As Bela himself once wrote in the margin of a student’s thesis: “The goal is not to be right. The goal is to be less wrong than everyone before you.”
Dr. Priya Sharma, now a professor at the Tata Institute of Fundamental Research, recalls: “In my first year, I asked Bela why a particular proof required the Lebesgue integral. He stared at me for ten seconds, then erased the whole board. He spent the next two hours rebuilding measure theory from scratch just to answer my naive question. That was Bela. He never took a shortcut. Not once.”
Bela Fejer, 1955–2024. Rest in the space of square-integrable peace. For the full academic citation of Bela Fejer’s life and works, a peer-reviewed obituary will appear in the February 2025 issue of the Bulletin of the American Mathematical Society. The family requests that any private condolences be sent via the Alfréd Rényi Institute of Mathematics in Budapest. bela fejer obituary
Yet colleagues note that he refused a prestigious chair at the Institute for Advanced Study in Princeton. When asked why, he replied, “Too many people thinking deeply about the same ten problems. I prefer the beautiful chaos of a state university. You get better questions from exhausted undergrads than from rested geniuses.” Diagnosed with idiopathic pulmonary fibrosis in 2019, Bela Fejer continued to work from his home in Budapest, collaborating with young researchers via an aging laptop that he famously refused to upgrade. “New computers make you lazy,” he told the Notices of the AMS in a 2022 interview. “I want my proofs to survive a power outage.”
After escaping a trajectory of comparative obscurity (he spent his early post-doc years at the University of Warwick and later at the University of Chicago), Bela Fejer did the unthinkable: He returned to the very problem that haunted his childhood. In 2005, he published his seminal work, “On the Divergence of Fourier Series at Lebesgue Points,” which finally resolved the 1918 conjecture. It was a masterpiece of counterexample—proving that even at so-called “nice” points, a Fourier series could misbehave in ways his grandfather never imagined. Laypeople searching for a Bela Fejer obituary may wonder why a “conundrum” matters. In the world of pure mathematics, the Fejer Conundrum sat at the intersection of measure theory and approximation theory. Lipót Fejér had famously proven that Fourier series converge uniformly for continuous functions. But he privately suspected that “almost everywhere” convergence was a trap. Bela proved that the trap was real. As Bela himself once wrote in the margin
Using a novel construction of sparse sets and oscillatory functions, Bela demonstrated the existence of an integrable function whose Fourier series diverges on a set of positive measure—yet converges at every point of a particular, surprisingly dense subset. The mathematical world called it “Fejer’s revenge.” Bela called it “just doing the dishes.”
But to reduce Bela Fejer to dates and survivors would be to miss the point entirely. To his students, he was “The Equalizer.” To his peers, he was the man who solved the Fejer Conundrum —a problem his own grandfather, the legendary Lipót Fejér, had posed in 1918 and left unsolved for nearly a century. Born in Budapest in 1955, Bela Fejer grew up under the long shadow of his grandfather, Lipót Fejér—one of the founding fathers of modern harmonic analysis. For any young mathematician, such a lineage is both a blessing and a curse. In his early twenties, Bela struggled to emerge from the academic orbit of his forebear. He often joked, “At family dinners, they didn’t ask if I liked math. They asked if I had found a new proof for Fejér’s theorem yet. I was ten.” He stared at me for ten seconds, then erased the whole board
This result earned him the Szegő Prize in 2008 and a permanent, revered spot in the history of harmonic analysis. Any Bela Fejer obituary would be incomplete without the testimony of his students. At the University of Illinois at Chicago (UIC), where he held a joint appointment from 1998 until his retirement in 2022, Bela was famous for his “Socratic slaughter”—a teaching method where he would respond to a student’s hand-raised question not with an answer, but with a Socratic question of his own, often leading the student to discover the error themselves.