Alfred Errera (1886 – 1960) was a Belgian

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, structure, space, models, and change. History On ...

. Errera studied at the Université libre de Bruxelles, where he received his

Ph.D. A Doctor of Philosophy (PhD, Ph.D., or DPhil; Latin: or ') is the most common degree at the highest academic level awarded following a course of study. PhDs are awarded for programs across the whole breadth of academic fields. Because it is a ...

in 1921 with dissertation ''Du coloriage des cartes et de quelques questions d'analysis situs''. In his dissertation he introduced what is now called the

Errera graph In the mathematical field of graph theory, the Errera graph is a graph with 17 vertices and 45 edges. Alfred Errera published it in 1921 as a counterexample to Kempe's erroneous proof of the four color theorem; it was named after Errera by . Pr ...

, which is a counterexample to the validity of the alleged proof of the four color theorem by

Alfred Kempe Sir Alfred Bray Kempe FRS (6 July 1849 – 21 April 1922) was a mathematician best known for his work on linkages and the four colour theorem. Biography Kempe was the son of the Rector of St James's Church, Piccadilly, the Rev. John Edward K ...

. From 1928 to 1956 he was a professor at the Université libre de Bruxelles. He did research on

topology In mathematics, topology (from the Greek language, Greek words , and ) is concerned with the properties of a mathematical object, geometric object that are preserved under Continuous function, continuous Deformation theory, deformations, such ...

, especially the theory of

polyhedra In geometry, a polyhedron (plural polyhedra or polyhedrons; ) is a three-dimensional shape with flat polygonal faces, straight edges and sharp corners or vertices. A convex polyhedron is the convex hull of finitely many points, not all on t ...

and the

Jordan curve theorem In topology, the Jordan curve theorem asserts that every ''Jordan curve'' (a plane simple closed curve) divides the plane into an " interior" region bounded by the curve and an "exterior" region containing all of the nearby and far away exterior ...

. With

Théophile Lepage Théophile Lepage (24 March 1901 – 1 April 1991) was a Belgian mathematician. Biography Théophile Henri Joseph Lepage, better known as Théophile Lepage, was born in Limburg on March 24, 1901. Together with Alfred Errera he founded the semin ...

he conducted a seminar on analysis at the University of Brussels. During World War I, he worked on the

acoustic source localization Acoustic location is the use of sound to determine the distance and direction of its source or reflector. Location can be done actively or passively, and can take place in gases (such as the atmosphere), liquids (such as water), and in solids (s ...

of artillery fire and from 1921 to 1938 taught courses on this subject at the Royal Military Academy. Errera was an Invited Speaker at the

International Congress of Mathematicians The International Congress of Mathematicians (ICM) is the largest conference for the topic of mathematics. It meets once every four years, hosted by the International Mathematical Union (IMU). The Fields Medals, the Nevanlinna Prize (to be rename ...

in 1924 in Toronto, in 1932 in Zürich, and in 1936 in Oslo. In 1932 he participated in the Congresul Matematicienilor Români in

Drobeta-Turnu Severin Drobeta-Turnu Severin (), colloquially Severin, is a city in Mehedinți County, Oltenia, Romania, on the northern bank of the Danube, close to the Iron Gates. "Drobeta" is the name of the ancient Dacian and Roman towns at the site, and the modern ...

. In 1935 he gave a talk at the inaugural Congrés International des Récréations Mathématiques in Brussels. His doctoral students include

Guy Hirsch Guy Hirsch (20 September 1915 – 4 August 1993) was a Belgian mathematician and philosopher of mathematics, who worked on algebraic topology and epistemology of mathematics. He became a member of the Royal Flemish Academy of Belgium for Science ...

Selected publications

* ''Un théorème sur les liaisons'', 1923 * ''Periodico matematico'', 1927 * ''Analysis situs: un problème d’énumération'', Brüssel, M. Lamertin 1931 * ''Sur un problème de géométrie infinitésimale'', Brüssel, M. Lamertin 1932

References

External links

* ''Flemish'' {{DEFAULTSORT:Errera, Alfred 20th-century Belgian mathematicians Belgian mathematicians 1886 births 1960 deaths