Ronald Kay Getoor (9 February 1929,

Royal Oak, Michigan Royal Oak is a city in Oakland County in the U.S. state of Michigan. An inner-ring suburb of Detroit, Royal Oak is about north of Detroit's city limits. As of the 2010 census, the city had a population of 57,236. Royal Oak is located along th ...

– 28 October 2017,

La Jolla, San Diego, California LA most frequently refers to Los Angeles, the second largest city in the United States. La, LA, or L.A. may also refer to: Arts and entertainment Music * La (musical note), or A, the sixth note * "L.A.", a song by Elliott Smith on ''Figure ...

) was an American mathematician. Getoor received from the

University of Michigan , mottoeng = "Arts, Knowledge, Truth" , former_names = Catholepistemiad, or University of Michigania (1817–1821) , budget = $10.3 billion (2021) , endowment = $17 billion (2021)As o ...

bachelor's degree in 1950, master's degree in 1951, and Ph.D. in 1954 under Arthur Herbert Copeland with thesis ''Connections between operators in Hilbert space and random functions of second order''. As a postdoc he was an instructor at

Princeton University Princeton University is a private university, private research university in Princeton, New Jersey. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is the List of Colonial Colleges, fourth-oldest ins ...

. He became in 1956 an assistant professor and then full professor at the

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...

. During the academic year 1964–1965 he was a visiting professor at

Stanford University Stanford University, officially Leland Stanford Junior University, is a private research university in Stanford, California. The campus occupies , among the largest in the United States, and enrolls over 17,000 students. Stanford is consider ...

. From 1966 until his retirement in 2000 he was a professor at the

University of California, San Diego The University of California, San Diego (UC San Diego or colloquially, UCSD) is a public university, public Land-grant university, land-grant research university in San Diego, California. Established in 1960 near the pre-existing Scripps Insti ...

. Getoor's research deals with

probability theory Probability theory is the branch of mathematics concerned with probability. Although there are several different probability interpretations, probability theory treats the concept in a rigorous mathematical manner by expressing it through a set o ...

, especially the theory of

Markov process A Markov chain or Markov process is a stochastic model describing a sequence of possible events in which the probability of each event depends only on the state attained in the previous event. Informally, this may be thought of as, "What happe ...

es and

potential theory In mathematics and mathematical physics, potential theory is the study of harmonic functions. The term "potential theory" was coined in 19th-century physics when it was realized that two fundamental forces of nature known at the time, namely gravi ...

. In 1970 he was an

invited speaker at the International Congress of Mathematicians This is a list of International Congresses of Mathematicians Plenary and Invited Speakers. Being invited to talk at an International Congress of Mathematicians has been called "the equivalent, in this community, of an induction to a hall of fame." ...

Nice Nice ( , ; Niçard: , classical norm, or , nonstandard, ; it, Nizza ; lij, Nissa; grc, Νίκαια; la, Nicaea) is the prefecture of the Alpes-Maritimes department in France. The Nice agglomeration extends far beyond the administrative c ...

. He was elected a Fellow of the

Institute of Mathematical Statistics The Institute of Mathematical Statistics is an international professional and scholarly society devoted to the development, dissemination, and application of statistics and probability. The Institute currently has about 4,000 members in all parts o ...

and in 2012 a Fellow of the

American Mathematical Society The American Mathematical Society (AMS) is an association of professional mathematicians dedicated to the interests of mathematical research and scholarship, and serves the national and international community through its publications, meetings, ...

Scientific work

In the late 1950s, Getoor and Robert Blumenthal set out to understand the work of

Gilbert Hunt Gilbert Agnew Hunt, Jr. (March 4, 1916 – May 30, 2008) was an American mathematician and amateur tennis player active in the 1930s and 1940s. Early life and education Hunt was born in Washington, D.C. and attended Eastern High School (Washing ...

on the connection between

Markov processes Markov ( Bulgarian, russian: Марков), Markova, and Markoff are common surnames used in Russia and Bulgaria. Notable people with the name include: Academics *Ivana Markova (born 1938), Czechoslovak-British emeritus professor of psychology at ...

and potential theory, extending the connections between

Brownian motion Brownian motion, or pedesis (from grc, πήδησις "leaping"), is the random motion of particles suspended in a medium (a liquid or a gas). This pattern of motion typically consists of random fluctuations in a particle's position insi ...

and Newtonian potential theory. Getoor's book on 'Markov processes and potential theory', co-authored with Blumenthal, became a reference on the topic. Together with Blumenthal and Sharpe, Getoor obtained many results on the fine structure of

es and martingales, in particular the theory of

local time Local time is the time observed in a specific locality. There is no canonical definition. Originally it was mean solar time, but since the introduction of time zones it is generally the time as determined by the time zone in effect, with daylight s ...

for Markov processes. With Michael J. Sharpe, Getoor defined the notion of 'conformal martingale', which proved to be influential in potential theory, investigated the behavior of Bessel processes, last-exit times and excursions. Starting in the early 1980s, Getoor studied stationary extensions of a given strong Markov process, with time extending to infinity in both directions, formulating a pathwise view of "time reversal" which became a key tool in his studies of the excessive measures of a Markov process. The 'Blumenthal-Getoor index', a concept which characterises the nature of discontinuities of

Lévy processes Levy, Lévy or Levies may refer to: People * Levy (surname), people with the surname Levy or Lévy * Levy Adcock (born 1988), American football player * Levy Barent Cohen (1747–1808), Dutch-born British financier and community worker * Levy ...

and semi-martingales, is named after him.

Personal life

He married in 1959. His wife Ann Getoor worked on the design of commercial aircraft at Boeing, and his daughter Lise Getoor is a professor of computer science at the

University of California, Santa Cruz The University of California, Santa Cruz (UC Santa Cruz or UCSC) is a public university, public Land-grant university, land-grant research university in Santa Cruz, California. It is one of the ten campuses in the University of California syste ...

. Getoor died at home on October 28, 2017, in La Jolla at the age of 88.

Selected publications

;Books * * with

Robert McCallum Blumenthal Robert "Bob" McCallum Blumenthal (7 February 1931, Chicago – 8 November 2012) was an American mathematician, specializing in probability theory. He is known for Blumenthal's zero-one law. Biography He received his Ph.D. in mathematics from Corn ...

: * ;Articles * * * * * *

References

External links

Getoor, Ronald K., Royal Oak High School Hall of FameComplete bibliography
{{DEFAULTSORT:Getoor, Ronald 1929 births 2017 deaths American probability theorists University of Michigan alumni University of Washington faculty University of California, San Diego faculty Fellows of the Institute of Mathematical Statistics Fellows of the American Mathematical Society People from Royal Oak, Michigan