Lambda-transition in liquid Helium, pp. 1116-7 in Physical Review Vol. 90, No. 6, June 15, 1953 [With:] Atomic theory of the lambda transition in Helium, pp. 1291-1301 [With:] Atomic theory of liquid Helium near absolute zero, pp. 1301-1309 in Physical Review Vol. 91, No. 6, September 15, 1953. [With:] Atomic theory of the two-fluid model of liquid Helium, pp. 262-77 in Physical Review Vol. 94, No. 2, April 15, 1954. FEYNMAN'S SOLUTION OF THE LIQUID HELIUM PROBLEM

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First editions of the papers which document Feynman's solution of the problem of superfluidity in liquid helium-4. The graph of specific heat v. temperature for He4 is shaped like a Greek letter lambda. Above the lambda He4 behaves like a normal fluid; below it He-4 is partly a normal fluid and partly a superfluid, which is able to flow with zero viscosity and exhibits other bizarre properties such as the ability to flow up the wall of containers, over the top, and down to the same level as the surface of the liquid inside the container. Superfluidity was discovered in 1937 by Pyotr Kapitsa, John F. Allen, and Don Misener. Lev Landau's phenomenological theory of superfluidity of helium-4 earned him the Nobel Prize in physics in 1962, but his theory does not elaborate on the microscopic structure of the superfluid component of liquid helium. "In 1950 Feynman left Cornell to join the faculty of the California Institute of Technology, where, except for a year in Brazil (1951-1952), he would spend the rest of his career. At Caltech he turned his attention to the problem of superfluidity in liquid helium. Russian theorist Lev Landau had shown that the remarkable ability of superfluid helium at low temperature to flow without resistance resulted from the fact that the liquid could take up energy from its surroundings only in certain very restricted ways. Feynman succeeded in tracing Landau's observation to its quantum mechanical roots. Feynman diagrams would later become an important research tool in this field, but Feynman did not use them to solve this problem. Instead he reverted to the old-fashioned Schrödinger formulation of quantum mechanics, using his remarkable intuition to guess the nature of a giant quantum system" (American National Biography). "The phenomenon of superfluidity had been discovered experimentally during the 1930s, and the great Russian theorist Lev Landau had provided a successful phenomenological description during the 1940s. While he greatly admired Landau's contributions to and successes in the field, Feynman pointed out several weaknesses in Landau's theory. Notably, Landau's quantum hydrodynamical approach treated Helium II as a continuous medium, which right from the beginning sacrificed the atomic structure of the liquid and thus forestalled the possibility of calculating the various characteristics of the system, such as the various parameters, on an atomic basis" (Mehra & Rechenberg, The Historical Development of Quantum Theory, Vol. 6, Part 2, p. 1160). "The main thrust of the first paper ['Lambda-transition in liquid Helium'] was to show that, despite interparticle interactions, liquid He4 did, by virtue of the symmetry of its [quantum] states, undergo a phase transition very much like the one experienced by an ideal Bose gas; in other words, the suggestion made by London in 1938 that the transition observed in this liquid might be a manifestation of Bose-Einstein condenstaion was basically correct. To demonstrate this, Feynman resorted to his space-time approach to quantum mechanics, and expressed the partition function of the liquid in the form of a path-integral" (Mehra, The Beat of a Different Drum, p. 364). "In his first paper on the 'Atomic theory of the lambda-transition in helium', he showed from first principles that, in spite of the large interatomic forces, liquid He4 should exhibit a transition analogous to the transition in an ideal gas (p. 1291). By writing the exact partition function as an integral over trajectories, using the space-time approach to quantum mechanics , Feynman could indeed derive a Landau-type energy spectrum [in 'Atomic theory of liquid Helium near absolute zero'] and further demonstrate phonon-like excitations evolve into roton-like ones at large momenta [in 'Atomic theory of the two fluid model of liquid helium'] (Mehra & Rechenberg). Three complete journal issues, large 8vo, original printed wrappers (slight chipping at ends of spines of 91/6 and 94/2). N° de ref. del artículo ABE-1612282972382

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