Per Bak
Encyclopedia
Per Bak was a Danish
theoretical physicist
who coauthored the 1987 academic paper that coined the term "self-organized criticality
."
in 1974, Bak worked at Brookhaven National Laboratory
. He specialized in phase transition
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
setting a new concept they called self-organized criticality
. The first discovered example of a dynamical system
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 Niels Bohr Institute
in Copenhagen, and Imperial College London
, where he became a professor in 2000.
In 1996, he took his ideas to a broader audience with his ambitiously entitled book, How Nature Works.
In 2001, Bak learned that he had myelodysplastic syndrome
and died from it the following year. He was survived by his second wife, Maya Paczuski
, a fellow physicist at Imperial College, and his four children.
Denmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
theoretical physicist
Theoretical physics
Theoretical physics is a branch of physics which employs mathematical models and abstractions of physics to rationalize, explain and predict natural phenomena...
who coauthored the 1987 academic paper that coined the term "self-organized criticality
Self-organized criticality
In physics, self-organized criticality is a property of dynamical systems which have a critical point as an attractor. Their macroscopic behaviour thus displays the spatial and/or temporal scale-invariance characteristic of the critical point of a phase transition, but without the need to tune...
."
Life and work
After receiving his Ph.D. from the Technical University of DenmarkTechnical University of Denmark
The Technical University of Denmark , often simply referred to as DTU, is a university just north of Copenhagen, Denmark. It was founded in 1829 at the initiative of Hans Christian Ørsted as Denmark's first polytechnic, and is today ranked among Europe's leading engineering institutions, and the...
in 1974, Bak worked at Brookhaven National Laboratory
Brookhaven National Laboratory
Brookhaven National Laboratory , is a United States national laboratory located in Upton, New York on Long Island, and was formally established in 1947 at the site of Camp Upton, a former U.S. Army base...
. He specialized in phase transition
Phase transition
A phase transition is the transformation of a thermodynamic system from one phase or state of matter to another.A phase of a thermodynamic system and the states of matter have uniform physical properties....
s, such as those occurring when an insulator
Electrical insulation
thumb|250px|[[Coaxial Cable]] with dielectric insulator supporting a central coreThis article refers to electrical insulation. For insulation of heat, see Thermal insulation...
suddenly becomes a conductor or when water freezes. In that context, he also did important work on complicated spatially modulated
ANNNI model
In statistical physics, the axial next-nearest-neighbor Ising model, usually known as the ANNNI model, is a variant of the Ising model in which competing ferromagnetic and...
(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
Chao Tang
Chao Tang is a Chinese physicist and professor at the University of California at San Francisco.In 1987, as a post-doctoral research scientist in the Solid State Theory Group of Brookhaven National Laboratory, he and another fellow post-doctoral scientist, Kurt Wiesenfeld, along with their mentor,...
and Kurt Wiesenfeld
Kurt Wiesenfeld
Kurt Wiesenfeld is an American physicist working primarily on non-linear dynamics. His works primarily concern stochastic resonance, spontaneous synchronization of coupled oscillators, and non-linear laser dynamics...
, published an article in Physical Review Letters
Physical Review Letters
Physical Review Letters , established in 1958, is a peer reviewed, scientific journal that is published 52 times per year by the American Physical Society...
setting a new concept they called self-organized criticality
Self-organized criticality
In physics, self-organized criticality is a property of dynamical systems which have a critical point as an attractor. Their macroscopic behaviour thus displays the spatial and/or temporal scale-invariance characteristic of the critical point of a phase transition, but without the need to tune...
. The first discovered example of a dynamical system
Dynamical system
A dynamical system is a concept in mathematics where a fixed rule describes the time dependence of a point in a geometrical space. Examples include the mathematical models that describe the swinging of a clock pendulum, the flow of water in a pipe, and the number of fish each springtime in a...
displaying such self-organized criticality, the Bak-Tang-Wiesenfeld sandpile
Bak-Tang-Wiesenfeld sandpile
In physics, the Bak–Tang–Wiesenfeld sandpile model is the first discovered example of a dynamical system displaying self-organized criticality and is named after Per Bak, Chao Tang and Kurt Wiesenfeld....
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
Santa Fe Institute
The Santa Fe Institute is an independent, nonprofit theoretical research institute located in Santa Fe and dedicated to the multidisciplinary study of the fundamental principles of complex adaptive systems, including physical, computational, biological, and social systems.The Institute houses a...
, the Niels Bohr Institute
Niels Bohr Institute
The Niels Bohr Institute is a research institute of the University of Copenhagen. The research of the institute spans astronomy, geophysics, nanotechnology, particle physics, quantum mechanics and biophysics....
in Copenhagen, and Imperial College London
Imperial College London
Imperial College London is a public research university located in London, United Kingdom, specialising in science, engineering, business and medicine...
, where he became a professor in 2000.
In 1996, he took his ideas to a broader audience with his ambitiously entitled book, How Nature Works.
In 2001, Bak learned that he had myelodysplastic syndrome
Myelodysplastic syndrome
The myelodysplastic syndromes are a diverse collection of hematological medical conditions that involve ineffective production of the myeloid class of blood cells....
and died from it the following year. He was survived by his second wife, Maya Paczuski
Maya Paczuski
-External link:*...
, a fellow physicist at Imperial College, and his four children.
Others about Per Bak
- "He was the most American of Danes," said Predrag CvitanovićPredrag CvitanovicPredrag Cvitanović, is currently an endowed Professor of Physics at the Georgia Institute of Technology. He is highly regarded for his work in nonlinear dynamics, particularly his contributions to periodic orbit theory...
. "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
- 1982, "Commensurate phases, incommensurate phases, and the devil's staircase", in: Reports on Progress in Physics, Vol. 45, pp.587-629;
- 1987, "Self-organized criticality: an explanation of 1/f noise", with Chao TangChao TangChao Tang is a Chinese physicist and professor at the University of California at San Francisco.In 1987, as a post-doctoral research scientist in the Solid State Theory Group of Brookhaven National Laboratory, he and another fellow post-doctoral scientist, Kurt Wiesenfeld, along with their mentor,...
and Kurt WiesenfeldKurt WiesenfeldKurt Wiesenfeld is an American physicist working primarily on non-linear dynamics. His works primarily concern stochastic resonance, spontaneous synchronization of coupled oscillators, and non-linear laser dynamics...
, in: Physical Review Letters, Vol. 59, pp.381-384; - 1996, How Nature Works: The Science of Self-Organized Criticality, New York: Copernicus. ISBN 0-387-94791-4
External links and references
- Obituary in NatureNatureNature, in the broadest sense, is equivalent to the natural world, physical world, or material world. "Nature" refers to the phenomena of the physical world, and also to life in general...
. - Sand Piles and Cancer. Short article about Per Bak by Azra Raza, M.D., in 3 Quarks Daily