International Journal of Modern Physics B

This paper discusses the optical and mechanical properties of triglycine sulphate (TGS) and MgCl₂ added TGS single crystals (McTGS) grown from aqueous solution at room temperature using slow evaporation solution growth technique. The grown crystals were characterized by powder X-ray diffraction technique and the cell parameter values are found to be a = 9.405 Å, b = 12.623 Å and c = 5.721 Å; β = 110.347° with V = 637.001 ų. UV-Vis-NIR study shows the direct type transition is involved in these materials and indirect, phonon energy gap of McTGS crystals have also been calculated, and these values are less than the TGS crystals. Refractive index and real and imaginary part of the dielectric constant have been discussed for grown crystals. The value of interband optical transition and oscillator energy has been determined by analyzing refractive index with incident energy. Vickers microhardness test was used to determine hardness number, fracture toughness, brittleness index, yield strength and types of crack formed in the crystals.

We have considered a disordered driven-diffusive system defined on a ring. This system can be mapped onto a heterogeneous zero-range process. We have shown that the grand-canonical partition function of this process can be obtained using a matrix product formalism and that it is exactly equal to the partition function of a two-dimensional walk model. The canonical partition function of this process is also calculated. Two simple examples are presented in order to confirm the results.

Spin-polarons are obtained using an Ising-like exchange model consisting of double and super-exchange interactions in low-dimensional systems. At zero temperature, a new phase separation between small magnetic polarons, one conduction electron self-trapped in a magnetic domain of two or three sites, and the antiferromagnetic phase was previously reported. On the other hand the important effect of temperature was missed. Temperature diminishes Boltzmann probability allowing excited states in the system. Static magnetic susceptibility and short-range spin–spin correlations at zero magnetic field were calculated to explore the spin-polaron formation. At high temperature Curie–Weiss behavior is obtained and compared with the Curie-like behavior observed in the nickelate one-dimensional compound Y_2-nCa_nBaNiO₅.

This paper analyzes the synchronizations for autonomous chaotic systems with disturbance of parameter, achieves the self-synchronization of Lü system, a modified coupled dynamos system and a four-dimensional hyperchaotic system by the methods of active control and adaptive parameter. In addition, the synchronization of Lorenz system and Chen system is presented. Numerical simulations are provided for illustration and verification of the proposed method.

We investigate the theory of observers in the quantum mechanical world by using a novel model of the human brain which incorporates the glial network into the Hopfield model of the neural network. Our model is based on a microscopic construction of a quantum Hamiltonian of the synaptic junctions. Using the Eguchi–Kawai large N reduction, we show that, when the number of neurons and astrocytes is exponentially large, the degrees of freedom (d.o.f) of the dynamics of the neural and glial networks can be completely removed and, consequently, that the retention time of the superposition of the wavefunctions in the brain is as long as that of the microscopic quantum system of pre-synaptics sites. Based on this model, the classical information entropy of the neural-glial network is introduced. Using this quantity, we propose a criterion for the brain to be a quantum mechanical observer.

For the superconducting phase with a d-wave order parameter and zero temperature, the magnetic susceptibility of the t–J model is calculated using the Mori projection operator technique. Conditions for the appearance of an incommensurate magnetic response below the resonance frequency are identified. A fast decay of the tails of the hole coherent peaks and a weak intensity of the hole incoherent continuum near the Fermi level are enough to produce an incommensurate response using different hole dispersions established for p-type cuprates, in which such response was observed. In this case, the nesting of the itinerant-electron theory or the charge modulation of the stripe theory is unnecessary for the incommensurability. The theory reproduces the hourglass dispersion of the susceptibility maxima with their location in the momentum space similar to that observed experimentally. The upper branch of the dispersion stems from the excitations of localized spins, while the lower one is due to the incommensurate maxima of their damping. The narrow and intensive resonance peak arises if the frequency of these excitations at the antiferromagnetic momentum lies below the edge of the two-fermion continuum; otherwise the maximum is broad and less intensive.

The chemical bond parameters of II–IV–V₂ and I–III–VI₂ compounds have calculated using the chemical bond theory of complex crystals. Their hardnesses have been predicted by the chemical bond definition of hardness. The calculated results are in agreement with their experimental values. The calculation of hardness indicates that all of compounds possess good mechanical properties.