Fit Regions and Contact Interactions
In 1985, during his stay in Pisa, Italy, Walter Noll made his first contact with Epifanio G. Virga, who later became his most important collaborator after B.D. Coleman and H.D. Dombrowski [15.1]. In October-November 1985, Virga was staying at the Department of Mathematics of the Carnegie-Mellon University on the invitation of Professor W.O. Williams. He was working at that time on a paper devoted to the “unstable equilibrium configurations of fluids which were not removed by strengthening surface tension” [15.2]. Williams offered Virga an opportunity to speak on his research at a department colloquium. Virga remembered: “Walter (Noll) was in the audience. After the talk he said to me that he had attempted to find the simplest class of sets which would form a ‘material universe’ according to his definition of 1959, but he was stuck in some difficulties with sets of finite perimeter. He ended by proposing to work together on the problem. I was happy to accept” [15.3]. Noll and Virga collaborated first in Pittsburgh until the end of Virga’s stay. They continued by correspondence. However, the problem was too difficult for them both. Noll could not read in Italian the works of Ennio De Giorgi on sets with finite perimeter, which were of immense importance for their work. On the other hand, Virga was only a “beginner” at that time, as he wrote himself, and, obviously, he was insufficiently qualified to help him.
KeywordsManifold Clarification Verse
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