Lipót Fejér

Lipót Fejér was a Hungarian mathematician, born at Pécs on 9 February 1880 and died in Budapest on 15 October 1959. His main work was in harmonic analysis, on Fourier series and their singularities, and he also worked on power series, potential theory and approximation theory. He studied at the Polytechnic University of Budapest and spent a year at the University of Berlin, where he obtained the results that shaped his career. Fejér's theorem on Fourier series is described in the MacTutor biography as a simple, beautiful theorem. He collaborated with Carathéodory on entire functions and with Riesz on conformal mappings.