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Kennet VilsonPhysicist
Date of Birth: 08.06.1936
Country:  USA |
Content:
Kenneth Geddes Wilson
Early Life and EducationKenneth Geddes Wilson, a renowned American physicist, was born in Waltham, Massachusetts, as the eldest of four children to Emily (née Buckingham) Wilson and Edgar Bright Wilson Jr. His father, a microwave spectroscopist, taught chemistry at Harvard University. Wilson received his early education at private schools in Massachusetts. He excelled particularly in mathematics, recalling that he entertained himself by extracting cube roots mentally while waiting for the school bus. After spending a year at Magdalen College School in Oxford, England, he graduated from George School, a Quaker boarding school in Pennsylvania, in 1952.
Enrolling at Harvard University at age 16, Wilson studied mathematics and physics, earning his Bachelor of Arts degree in 1956. He then pursued graduate work in quantum field theory under the guidance of Murray Gell-Mann at the California Institute of Technology (Caltech), receiving his PhD in 1961. His doctoral dissertation was entitled "An Investigation of the Low Equation and the Chew Mandelshtam Equations."
Scientific Career
Following his dissertation, Wilson was awarded a Junior Fellowship at Harvard and later received a Ford Foundation Postdoctoral Fellowship (1962-1963) to work at CERN (the European Center for Nuclear Research). In 1963, he joined the physics faculty at Cornell University, where he became a full professor in 1970.
In his early work on elementary particles and their interactions, Wilson utilized a mathematical technique called renormalization, pioneered by Gell-Mann, Caltech colleague Francis Low, and others, to overcome certain difficulties in quantum electrodynamics. When quantum theory was directly applied to the behavior of elementary particles, it encountered troublesome quantities, such as infinite charges. Gell-Mann and Low introduced renormalization groups to modify the mathematical representation of, for example, a point-like particle such as an electron, smoothing out the obstacles for further application of the theory. Wilson made contributions to this theory, solving a problem related to K-mesons (kaons) in his doctoral dissertation.
At Cornell, partly inspired by the work of colleagues Michael Fisher and Benjamin Widom, Wilson became interested in critical phenomena, with an eye towards further applications of renormalization groups. Critical phenomena are the distinctive behaviors of materials at specific external conditions (e.g., temperature and pressure) at which the material's properties change abruptly. These specific conditions are known as the critical point. For instance, when considering water, the temperature at which the liquid freezes or turns to vapor depends on the pressure. During boiling, the liquid and vapor coexist, and if contained in a closed volume, they are said to be in equilibrium; they are usually easy to distinguish as they have vastly different densities. However, as the boiling temperature is raised along with the pressure, the density of the liquid decreases with increasing temperature as the liquid expands (the pressure only slightly compresses water), while the vapor (a gas) is highly compressed, becoming denser. If the heating is extended to maintain the boiling point as the pressure is increased, eventually a point is reached (pressure at 219 atmospheres, temperature at 374°C) where the two densities become the same and boiling ceases. It then becomes impossible to separate the liquid from the vapor, and the question loses its usual meaning. These values of pressure and temperature define the critical point of water. Another example of a critical point is the temperature (called the Curie point after Pierre Curie) below which a ferromagnetic material spontaneously begins to magnetize and above which it remains unmagnetized. If a magnet is heated above its Curie point, it loses its magnetic properties and does not "remember" its initial state when cooled again.
Critical phenomena were first studied systematically in the 1860s in carbon dioxide. Systems with critical points show a peculiar connection between interactions at very short distances (on a microscopic level) and the macroscopic characteristics of the bulk. In the case of water, the microscale phenomena boil down to the motion of molecules and their intermolecular attraction. For magnets, the determining factor is the ability of elementary magnets related to electron spins to influence their neighbors, compelling them into some ordered arrangement. Near the critical point, these ubiquitous interactions become greatly enhanced in magnitude, leading to a coherent macroscopic behavior.
Quantitatively understanding critical phenomena presented a daunting complexity due to the enormous number of independent microscopic interactions (degrees of freedom) and the correlations between different regions operating at larger distances, eventually encompassing the entire bulk. Quantities fluctuate from point to point and region to region, forming a hierarchy of different levels of interaction, or scales.
Scientists actively grappled with this problem, seeking avenues to reduce the complexities to manageable terms without compromising the underlying validity of the theory. In 1937, Russian physicist Lev Landau proposed what became known as mean-field theory for the case of magnets, in which he averaged out the fluctuations of magnetization, assuming that only fluctuations at the atomic level mattered. In 1944, Norwegian-American chemist Lars Onsager found an exact solution for a two-dimensional model, allowing him to calculate magnetic properties and also demonstrating the inadequacy of Landau's theory. The need arose for a new, more general theory.
In 1965, Widom suggested that changing the scale of interactions near the critical point should not alter the validity of the mathematical description. In 1966, American physicist Leo Kadanoff proposed dividing a ferromagnetic system near the critical point into cells, each containing a handful of atomic-level magnets, with the size of the cell defining the scale. Other scientists made partial contributions to a potential solution to the problem.
It was Wilson's application of renormalization group theory, however, that provided a successful method for describing behavior near a critical point and enabled the calculation of quantitative estimates of a system's properties via computers. In essence, Wilson broke the system into blocks arranged in a lattice-like grid, as Kadanoff had done. Starting from a fine scale with a large number of small blocks, he applied an averaging procedure. Then progressively increasing the scale and the size of the blocks, he repeated this procedure over and over until it converged to a final representation that yielded numerical results matching experimental data. At each step, the smaller-scale fluctuations averaged out, while the larger-scale fluctuations approached encompassing the entire system. He also discovered that systems near their critical points could be characterized by a small set of parameters that had the quality of universality. In other words, similar parameters could be used to calculate the behavior of a surprisingly wide range of other systems. Wilson and Fisher later developed some aspects of this method further, enhancing its utility.
Recognition and Impact
The significance of Wilson's achievement was quickly recognized by his fellow physicists. Landau had called critical phenomena the most important unsolved problem in theoretical physics, and Wilson himself later stated that the problems to which his method applied were among the hardest in physics. "If they weren't," he explained, "they would have been solved long ago by simpler ways." Wilson was awarded the 1982 Nobel Prize in Physics "for his theory of critical phenomena in connection with phase transitions." In presenting the prize, Stig Lundqvist of the Royal Swedish Academy of Sciences praised Wilson for his "elegant and profound" solution to the phase transition problem. The results obtained by Wilson, he said, "have given a complete theoretical description of the behavior near the critical point and have also led to methods for the numerical determination of the critical exponents. That his ideas and methods have during the decade that has elapsed since his first papers were published triumphed over the field is by now a matter of common knowledge."
Practical applications of renormalization are anticipated in areas such as the filtration of liquids through solids, freezing, crack propagation in metals, and the flow of oil in underground reservoirs—settings where complex microscopic physical processes manifest in macroscopic effects. In recent years, Wilson has sought to apply his methods to the theory of quarks, particles that Gell-Mann believed were the building blocks of protons, neutrons, and other subatomic particles previously considered elementary. Since 1976, Wilson has focused largely on computer simulations. Finding his theoretical work limited by the speed and memory of contemporary computers, he has become an advocate for establishing supercomputer centers dedicated to serving scientists.
Personal Life
In 1982, Wilson married Alison Brown, a computer scientist at the Cornell Computer Center. A former amateur musician who played the oboe, he enjoys folk dancing and hiking. He has described himself as "a workaholic who is primarily impressed by the number of things there are to do." Wilson is a member of the National Academy of Sciences and the American Academy of Arts and Sciences. His other honors include the Danny Heineman Prize for Mathematical Physics from the American Physical Society (1973), the Wolf Prize in Physics from the Wolf Foundation (1980), which he shared with Fisher and Kadanoff, and the California Institute of Technology Distinguished Alumni Award (1981). He holds an honorary Doctor of Science degree from Harvard University.
