The role of directionality on the structure and dynamics of strongly anisotropic turbulent flows

Strong anisotropy in turbulent flows may be induced by body forces, Coriolis, buoyancy, Lorentz, and/or by large-scale gradients. These effects combined to the redistribution pressure terms are first identified by an angle dependence of the wave vector in Fourier space, the directionality. The resulting anisotropic structure is not taken into account in classical phenomenological theory, using essentially ‘isotropised’ dimensional analysis. Besides, it is generally hidden in practical engineering models by means of tuned constants, which may vary if the flow changes of nature. In this paper, different examples of anisotropic turbulence are revisited and compared to each other in order to shed light on fundamental aspects of this specific turbulence. To begin with, flows without energy production like rotating turbulence are considered. In this case, isotropy is broken by mean of third-order correlations in the equations. These correlations quantify the interscale energy transfer, and must be investigated at three-point, or triad by triad in Fourier space. This allows to account for the role of typical anisotropic frequency 2Ωcos θ _k , with θ _k the angle of the wave vector to the axis of rotation, and to simultaneously restore the role of phase coherence. We pursue the discussion with a second flow case, with production, quasi-static magnetohydrodynamics. This illustrates turbulence forced towards two-dimensional structure by an explicit Ohmic dissipation term. Linear dynamics displays an angle (called Moreau, or Shebalin) capable of reflecting the basic anisotropy in models as simple as . In the final phase of transition towards 2D structure, however, dynamics are essentially driven by third-order velocity correlations, and both successive linear and nonlinear phases yield counter-intuitive anisotropic results. The last case considered here is the turbulent mixing induced by a Rayleigh-Taylor instability. It is shown that anisotropy plays a central role in the dynamics of the mixing zone by means of an angular dimensionality parameter similar to the Moreau angle but for the density field, and appearing in a global model of buoyancy-drag equation.     

Dynamics of measurement-induced non-locality and geometric discord with initial system-environment correlations

We analyze the dynamics of geometric measure of discord （GMOD） and measurement-induced non-locality （MIN） in the presence of initial system-reservoir correlations without Born and Markov approximation. Although the initial system-environment states have the same reduced density matrices for both the system and environment, the effects of different initial system-environment correlations have been shown to fundamentally alter the time evolution of GMOD and MIN between two quantum systems in both Markovian and non-Markovian regimes. In general, both GMOD and MIN experience a sudden increase for initially quantum-correlated states, and a sudden decrease for classical-correlated states before they reach the same stationary values with initially factorized states.     

Chain folding and the structure of nylon 6.6 spherulites

Following the assignment of the 1329 and 1224 cm^?1 infrared bands to chain-folded conformations in nylon 6.6 by Koenig et al. examination of the infrared spectra of positively birefringent and negatively birefringent spherulitic films has been made. The spectra indicate extensive regular folding in negative spherulites but fewer folds or less regular folding in the positive spherulite structure.

The assignment of the infrared fold bands to modes of vibration of the repeat unit is discussed with reference to the spectra of films with varying extents of N deuteration (normal 6.6, disordered regions deuterated, N deutero 6.6, disordered regions hydrogenated).

Electron micrographs of negative spherulites are analyzed with the infrared and previous evidence. We suggest they are built up of single-crystal lamellae of 0.2 to 0.3 μ lateral dimensions packed with a preferential orientation of the lamellae planes parallel to the radial direction but otherwise randomly oriented.     

Large Deviations in Weakly Interacting Boundary Driven Lattice Gases

One-dimensional, boundary-driven lattice gases with local interactions are studied in the weakly interacting limit. The density profiles and the correlation functions are calculated to first order in the interaction strength for zero-range and short-range processes differing only in the specifics of the detailed-balance dynamics. Furthermore, the effective free-energy (large-deviation function) and the integrated current distribution are also found to this order. From the former, we find that the boundary drive generates long-range correlations only for the short-range dynamics while the latter provides support to an additivity principle recently proposed by Bodineau and Derrida.     

On familial longitudinal Poisson mixed models with gamma random effects

Poisson mixed models are used to analyze a wide variety of cluster count data. These models are commonly developed based on the assumption that the random effects have either the log-normal or the gamma distribution. Obtaining consistent as well as efficient estimates for the parameters involved in such Poisson mixed models has, however, proven to be difficult. Further problem gets mounted when the data are collected repeatedly from the individuals of the same cluster or family. In this paper, we introduce a generalized quasilikelihood approach to analyze the repeated familial data based on the familial structure caused by gamma random effects. This approach provides estimates of the regression parameters and the variance component of the random effects after taking the longitudinal correlations of the data into account. The estimators are consistent as well as highly efficient.     

Multiparticle azimuthal correlations

First observations of elliptic flow in Au-Au collisions at RHIC have been interpreted as evidence that the colliding system reaches thermal equilibrium. We discuss some of the arguments leading to this conclusion and show that a more accurate analysis is needed, which the standard flow analysis may not provide. We then present a new method of flow analysis, based on a systematic study of multiparticle azimuthal correlations. This method allows one to test quantitatively the collective behaviour of the interacting system. It has recently been applied by the STAR Collaboration at RHIC.     

Multiparticle correlations,entropy of partial distributions,and the direct variational method

In the classical statistical theory, multiparticle correlations are governed by a variational principle for a functional that becomes the thermodynamic potential on its extremal. We show that this functional contains a part that has the meaning of a sum of contributions from multiparticle entropies. We present a method for passing from the conditional variational problem for the thermodynamic potential to an unconditional one.Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 143, No. 1, pp. 150–160, April, 2005.     

Electron correlation effects in the presence of non-symmetry dictated nodes

We numerically study the effect of non-symmetry dictated nodes (NSDN) on electron correlation effects for spinless electrons. We find that repulsive interaction between electrons can enhance the overlap between nearest neighbors in the tight binding Hamiltonian, in the presence of NSDN. Normally, in the absence of NSDN, attractive interaction between electrons give such an effect and repulsive interaction gives the opposite effect.     

Comparisons of statistical multifragmentation and evaporation models for heavy-ion collisions

The results from ten statistical multifragmentation models have been compared with each other using selected experimental observables. Even though details in any single observable may differ, the general trends among models are similar. Thus, these models and similar ones are very good in providing important physics insights especially for general properties of the primary fragments and the multifragmentation process. Mean values and ratios of observables are also less sensitive to individual differences in the models. In addition to multifragmentation models, we have compared results from five commonly used evaporation codes. The fluctuations in isotope yield ratios are found to be a good indicator to evaluate the sequential decay implementation in the code. The systems and the observables studied here can be used as benchmarks for the development of statistical multifragmentation models and evaporation codes. An erratum to this article is available at .