Per Bak

Infobox Scientist
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name = Per Bak


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caption = Per Bak at the ITCP 1992.
birth_date = December 8 1948
birth_place = Brønderslev, Denmark
death_date = October 16 2002
death_place = Copenhagen, Denmark
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fields = Physicist
workplaces = Brookhaven National Laboratory
University of Copenhagen
Santa Fe Institute
Niels Bohr Institute
Imperial College London
alma_mater = Technical University of Denmark
Risø National Laboratory
doctoral_advisor =
academic_advisor =
doctoral_students = Sergei Maslov
Kim Sneppen
notable_students =
known_for = Self-organized criticality
Bak-Tang-Wiesenfeld sandpile
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Per Bak (December 8 1948 - October 16 2002) was a Danish theoretical physicist, attributed with the development of the concept of self-organized criticality.

Life and work

Bak was born in Brønderslev, Denmark. After studying at the Technical University of Denmark, he received a doctorate in 1974 and went on to work at Brookhaven National Laboratory in Upton, New York. He specialized in phase transitions, 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, presented new ideas on organization with a concept they coined self-organized criticality in an article in "Physical Review Letters". The first discovered example of a dynamical system displaying such self-organized criticality was named after them as the Bak-Tang-Wiesenfeld sandpile model.

Faced with many skeptics, Bak pursued the implications of his theory at a number of institutions, including the above mentioned Brookhaven National Laboratory, the Santa Fe Institute in New Mexico, the Niels Bohr Institute in Copenhagen and Imperial College London, where he became a professor in 2000.

He took his ideas to a broader audience in 1996 with his ambitiously entitled book, "How Nature Works".

In 2001, Bak learned that he had myelodysplastic syndrome. He died in 2002 in Copenhagen and was survived by his second wife, Maya Paczuski, a physicist at Imperial College, and his four children.

Others about Per Bak

*"He was the most American of Danes," said Predrag Cvitanović. "Danes eschew confrontation, but he was arrogant and loved to fight with his colleagues in academia. We all have stories of how we first met him, usually remembered by some outrageous statement or insult."
*A sample of Prof. Bak's statements at conferences: After a young and hopeful researcher had presented his recent work, Prof. Bak stood up and almost screamed: "Perhaps I'm the only crazy person in here, but I understand zero - I mean ZERO - of what you said!". Another young scholar was met with the gratifying question: "Excuse me, but what is actually non-trivial about what you did?"
*Chao Tang mentions his mentor's irreverent style, "He certainly was one of the most original people in science, and also one of the very few who truly doesn't care what other people think about what he is doing. He was sort of on his own."

Selected publications

Per Bak has written several important books and articles, including:
* 1982, "Commensurate phases, incommensurate phases, and the devil's staircase", in: "Reports on Progress in Physics", Vol. 45, pp.587-629;DOI|10.1088/0034-4885/45/6/001
* 1987, "Self-organized criticality: an explanation of $$1/f noise", with Chao Tang and Kurt Wiesenfeld, in: "Physical Review Letters", Vol. 59, pp.381-384;DOI|10.1103/PhysRevLett.59.381
* 1996, "How Nature Works: The Science of Self-Organized Criticality", New York: Copernicus. ISBN 0-387-94791-4

External links and references

* [http://www.nature.com/nature/journal/v420/n6913/full/420284a.html Obituary in Nature magazine]
* [http://3quarksdaily.blogs.com/3quarksdaily/2006/02/rx_sand_piles_a.html Sand Piles and Cancer] Short article about Per Bak by Azra Raza, M.D., in [http://3quarksdaily.com "3 Quarks Daily"]