Paul Felix Nemenyi (; June 5, 1895 – March 1, 1952) was a Hungarian mathematician and physicist who specialized in continuum mechanics. He was known for using what he called the inverse or semi-inverse approach, which applied vector field analysis, to obtain numerous exact solutions of the nonlinear equations of gas dynamics, many of them representing rotational flows of nonuniform total energy. His work applied geometrical solutions to fluid dynamics. In continuum mechanics, "Nemenyi's theorem" proves that, given any net of isothermal curves, there exists a five parameter family of plane stress systems for which these curves are stress trajectories. Nemenyi's five constant theory for the determination of stress trajectories in plane elastic systems, was subsequently proven by later mathematicians. He was the father of the statistician Peter Nemenyi and the putative father of former World Chess Champion Bobby Fischer. Biography Family Neményi was born to a wealthy Hungarian-Jewish family on June 5, 1895 in Fiume (Rijeka) in the Kingdom of Hungary. His grandfather was Zsigmond Neményi. His father Dezső Neményi was one of the directors at Rijeka Refinery (now INA d.d.). Nemenyi attended elementary and high school in Fiume (Rijeka). He graduated from high school in Budapest. Nemenyi's uncle was Dr. Ambrus Neményi, born in Pécel, c. 20 km east of Budapest. The family's name was Neumann until 1871 when they magyarized it to Neményi. Paul Nemenyi's aunt was Berta Koppély (whose parents were Adolf Koppély (1809-1883) and Rózsa von Hatvany-Deutsch). His family's art collection included works by Klimt, Kandinsky and Matisse. Hungary at the time, was producing a generation of geniuses in the exact sciences, who would be collectively known as Martians, that included Theodore von Kármán (b. 1881), George de Hevesy (b. 1885), Leó Szilárd (b. 1898), Dennis Gabor (b. 1900), Eugene Wigner (b. 1902), John von Neumann (b. 1903), Edward Teller (b. 1908), and Paul Erdős (b. 1913). Mathematical career A child prodigy in mathematics, at the age of 17, Nemenyi won the Hungarian national mathematics competition. Nemenyi obtained his doctorate in mathematics in Berlin in 1922 and was appointed a lecturer in fluid dynamics at the Technical University of Berlin. In the early 1930s, he published a textbook on mathematical mechanics that became required reading in German universities. Stripped of his position when the Nazis came to power, he also had to leave Hungary where anti-Semitic laws had been enacted, and found work for a