Lipót Fejér facts for kids
Quick facts for kids
Lipót Fejér
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Fejér c. 1928
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| Born | 9 February 1880 |
| Died | 15 October 1959 (aged 79) Budapest, Hungary
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| Nationality | Hungarian |
| Alma mater | University of Budapest |
| Known for | Fejér kernel Fejér quadrature Fejér's theorem Fejér–Riesz theorem |
| Scientific career | |
| Fields | Mathematics |
| Institutions | University of Budapest University of Berlin |
| Doctoral advisor | Hermann Schwarz |
| Doctoral students | Paul Erdős John von Neumann George Pólya Tibor Radó László Kalmár Marcel Riesz John Horvath Gábor Szegő Michael Fekete János Aczél Steven Gaal |
| Other notable students | Cornelius Lanczos |
Lipót Fejér (born Leopold Weisz; February 9, 1880 – October 15, 1959) was a very important Hungarian mathematician. He changed his name to Fejér around the year 1900. He is well-known for his significant work in a part of mathematics called harmonic analysis, especially with Fourier series. He also guided many students who later became famous mathematicians themselves.
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Lipót Fejér's Early Life and Education
Lipót Fejér was born in Pécs, which was part of Austria-Hungary at the time. His family was Jewish. His father, Samuel Weiss, ran a shop. When he was young, Lipót didn't do very well in primary school. For a while, his father even taught him at home.
However, in high school, Lipót discovered his love for mathematics. This happened thanks to his teacher, Sigismund Maksay. This interest led him to a remarkable career in math.
Becoming a Professor
Fejér studied mathematics and physics at the University of Budapest and the University of Berlin. One of his teachers was a famous mathematician named Hermann Schwarz. In 1902, Fejér earned his doctorate degree from the University of Budapest, which is now called Eötvös Loránd University.
After getting his degree, Fejér taught at the University of Budapest from 1902 to 1905. Then, he moved to Franz Joseph University in Kolozsvár (now Cluj-Napoca, Romania), where he taught until 1911. In 1911, he returned to the University of Budapest. He became the head of the mathematics department there and stayed in that position until he passed away. He was also chosen to be a member of the Hungarian Academy of Sciences.
Fejér's Influence on Mathematics
During his time as a professor in Budapest, Fejér created a very successful group of mathematicians focused on a field called analysis. He was the main teacher and guide for many students who became extremely famous. Some of his students included John von Neumann, Paul Erdős, George Pólya, and Pál Turán.
Thanks to Fejér, Hungary became a strong center for mathematics. He trained a new generation of students who went on to become leading scientists around the world. His students remembered him as a fascinating and inspiring person. He gave short, fun lectures and often met with students in coffee shops. There, they would talk about math problems and he would share stories about his life and other great mathematicians.
Fejér's own research mainly focused on harmonic analysis and, more specifically, Fourier series. He also worked with other mathematicians on important papers. For example, he collaborated with Carathéodory on entire functions in 1907. He also worked with Frigyes Riesz in 1922 on conformal mappings, providing a simpler proof for the Riemann mapping theorem.
Difficult Times and Later Life
In 1944, Fejér was forced to leave his job because of his Jewish background. One night in December 1944, members of a political group called the Arrow Cross Party came to his house. Fejér and others in his house were taken to the banks of the Danube River. They were about to be shot, but they were saved at the last moment by a phone call from a brave officer.
Fejér was later found in a hospital. This very difficult experience deeply affected him. He even said later that he felt like he had become "an idiot" because of the trauma. However, his colleagues said he continued to work well until the mid-1950s, when he began to show signs of old age.
Lipót Fejér passed away in Budapest on October 15, 1959. He is buried in the famous Kerepesi Cemetery.
Fejér's Personality and Teaching Style
George Pólya, one of Fejér's famous students, wrote about his teacher's unique personality and teaching style. Pólya described Fejér as someone who seemed a bit eccentric, but in a charming way. He had a great sense of humor and enjoyed noticing funny or sad details in everyday life.
Fejér loved music and was a good pianist. He also enjoyed using clever phrases. For example, when he was angry with a colleague who studied topology, he said that what the colleague was saying was "a topological mapping of the truth." This meant it was a distorted version of the truth.
Fejér was also a wonderful storyteller. He would tell stories about the small flaws of great mathematicians, and people found him irresistible. Many mathematicians fondly remember spending hours with Fejér in coffee houses, discussing math and listening to his stories. He presented his mathematical ideas with the same energy as his stories, which helped many younger students become interested in his problems.
Pólya also explained Fejér's mathematical approach. Fejér focused on making every detail clear and easy to understand. He might spend a lot of time on a problem, making sure every step was perfectly transparent. He wasn't known for solving extremely difficult problems or building huge, complex mathematical ideas. Instead, he was excellent at finding important, beautiful problems that had simple solutions. He would then work on these solutions with great care, making his papers very clear and easy to read. This careful work is what made his proofs seem so simple, even though writing them was not easy at all.
Gallery
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(Left to right); Standing: Frigyes Riesz, Béla Kerékjártó, Alfréd Haar, Gyula Kőnig, Rudolf Ortvay; On chairs: József Kürschák, George David Birkhoff, O.D. Kellog, Lipót Fejér; Sitting on the floor: Tibor Radó, István Lipka, László Kalmár, Pál Szász
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Fejér's grave in Kerepesi Cemetery, Budapest
See also
- Fejér window
- Real algebraic geometry
