Anders Lindstedt (27 June 1854 – 16 May 1939) was a

Swedish Swedish or ' may refer to: Anything from or related to Sweden, a country in Northern Europe. Or, specifically: * Swedish language, a North Germanic language spoken primarily in Sweden and Finland ** Swedish alphabet, the official alphabet used by ...

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, structure, space, models, and change. History On ...

, astronomer, and actuarial scientist, known for the Lindstedt-Poincaré method.

Life and work

Lindstedt was born in a small village in the district of Sundborns,

Dalecarlia Dalarna () is a '' landskap'' (historical province) in central Sweden. English exonyms for it are Dalecarlia () and the Dales. Dalarna adjoins Härjedalen, Hälsingland, Gästrikland, Västmanland and Värmland. It is also bordered by Norway i ...

a province in central Sweden.
Hvar 8 dag, 10:de Årg, No 11, 13 december 1908, sid. 162
'.Memoir Anders Lindstedt 27 June 1854-16 May 1939, Journal of the Institute of Actuaries, 70 (1939) p. 269

/ref> He obtained a PhD from the

University of Lund , motto = Ad utrumque , mottoeng = Prepared for both , established = , type = Public research university , budget = SEK 9 billion University of Tartu The University of Tartu (UT; et, Tartu Ülikool; la, Universitas Tartuensis) is a university in the city of Tartu in Estonia. It is the national university of Estonia. It is the only classical university in the country, and also its biggest ...

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 In physics and classical mechanics, the three-body problem is the problem of taking the initial positions and velocities (or momenta) of three point masses and solving for their subsequent motion according to Newton's laws of motion and Newton's ...

This work was to influence Poincaré 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 Chaos theory is an interdisciplinary area of scientific study and branch of mathematics focused on underlying patterns and deterministic laws of dynamical systems that are highly sensitive to initial conditions, and were once thought to have co ...

'. His papers on

celestial mechanics Celestial mechanics is the branch of astronomy that deals with the motions of objects in outer space. Historically, celestial mechanics applies principles of physics (classical mechanics) to astronomical objects, such as stars and planets, to ...

written during that period include a technique for uniformly approximating periodic solutions to

ordinary differential equations In mathematics, an ordinary differential equation (ODE) is a differential equation whose unknown(s) consists of one (or more) function(s) of one variable and involves the derivatives of those functions. The term ''ordinary'' is used in contrast w ...

when regular perturbation approaches fail. This was later developed by

Henri Poincaré Jules Henri Poincaré ( S: stress final syllable ; 29 April 1854 – 17 July 1912) was a French mathematician, theoretical physicist, engineer, and philosopher of science. He is often described as a polymath, and in mathematics as "The ...

and is known today as the Lindstedt–Poincaré method. Lindstedt returned to Sweden in 1886 to take a post as professor at the

Royal Institute of Technology The KTH Royal Institute of Technology ( sv, Kungliga Tekniska högskolan, lit=Royal Institute of Technology), abbreviated KTH, is a public research university in Stockholm, Sweden. KTH conducts research and education in engineering and technolo ...

Stockholm Stockholm () is the Capital city, capital and List of urban areas in Sweden by population, largest city of Sweden as well as the List of urban areas in the Nordic countries, largest urban area in Scandinavia. Approximately 980,000 people liv ...

, where he was rector from 1903 to 1909. During his time at the institute, until 1909, he developed an interest in actuarial science. He made contributions to the theory of

pension funds A pension fund, also known as a superannuation fund in some countries, is any plan, fund, or scheme which provides retirement income. Pension funds typically have large amounts of money to invest and are the major investors in listed and priva ...

and worked as a member of government committees responsible for

insurance law Insurance law is the practice of law surrounding insurance, including insurance policies and claims. It can be broadly broken into three categories - regulation of the business of insurance; regulation of the content of insurance policies, especial ...

and

social insurance Social insurance is a form of Social protection, social welfare that provides insurance against economic risks. The insurance may be provided publicly or through the subsidizing of private insurance. In contrast to other forms of Welfare, soci ...

. He became a corresponding member of the

Institute of Actuaries The Institute of Actuaries was one of the two professional bodies which represented actuaries in the United Kingdom. The institute was based in England, while the other body, the Faculty of Actuaries, was based in Scotland. While the Institute and ...

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 Insurance is a means of protection from financial loss in which, in exchange for a fee, a party agrees to compensate another party in the event of a certain loss, damage, or injury. It is a form of risk management, primarily used to hedge ...

. From 1909 to 1916 Lindstedt was also a Justice of the

Supreme Administrative Court of Sweden The Supreme Administrative Court of Sweden ( sv, Högsta förvaltningsdomstolen, before 2011 ''Regeringsrätten'', acronym ''RR'' or ''RegR'') is the supreme court and the third and final tier for administrative court cases in Sweden, and is loca ...

. In 1912 Lindstedt constructed a

life table In actuarial science and demography, a life table (also called a mortality table or actuarial table) is a table which shows, for each age, what the probability is that a person of that age will die before their next birthday ("probability of deat ...

for

annuities In investment, an annuity is a series of payments made at equal intervals.Kellison, Stephen G. (1970). ''The Theory of Interest''. Homewood, Illinois: Richard D. Irwin, Inc. p. 45 Examples of annuities are regular deposits to a savings account, mo ...

using data from Swedish population experience and for each age was able to

extrapolate In mathematics, extrapolation is a type of estimation, beyond the original observation range, of the value of a variable on the basis of its relationship with another variable. It is similar to interpolation, which produces estimates between know ...

the sequence of annual

probability Probability is the branch of mathematics concerning numerical descriptions of how likely an Event (probability theory), event is to occur, or how likely it is that a proposition is true. The probability of an event is a number between 0 and ...

of death, namely the 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

/ref> 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#History, 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.

Notes

{{DEFAULTSORT:Lindstedt, Anders 1854 births 1939 deaths 19th-century Swedish astronomers 19th-century Swedish mathematicians Academic staff of the KTH Royal Institute of Technology Rectors of KTH Royal Institute of Technology Lund University alumni Swedish actuaries Justices of the Supreme Administrative Court of Sweden 20th-century Swedish mathematicians 20th-century Swedish judges