Per Bak (8 December 1948 – 16 October 2002) was a

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish a ...

theoretical physicist Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain and predict natural phenomena. This is in contrast to experimental physics, which uses experime ...

who coauthored the 1987 academic paper that coined the term "

self-organized criticality Self-organized criticality (SOC) is a property of dynamical systems that have a critical point as an attractor. Their macroscopic behavior thus displays the spatial or temporal scale-invariance characteristic of the critical point of a phase ...

Life and work

After receiving his Ph.D. from the

Technical University of Denmark The Technical University of Denmark ( da, Danmarks Tekniske Universitet), often simply referred to as DTU, is a polytechnic university and school of engineering. It was founded in 1829 at the initiative of Hans Christian Ørsted as Denmark's fir ...

in 1974, Bak worked at

Brookhaven National Laboratory Brookhaven National Laboratory (BNL) is a United States Department of Energy national laboratory located in Upton, Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base and Japanese internment c ...

. He specialized in

phase transition In chemistry, thermodynamics, and other related fields, a phase transition (or phase change) is the physical process of transition between one state of a medium and another. Commonly the term is used to refer to changes among the basic states o ...

s, such as those occurring when an insulator suddenly becomes a conductor or when water freezes. In that context, he also did important work on complicated spatially modulated (magnetic) structures in solids. This research led him to the more general question of how organization emerges from disorder. In 1987, he and two postdoctoral researchers, Chao Tang and Kurt Wiesenfeld, published an article in ''

Physical Review Letters ''Physical Review Letters'' (''PRL''), established in 1958, is a peer-reviewed, scientific journal that is published 52 times per year by the American Physical Society. As also confirmed by various measurement standards, which include the ''Journa ...

'' setting a new concept they called

. The first discovered example of a

dynamical system In mathematics, a dynamical system is a system in which a function describes the time dependence of a point in an ambient space. Examples include the mathematical models that describe the swinging of a clock pendulum, the flow of water in ...

displaying such self-organized criticality, the Bak-Tang-Wiesenfeld sandpile model, was named after them. Faced with many skeptics, Bak pursued the implications of his theory at a number of institutions, including the Brookhaven National Laboratory, the

Santa Fe Institute The Santa Fe Institute (SFI) is an independent, nonprofit theoretical research institute located in Santa Fe, New Mexico, United States and dedicated to the multidisciplinary study of the fundamental principles of complex adaptive systems, inclu ...

, the Niels Bohr Institute in Copenhagen, and

Imperial College London Imperial College London (legally Imperial College of Science, Technology and Medicine) is a public research university in London, United Kingdom. Its history began with Prince Albert, consort of Queen Victoria, who developed his vision for a cu ...

, where he became a professor in 2000. In 1996, he took his ideas to a broader audience with his ambitiously titled book, ''How Nature Works''. In 2001, Bak learned that he had

myelodysplastic syndrome A myelodysplastic syndrome (MDS) is one of a group of cancers in which immature blood cells in the bone marrow do not mature, and as a result, do not develop into healthy blood cells. Early on, no symptoms typically are seen. Later, symptoms may ...

and died from it the following year. Bak is survived by his second wife, Maya Paczuski, a fellow physicist and current professor at the

University of Calgary The University of Calgary (U of C or UCalgary) is a public research university located in Calgary, Alberta, Canada. The University of Calgary started in 1944 as the Calgary branch of the University of Alberta, founded in 1908, prior to being ins ...

, with whom he has coauthored papers, and his four children.

Selected publications

* * * 1996, ''How Nature Works: The Science of Self-Organized Criticality'', New York: Copernicus. *

References

* {{DEFAULTSORT:Bak, Per 1948 births 2002 deaths Deaths from myelodysplastic syndrome People from Brønderslev Academics of Imperial College London Complex systems scientists 20th-century Danish physicists Brookhaven National Laboratory staff Fellows of the American Physical Society