Time dependence of the survival probability of an opinion in a closed community

The time dependence of the survival probability of an opinion in a closed community has been investigated in accordance with social temperature by using the Kawasaki-exchange dynamics based on previous study in Ref. [1]. It is shown that the survival probability of opinion decays with stretched exponential law consistent with previous static model. However, the crossover regime in the decay of the survival probability has been observed in this dynamic model unlike previous model. The decay characteristics of both two regimes obey to stretched exponential.Comment: Revised version of the paper (9 page, 5 Figures). Submitted to Int. J. Mod. Phys.

An Experimental and Theoretical Investigation of the Skeletal Frequencies of the Paraffin Hydrocarbons and the Far Infra‐Red Spectrum of Carbon Tetrachloride

The far infra‐red spectra of the paraffin hydrocarbons and of carbon tetrachloride have been investigated. The following bands were located: propane at 370.6 cm−1, n‐butane at 215 cm−1, and carbon tetrachloride at 315 cm−1, the latter showing isotope structure. The contours of the following near infra‐red bands for n‐butane were surveyed, and some fine structure was revealed: 1342.9 cm−1, 1295.6 cm−1, 1135.6 cm−1, 956.5 cm−1, and 740.0 cm−1. The assignment of the skeletal frequencies of vibration is made, and a theoretical analysis of the skeletal normal frequencies, assuming a valence potential for the molecules propane through pentane, is given.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/71089/2/JCPSA6-17-4-393-1.pd

The Infra‐Red Absorption Spectrum of Propane

Of the twenty‐seven internal degrees of freedom of propane, all nondegenerate, twenty‐two may appear as fundamental absorption bands. These bands fall into three symmetry classes, designated A1, B1 and B2, and distinguishable by their characteristic contours. Because of overlapping, however, it is impossible in many cases to determine their positions precisely. This is especially true in the regions of the C☒H valence and deformation frequencies. Some ten or twelve fundamental bands may be identified with confidence as well as a number of combinations. An A1 band at 870 cm—1 and a B2 band at 748 cm—1 have been partially resolved, the line spacing being about 1.47 cm—1 in agreement with predictions based upon electron diffraction measurements. The fine structure of the B1 bands has not been observed (the predicted spacing is 0.5 cm—1) but the interval between maxima of the P and R branches is approximately 26 cm—1 as expected. With 24 cm‐atmospheres of gas no bands were observed between 15μ and 35μ, although the symmetrical C☒C deformation might be expected to produce a band of appreciable intensity within these limits. This frequency has apparently been observed in Raman spectra at 375 cm—1.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70815/2/JCPSA6-9-7-487-1.pd

A Hybrid model for the origin of photoluminescence from Ge nanocrystals in SiO2_2 matrix

In spite of several articles, the origin of visible luminescence from germanium nanocrystals in SiO$_2$ matrix is controversial even today. Some authors attribute the luminescence to quantum confinement of charge carriers in these nanocrystals. On the other hand, surface or defect states formed during the growth process, have also been proposed as the source of luminescence in this system. We have addressed this long standing query by simultaneous photoluminescence and Raman measurements on germanium nanocrystals embedded in SiO$_2$ matrix, grown by two different techniques: (i) low energy ion-implantation and (ii) atom beam sputtering. Along with our own experimental observations, we have summarized relevant information available in the literature and proposed a \emph{Hybrid Model} to explain the visible photoluminescence from nanocrystalline germanium in SiO$_2$ matrix.Comment: 23 pages, 8 figure

Anomalous Rotational Relaxation: A Fractional Fokker-Planck Equation Approach

In this study we obtained analytically relaxation function in terms of rotational correlation functions based on Brownian motion for complex disordered systems in a stochastic framework. We found out that rotational relaxation function has a fractional form for complex disordered systems, which indicates relaxation has non-exponential character obeys to Kohlrausch-William-Watts law, following the Mittag-Leffler decay.Comment: Revtex4, 9 pages. Paper was revised. References adde

Relaxation properties in a lattice gas model with asymmetrical particles

We study the relaxation process in a two-dimensional lattice gas model, where the interactions come from the excluded volume. In this model particles have three arms with an asymmetrical shape, which results in geometrical frustration that inhibits full packing. A dynamical crossover is found at the arm percolation of the particles, from a dynamical behavior characterized by a single step relaxation above the transition, to a two-step decay below it. Relaxation functions of the self-part of density fluctuations are well fitted by a stretched exponential form, with a $\beta$ exponent decreasing when the temperature is lowered until the percolation transition is reached, and constant below it. The structural arrest of the model seems to happen only at the maximum density of the model, where both the inverse diffusivity and the relaxation time of density fluctuations diverge with a power law. The dynamical non linear susceptibility, defined as the fluctuations of the self-overlap autocorrelation, exhibits a peak at some characteristic time, which seems to diverge at the maximum density as well.Comment: 7 pages and 9 figure

Stretched-exponential decay functions from a self-consistent model of dielectric relaxation

There are many materials whose dielectric properties are described by a stretched exponential, the so-called Kohlrausch-Williams-Watts (KWW) relaxation function. Its physical origin and statistical-mechanical foundation have been a matter of debate in the literature. In this paper we suggest a model of dielectric relaxation, which naturally leads to a stretched exponential decay function. Some essential characteristics of the underlying charge conduction mechanisms are considered. A kinetic description of the relaxation and charge transport processes is proposed in terms of equations with time-fractional derivatives.Comment: 17 page

Nonequilibrium dynamics of urn models

Dynamical urn models, such as the Ehrenfest model, have played an important role in the early days of statistical mechanics. Dynamical many-urn models generalize the former models in two respects: the number of urns is macroscopic, and thermal effects are included. These many-urn models are exactly solvable in the mean-field geometry. They allow analytical investigations of the characteristic features of nonequilibrium dynamics referred to as aging, including the scaling of correlation and response functions in the two-time plane and the violation of the fluctuation-dissipation theorem. This review paper contains a general presentation of these models, as well as a more detailed description of two dynamical urn models, the backgammon model and the zeta urn model.Comment: 15 pages. Contribution to the Proceedings of the ESF SPHINX meeting `Glassy behaviour of kinetically constrained models' (Barcelona, March 22-25, 2001). To appear in a special issue of J. Phys. Cond. Mat

Electronic transport in field-effect transistors of sexithiophene

The electronic conduction of thin-film field-effect-transistors (FETs) of sexithiophene was studied. In most cases the transfer curves deviate from standard FET theory; they are not linear, but follow a power law instead. These results are compared to conduction models of "variable-range hopping" and "multi-trap-and-release". The accompanying IV curves follow a Poole-Frenkel (exponential) dependence on the drain voltage. The results are explained assuming a huge density of traps. Below 200 K, the activation energy for conduction was found to be ca. 0.17 eV. The activation energies of the mobility follow the Meyer-Neldel rule. A sharp transition is seen in the behavior of the devices at around 200 K. The difference in behavior of a micro-FET and a submicron FET is shown. (C) 2004 American Institute of Physics

Correlation and response in the Backgammon model: the Ehrenfest legacy

We pursue our investigation of the non-equilibrium dynamics of the Backgammon model, a dynamical urn model which exhibits aging and glassy behavior at low temperature. We present an analytical study of the scaling behavior of the local correlation and response functions of the density fluctuations of the model, and of the associated fluctuation- dissipation ratios, throughout the alpha regime of low temperatures and long times. This analysis includes the aging regime, the convergence to equilibrium, sand the crossover behavior between them.Comment: 30 pages, 2 figures. To appear in Journal of Physics