جستجوی مقالات مرتبط با کلیدواژه « ناهمسانگردی » در نشریات گروه « فیزیک »

One of the most fascinating features of cosmology is the study of large structures that can reveal the properties of particles with the smallest known cross sections (neutrinos). In fact, in the early universe, after photons, neutrinos play an important role in the formation of structures. The large number of neutrinos, combined with their non-zero mass, leads to today's energy density at least 25 times larger than CMB photons. This high density of free-flowing particles leads to changes in the large-scale structure (LSS) that can be recorded in large galaxy studies or dark current measurements. The purpose of this paper is to determine the direction of bulk flow and other cosmic parameters using the quintessence model. In this paper, we also estimate the mass of neutrinos using neutrino coupling and the scalar field of quintessence. The data where used in this article is the Pantheon Catalog, a total of 1048 Type Ia supernovae. The direction of the bulk flow is slightly different on scales smaller than 0.1, and the higher the scale of the local world, the greater the difference in the direction of the bulk current.

Arsenene is one of the members of a large group of two-dimensional structures that in the present project, we have investigated the single layer structure and its nanoribbons based on density functional theory. In this study, after calculating the single layer band structure, we discussed the effect of width on the band structure of nanoribbon from the angle of quantum limiting phenomenon. The results show the different effect of quantum limiting phenomenon on different points of each band in the band structure, which is the cause of indirect-direct gap transition due to the reduction of the width of armchair nanoribbon. Also, the electrical conductance properties of arsenene single layer have been obtained by calculating the mobility of load carriers and the effect of uniaxial strain of crystalline structure on them has been investigated. In order to investigate the mobility, crystalline structure defects have been neglected and only phonon dispersion is considered based on Takagi relationship. In this process, the focus is not on the quantitative accuracy of the obtained values for the mobility of load carriers and the existing anisotropy between mobility in the two directions of armchair and zigzag has been the focus of the discussion. The results of the calculations show a significant anisotropy of mobility in the two directions of armchair and zigzag and the effect of uniaxial strain of crystal structure on it. Also, a significant difference between the mobility of electrons and holes in the direction of armchair is one of the key results.

Entanglement is one of the fundamental quantum concepts that not only distinguishes quantum mechanics from its classical counterpart but also plays important roles in quantum communication and information processing technologies. Here, we aim to study anisotropy contributions of continuous variable entanglement between magnon modes in antiferromagnets. By introducing different bosonic modes, it is shown that the magnetic uniaxial anisotropy induces different entanglement contributions in the ground state of the system. While some of these contributions appear to be decreasing with respect to anisotropy, the other contributions are increasing as functions of anisotropy. It is also shown that the maximum magnon entanglement is always at the centre of Brillouin zone. The analysis presented here is independent of geometric lattice structure and appropriate for many classes of compounds.

Halide Perovskites have great energy conversion efficiency, but their structural degradation due to change in surface temperature arise from heat accumulation of solar radiation is one of their most important drawbacks. Analysis of structure and thermal transport can be useful in increasing their efficiency. in this paper mechanical, acoustical and thermal properties of CsPbI3 and CsPbBr3 in cubic phase were studied using density functional theory with PBE-GGA approximation. Elastic constants obtained with stress-strain methodology. Using elastic constants, mechanical stability, anisotropy, elastic coefficients, Debye temperature and various sound propagation modes in the materials investigated. Despite mechanical stability in static conditions, the existence of high anisotropy (~2.9) in these perovskites revealed that, they may become unstable in commercial applications. CsPbBr3 compared to CsPbI3 due to higher Debye temperature (120 and 101 K) and more speed of sound propagation (1774 and 1587 m/s), has stronger bonds between the components, in addition to, having higher phonon transport. Thermal conductivity was investigated using the Slack model, which obtained 0.349 and 0.274 W mK/s for CsPbI3 and CsPbBr3, respectively. Higher thermal conductivity of CsPbBr3 leads to less heat accumulation on the surface, so it can be introduce as better choice for use in solar cell applications.

In this paper, we consider the anisotropic super Yang-Mils plasma at finite temperature and and calculate its conductivity in the presence of a constant electric field. By applying the electric field in two different directions, we study the effect of the electric field, charge density and anisotropy parameter on the electrical conductivity of the plasma. We first consider the constant external electric field in the longitudinal x-direction, and then the external electric field is applied to the system in the longitudinal z- direction. At the end, we compare the results of two different directions with each other. Also, we compare the results with those from isotropic Ads-Schwarzschild black hole and non-critical Ads6 model.

The geometrical and topological measures enable us to characterize stochastic field systematically, and  the relation between weighted and unweighted N-point functions is provided. One of such relations is given by the bias factor. In this paper, based on peak statistics, we study the bias factor for stochastic and anisotropic fields. Accordingly, we present the analytical description of local and linear bias factor. Doing simulations, we examine the validation of  the derived analytical relation. Our results show that at high threshold level and large spatial separation, there exists a good agreement between the analytical calculation and numerical computations.

Fission fragment angular distribution (FFAD) data are important to get new insights into the fission process. In this study, the frame work of statistical modeling is used to analyze FFAD from neutron induced fission of 234U.The results have been compared with recent experimental data of 234U(n, f) reaction measured at the n_TOF facility in CERN. Accurate analysis was performed in order to deduce the variance K02 of the K- distribution of levels in the transition nucleus at neutron energies from threshold up to 50 MeV. We show the method in which the quantitative values of K02 is obtained. We have also studied the periodic structure of anisotropy related to the set of (n,xn) reaction in comparison with related cross section performed with TALYS1.8 code. The comparison of the variance with the cross section clearly illustrates the strong correlation between the value of the variance and the opening of a fission chance. We show that whenever the probability of reaction in a new channel and cross section increases, K02 decreases; so the minimum of K02 can show the maximum probability of (n,f)xn reaction. The results are in a good agreement with similar calculations in232Th(n,f) and 238U(n,f) reactions.

In this paper, we quantize electromagnetic field in, lossy, dispersive and anisotropic magnetodielectric media by using phenomenological approach. We obtain quantum input– output relations for anisotropic multilayer metamaterials. As an application of our approach, we investigate the dissipative and anisotropic effects of an anisotropic magnetodielectric slab on the quantum properties of incident input states. For this purpose, quadrature squeezing and Mandel parameter of output states has been calculated by modeling the anisotropic magnetodielectric slab through Lorentz model for a situation in which the incident states on the right and left side of the magnetodielectric slab are two- mode coherent states and quantum vacuum state, respectively.

Investigation of broken symmetry phases with long range order in strongly correlated electron systems is among subjects that have always been of interest to condensed matter scientists. In this paper we tried to study the existence of the 120 degrees magnetic spiral order, based on anisotropy in geometrically frustrated triangular lattices, using variational cluster approximation. We observed that by increasing the anisotropy in the system, the spiral order can be found for AWT IMAGE and for AWT IMAGE; however, it is limited by decreasing AWT IMAGE since antiferromagnetism is dominant for AWT IMAGE. Studying the Mott transition shows that a paramagnetic insulating phase, called quantum spin liquid, happens in the neighborhood of the spiral ordered phase.

The seismic anisotropy is a subject of interest for seismologists and geologists. The information of seismic anisotropy has significant role in geology interpretations (Savage, 1999). In this study, we have investigated the upper crust anisotropy in Bam area by means of shear wave splitting Sg phase. We have selected more than three hundred aftershocks from IIEES local temporary seismic network that had been installed after 26 December 2003 Bam earthquake. In the present study, due to using local waveform data, type of Sg phase and shallow depth of events, the estimated values of seismic anisotropy could be related to heterogeneities within upper crust of Bam area. The shear wave, upon entering the anisotropic region, splits into two phases with polarizations and velocities that caused properties of the anisotropic media. The phases, polarized into fast and slow components, progressively split in time as they propagate through the anisotropic media. This split is preserved in any isotropic segments along the ray path and can be observed as a time delay (δt) between the two horizontal components of motion. Polarity and amplitude are strongly affected by the azimuth of arrival. The orientation of anisotropy is estimated trough measuring the azimuth of fast component (φ). The magnitude of anisotropy is estimated by measuring the time split (δt) between the fast and slow components of motion. Our aim in this study is to calculate the magnitude (t) of anisotropy and direction () of the fast wave as the main parameters of seismic wave anisotropy in Bam area in south east of Kerman Province. For measuring anisotropy parameters, we have used the Teanby et al. (2004) shear wave splitting technique. This method can be divided into three main groups, where the search for the optimal pair of splitting parameters is based on: (1) the minimization of a penalty function which represents the difference between observed and predicted transverse components (e.g., Vinnik et al., 1989); (2) the maximization of the cross-correlation between the fast and slow components or linear particle motion (e.g. Bowman and Ando, 1987; Levin et al.,1999); and (3) the minimization of energy on the corrected transverse component reassembled from the optimal fast and slow components (Silver and Chan, 1988 and 1991). The results for 15 seismic stations show two perpendicular main directions for shear wave anisotropy. These two dominant seismic anisotropy directions as given in table 1, can be considered as geological fabric and the principal stress directions. In the present study, one of the main seismic anisotropy directions is perpendicular to the faults trend for the nearest seismic stations on the fault border. Therefore, some of our results indicated that the polarization of the fast split shear wave is parallel to direction of the maximum horizontal stress. The second of the main seismic anisotropy directions is parallel to the faults trend, especially for that stations far a way fault border. The size of anisotropy is about 0.034 to 0.1 S.

Accurate modeling of omni-directional assay variograms for a deposit, plays a very significant role in the results of 3-D assay estimation and therefore its distribution within the estimation blocks. The high grade variations in uranium deposits render the significance of accurate variogram modeling. By this research, some models have been fitted to the experimental variograms with 0.5 meter composited uranium assay data, resulted from chemical analysis of drill core samples, from a uranium deposit. Reciprocal validation test has been applied for selection and evaluating the effect of suitable results, from multi-structural models in compare with other proper types of models. Validity study of the models is conducted through the reciprocal validation test, based on a series of criteria such as the average of differences and the difference of estimated values and raw data, in order to determine the validity accuracy of the fitted model. It is concluded that the dual-structure spherical model has a higher validity and furthermore reveals the significance of minor structures in variogram modeling, specifically for uranium deposits.

We have performed extensive numerical simulations to estimate the fractal dimension of the mass and also the anisotropy in the shape of sample spanning cluster (SSC) in 2-D site invasion percolation processes with and without trapping. In agreement with the most recent works, we have observed that these two different processes belong to two different universality classes. Furthermore, we have determined for the first time, the degree of anisotropy in the shape of SSC by evaluating its gyration ratio. It is found that despite isotropy of the media and also the dynamics, the shape of invasion percolation clusters are not isotropic. The degree of anisotropy is more for clusters of invasion percolation with trapping. We have also studied the distribution of invaded pore sizes for the two invasion percolation processes.

In this work we investigated the critical properties of the anti-ferromagnetic XY model on a two dimensional Kagome lattice under single-ion easy-axes anisotropy. Employing the mean field theory, we found that this model shows a second order phase transition from disordered to all-in all-out state for any value of anisotropy.