Dennis Johnson (mathematician)

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Dennis Lee Johnson (born November 19, 1938 in Los Angeles , † December 20, 2018 in Morgan Hill , California ) was an American mathematician who studied algebraic topology and geometric topology . He was also a composer and a pioneer of minimal music .

Career

Johnson studied music at the University of California, Los Angeles (UCLA) in 1959 . La Monte Young and Terry Jennings were fellow students at the time. He received his PhD in 1968 from the University of California, Los Angeles (UCLA) with Nathaniel Grossmann ( The homology of locally finite CW complexes ). As a post-doctoral student , he was at the Institute for Advanced Study until 1970 . He then worked at Caltech in space research (Mars robots and others).

In the early 1980s he published a fundamental paper on the structure of Torelli groups , special subgroups of mapping class groups of surfaces. In the 1980s he was back at UCLA. He later lived in Kensington, California .

He published with Joan Birman , among others .

Johnson also looked at nodal groups and hyperbolic manifolds .

He was also a pianist and composer. His solo composition November 1959 was one of the earliest pieces of minimal music and the inspiration for The Well Tuned Piano (1964) by La Monte Young . The musicologist Kyle Gann tried to reconstruct the several hours long composition, of which only a tape recording with Johnson himself at the piano, which ended abruptly after around 100 minutes, has been preserved. The cassette was of poor quality and was distorted with background noise. Gann succeeded in transcribing it in 1992 with the help of a partial score that Johnson made in the 1980s. According to Johnson, the composition emerged as the fruit of a practice lesson on Jennings' grand piano and was further developed in the UCLA practice rooms (interview with Clive Bell). A recording with pianist R. Andrew Lee was released by Penultimate Press in 2013. It required improvisations in addition to Gann's score. Another piece by Johnson is The Second Machine . In 1966 he gave up composition and turned to mathematics. But he continued to play the piano in the 1980s and 1990s, mainly improvising.

He was a passionate rock climber and kayaker.

Fonts

  • A survey of the Torelli Group , in Low dimensional Topology (San Francisco 1981), Contemporary Mathematics, Volume 20, 1983, American Mathematical Society, pp. 165-179
  • An abelian quotient of the mapping class group Tg , Mathematische Annalen, Volume 249, 1980, pp. 225-242
  • Conjugacy relations in subgroups of the mapping class group and a group theoretic description of the Rokhlin Invariant , Mathematische Annalen, Volume 249, 1980, pp. 243-263
  • with John James Millson : Deformation spaces associated to compact hyperbolic manifolds , Bulletin AMS, Volume 14, 1986, pp. 99-102

Web links

Individual evidence

  1. ^ Mathematician and early minimalist composer Dennis Johnson has died , accessed January 5, 2019.
  2. ^ Mathematics Genealogy Project
  3. ^ Johnson The structure of the Torelli group. I. A finite set of generators for T , Annals of Mathematics, Volume 118, 1983, pp. 423-442, Part 2 A characterization of the group generated by twists on boundary curves , Topology, Volume 24, 1985, pp. 113- 126, part 3 The abelianization of T , ibid. Pp. 127-144
  4. ^ Birman, Johnson, Putman Symplectic Heegaard splittings and linked abelian groups , in Groups of Diffeomorphisms , Advanced Studies in Pure Mathematics 52, Mathematical Society of Japan, 2008, pp. 135-220, Preprint
  5. ^ Kyle Gann Reconstructing November , American Music, Volume 28, 2010, No. 4
personal data
SURNAME Johnson, Dennis
ALTERNATIVE NAMES Johnson, Dennis Lee
BRIEF DESCRIPTION American mathematician
DATE OF BIRTH November 19, 1938
PLACE OF BIRTH los Angeles
DATE OF DEATH 20th December 2018
Place of death Morgan Hill