| Co-Investigator(Kenkyū-buntansha) |
ORBACH R Univ.California Riverside, Dept.of Physics, Professor, リバーサイド校, 教授
OCIO M CEA Saclay, Service de Physique de l'Etat Condense, Chief Researcher, 凝縮系物理, 研究室長
CAMPBELL I Univ.Paris Sud, Physique des Solides, Professor, 固体物理研究所, 教授
ITO Atsuko Ochanomizu Univ., Dept.of Physics, Professor, 理学部, 教授 (20017180)
MIYAKO Yoshihiko Osaka Univ., Dept.of Earth and Space Science, Professor, 理学研究科, 教授 (10000837)
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| Research Abstract |
Aging phenomena in random systems with frustration, or complex systems, have been extensively investigated more than a decade. They are infinitely long-time relaxation processes to equilibrium (but in some systems to a state different from equilibrium). Researches on the phenomena are expected to open a new field in statistical physics and condensed matter physics, namely, the out-of -equilibrium dynamics in such complex systems. In the course of this program aging phenomena and their related slow dynamics in spin-glasses were mainly studied. We obtained various interesting findings which provide us deeper insights into one of the most fundamental ingredients of the complex system, i.e., its rugged free-energy landscape in phase space.
The main results obtained in this program are as follows.
1) Parisi's overlap distribution function, which describes theoretically the hierarchical structure in the rugged free-energy landscape of spin-glasses, was extracted experimentally for the first ti
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me by measuring aging phenomena followed after change of magnetic field (Orbach). 2) The characteristic differences between aging phenomena in cluster spin-glasses and those in ordinary spin-glasses were found experimentally (Ito). 3) Based on the results by large-scale simulations a unified scenario (named Growth of Quasi-Equilibrium Domain one), for aging phenomena in the SK model of finite sizes was proposed (Takayama). 4) By the simulations on aging phenomena in the 3D Heisenberg spin-glass model the results, which imply the existence of the chiral-glass transition, were obtained for the first time (Kawamura). 5) The non-universal feature of the spin-glass transition that critical nature depends on the type of distribution of random interactions was found by numerical simulations (Campbell). 6) Various interesting perceptron models for on-line learning were proposed and investigated (Nishimori). 7) In heavy electron system Ce(Ru_<1-x>Rh_x)_2Si_2 three ground states, Fermi liquid, non-Fermi liquid, and antiferromagnetic ones, were specified and the quantum phase transitions between them were analyzed experimentally (Miyako, Ocio). Less
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