Study of non-equilibrium effects and thermal properties of heavy ion collisions using a covariant approach

Non-equilibrium effects are studied using a full Lorentz-invariant formalism. Our analysis shows that in reactions considered here, no global or local equilibrium is reached. The heavier masses are found to be equilibrated more than the lighter systems. The local temperature is extracted using hot Thomas Fermi formalism generalized for the case of two interpenetrating pieces of nuclear matter. The temperature is found to vary linearly with bombarding energy and impact parameter whereas it is nearly independent of the mass of the colliding nuclei. This indicates that the study of temperature with medium size nuclei is also reliable. The maximum temperatures obtained in our approach are in a nice agreement with earlier calculations of other approaches. A simple parametrization of maximal temperature as a function of the bombarding energy is also given.Comment: LaTex-file, 17 pages, 8 figures (available upon request), Journal of Physics G20 (1994) 181

Surface-Directed Spinodal Decomposition in Binary Fluid Mixtures

We consider the phase separation of binary fluids in contact with a surface which is preferentially wetted by one of the components of the mixture. We review the results available for this problem and present new numerical results obtained using a mesoscopic-level simulation technique for the 3-dimensional problem.Comment: RevTeX, 7 figure

Scaling Behavior of Response Functions in the Coarsening Dynamics of Disordered Ferromagnets

We study coarsening dynamics in the ferromagnetic random bond Ising model in d = 1; 2. We focus on the validity of super-universality and the scaling properties of the response functions. In the d = 1 case, we obtain a complete understanding of the evolution, from pre- asymptotic to asymptotic behavior. The corresponding response function shows a clear violation of super-universality. Further, our results for d = 1; 2 settle the controversy regarding the decay exponent which characterizes the response function

Crossover in Growth Law and Violation of Superuniversality in the Random Field Ising Model

We study the nonconserved phase ordering dynamics of the d = 2, 3 random field Ising model, quenched to below the critical temperature. Motivated by the puzzling results of previous work in two and three di- mensions, reporting a crossover from power-law to logarithmic growth, together with superuniversal behavior of the correlation function, we have undertaken a careful investigation of both the domain growth law and the autocorrelation function. Our main results are as follows: We confirm the crossover to asymptotic logarithmic behavior in the growth law, but, at variance with previous findings, the exponent in the preasymptotic power law is disorder-dependent, rather than being the one of the pure system. Furthermore, we find that the autocorre- lation function does not display superuniversal behavior. This restores consistency with previous results for the d = 1 system, and fits nicely into the unifying scaling scheme we have recently proposed in the study of the random bond Ising model.Comment: To be published in Physical Review

Amplification of Fluctuations in Unstable Systems with Disorder

We study the early-stage kinetics of thermodynamically unstable systems with quenched disorder. We show analytically that the growth of initial fluctuations is amplified by the presence of disorder. This is confirmed by numerical simulations of morphological phase separation (MPS) in thin liquid films and spinodal decomposition (SD) in binary mixtures. We also discuss the experimental implications of our results.Comment: 15 pages, 4 figure

Complex Chebyshev polynomials and generalizations with an application to the optimal choice of interpolating knots in complex planar splines

AbstractThis paper contains a brief account on complex planar splines which are complex valued functions defined piecewise on a grid. For noncontinuous (so called nonconforming) splines the problem of the placement of knots at which these splines are required to be continuous is investigated. It is shown that this problem reduces to finding complex Chebyshev polynomials under the additional requirement that the zeros of the polynomials are on the boundary of the corresponding domains. It is proved that the zeros of a generalized Chebyshev polynomial are in the convex hull of the domain on which the Chebyshev polynomials are defined. Some open problems are stated. A numerical and graphical display for the optimal location of three and six points on certain triangles is provided

Mirrorless optical bistability in a nonlinear absorbing dielectric film

The optical transmissivity of a mirrorless, nonlinear, absorbing dielectric thin film is investigated numerically. The dielectric function in the film region is dependent on the intensity of the electromagnetic field. Multivalued solutions of transmissivity as a function of incident power are calculated for the steady-state wave equation. The numerical solution is applied to two different model dielectric functions. As the absorption parameter is increased, larger values of incident intensity are required to switch the systems between stable output states. Also, the peak values of transmissivity are reduced as the absorption is increased