Energy basis via decoherence

The question of the emergence of a preferred basis which is generally understood as that basis in which the reduced density matrix is driven to a diagonal (classically interpretable) form via environment induced decoherence is addressed. The exact solutions of the Caldeira-Leggett Master Equation are analyzed for a free particle and a harmonic oscillator system. In both cases, we see that the reduced density matrix is driven diagonal in the energy basis, which is momentum for the free particle and the number states for the harmonic oscillator. This seems to single out the energy basis as the preferred basis which is contrary to the general notion that it is the position basis which is selected since the coupling to the environment is via the position coordinates     

Fast fission phenomena: A possible intermediate time scale between deep inelastic reactions and compound nucleus formation

The change of the FWHM of the mass distribution of the fission products as a function of angular momentum is interpreted as a signature for a mechanism which is intermediate between compound nucleus formation and deep inelastic reactions. An intermediate composite system is assumed to be formed during the reaction, which undergoes fission. This kind of mechanism can therefore be called fast fission phenomena. It is related to the existence of a long lifetime component in déep inelastic reactions. Within the framework of a simple statistical model a qualitative as well as a quantitative estimate is done for a particular system. The conditions under which such a mechanism can be observed are discussed.     

On the theory of electronic correlations in solids

A formalism is presented for the computation of long range as well as short range correlations in the electronic ground state of a solid. It is based on a Local Approach to the correlation problem which was successfully tested before for small molecules. The method connects two approaches to the correlation problem. One is that of the RPA which is often applied in solid state physics and describes the long range aspects of the correlated electronic motions. The other is that of quantum chemistry which tries to calculate to high accuracy the short range part of the correlation problem. The method is variational in nature. The approximations which have been made exclude the application of the present formalism to strongly correlated systems such as valence fluctuating systems.     

Disassembly of an excited nuclear aggregate through sequential decay

The disassembly of an excited nuclear aggregate is described as a time-dependent decay process in which clusters are continuously and sequentially emitted by the primitive aggregate and those which have already been formed at a given time. The dynamics describe the rate at which the different species are generated as well as the rate at which the system de-excites and expands isotropically in space. The model is applied to the study of sequentially decaying⁴⁰Ar as a function of the initial excitation energy.     

The effect of compound states on collective-state singularities in the optical potential

From an exact form of the self-energy of a nucleon in a nucleus, which is equivalent to the optical potential, two approximation schemes, which are both based on a weak-coupling picture, are presented. They lead to expressions which can be interpreted physically as the coupling of a dressed single-particle (single-hole) state to the exact particle-hole (particle-particle) propagator. The residues of the many poles of the self-energy are divided into two categories: (i) residues which are distributed statistically, and (ii) residues which vary systematically. The first set is interpreted as compound nuclear structure and its influence on the single particle motion is investigated. The second set leads to intermediate structure. This structure is further investigated within an extension of the random phase approximation where all particle and hole lines are dressed by compound nuclear effects. In this way the spreading width of intermediate resonances, which is found to be the imaginary part of the pole position in the self-energy, is calculated. The escape width for these resonances is obtained by solving the Lippmann-Schwinger equation in which the calculated self-energy appears. This width depends on the structure of the continuum as well as on the residues of the poles of the self-energy. It is shown that these residues are complex, one of the reasons for this being that corrections to the vertex for the excitation of a collective state, appear. The similarity between the complex form factors introduced in the macroscopic model for inelastic scattering and the complex vertex functions above, is discussed. It is also pointed out that the results obtained here may be used in a phenomenological analysis.     

单一亚波长孔径增强透射效应的传输线模型

为了研究亚波长孔径的增强透射效应,把传输线理论引入到了单一亚波长金属孔径的增强光学透射效应中。把金属孔径看成传输线,将电流在传输线上的传输和类Fabry-Pérot腔联系起来;把孔径的出射面看成是传输线的输出端,将出射面的电流看成是一种局域的衰逝电流,电流经传输线在传输线的输出端以天线辐射的形式辐射电磁波。解释了孔径透射的近场分布问题、孔径增强透射峰的位置问题和透射峰位置随金属板厚度的红移问题,得到了与其它理论和实验一致的结果,对开发基于增强透射的亚波长元件具有重要的参考价值。     

Physical models of cognition

This paper presents and discusses physical models for simulating some aspects of neural intelligence, and, in particular, the process of cognition. The main departure from the classical approach here is in utilization of a terminal version of classical dynamics introduced by the author earlier. Based upon violations of the Lipschitz condition at equilibrium points, terminal dynamics attains two new fundamental properties: it is spontaneous and nondeterministic. Special attention is focused on terminal neurodynamics as a particular architecture of terminal dynamics which is suitable for modeling of information flows. Terminal neurodynamics possesses a well-organized probabilistic structure which can be analytically predicted, prescribed, and controlled, and therefore which presents a powerful tool for modeling real-life uncertainties. Two basic phenomena associated with random behavior of neurodynamic solutions are exploited. The first one is a stochastic attractor—a stable stationary stochastic process to which random solutions of a closed system converge. As a model of the cognition process, a stochastic attractor can be viewed as a universal tool for generalization and formation of classes of patterns. The concept of stochastic attractor is applied to model a collective brain paradigm explaining coordination between simple units of intelligence which perform a collective task without direct exchange of information. The second fundamental phenomenon discussed is terminal chaos which occurs in open systems. Applications of terminal chaos to information fusion as well as to explanation and modeling of coordination among neurons in biological systems are discussed. It should be emphasized that all the models of terminal neurodynamics are implementable in analog devices, which means that all the cognition processes discussed in the paper are reducible to the laws of Newtonian mechanics.     

On the origin of the so called conical emission in laser pulse propagation in atomic vapor

Propagation in Na vapor of a near resonant pulse from a single mode tunable dye laser is shown to produce, among other effects, a forward coherent, broadband (0.2 nm) scattering with two apparent spectral maxima which can be observed for both detuning sides of the laser frequency with respect to the atomic frequency. The spectral angular distribution of the scattering is studied. The origin of the broadening is suggested to be a combination of stimulated Raman scattering and self phase modulation. It is proposed that the red wing of this emission, which was previously observed only in a ring (and often referred to as “the conical emission”) can be interpreted, as well as the new observation reported here, as part of a more general process involving reabsorption of the generated near resonant broadband which, because of self lensing processes, is angularly dispersed.     

Conformal scalar propagation and Hawking radiation

The construction of the conformal scalar propagator which has been obtained in the preceding two projects as an analytic function of the Schwarzschild black-hole space-time is completed with a boundary condition imposed by the physical context through contour integration in the exterior vicinity of the event horizon. It is shown that, as a consequence of the semi-classical character which the emitted quanta have in that exterior vicinity, the particle production by the Schwarzschild black hole which was formally established in the preceding project is identical to thermal Hawking radiation. By extension, it is established that such a particle production corresponds to a spectrum which detracts from thermality by the amount predicted by Parikh and Wilczek if energy conservation is properly imposed as a constraint on scalar propagation. The results obtained herein support the case made by Hawking on the relation between quantum propagation and observation of particles produced by a black hole.     

Synchronization of an ensemble of oscillators regulated by their spatial movement

Synchronization for a collection of oscillators residing in a finite two dimensional plane is explored. The coupling between any two oscillators in this array is unidirectional, viz., master-slave configuration. Initially the oscillators are distributed randomly in space and their autonomous time-periods follow a Gaussian distribution. The duty cycles of these oscillators, which work under an on-off scenario, are normally distributed as well. It is realized that random hopping of oscillators is a necessary condition for observing global synchronization in this ensemble of oscillators. Global synchronization in the context of the present work is defined as the state in which all the oscillators are rendered identical. Furthermore, there exists an optimal amplitude of random hopping for which the attainment of this global synchronization is the fastest. The present work is deemed to be of relevance to the synchronization phenomena exhibited by pulse coupled oscillators such as a collection of fireflies.     

三维成像中相位级次自编码的相位测量方法

提出一种相位级次自编码技术的相位测量方法.与传统的相位测量技术不同,该方法利用截断相位的微分值作为编码通道,完成对各条纹级次的编码.构造的代码序列总长度为投影条纹的周期数,每个周期作为一个码元,由相邻若干码元构成一个代码子序列.相位计算后,根据截断相位的微分信息,可以提取出各周期及其码元值,通过在设计的代码序列中进行代...     

Hamilton-Jacobi expansion of the scattering amplitude

The calculation of the scattering amplitude is reduced to the problem of solving a set of classical Hamilton-Jacobi equations. This allows one to incorporate classical intuition into approximations at a fundamental level. The result is actually an iterative expansion for the scattering amplitude which is expected to be convergent in the high-energy limit. The first term in the expansion is shown to be the Glauber approximation, which is an approximation used extensively in nuclear as well as atomic and particle physics.     

Spin-reorientational phase transition in the basal plane in an α-Fe2O3: (Ga, Dy) crystal

A spin-reorientational phase transition in the basal plane, which was experimentally observed earlier, is explained in terms of a model in which the crystalline Fe-ion matrix is considered as a continuum, while dopant Dy ions are treated as quasi-Ising ions. The transition is established to be due to the Fe-subsystem anisotropy competing with that of the rare-earth subsystem.     

A general surface-treatment-free approach to fabrication of alignment layers using a super-aligned carbon nanotube film template

<正>We develop a general approach to the fabrication of films with unidirectional grooves,such as silicon nitride, silicon dioxide and aluminium oxide,in which the surface is not required to be treated.Super-aligned carbon nanotube (SACNT) film may be used as a template and as sacrificial layer,which is subsequently removed by heating in an atmosphere of air.The unidirectional morphology of the SACNT film turns into a desired film,which is found to possess the ability to align liquid crystal molecules.This approach also features high efficiency,low cost and easy scaling-up for mass production.     

The dispersion and matching characteristics of the helicalresonator plasma source

The dispersion characteristics and the fields of a helical resonator are obtained. The coil is approximated by a helical current layer with infinite conductivity along the current direction (a “sheath helix”). The plasma column is modeled as a cylindrical dielectric in which the dielectric losses can be neglected in determining the propagation properties of the resonator. Assuming the plasma losses are known, the model can be used to study the matching of the helical resonator to an external power source which is connected to the helix by a tap. The resonator is modeled as a parallel connection of two transmission line segments on each side of the tap position. We determine the efficiency of power transfer to the resonator as a function of the tap position driving frequency, and plasma loading. We find that whereas for a small plasma loading it is possible to achieve perfect matching, there exists a critical value of plasma loading beyond which a perfect match is no longer possible     

Flow-induced beam steering in a single laser hot spot

The transmitted angular distribution of a 527 nm nearly diffraction-limited laser is measured after it propagates through a plasma with supersonic transverse flow. The laser beam is deflected by as much as 10 degrees and exhibits bowlike features in the flow direction, which is attributed to flow-induced beam steering. The finite interaction volume allows for direct comparison with a 3D hydrodynamic simulation, which is in good agreement with details of the experiment.     

Heat conduction and Fourier's law by consecutive local mixing and thermalization

We present a first-principles study of heat conduction in a class of models which exhibit a new multistep local thermalization mechanism which gives rise to Fourier's law. Local thermalization in our models occurs as the result of binary collisions among locally confined gas particles. We explore the conditions under which relaxation to local equilibrium, which involves no energy exchange, takes place on time scales shorter than that of the binary collisions which induce local thermalization. The role of this mechanism in multiphase material systems such as aerogels is discussed.     

Self-oscillations in a hybrid bistable optical device

The Van der Pol, Krylov-Bogoliubov method for self-oscillation calculations in nonlinear systems is applied to a piezoelectrically driven Fabry-Perot interferometer which is operated as a hybrid bistable optical device. It is shown that in cases where the time delay in the feedback signal cannot be ignored, or when a reactive element is inserted in the appropriate place in the electrical circuit, self-oscillation will result. Experiments in which a piezoelectric element serves as the basic component of a hybrid bistable device demonstrate that self-oscillation occurs with a frequency which is very near the piezoelement self-frequency.     

Temperature dependence of indirect-exciton luminescence in in-plane magnetic field

We report on a magneto-luminescence on a double quantum well subject to an in-plane magnetic field. The attention is paid to the properties of interwell excitons, which are indirect in the real space and which become indirect in the reciprocal space as well when a finite in-plane magnetic field is applied. Such indirect exciton states become optically inactive unless some relaxation mechanisms of their momentum appear. The experiment is carried out on a sample where, as reported previously, the radiative recombination of indirect excitons is possible due to their localization or via collisions with structural defects. The experimental data presented here, measured at various temperatures, favour the latter mechanism which is less sensitive to the system temperature in comparison with the former one.