E.G.D. Cohen
Encyclopedia
E.G.D. Cohen is an American physicist, and is Professor Emeritus at The Rockefeller University. He is widely recognised for his contributions to statistical physics
. In 2004 Cohen was awarded the Boltzmann Medal
, jointly with Prof. H. Eugene Stanley
. Cohen's citation read "For his fundamental contributions to nonequilibrium statistical mechanics, including the development of a theory of transport phenomena in dense gases, and the characterization of measures and fluctuations in nonequilibrium stationary states."
being sheltered in safe houses in Holland. He received his B.Sc. at the University of Amsterdam in 1952 and his Ph.D. at the University of Amsterdam in 1957. He was a research associate for two years at the University of Michigan
, Ann Arbor working with George Uhlenbeck and Theodore Berlin, the Johns Hopkins University
and an associate professor at the Institute for Theoretical Physics at the University of Amsterdam before moving to the Rockefeller University in New York as a professor in 1963.
In 2004 Cohen received the triannual Boltzmann Medal
from the Committee on Thermodynamics and Statistical Mechanics of the International Union of Pure and Applied Physics
, its highest award for contributions to statistical mechanics. In that same year, he was honored with a Royal Knighthood in the Order of the Dutch Lion
. He is the editor of a number of books, including the series Fundamental Problems in Statistical Mechanics, I–VI, which contains an account of the developments in his field over almost 45 years. These books contain the proceedings of a summer school in statistical mechanics that he founded in 1961 in the Netherlands.
For most of Cohen's career he has focused on nonequilibrium statistical mechanics. Together with J.R. Dorfman in the 1960s he proved that a power series expansion of transport coefficients in the density (analogous to the virial expansion of the pressure in terms of the density), is in fact divergent. This discovery effectively closed off one entire line of research in nonequilibrium statistical mechanics.
Later with Denis Evans
and Gary Morriss in 1990 he proved that for certain classes of thermostatted nonequilibrium steady states the relevant transport coefficient the transport coefficient has a simple relation to the sum of the largest and smallest Lyapunov exponents describing the trajectory of the N-particle steady state system in phase space. This relation is called the Conjugate Pairing Rule. This was the first practical relationship between chaotic measures and thermophysical properties.
In 1993 Denis Evans, Cohen and Gary Morriss announced the first steady state Fluctuation Theorem
describing asymptotic fluctuations of time averaged fluctuations of what has since become known as dissipation, in nonequilibrium steady states. In the same paper they also gave an heuristic proof of that relation using local Lyapunov weights
In 1995 Gallavotti and Cohen described a proof employing the so-called chaotic hypothesis, of the so-called Gallavotti Cohen Fluctuation Theorem
. This proof formalised the heuristic proof given in 1993 by Denis Evans, Cohen and Gary Morriss.
Another interest of Cohen's is the diffusion of independent point particles moving on a lattice occupied by two kinds of obstacles that scatter the particles according to certain deterministic scattering rules. This mixture of random and deterministic features has led to a number of new types of particle diffusion, which can evolve suddenly to propagation. Cohen's lab has focused on determining a numerical approach to understand the origin of this phenomenon, because neither probability theory nor kinetic theory is applicable to these systems.
Statistical physics
Statistical physics is the branch of physics that uses methods of probability theory and statistics, and particularly the mathematical tools for dealing with large populations and approximations, in solving physical problems. It can describe a wide variety of fields with an inherently stochastic...
. In 2004 Cohen was awarded the Boltzmann Medal
Boltzmann Medal
The Boltzmann Medal is the most important prize awarded to physicists that obtain new results concerning statistical mechanics; it is named after the celebrated physicist Ludwig Boltzmann...
, jointly with Prof. H. Eugene Stanley
H. Eugene Stanley
Harry Eugene Stanley is an American physicist and University Professor at Boston University. He has made seminal contributions to statistical physics and is one of the pioneers of interdisciplinary science...
. Cohen's citation read "For his fundamental contributions to nonequilibrium statistical mechanics, including the development of a theory of transport phenomena in dense gases, and the characterization of measures and fluctuations in nonequilibrium stationary states."
Personal profile
Ezechiel (Eddie) Godert David Cohen was born in Amsterdam in January 1923. He spent World War IIWorld War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...
being sheltered in safe houses in Holland. He received his B.Sc. at the University of Amsterdam in 1952 and his Ph.D. at the University of Amsterdam in 1957. He was a research associate for two years at the University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
, Ann Arbor working with George Uhlenbeck and Theodore Berlin, the Johns Hopkins University
Johns Hopkins University
The Johns Hopkins University, commonly referred to as Johns Hopkins, JHU, or simply Hopkins, is a private research university based in Baltimore, Maryland, United States...
and an associate professor at the Institute for Theoretical Physics at the University of Amsterdam before moving to the Rockefeller University in New York as a professor in 1963.
In 2004 Cohen received the triannual Boltzmann Medal
Boltzmann Medal
The Boltzmann Medal is the most important prize awarded to physicists that obtain new results concerning statistical mechanics; it is named after the celebrated physicist Ludwig Boltzmann...
from the Committee on Thermodynamics and Statistical Mechanics of the International Union of Pure and Applied Physics
International Union of Pure and Applied Physics
The International Union of Pure and Applied Physics is an international non-governmental organization devoted to the advancement of physics...
, its highest award for contributions to statistical mechanics. In that same year, he was honored with a Royal Knighthood in the Order of the Dutch Lion
Order of the Dutch Lion
The Order of the Netherlands Lion is an order of the Netherlands which was first created on 29 September 1815 by King William I of the Netherlands....
. He is the editor of a number of books, including the series Fundamental Problems in Statistical Mechanics, I–VI, which contains an account of the developments in his field over almost 45 years. These books contain the proceedings of a summer school in statistical mechanics that he founded in 1961 in the Netherlands.
Research interests
Early in his career, Cohen predicted the possibility of an incomplete phase separation in liquid helium mixtures at very low temperatures that was later discovered experimentally, leading to the design of the helium dilution refrigerator, one of the basic low-temperature instruments available.For most of Cohen's career he has focused on nonequilibrium statistical mechanics. Together with J.R. Dorfman in the 1960s he proved that a power series expansion of transport coefficients in the density (analogous to the virial expansion of the pressure in terms of the density), is in fact divergent. This discovery effectively closed off one entire line of research in nonequilibrium statistical mechanics.
Later with Denis Evans
Denis Evans
Denis James Evans, , is a Professor in the Research School of Chemistry at the Australian National University...
and Gary Morriss in 1990 he proved that for certain classes of thermostatted nonequilibrium steady states the relevant transport coefficient the transport coefficient has a simple relation to the sum of the largest and smallest Lyapunov exponents describing the trajectory of the N-particle steady state system in phase space. This relation is called the Conjugate Pairing Rule. This was the first practical relationship between chaotic measures and thermophysical properties.
In 1993 Denis Evans, Cohen and Gary Morriss announced the first steady state Fluctuation Theorem
Fluctuation theorem
The fluctuation theorem , which originated from statistical mechanics, deals with the relative probability that the entropy of a system which is currently away from thermodynamic equilibrium will increase or decrease over a given amount of time...
describing asymptotic fluctuations of time averaged fluctuations of what has since become known as dissipation, in nonequilibrium steady states. In the same paper they also gave an heuristic proof of that relation using local Lyapunov weights
In 1995 Gallavotti and Cohen described a proof employing the so-called chaotic hypothesis, of the so-called Gallavotti Cohen Fluctuation Theorem
Fluctuation theorem
The fluctuation theorem , which originated from statistical mechanics, deals with the relative probability that the entropy of a system which is currently away from thermodynamic equilibrium will increase or decrease over a given amount of time...
. This proof formalised the heuristic proof given in 1993 by Denis Evans, Cohen and Gary Morriss.
Another interest of Cohen's is the diffusion of independent point particles moving on a lattice occupied by two kinds of obstacles that scatter the particles according to certain deterministic scattering rules. This mixture of random and deterministic features has led to a number of new types of particle diffusion, which can evolve suddenly to propagation. Cohen's lab has focused on determining a numerical approach to understand the origin of this phenomenon, because neither probability theory nor kinetic theory is applicable to these systems.
Selected publications
- "Difficulties in the kinetic theory of dense gases", with J R Dorfman, J. Math. Phys. Bd.8, p. 282(1967).
- Editor "Statistical Mechanics at the Turn of the Decade", Dekker 1971 (Festschrift for the 70th birthday of Uhlenbeck), including his essay: "The generalization of the Boltzmann equation to higher densities"
- "The Boltzmann Equation", Walter Thirring (Editor), Wien 1973
- "The kinetic theory of dense gases", in Cohen (Editor) Fundamental problems of statistical mechanics, Vol.2, North Holland 1968
- "Kinetic approach to non equilibrium phenomena", physicists in Mehra The concept of nature, Reidel 1973
- "The kinetic theory of fluids-an introduction", Physics Today, January 1984
- "Kinetic theory - Understanding nature through collisions", American Journal of Physics, Bd.60, 1993, p. 524
- "Transport coefficients and Lyapunov exponents", Physica A 213, 293(1995).
- "Boltzmann and Statistical Mechanics", http://arXiv.org/pdf/:cond-mat/9608054, 1996
- "George E. Uhlenbeck and Statistical Mechanics", Am. J. Phys., 58, 618(1990).
- "Viscosity of a simple fluid from its maximal Lyapunov exponents", with Evans and Morriss, Phys. Rev. A., 42, pp. 5990–5997 (1990).
- "Probability of second law violations in nonequilibrium steady states", Phys. Rev. Lett, 71, pp. 2401–2404 (1993); Erratum, 71, 3616 (1993).