Effects of dynamic response time in an evolving market

Considering the time scales of global information and personal reaction, we study the role of dynamic response time in the evolution of collective behavior in an evolving market. The insensitiveness to the market information makes the population cluster around a kind of extreme behavior, in which they always follow what happened last time, while a sensitive population tends to self-segregate into opposing groups. The average success rate R among all the agents is found to have a nonmonotonic dependence on the time scale parameter q. There exists a critical value below (above) which R decreases (increases) with the rise of q. Theoretical analyses demonstrate that the higher efficiency found in the market with an insensitive population is related to its predictability. In such a predictable market, the agents following current prediction have a higher winning probability than those rejecting it. Analytical calculations are in good agreement with numerical data.     

Radial anomalous diffusion in an annulus

In this study, time fractional radial diffusion has been modeled in cylindrical coordinates in order to analyze the anomalous diffusion in an annulus. By using an integral transform technique, the analytical solution of the concentration distribution formula is obtained. The establishing of the concentration distribution is found to be controlled by the fractional derivative α, and the influences of α on the concentration field, the total amount diffused and the quantity of mass passing through the inner wall are presented graphically and studied in detail. Asymptotic expressions for the exact solutions are developed in order to explain the numerical results at small and large time, respectively, and the physical mechanism explanation for the paradoxical behavior shown in the numerical results is given.     

On a soluble model of an antiferromagnetic chain with Dzyaloshinsky interactions. II

Time-dependent properties of the one-dimensional XY model with Dzyaloshinsky interactions in the presence of a magnetic field in the z direction are investigated. Explicit expressions are derived for the time correlation functions of the z components of two spins and the time auto-correlation functions of M^z (= the z component of the magnetization). The ergodic behaviour of M^z in the thermodynamic limit is discussed in some detail. Furthermore an exact expression is derived for the time dependence of the average of M^z in a typical nonequilibrium situation. Finally the frequency-dependent susceptibility is evaluated.     

Explicit form of an implicit method for inverse force identification

Most existing time domain force identification methods are based on the state space method, which has the disadvantage of large discretization error with a low sampling frequency or a long sampling duration. This work transforms the conventional implicit Newmark-β algorithm into an explicit form for the solution of the Ax=b equations, which is an equivalent transformation, and it exhibits the same characteristics of Newmark-β algorithm as an implicit method. The accuracy of this method for the dynamic force identification is illustrated with two shear-frame buildings and a planar truss structure. Numerical results are compared with reference analytical responses. The new method gives more accurate identified force time histories compared with those from the conventional state space method for multiple sinusoidal and white noise excitations with 10% measurement noise in the responses.     

Dynamical complexity and stochastic resonance in an asymmetry bistable system with time delay

The dynamical complexity and stochastic resonance (SR) of a time-delayed asymmetric bistable system are studied. Firstly, The effective potential function and steady-state probability density function are deduced based on Born-Oppenheimer approximation theory, and we find that the asymmetric item and time-delayed feedback item can both affect the curve of these two functions, especially the asymmetric item can induce phase displacement. Secondly, the mean first-passage time (MFPT) which plays an important role in research on particles escape rate is derived and we obtain an approximate asymmetric item r which can maintain a steady MFPT. Finally, the influences of different parameters on SR are researched by signal-to-noise ratio (SNR). The analytic expression of SNR is derived and three dimensional graphs and contour maps of SNR with different parameters are obtained. The results indicate that time delay τ and time delay strength e can enhance the SNR and the asymmetric item r has a non-monotone effect on SNR. Notably, adjusting time delay strength e is more sensitive than that of the time delay τ in controlling SR.     

Dynamics of an N-vortex state at small distances

We investigate the dynamics of a state of N vortices, placed at the initial instant at small distances from some point, close to the “weight center” of vortices. The general solution of the time-dependent Ginsburg-Landau equation for N vortices in a large time interval is found. For N = 2, the position of the “weight center” of two vortices is time independent. For N ≥ 3, the position of the “weight center” weakly depends on time and is located in the range of the order of a ³, where a is a characteristic distance of a single vortex from the “weight center.” For N = 3, the time evolution of the N-vortex state is fixed by the position of vortices at any time instant and by the values of two small parameters. For N ≥ 4, a new parameter arises in the problem, connected with relative increases in the number of decay modes.     

Tripartite Entanglement in an Atom-Cavity-Optomechanical System

We investigate tripartite entanglement in an atom-cavity-optomechanical system consisting of a two-level atom coupled to a cavity with an oscillating mirror at one end. The maximally entangled state between the atom, the field and the oscillating mirror can be prepared in the ideal case. It is shown that the atomic coherent angle that is relatively small makes tripartite entanglement much stronger against dissipative effects in a finite time interval. The parameter k plays a very important role in the oscillating frequency of the tripartite entanglement. More importantly, the π-tangle decays more quickly with the increasing of spontaneous emission rate γ and mean photon number n.     

Reflectance spectra and thermoluminescence of NaBr coloured in an electrodeless discharge

A comparative study of the optical and thermoluminescent properties ofγ irradiated NaBr and NaBr coloured in an electrodeless discharge is reported. In discharge coloured NaBrF centre absorption maxima shifted with the colouration time. This is tentatively attributed to the formation ofE centres. Correspondingly, an additional peak was observed in thermoluminescence glow curve. It is suggested that the results are not characteristic of the method of colouration but rather of the imperfections inherent to the powders, and in a perfect (undeformed) single crystal such a phenomenon should not be observed.     

Reversibility and irreversibility from an initial value formulation

From a time evolution equation for the single particle distribution function derived from the N-particle distribution function (A. Muriel, M. Dresden, Physica D 101 (1997) 297), an exact solution for the 3D Navier–Stokes equation – an old problem – has been found (A. Muriel, Results Phys. 1 (2011) 2). In this Letter, a second exact conclusion from the above-mentioned work is presented. We analyze the time symmetry properties of a formal, exact solution for the single-particle distribution function contracted from the many-body Liouville equation. This analysis must be done because group theoretic results on time reversal symmetry of the full Liouville equation (E.C.G. Sudarshan, N. Mukunda, Classical Mechanics: A Modern Perspective, Wiley, 1974). no longer applies automatically to the single particle distribution function contracted from the formal solution of the N-body Liouville equation. We find the following result: if the initial momentum distribution is even in the momentum, the single particle distribution is reversible. If there is any asymmetry in the initial momentum distribution, no matter how small, the system is irreversible.     

Foreign gas broadening of an IR absorption line of formaldehyde

The theory of nuclear spin state relaxation of symmetrical molecules like formaldehyde contains a collision time t_c that is interpreted as time between rotationally inelastic molecular collisions. This time traditionally is determined from measurements of pressure broadening of spectral lines. In order to test whether these collision times, which determine spin relaxation rate constants and line broadening coefficients, respectively, are the same or at least related to another, we have performed systematic measurements of the broadening of an IR line of formaldehyde by other gases of different pressures.     

Numerical prediction of heat transfer by natural convection and radiation in an enclosure filled with an isotropic scattering medium

This paper deals with the numerical solution for natural convection and volumetric radiation in an isotropic scattering medium within a heated square cavity using a hybrid thermal lattice Boltzmann method (HTLBM). The multiple relaxation time lattice Boltzmann method (MRT-LBM) has been coupled to the finite difference method (FDM) to solve momentum and energy equations, while the discrete ordinates method (DOM) has been adopted to solve the radiative transfer equation (RTE) using the S8 quadrature. Based on these approaches, the effects of various influencing parameters such as the Rayleigh number (Ra), the wall emissivity (ε_ι), the Planck number (Pl), and the scattering albedo (ω), have been considered. The results presented in terms of isotherms, streamlines and averaged Nusselt number, show that in absence of radiation, the temperature and the flow fields are centro-symmetrics and the cavity core is thermally stratified. However, radiation causes an overall increase in the temperature and velocity gradients along both thermally active walls. The maximum heat transfer rate is obtained when the surfaces of the enclosure walls are regarded as blackbodies. It is also seen that the scattering medium can generate a multicellular flow.     

Magnetic HFI of cerium in an iron garnet investigated by angular correlations

The magnetic HFI of cerium ion in a lanthanum-doped yttrium iron garnet is investigated by the gamma-gamma angular correlation technique. It is found that cerium, formed after radioactive decay of La¹⁴⁰, reaches the ground state of Ce³⁺ in a time short compared with the nuclear state life-time of 4.9 nsec. Quasi-static as well as time-dependent interactions are detected, yielding an internal field ofH _eff=(21.5± 3) kOe at the nuclei of cerium. The molecular field theory is applied in the analysis of data, and values for the exchange field, the spinlattice relaxation time and the magnectic moment of cerium ion in an iron garnet at room temperature are deduced. These values are:H _exch=(147±20)kOe, τ _c =(4.5±0.6)×10^?13 sec and 〈μ_z〉=(0.017±0.002) Bohr magnetons.     

Experimente an einem Plasmabetatron

Recently reported measurements on a plasma betatronM II were continued and under certain conditions bremsstrahlung produced by relativistic electrons was observed associated with conduction currents of some 100 A. But also early beam disruption occured. The time τ_gg of disruption of the stream has been measured as a function of gas pressure and acceleration field strength. Most of the electrons were lost during an early stage of the acceleration process but also beam loss was observed over a long period of the acceleration time. The expected increase of the circulating runaway current due to improved parameters was not found.     

Effect of an ac field on the conductance fluctuations for mescoscopic systems

With the use of perturbation theory to perform impurity averaging, the conductance fluctuations (CF) in mesoscopic systems are evaluated at finite frequency (ω) of the applied electric field. Calculations are carried out for frequencies much smaller than the inverse elastic mean free time, ω≪τ_el⁻¹. It is shown that the CF decrease monotonically as ω increases. Also, the frequency scale over which this decrease occurs is given by τ_diff⁻¹≪τ_el⁻¹, where τ_diff is the time for an electron to diffuse across the sample. This means that the universality of the CF at zero frequency is not preserved at finite frequency. These calculations are for a rectangular prism. Six leads covering the probe faces are attached to the cube. It is also shown that at finite frequency the sample-to-sample CF have the same size as the fluctuations of a given sample as a function of frequency.     

Mobility of an electron in a Guassian random potential

The mobility of an electron in a Gaussian random potential is evaluated. It is shown that the relaxation time of the electron is found to be proportional to $\text{L}{}^2\text{|}\text{p}\text{|}$ for large and small correlation lengths L where |p| is the electron momentum.     

Black hole in an asymmetric electromagnetic field: New ponderomotive effects — Spin precession and drift

Two new ponderomotive effects in black hole physics are indicated: (i) the precession of the rotation axis of a charged black hole in an external magnetic field, (ii) the drift of a non-charged rotating hole in an asymmetric homogeneous electromagnetic field posessing a non-zero Poynting vector. The precession time for a black hole of solar mass with Q = 10^?5M in a magnetic field B ～ 10¹²G is about a year.     

Bistability of a CO2 laser with SF6 intracavity as an absorber: Transient effects

We investigated time-dependent effects related to the bistable operation of a CO₂ laser with an intracavity nonlinear absorber (SF₆). The response of the system to small perturbations was sensitively dependent on the operating laser line [P(12)→P(30)] of the 10.6 μm band. The narrow bistable region forP(12), due to a very narrow hysteresis loop, can be effectively utilized for optical switching, because of its pronounced sensitivity to variations in operational parameters. The maximum admissable beam blocking time (intracavity) for spontaneous return to lasing was measured forP(16), for a range of absorber pressures. This τm is related to the relaxation time of the upper level in the absorber.     

Influence of the gyromagnetic term in the effect of an oblique magnetic field on the superparamagnetic relaxation time

The effect of a uniform magnetic field applied at an oblique angle ψ to the easy axis of magnetization on the superparamagnetic (longitudinal or Néel) relaxation time is illustrated by considering the simplest possible case where the field is applied normal to the easy axis. This is accomplished by numerically solving the Fokker-Planck equation for the smallest non-vanishing eigenvalue λ₁. It is demonstrated that the asymptotic formula for the Kramers escape rate for general non-axially symmetric potentials evaluated for the particular case ψ = π/2 yields an acceptable asymptotic approximation to the behaviour of λ₁ for sufficiently high-potential barrier heights and a wide range of values of the dimensionless damping factor. The effect of the gyromagnetic term which gives rise to coupling between the longitudinal and transverse modes of motion corresponds to an increase (higher when the dimensionless damping factor a is smaller) of the smallest non-vanishing eigenvalue λ₁ and so to a decrease of the Néel relaxation time τ.     

Optimal wavelet filter for suppression of coherent noise with an application to seismic data

Wavelet analysis is combined with the Karhunen-Loève (KL) transform into an innovative hybrid method for locally filtering coherent noise. In applying our method, the original time series is first decomposed with wavelet transform, the scales more contaminated with noise are reduced by an attenuation factor A_f, and the signal is reconstructed using the inverse wavelet transform. Then the KL transform is applied to the reconstructed signal and the behavior of the first energy modes is analyzed as a function of A_f. The point corresponding to a minimum in the first mode is identified with the maximum extraction of the coherent noise. Our methodology is applied with success to seismic data with the aim of locally extracting the relevant coherent noise, namely the ground roll noise. The procedure can be easily extended to other situations where an undesirable signal is associated with a specific set of energy modes.     

Time of a semiconductor-metal phase transition induced by an ultrashort light pulse in vanadium dioxide

A relationship is obtained for a time τ of a photoinduced semiconductor-metal phase transition of the Peierls type under exposure to an ultrashort laser pulse. It is demonstrated that (i) the time τ increases as the pulse energy density W decreases, and (ii) the phase transition is initiated when the pulse energy density W exceeds a critical value W _c . The results obtained are compared with the experiment on irradiation of a vanadium dioxide film in a light field.