Henri Cabannes


Born: 21 January 1923 in Montpellier, Hérault, France
Died: 30 May 2016 in Saint-Cyr-sur-Mer, Var, France

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Henri Cabannes was the son of the physicist Jean Cabannes (1885-1959) and Marie Fabry (1893-1976). Jean Cabannes specialised in optics and was trained in the laboratory of the physicist Charles Fabry (1867-1945) in Marseille. Charles Fabry's brother, the mathematician Eugène Fabry (1856-1944), was the father of Marie Fabry. Jean Cabannes's studies were interrupted by military service during World War I after which he returned to Charles Fabry's laboratory in Marseille to complete his thesis. He then moved to Montpellier where he married Marie on 29 March 1921. Henri was one of his parents' four children.

It was in Montpellier that Henri Cabannes began his schooling. He studied first at the Lycée de Montpellier and then at the Lycée Saint-Louis in Paris. The family had moved to Paris in 1937 when Jean Cabannes was appointed as a professor in the Faculty of Science in Paris. Henri entered the École Polytechnique in 1941 while he was still a pupil in the special preparatory Mathematics class at the lycée Saint-Louis. He then entered the École Polytechnique for a second time when he completed his studies at the lycée but resigned and entered the École Normale Supérieure in October 1942.

One has to understand the situation in France at this time since this was in the middle of World War II. The War had begun on 1 September 1939 with the German invasion of Poland. On 3 September France declared war on Germany. In May 1940 German troops invade Holland, Belgium and Luxemburg moving on to France. German troops entered Paris on 14 June and on 22 June the Franco-German Armistice was signed. This limited the amount of France occupied by German troops and set up a French government in Vichy which cooperated with Germany. We quote Cabannes writing about being in Paris in 1942 [3]:-

In 1942 I was in a class at the lycée Saint-Louis with Jean-Claude Pecker. On 7 June, some of our comrades, including Pecker, arrived at the school with a yellow star. Pecker and I passed the written and then the oral entrance examination to the École Normale Supérieure. The oral ended for the candidates of the occupied zone on 14 July 1942. Pecker immediately tore off his yellow star and the next morning, we left both from Saint-Lazare station for Saint-Germain. We went camping on the land of a brave farmer whose address Pecker had. On 16 July, the French police arrested all Jews in the Paris region and brought them together at the Vélodrome d'Hiver before sending them to Drancy and then to Germany. After a week, the roundup being over, we returned and Pecker went to an unoccupied zone where he lived under a false name.
Early in 1943 the Germans conducted a census of Frenchmen aged 21 to 31 and began to call up Frenchmen born in 1920, 1921 and 1922 to be sent to Germany to undergo military training. Cabannes, being born in 1923, was not affected by this but, nevertheless, he decided to interrupt his studies at the École Normale Supérieure and try to reach England or North Africa.

For Cabannes' own detailed account of his escape to Spain, then North Africa and finally Britain, see THIS LINK.

The war ended in May 1945 and by July Cabannes was back in France. He had left in 1943 before taking his examinations on rational mechanics so he prepared for this and, after being demobbed on 21 October he was examined three days later. He passed the Rational Mechanics certificate and completed his bachelor's degree. He then undertook one further year of study at the École Normale Supérieure.

In 1946 he was appointed as a Research Associate at the Centre National de la Recherche Scientifique. He now undertook research for his doctorate advised by Joseph Pérès. He had already published several papers, the first being Application des fractions continues à la formation de nombres transcendants (1944). He writes about this paper in [2]:-

... during my stay in Britain, I wrote an article on the application of continued fractions to the formation of transcendental numbers; the relations between France and England being restored, I sent this article to my father, who submitted it to the "Revue Scientifique", in which it was published.
He published a second paper on continued fractions, Étude des fractions continues ayant leurs quotients en progression arithmétique ou en progression géométrique (1945), before embarking on the topic for his doctorate.

In [3] Cabannes explains how he chose the area for his research:-

In the Air Force, first in Morocco, but especially in England in the Royal Air Force, I had seen the very important progress made in aviation and aeronautics. Fortunately the Germans had failed to realise the importance of the atomic bomb, but in the field of aeronautics they surpassed the Allies. As early as 1944, they had built the flying bombs, the V1s, which I saw coming crashing down on London, then the V2s, which I heard crashing on London. The Messerschmitt factories in Augsburg had made the first jet planes, which were used at the beginning of 1945. There was already talk of supersonic flights, and the year 2000 was scheduled for landing on the moon. I thought that by working in fluid mechanics, I would participate in the progress of aeronautics and I asked Joseph Pérès to direct my research and my first thesis. Pérès told me that since 1939, France had continued in the study of incompressible fluids, which was sufficient when planes were flying at 300 kilometres an hour, but had become insufficient, especially for the future. He therefore advised me to study the German works on the subject and to make a thesis. At the time I had not yet forgotten the German language, which I had learned in high school, and the French had recovered the maximum number of documents in their zone of occupation in Germany and Austria. The aeronautical documents were entrusted to the Office National d'Etudes et de Recherches Aérospatiales (O.N.E.R.A.), the National Office for Aeronautical Studies and Research, which met at regular intervals with German engineers housed in a hotel. I was invited to these meetings; I was a beginner on the subject and later realized that many of the questions I asked were quite naive. But, following Pérès very judicious advice, on 5 February 1950, I submitted the doctoral thesis 'Contribution a l'étude théorique des fluides compressibles. Écoulements transsoniques. Ondes de choc' . What a difference from the way that theses are done today, where thesis advisors feed their students with a teaspoon!
While he was undertaking the research for his doctorate Cabannes published seven papers: Application du calcul symbolique à l'étude de la dynamique des fils (1948); Étude des écoulements gazeux au voisinage de la vitesse du son (1949); Écoulement potentiel discontinu d'un fluide parfait compressible (1949); Détermination approchée de l'onde de choc détachée (1949); Étude de la singularité au sommet d'une onde de choc attachée, dans un écoulement à deux dimensions (1949); Sur l'onde de choc attachée lorsque la vitesse aval à la pointe de l'obstacle est subsonique (1950); and Calcul de la courbure au sommet de l'onde de choc attachée dans un écoulement de révolution (1950).

In addition to this remarkable publication record, Cabannes had married Madeleine Lebon. Henri and Madeleine were both Roman Catholics and met at the Catholic youth gatherings. Cabannes writes [3]:-

In 1948, a classmate, Madeleine Lebon, and I got married. At the time the two schools Ulm and Sèvres were separated, but promotional outings were an opportunity to get to know each other and were at the origin of several marriages.
In [1] Yvonne Choquet-Bruhat tells us a little about Madeleine Lebon:-
Madeleine had passed the scientific competitive exam, but once at the École Normale Supérieure she had decided to follow studies in philosophy, which was allowed by the rules. She hence did what I had considered and that brought us closer. Madeleine Lebon was a full believer, brought up in a practicing Catholic family where she was happy. She was also very close to her brother and sister. "I have never doubted", she told me one day. My mother pointed out to me that that assertion is not very compatible with the profession of philosopher. Madeleine was, however, a very intelligent woman who had passed, with "very good", both the scientific and literary baccalaureate, a feat I had not managed. As the Aggregation of philosophy did not offer many positions, she had not been admitted to it. She had considered a re-conversion to mathematics - my entire class had been successful at the competitive exam - when marriage and children convinced her to remain a housewife.
Henri and Madeleine Cabannes had five children, Jean-Pierre, Jean-Paul, André, Hélène, and Benoît. We say more about Madeleine and the children below.

Cabannes's doctoral thesis was examined by Henri Villat, Joseph Pérès and Georges Valiron. After the award of his doctorate, he published his thesis in 1952 but we note the quantity of research output that he produced around that time for, following the seven papers listed above, he had published another eight papers before his thesis was published. In 1950 he was appointed as an assistant lecturer in mathematics at the Faculty of Science in Marseille. In the same year he became an external collaborator with the Office National d'Etudes et de Recherches Aérospatiales (O.N.E.R.A.). In 1952 Cabannes was promoted to Professor of Rational Mechanics at the Faculty of Science in Marseille and in the following year he became a member of the council of the French Mathematical Society.

We said above that we would give more details of the Cabannes' children. Yvonne Choquet-Bruhat was appointed to Marseille in 1953 and met up with the Cabannes [1]:-

I had been happy to find, in Marseille, my friends Henri and Madeleine Cabannes. Madeleine was always optimistic, persuaded of the goodness of God in spite of the problems caused by her second son who, she told me, was not "well come". The baby Jean-Paul did not tolerate any dairy product, except Roquefort. The courage and perseverance of Madeleine ensured his survival. In fact Jean-Paul was what was then called a mongoloid. In 1953, the chromosomal origin of this handicap, trisomy twenty-one, was not known. Madeleine spent considerable energy on her son, thinking that assiduous material and intellectual care would make him an ordinary man. She even took him for a Bogomoletz treatment, and persevered in her hope in spite of its failure. Unfortunately, Jean-Paul was a severe case. It is now known that the severity of the harmful effects due to the supernumerary chromosome 21 depends on the location where it is attached to the other two. To her deep regret, pushed by her husband, Madeleine had to resign herself to placing the adolescent Jean-Paul in an appropriate facility in the interest of her other four children, all "well come".
Cabannes spent 9 months as a Visiting Professor at Laval University, Quebec, Canada during 1956-57.

The three children André, Hélène, and Benoît were born while Cabannes was still working at the Faculty of Science in Marseille. Yvonne Choquet-Bruhat writes about them in 1957-8 [1]:-

The Cabannes already had, besides the Down syndrome sufferer Jean-Paul, two boys: Jean-Pierre - a few months older than Michelle [Yvonne Choquet-Bruhat's daughter] - and André - a few months younger - and a girl of little more than a year, Hélène. In the fall of 1957, they had a fifth child, a charming baby, Benoît. It was the time of the baby boom. Madeleine, a devout Catholic, would still want other children, but as she had to have surgery for a fibroma, it stopped her pregnancies. Henri was rather glad of that; he said, "Five is good." Madeleine was helped by a very nice girl living at their home, but her baby, the little Hélène and Jean-Paul did not let her be idle. The two elders went to the public school in Saint Cyr, but still demanded a lot of time from their mother. Madeleine came each morning to take Michelle and drive her to school with her sons. Jean-Pierre and André were half-boarders but I picked Michelle up to have lunch together. ... In general, Madeleine went in the afternoon to pick up the children from school.
In 1960 the Cabannes family moved from Marseille to Paris when he was appointed Professor of General Mechanics at the Faculty of Sciences of Paris. We have details of what Cabannes taught since he published Cours de mécanique générale in 1962. William Prager writes in a review:-
This excellent text corresponds to the course that the author teaches at the Sorbonne. The contents are best indicated by the following titles of chapters and abbreviated headings of sections. 

Part I. General Mechanics: Kinematics (vectors, velocities, accelerations); Kinetics (mass distributions, quantities associated with velocities, quantities associated with accelerations); Principles of mechanics (fundamental law, momentum theorems, search for absolute frames of reference, special theory of relativity); Problem types (statics, dynamics, impact, friction); Work and power (definitions and basic properties, theorem of virtual velocities, units); Differential equations (methods of integration, linear equations, oscillations); Analytical mechanics (Lagrangian equations for holonomic and non-holonomic systems, stability of equilibrium, small oscillations); Rigid bodies (general theory, gyroscopes)

Part II. Introduction to fluid mechanics: Microscopic aspects (concepts of statistical mechanics, hypotheses of kinetic theory, equations of kinetic theory, macroscopic equations); Macroscopic aspects (integral form of equations of motion, equations for continuous motions, equations for discontinuous motions)

The presentation has the clarity that is a characteristic of French texts in this field; vector and tensor equations are used wherever this is advantageous.
In 1966 Cabannes published the collection of exercises Problèmes de mécanique générale and in the same year published a second edition of Cours de mécanique générale .

He spent 3 months as a Visiting Professor at Brown University, Providence, U.S.A. in 1967 and 3 months as a Visiting Professor at the University of California at Berkeley, U.S.A. in 1968. Cabannes was appointed as Professor of General Mechanics at the Pierre and Marie Curie University (Paris 6) in 1969. He continued in this role until he retired in 1990. He also served as Director of the Theoretical Mechanics Laboratory (1975-79).

Cabannes made a second trip to the University of California at Berkeley in 1980 and delivered a set of lectures on the discrete Boltzmann equation as part of a graduate course in the Mechanical Engineering Department. These were later published as The discrete Boltzmann equation (theory and applications)

Evariste Sanchez-Palencia gives the following summary of Cabannes' mathematical contributions [4]:-

The scientific work of Henri Cabannes revolved around various topics. Each theme occupied him exhaustively for periods of five to ten years, where personally he worked hard, while increasing contacts and collaborations in France and abroad, and supervising young researchers, who often pursued the area once he had opened the next.
Topics:
  1. Aerodynamics. Shockwaves attached and detached from obstacles.
  2. Magnetodynamics of fluids.
  3. Kinetic theory of gases. Determination of viscosity and conductivity from particle kinetics.
  4. Discrete kinetic theory. Existence of solutions.
  5. Vibrating ropes with obstacle or solid friction. Periodic and near-periodic solutions.
Throughout his career, Cabannes received many honours. For example, he was awarded the Montyon prize for mechanics by the Académie des sciences in 1960, He became a Corresponding Member of the Académie des Sciences in 1983 and a full member in 1991. He was awarded the Agostinelli Prize by the Accademia Nazionale dei Lincei in 1993 and became a laureate of the Alexander von Humboldt Foundation in 1995. For his efforts during World War II, he was made Chevalier de la Légion d'honneur, Officier de l'Ordre National du Mérite, Commandeur des Palmes Académiques, and holder of the Médaille des Évadés.

In 2002 Cabannes was interviewed by the Romanian "Magazin Istoric" and asked "At present, what do you recommend to young Europeans?". For his reply, see THIS LINK.

Article by: J J O'Connor and E F Robertson


List of References (4 books/articles)

Mathematicians born in the same country

Additional Material in MacTutor
  1. Cabannes and the future of Europe
  2. The Odyssey of Henri Cabannes: 1943-1945

Cross-references in MacTutor

  1. 1970 ICM - Nice

Other Web sites
  1. Mathematical Genealogy Project
  2. MathSciNet Author profile
  3. zbMATH entry


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