Alexander_Grothendieck

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'''Alexander Grothendieck''' (born [[March 28]], [[1928]] in [[Berlin]], [[Germany]]) is considered to be one of the greatest [[mathematician]]s of the 20th century. He made major contributions to [[algebraic geometry]], [[homological algebra]], and [[functional analysis]]. He was awarded the [[Fields Medal]] in 1966, and was co-awarded the [[Crafoord Prize]] with [[Pierre Deligne]] in 1988. He declined the latter prize on ethical grounds in an open letter to the media.

He is noted for his mastery of abstract approaches to mathematics, and his perfectionism in matters of formulation and presentation. In particular, he demonstrated the ability to derive concrete results using only very general methods.<ref>See, for example, Deligne (1998).</ref> Relatively little of his work after 1960 was published by the conventional route of the [[learned journal]], circulating initially in duplicated volumes of seminar notes; his influence was to a considerable extent personal, on French mathematics and the [[Oscar Zariski|Zariski]] school at [[Harvard University]]. He is the subject of many stories and some misleading rumors concerning his work habits and politics, his confrontations with other mathematicians and the French authorities, his withdrawal from mathematics at age 42, his retirement, and his subsequent lengthy writings.

== Mathematical achievements ==
Homological methods and [[sheaf (mathematics)|sheaf]] theory had already been introduced in algebraic geometry by [[Jean-Pierre Serre]] and others, after sheaves had been invented by [[Jean Leray]]. Grothendieck took them to a higher level of abstraction and turned them into the key organising principle of his theory. He thereby changed the tools and the level of abstraction in algebraic geometry.

Amongst his insights, he shifted attention from the study of individual varieties to the ''[[Grothendieck's relative point of view|relative point of view]]'' (pairs of varieties related by a [[morphism]]), allowing a broad generalization of many classical theorems. This he applied first to the [[Riemann–Roch theorem]], around 1956, which had already recently been generalized to any dimension by [[Friedrich Hirzebruch|Hirzebruch]]. The [[Grothendieck–Riemann–Roch theorem]] was announced by Grothendieck at the initial [[Mathematische Arbeitstagung]] in [[Bonn]], in 1957. It appeared in print in a paper written by [[Armand Borel]] with Serre.

His foundational work on [[algebraic geometry]] is at a higher level of abstraction than all prior versions. He adapted the use of non-closed [[generic point]]s, which led to the theory of [[scheme (mathematics)|schemes]]. He also pioneered the systematic use of [[nilpotent]]s. As 'functions' these can take only the value 0, but they carry infinitesimal information, in purely algebraic settings. His ''theory of schemes'' has become established as the best universal foundation for this major field, because of its great expressive power as well as technical depth. In that setting one can use [[birational geometry]], techniques from [[number theory]], [[Galois theory]] and [[commutative algebra]], and close analogues of the methods of [[algebraic topology]], all in an integrated way.

Its influence spilled over into many other branches of mathematics, for example the contemporary theory of [[D-module]]s. (It also provoked adverse reactions, with many mathematicians seeking out more concrete areas and problems. Grothendieck is one of the few mathematicians who matches the French concept of [[maître à penser]]; some go further and call him [[maître-penseur]].)

==EGA and SGA==

The bulk of Grothendieck's published work is collected in the monumental, and yet incomplete, ''[[Éléments de géométrie algébrique]]'' (EGA) and ''[[Séminaire de géométrie algébrique]]'' (SGA). The collection ''[[Fondements de la Géometrie Algébrique]]'' (FGA), which gathers together talks given in the [[Séminaire Bourbaki]], also contains important material.

Perhaps Grothendieck's deepest single accomplishment is the invention of the [[étale cohomology|étale]] and l-adic cohomology theories, which explain an observation of [[André Weil]]'s that there is a deep connection between the topological characteristics of a variety and its diophantine (number theoretic) properties. For example, the number of solutions of an equation over a [[finite field]] reflects the topological nature of its solutions over the [[complex number]]s. Weil realized that to prove such a connection one needed a new cohomology theory, but neither he nor any other expert saw how to do this until such a theory was found by Grothendieck.

This program culminated in the proofs of the [[Weil conjectures]] by Grothendieck's student [[Pierre Deligne]] in the early 1970s after Grothendieck had largely withdrawn from mathematics.

=== Major mathematical topics (from [[Récoltes et Semailles]]) ===

He wrote a retrospective assessment of his mathematical work (see the external link ''La Vision'' below). As his main mathematical achievements ("maître-thèmes"), he chose this collection of 12 topics (his chronological order):

#[[Topological tensor product]]s and [[nuclear space]]s
#"Continuous" and "discrete" [[duality]] ([[derived category|derived categories]] and "[[six operations (mathematics)|six operations]]").
#''Yoga'' of the [[Grothendieck–Riemann–Roch theorem]] ([[K-theory]], relation with [[intersection theory]]).
#[[Scheme (mathematics)|Scheme]]s.
#[[topos|Topoi]].
#[[Étale cohomology]] including [[l-adic cohomology]].
#[[Motive (mathematics)|Motive]]s and the [[motivic Galois group]] (and [[Grothendieck category|Grothendieck categories]])
#[[Crystal (mathematics)|Crystal]]s and [[crystalline cohomology]], ''yoga'' of De Rham and Hodge coefficients.
#Topological algebra, infinity-stacks, 'dérivateurs', cohomological formalism of toposes as an inspiration for a new [[homotopic algebra]]
#[[Tame topology]].
#''Yoga'' of [[anabelian geometry]] and [[Galois–Teichmüller theory]].
#Schematic point of view, or "arithmetics" for [[regular polyhedron|regular polyhedra]] and [[regular configurations]] of all sorts.

He wrote that the central theme of the topics above is that of [[topos]] theory, while the first and last were of the least importance to him.

Here the term ''yoga'' denotes a kind of "meta-theory" that can be used heuristically.{{huh}} The word ''yoke'', meaning "linkage", is derived from the same Indo-European root.

== Life ==
=== Family and early life ===

Born to a [[Russians|Russian]] [[Jew]]ish father, Alexander Shapiro, and a [[Germany|German]] mother<ref>There are incompatibilities in the various accounts of his origins; see Jackson (2004:1), Cartier (1998, 2001) and [http://www.jinfo.org/Fields_Mathematics.html]; Hanka's ethnic origin is uncertain.</ref>, Hanka Grothendieck, in [[Berlin]]. He was a [[displaced person]] during much of his childhood due to the upheavals of [[World War II]].

Alexander lived with his parents both of whom were [[anarchist]]s, until 1933, in [[Berlin]]. At the end of that year, Shapiro moved to [[Paris]], and Hanka followed him the next year. They left Alexander with a family in [[Hamburg]] where he went to school. During this time, his parents fought in the [[Spanish Civil War]].

===During WWII===

In 1939 Alexander came to France and lived in various camps for displaced persons with his mother, first at the [[Camp de Rieucros]], spending 1942–44 at [[Le Chambon-sur-Lignon]]. His father was sent via [[Drancy]] to [[Auschwitz concentration camp|Auschwitz]] where he died in 1942.

===Studies and contact with research mathematics===

After the war, young Grothendieck studied mathematics in [[France]], initially at the [[University of Montpellier]]. He had decided to become a math teacher because he had been told that mathematical research had been completed early in the 20th century and there were no more open problems.<ref>See Jackson (2004:1). The remark is from the beginning of Récoltes et Semailles (page P4, in the introductory section Prélude en quatre Mouvements)</ref> However, his talent was noticed, and he was encouraged to go to [[Paris]] in 1948.

Initially, Grothendieck attended Henri Cartan's Seminar at [[École Normale Superieure]], but lacking the necessary background to follow the high-powered seminar, he moved to the [[University of Nancy]] where he wrote his dissertation under [[Laurent Schwartz]] in functional analysis, from 1950 to 1953. At this time he was a leading expert in the theory of [[topological vector space]]s. By 1957, he set this subject aside in order to work in algebraic geometry and [[homological algebra]].

===The IHES years===

Installed at the [[Institut des Hautes Études Scientifiques]] (IHES), Grothendieck attracted attention, first by his spectacular [[Grothendieck-Riemann-Roch theorem]], and then by an intense and highly productive activity of seminars (''de facto'' working groups drafting into foundational work some of the ablest French and other mathematicians of the younger generation). Grothendieck himself practically ceased publication of papers through the conventional, [[learned journal]] route. He was, however, able to play a dominant role in mathematics for around a decade, gathering a strong school.

During this time he had officially as students [[Michel Demazure]] (who worked on SGA3, on [[group scheme]]s), [[Luc Illusie]] ([[cotangent complex]]), [[Michel Raynaud]], [[Jean-Louis Verdier]] (cofounder of the [[derived category]] theory) and [[Pierre Deligne]]. Collaborators on the SGA projects also included [[Mike Artin]] ([[étale cohomology]]) and [[Nick Katz]] ([[monodromy theory]] and [[Lefschetz pencil]]s). [[Jean Giraud (mathematician)|Jean Giraud]] worked out [[torsor]] theory extensions of [[non-abelian cohomology]]. Many others were involved.

=== Politics and retreat from scientific community ===

Grothendieck's political views were radical left-wing and pacifist. He gave lectures on [[category theory]] in the forests surrounding [[Hanoi]] while the city was being bombed, to protest against the [[Vietnam War]].{{Fact|date=September 2007}} He retired from scientific life around 1970, after having discovered the partly military funding of [[IHES]] (see pp. xii and xiii of SGA1, Springer Lecture Notes 224). He returned to academia a few years later as a professor at the University of [[Montpellier]], where he stayed until his retirement in 1988. His criticisms of the scientific community are also contained in a [http://web.archive.org/web/20060106062005/http://www.math.columbia.edu/~lipyan/CrafoordPrize.pdf letter], written in 1988, in which he states the reasons for his refusal of the [[Crafoord Prize]].


=== Manuscripts written in the 1980s ===

While not publishing mathematical research in conventional ways during the 1980s, he produced several influential manuscripts with limited distribution, with both mathematical and biographical content. During that period he also released his work on Bertini type theorems contained in EGA 5, published by the [http://www.math.jussieu.fr/~leila/grothendieckcircle/index.php Grothendieck Circle] in 2004.

''[[La Longue Marche à travers la théorie de Galois]]'' (roughly ''The Long Walk Through Galois Theory'') is an approximately 1600-page handwritten manuscript produced by Grothendieck during the years 1980-1981, containing many of the ideas leading to the ''[[Esquisse d'un programme]]'' (see below) and in particular studying the Teichmüller theory.

In 1983 he wrote a huge extended manuscript (about 600 pages) entitled ''[[Pursuing Stacks]]'', stimulated by correspondence with [http://www.bangor.ac.uk/r.brown Ronnie Brown] and [http://www.informatics.bangor.ac.uk/~tporter/ Tim Porter] at [[University of Bangor|Bangor]], and starting with a letter addressed to [[Daniel Quillen]]. This letter and successive parts were distributed from Bangor (see External Links below): in an informal manner, as a kind of diary, Grothendieck explained and developed his ideas on the relationship between [[algebraic homotopy theory]] and [[algebraic geometry]] and prospects for a noncommutative theory of [[Stack (descent theory)|stacks]]. The manuscript, which is being edited for publication by G. Maltsiniotis, later led to another of his monumental works, ''[[Les Dérivateurs]]''. Written in 1991, this latter opus of about 2000 pages further developed the homotopical ideas begun in ''[[Pursuing Stacks]]''. Much of this work anticipated the subsequent development of the motivic homotopy theory of [[F. Morel]] and [[V. Voevodsky]] in the mid 1990s.

His ''[[Esquisse d'un programme]]'' (1984) is a proposal for a position at the [[Centre National de la Recherche Scientifique]], which he held from 1984 to his retirement in 1988. Ideas from it have proved influential, and have been developed by others, in particular [[dessin d'enfant|dessins d'enfants]] and a new field emerging as [[anabelian geometry]]. In ''[[La Clef des Songes]]'' he explains how the reality of [[dream]]s convinced him of [[God]]'s existence.

The 1000-page autobiographical manuscript ''[[Récoltes et semailles]]'' (1986) is now available on the internet in the French original, and an English translation is underway (these parts of Récoltes et semailles have already been [http://www.mccme.ru/free-books/grothendieck/RS.html translated into Russian] and published in Moscow).

=== Disappearance ===

In 1991, he left his home and disappeared. He is now said to live in southern France or [[Andorra]] and to entertain no visitors. Though he has been inactive in mathematics for many years, he remains one of the greatest and most influential mathematicians of modern times.

==See also==
*[[Grothendieck's Galois theory]]
*[[Grothendieck group]]
*[[Grothendieck's relative point of view]]
*[[Grothendieck-Riemann-Roch theorem]]
*[[Grothendieck's Séminaire de géométrie algébrique]]
*[[Grothendieck topology]]
*[[Grothendieck universe]]
*[[Grothendieck inequality]] or [[Grothendieck constant]]
*[[Tarski-Grothendieck set theory]]

== Notes==
<references />

==References==
* {{Citation
| first = Pierre
| last = Cartier
| author-link =
| first2 =
| last2 =
| author2-link =
| editor-last =
| editor-first =
| editor2-last =
| editor2-first =
| contribution = La Folle Journée, de Grothendieck à Connes et Kontsevich — Évolution des Notions d'Espace et de Symétrie
| contribution-url =
| title = Les Relatons entre les Mathématiques et la Physique Théorique — Festschrift for the 40th anniversary of the IHÉS
| year = 1998
| pages = 11–19
| place =
| publisher = Institut des Hautes Études Scientifiques
| url =
| doi =
| id = }}
* {{Citation
| last = Cartier
| first = Pierre
| author-link =
| last2 =
| first2 =
| author2-link =
| title = A mad day's work: from Grothendieck to Connes and Kontsevich The evolution of concepts of space and symmetry
| journal = Bull. Amer. Math. Soc.
| volume = 38
| issue = 4
| pages = 389–408
| date = 2001
| year =
| url = http://www.ams.org/bull/2001-38-04/S0273-0979-01-00913-2/S0273-0979-01-00913-2.pdf
| doi =
| id = }}. An English translation of Cartier (1998)
* {{Citation
| first = Pierre
| last = Deligne
| author-link =
| first2 =
| last2 =
| author2-link =
| editor-last =
| editor-first =
| editor2-last =
| editor2-first =
| contribution = Quelques idées maîtresses de l'œuvre de A. Grothendieck
| contribution-url = http://smf.emath.fr/Publications/SeminairesCongres/1998/3/pdf/smf_sem-cong_3_11-19.pdf
| title = Matériaux pour l'histoire des mathématiques au XXe siècle - Actes du colloque à la mémoire de Jean Dieudonné (Nice 1996)
| year = 1998
| pages = 11–19
| place =
| publisher = Société Mathématique de France
| url =
| doi =
| id = }}
*{{Citation
| last =Jackson
| first =Allyn
| author-link =
| last2 =
| first2 =
| author2-link =
| title = Comme Appelé du Néant — As If Summoned from the Void: The Life of Alexandre Grothendieck I
| journal = Notices of the American Mathematical Society
| volume = 51
| issue = 9
| pages = 1038–1056
| date = 2004
| year =
| url = http://www.ams.org/notices/200409/fea-grothendieck-part1.pdf
| doi =
| id = }}
*{{Citation
| last =Jackson
| first =Allyn
| author-link =
| last2 =
| first2 =
| author2-link =
| title = Comme Appelé du Néant — As If Summoned from the Void: The Life of Alexandre Grothendieck II
| journal = Notices of the American Mathematical Society
| volume = 51
| issue = 10
| pages = 1196–1212
| date = 2004
| year =
| url = http://www.ams.org/notices/200410/fea-grothendieck-part2.pdf
| doi =
| id = }}

== External links ==

* {{MacTutor Biography|id=Grothendieck}}
* {{MathGenealogy|id=31245}}
*[http://www.math.jussieu.fr/~leila/grothendieckcircle/index.php Grothendieck Circle], collection of mathematical and biographical information, photos, links to his writings
**[http://gavrilov.akatov.com/Grothendieck Grothendieck Circle discussion Forum]
*[http://www.ihes.fr Institut des Hautes Études Scientifiques]
*[http://www.bangor.ac.uk/r.brown/pstacks.htm The origins of `Pursuing Stacks'] This is an account of how `Pursuing Stacks' was written in response to a correspondence in English with Ronnie Brown and Tim Porter at Bangor, which continued until 1991.
*[http://acm.math.spbu.ru/RS/ Récoltes et Semailles] in French.

{{Fields medalists}}


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