Argentine mathematician Luis Caffarelli, 74 years old, born in Buenos Aires, continues to be absorbed in talking about a glass of ice. As the cubes melt, he explains enthusiastically, their edges round off, gradually creating a new world on that border between solid and liquid, a complicated universe with shifting energies and geometries. Caffarelli has been submerged in this type of microcosm for more than four decades and has managed to describe them mathematically, with increasing precision. That’s why he won this Wednesday the Abel Prize, considered the Nobel Prize of mathematics and endowed with 7.5 million Norwegian kroner (660,000 euros).

“You can’t get to the truth, but at least you can get closer to it, to the complexity of reality,” he says via videoconference from his home in the American city of Austin, where he has been researching for a quarter of a century at the University of Texas. . The Norwegian Academy of Sciences and Letters, which awards the prize, highlighted its “technically virtuous” results, especially on so-called free-boundary problems, such as mathematical models of what happens at the interface between water and sea. or an alloy of different molten metals that solidify at different rates. Caffarelli also shone when delving into the Navier-Stokes equations, which since 1845 describe the flow of a viscous fluid, such as oil. The applications of his work are incalculable: analyzing a person’s blood circulation, predicting the movement of oil, manufacturing an automobile engine, financial mathematics, refining the fundamental models that explain the universe.

Caffarelli received his doctorate from the University of Buenos Aires in 1972 and immediately emigrated to the United States on a scholarship, spending a decade at the mythical Institute for Advanced Studies in Princeton, where the German physicist Albert Einstein ended up fleeing the Nazis. “Mathematics linked to physics is the most interesting. I’m not much in favor of doing super-abstract research, which only half a dozen mathematicians can understand”, says the Argentine, closely linked to Spain and member of the scientific advisory committee of the Institute of Mathematical Sciences (ICMAT), in Madrid.

The researcher promoted a successful mathematics summer school with Ernest Luch

The researcher remembers that his first visit to the Spanish capital was in 1984, in the midst of a countercultural explosion after the Franco regime, although his interests were different. “The Madrid scene wasn’t as important as Madrid food,” he jokes. Caffarelli exposed the interactions between solids and liquids with the help of Spanish colleagues such as Antonio Córdoba, Ireneo Peral and Juan Luis Vázquez. Córdoba, former director of ICMAT, describes the Argentinian’s contributions in the field of partial differential equations as “classic and revolutionary”, tools used in the mathematical description of the physical world that is the protagonist of everyday life, such as fluids in motion. The Porteño is the first Latin American to win the Abel Prize, an award established in 2002 by the Norwegian government to fill the mathematical void of the Nobels.

Caffarelli and Córdoba met another Spaniard at Princeton, the economist Ernest Lluch, the father of universal public health in Spain —as a minister in the first socialist government— and later rector of the Universidad Internacional Menéndez Pelayo. The three conceived a successful summer school of mathematics at the Palacio de la Magdalena in Santander, which ended when the terrorist group ETA shot Ernest Lluch twice in the head in his garage on November 21, 2000. Córdoba recalls that Caffarelli came to bought land in the mountains of Madrid, in Soto del Real, to build a house with his wife, the also brilliant mathematician Irene Martínez Gamba. Ultimately, the couple stayed in the United States.

The Argentine researcher remembers that time with nostalgia. “Madrid was, scientifically, one of the most interesting places, maybe because it was a combination of doing math and the very friendly life we ​​had between us. Speaking the same language made deep scientific discussions much easier,” he recalls. Caffarelli has spent entire quarters in Madrid since the 1980s, but he never finished with a glass of ice after his mathematical days. “If you want to drink, in Spain you drink good wine”, he comments with a laugh.

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