Transition and Dynamics in Complex Systems

点击翻译按钮获取中文摘要

In the course of the project several members and their collaborators were individually exchanged between the two countries (France and US) and Japan. The two workshops were held ; one on October 17-18,1994 at University of Tsukuba, and the other entitled "Physics of Frustrated Systems" on December 4-6,1995 at CEA-Saclay. Below we briefly describe the main results obtained by the project.1) Transitions and Dynamics in spin glasses (SG's) : By the computational method Takayama has shown that slow dynamics in the 'Griffiths phase' consists of two processes, ordinary critical dynamics and cluster dynamics, while Campbell has pointed out a non-universal nature of Ising SG's. Ito has observed a divergent bahavior in the nonlinear susceptibility at the reentrant transition point to the mixed phase.2) Aging Phenomena in SG's in Magnetic Fields : Ocio has found a universal scaling form for the time development of TRM and IRM including their waiting time dependence, while Orbach has proposed a way to extract the overlap function P (q) from the observed aging phenomena.3) Phase Dynamics in Granular (Ceramic) Superconductors : From the measurement on 1/f noise Ocio has pointed out a possible existence of pi-junction, and Kawamura has developed a theory of the random freezing of 'chiralities' in these systems.4) Heavy Electron Systems Ce (Ru_<0.85>Rh_<0.15>)_2Si_2 : In this material Miyako has observed the crossover from the high-T localized spin state to the low-T heavy electron state, and then to the spin-density wave (SDW) phase associated with the INVAR effect.5) SDW Dynamics in (TMTSF)_2PF_6 : Clark has found that the repining process of SDW is governed by thermally excited quasi-particles at high T,but by their quantum tunneling at low T.6) General Theory for Phase Transitions : Suzuki has developed general theories, such as the 'decomposition of exponential operators', and has applied them to various systems with exotic phase transitions.