International Journal of Modern Physics B

The Cauchy stress theory has been shown to be profoundly at variance with the principles of the theory of potentials. Thus, a new physical approach to deformation theory is presented, which is based on the balance of externally applied forces and material forces. The equation of state is generalized to apply to solids, and transformed into vector form. By taking the derivatives of an external potential and the material internal energy with respect to the coordinates, two vector fields are defined for the forces exerted by surrounding the system, subject to the boundary conditions, and vice versa, subject to the material properties. These vector fields are then merged into a third one that represents the properties of the loaded state. Through the work function, the force field is then directly transformed into the displacement field. The approach permits fully satisfactory prediction of all geometric and energetic properties of elastic and plastic simple shear. It predicts the existence of a bifurcation at the transition from reversible to irreversible behavior whose properties permit correct prediction of cracks in solids. It also offers a mechanism for the generation of sheath folds in plastic shear zones and for turbulence in viscous flow. Finally, an example is given on how to apply the new approach to deformation of a discrete sample as a function of loading configuration and sample shape.

The chiral anomaly in (2+1)-dimensions and its relationship to the zero mode of the Dirac equation in the massless case is studied. Solutions are obtained for the Dirac equation under a vector potential which generates a constant magnetic field. It is shown that there is an anomaly term associated with the corresponding chiral transformation. It can be calculated by using the regularization procedure of Fujikawa. The results are applied to the quantum Hall effect.

The rapidly rotating Bose–Einstein condensate in the presence of an external electric field is studied. The vortex lattice formed in the condensate will shift after the electric field is applied. The electric field changes the particle density distribution and makes the system more stable. A method to detect this shift is also suggested.

TlInS₂-layered single crystals were prepared by using a special technique for crystal growth, and the obtained crystals were analyzed by X-ray diffraction. The reflectance and transmittance spectra were measured for the mentioned layered crystals and analyzed over the incident photon energy range 1.96–2.46 eV and in the temperature range 77–300 K. In this work and with the aid of these spectra, the temperature dependence of optical transports and parameters were investigated. In line with the transmittance and reflectance analyses, the refractive index as a function of wavelength was determined in the low-energy region of the studied incident photon energy range. As results of the refractive index–wavelength variations, the oscillator and dispersion energies of the refractive index for the TlInS₂-layered single crystals were determined in the temperature range under investigation. Thereafter, static refractive index and static dielectric constant were also investigated.

Synchronization phenomena in dynamical systems with local-world topologies are investigated. The effect of local-world size M on the synchronizability is studied. A larger M makes networks more synchronizable. Then the ability of dynamical networks to resist random errors and attacks is analyzed and compared with those of scale-free and exponential networks. Two attacking strategies are adopted, and a better quantity is used to measure the changes in synchronizability after node removal.

Collapses and revivals phenomenon in system of a single two-level atom and two two-level atoms existing in some superposed states and interacting with a single mode superposed coherent radiation is studied. For superposed Dicke states |1/2, ±1/2> of a single two-level atom interacting with even or odd coherent state, only odd revivals occur. For two two-level atoms, it is found that the collapse and revival times for even and odd coherent states are equal to one half of the corresponding times for coherent state. For this system, Rabi oscillations occur with a main mean frequency and also some second harmonics are present, in general. However, if the two atoms are in the superradiant state, only the second harmonics with large amplitude are obtained. The appearance of weak double frequency revivals for superposed atomic and coherent states was studied and a condition for their disappearance is found.

The effect of nano size Ag addition on the YBa₂Cu₃O_7-δ (Y-123) system has been investigated. 2–15% weight of nano size Ag was added to the Y-123 system prepared by using the sol-gel-solid-state method. The phase purity was investigated by the powder X-ray diffraction method. Energy Dispersive X-ray Analysis (EDAX) was used to determine the distribution of nano Ag in the samples, and the microstructure was observed using a Scanning Electron Microscope (SEM). The transport critical current density was found to increase with increase in nano Ag content.

An effective interionic interaction potential is developed to study the pressure-induced phase transitions from zinc blende (B3) to rock salt (B1) structure in diluted magnetic semiconductors Zn_1-xMn_xSe (x=0.08 and 0.15). As a first step, the elastic constants, including the long-range Coulomb, van der Waals (vdW) interaction and the short-range repulsive interaction up to second-neighbor ions within the Hafemeister and Flygare approach, are derived. Assuming that both the ions are polarizable, the Slater–Kirkwood variational method is employed to estimate the vdW coefficients. The estimated values of the phase transition pressure (P_t) increase with Mn concentration. The vast volume discontinuity in the pressure volume phase diagram identifies the structural phase transition from zinc blende to rock salt structure. The variation of second-order elastic constants with pressure resembles that observed in some binary semiconductors. It is noticed that the vdW interaction is effective in obtaining the thermodynamical parameters such as Debye temperature, Gruneisen parameter, and thermal expansion coefficient. However, the inconsistency in the value of pressure derivative of the theoretical and experimental value of C₄₄ is attributed to the fact that we have derived the expressions by assuming that the overlap repulsion is significant only up to nearest neighbors, as well as neglecting thermal effects.

By exploiting the eigenvalues of the Hessian matrix, which are the second derivatives of the bending energy of shapes obtained using the software Surface Evolver, we partly show the stable phase diagrams of several starfish vesicles. The work indicates that most of the phase transforms are discontinuous and most of the nonaxisymmetric shapes are metastable shapes according to the spontaneous curvature (SC) model. We also find two kinds of stable new starfish shapes and a continuous phase transform in the SC model.

Molecular dynamics simulation study based on the EAM potential is carried out to investigate the effect of pressure on the rapid solidification of Aluminum. The radial distribution function is used to characterize the structure of the Al solidified under different pressures. It is indicated that a high pressure leads to strong crystallization tendency during cooling.