In Memoriam: Zdenek Vorel, 86

Zdenek Vorel, professor of mathematics, has died. He was 86.

Vorel died on March 3 in Motol University Hospital in Prague, Czech Republic, after a six month battle with cancer.

Vorel’s research focus lay in mathematical theory of electric circuits, nonlinear ordinary differential equations, control theory, differential equations in Banach spaces, functional differential equations and continuous dependence of fixed points of nonlinear operations.

“Zdenek Vorel was a longtime member of the USC Dornsife Department of Mathematics,” said Francis Bonahon, professor of mathematics. “He specialized in the area of differential equations, in which he published 31 research articles. He was an excellent colleague, with a particularly gentle personality.”

Gary Rosen, professor of mathematics, agreed.

“Professor Vorel was a fine colleague, dedicated teacher and a gentleman,” he said. “He had an old-world European demeanor and charm about him and a true love of his homeland, the Czech Republic, and especially the city of Prague.” 

Vorel began teaching at USC Dornsife in 1969 as a visiting associate professor of mathematics. He joined the faculty full time in 1972, and was promoted to professor of mathematics in 1985. 

“My first impression of Zdenek was of a very polite and accommodating man,” said Professor of Mathematics Robert Sacker, who knew Vorel for 48 years. “He will be remembered as a true old-world gentleman, polite and charming and always there when needed. He will be missed by many.”

Vorel was a member of the U.S. organizing committee for the Mexican Symposium on Differential Equations from 1974–76 and was chair of USC’s foreign language exam committee from 1976–2011. Vorel also chaired USC’s mathematical colloquium from 1978–86 and served as the undergraduate vice chairman from 1989–92.

He retired in 2014.

His daughter, Veronika Vorel, said her father valued learning and the development of knowledge above all else.

“He believed in intellectual rigor and was not moved by emotional arguments, preferring to set aside a popular opinion in favor of finding the true heart of the matter — be it in a formal discussion about international politics or a dinner-table chat about the development of a piece of urban infrastructure,” she said.

“USC gave him a professional home wherein he could share and grow his work in mathematics, which he found to be a beautiful and challenging language. I remember how fondly he spoke of teaching the history of mathematics, his very favorite topic, and how grateful he felt to be able to pursue that passion to the end of his tenure at the university.”   

Born in what is now the Czech Republic, Vorel was also an accomplished linguist and was proficient in seven languages.

Zdenek Vorel was born in Kostelec nad ÄŒernými Lesy on the outskirts of Prague, in what was then Czechoslovakia, on April 27, 1929. His father headed a local hospital as chief administrator, later becoming an official at the National State Insurance Agency. Vorel was educated first at the Classical Gymnasium, where he was highly successful in his studies of Latin and Greek, and then at the British Grammar School in Prague. He attended the city’s Technical University before earning his doctorate in mathematics from Prague’s Czechoslovak Academy of Sciences in 1958. His thesis was “Error Estimates in the Theory of Generalized Differential Equations.”

From 1955–65, Vorel was a researcher at the Mathematical Institute of Czechoslovak Institute of Sciences. He held visiting positions at several academic institutions: the Centro de Investigación in Mexico City (1963–66); Rose Polytechnical Institute in Terre Haute, Ind.; National Autonomous University of Mexico in Mexico City (1967–68); and Clark University in Worcester, Mass. (1968–69).

From 1969–81, he returned to Mexico City each summer at the invitation of the Department of Mathematics of the Centro de Investigación and National Autonomous University where he directed seminars and Ph.D. theses.

Proficient in seven languages (English, Czech, Spanish, German, Russian, French and Italian), his articles on mathematics were published in Russian, Czech, English and Spanish. Vorel lectured at international conferences in diverse places: Moscow, Russia; Stockholm, Sweden; Trieste, Italy; Warsaw, Poland; Mexico; Arlington, Texas; and Los Angeles.

Sacker remembers Vorel’s intelligence and kindness.

“I became interested in generalized differential equations and went to him for help,” he said. “Zdenek very patiently gave me a beautiful lecture on the subject that impressed me tremendously.”

Sacker also recalls learning of Vorel’s ingenuity while a young man living behind the Iron Curtain in Soviet-controlled Czechoslovakia.

“After I returned from visiting Czechoslovakia in 1973 and realized how difficult it was to travel to and from that country, I asked him how he got out,” Sacker said. “He informed me he was a runner and would leave through some little known checkpoint where there were only a few border guards. Zdenek would obtain six or eight watches on the black market and wear them on his arm and bribe his way through like that. In the ensuing years he would come and go several times that way.”

Vorel published more than 33 papers in 18 journals, including the Journal of Integral Equations and the Boletín De La Sociedad Matemática Mexicana.

A keen mountain climber, Vorel enjoyed international travel and the beauty of nature. In addition to his passion for languages, he also loved classical music and was a voracious reader of biographies and history. He had a profound appreciation for National Geographic and The Economist.

He is survived by his daughter, Veronika Vorel.

He was cremated in Prague on March 9, 2016.