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Leprince-Ringuet and experimental physics


Gaston Maurice Julia
Benoît Mandelbrot Mathematician
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Julia was a very different person. He was much younger than Paul Levy and very much a southerner. He spoke with a loud voice and big gestures. He had been wounded during World War I very badly and his nose and half his cheek were missing so he wore a leather mask. The first day it was very, very odd. One only looked at his mask. After a few meetings, one forgot. Julia wanted to establish some contact with students but didn't know how, and besides he came in the period of his life where he did not have any interest for the course. Paul Levy was rewriting his a little bit every year to make it more perfect and, perhaps, more obscure. Julia was taking chunks of one course, chunks of another course and stacking them together. It was a much less inspiring course than Paul Levy's. Also my uncle had a combination of extreme admiration for Julia's works of the 1910s and 1920s, but a very bad personal relation with the man, which is another story I may come to later. But I never thought I would have anything to do with Julia. I was convinced that Julia was representative of a very long forgotten past, dying kind of mathematics and that whatever I would do I would not be concerned with that. Did you learn about Julia sets at this time? No, I only knew Julia as a professor. It was several years later, after my return from Caltech when I was looking for a Ph.D. topic, that my uncle told me that I should read Julia's great masterpiece of 1917 and that I became aware of it. I knew of Julia as being a great mathematician in a kind of old-fashioned fashion, as early at the École Polytechnique.

Benoît Mandelbrot (1924-2010) discovered his ability to think about mathematics in images while working with the French Resistance during the Second World War, and is famous for his work on fractal geometry - the maths of the shapes found in nature.

Listeners: Daniel Zajdenweber Bernard Sapoval

Daniel Zajdenweber is a Professor at the College of Economics, University of Paris.

Bernard Sapoval is Research Director at C.N.R.S. Since 1983 his work has focused on the physics of fractals and irregular systems and structures and properties in general. The main themes are the fractal structure of diffusion fronts, the concept of percolation in a gradient, random walks in a probability gradient as a method to calculate the threshold of percolation in two dimensions, the concept of intercalation and invasion noise, observed, for example, in the absorbance of a liquid in a porous substance, prediction of the fractal dimension of certain corrosion figures, the possibility of increasing sharpness in fuzzy images by a numerical analysis using the concept of percolation in a gradient, calculation of the way a fractal model will respond to external stimulus and the correspondence between the electrochemical response of an irregular electrode and the absorbance of a membrane of the same geometry.

Duration: 2 minutes, 3 seconds

Date story recorded: May 1998

Date story went live: 24 January 2008