JOURNAL OF RESEARCH ON MANY BODY SYSTEMS
Year:2018 | Volume:8 | Issue:17 |Papers Count:20

In this paper, a massive charged scalar field in a uniform strong electric field background in a de Sitter spacetime of arbitrary dimension has been considered. Using Bogoliubov coefficients, we obtain the semiclassical energy-momentum tensor of the Schwinger pairs in the strong electric field limit. We have shown that the trace of the semiclassical energy-momentum tensor vanishes. We have found that the nonvanishing components of the semiclassical energy-momentum tensor increase by a power of the electric field. Our results of the semiclassical energy-momentum tensor would be important for discussing the gravitational backreaction effect of the Schwinger pair production. We have shown that the Hubble constant decays and the time scale of the decay decreases by a power of the electric field.

In this research, hydrothermal-microwave process was used for synthesis of manganese sulfide (MnS) nanoparticles (NPs). The effects of growth parameters such as concentration, solution type, and power were investigated. After synthesis, different thermo-radiations of microwave were applied and optical properties were studied. Different characterization methods for study of NPs properties such as X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM), energy dispersive X-ray, and UV-Visible spectroscopy were used. XRD patterns and EDX spectra represent formation of polycrystalline MnS phase and the existence of desired elements, respectively. Electron microscopy images showed the composition of NPs in the form of adherent spherical particles. With increasing synthesis temperature, optical energy band gap increased and relative absorbance intensity decreased.

Tumor growth has been the subject of study by additive and multiplicative noise. These methods can often be employed as discrete procedures or they can be independently exploited. In this paper, the tumor growth has been investigated using three different entropy models. We have calculated the steady state probability distribution function using Plank-Fokker equation. The obtained results show that the variations of intensity of the multiplicative and additive noises lead to the tumor cells growth. Also, the tumor cells growth can be controlled by changing the nonextensive degree. The growth of tumor cells increases with the enhancement of the correlated noises.

In this paper, using simulation code CRPropa3. 0, the propagation of 104 primary cosmic rays of proton and iron with energy range of 1018 to 1021 eV was simulated. The spectra of the secondary photons and electron-positrons generated in the interactions of ultra-high energy cosmic rays (UHECRs) with cosmic background photons were investigated. The photon and electron spectra considered here are generated in photopion production, beta decay, and pair production. The minimum energy of primaries and the spectral index of source injection is changed separately and the effect of these changes on the spectra is investigated. Also, the total primary energy percent which transfers to secondaries, is calculated. It is found that for both primaries, lowering the minimum energy of the primaries leads to the decrease of the flux of secondaries. This also results in the decrease of the total energy percent carried by beta and photopion products and the increase of the energy percent of pair production. Finally, in is shown that by increasing the spectral index, the flux and the energy percent of all secondaries decreases for proton and iron primaries.

In this paper, we investigate the effect of neutron matter equation of state on the structure of halo of dark matter and the distribution of dark matter in neutron star using the relativistic two-fluid formalism in the dark-matter admixed neutron star. Applying the equation of state related to the free fermionic gas as dark matter equation of state, we calculate the structure of dark-matter admixed neutron star within different models of Skyrme interaction for the neutron matter, SLy230a, SLy230b, SkM*. Our results indicate that the mass-radius relation depends on the model of interaction. In addition, our calculations confirm that the neutron matter equation of state affects the size of dark matter and neutron matter cores. The results show that the surface gravitational redshift depends on the neutron matter equation of state.

In this paper, the meshless local Petrov-Galerkin (MLPG) method is presented for the numerical solution of the three-dimensional time-dependent Schrö dinger equation. The method is based on the local weak form and the moving least squares (MLS) approximation. In this paper, the Heaviside step function is regarded as the test function. Local sub-domains are also considered as cubic shapes. In order to satisfy the essential boundary conditions, the penalty parameter technique is implemented as the MLS approximation can’ t Kronecker delta function property. The forward finite difference method is used to decompose the time expression of Schrö dinger equations. Moreover, the MLPG results of the problem are compared with those obtained by an exact analytical solution showing the efficiency and accuracy of this method.

Today, semiconductor nanoparticles have attracted much attention in nano-medicine branches. In this study, the ability of the ZnS: Mn nanoparticles to produce reactive oxygen species including radical hydroxyl was investigated and also the preparation method of these nanoparticles was reported. ZnS: Mn nanoparticles were synthesized using co-precipitation method. Excitation of nanoparticles was done by UV radiation. The formation and structure of nanostructures was investigated by XRD, SEM and PL analysis. The PL emission spectrum of the ZnS: Mn nanoparticles shows two main peaks in wavelengths of 444 and 587 nm. The size of ZnS: Mn nanoparticles was obtained at about 24 nm using XRD result which is in agreement with SEM and TEM images. According to the decrease in absorption intensity of methylene blue detector in irradiation alongside prepared nanoparticles, it can be said that ZnS: Mn nanoparticles are able to create hydroxyl radicals. This suggests that ZnS: Mn nanoparticles can be used in cancer therapy using photodynamic therapy method.

In this study, we have used Collocation Method (COM) as a new method for solution of reactor point kinetics equations in the presence of step, linear and sinusoidal reactivities with six groups of delayed neutron. The calculation code was written by MATHEMATICA software. This method, in addition to the low time of calculations and convergence of solutions, has high accuracy. The results of numerical calculations by COM compared with other numerical methods show that this method is efficient and accurate. Therefore, it can be used for dynamical computing at the startup stage of the reactor.

In this paper, the effect of the magnetic field generated by the interaction of femtosecond highintensity laser with under-dense plasma in the bubble regime has been studied on the acceleration of an electron bunch with Gaussian distribution in velocity and position. It was observed that the magnetic field could increase the final energy of electron bunch from about 1GeV to approximately 1. 2 GeV and reduce the final energy spread. Also, the final emittance of electron bunch decreased about one order of magnitude and it was equal to. Moreover, we observed that the magnetic field caused ten percent increment in the number of accelerated electrons.

Inertial confinement fusion is driven by laser or heavy ion beams. In the laser driven-fusion, one of the important points is to absorb laser energy as much as possible. Collisional absorption is an essential mechanism for absorption of laser energy into the target for the critical surface. In this paper, using kinetic theory, the collisional absorption is theoretically studied in an unmagnified and uniform plasma. Collisional absorption is compared with two different one-dimensional Maxwellian and q non-extensive distribution functions and also for linearly polarized light laser. Our results show that higher absorption is obtained for q non-extensive distribution function, and this difference will be more with increasing q value. Also, the effect of the Coulomb logarithm and laser wavelength is considered on the collisional absorption coefficient. The absorption value will decrease by increasing the laser wavelength and also the Coulomb logarithm value has a direct relation with the absorption value of energy.

In this paper, structural, phonon and thermal properties of Co2MnGe and Co2MnSi were calculated and compared with each other. Structural properties of these alloys have a good agreement with other experimental and theoretical works. By using density functional perturbation theory and Quantum Espresso package, phonon dispersion calculation in different directions has been done. Calculation of total and partial phonon density of states demonstrated that by increasing of mass of atoms their contributions decrease at higher frequencies. Also, calculations of specific heat at constant volume and Debye temperature by quasi-harmonic Debye-Einstein model and GIBBS2 package were performed by considering only phonon contribution in the temperatures ranging 0K to 900K which have a good consistency with other theoretical studies. Specific heat at low temperatures has T3behavior, while it tends to saturation limit at high temperatures. Debye temperature decreases by increasing temperature slowly.

The electronic charge transfer between the magnetic sites is essential to know about controllability of the magnetic molecules. Through an analytical study of the density of states (DOS) of the different parts of magnetic molecules [py. H]3[FeCl4]2Cl, the electronic transitions corresponding to the induced magnetization curve under the irradiation of light (Faraday rotation), we illustrate the plausible intra-molecular superexchange pathways inside the molecule. A qualitative justification of large superexchange observed previously in the molecule is addressed by employing a method for deciding the plausible pathway for magnetic coupling between magnetic centers. Results of the present work justify the previous theoretical predictions made in previous works making use of different graphical methods.

In this study, PVA / MWCNT composite fibers were produced by a wet spinning method. In order to fabricate the fibers, first carbon nanotubes were dispersed in deionized water using sodium dodecyl sulfate (SDS) surfactant. Using UV-vis analysis, the high dispersion of carbon nanotubes was confirmed. This solution was mixed homogenously in an aqueous solution of PVA and then was injected into PVA and Na2SO4 static coagulation baths. The resulting fibers were uniform and homogeneous in diameter and could be spun out indefinitely. The structure of the fibers was studied by SEM and their strength was investigated using an Instron tensile tester.

This paper presents a comparative study of organometal halide perovskite-based solar cells using two different transparent conducting oxides, including SnO2 and ZnO, as electron-transporting materials. Simulation is an interesting way of studying the behavior of every component of a solar cell device as well as analyzing the performance of the full device. A solar cell capacitance simulator (AMPS)-1D has been the tool used for numerical simulation of such devices. In this study, the inluences of thickness of absorber and ETMs, dopant concentration of ETM, and working temperature on the performance of photovoltaic solar cells are studied. The performance of both devices indicates the replacement of SnO2 by a ZnO layer. ZnO can be a good option to reduce the cost and increase the mobility of ETM for this type of solar cells.

In this study, the ground states of a 6-qubit star lattice are studied in the presence of a magnetic field. In addition, their bipartite and multipartite entanglements are obtained, using concurrence as a measure of bipartite entanglement and Meyer– Wallach measure and its generalizations as the measures of multipartite entanglement. Also, a comprehensive structure of their entanglement is presented and described. It is shown that the external magnetic field is a tuning agent that determines the separable ground states, the global entangled states and the states between them. Determination of these states helps to choose the required ones for different quantum information processes.

In this study, spin conductivity of gapped graphene using Hubbard model is calculated. We obtain spin conductivity for two cases: in the absence of coulomb interaction and in the presence of coulomb interaction between electrons. It can be seen that for the non-itercting case, by increasing the magnetization, the peaks of spin conductivity will be shifted towards lower frequencies and the height of them rises. By increasing the energy gap, the peaks of spin conductivity will be shifted towards higher frequencies and the height of them rises. In the interacting case, plots of spin conductivity versus frequency have two peaks. One of them belongs to spin up electrons and the other belongs to spin down electrons. By increasing magnetization, the peaks of spin up electrons will be shifted towards lower frequencies and the peaks of spin down electrons will be shifted towards higher frequencies. By increasing the repulsion coulomb interaction and the energy gap, spin up and spin down peaks will be shifted towards higher frequencies.

The 16O(p, γ )17F is an important reaction in CNO cycle and effective in the stellar revolution. The Cross Section and S-factor is calculated using woods Saxon potential for bound levels including 5/2+( ground state) and 1/2+ (first excited state). The main portion of the total cross section for both final states was provided by E1 transitions from the incoming p wave to the bound 1d5/2 and 2s1/2 states. The contribution of the S-factor in the ground state, because of deeply bound state and higher angular momentum, is less than the contribution of the first excited state and the halo properties of the proton at 1/2+ state. By comparing our results with the previous results, a good agreement was observed. The S-factor at zero Energy for states 5/2+ and 1/2+ was 0. 3482 and 10. 21 (keVb), respectively. In addition, we calculated reaction rate, which indicated good agreement between our results, and the data from NACRE and CA88.

In this paper, strontium spinel ferrite nanoparticles (SrFe2O4) were synthesized by sol-gel method. Also, in order to investigate the effect of sintering time on the structural, magnetic and dielectric properties of strontium spinel ferrite nanoparticles a gel of metal nitrates with proper molar ratios was first prepared and then the powder was sintered at 700 ° C at different times. To investigate structural properties from the X-ray diffraction pattern, Fourier transform infrared spectroscopy and field emission scanning electron microscopy were used. Furthermore, to investigate magnetic and dielectric properties from of the vibrating sample magnetometer and an LCR meter were used. The results of X-ray diffraction patterns indicated the formation of the main phase of spinel-strontium ferrite with increasing sintering time. The results of field emission scanning electron microscope showed that the particles size is nano, but particles are stacked together. The results of the Fourier transform infrared spectroscopy confirm the spinel structure in the samples. Hysteresis curve of the samples showed that with increasing sintering time, saturation magnetization and magnetic coercivity increased which is due to change in the distribution of ions and the anisotropy of nanoparticles. Also, the dielectric measurement of the samples shows that the dielectric constant and the dielectric loss decrease while ac electrical conductivity with increasing the frequency increases. These changes were studied by the Maxwell-Wagner model.

One of the key concepts in quantum information theory and quantum computing is the study of quantum correlations. Other factors aside, the effect of decoherence on the quantum correlations is very important. In this paper, dynamics of super-quantum discord in Heisenberg model with Dzyaloshinskii-Moriya interaction and the influence of environmental decoherence by taking Lyndblad equation will be studied. We consider Werner state as the initial state of the system. By calculating the time evolution of the system, we figure out the influence of mixture degree r on the dynamics such as super quantum discord, quantum discord and concurrence. A remarkable result is that when the initial state is Bell state the concurrence decay from 1 to a minimum value is close to 0 but the super-quantum discord and quantum discord vanish. This is contrary to recent results obtained. The effect of coupling between the quantum system and environment on superquantum discord was investigated based on interaction parameters. The results showed that the magnitude of Dzyaloshinskii-Moriya interaction that represents the interaction of spin-orbit interaction has played a significant role in the amount of super quantum discord.

In this paper, the static and dynamic performances of quantum-dot (QD) semiconductor lasers and quantum cascade (QC) lasers are characterized and analyzed comparatively using the standard rate equations model. Using the presented model, the effect of photon lifetime on both the device’ s output characteristics is investigated. The results of simulation show that, due to the ultrafast nature of intersubband transitions (ISTs) in QC lasers that is dominantly induced by the longitudinal optical (LO) phonon emission with a picosecond time scale, the threshold current in QC lasers is much larger than is common for QD lasers, in which the intrinsic carrier lifetime is on the order of a few nanoseconds due to the nature of band-to-band Auger recombination process. Additionally, due to the ultrafast nature of LO-phonon scattering process in QC lasers, the transient oscillations of the emitted photons are over-damped, and no resonance appears in the frequency response. This is in contrast with the transient oscillations and frequency response of QD lasers. This unique feature makes QC lasers ideally suited for high-speed operation.