Pablo Halmos

Paul Richard Halmos ( en húngaro : Halmos Pál [ ˈhɒlmoʃ paːl ] ; 3 de marzo de 1916 – 2 de octubre de 2006) fue un matemático y probabilista estadounidense de origen húngaro que realizó avances fundamentales en las áreas de lógica matemática , teoría de la probabilidad , teoría de operadores , teoría ergódica y análisis funcional (en particular, espacios de Hilbert ). También fue reconocido como un gran divulgador matemático. Se le ha descrito como uno de los «marcianos» . ^{[ 1 ]}

Nacido en el Reino de Hungría en el seno de una familia judía , Halmos emigró a los Estados Unidos a los 13 años. Asistió a la escuela secundaria Robert A. Waller en Lincoln Park, Chicago, donde se matriculó en 1929 y se graduó en 1931. Obtuvo su licenciatura en la Universidad de Illinois , especializándose en matemáticas y cumpliendo también los requisitos para obtener un título en filosofía. Obtuvo el título en tan solo tres años y tenía 19 años cuando se graduó. Luego comenzó un doctorado en filosofía, todavía en el campus de Champaign-Urbana . Sin embargo, después de reprobar sus exámenes orales de maestría, ^{[ 2 ]} cambió a matemáticas y se graduó en 1938. Joseph L. Doob supervisó su disertación, titulada Invariantes de ciertas transformaciones estocásticas: la teoría matemática de los sistemas de juego . ^{[ 3 ]}

Poco después de graduarse, Halmos se marchó al Instituto de Estudios Avanzados , sin trabajo ni beca. Seis meses más tarde, trabajaba con John von Neumann , una experiencia que resultó decisiva. Durante su estancia en el Instituto, Halmos escribió su primer libro, Espacios vectoriales de dimensión finita , que inmediatamente consolidó su reputación como un excelente divulgador de las matemáticas. ^{[ 4 ]}

Entre 1967 y 1968 fue profesor titular de Matemáticas en el Trinity College de Dublín ( Cátedra Donegall) .

Halmos taught at Syracuse University, the University of Chicago (1946–60), the University of Michigan (~1961–67), the University of Hawaiʻi (1967–68), Indiana University (1969–85), and the University of California at Santa Barbara (1976–78). From his 1985 retirement from Indiana until his death, he was affiliated with the Mathematics department at Santa Clara University (1985–2006).

In a series of papers reprinted in his 1962 Algebraic Logic, Halmos devised polyadic algebras, an algebraic version of first-order logic differing from the better known cylindric algebras of Alfred Tarski and his students. An elementary version of polyadic algebra is described in monadic Boolean algebra.

In addition to his original contributions to mathematics, Halmos was an unusually clear and engaging expositor of university mathematics. He won the Lester R. Ford Award in 1971^[5] and again in 1977 (shared with W. P. Ziemer, W. H. Wheeler, S. H. Moolgavkar, J. H. Ewing and W. H. Gustafson).^[6] Halmos chaired the American Mathematical Society committee that wrote the AMS style guide for academic mathematics, published in 1973. In 1983, he received the AMS's Leroy P. Steele Prize for exposition.

In an article in the American Scientist, Halmos argued that mathematics is a creative art, and that mathematicians should be seen as artists, not number crunchers.^[7] He discussed the division of the field into mathology and mathophysics, further arguing that mathematicians and painters think and work in related ways.

Halmos's 1985 "automathography" I Want to Be a Mathematician is an account of what it was like to be an academic mathematician in 20th century America. He called the book "automathography" rather than "autobiography", because its focus is almost entirely on his life as a mathematician, not his personal life. The book contains the following quote on Halmos' view of what doing mathematics means:

Don't just read it; fight it! Ask your own questions, look for your own examples, discover your own proofs. Is the hypothesis necessary? Is the converse true? What happens in the classical special case? What about the degenerate cases? Where does the proof use the hypothesis?^[8]

In these memoirs, Halmos claims to have invented the "iff" notation for the words "if and only if" and to have been the first to use the "tombstone" notation to signify the end of a proof,^[10] and this is generally agreed to be the case. The tombstone symbol ∎ (Unicode U+220E) is sometimes called a halmos.^[11]

In 1994, Halmos received the Deborah and Franklin Haimo Award for Distinguished College or University Teaching of Mathematics.^[12]

In 2005, Halmos and his wife Virginia Halmos funded the Euler Book Prize, an annual award given by the Mathematical Association of America for a book that is likely to improve the view of mathematics among the public. The first prize was given in 2007, the 300th anniversary of Leonhard Euler's birth, to John Derbyshire for his book about Bernhard Riemann and the Riemann hypothesis: Prime Obsession.^[13]

In 2009 George Csicsery featured Halmos in a documentary film also called I Want to Be a Mathematician.^[14]

Books by Halmos have led to so many reviews that lists have been assembled.^[15][16]

• 1942. Finite-Dimensional Vector Spaces. Springer-Verlag.^[17]
• 1950. Measure Theory. Springer Verlag.^[18]
• 1951. Introduction to Hilbert Space and the Theory of Spectral Multiplicity. Chelsea.^[19]
• 1956. Lectures on Ergodic Theory. Chelsea.^[20]
• 1960. Naive Set Theory. Springer Verlag.
• 1962. Algebraic Logic. Chelsea.
• 1963. Lectures on Boolean Algebras. Van Nostrand.
• 1967. A Hilbert Space Problem Book. Springer-Verlag.
• 1973. (with Norman E. Steenrod, Menahem M. Schiffer, and Jean A. Dieudonné). How to Write Mathematics. American Mathematical Society. ISBN 978-0-8218-0055-3
• 1978. (with V. S. Sunder). Bounded Integral Operators on L² Spaces. Springer Verlag ISBN 978-3540088943^[21]
• 1985. I Want to Be a Mathematician. Springer-Verlag. ISBN 978-0387960784
• 1987. I Have a Photographic Memory. Mathematical Association of America. ISBN 978-0821819395
• 1991. Problems for Mathematicians, Young and Old, Dolciani Mathematical Expositions, Mathematical Association of America. ISBN 978-0883853207
• 1996. Linear Algebra Problem Book, Dolciani Mathematical Expositions, Mathematical Association of America. ISBN 978-0883853221
• 1998. (with Steven Givant). Logic as Algebra, Dolciani Mathematical Expositions No. 21, Mathematical Association of America.ISBN 978-1470451134^[22]
• 2009. (posthumous, with Steven Givant), Introduction to Boolean Algebras. ISBN 978-1-4419-2324-0^[23] Springer.

• Crinkled arc
• Commutator subspace
• Invariant subspace problem
• Naive set theory
• Criticism of non-standard analysis
• The Martians (scientists)

• J. H. Ewing; F. W. Gehring (1991). Paul Halmos: Celebrating 50 Years of Mathematics. Springer-Verlag. ISBN 0-387-97509-8. OCLC 22859036. Includes a bibliography of Halmos's writings through 1991.
• John Ewing (October 2007). "Paul Halmos: In His Own Words"(PDF). Notices of the American Mathematical Society. 54 (9): 1136–1144. Retrieved 15 January 2008.
• Paul R. Halmos (1985). I want to Be a Mathematician: An Automathography. Springer-Verlag. ISBN 0-387-96470-3. OCLC 230812318.
• Paul R. Halmos (1970). "How to Write Mathematics"(PDF). L'Enseignement mathématique. 16 (2): 123–152.

• O'Connor, John J.; Robertson, Edmund F., "Paul Halmos", MacTutor History of Mathematics Archive, University of St Andrews
• "Paul Halmos: A Life in Mathematics", Mathematical Association of America (MAA)
• Finite-Dimensional Vector Spaces
• "Examples of Operators" a series of video lectures on operators in Hilbert Space given by Paul Halmos during his 2-week stay in Australia, Briscoe Center Digital Collections