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Mitchell Jay Feigenbaum (born December 19, 1944) is a mathematical physicist whose pioneering studies in chaos theory led to the discovery of the Feigenbaum constants.

Feigenbaum was born in Philadelphia, Pennsylvania, to Polish and Ukrainian Jewish immigrants. His education was not a happy one. Despite excelling in examinations, his early schooling at Tilden High School, Brooklyn, New York, and the City College of New York seemed unable to stimulate his appetite to learn. However, in 1964 he began his graduate studies at the Massachusetts Institute of Technology (MIT). Enrolling for graduate study in electrical engineering, he changed his area to physics. He completed his doctorate in 1970 for a thesis on dispersion relations, under the supervision of Professor Francis E. Low.

After short positions at Cornell University and the Virginia Polytechnic Institute, he was offered a longer-term post at the Los Alamos National Laboratory in New Mexico to study turbulence in fluids. Although that group of researchers was ultimately unable to unravel the currently intractable theory of turbulent fluids, his research led him to study chaotic mappings.

Some mathematical mappings involving a single linear parameter exhibit the apparently random behavior known as chaos when the parameter lies within certain ranges. As the parameter is increased towards this region, the mapping undergoes bifurcations at precise values of the parameter. At first there is one stable point, then bifurcating to an oscillation between two values, then bifurcating again to oscillate between four values and so on. In 1975, Dr. Feigenbaum, using the small HP-65 computer he had been issued, discovered that the ratio of the difference between the values at which such successive period-doubling bifurcations occur tends to a constant of around 4.6692... He was then able to provide a mathematical proof of that fact, and he then showed that the same behavior, with the same mathematical constant, would occur within a wide class of mathematical functions, prior to the onset of chaos. For the first time, this universal result enabled mathematicians to take their first steps to unravelling the apparently intractable "random" behavior of chaotic systems. This "ratio of convergence" is now known as the first Feigenbaum constant.

The Logistic map is a prominent example of the mappings that Feigenbaum studied in his noted 1978 article: Quantitative Universality for a Class of Nonlinear Transformations.

Feigenbaum's other contributions include important new fractal methods in cartography, starting when he was hired by Hammond to develop techniques to allow computers to assist in drawing maps. The introduction to the Hammond Atlas (1992) states:

"Using fractal geometry to describe natural forms such as coastlines, mathematical physicist Mitchell Feigenbaum developed software capable reconfiguring coastlines, borders, and mountain ranges to fit a multitude of map scales and projections. Dr. Feigenbaum also created a new computerized type placement program which places thousands of map labels in minutes, a task which previously required days of tedious labor."

In 1983 he was awarded a MacArthur Fellowship, and in 1986, he was awarded the Wolf Prize in Physics. He has been Toyota Professor at Rockefeller University since 1986.

• Chaos theory
• Fractal
• Logistic map
• Radial basis function
• Theory of Colours

• O'Connor, John J; Edmund F. Robertson "Mitchell Feigenbaum". MacTutor History of Mathematics archive.  
• Feigenbaum's webpage at Rockefeller