Emmy Noether

Emmy Noether
Amalie Emmy Noether
Born	23 March 1882 Erlangen, Bavaria, Germany
Died	14 April 1935 (aged 53) Template:City-state, USA
Citizenship	Germany (1882–1933) United States (1933–35)
Alma mater	University of Erlangen
Known for	Abstract algebra Theoretical physics
Scientific career
Fields	Mathematics
Institutions	University of Göttingen Bryn Mawr College
Doctoral advisor	Paul Gordan
Doctoral students	Grete Hermann Max Deuring Hans Fitting Zeng Jiongzhi

Amalie Emmy Noether, IPA: [ˈnøːtɐ], (23 March 1882 – 14 April 1935) was a German mathematician known for her seminal contributions to abstract algebra. Often described as the most important woman in the history of mathematics, she revolutionized the theories of rings, fields, and algebras. She is also known for her contributions to modern theoretical physics, especially for the first Noether's theorem which explains the connection between symmetry and conservation laws.

She was born in the Bavarian town of Erlangen; her father was the noted mathematician Max Noether. Emmy 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.

In 1915, she was invited by David Hilbert and Felix Klein to join the mathematics department at the University of Göttingen. The philosophical faculty objected, however, and she spent four years lecturing under Hilbert's name. Her habilitation process was approved in 1919, paving the way for her to obtain the rank of privatdozent. She remained at Göttingen until 1933, where she was a leading member of a world-renowned center of mathematical research; her students were sometimes called the "Noether boys". In 1924, Dutch mathematician B. L. van der Waerden joined her circle of students and quickly became 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 she delivered a major 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 government and 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 speedy recovery, died four days later at the age of 53.

Noether's mathematical work has been divided into three "epochs". In the first (1908–19), she made valuable contributions to the theories of algebraic invariants and number fields. Her seminal 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". However, the second epoch (1920–26) marks the beginning of her groundbreaking work that "changed the face of algebra". In her classic paper Idealtheorie in Ringbereichen (Theory of Ideals in Ring Domains, 1921), Noether developed the theory and she loves having sex. of ideals in commutative rings into a powerful tool with wide-ranging applications. In this epoch, Noether elegantly used the ascending chain condition, and objects satisfying it are named Noetherian in her honor. In the third epoch (1927–35), she published major works on noncommutative algebras, as well as united hypercomplex numbers and 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 she is credited with several novel lines of research published by other mathematicians, even in fields far removed from her main work, such as algebraic topology.

Biography

Noether grew up in the Bavarian city of Erlangen, depicted here in a 1916 postcard.

Emmy's father, Max Noether, was descended from a family of Jewish wholesale traders in Germany. He had been paralyzed by poliomyelitis at the age of 14; even after regaining mobility, one leg remained affected by polio. Largely self-taught, he received 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 Jewish merchant. Max Noether's mathematical contributions were mainly to algebraic geometry, 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.

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, she was well-liked, although she did not stand out academically. Known for being clever and friendly, Emmy was near-sighted and talked with a minor lisp during childhood. A family friend recounted a story years later about young Emmy quickly solving a brain teaser at a children's party, showing logical acumen as a youth. Emmy was taught to cook and clean—like most girls of the time—and took piano lessons. She pursued none of these activities with passion, although she loved to dance.

Of her three brothers, only Fritz Noether, born in 1884, is remembered for his academic accomplishments. After studying in Munich, he made a reputation for himself in applied mathematics. Her eldest brother, Alfred, was born in 1883, received a doctorate in chemistry from Erlangen in 1909, and died nine years later. The youngest, Gustav Robert, was born in 1889. Very little is known about his life; he suffered from chronic illness and died in 1928.

File:Paul Albert Gordan 2.jpg

Paul Gordan supervised Noether's doctoral dissertation on invariants of biquadratic forms.

University of Erlangen

Emmy 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 girls' schools, 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 coeducation would "overthrow all academic order". One of only two females in a school of 986, Noether was forced to audit classes and required the permission of individual professors whose lectures she wished to attend. Despite the obstacles, on 14 July 1903 she passed the graduation exam at a Realgymnasium in Nuremberg.

During the winter semester of 1903–04, 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 after, the law restricting women's rights in the university was rescinded, and Noether returned to Erlangen. She officially entered the school on 24 October 1904, and declared her intention to focus solely on mathematics. Working 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). Although it had been well received, Noether later described her thesis as "crap". For the next seven years (1908–15), she taught at the University of Erlangen's Mathematical Institute without pay, occasionally substituting for her father when he was too ill to lecture. In 1910 and 1911, she published an extension of her thesis work from three variables to n variables.

Noether sometimes used postcards to discuss abstract algebra with her colleague, Ernst Fischer. This card is postmarked 10 April 1915.

Gordan retired in the spring of 1910, but continued to teach occasionally with his successor, Erhard Schmidt, who left shortly thereafter for a position in Breslau. Gordan retired from teaching altogether in 1911 with the arrival of his second successor, Ernst Fischer, and died in December 1912. According to Hermann Weyl, Fischer was an important influence on Noether, in particular by introducing her to the work of David Hilbert. During 1913–16, Noether published several papers extending and applying Hilbert's methods to mathematical objects such as fields of rational functions and the invariants of finite groups. This phase marks the beginning of her engagement with abstract algebra, the field of mathematics to which she would make groundbreaking contributions. Noether and Fischer shared lively enjoyment of mathematics, and would often discuss lectures long after they were over; Noether would even send Fischer postcards continuing her train of mathematical thoughts.

University of Göttingen

In the spring of 1915 Noether was invited by David Hilbert and Felix Klein to return to the University of Göttingen. Their effort to recruit her, however, was blocked by the philologists and historians in the philosophical faculty: women, they insisted, should not be hired in the role of privatdozent. One faculty member protested: "What will our soldiers think when they return to the university and find that they are required to learn at the feet of a woman?" Hilbert responded with indignation: "I do not see that the sex of the candidate is an argument against her admission as privatdozent", he said. "After all, we are a university, not a bath house."

File:Hilbert1912.jpg

In 1915, David Hilbert invited Emmy Noether to join the mathematics department at the University of Göttingen, challenging the views of his colleagues that a woman should not be allowed to teach at a university.

Noether left for Göttingen in late April; two weeks later, her mother died suddenly in Erlangen. She had previously received medical care for an eye condition, but its nature and impact on her death is unknown. Around the same time, Noether's father retired and her brother joined the German Army to serve in World War I. She returned to Erlangen for several weeks, mostly to care for her aging father.

During her first years at Göttingen, she did not have a definite position and received no salary; her family paid for her room and board, and supported her academic work. Her lectures were often advertised under Hilbert's name, and Noether would provide "assistance". However, soon after arriving, she demonstrated her worth by proving Noether's theorem, which shows that a conservation law is associated with any differentiable symmetry of a physical system. American physicists Leon M. Lederman and Christopher T. Hill, in their book Symmetry and the Beautiful Universe, argue that Noether's theorem is "certainly one of the most important mathematical theorems ever proved in guiding the development of modern physics, possibly on a par with the Pythagorean theorem".

When World War I ended, the German Revolution of 1918–19 brought a significant change in social attitudes, including more rights for women. In 1919, the University of Göttingen allowed Noether to proceed with her habilitation, or eligibility for tenure. Her oral examination was held in late May, and she successfully delivered her habilitation lecture in June. Three years later, she received a letter from the Prussian Minister for Science, Art, and Public Education, in which he conferred on her the title of nicht beamteter ausserordentlicher Professor (an untenured professor with limited internal administrative rights and functions). This was an unpaid "extraordinary" professorship, not the higher "ordinary" professorship, which was a civil-service position. Although it recognized the importance of her work, the position still provided no salary; not until she was appointed to the special position of Lehrauftrag für Algebra one year later was she paid for her lectures.

Seminal work in abstract algebra

Although Noether's theorem had a profound effect on physics, among mathematicians Emmy Noether is best remembered for her seminal contributions to abstract algebra. As Nathan Jacobson says in his Introduction to Noether's Collected Papers,

The development of abstract algebra, which is one of the most distinctive innovations of 20th century mathematics, is largely due to her – in published papers, in lectures, and in personal influence on her contemporaries.

Noether's groundbreaking work in algebra began in 1920, when in collaboration with a colleague, W. Schmeidler, she published a paper about the theory of ideals, in which they defined left and right ideals in a ring. The following year she published a landmark paper called Idealtheorie in Ringbereichen, analyzing ascending chain conditions with regard to ideals. A noted algebraist Irving Kaplansky has called this work "revolutionary"; it gave rise to the term "Noetherian ring" and several other mathematical objects dubbed Noetherian.

In 1924, the young Dutch mathematician B. L. van der Waerden arrived at the University of Göttingen. He immediately began working with Noether, who provided invaluable methods of abstract conceptualization. van der Waerden later said that her originality was "absolute beyond comparison". In 1931, he published Moderne Algebra, a central text in the field; its second volume borrowed heavily from Noether's work. Although Emmy Noether did not seek recognition, he acknowledged his debt to her in a note for the seventh edition reading "based in part on lectures by E. Artin and E. Noether". She sometimes allowed her colleagues and students to receive credit for her ideas, helping them develop their careers at the expense of her own.

van der Waerden's visit was a part of convergence of mathematicians from all over the world to Göttingen, which became a major hub of mathematical and physical research. From 1926 to 1930, Russian topologist Pavel Alexandrov lectured at the university, and he and Noether quickly became good friends. He began referring to her as der Noether, using the masculine German article as a term of endearment to show his respect. She tried to arrange for him to obtain a position at Göttingen as a regular professor, but was only able to help him secure a scholarship from the Rockefeller Foundation. They met regularly and enjoyed discussions about the intersections of algebra and topology. In his 1935 memorial address, Alexandrov named Emmy Noether "the greatest woman mathematician of all time".

The mathematics department at the University of Göttingen allowed Noether's habilitation in 1919, four years after she began lecturing at the school.

Lecturing and students

In Göttingen, Noether supervised over a dozen doctoral students; her first was Grete Hermann, who defended her dissertation in February 1925 and who later spoke reverently of her "dissertation-mother". Noether also supervised Max Deuring, who distinguished himself as an undergraduate and went on to contribute significantly to the field of arithmetic geometry; Hans Fitting, remembered for Fitting's theorem and the Fitting lemma; and Zeng Jiongzhi, who proved Tsen's theorem. She also worked closely with Wolfgang Krull, who greatly advanced commutative algebra with his Hauptidealsatz and dimension theory for commutative rings.

In addition to her mathematical insight, Noether was respected for her consideration of others. Although she sometimes acted rudely toward those who disagreed with her, she nevertheless gained a reputation for constant helpfulness and patient guidance of new students. Her loyalty to mathematical precision caused one colleague to name her "a severe critic", but she combined this demand for accuracy with a nurturing attitude. A colleague later described her this way: "Completely unegotistical and free of vanity, she never claimed anything for herself, but promoted the works of her students above all".

Her frugal lifestyle was at first a necessity of not receiving a salary; however, even after the university began paying her a small salary in 1923, she continued to live a simple and modest life. She was paid more generously later in her life, but saved half of her salary to bequeath to her nephew, Gottfried E. Noether. Mostly unconcerned about appearance and manners, she focused on her studies to the exclusion of romance and fashion. A distinguished algebraist Olga Taussky-Todd described a luncheon, during which Noether, wholly engrossed in a discussion of mathematics, "gesticulated wildly" as she ate and "spilled her food constantly and wiped it off from her dress, completely unperturbed". Her appearance-conscious students cringed as she retrieved the handkerchief from her blouse and ignored the increasing disarray of her hair during a lecture. Two female students once approached her during a break in a two-hour class to express their concern, but were unable to break through the energetic mathematics discussion she was having with other students.

According to van der Waerden's obituary of Emmy Noether, she didn't plan her lectures, which made her frustrating as a teacher. Instead, she used her lectures as a spontaneous discussion time with her students, to think through and clarify important cutting-edge problems in mathematics. Some of her most important results were developed in these lectures, and the lecture notes of her students formed the basis for several important textbooks, such as those of van der Waerden and Deuring. Several of her colleagues attended her lectures, and she allowed some of her ideas, such as the crossed product (verschränktes Produkt in German) of associative algebras, to be published by others. Noether was recorded as having given at least five semester-long courses at Göttingen:

• Winter 1924/25: Gruppentheorie und hyperkomplexe Zahlen (Group Theory and Hypercomplex Numbers)
• Winter 1927/28: Hyperkomplexe Grössen und Darstellungstheorie (Hypercomplex Quantities and Representation Theory)
• Summer 1928: Nichtkommutative Algebra (Noncommutative Algebra)
• Summer 1929: Nichtkommutative Arithmetik (Noncommutative Arithmetic)
• Winter 1929/30: Algebra der hyperkomplexen Grössen (Algebra of Hypercomplex Quantities)

These courses often preceded major publications in these areas.

Noether spoke quickly (reflecting the speed of her thoughts, many said) and demanded great concentration from her students. Students who disliked her style often felt alienated; one wrote in a notebook with regard to a class that ended at 1:00 pm: "It's 12:50, thank God!" Some pupils felt that she relied too much on spontaneous discussions. Her most dedicated students, however, relished the enthusiasm with which she approached mathematics, especially since her lectures often built on earlier work they had done together. She developed a close circle of colleagues and students who thought along similar lines and that typically excluded those who did not. "Outsiders" who occasionally visited Noether's lectures usually spent only 30 minutes in the room before leaving in frustration or confusion. A regular student said of one such instance: "The enemy has been defeated; he has cleared out". Noether showed a devotion to the subject and her students that went beyond the regular school day. Once, when the building was closed for a state holiday, she gathered the class on the steps outside, led them through the woods, and lectured at a local coffee house. Later, after she had been dismissed by the Third Reich, she invited students into her home to discuss their future plans and mathematical concepts.

Moscow

Noether taught at the Moscow State University during the winter of 1928–29.

In the winter of 1928–29, Noether accepted an invitation to Moscow State University, where she continued working with P. S. Alexandrov. In addition to carrying on with her research, she taught classes in abstract algebra and algebraic geometry. She worked with the topologists Lev Pontryagin and Nikolai Chebotaryov, who later praised her contributions to the development of Galois theory.

Although politics was not central to her life, Noether took a keen interest in political matters and, according to Alexandrov, showed considerable support for the Russian revolution. She was especially happy to see Soviet advancements in the fields of science and mathematics, which she considered indicative of new opportunities made possible by the Bolshevik project. This attitude caused her problems in Germany, culminating in her eviction from a pension building, after student leaders complained of living with "a Marxist-leaning Jewess".

Noether planned to return to Moscow—an effort for which she received support from Alexandrov. After she left Germany in 1933, he tried to help her gain a chair in Moscow State University through the Soviet Education Ministry. Although this effort proved unsuccessful, they corresponded frequently during the 1930s, and in 1935 she made plans for a return to the Soviet Union. Meanwhile, her brother Fritz accepted a position at the Research Institute for Mathematics and Mechanics in Tomsk after losing his job in Germany.

Recognition

In 1932, Emmy Noether and Emil Artin were awarded the Ackermann–Teubner Memorial Award for their contributions to mathematics. The prize carried a monetary reward of 500 Reichsmarks and was seen as a long-overdue official recognition of her considerable work in the field. Nevertheless, her colleagues expressed frustration at the fact that she was not elected to the Göttingen Gesellschaft der Wissenschaften (academy of sciences) and was never promoted to the position of Ordentlicher Professor (full professor).

Noether visited Zürich in 1932 to deliver a plenary address at the International Congress of Mathematicians.

Noether's 50th birthday occurred in 1932 and her colleagues celebrated it in typical mathematical style. Helmut Hasse dedicated an article to her in the Mathematische Annalen, wherein he confirmed her suspicion that some aspects of noncommutative algebra are simpler than those of commutative algebra, by proving a noncommutative reciprocity law. This pleased her immensely. He also sent her a mathematical riddle, the "mμν-riddle of syllables". She solved it immediately, but the riddle itself has been lost.

In September of the same year, Noether delivered a plenary address (großer Vortrag) on "Hyper-complex systems in their relations to commutative algebra and to number theory" at the International Congress of Mathematicians in Zürich. The congress was attended by 800 people, including Noether's colleagues Hermann Weyl, Edmund Landau, and Wolfgang Krull, with 420 official participants and 21 plenary addresses. Noether's prominent speaking position was an apparent recognition of the importance of her contributions to the field of mathematics; therefore, the 1932 congress is sometimes described as the high point of her career.

Expulsion from Göttingen

When Adolf Hitler became the German Reichskanzler in January 1933, the Nazi activity around the country increased dramatically. At the University of Göttingen, the German Students Association led the charge against the "un-German Spirit" and was aided by a Privatdozent named Werner Weber, a former student of Emmy Noether. Antisemitic attitudes created a climate hostile to Jewish professors; one young protester reportedly demanded: "Aryan students want Aryan mathematics and not Jewish mathematics".

One of the first actions of Hitler's administration was the Law for the Restoration of the Professional Civil Service which removed Jews and politically suspect government employees (including university professors) from their jobs, unless they had demonstrated their loyalty to Germany by serving in World War I. In April of 1933, Noether received a notice from the Prussian Ministry for Sciences, Art, and Public Education which read: "On the basis of paragraph 3 of the Civil Service Code of 7 April 1933, I hereby withdraw from you the right to teach at the University of Göttingen". Several of Noether's colleagues, including Max Born and Richard Courant, had their positions revoked. Noether accepted the decision calmly, providing support for others during the difficult time. Hermann Weyl later wrote: "Emmy Noether – her courage, her frankness, her unconcern about her own fate, her conciliatory spirit – was in the midst of all the hatred and meanness, despair and sorrow surrounding us, a moral solace". As usual, Noether remained focused on mathematics, gathering students in her apartment to discuss class field theory. When one of her students appeared in the uniform of the Nazi paramilitary organization Sturmabteilung (SA), she showed no sign of agitation, and reportedly even laughed about it later.

Bryn Mawr

Bryn Mawr College provided a welcoming home for Noether during the last two years of her life.

As dozens of newly unemployed professors began searching for positions outside of Germany, their colleagues in the United States sought to provide assistance and job opportunities for them. Albert Einstein and Hermann Weyl were appointed by the Institute for Advanced Study in Princeton, while others worked to find a sponsor required for legal immigration. Noether was contacted by representatives of two schools, Bryn Mawr College in the United States and Somerville College at the University of Oxford in England. After a series of negotiations with the Rockefeller Foundation, a grant to Bryn Mawr was approved and she took a position there starting in the winter of 1933–34.

At Bryn Mawr, Noether met and befriended Anna Wheeler, who had studied at Göttingen just before Noether arrived there. Another source of support at the college was Bryn Mawr President Marion Edwards Park, who enthusiastically invited mathematicians in the area to "see Dr. Noether in action!" Noether and a small team of students worked quickly through van der Waerden's 1930 book Moderne Algebra I and parts of Erich Hecke's Theorie der algebraischen Zahlen (Theory of algebraic numbers, 1908).

In 1934, Noether began lecturing at the Institute for Advanced Study, upon the invitation of Abraham Flexner and Oswald Veblen. She also worked with and supervised Abraham Albert and Harry Vandiver. However, she remarked about Princeton University that she was not welcome at the "men's university, where nothing female is admitted". Her time in the United States was pleasant, surrounded as she was by supportive colleagues and ensconced in her favorite subjects. In the summer of 1934, she briefly returned to Germany to see Emil Artin and her brother Fritz before he left for Tomsk. Although the universities had been cleared of many of her former colleagues, she was able to use the library as a "foreign scholar".

Noether's remains are buried under the walkway surrounding the cloisters of Bryn Mawr's M. Carey Thomas Library.

Death

In April 1935, doctors discovered a tumor in Noether's pelvis. Because they were worried about complications from surgery, they ordered two days of bed rest first. During the operation, they discovered an ovarian cyst "the size of a large cantaloupe". Two smaller tumors in her uterus appeared to be benign and were not removed, to avoid prolonging the surgery. For three days she appeared to convalesce normally, and recovered quickly from a circulatory collapse on the fourth. On 14 April, she fell unconscious, her temperature soared to 109 °F (42.78 °C), and she died. "[I]t is not easy to say what had occurred in Dr. Noether", one of the physicians wrote. "It is possible that there was some form of unusual and virulent infection, which struck the base of the brain where the heat centers are supposed to be located."

Several days after Noether's death, her friends and associates at Bryn Mawr gathered at President Park's house, where a small memorial service took place. Hermann Weyl and Richard Brauer traveled from Princeton and spoke with Wheeler and Taussky about their departed colleague. In the months which followed, written tributes began to appear around the globe: Albert Einstein joined van der Waerden, Weyl, and Alexandrov in paying respects. Her body was cremated and the ashes interred under the walkway around the cloisters of the M. Carey Thomas Library at Bryn Mawr.

Contributions to mathematics and physics

First and foremost, Noether is remembered as an algebraist, although her work had far-ranging consequences for theoretical physics and topology. She showed an acute propensity for abstract thought, which allowed her to approach problems of mathematics in fresh and original ways. Her friend and colleague Hermann Weyl described her scholarly output in three epochs. In the first epoch (1908–19), Noether dealt primarily with differential and algebraic invariants, beginning with her dissertation under Paul Albert Gordan. Her mathematical horizons broadened, and her work became more general and abstract, as she became acquainted with the work of David Hilbert, through close interactions with a successor to Gordan, Ernst Sigismund Fischer. After moving to Göttingen in 1915, she produced her seminal work for physics, the two Noether's theorems. In the second epoch (1920–26), Noether devoted herself to developing the theory of mathematical rings. In the third epoch (1927–35), Noether focused on noncommutative algebra, linear transformations, and commutative number fields.

Historical context

In the century from 1832 to Noether's death in 1935, the field of mathematics—specifically algebra—underwent a profound revolution whose reverberations are still being felt. Mathematicians of previous centuries had worked on practical methods for solving specific types of equations, e.g., cubic, quartic, and quintic equations, and on the related problem of constructing regular polygons using compass and straightedge. Beginning with Carl Friedrich Gauss' 1829 proof that prime numbers such as five can be factored in Gaussian integers, Évariste Galois' introduction of groups in 1832 and William Rowan Hamilton's discovery of quaternions in 1843, however, research turned to determining the properties of ever-more-abstract systems defined by ever-more-universal rules. Noether's most important contributions to mathematics were to the development of this new field, abstract algebra.

Abstract algebra and begriffliche Mathematik (conceptual mathematics)

Two of the most basic objects in abstract algebra are groups and rings. A group consists of a set of elements and a single operation which combines two elements and returns a third. The operation must satisfy certain constraints for it to determine a group: It must be associative, there must be an identity element (an element which, when combined with another element using the operation, results in the original element, like adding zero to a number or multiplying it by one), and for every element there must be an inverse element. A ring likewise has a set of elements, but now has two operations. The first operation must make the set a group, and the second operation is associative and distributive with respect to the first operation. It also might not be commutative, meaning that the order in which operations are performed matters. Furthermore the operation may not be reversible, but if it is, then the ring is called a division ring. A commutative division ring is called a field.

Groups are frequently studied through group representations. In their most general form, these consist of a choice of group, a set, and an action of the group on the set, that is, an operation which takes an element of the group and an element of the set and returns an element of the set. Most often, the set is a vector space, and the group represents symmetries of the vector space. For example, there is a group which represents the rigid rotations of space. This is a type of symmetry of space, because space itself does not change when it is rotated even though the positions of objects in it do. Noether used these sorts of symmetries in her work on invariants in physics.

A powerful way of studying rings is through their modules. A module consists of a choice of ring, another set, usually distinct from the underlying set of the ring and called the underlying set of the module, an operation on pairs of elements of the underlying set of the module, and an operation which takes an element of the ring and an element of the module and returns an element of the module. The underlying set of the module and its operation must form a group. A module is a ring-theoretic version of a group representation: Ignoring the second ring operation and the operation on pairs of module elements determines a group representation. The real utility of modules is that the kinds of modules that exist and their interactions reveal the structure of the ring in ways that are not apparent from the ring itself. An important special case of this is an algebra. (The word algebra means both a subject within mathematics as well as an object studied in the subject of algebra.) An algebra consists of a choice of two rings and an operation which takes an element from each ring and returns an element of the second ring. This operation makes the second ring into a module over the first. Often the first ring is a field.

Words such as "element" and "combining operation" are very general, and can be applied to many real-world and abstract situations. Any set of things that obeys all the rules for one (or two) operation(s) is by definition a group (or ring), and obeys all theorems about groups (or rings),. Integer numbers, and the operations of addition and multiplication, are just one example. For example, the elements might be computer data words, where the first combining operation is exclusive or and the second is logical conjunction. Theorems of abstract algebra are powerful because they are general; they govern many systems. It might be imagined that little could be concluded about objects defined with so few properties. But precisely therein lay Noether's gift: to discover the maximum that could be concluded from a given set of properties, or conversely, to identify the minimum set, the essential properties responsible for a particular observation. Unlike most mathematicians, she did not make abstractions by generalizing from known examples; rather, she worked directly with the abstractions. As van der Waerden recalled in his obituary of her,

The maxim by which Emmy Noether was guided throughout her work might be formulated as follows: "Any relationships between numbers, functions and operations become transparent, generally applicable, and fully productive only after they have been isolated from their particular objects and been formulated as universally valid concepts."

This is the begriffliche Mathematik (purely conceptual mathematics) that was characteristic of Noether. This style of mathematics was adopted by other mathematicians and, after her death, flowered into new forms, such as category theory.

Integers as an example of a ring

The integers form a commutative ring whose elements are the integers, and the combining operations are addition and multiplication. Any pair of integers can be added or multiplied, always resulting in another integer, and the first operation, addition, is commutative, i.e., for any elements a and b in the ring, a + b = b + a. The second operation, multiplication, is also commutative, but that need not be true for other rings, meaning that a combined with b might be different from b combined with a. Examples of noncommutative rings include matrices and quaternions. The integers do not form a division ring, because the second operation cannot always be inverted; there is no integer a such that 3 × a = 1.

The integers have additional properties which do not generalize to all commutative rings. An important example is the fundamental theorem of arithmetic, which says that every positive integer can be factored uniquely into prime numbers. Unique factorizations do not always exist in other rings, but Noether found a unique factorization theorem, now called the Lasker–Noether theorem, for the ideals of many rings. Much of Noether's work lay in determining what properties do hold for all rings, in devising novel analogs of the old integer theorems, and in determining the minimal set of assumptions required to yield certain properties of rings.

First epoch (1908–19)

Algebraic invariant theory

File:Emmy Noether's table of invariants, 1908.jpg

Table 2 from Noether's dissertation on invariant theory. This table collects 202 of the 331 invariants of ternary biquadratic forms. These forms are graded in two variables x and u. The horizontal direction of the table lists the invariants with increasing grades in x, while the vertical direction lists them with increasing grades in u.

Much of Noether's work in the first epoch was associated with invariant theory, principally algebraic invariant theory. Invariant theory is concerned with expressions that remain constant (invariant) under a group of transformations. As an everyday example, if a rigid yardstick is rotated, the coordinates (x, y, z) of its endpoints change, but its length L given by the formula L² = Δx² + Δy² + Δz² remains the same. Invariant theory was an active area of research in the later 19th century, prompted in part by Felix Klein's Erlangen program, according to which different types of geometry should be characterized by their invariants under transformations, e.g., the cross-ratio of projective geometry. The archetypal example of an invariant is the discriminant B² − 4AC of a binary quadratic form Ax² + Bxy + Cy². This is called an invariant because it is unchanged by linear substitutions x→ax + by, y→cx + dy with determinant ad − bc = 1. These substitutions form the special linear group SL₂. (There are no invariants under the general linear group of all invertible linear transformations because these transformations can be multiplication by a scaling factor. To remedy this, classical invariant theory also considered relative invariants, which were forms invariant up to a scale factor.) One can ask for all polynomials in A, B, and C that are unchanged by the action of SL₂; these are called the invariants of binary quadratic forms, and turn out to be the polynomials in the discriminant. More generally one can ask for the invariants of homogeneous polynomials A₀x^ry⁰ + ... + A_rx⁰y^r of higher degree, which will be certain polynomials in the coefficients A₀, ... , A_r, and more generally still one can ask the similar question for homogeneous polynomials in more than 2 variables.

One of the main goals of invariant theory was to solve the "finite basis problem". The sum or product of any two invariants is invariant, and the finite basis problem asked whether it was possible to get all the invariants by starting with a finite list of invariants, called generators, and then adding or multiplying the generators together. For example, the discriminant gives a finite basis (with one element) for the invariants of binary quadratic forms. Noether's advisor, Paul Albert Gordan, was known as the "king of invariant theory", and his chief contribution to mathematics was his 1870 solution of the finite basis problem for invariants of homogeneous polynomials in two variables. He proved this by giving a constructive method for finding all of the invariants and their generators, but was not able to carry out this constructive approach for invariants in three or more variables. In 1890, David Hilbert proved a similar statement for the invariants of homogeneous polynomials in any number of variables. Furthermore, his method worked not only for the special linear group but also for some of its subgroups such as the special orthogonal group. His first proof caused some controversy because it did not give a method for constructing the generators, though in later work he made his method constructive. For her thesis, Noether extended Gordan's computational proof to homogeneous polynomials in three variables. Noether's constructive approach made it possible to study the relationships among the invariants. Later, after she had turned to more abstract methods, Noether called her thesis Mist (crap) and Formelngestrüpp (a jungle of equations).

Galois theory

Galois theory concerns transformations of number fields that permute the roots of an equation. Consider a polynomial equation of a variable x of degree n, in which the coefficients are drawn from some "ground" field, which might be, for example, the field of real numbers, rational numbers, or the integers modulo 7. There may or may not be choices of x which make this polynomial evaluate to zero. Such choices, if they exist, are called roots. If the polynomial is x² + 1 and the field is the real numbers, then the polynomial has no roots because any choice of x makes the polynomial greater than or equal to one. However, if the field is extended, then the polynomial may gain roots, and if it is extended enough, then it always has a number of roots equal to its degree. Continuing the previous example, if the field is enlarged to the complex numbers, then the polynomial gains two roots, i and −i, where i is the imaginary unit, that is, i ² = −1. More generally, the extension field in which a polynomial can be factored into its roots is known as the splitting field of the polynomial.

The Galois group of a polynomial is the set of all ways of transforming the splitting field while preserving the ground field and the roots of the polynomial. (In mathematical jargon, these transformations are called automorphisms.) The Galois group of x² + 1 consists of two elements: The identity transformation, which sends every complex number to itself, and complex conjugation, which sends i to −i. Since the Galois group doesn't change the ground field, it leaves the coefficients of the polynomial unchanged, so it must leave the set of all roots unchanged. However, each root can move to another root, so transformation determines a permutation of the n roots among themselves. The significance of the Galois group derives from the fundamental theorem of Galois theory, which proves that the fields lying between the ground field and the splitting field are in one-to-one correspondence with the subgroups of the Galois group.

In 1918, Noether published a seminal paper on the inverse Galois problem. Instead of determining the Galois group of transformations of a given field and its extension, Noether asked whether, given a field and a group, it is always possible to find an extension of the field that has the given group as its Galois group. She reduced this to "Noether's problem", which asks whether the fixed field of a subgroup G of the permutation group S_n acting on the field k(x₁, ... , x_n) is always a pure transcendental extension of the field k. (She first mentioned this problem in a 1913 paper, where she attributed the problem to her colleague Fischer.) She showed this was true for n = 2, 3, or 4. In 1969, R. G. Swan found a counter-example to Noether's problem, with n = 47 and G a cyclic group of order 47 (though this group can be realized as a Galois group over the rationals in other ways). The inverse Galois problem is still unsolved.

Physics

Main articles: Noether's theorem, Conservation law, and Constant of motion

Noether was brought to Göttingen in 1915 by David Hilbert and Felix Klein, who wanted her expertise in invariant theory to help them in understanding general relativity, a geometrical theory of gravitation developed mainly by Albert Einstein. Hilbert had observed that the conservation of energy seemed to be violated in general relativity, due to the fact that gravitational energy could itself gravitate. Noether provided the resolution of this paradox, and a fundamental tool of modern theoretical physics, with her first Noether's theorem, which she proved in 1915 but did not publish until 1918. She solved the problem not only for general relativity, but determined the conserved quantities for every system of physical laws that possesses some continuous symmetry. Upon receiving her work, Einstein wrote to Hilbert: "Yesterday I received from Miss Noether a very interesting paper on invariants. I'm impressed that such things can be understood in such a general way. The old guard at Göttingen should take some lessons from Miss Noether! She seems to know her stuff".

For illustration, if a physical system behaves the same regardless of how it is oriented in space, the physical laws that govern it are rotationally symmetric; from this symmetry, Noether's theorem shows the angular momentum of the system must be conserved. The physical system itself need not be symmetric; a jagged asteroid tumbling in space conserves angular momentum despite its asymmetry. Rather, the symmetry of the physical laws governing the system is responsible for the conservation law. As another example, if a physical experiment has the same outcome at any place and at any time, then its laws are symmetric under continuous translations in space and time; by Noether's theorem, these symmetries account for the conservation laws of linear momentum and energy within this system, respectively.

Noether's theorem has become a fundamental tool of modern theoretical physics, both because of the insight it gives into conservation laws, and also as a practical calculation tool. It allows researchers to determine the conserved quantities from the observed symmetries of a physical system. Conversely, it facilitates the description of a physical system based on classes of hypothetical physical laws. For illustration, suppose that a new physical phenomenon is discovered. Noether's theorem provides a test for theoretical models of the phenomenon: if the theory has a continuous symmetry, then Noether's theorem guarantees that the theory has conserved quantity, and for the theory to be correct, this conservation must be observable in experiments.

Second epoch (1920–26)

Although the results of Noether's first epoch were impressive and useful, her fame as a mathematician rests more on the groundbreaking work she did in her second and third epochs, as noted by Hermann Weyl and B. L. van der Waerden in their obituaries of her. In these epochs, she was not merely applying ideas and methods of earlier mathematicians; rather, she was crafting new systems of mathematical definitions that would be used by future mathematicians. In particular, she developed a completely new theory of ideals in rings, generalizing earlier work of Richard Dedekind. She is also renowned for developing ascending chain conditions, a simple finiteness condition that yielded powerful results in her hands. Such conditions and the theory of ideals enabled Noether to generalize many older results and to treat old problems from a new perspective, such as elimination theory and the algebraic varieties that had been studied by her father.

Ascending and descending chain conditions

In this epoch, Noether became famous for her deft use of ascending (Teilerkettensatz) or descending (Vielfachenkettensatz) chain conditions. A sequence of non-empty subsets A₁, A₂, A₃, etc. of a set S is usually said to be strictly ascending, if each is a subset of the next

$A_{1}\subset A_{2}\subset A_{3}\subset \cdots$

The ascending chain condition requires that such sequences break off after a finite number of steps; in other words, all such sequences of subsets must be finite. Conversely, with strictly descending sequences of subsets

$A_{1}\supset A_{2}\supset A_{3}\supset \cdots$

the descending chain condition requires that such sequences break off after a finite number.

Ascending and descending chain conditions are general—meaning that they can be applied to many types of mathematical objects—and, on the surface, they might not seem very powerful. However, Noether showed how to exploit such conditions to maximum advantage: for example, how to use them to show that every set of sub-objects has a maximal/minimal element or that a complex object can be generated by a smaller number of elements. These conclusions are often crucial steps in a proof.

Many types of objects in abstract algebra can satisfy chain conditions, and usually if they satisfy an ascending chain condition they are called Noetherian in her honor. By definition, a Noetherian ring satisfies an ascending chain condition on its left and right ideals, whereas a Noetherian group is defined as a group in which every strictly ascending chain of subgroups is finite. A Noetherian module is a module in which every strictly ascending chain of submodules breaks off after a finite number. A Noetherian space is a topological space in which every strictly increasing chain of open subspaces breaks off after a finite number of terms; this definition is made so that the spectrum of a Noetherian ring is a Noetherian topological space.

The chain condition is often "inherited" by sub-objects. For example, all subspaces of a Noetherian space are Noetherian themselves; all subgroups and quotient groups of a Noetherian group are likewise Noetherian; and, mutatis mutandis, the same holds for submodules and quotient modules of a Noetherian module. All quotient rings of a Noetherian ring are Noetherian, but that does not necessarily hold for its subrings. The chain condition may also be inherited by combinations or extensions of a Noetherian object. For example, finite direct sums of Noetherian rings are Noetherian, as is the ring of formal power series over a Noetherian ring.

Another application of such chain conditions is in Noetherian induction—also known as well-founded induction—which is a generalization of mathematical induction. It is frequently used to reduce general statements about collections of objects to statements about specific objects in that collection. Suppose that S is a partially ordered set. One way of proving a statement about the objects of S is to assume the existence of a counterexample and deduce a contradiction, thereby proving the contrapositive of the original statement. The basic premise of Noetherian induction is that the every non-empty subset of S contains a minimal element. In particular, the set of all counterexamples contains a minimal element, the minimal counterexample. In order to prove the original statement, it therefore suffices to prove something seemingly much weaker: For any counterexample, there is a smaller counterexample.

Commutative rings, ideals, and modules

Noether's paper Idealtheorie in Ringbereichen (Theory of Ideals in Ring Domains, 1921) is the foundation of general commutative ring theory, and gives one of the first general definitions of a commutative ring. Before this paper, most results in commutative algebra were restricted to special examples of commutative rings, such as polynomial rings over fields or rings of algebraic integers. Noether proved that in a ring which satisfies the ascending chain condition on ideals, every ideal is finitely generated. In 1943, French mathematician Claude Chevalley coined the term Noetherian ring to describe this property. A major result in Noether's 1921 paper is the Lasker–Noether theorem, which extends Lasker's theorem on the primary decomposition of ideals of polynomial rings to all Noetherian rings. The Lasker–Noether theorem can be viewed as a generalization of the fundamental theorem of arithmetic which states that any positive integer can be expressed as a product of prime numbers, and that this decomposition is unique.

Noether's work Abstrakter Aufbau der Idealtheorie in algebraischen Zahl- und Funktionenkörpern (Abstract Structure of the Theory of Ideals in Algebraic Number and Function Fields, 1927) characterized the rings in which the ideals have unique factorization into prime ideals as the Dedekind domains: integral domains that are Noetherian, 0 or 1-dimensional, and integrally closed in their quotient fields. This paper also contains what are now called the isomorphism theorems, which describe some fundamental natural isomorphisms, and some other basic results on Noetherian and Artinian modules.

Elimination theory

In 1923–24, Noether applied her ideal theory to elimination theory—in a formulation that she attributed to her student, Kurt Hentzelt—showing that fundamental theorems about the factorization of polynomials could be carried over directly. Traditionally, elimination theory is concerned with eliminating one or more variables from a system of polynomial equations, usually by the method of resultants. For illustration, the system of equations can often be written in the form of a matrix M (missing the variable x) times a vector v (having only different powers of x) equaling the zero vector, M·v = 0. Hence, the determinant of the matrix M must be zero, providing a new equation in which the variable x has been eliminated.

Invariant theory of finite groups

Techniques such as Hilbert's original non-constructive solution to the finite basis problem could not be used to get quantitative information about the invariants of a group action, and furthermore they did not apply to all group actions. In her 1915 paper Noether found a solution to the finite basis problem for a finite group of transformations G acting on a finite dimensional vector space over a field of characteristic zero. Her solution shows that the ring of invariants is generated by homogenous invariants whose degree is less than or equal to the order of the finite group; this is called "Noether's bound". Her paper gave two proofs of Noether's bound, both of which also work when the characteristic of the field is coprime to |G|!, the factorial of the order |G| of the group G. The number of generators need not satisfy Noether's bound when the characteristic of the field divides the |G|, but Noether was not able to determine whether the bound was correct when the characteristic of the field divides |G|! but not |G|. For many years, determining the truth or falsity of the bound in this case was an open problem called "Noether's gap". It was finally resolved independently by Fleischmann in 2000 and Fogarty in 2001, who both showed that the bound remains true.

In her 1926 paper, she extended Hilbert's theorem to representations of a finite group over any field; the new case that did not follow from Hilbert's work is when the characteristic of the field divides the order of the group. Noether's result was later extended by William Haboush to all reductive groups by his proof of the Mumford conjecture. In this paper Noether also introduced the Noether normalization lemma, showing that a finitely generated domain A over a field k has a set x₁, ... , x_n of algebraically independent elements such that A is integral over k[x₁, ... , x_n].

Contributions to topology

A continuous deformation (homotopy) of a coffee cup into a doughnut (torus) and back.

As noted by Pavel Alexandrov and Hermann Weyl in their obituaries, Noether's contributions to topology illustrate her generosity with ideas and how her insights could transform entire fields of mathematics. In topology, mathematicians study the properties of objects that remain invariant even under deformation, properties such as their connectedness. A common joke is that a topologist can't distinguish her donut from her coffee mug, since they can be smoothly deformed into one another.

Noether is credited with the fundamental ideas that led to the development of algebraic topology from the earlier combinatorial topology, specifically the idea of homology groups. According to the account of Alexandrov, Noether attended lectures given by Heinz Hopf and himself in the summers of 1926 and 1927, where "she continually made observations, which were often deep and subtle". He continues

When ... she first became acquainted with a systematic construction of combinatorial topology, she immediately observed that it would be worthwhile to study directly the groups of algebraic complexes and cycles of a given polyhedron and the subgroup of the cycle group consisting of cycles homologous to zero; instead of the usual definition of Betti numbers, she suggested immediately defining the Betti group as the complementary (quotient) group of the group of all cycles by the subgroup of cycles homologous to zero. This observation now seems self-evident. But in those years (1925–1928) this was a completely new point of view.

Noether's suggestion that topology be studied algebraically was adopted immediately by Hopf, Alexandrov, and others, and it became a frequent topic of discussion among the mathematicians of Göttingen. Noether observed that her idea of a Betti group makes the Euler–Poincaré formula simple to understand, and Hopf's own work on this subject "bears the imprint of these remarks of Emmy Noether". Noether herself mentions her topology ideas only as an aside in one 1926 publication, where she cites it as an application of group theory.

The algebraic approach to topology was developed independently in Austria. In a 1926–27 course given in Vienna, Leopold Vietoris defined a homology group, which was developed by Walther Mayer into an axiomatic definition in 1928.

Helmut Hasse worked with Noether and others to found the theory of central simple algebras.

Third epoch (1927–35)

Hypercomplex numbers and representation theory

Much work on hypercomplex numbers and group representations was carried out in the 19th and early 20th centuries, but remained disparate. Noether united the results and gave the first general representation theory of groups and algebras. Briefly, Noether subsumed the structure theory of associative algebras and the representation theory of groups into a single arithmetic theory of modules and ideals in rings satisfying ascending chain conditions. This single work was of fundamental importance for the development of modern algebra.

Noncommutative algebra

Noether was also responsible for a number of other advancements in the field of algebra. With Emil Artin, Richard Brauer, and Helmut Hasse, she founded the theory of central simple algebras.

A seminal paper by Noether, Helmut Hasse, and Richard Brauer pertains to division algebras, which are algebraic systems in which division is possible. They proved two important theorems: A local-global theorem stating that if a finite dimensional central division algebra over a number field splits locally everywhere then it splits globally (so is trivial), and from this deduced their Hauptsatz ("main theorem"): Every finite dimensional central division algebra over an algebraic number field F splits over a cyclic cyclotomic extension. These theorems allow one to classify all finite dimensional central division algebras over a given number field. A subsequent paper by Noether showed, as a special case of a more general theorem, that all maximal subfields of a division algebra D are splitting fields. This paper also contains the Skolem–Noether theorem which states that any two embeddings of an extension of a field k into a finite dimensional central simple algebra over k are conjugate. The Brauer–Noether theorem gives a characterization of the splitting fields of a central division algebra over a field.

Assessment and memorials

The Emmy Noether Campus at the University of Siegen is home to the mathematics and physics departments. Image by Bob Ionescu.

Noether's work continues to be relevant for the development of theoretical physics and mathematics, and she is consistently ranked as one of the greatest mathematicians of the 20th century. In his obituary, fellow algebraist B. L. van der Waerden says that her mathematical originality was "absolute beyond comparison", and Hermann Weyl said that Noether "changed the face of algebra by her work". During her lifetime and even until today, Noether has been characterized as the greatest woman mathematician in recorded history by mathematicians such as Pavel Alexandrov, Hermann Weyl, and Jean Dieudonné. In a letter to The New York Times, Albert Einstein wrote:

In the judgment of the most competent living mathematicians, Fräulein Noether was the most significant creative mathematical genius thus far produced since the higher education of women began. In the realm of algebra, in which the most gifted mathematicians have been busy for centuries, she discovered methods which have proved of enormous importance in the development of the present-day younger generation of mathematicians.

On 2 January 1935, a few months before her death, mathematician Norbert Wiener wrote that

Miss Noether is ... the greatest woman mathematician who has ever lived; and the greatest woman scientist of any sort now living, and a scholar at least on the plane of Madame Curie.

In a 1964 World's Fair exhibit entitled "Men of Modern Mathematics", Noether was the only female represented. Noether has been honored in several memorials. The Association for Women in Mathematics holds a Noether Lecture to honor women in mathematics every year; in its 2005 pamphlet for the event, the Association characterizes Noether as "one of the great mathematicians of her time, someone who worked and struggled for what she loved and believed in. Her life and work remain a tremendous inspiration". Consistent with her dedication to her students, the University of Siegen houses its mathematics and physics buildings on the Emmy Noether Campus. A street in her hometown Erlangen has been named after her and her father, Max Noether; and the successor to the secondary school she attended in Erlangen has been renamed the Emmy Noether School. Further from home, the Nöther crater on the far side of the Moon is named for her, as is the 7001 Noether asteroid.

List of doctoral students

Date	Student name	Dissertation title and English translation	University	Publication
1911.12.16	Falckenberg, Hans	Verzweigungen von Lösungen nichtlinearer Differentialgleichungen Ramifications of Solutions of Nonlinear Differential Equations§	Erlangen	Leipzig 1912
1916.03.04	Seidelmann, Fritz	Die Gesamtheit der kubischen und biquadratischen Gleichungen mit Affekt bei beliebigem Rationalitätsbereich Complete Set of Cubic and Biquadratic Equations with Affect in an Arbitrary Rationality Domain§	Erlangen	Erlangen 1916
1925.02.25	Hermann, Grete	Die Frage der endlich vielen Schritte in der Theorie der Polynomideale unter Benutzung nachgelassener Sätze von Kurt Hentzelt The Question of the Finite Number of Steps in the Theory of Ideals of Polynomials using Theorems of the Late Kurt Hentzelt§	Göttingen	Berlin 1926
1926.07.14	Grell, Heinrich	Beziehungen zwischen den Idealen verschiedener Ringe Relationships between the Ideals of Various Rings§	Göttingen	Berlin 1927
1927	Doräte, Wilhelm	Über einem verallgemeinerten Gruppenbegriff On a Generalized Conceptions of Groups§	Göttingen	Berlin 1927
died before defense	Hölzer, Rudolf	Zur Theorie der primären Ringe On the Theory of Primary Rings§	Göttingen	Berlin 1927
1929.06.12	Weber, Werner	Idealtheoretische Deuting der Darstellbarkeit beliebiger natürlicher Zahlen durch quadratische Formen Ideal-theoretic Interpretation of the Representability of Arbitrary Natural Numbers by Quadratic Forms§	Göttingen	Berlin 1930
1929.06.26	Levitski, Jakob	Über vollständig reduzible Ringe und Unterringe On Completely Reducible Rings and Subrings§	Göttingen	Berlin 1931
1930.06.18	Deuring, Max	Zur arithmetischen Theorie der algebraischen Funktionen On the Arithmetic Theory of Algebraic Functions§	Göttingen	Berlin 1932
1931.07.29	Fitting, Hans	Zur Theorie der Automorphismenringe Abelscher Gruppen und ihr Analogon bei nichtkommutativen Gruppen On the Theory of Automorphism-Rings of Abelian Groups and Their Analogs in Noncommutative Groups§	Göttingen	Berlin 1933
1933.07.27	Witt, Ernst	Riemann-Rochscher Satz und Zeta-Funktion im Hyperkomplexen The Riemann-Roch Theorem and Zeta Function in Hypercomplex Numbers§	Göttingen	Berlin 1934
1933.12.06	Tsen, Chiungtze	Algebren über Funktionenkörper Algebras over Function Fields§	Göttingen	Göttingen 1934
1934	Schilling, Otto	Über gewisse Beziehungen zwischen der Arithmetik hyperkomplexer Zahlsysteme und algebraischer Zahlkörper On Certain Relationships between the Arithmetic of Hypercomplex Number Systems and Algebraic Number Fields§	Marburg	Braunschweig 1935
1935	Stauffer, Ruth	The construction of a normal basis in a separable extension field	Bryn Mawr	Baltimore 1936
1935	Vorbeck, Werner	Nichtgaloissche Zerfällungskörper einfacher Systeme Non-Galois Splitting Fields of Simple Systems§	Göttingen
1936	Wichmann, Wolfgang	Anwendungen der p-adischen Theorie im Nichtkommutativen Algebren Applications of the p-adic Theory in Noncommutative Algebras§	Göttingen	Monatshefte für Mathematik und Physik (1936) 44, 203–224.

Eponymous mathematical topics

• Noetherian
• Noetherian group
• Noetherian ring
• Noetherian module
• Noetherian space

• Noetherian induction
• Noetherian scheme
• Noether normalization lemma
• Noether problem

• Noether's theorem
• Lasker–Noether theorem
• Skolem–Noether theorem
• Brauer–Noether theorem

References

Selected works by Emmy Noether (in German)

Main article: List of publications by Emmy Noether

• Noether, Emmy (1908), "Über die Bildung des Formensystems der ternären biquadratischen Form (On Complete Systems of Invariants for Ternary Biquadratic Forms)", Journal für die reine und angewandte Mathematik, 134: 23–90 and two tables.
• Noether, Emmy (1913), "Rationale Funkionenkörper (Rational Function Fields)", J. Ber. D. DMV, 22: 316–319.
• Noether, Emmy (1915), "Der Endlichkeitssatz der Invarianten endlicher Gruppen (The Finiteness Theorem for Invariants of Finite Groups)", Mathematische Annalen, 77: 89–92, doi:10.1007/BF01456821
• Noether, Emmy (1918), "Gleichungen mit vorgeschriebener Gruppe (Equations with Prescribed Group)", Mathematische Annalen, 78: 221–229, doi:10.1007/BF01457099.
• Noether, Emmy (1918b), "Invariante Variationsprobleme (Invariant Variation Problems)", Nachr. D. König. Gesellsch. D. Wiss. Zu Göttingen, Math-phys. Klasse, 1918: 235–257. English translation by M. A. Tavel (1918), arXiv:physics/0503066.
• Noether, Emmy (1921), "Idealtheorie in Ringbereichen (The Theory of Ideals in Ring Domains)" (PDF), Mathematische Annalen, 83 (1), ISSN 0025-5831.
• Noether, Emmy (1926), "Der Endlichkeitsatz der Invarianten endlicher linearer Gruppen der Charakteristik p (Proof of the Finiteness of the Invariants of Finite Linear Groups of Characteristic p)", Nachr. Ges. Wiss. Göttingen: 28–35.
• Noether, Emmy (1927), "Abstrakter Aufbau der Idealtheorie in algebraischen Zahl- und Funktionenkörpern (Abstract Structure of the Theory of Ideals in Algebraic Number Fields)" (PDF), Mathematische Annalen, 96 (1): 26–61, doi:10.1007/BF01209152, ISSN 0025-5831.
• Brauer, Richard; Noether, Emmy (1927), "Über minimale Zerfällungskörper irreduzibler Darstellungen (On the Minimum Splitting Fields of Irreducible Representations)", Sitz. Ber. D. Preuss. Akad. D. Wiss.: 221–228.
• Noether, Emmy (1929), "Hyperkomplexe Grössen und Darstellungstheorie (Hypercomplex Quantities and the Theory of Representations)", Mathematische Annalen, 30: 641–692, doi:10.1007/BF01187794.
• Brauer, Richard; Hasse, Helmut; Noether, Emmy (1932), "Beweis eines Hauptsatzes in der Theorie der Algebren (Proof of a Main Theorem in the Theory of Algebras)", Journal für Math., 167: 399–404.
• Noether, Emmy (1933), "Nichtkommutative Algebren (Noncommutative Algebras)", Mathematische Zeitschrift, 37: 514–541, doi:10.1007/BF01474591.
• Noether, Emmy (1983), Jacobson, Nathan (ed.), Gesammelte Abhandlungen (Collected papers), Berlin-New York: Springer-Verlag, pp. viii, 777, ISBN 3-540-11504-8, MR0703862.

Additional sources

• Alexandrov, Pavel S. (1981), "In Memory of Emmy Noether", in James W. Brewer and Martha K. Smith (ed.), Emmy Noether: A Tribute to Her Life and Work, New York: Marcel Dekker, Inc., pp. 99–111, ISBN 0-8247-1550-0.
• Blue, Meredith (2001), Galois Theory and Noether's Problem (PDF), Thirty-Fourth Annual Meeting: Florida Section of The Mathematical Association of America.
• Byers, Nina (2006), "Emmy Noether", in Nina Byers and Gary Williams (ed.), Out of the Shadows: Contributions of 20th Century Women to Physics, Cambridge: Cambridge University Press, ISBN 0-5218-2197-5.
• Dick, Auguste (1981), Emmy Noether: 1882–1935, Boston: Birkhäuser, ISBN 3-7643-3019-8. Trans. H.I. Blocher.
• Fleischmann, Peter (2000), "The Noether bound in invariant theory of finite groups", Advances in Mathematics, 156 (1): 23–32, doi:10.1006/aima.2000.1952, ISSN 0001-8708, MR1800251 {{citation}}: |access-date= requires |url= (help); Check date values in: |accessdate= (help)
• Fogarty, John (2001), "On Noether's bound for polynomial invariants of a finite group", Electronic Research Announcements of the American Mathematical Society, 7: 5–7, doi:10.1090/S1079-6762-01-00088-9, ISSN 1079-6762, MR1826990, retrieved 2008/6/16 {{citation}}: Check date values in: |accessdate= (help)
• Gilmer, Robert (1981), "Commutative Ring Theory", in James W. Brewer and Martha K. Smith (ed.), Emmy Noether: A Tribute to Her Life and Work, New York: Marcel Dekker, Inc., pp. 131–143, ISBN 0-8247-1550-0.
• Gordan, Paul (1870), "Die simultanen Systeme binärer Formen", Mathematische Annalen (in German), 2 (2): 227–280, doi:10.1007/BF01444021, ISSN 0025-5831
• Hasse, Helmut (1933), "Die Struktur der R. Brauerschen Algebrenklassengruppe über einem algebraischen Zahlkörper", Mathematische Annalen (in German), 107: 731–760, doi:10.1007/BF01448916. (German)
• Hilbert, David (1890), "Ueber die Theorie der algebraischen Formen", Mathematische Annalen (in German), 36 (4): 473–534, doi:10.1007/BF01208503, ISSN 0025-5831 {{citation}}: Unknown parameter |month= ignored (help).
• Hilton, Peter (1988), "A Brief, Subjective History of Homology and Homotopy Theory in This Century", Mathematics Magazine, 60 (5): 282–291
• Kimberling, Clark (1981), "Emmy Noether and Her Influence", in James W. Brewer and Martha K. Smith (ed.), Emmy Noether: A Tribute to Her Life and Work, New York: Marcel Dekker, Inc., pp. 3–61, ISBN 0-8247-1550-0.
• Lam, Tsit Yuen (1981), "Representation Theory", in James W. Brewer and Martha K. Smith (ed.), Emmy Noether: A Tribute to Her Life and Work, New York: Marcel Dekker, Inc., pp. 145–156, ISBN 0-8247-1550-0.
• Lederman, Leon M.; Hill, Christopher T. (2004), Symmetry and the Beautiful Universe, Amherst: Prometheus Books, ISBN 1-59102-242-8.
• Mac Lane, Saunders (1981), "Mathematics at the University of Göttingen 1831–1933", in James W. Brewer and Martha K. Smith (ed.), Emmy Noether: A Tribute to Her Life and Work, New York: Marcel Dekker, Inc., pp. 65–78, ISBN 0-8247-1550-0.
• Noether, Max (1914), "Paul Gordan", Mathematische Annalen, 75 (1): 1–41, doi:10.1007/BF01564521.
• Osen, Lynn M. (1974), "Emmy (Amalie) Noether", Women in Mathematics, MIT Press, pp. 141–152, ISBN 0-262-15014-X.
• Schmadel, Lutz D. (2003), Dictionary of Minor Planet Names (5th revised and enlarged ed.), Berlin: Springer-Verlag, ISBN 3-540-00238-3.
• Swan, Richard G. (1969), "Invariant rational functions and a problem of Steenrod", Inventiones Mathematicae, 7: 148–158, doi:10.1007/BF01389798.
• Taussky, Olga (1981), "My Personal Recollections of Emmy Noether", in James W. Brewer and Martha K. Smith (ed.), Emmy Noether: A Tribute to Her Life and Work, New York: Marcel Dekker, Inc., pp. 79–92, ISBN 0-8247-1550-0.
• van der Waerden, B.L. (1935), "Nachruf auf Emmy Noether (Obituary of Emmy Noether)", Mathematische Annalen, 111: 469–474, doi:10.1007/BF01472233. Reprinted in Dick 1981. (German)
• van der Waerden, B.L. (1985), A History of Algebra: from al-Khwārizmī to Emmy Noether, Berlin: Springer-Verlag, ISBN 0-387-13610-X.
• Weyl, Hermann (1944), "David Hilbert and his mathematical work", Bulletin of the American Mathematical Society, 50: 612–654, doi:10.1090/S0002-9904-1944-08178-0, ISSN 0002-9904, MR0011274.

External links

• "Invariante Variationsprobleme", Nachr. v. d. Ges. d. Wiss. zu Göttingen Original paper in German with link to English translation.
• "Emmy Noether" in CWP at UCLA
• Emmy Noether at the Mathematics Genealogy Project
• "Emmy Noether", Biographies of Women Mathematicians, Agnes Scott College
• O'Connor, John J.; Robertson, Edmund F., "Emmy Noether", MacTutor History of Mathematics Archive, University of St Andrews
• Lebensläufe Template:De icon Noether's application for admission to the University of Erlangen and three curricula vitae, two of which are shown in handwriting, with transcriptions. The first of these is in Emmy Noether's own handwriting.
• Unpublished and published versions Template:De icon of Noether's 1908 doctoral dissertation completed at Erlangen.
• Emmy Noether, Mentors & Colleagues (photo by Clark Kimberling)
• Oberwolfach collection of photos of Noether
• Correspondence between Noether and Helmut Hasse, 1925–35