International Journal of Modern Physics B

Based on the entangled state representation for describing electron's coordinates under uniform magnetic field, we establish a one-to-one correspondence between quantum Hamiltonian and its classical Weyl function through the introduction of Wigner operator. We also study some new important properties of Wigner function of electron's quantum states, such as its upper bound, and its relation with electron's wave function. These discussions demonstrate the beauty and elegance of the entangled state representation.

Due to their relevance to physics and technology, the Bose–Einstein condensates (BECs) are of current interest. Certain dynamics of the BECs, such as the cigar-shaped condensate confined in a cylindrically symmetric parabolic trap, can be described by the Gross–Pitaevskii (GP) equation with a time-dependent trap. In this paper, by virtue of the Painlevé analysis and symbolic computation, we derive the integrable condition for the GP equation with the time-dependent scattering length in the presence of a confining or expulsive time-dependent trap. Lax pair for this equation is directly obtained via the Ablowitz–Kaup–Newell–Segur scheme under the integrable condition. Bright one-soliton-like solution of the GP equation is presented via the Bäcklund transformation and some analytic solutions with variable amplitudes are obtained by the ansatz method. In addition, an infinite number of conservation laws are also derived. Those results could be of some value for the studies on the lower-dimensional condensates.

Samples of CaCu₃Ti₄O₁₂ (CCTO) ceramics were prepared by solid state reaction method. X-ray diffraction analysis confirmed single phase formation for the powder calcined at 1173 K. Sintering was done at different temperatures viz. 1348 K, 1373 K and 1398 K with a fixed heating rate of 3 K/min. Detailed study of dielectric properties was carried out for the CCTO samples sintered at 1373 K for different duration of holding times (2 h and 10 h). It is found that dielectric properties are sensitive to both sintering time and temperature. With increasing sintering time from 2 h to 10 h dielectric constant increases from ∼2.1 × 10⁴ to ∼2.5 × 10⁴ measured at 1 kHz at room temperature. Impedance spectroscopy has been used for separating out of grain and grain boundary contributions to the overall electrical properties.

Secure key distribution is impossible in pure classical environment. Unconditional secure key distribution is available when quantum means are introduced, assisted by a classical communication channel. What is possible when a quantum key distribution scheme is without classical communication? We present a general model with this constraint and show that quantum key distribution without classical eavesdropping check is in principle impossible. For an adversary can always succeed in obtaining the secret key via a special case of man-in-the-middle attack, namely intercept-and-forward attack without any risk of being captured.

Depending on the properties of photonic band gap materials, a novel photonic crystal fiber (PCF), formed by lithium niobate and liquid crystal, has been studied numerically. Dispersion relationships and transmission spectra of the PCF are calculated by methods of the full-vector modal and the finite difference time domain, respectively. The parameter-dependent dispersion and transmission of the PCF have been found. It is shown that the design of the novel photonic crystal fiber could be supported by the theoretical analysis in the paper.

Transparent and conducting SnO₂ thin film has been produced on quartz substrate using rapid thermal oxidation of pure Sn in air at different oxidation temperature and oxidation time. The transmittance T in the visible and NIR was investigated, the allowed direct energy gap was determined to be 3.18 eV at optimum condition of 600° and 90 s. The dependence of the resistivity on the film thickness and oxidation time has been studied. The optimum thickness of high transmittance and lowest resistivity is about 150 nm for SnO₂ were ρ = 2 × 10^-2Ω cm and T = 88%.

We have discussed the time evolution along with the nonclassicality phenomena of a system containing a vee-type three-level atom interacting with a bimodal electromagnetic field. A general expression for the atomic inversion is presented. It is found that the model undergoes Rabi oscillation. The total noise of the output state is measured.

An extended variable separated ODE method is presented for exploring the explicit exact solutions of the mKdV-sinh-Gordon equation by introducing a more general auxiliary ODE, and by employing its rich types of solutions, we can not only recover the previously known exact solutions, but also derive some new formal solutions for the mKdV-sinh-Gordon equation.

There is a common time parameter for representing the sensitivity or the lag (response) time of drivers in many car-following models. In the viewpoint of traffic psychology, this parameter could be considered as the perception–response time (PRT). Generally, this parameter is set to be a constant in previous models. However, PRT is actually not a constant but a random variable described by the lognormal distribution. Thus the probability can be naturally introduced into car-following models by recovering the probability of PRT. For demonstrating this idea, a specific stochastic model is constructed based on the optimal velocity model. By conducting simulations under periodic boundary conditions, it is found that some important traffic phenomena, such as the hysteresis and phantom traffic jams phenomena, can be reproduced more realistically. Especially, an interesting experimental feature of traffic jams, i.e., two moving jams propagating in parallel with constant speed stably and sustainably, is successfully captured by the present model.

Ultra fine NiAl_xFe_2-xO₄(0 ≤ x ≤ 1) nanopowders were synthesized by sol-gel method and their structural properties were investigated using X-ray diffractometer (XRD) and fourier transform infrared (FTIR) spectrometer. The particle size D, lattice constant a, density dx decreased with increasing non-magnetic Al content x. The combustion reaction mechanisms were explained with the help of FTIR analysis.

In this paper, a solution to heat equation in a spherical model is proposed. The model takes into account conjointly the boundary conditions and the transfer equations in a spray device. The deposited layer is supposed to be Gaussian and not uniform like most recent studies. The solution, using Legendre, Bessel and Boubaker polynomials expansions, presents the advantage of being continuous and indefinitely derivable. These features make the resolution connectable to any heat transfer similar model.

We investigate the problem of teleportation of tripartite entangled coherent state (ECS) using linear optical devices such as beam splitters, phase shifters, and two-mode number measurements. The scheme is based on the maximally four-partite ECS with bipartite maximal entanglement as the quantum channel to teleportation tripartite ECS. Our scheme is efficient in the sense that for mean number of photons equal to 2, the minimum of average fidelity (MAF) for teleportation an arbitrary tripartite entangled state is 1-2.3 × 10^-7. We also generalize the tripartite scheme into multipartite case and calculate the MAF for the schemes in multipartite cases.

A novel multilayer starlike ZnO nanostructure has been successfully synthesized on a Si (111) substrate at 600°C by chemical vapor deposition using Zn and zinc acetate dihydrate as the source materials. The morphology, structure, and optical properties are investigated by field emission scanning electron microscopy, X-ray diffraction, Raman and photoluminescence (PL) spectrum, respectively. The results show that the multilayer starlike ZnO nanostructures have hexagonal wurtzite structure. The room-temperature PL spectrum shows the dominant green band peak and the weak UV peak. The possible growth mechanism of the multilayer starlike ZnO nanostructures is also discussed.

W-type hexagonal ferrites having the formula BaCo_2-xMg_xFe₁₆O₂₇ with x = 0, 0.4, 0.8, 1.2, 1.6, 2.0 were synthesized by the chemical coprecipitation method. XRD analysis shows that the structure of all the compositions is W-type hexagonal ferrite. The c/a ratio varies from 5.48 to 5.52, consistent with the standard values. It was observed that the bulk density and X-ray density decrease whereas porosity increases with increasing concentration of Mg²⁺. Room temperature resistivity increases, from 10³ to 10⁷ (Ω cm) by increasing the concentration of Mg²⁺, due to an increased number of grain boundaries. The remanence and saturation magnetization decrease with increasing Mg²⁺ content while coercivity increases as the Mg²⁺ increases according to the relation H_c ∝ 1/r. The measured coercivity values are suitable for use in high frequency applications such as microwave absorber materials.

Consideration is given to magnetodynamics of high-coercivity submicron particles suspended in a liquid and exposed to an AC magnetic field with subcritical (smaller than article coercivity) amplitude. In experiments, use is made of chromium dioxide particles, different-viscosity liquids, and magnetic fields with frequency of 430 Hz and amplitude of up to 230 Oe. The registered dynamic magnetization curves are analyzed within the framework of models of orientational dynamics of single-domain particles and magnetic clusters. The possibility of applying high-coercivity particles for magnetodynamic probing viscosity of liquids is discussed.