By Prof. Ehud de-Shalit (Hebrew University) and Prof. Yehuda Pinchover (Technion) 

 

On the 21st of Adar, 5785 (March 21, 2025), Professor Shmuel Agmon passed away. He was the eldest member of the Israel Academy of Sciences and Humanities, one of the founding faculty members of the Einstein Institute of Mathematics at the Hebrew University, and among the world’s leading researchers in the field of partial differential equations.

Shmuel Agmon was born on February 2, 1922, in Tel Aviv, to the writer and Zionist activist Natan Bistritzky and his wife Chaya (née Guttman). The family moved from Nazareth—where Chaya had worked as a dentist—to Jerusalem, where Shmuel completed his studies at the Hebrew Gymnasium. Although he was drawn to mathematics from a young age, he also found time for chess (he was the Jerusalem youth champion) and was a member of the “Machanot HaOlim” youth movement. In 1939, he went for training at Kibbutz Na’an, but within a year returned to academic studies at the Hebrew University. His studies were interrupted by World War II, during which he volunteered for four years in the Jewish Brigade. After being discharged, he completed his studies at the Hebrew University and was invited by Professor Sholem Mandelbrojt to pursue his doctorate at the Sorbonne in Paris.

He completed his PhD in 1949 in the field of complex functions and then took a position at Rice University in Texas. At Rice, he transitioned into the field of partial differential equations, which would define his career. His encounters with leading analysts Peter Lax and Louis Nirenberg—especially his collaboration and friendship with the latter—deeply influenced him and shaped his professional path.

In 1952, he joined the Hebrew University, pioneering the field of partial differential equations in Israel and mentoring many students. In 1964, he was elected to the Israel Academy of Sciences and Humanities.

His research focused on the qualitative theory of linear elliptic differential equations. His groundbreaking and highly influential papers with Douglas and Nirenberg, published in 1959 and 1964, generalized the classical Schauder theory on regularity of second-order elliptic boundary value problems to higher-order elliptic equations and even to systems of such equations. These works, among the most cited in mathematical analysis, continue to influence the modern theory of linear and nonlinear elliptic equations.

From the mid-1960s, Agmon worked on the spectral theory and scattering theory of Schrödinger-type equations, publishing results of great significance in mathematical physics. In particular, he obtained precise estimates on the decay of eigenfunctions of the Schrödinger equation in terms of a metric he defined—now known as the Agmon metric. His work advanced the understanding of wavefunction scattering for both short-range and long-range potentials.

For his work, he was awarded the Weizmann Prize, the Rothschild Prize, the Israel Prize, and the EMET Prize. His 1965 book on boundary value problems for elliptic differential equations became a foundational text in the field.

Agmon was widely respected worldwide and known among his colleagues for his broad intellectual horizons, phenomenal memory, modesty, and sense of humor. In 1947, he married Galia Yardeni, who sadly passed away in 1968. In 1972, he married Nechama de Shalit.

Shmuel Agmon witnessed momentous events throughout his life and was blessed with longevity and good health. At the age of 102, he gave an interview to the Israel Academy of Sciences, which can be viewed here: https://www.youtube.com/watch?v=hlYQStrcM2g&t=4s

May his memory be a blessing.