Eugène Maurice-Pierre Cosserat

Background

Cosserat was born on March 4, 1866, in Amiens, France. His father was François-Constant Cosserat who was a well-off middle-class entrepreneur who was based in Amiens. Eugène had two brothers: François-Nicolas and Lucien-Constant.

Education

Eugène was educated first in a primary school in Amiens, moving to the Lycée in Amiens for his secondary education which he entered in the autumn of 1877. At first, he was only an average pupil, but once he began to study the sciences he showed considerable aptitude. When he was fourteen years old, in 1880, he was showing exceptional promise and was awarded a prize offered by the Industrial Society of Amiens and also a prize presented by the former pupils of the Lycée.

In the following year, 1880-81, he began to study Elementary Mathematics and his love for the sciences became very clear. He received a bursary for his study of Advanced Mathematics which he attended over the following two years. For his outstanding successes in the first of these years, he was awarded the Municipal Prize, awarded to the best student in the sciences, and for his achievements in the second of the two years, he was awarded the Delambre Prize, given to the best student in the mathematics and physics courses. At the age of 17, he took the competitive entrance examinations for the two major Paris Institutions, the École Polytechnique and the École Normale Supérieure, and was offered a place at both. Unlike his two brothers who both studied at the École Polytechnique, he chose to study at the École Normale Supérieure which he entered in 1883, finishing his studies in 1887.

Career

Cosserat's scientific career was spent in Toulouse: he was assigned to the observatory in 1886, became a professor of differential calculus at the Faculty of Sciences in 1896 and of astronomy in 1908, and was a director of the observatory from 1908 until his death. He was considered one of the moving forces of the University of Toulouse for thirty-five years. He was a membre non-résident of the Académie des Sciences (1919) and a corresponding member of the Bureau des Longitudes (1923).

For the first ten years, Cosserat divided his time between his duties at the observatory, where he made equatorial observations of double stars, planets, and comets, and his research in geometry. His doctoral thesis (1888), which deals with an extension of Pliicker’s concept of the generation of space by means of straight lines, considers the infinitesimal properties of space created by circles. The congruences and complexes of straight lines are the main subject of his later works, in which he remained a disciple of Darboux.

In studying the deformation of surfaces Cosserat was oriented toward the theory of elasticity and the general problem of continuous mediums. These studies were done between 1885 and 1914 in collaboration with his older brother François, who was chief engineer of the Service des Ponts et Chaussées. François was the main participant in tests on the synthesis and philosophical concepts, the mathematical framework of the research being furnished by Eugène. The most practical results concerning elasticity were the introduction of the systematic use of the movable trihedral and the proposal and resolution, before Fredholm’s studies, of the functional equations of the sphere and ellipsoid.

Cosserat’s theoretical research, designed to include everything in theoretical physics that is directly subject to the laws of mechanics, was founded on the notion of Euclidean action combined with Lagrange’s ideas on the principle of extremality and Lie’s ideas on invariance in regard to displacement groups. The bearing of this original and coherent conception was diminished in importance because at the time it was proposed, fundamental ideas were already being called into question by both the theory of relativity and progress in physical theory. The Toulouse observatory participated in the international undertaking of formulating the Carte du Ciel. Having become director, Cosserat organized the important work of meridian observations, photography, and computation of positions in order to make a systematic determination of the proper motions of the stars. He personally supervised the details of these operations, including the computations, and was completely occupied with this task for the last fifteen years of his life. Cosserat was particularly concerned with accuracy: he used his original research, which later appeared as notes in the now-classic works of Darboux, Koenigs, Appell, and Chwolson. Thus, although his name seldom appears in modern works, his influence on them was far-reaching.

Achievements

• Cosserat is best remembered for work with his engineer brother François on surface mechanics, particularly problems of elasticity. It has become known as the theory of micropolar elasticity and has remained an active research area ever since.

Works

More photos

• book

  • Théorie des corps déformables

    (French Edition)

    1909

Membership

• Académie des Sciences , France

  March 31, 1919

Personality

Cosserat was known to be a reserved, kindly man and a diligent worker.

Connections

Cosserat married Berthe Jèze; they had two sons. The eldest, Louis Cosserat, became a medical doctor but their younger son died before reaching adulthood.

Father:

François-Constant Cosserat

Brother:

François-Nicolas Cosserat

He is known by his theories about deformable bodies written with his brother Eugène.

Brother:

Lucien-Constant Cosserat

References

• Dictionary of Scientific Biography Volume 3
  1971
• Lie Pseudogroups And Mechanics
  1988