Exact solution of a drop-push model for percolation

Motivated by a computer science algorithm known as "linear probing with hashing," we study a new type of percolation model whose basic features include a sequential "dropping" of particles on a substrate followed by their transport via a "pushing" mechanism. Our exact solution in one dimension shows that, unlike the ordinary random percolation model, the drop-push model has nontrivial spatial correlations generated by the dynamics itself. The critical exponents in the drop-push model are also different from those of the ordinary percolation. The relevance of our results to computer science is pointed out.     

A first-order level-2 phase transition in thermodynamic formalism

We show the existence of a phase transition at the level of measures for the generalized dimension of the maximal entropy measure in a model that was considered by F. Hofbauer and which is related to a model of M. Fisher. The model presented here is related to the one-dimensional Ising model in which a wall effect is assumed. In this situation, the problem has to be considered in the one-dimensional lattice . In general there is no first-order transition for the Ising model in the lattice , but under our assumptions such transitions can occur. The Ising model has the purpose of explaining the magnetization of ferromagnetic systems at low temperatures. The main difference of our result from a previous result of F. Hofbauer is that the transition is analyzed in the setting of the generalized dimension. This setting is more closely related to the observables. The main purpose of this paper is to explain another mathematical model for phase transition using the mathematical results obtained by F. Hofbauer. We also use results of the thermodynamic formalism in an essential way.     

光电跟踪目标的强跟踪滤波算法及其仿真研究

针对光电武器对机动目标跟踪精度较差的问题,在"当前"统计模型的基础上,形成了机动目标"当前"统计模型下强跟踪滤波算法。该算法通过引入强跟踪滤波器的渐消因子,实时调节滤波器增益,增强了系统对突发机动目标的跟踪能力,同时保留了"当前"统计模型跟踪算法对一般机动目标跟踪精度高的特点。仿真结果表明,该算法对机动目标具有较好的跟踪精度和适中的计算复杂度,是一种较好的光电跟踪算法。     

A core-envelope massive distribution with a parabolic density distribution in the core

Tohnan's V solution has found wide application to the redshift problem in astrophysics but it has a drawback in that there is singularity at the centre. We have developed a core-envelope model with a parabolic density distribution in the core ande ^v r ²ⁿ in the envelope. The most distinctive feature of the model is that there is a continuity of all the four variables (E, P, andv) at the boundary. In other analytic coreenvelope models the continuity of only three variables is possible. This two-density structure has been used to model neutron stars and their mass, size and red shifts have been obtained.     

Soft Communities in Similarity Space

The \(\mathbb {S}^1\) model has been central in the development of the field of network geometry. It places nodes in a similarity space and connects them with a likelihood depending on an effective distance which combines similarity and popularity dimensions, with popularity directly related to the degrees of the nodes. The \(\mathbb {S}^1\) model has been mainly studied in its homogeneous regime, in which angular coordinates are independently and uniformly scattered on the circle. We now investigate if the model can generate networks with targeted topological features and soft communities, that is, inhomogeneous angular distributions. To that end, hidden degrees must depend on angular coordinates, and we propose a method to estimate them. We conclude that the model can be topologically invariant with respect to the soft-community structure. Our results expand the scope of the model beyond the independent hidden variables limit and can have an important impact in the embedding of real-world networks.     

Landau levels and Riemann zeros

The number N(E) of complex zeros of the Riemann zeta function with positive imaginary part less than E is the sum of a "smooth" function N[over ](E) and a "fluctuation." Berry and Keating have shown that the asymptotic expansion of N[over ](E) counts states of positive energy less than E in a "regularized" semiclassical model with classical Hamiltonian H=xp. For a different regularization, Connes has shown that it counts states "missing" from a continuum. Here we show how the "absorption spectrum" model of Connes emerges as the lowest Landau level limit of a specific quantum-mechanical model for a charged particle on a planar surface in an electric potential and uniform magnetic field. We suggest a role for the higher Landau levels in the fluctuation part of N(E).     

Breaking of permutation symmetry and diagonal group action: Nielsen model and the standard model as low-energy limit

We point out that, on the basis of a theorem by L. Michel, every model based on the symmetryG ... G has a generic low-energy limit the breaking to diagonal action, i.e., toG. This applies in particular to the proposal by Nielsen to consider such a model withG the standard model group.     

Binocular, Monocular and Dichoptic Pattern Masking

It has been reported that a quadratic summation rule can account for threshold versus masker contrast (TvC) functions for binocular, monocular and dichoptic masking. However, the present study suggests that inputs from two eyes are summed in different ways. Foleys model was revised to describe TvC functions for binocular, monocular and dichoptic masking. The revised model has the following two characteristics. First, the revised model receives two monocular inputs. Secondly, excitations and inhibitory signals are subjected to nonlinear transducer functions before and after summation of the monocular signals. A two-alternative forced-choice procedure was used to measure contrast thresholds for Gaussian windowed sine-wave gratings (target) in the presence of sine-wave gratings (masker). Thresholds were measured for 11 masker contrasts and the three masking conditions. It was shown that this revised model fitted the data resonably well. The revised model indicates how monocular inputs are summed in contrast processing.     

A Scalar Field as a Candidate for the Cosmological Non-baryonic Dark Matter

We present an up-to-date report on the status ofthe cosmological model based on a massive scalar fieldnon-minimally coupled to gravity, which has beenrecently used to explain the apparent periodicity in the distribution of galaxies, and as a modelfor the missing non-baryonic component of dark matter,within the standard inflationary scenario ( = 1).The model agrees with most cosmological observations, however local experiments can pose seriousconstraints that indicate the necessity of a slightlymodified model.     

"WHIMPERS" IN SELF-SIMILAR COSMOLOGIES

We examine how self-similarity influences the occurrence & nature of singularities in self-similar cosmologies. There exists a density divergence due to a conformal factor in any Self-similar model. If we discuss the singularity problem in an "unphysical" homogeneous model which is conformally related to the self-similar model, it is easy to show-that in a Class D model with -36/2, singularity bebaviour is similar to that in homogeneous comrologies; The Boyer-Ehlers analysis of Killing geodesicsic has been generalized to the self-similar case. Some new Penrosediagrams are given.     

Linewidth enhancement factor of wurtzite GaN/AlGaN quantum-well lasers with spontaneous polarization and piezoelectric effects

Spontaneous and piezoelectric polarization effects on the linewidth enhancement factor _e of (0001)-oriented wurtzite (WZ) GaN/AlGaN quantum-well (QW) lasers are investigated using a many-body self-consistent (MB-SC) model. The results are compared with those of a many-body flat-band (MB-FB) model and a free-carrier flat-band (FC-FB) model ignoring spontaneous and piezoelectric polarization. The MB-FB model shows a significant increase of _e at the peak gain position at high carrier densities compared to that of the FC-FB model. This is because the refractive index change at high carrier densities increases with the inclusion of the Coulomb enhancement effect. With the inclusion of the internal field, the differential gain and the differential index change (dg/dN and -d(n_e)/dN) are reduced compared to those for the MB-FB model, because the optical matrix elements of the MB-SC model decrease with the inclusion of the internal field. In the case of a well width of 30 Å, the MB-SC model has a smaller _e factor than that of the MB-FB model. On the other hand, in the case of a well width of 50 Å, the MB-SC model has a larger _e factor than that of the MB-FB model at a larger peak gain because the reduction rate of dg/dN is larger than that of -d(n_e)/dN for a larger peak gain. PACS 85.60.Bt; 85.30.De; 85.30.Vw; 78.20.Bh     

Formally Renormalizable Gravitationally Self-Interacting String Models

It has recently been shown how the effect of thedivergent part of the gravitational self-interaction fora classical string model in four dimensions can beallowed for by a renormalization of its stress-energy tensor and in the elastic case a correspondingrenormalization of the off-shell action. It is shownhere that that it is possible to construct a newcategory of elastic string models for which this effect is describable as a renormalization in thestricter formal sense, meaning that itonly requires a rescaling of one of the fixed parameterscharacterizing the model.     

Bound fermion states in the field of a soliton of the nonlinear O(3) σ model

The (2 + 1)-dimensional nonlinear O(3) σ model whose n field is coupled to the fermion field by the Yukawa interaction has been examined. The cases of the isosinglet and isodoublet fermion fields with respect to the internal symmetry group have been considered. It has been shown that bound states of the fermion in the n field of a soliton of the nonlinear O(3) σ model exist for some variants of the Yukawa interaction. The absence of zeroth fermion modes in the n field of the soliton has been established. The properties of the ground state of the fermion have been numerically studied. In particular, it has been shown that an increase in the spatial size of the soliton results in a decrease in the energy of the ground state. This leads to the instability of the soliton in a certain region of the parameters of the model.     

Ground states and flux configurations of the two-dimensional Falicov-Kimball model

The Falicov-Kimball model is a lattice model of itinerant spinless fermions (electrons) interacting by an on-site potential with classical particles (ions). We continue the investigations of the crystalline ground states that appear for various filling of electrons and ions for large coupling. We investigate the model for square as well as triangular lattices. New ground states are found and the effects of a magnetic flux on the structure of the phase diagram are studied. The flux phase problem where one has to find the optimal flux configurations and the nuclei configurations is also solved in some cases. Finally we consider a model where the fermions are replaced by hard-core bosons. This model also has crystalline ground states. Therefore their existence does not require the Pauli principle, but only the on-site hard-core constraint for the itinerant particles.     

The Gacs-Kurdyumov-Levin automaton revisited

We study a one-dimensional cellular automaton that was originally proposed as a candidate for exhibiting nonergodic behavior under noise. We prove that the deterministic model has the eroder property for two and only two invariant states. Moreover, we give the best possible estimates for the corresponding erosion times. We then review the results we have obtained from extensive computer simulations for the stochastic model and for a mixed model and argue that they suggest numerical and heuristic evidence in favour of ergodic behavior for all nonzero values of the noise parameter.     

Nonperturbative True Muonium on the Light Front with TMSWIFT

The true muonium \({(\mu\bar{\mu})}\) bound state presents an interesting test of light-cone quantization techniques. In addition to exhibiting the standard problems of handling non-perturbative calculations, true muonium requires correct treatment of \({e\bar{e}}\) Fock-state contributions. Having previously produced a crude model of true muonium using the method of iterated resolvents, our current work has focused on the inclusion of the box diagrams to improve the cutoff-dependent issues of the model. Further, a parallel computer code, TMSWIFT, allowing for smaller numerical uncertainties, has been developed. This work focuses on the current state of these efforts to develop a model of true muonium that is testable at near-term experiments.     

On the two-dimensional Coulomb gas

This is a sequel to a recent work of Gaudin, who studied the classical equilibrium statistical mechanics of the two-dimensional Coulomb gas on a lattice at a special value of the coupling constant such that the model is exactly solvable. This model is briefly reviewed, and it is shown that the correlation functions obey the sum rules that characterize a conductive phase. A related model in which the particles are constrained to move on an array of equidistant parallel lines has simpler mathematics, and the asymptotic behavior of its correlation functions is studied in some detail. In the low-density limit, the lattice model is expected to have the same properties as a system of charged, hard disks; the correlation functions, internal energy, and specific heat of the latter are discussed.this laboratory is associated with the Centre National de la Recherche Scientifique     

p-Spin model in finite dimensions and its relation to structural glasses

The p-spin spin-glass model has been studied extensively at mean-field level because of the insights which it provides into the mode-coupling approach to structural glasses and the nature of the glass transition. We demonstrate explicitly that the finite-dimensional version of the three-spin model is in the same universality class as an Ising spin glass in a magnetic field. Assuming that the droplet picture of Ising spin glasses is valid we discuss how this universality may provide insights into why structural glasses are either "fragile" or "strong."     

Dilatonic Dark Energy Model with Late Time de Sitter Attractor

Based on Weyl-scaled induced gravitational theory, we regard dilaton field in this theory as a candidate of dark energy. We construct a dilatonic dark energy model and its phantom model, that admit late time de Sitter attractor solution. When we take the potential of dilaton field as the form which has been studied in supergravity model and the famous Mexican hat potential , we show mathematically that these attractor solutions correspond to an equation of state ω = −1 and a cosmic density parameter Ω_σ = 1, which are important features for a dark energy model that can meet the current observations.     

A Color Appearance Model Applicable in Mesopic Vision

We propose a color vision model that can be used to predict color appearance in mesopic vision as well as photopic and scotopic vision. It is based on a two-stage model which consists of the cone and opponent stages and it assumes rod intrusion at the opponent stage. The model has the following features to describe the color appearance in mesopic vision. First, it includes a gradual and nonlinear shift in spectral luminous efficiency from V (LD) to V (LD) to cope with the spectral sensitivity difference between photopic and scotopic vision and the nonlinearity of rod influence on the luminance channel. Second, the model assumes decrease of the chromatic component with decreasing illuminance to explain the reduction of saturation at low illuminance levels. Third, it assumes that red/green and yellow/blue components change with illuminance levels independently, thus explaining hue shifts with decreasing illuminance. We applied the model for color appearance simulation of natural scenes in a mesopic visual environment.