Obituary: Ellis Cumberbatch

Ellis Cumberbatch, a pioneer in industrial mathematics and architect of the applied mathematics community at the Claremont Colleges, passed away on September 5, 2021, at the age of 87.

Ellis was born on April 19, 1934, to a working-class family in northern England. His father, Richard, only attended school until age 12. His mother, Isabella, also began to work in her teenage years, both in Manchester’s cotton mills and as a maid and cook in Cheshire. When Ellis was young, his parents had a small chicken farm in the hills surrounding Oldham that Isabella tended during the day while Richard worked in a factory. Once grain became unavailable during World War II, they left their farm and bought a small shop in Oldham. Around this time, Ellis began to show great promise as a student and performed very well on his O levels at age 11. His family then moved to Blackpool, where he was accepted to the prestigious Baines School. After Baines, Ellis went on to Manchester University.

At Manchester University, Ellis received his B.S. in mathematics in 1955 and his Ph.D. in applied mathematics in 1958 — the latter was under the direction of the renowned Sir James Lighthill, Fellow of the Royal Society. His dissertation foretold the design of an ocean-going ship hull that would allow the ship to travel more than 230 miles per hour. After earning his doctorate, Ellis spent two years at the California Institute of Technology—where he worked with Theodore Wu and Milton Plesset—and one year at New York University’s Courant Institute of Mathematical Sciences—where he worked with Harold Grad—before returning to England as a lecturer in mathematics at Leeds University. In 1964, he moved back to the U.S. to accept a position as an associate professor of mathematics at Purdue University; he was promoted to full professor in 1968 at the age of 34. After spending a sabbatical at the Claremont Colleges from 1977 to 1978 and learning about their math “clinics” (teams of students who work on industry projects), Ellis joined the mathematics department at Claremont Graduate University (CGU) in 1981. He directly supervised over a dozen doctoral students at Purdue and CGU.

The subjects of Ellis’ mathematical contributions ranged from differential equations and fluid mechanics to semiconductors and industrial modeling. While his initial publications focused on problems in fluid dynamics—including hydrofoils, cavitation, nonlinear water waves, and magnetohydrodynamics—he gradually broadened his focus to areas that included elasticity and vibrations as well as semiconductors and field effect transistors. Meanwhile, Ellis and his students made important contributions to understanding and modeling the current-voltage relation in transistors — anticipating quantum effects that are now becoming important with the reduction of transistor sizes.

Ellis was active in the SIAM community, having previously served on the Education Committee, working group for graduate modeling contests, and the Editorial Boards of SIAM News and SIAM Review. He took pride in the fact that, for some years, CGU was the only university where two students (Weifu Fang and Kaiqi Xiong) won SIAM awards for their Ph.D. dissertations. He also initiated the Southern California Applied Mathematics Symposium — a series of one-day meetings that rotate among universities in Southern California, which SIAM often supports as part of its regional activities. 

Ellis was a particularly strong advocate for the “I” in SIAM. He organized the SIAM Conference on University-Industry Collaborations in Mathematical Sciences with Stavros Busenberg in 1987, as well as subsequent workshops in 1999 and 2009. Ellis also co-wrote a book with his friend Alistair Fitt called Mathematical Modeling: Case Studies from Industry, which was published by Cambridge University Press in 2001. He traveled the globe for international industrial math study groups, during which he recruited colleagues and students to share the excitement of working intensively with a team of mathematicians to solve industrial math problems wherein, as he put it, “the flimsiest idea can get taken quite a distance.” One example in Turkey involved improving the accuracy of handguns. Upon seeing sugar cubes at a coffee break, Ellis had the ingenious thought of lining them up along the top of the gun’s barrel. When the gun was fired, the cube that jumped the highest marked the point where elastic distortion maximally compromised the bullet’s trajectory.

Throughout his life, Ellis was a keen sportsman and a passionate fan of soccer. He played soccer at Purdue with a team of professors and graduate students called the “Ethnics.” He always enjoyed watching Manchester United but was not partial to any one team; he was simply a fan of the best abilities and good sportsmanship. When his children’s high school lacked a soccer team, he simultaneously became the soccer coach, chauffeur to games, and grass-cutter and line-drawer for the fields — anything to make the games happen! In addition, he was an avid swimmer and trained lifeguard who once rescued a fellow participant at an industrial mathematics workshop in Venezuela.

Ellis had a monumental impact on the mathematical sciences at the Claremont Colleges. He revitalized CGU’s mathematics programs with colleague Jerry Spanier, serving as department chair for years and building an applied focus that thrives to this day. He was also instrumental in establishing the Ph.D. in engineering and computational mathematics (jointly with California State University, Long Beach) and the Financial Engineering program (jointly with CGU’s Drucker School of Management). Ellis was responsible for so many of the intangibles as well. His former Ph.D. student Jose Macias once commented that “His dry British wit with the light touch of cynicism is always a welcome stress reliever in the classroom.” Ellis regularly took new faculty under his wing and helped them understand the workings of the Claremont Colleges. He generously dispensed wisdom that was concise, direct, and invaluable. When one of us was interviewing at CGU and inquired about how to dress for the interview, Ellis advised that “If you wear a tie, you will immediately be regarded as pretentious!”

Ellis was legendary for bringing people together. He was the driving force behind the creation of the Claremont Center for Mathematical Sciences, which unites the faculty from all six math departments at Claremont in research and teaching collaborations. He was also passionate about outreach activities like the Gateway to Exploring Mathematical Sciences program, which brings middle and high school students to campus for lectures and hands-on activities to excite them about mathematics.

After his retirement in 2009, Ellis remained instrumental in department affairs and even served as dean of mathematical sciences from 2011 to 2012. He enjoyed the iconic Elton John line, “If you’re made in England, you’re built to last.” Until the start of the COVID-19 pandemic, Ellis was the faculty member who could most reliably be found in his office — except at 3 p.m., when he could reliably be found preparing tea in the department kitchen. He served on numerous Ph.D. committees until well into his 80s, including an epic case of a student whose dissertation took so long to complete that all committee members were retired by the time of the defense — and the Ph.D. candidate was too.

Ellis is survived by his long-term partner, Suzanna Stafford, and three children from his first marriage: Guy, Louis, and Evelyn Cumberbatch; his daughter Ellen is deceased. He is also survived by his sister, Pamela Dagger, and his grandchildren: Adam and Christopher Cumberbatch and Boaz and Lily Kaffman. Suzanna’s daughter, Jeni Hess Brage, and grandchildren Shelby and Cassidy Brage were close to him as well. 

We will greatly miss Ellis’ wise advice, northern English candor, and steadfast insistence that “we all work together and we all get along.”

This piece was prepared by members of Claremont Graduate University’s Institute of Mathematical Sciences and the family of Ellis Cumberbatch.