Anders Lindstedt

Infobox_Scientist
name = Anders Lindstedt
birth_date = June 27, 1854
birth_place = Dalecarlia, Sweden MEMOIR ANDERS LINDSTEDT 27 June 1854-16 May 1939, Journal of the Institute of Actuaries, 70 (1939) p. 269. [http://www.actuaries.org.uk/__data/assets/pdf_file/0005/24377/0269.pdf] ]
death_date = May 16, 1939
death_place = Stockholm, Sweden
residence =
nationality =
field = Mathematician, astronomer and actuarial scientist
known_for = Lindstedt-Poincaré method
religion =
footnotes =

Anders Lindstedt (June 27, 1854 – May 16, 1939" [http://runeberg.org/hvar8dag/10/0162.html Hvar 8 dag, 10:de Årg, No 11, 13 december 1908, sid. 162] .] ) was a Swedish mathematician, astronomer and actuarial scientist, known for the Lindstedt-Poincaré method

Lindsted was born in a small village in the district of Sundborns,Dalecarlia a province in central Sweden. He obtained a PhD in from the University of Lund aged 32 and was subsequently appointed as a lecturer in astronomy. After numerous He later went on to a position at the University of Dorpat (then belonging to Russia, now University of Tartu in Estonia) where he worked for around seven years on theoretical astronomy.He combined practical astronomy with an interest in theory, developing especially an interest in the three body problem [cite journal|last = Lindstedt|first = A.|title = Über die Bestimmung der gegenseitigen Entfernungen in dem Probleme der drei Körper|journal = Astronomische Nachrichten|volume = 107|date = 1884|pages = 197–214|url = http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?db_key=AST&bibcode=1884AN....107..197L&letter=.&classic=YES&defaultprint=YES&whole_paper=YES&page=197&epage=197&send=Send+PDF&filetype=.pdf|doi = 10.1002/asna.18841071301 (Roughly translated, the title of this paper is "On determining the mutual distances in the three body problem".),] This work was to influence Poincaré [Jules Henri Poincaré (1890) "Sur le problème des trois corps et les équations de la dynamique. Divergence des séries de M. Lindstedt," Acta Mathematica, vol. 13, pages 1–270.,] whose work on the three-body problem led to the discovery that there can be orbits which are nonperiodic, and yet not forever increasing nor approaching a fixed point, the beginning of what we now know as 'chaos theory'.

His papers written during that period on celestial mechanics including a technique for uniformly approximating periodic solutions to ordinary differential equations when regular perturbation approaches fail [A. Lindstedt, Abh. K. Akad. Wiss. St. Petersburg 31, No. 4 (1882)] . This was later developed by Henri Poincaré [ H. Poincaré, Les Méthodes Nouvelles de la Mécanique Célèste I, II, III (Dover Publ., New York,1957).] and known today as the Lindstedt-Poincaré method.

Lindstedt returned to Sweden in 1886 to take a post at professor at the Royal Institute of TechnologyFact|date=September 2008 in Stockholm. During the period occupying this position, until 1909, he developed an interest in actuarial science. He made contributions to the theory of pension funds and worked as a member of government committees responsible for insurance law and social insurance. He became a corresponding member of the Institute of Actuaries in London. He was for a time Kings Inspector of insurance companies.

In 1909 he resigned his professorial position to work full time on insurance. In 1912 Lindstedt constructed a life table for annuities [Cramer H and H Wold (1935), Mortality variations in Sweden: a study in graduation and forecasting, Skandinavisk Aktuarietidskrift, 18: 161–241] using data from Swedish population experience and for each age was able to extrapolate the sequence of annual probability of death, namelythe mortality profile. Probably, this work constitutes the earliest projection of age-specific functions [Pitcco, Ermnno, From Halley to Frailty: A Review of Survival Models for Actuarial Calculations, [http://ssrn.com/bstrct=741586] ] . He directed the actuarial work which underpinned the state old age an invalidity pensions in Sweden introduced in 1913 as part of the "National Pension Act" (see Swedish welfare).

Even after his retirement aged 70 he continued to take an active interest in actuarial activities both in Sweden and abroad, attending meetings of the Swedish Actuarial Society until shortly before his death in 1939.

References