نشریه پژوهش های نوین فیزیک
سال هشتم شماره 1 (پیاپی 16، بهار و تابستان 1403)

The merging for the Schwarzschild type and FRW metrics are discussed and investigated and it is shown that the merger is possible for three geometry of the expanding universe.

The controlled arrangement of nanowires plays a very important role in the development of their application in optoelectronics, nanoelectronics, sensors and spintronic devices. The arrangement of one-dimensional nanostructures has been done using different techniques such as optical manipulation, microfluidics, electric and magnetic fields. In this article, we have used the Langmuir-Blodgett technique for the deposition of magnetic nanowires in the presence of an external magnetic field on solid surfaces. We synthesized magnetic nanowires using direct voltage electrodeposition method and aluminum oxide template, with a hole diameter of 200 nm. After cleaning, we dropcasted the nanowires on the surface of deionized water in a Langmuir trough (Teflon) using a plastic microsyringe. Using two moving barriers, the magnetic nanowires were collected on the subphase (water) surface and at a certain surface pressure and in the presence of an external magnetic field, Langmuir films were transferred to solid substrates. The scanning electron microscope images of the monolayers show that the nanowires are aligned almost in the same direction as the magnetic field. In order to compare the Langmuir–Blodgett films of nanowires with the dropcasting method, films of nanowires using dropcasting method were prepared in the presence and absence of an external magnetic field. This comparison showed that a monolayer film of nanowires can be prepared only by the Langmuir-Blodgett method. Cheapness, high operating speed, layering in large areas, as well as diversity in the morphology of single layers are the importance and advantages of the Langmuir-Blodgett technique.

In this study, the solvent polarity effects on the nonlinear responses of the organic azo dye with the commercial name, Disperse Red 1, were investigated by the z-scan method under 532 nm laser irradiation. The nonlinear optical refraction and absorption were obtained for different solvents. The experimental results reveal that the nonlinear response is highly dependent on the molecular environment around the azo dye and its intermolecular interactions. Since alcohols have a higher order parameter, the nonlinear refraction and absorption decrease with increasing dielectric constant, but for other solvents with low order parameters, the nonlinear indexes increase with increasing dielectric constant. The refractive index is negative and in order of 10-7 cm2/W, which indicates that self-focusing occurs for different solvents.

In this article, the energy gap of 300 nitride compounds was analyzed and investigated using quantum simulations based on Density Functional Theory (DFT). The energy gaps of the compounds were calculated using two approximations, GGA-PBE and HSE06. The parameters considered in the machine learning studies were categorized into two groups: atomic and crystalline parameters. The atomic parameters include covalent radius, electronegativity, the number of valence electrons, and the first ionization energy. After collecting data on atomic features, a multiple linear regression model was fitted to the data. Subsequently, variable selection was performed using the stepwise regression method with the AICc criterion, and the effect size of various features was calculated. Additionally, to improve the accuracy of the model in predicting HSE06, three crystal features were incorporated into the model, and eight different models were fitted, each including one or more of these crystal features. The findings indicate that the model without any crystal variables has an adjusted coefficient of determination (R²) of 75.45%. However, with the inclusion of crystal features, the results improve significantly. Specifically, adding the PBE energy gap as a variable increases the R² to 99.03% (from 75.45% to 99.03%).

In this paper, we introduce the generalized  coherent states and Photon- added coherent states in the sence of Barut-Girardello  for the nonlinear harmonic oscillator with position dependent effective mass. The study of  the resolution of the unity  as  the fundamental property of coherent states,  is done  in Meijer G-function. Also , the non- classical  features of these two states are calculated and analyized by using the  probability distribution function and Mandel paramerer .

The Investigation of the statistical distribution of nuclear energy levels and wave functions in the atomic nucleus as a many-body system is necessary for understanding various reactions of the nuclear structure We are considering the multifractal spectrum analysis of wavefunction to investigate the effect of isospin on the nuclear structure. This analysis is compared with the results obtained by the localization length and the statistical analysis of the distribution of energy levels based on the Brody distribution function. For this purpose, the 46Ca with the only neutron in its valence space and its neighbor nuclide 46Sc, which has different isospin because of replacing one proton to neutron in its valance space, are selected for study on the basis of the nuclear shell model. Energy eigenvalues of the system are calculated with NuShellX code.  The amplitudes of wave functions can be achieved by modifying in the new version of this code.