became leaders in their fields. Drawing on his own upbringing in Lawrence, he offered encouragement that was both personal and sustained—rooted in the conviction that talent is universal, even when opportunity is not. “If I can do this, you can do this,” he would tell students.

That message resonated deeply with Núria Fagella, who came to Boston University for a master’s degree and completed her Ph.D. under Devaney’s supervision. She is now a professor at the Universitat de Barcelona and a principal investigator at the Centre de Recerca Matemàtica. “Bob’s encouragement made me believe, for the first time, that I could become a researcher in mathematics—something I had never imagined for myself,” Fagella said. “His support changed my life.”

His mentorship extended well beyond his own students. Jamil Siddiqui (ENG’93, Wheelock’94, GRS’98), an engineering major, first met Devaney as a sophomore through his federal work‑study job in the mathematics office. “You hear of Bob Devaney—he’s a world‑class mathematician,” Siddiqui said. “But I knew him as this goofy, down‑to‑earth guy who liked to hang out with students.”

When Devaney learned that Siddiqui was working long hours to afford college, he offered him a summer job assisting with teacher workshops—at $500 a week, far more than his work‑study position paid. Siddiqui’s duties included organizing materials and, memorably, picking up six dozen fresh bagels each morning. “Bob’s paying me $500 a week to get bagels,” he laughed. Yet those summers proved transformative. Surrounded by teachers from across Boston, Siddiqui discovered his calling and went on to become an award‑winning high school math teacher.

Over the years, Devaney continued to advocate for him—arranging funding for graduate study, bringing him on as a teaching assistant, and writing letters that opened doors. “Once he cared about you,” Siddiqui said, “you were in his group—and he would use his powers to help you succeed.”

Devaney’s commitment to outreach was tireless and far‑reaching. For more than two decades, he organized Boston University’s Math Field Days, drawing thousands of high school students and teachers to campus. He ran summer workshops for teachers, directed the NSF’s Dynamical Systems and Technology Project, developed computer programs and visual tools, and produced videos that made chaos and fractals tangible.

He delivered more than 1,600 invited lectures in all 50 states and more than 35 countries on six continents. He often joked that he was still waiting for Antarctica to complete the set. He also served as a chaos consultant for theatrical productions of Arcadia and as the mathematical consultant for the 2007 film Twenty One.

“He travelled a whole lot”, Blanchard added. “On his web page, he lists all of his invited lectures, and the net result is on average more than 40 talks per year for each of his 39 years at BU. That’s a lot of frequent flyer miles.”

One week he might lecture to leading mathematicians; the next, he would sit cross‑legged on a classroom floor explaining fractals to fourth graders, Siddiqui said. “There are professors who don’t have time for you unless you can help with their research,” he recalled. “Bob wanted to be a teacher. He wanted to get people excited.”

Devaney’s honors reflected both his scholarly impact and his devotion to teaching. He served as president of the Mathematical Association of America from 2013 to 2015, was named a Fellow of the American Mathematical Society, and received numerous awards, including the Deborah and Franklin Tepper Haimo Award for Distinguished University Teaching, the National Science Foundation Director’s Award for Distinguished Teaching Scholars, the Carnegie/CASE Massachusetts Professor of the Year Award, and Boston University’s Metcalf Award for Teaching Excellence. His appointment as the inaugural Feld Family Professor of Teaching Excellence recognized a career that proved there is no conflict between being a great scholar and a great teacher.

Despite these accolades, Devaney remained famously unpretentious. On his website, he once wrote: “This stuff is here only because I give so many talks… Please don’t waste your time reading all this crap.”

Outside mathematics, he embraced life with the same exuberance he brought to the classroom. He loved sailing aboard Cygnet with his wife, Kathy; attending opera performances; solving Sudoku; and traveling widely.

“He was a friendly family man, lots of fun at the BU Pub, generous,” said Mathematics Professor David Fried, whom Devaney recruited to BU. “He had a knack for finding tractable problems for his students, which made him a great thesis advisor. We all miss him.”

Devaney didn’t drink coffee—he preferred Earl Grey tea—but his mug collection ballooned as word spread about it, eventually finding a permanent home in his Boston University office. Upon retirement, he joked, “If anyone wants a mug, stop by.”

The shelves of his office may no longer be lined with mugs, but the stories behind them—the lives changed, the confidence sparked, the doors opened—remain. His legacy endures not only in the mathematics he advanced, but in the people he lifted, and in the joy he brought to learning itself.

He is survived by his wife, Kathleen Ferguson Devaney; his sons, Robert and Stephen; nine grandchildren; and many extended family members. He was predeceased by his daughter, Meaghan. In lieu of flowers, contributions may be made to the Robert L. Devaney Scholarship Fund at Central Catholic High School.