A daughter, Yael Meyer, said his weakened heart had resulted from chemotherapy for prostate cancer.
Israel National News reported that Dr. Ehrenpreis was "an eminent scholar of Talmudic texts who received rabbinical ordination from the greatest [authority] of Jewish law in the post-Holocaust period, Rabbi Moshe Feinstein."
And he shared, with Bernard Malgrange of France, authorship of the Malgrange-Ehrenpreis theorem, which might be more puzzling for a layman to understand than it was for the two, working independently in their two countries, to solve.
The theorem "states that for a certain very large category of partial differential equations, there is a solution," said Temple mathematics professor Marvin Knopp, a close friend. ..But the solution requires more math than the Phillies' won-lost record.
"Without an understanding of the theory of partial differential equations," Knopp said, "our modern technological society would not be possible."
"This is a very, very big deal," he added, and Mr. Ehrenpreis solved it in his early 20s. "He was an enormous international figure in the mathematics community. He was invited everywhere."
Knopp first met Dr. Ehrenpreis when they were doing summer work at the Hebrew University of Jerusalem. Dr. Ehrenpreis was also a visiting professor at the University of Paris and at Kyoto University in Japan. Year after year he commuted daily between Brooklyn and Temple, his daughter said. "Most of the years, he taught two days a week," Meyer said. "In recent years, in certain semesters, he taught three or four days a week."
Even this year, when he turned 80 in May, he took the Q subway to Manhattan and then an Amtrak train to Philadelphia, she said.
"He always said a train is a good place to get work done."
