Violent Events in Superfluid Three-Helium and a Collective Model of Glasses

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A theoretical study will be carried out on various phenomena in superfluid helium-three in which the liquid is thrown violently out of thermal equilibrium and must then recover. In particular, in light of the recent discovery of Osheroff and Schiffer that a gamma ray scource is an efficient nucleator of the first order A to B transition, it is planned to elaborate the "baked Alaska" mechanism for nucleation of this transition by high energy electrons which was suggested earlier and to make detailed predictions of the dependence of the nucleation rate on temperature and on magnetic field. In addition, studies are planned of the nuclear magnetic resonance behavior in the highly supercooled A phase in low field, with a view to obtaining previously unavailable microscopic parameters of the liquid. It is also proposed to develop further a collective model of amorphous materials for explaining the remarkable quantitative universlaity of the thermal and acoustic properties of these materials at low temperatures. %%% Theoretical research will be conducted in two areas for which the Principal Investigator is the world leader: (1) research will continue on models for amorphous materials to explain the common properties that occur at very low temperatures among diverse materials; (2) work will continue on models for the violent behavior of helium at very low temperatures. This behavior has recently been observed and a theory, introduced earlier, will be further developed in light of these recent and exciting experimental discoveries.