Monday, November 11, 2019

Emmy Noether: Mathematician Trailblazer (Part I)



Amalie Emmy Noether[a] (German: [ˈnøːtɐ]; 23 March 1882 – 14 April 1935) was a Jewish-German mathematician who made important contributions to abstract algebra and theoretical physics.  She invariably used the name "Emmy Noether" in her life and publications.  She was described by Pavel Alexandrov, Albert Einstein, Jean Dieudonné, Hermann Weyl and Norbert Wiener as the most important woman in the history of mathematics.  As one of the leading mathematicians of her time, she developed the theories of rings, fields, and algebras. In physics, Noether's theorem explains the connection between symmetry and conservation laws.
Noether was born to a Jewish family in the Franconian town of Erlangen; her father was a mathematician, Max Noether. She originally planned to teach French and English after passing the required examinations, but instead studied mathematics at the University of Erlangen, where her father lectured. After completing her dissertation in 1907 under the supervision of Paul Gordan, she worked at the Mathematical Institute of Erlangen without pay for seven years. At the time, women were largely excluded from academic positions. In 1915, she was invited by David Hilbert and Felix Klein to join the mathematics department at the University of Göttingen, a world-renowned center of mathematical research. The philosophical faculty objected, however, and she spent four years lecturing under Hilbert's name. Her habilitation was approved in 1919, allowing her to obtain the rank of Privatdozent.
Noether remained a leading member of the Göttingen mathematics department until 1933; her students were sometimes called the "Noether boys". In 1924, Dutch mathematician B. L. van der Waerden joined her circle and soon became the leading expositor of Noether's ideas; her work was the foundation for the second volume of his influential 1931 textbook, Moderne Algebra. By the time of her plenary address at the 1932 International Congress of Mathematicians in Zürich, her algebraic acumen was recognized around the world. The following year, Germany's Nazi government dismissed Jews from university positions, and Noether moved to the United States to take up a position at Bryn Mawr College in Pennsylvania. In 1935 she underwent surgery for an ovarian cyst and, despite signs of a recovery, died four days later at the age of 53.
Noether's mathematical work has been divided into three "epochs".[5] In the first (1908–1919), she made contributions to the theories of algebraic invariants and number fields. Her work on differential invariants in the calculus of variations, Noether's theorem, has been called "one of the most important mathematical theorems ever proved in guiding the development of modern physics".[6] In the second epoch (1920–1926), she began work that "changed the face of [abstract] algebra".  In her classic 1921 paper Idealtheorie in Ringbereichen (Theory of Ideals in Ring Domains) Noether developed the theory of ideals in commutative rings into a tool with wide-ranging applications. She made elegant use of the ascending chain condition, and objects satisfying it are named Noetherian in her honor. In the third epoch (1927–1935), she published works on noncommutative algebras and hypercomplex numbers and united the representation theory of groups with the theory of modules and ideals. In addition to her own publications, Noether was generous with her ideas and is credited with several lines of research published by other mathematicians, even in fields far removed from her main work, such as algebraic topology.
Personal life
Emmy's father, Max Noether, was descended from a family of wholesale traders in Germany. At age 14, he had been paralyzed by polio. He regained mobility, but one leg remained affected. Largely self-taught, he was awarded a doctorate from the University of Heidelberg in 1868. After teaching there for seven years, he took a position in the Bavarian city of Erlangen, where he met and married Ida Amalia Kaufmann, the daughter of a prosperous merchant.
Max Noether's mathematical contributions were to algebraic geometry mainly, following in the footsteps of Alfred Clebsch. His best known results are the Brill–Noether theorem and the residue, or AF+BG theorem; several other theorems are associated with him; see Max Noether's theorem.
Emmy Noether was born on 23 March 1882, the first of four children.  Her first name was "Amalie", after her mother and paternal grandmother, but she began using her middle name at a young age.
As a girl, Noether was well liked. She did not stand out academically although she was known for being clever and friendly. She was near-sighted and talked with a minor lisp during her childhood. A family friend recounted a story years later about young Noether quickly solving a brain teaser at a children's party, showing logical acumen at that early age.  She was taught to cook and clean, as were most girls of the time, and she took piano lessons. She pursued none of these activities with passion, although she loved to dance.
She had three younger brothers: The eldest, Alfred, was born in 1883, was awarded a doctorate in chemistry from Erlangen in 1909, but died nine years later. Fritz Noether, born in 1884, is remembered for his academic accomplishments; after studying in Munich he made a reputation for himself in applied mathematics. The youngest, Gustav Robert, was born in 1889. Very little is known about his life; he suffered from chronic illness and died in 1928.
University education
Noether showed early proficiency in French and English. In the spring of 1900, she took the examination for teachers of these languages and received an overall score of sehr gut (very good). Her performance qualified her to teach languages at schools reserved for girls, but she chose instead to continue her studies at the University of Erlangen.
This was an unconventional decision; two years earlier, the Academic Senate of the university had declared that allowing mixed-sex education would "overthrow all academic order".  One of only two women in a university of 986 students, Noether was only allowed to audit classes rather than participate fully, and required the permission of individual professors whose lectures she wished to attend. Despite these obstacles, on 14 July 1903 she passed the graduation exam at a Realgymnasium in Nuremberg.
During the 1903–1904 winter semester, she studied at the University of Göttingen, attending lectures given by astronomer Karl Schwarzschild and mathematicians Hermann Minkowski, Otto Blumenthal, Felix Klein, and David Hilbert. Soon thereafter, restrictions on women's participation in that university were rescinded.
Noether returned to Erlangen. She officially reentered the university in October 1904, and declared her intention to focus solely on mathematics. Under the supervision of Paul Gordan she wrote her dissertation, Über die Bildung des Formensystems der ternären biquadratischen Form (On Complete Systems of Invariants for Ternary Biquadratic Forms, 1907). Gordan was a member of the "computational" school of invariant researchers, and Noether's thesis ended with a list of over 300 explicitly worked out invariants. This approach to invariants was later superseded by the more abstract and general approach pioneered by Hilbert.  Although it had been well received, Noether later described her thesis and a number of subsequent similar papers she produced as "crap".

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