Patrick Dehornoy (11 September 1952 – 4 September 2019) was a mathematician at the

University of Caen Normandy The University of Caen Normandy (French: ''Université de Caen Normandie''), also known as Unicaen, is a public university in Caen, France. History The institution was founded in 1432 by John of Lancaster, 1st Duke of Bedford, the first rector ...

who worked on

set theory Set theory is the branch of mathematical logic that studies Set (mathematics), sets, which can be informally described as collections of objects. Although objects of any kind can be collected into a set, set theory – as a branch of mathema ...

and

group theory In abstract algebra, group theory studies the algebraic structures known as group (mathematics), groups. The concept of a group is central to abstract algebra: other well-known algebraic structures, such as ring (mathematics), rings, field ( ...

Early life and education

Dehornoy was born on 11 September 1952 in

Rouen Rouen (, ; or ) is a city on the River Seine, in northwestern France. It is in the prefecture of Regions of France, region of Normandy (administrative region), Normandy and the Departments of France, department of Seine-Maritime. Formerly one ...

, France. He graduated from the

Lycée Pierre-Corneille The Lycée Pierre-Corneille (; also known as the Lycée Corneille) is a state secondary school located in the city of Rouen, France. Founded by the Jesuits in 1593, the school was secularized following the 1905 French law on the Separation of th ...

in 1971. He studied at the

École normale supérieure École or Ecole may refer to: * an elementary school in the French educational stages normally followed by Secondary education in France, secondary education establishments (collège and lycée) * École (river), a tributary of the Seine flowing i ...

from 1971 to 1975 and completed his

Ph.D. A Doctor of Philosophy (PhD, DPhil; or ) is a terminal degree that usually denotes the highest level of academic achievement in a given discipline and is awarded following a course of graduate study and original research. The name of the deg ...

in 1978 at the

University of Paris The University of Paris (), known Metonymy, metonymically as the Sorbonne (), was the leading university in Paris, France, from 1150 to 1970, except for 1793–1806 during the French Revolution. Emerging around 1150 as a corporation associated wit ...

, with a thesis written under the direction of Kenneth Walter McAloon.

Career

Dehornoy was a researcher at the

French National Centre for Scientific Research The French National Centre for Scientific Research (, , CNRS) is the French state research organisation and is the largest fundamental science agency in Europe. In 2016, it employed 31,637 staff, including 11,137 tenured researchers, 13,415 engi ...

(CNRS) from 1975 to 1982. He was at the

as a Professor from 1983 to 2017 and as an Emeritus Professor from 2017 until his death. From 2009 to 2013, he was an adjunct scientific director of the ' (INSMI) at the CNRS. Dehornoy died on 4 September 2019 in

Villejuif Villejuif () is a commune in the southern suburbs of Paris, France. It is located from the centre of Paris. Name The earliest reference to Villejuif appears in a bill signed by the Pope Callixtus II on 27 November 1119. It refers to Villa J ...

, France at the age of 66.

Research

Dehornoy found one of the first applications of

large cardinal In the mathematical field of set theory, a large cardinal property is a certain kind of property of transfinite cardinal numbers. Cardinals with such properties are, as the name suggests, generally very "large" (for example, bigger than the least ...

s to algebra by constructing a certain left-invariant

total order In mathematics, a total order or linear order is a partial order in which any two elements are comparable. That is, a total order is a binary relation \leq on some set X, which satisfies the following for all a, b and c in X: # a \leq a ( re ...

, called the Dehornoy order, on the

braid group In mathematics, the braid group on strands (denoted B_n), also known as the Artin braid group, is the group whose elements are equivalence classes of Braid theory, -braids (e.g. under ambient isotopy), and whose group operation is composition of ...

. In his later career, he was a major contributor to the theory of braid groups, including creating a fast algorithm for comparing braids, and was one of the main contributors to the development of Garside methods.

Awards

In 1999, Dehornoy received the

Ferran Sunyer i Balaguer Prize The Ferran Sunyer i Balaguer Prize is a prize in mathematics, first awarded in 1993. It honors Spanish mathematician Ferran Sunyer i Balaguer (1912–1967), a self-taught Catalan mathematician who, despite significant physical disability, was ...

. In 2002, he was elected a senior member of the

Institut Universitaire de France The Institut Universitaire de France (IUF, Academic Institute of France), is a service of the French Ministry of Higher Education that annually distinguishes a small number of university professors for their research excellence, as evidenced by t ...

(renewed in 2007). In 2005, he received the of the French Academy of Sciences. In 2014, he received the

EMS Ems or EMS may refer to: Places and rivers * Domat/Ems, a Swiss municipality in the canton of Grisons * Ems (river) (Eems), a river in northwestern Germany and northeastern Netherlands that discharges in the Dollart Bay * Ems (Eder), a river o ...

Monograph Award for his book ''Foundations of Garside Theory''.

Selected publications

* * * * *

References

External links

* {{DEFAULTSORT:Dehornoy, Patrick 1952 births 2019 deaths 20th-century French mathematicians 21st-century French mathematicians École Normale Supérieure alumni Academic staff of the University of Caen Normandy Scientists from Rouen Group theorists Set theorists Research directors of the French National Centre for Scientific Research University of Paris alumni