Anomalous Diffusion In Microrheology: A Comparative Study

We present a comparative study on two theoretical descriptions of microrheological experiments. Using a generalized Langevin equation (GLE), we analyze the origin of the power-law behavior of the main properties of a viscoelastic medium. Then, we discuss the equivalence of the GLE with a generalized Fokker-Planck equation (GFPE), and how more general GFPE's can be derived from a thermo-kinetic formalism. These complementary theories lead to a justification for the physical nature of the Hurst exponent of fractional kinetics. Theory is compared with experiments.Comment: 7 pages, 3 figure

A FDR-preserving field theory for interacting Brownian particles: one-loop theory and MCT

We develop a field theoretical treatment of a model of interacting Brownian particles. We pay particular attention to the requirement of the time reversal invariance and the fluctuation-dissipation relationship (FDR). The method used is a modified version of the auxiliary field method due originally to Andreanov, Biroli and Lefevre [J. Stat. Mech. P07008 (2006)]. We recover the correct diffusion law when the interaction is dropped as well as the standard mode coupling equation in the one-loop order calculation for interacting Brownian particle systems.Comment: 66 pages, 8 figures, submitted to J. Stat. Mec

Critical fluctuations of time-dependent magnetization in a random-field Ising model

Cooperative behaviors near the disorder-induced critical point in a random field Ising model are numerically investigated by analyzing time-dependent magnetization in ordering processes from a special initial condition. We find that the intensity of fluctuations of time-dependent magnetization, $\chi(t)$, attains a maximum value at a time $t=\tau$ in a normal phase and that $\chi(\tau)$ and $\tau$ exhibit divergences near the disorder-induced critical point. Furthermore, spin configurations around the time $\tau$ are characterized by a length scale, which also exhibits a divergence near the critical point. We estimate the critical exponents that characterize these power-law divergences by using a finite-size scaling method.Comment: 5 pages, 7 figure

Event-Driven Simulation of the Dynamics of Hard Ellipsoids

We introduce a novel algorithm to perform event-driven simulations of hard rigid bodies of arbitrary shape, that relies on the evaluation of the geometric distance. In the case of a monodisperse system of uniaxial hard ellipsoids,we perform molecular dynamics simulations varying the aspect-ratio X0 and the packing fraction phi. We evaluate the translational Dtrans and the rotational Drot diffusion coefficient and the associated isodiffusivity lines in the phi-X0 plane. We observe a decoupling of the translational and rotational dynamics which generates an almost perpendicular crossing of the Dtrans and Drot isodiffusivity lines. While the self intermediate scattering function exhibits stretched relaxation, i.e. glassy dynamics, only for large phi and X0 about equals to 1, the second order orientational correlator C2(t) shows stretching only for large and small X0 values. We discuss these findings in the context of a possible pre-nematic order driven glass transition.Comment: Proceedings of IWCS2007 Sendai (Japan

Can the frequency-dependent specific heat be measured by thermal effusion methods?

It has recently been shown that plane-plate heat effusion methods devised for wide-frequency specific-heat spectroscopy do not give the isobaric specific heat, but rather the so-called longitudinal specific heat. Here it is shown that heat effusion in a spherical symmetric geometry also involves the longitudinal specific heat.Comment: Paper presented at the Fifth International Workshop on Complex Systems (Sendai, September, 2007), to appear in AIP Conference Proceeding

Numerical Investigation of Supersonic Hybrid Argon-Water-Stabilized Arc for Biomass Gasification

科研費報告書収録論文(課題番号:17206016/研究代表者:西山秀哉/プラズマ流動システムのマルチスケール統合化による最適制御)77

Fluctuation effects in the theory of microphase separation of diblock copolymers in the presence of an electric field

We generalize the Fredrickson-Helfand theory of the microphase separation in symmetric diblock copolymer melts by taking into account the influence of a time-independent homogeneous electric field on the composition fluctuations within the self-consistent Hartree approximation. We predict that electric fields suppress composition fluctuations, and consequently weaken the first-order transition. In the presence of an electric field the critical temperature of the order-disorder transition is shifted towards its mean-field value. The collective structure factor in the disordered phase becomes anisotropic in the presence of the electric field. Fluctuational modulations of the order parameter along the field direction are strongest suppressed. The latter is in accordance with the parallel orientation of the lamellae in the ordered state.Comment: 16 page