Valentin Alexandre Poénaru (born 1932 in

Bucharest Bucharest ( , ; ) is the capital and largest city of Romania. The metropolis stands on the River Dâmbovița (river), Dâmbovița in south-eastern Romania. Its population is officially estimated at 1.76 million residents within a greater Buc ...

) is a

Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...

n– French

mathematician A mathematician is someone who uses an extensive knowledge of mathematics in their work, typically to solve mathematical problems. Mathematicians are concerned with numbers, data, quantity, mathematical structure, structure, space, Mathematica ...

. He was a Professor of Mathematics at

University of Paris-Sud Paris-Sud University (), also known as the University of Paris — XI (or as the Orsay Faculty of Sciences, University of Paris before 1971), was a French research university distributed among several campuses in the southern suburbs of Paris, ...

, specializing in

low-dimensional topology In mathematics, low-dimensional topology is the branch of topology that studies manifolds, or more generally topological spaces, of four or fewer dimensions. Representative topics are the theory of 3-manifolds and 4-manifolds, knot theory, ...

Life and career

Born in

, he did his undergraduate studies at the

University of Bucharest The University of Bucharest (UB) () is a public university, public research university in Bucharest, Romania. It was founded in its current form on by a decree of Prince Alexandru Ioan Cuza to convert the former Princely Academy of Bucharest, P ...

. In 1962, he was an invited speaker at the

International Congress of Mathematicians The International Congress of Mathematicians (ICM) is the largest conference for the topic of mathematics. It meets once every four years, hosted by the International Mathematical Union (IMU). The Fields Medals, the IMU Abacus Medal (known before ...

Stockholm Stockholm (; ) is the Capital city, capital and List of urban areas in Sweden by population, most populous city of Sweden, as well as the List of urban areas in the Nordic countries, largest urban area in the Nordic countries. Approximately ...

Sweden Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic count ...

. While at the congress, Poénaru

defected In politics, a defector is a person who gives up allegiance to one state in exchange for allegiance to another, changing sides in a way which is considered illegitimate by the first state. More broadly, defection involves abandoning a person, ca ...

, subsequently leaving for

France France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...

. He arrived in mid-September 1962 at the

Institut des Hautes Études Scientifiques The Institut des hautes études scientifiques (IHÉS; English: Institute of Advanced Scientific Studies) is a French research institute supporting advanced research in mathematics and theoretical physics (also with a small theoretical biology g ...

Bures-sur-Yvette Bures-sur-Yvette (, "Bures-on- Yvette") is a commune in the Essonne department in the Île-de-France region in Northern France. It is a southern Parisian outer suburb in the Vallée de Chevreuse, with a population of 9,254 as of 2021. Geograp ...

; the IHÉS decided to support him, and he has remained associated with the institute ever since then. Poénaru defended his Thèse d'État at the

University of Paris The University of Paris (), known Metonymy, metonymically as the Sorbonne (), was the leading university in Paris, France, from 1150 to 1970, except for 1793–1806 during the French Revolution. Emerging around 1150 as a corporation associated wit ...

on March 23, 1963. His dissertation topic was ''Sur les variétés tridimensionnelles ayant le type d'homotopie de la sphère S₃'', and was written under the supervision of

Charles Ehresmann Charles Ehresmann (19 April 1905 – 22 September 1979) was a German-born French mathematician who worked in differential topology and category theory. He was an early member of the Bourbaki group, and is known for his work on the differentia ...

. After that, he went to the

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

, spending four years at

Harvard University Harvard University is a Private university, private Ivy League research university in Cambridge, Massachusetts, United States. Founded in 1636 and named for its first benefactor, the History of the Puritans in North America, Puritan clergyma ...

and

Princeton University Princeton University is a private university, private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial ...

. In 1967, he returned to France. Poénaru has worked for several decades on a proof of the

Poincaré conjecture In the mathematical field of geometric topology, the Poincaré conjecture (, , ) is a theorem about the characterization of the 3-sphere, which is the hypersphere that bounds the unit ball in four-dimensional space. Originally conjectured b ...

, making a number of related breakthroughs. His first attempt at proving the conjecture dates from 1957. He has described his general approach over the years in different papers and conferences. On December 19, 2006, he posted a preprint to the

arXiv arXiv (pronounced as "archive"—the X represents the Chi (letter), Greek letter chi ⟨χ⟩) is an open-access repository of electronic preprints and postprints (known as e-prints) approved for posting after moderation, but not Scholarly pee ...

, claiming to have finally completed the details of his approach and proven the conjecture. His doctoral students include

Jean Lannes Jean Lannes, 1st Duke of Montebello, Prince of Siewierz (; 10 April 1769 – 31 May 1809), was a French military commander and a Marshal of the Empire who served during both the French Revolutionary and Napoleonic Wars. He was one of Napol ...

Works

*Valentin Poenaru, Memories from my former life: the making of a mathematician. In: Geometry in history (ed. S. G. Dani and A. Papadopoulos), 705–732, Springer, Cham, 2019. *Valentin Poenaru, ''On the 3-Dimensional Poincaré Conjecture and the 4-Dimensional Smooth Schoenflies Problem'', . * Valentin Poenaru
''Sur les variétés tridimensionnelles ayant le type d'homotopie de la sphère S₃''
Séminaire Ehresmann, Topologie et géométrie différentielle 6 (1964), Exposé No. 1, 1–67. * Valentin Poenaru, ''Produits cartésiens de variétés différentielles par un disque'', 1963 Proceedings of the

(Stockholm, 1962), pp. 481–489, Mittag-Leffler Institute, Djursholm. MR0176481. *

André Haefliger André Haefliger (; 22 May 19297 March 2023) was a Swiss mathematician who worked primarily on topology. Education and career Haefliger went to school in Nyon and then attended his final years at Collège Calvin, Collège de Genève in Genev ...

and Valentin Poenaru
''La classification des immersions combinatoires''

Publications Mathématiques de l'IHÉS ''Publications Mathématiques de l'IHÉS'' is a peer-reviewed mathematical journal. It is published by Springer Science+Business Media on behalf of the Institut des Hautes Études Scientifiques, with the help of the Centre National de la Recher ...

23 (1964), 75–91.

Iconography

His friend the Peruvian painter

Herman Braun-Vega Herman Braun-Vega (7 July 1933 in Lima — 2 April 2019 in Paris) was a Peruvian painter and artist. Although his work has always been figurative, it was at first (before 1970) close to abstraction. It experienced a decisive turning point when t ...

made of him a family portrait with his wife the painter Rigmor Poenaru, where figures and mathematical symbols in the form of graffiti evoke his research works.The Poenaru family
acrylic on wood, 1981-1982, by Herman Braun-Vega

References

David Gabai David Gabai is an American mathematician and the Princeton University Department of Mathematics, Hughes-Rogers Professor of Mathematics at Princeton University. His research focuses on low-dimensional topology and hyperbolic geometry. Biography ...

, ''Valentin Poenaru's program for the Poincaré conjecture.'' Geometry, topology, & physics, 139–166, Conf. Proc. Lecture Notes Geom. Topology, IV, Int. Press, Cambridge, MA, 1995.

External links

*
''Terza e quarta dimensione: un mistero da svelare''
interview by Marinella Daidone from Università degli Studi di Trento, Unitn, no. 52, April, 2003. {{DEFAULTSORT:Poenaru, Valentin Living people 20th-century Romanian people 20th-century French mathematicians 21st-century French mathematicians 20th-century Romanian mathematicians Topologists Romanian exiles Romanian expatriates in France Romanian defectors University of Bucharest alumni University of Paris alumni 1932 births Scientists from Bucharest Princeton University faculty Harvard University Department of Mathematics faculty 21st-century Romanian mathematicians

Life and career

Works

Iconography

See also

References

External links