Anisotropic Source Research Articles

Comparison of Solar Wind Speed Estimates from Nearly Simultaneous IPS Observations at 327 and 111 MHz

Results are presented of a comparison between solar wind speed estimates made using the time delays between 3 pairs of 327 MHz antennas at ISEE and estimates made by modeling the temporal power spectra observed with the 111 MHz BSA antenna at LPI. The observations were made for 6 years in the descending phase of solar cycle 24. More than 100 individual records were obtained for the compact source 3C48 and the extended and anisotropic source 3C298. The correlation between the daily speed estimates from 3C48 is 50%. Their annual averages agree within the error estimates and show the expected solar cycle variation. However the correlation between speeds from 3C298 is only 25% and their annual averages do not agree well. We investigate possible causes of this bias in the 3C298 estimated speeds.

Rotating cosmological cylindrical wormholes in GR and TEGR sourced by anisotropic fluids

Given an anisotropic fluid source, we determine in closed forms, upon solving the field equations of general relativity (GR) and teleparallel gravity (TEGR) coupled to a cosmological constant, cylindrically symmetric four-dimensional cosmological rotating wormholes, satisfying all local energy conditions, and cosmological rotating solutions with two axes of symmetry at finite proper distance. These solutions have the property that their angular velocity is proportional to the cosmological constant.

Asymptotic property of singular solutions in some nonstandard parabolic equation

In this paper, we study the asymptotic properties of singular solutions to some nonstandard parabolic equation involving p(x,t)-Laplacian and nonlocal anisotropic sources. First, we show the existence and uniqueness of weak solutions by using the Galerkin’s approximations in the anisotropic Orlicz–Sobolev spaces. Second, in order to determine extinction rates and time of solutions, we prove some ordinary differential inequalities with the Sobolev embedding inequalities. Third, we combine priori estimates and the embedding theorems to show the rates and time estimates of blow-up solutions.

Microscale Knudsen Effect over the Transverse Thermal Conductivity of Woven Ceramic Fabrics Under Compression

Woven-fiber ceramic materials have shown remarkable results in the design of insulative lay-up structures for flexible thermal protection systems. A deeper understanding of heat transfer through the different insulation layers is key for predicting the performance of heat shields. In this article, a thermo-mechanical multiscale model is developed to predict the out-of-plane thermal conductivity at the micro- and meso-levels of transversely loaded two-dimensional woven ceramic fabrics. Knudsen effects within the multiscale structure are studied by adjusting gas pressure conditions. Alumina-based Nextel-BF20 and silicon carbide Hi-Nicalon with a 5-harness satin weave pattern are modeled by finite-element analysis. The computational results are validated experimentally by applying the anisotropic transient plane source method. We find that out-of-plane thermal conductivity decreases significantly with gas pressure due to Knudsen effects in the confined air within the fibrous structure. The dependence of thermal conductivity of fabrics on fiber volume fraction is shown to decrease markedly with pressure reduction. The proposed multiscale modeling approach yields a notable accuracy improvement, with respect to simplified series-parallel models, when compared with our experimental measurements. The FEA model is applicable to other fabric materials and loading conditions and presents an opportunity to study how changes at the fiber level affect the overall thermal behavior of woven fabrics.

Cosmological solution through gravitational decoupling in Brans-Dicke gravity

In this paper, we compute an anisotropic cosmological solution through a minimal geometric deformation on a non-static spherical spacetime in the framework of self-interacting Brans-Dicke theory. The transformation of the radial component decouples the field equations into two arrays such that the influence of the anisotropic source is limited to one set only. We use FLRW universe model to obtain a solution of the system governed by the isotropic matter source. For this purpose, power-law models of the scale factor as well as massive scalar field are assumed while isotropic pressure and density are related via barotropic equation of state. The decoupling function, appearing in the other set, is evaluated through the conservation equation of the anisotropic source. Finally, we investigate the physical behavior, viability and stability of the extended FLRW solution for different values of the equation of state parameter. It is concluded that the solution is viable and stable for the massless scalar field and the radiation dominated universe.

The effect of areal density asymmetries on scattered neutron spectra in ICF implosions

Scattered neutron spectroscopy is a diagnostic technique commonly used to measure areal density in inertial confinement fusion experiments. Deleterious areal density asymmetries modify the shape of the scattered neutron spectrum. In this work, a novel analysis is developed, which can be used to fit the shape change. This will allow experimental scattered neutron spectroscopy to directly infer the amplitude and mode of the areal density asymmetries, with little sensitivity to confounding factors that affect other diagnostics for areal density. The model is tested on spectra produced by a neutron transport calculation with both isotropic and anisotropic primary fusion neutron sources. Multiple lines of sight are required to infer the areal density distribution over the whole sphere—we investigate the error propagation and optimal detector arrangement associated with the inference of mode 1 asymmetries.

Anisotropic stellar structures in the theory of gravity with quintessence via embedding approach

This work suggests a new model for anisotropic compact stars with quintessence in gravity by using the off-diagonal tetrad and the power-law as , where T is the scalar torsion and and n are real constants. The acquired field equations incorporating the anisotropic matter source along with the quintessence field, in gravity, are investigated by making use of the specific character of the scalar torsion T for the observed stars , , , , and . It is suggested that all the stellar structures under examination are advantageously independent of any central singularity and are stable. Comprehensive graphical analysis shows that various physical features which are crucially important for the emergence of the stellar structures are conferred.

APPLICATION OF THE SPH EQUIVALENCE TECHNIQUE TO THE CABRI FULL CORE IN NON-FUNDAMENTAL MODE

We developed a SPH equivalence technique in non-fundamental mode condition between a CABRI full-core model solved with the method of characteristics (MOC) in 2D and a simplified full-core model solved with the simplified P3 (SP3) method, linear anisotropic sources and discretized with Raviart-Thomas finite elements over a pure Cartesian mesh. The MOC and SP3 calculations are performed with DRAGON5 and DONJON5 codes, respectively. A three-parameter database is generated by DRAGON5 and is interpolated in DONJON5 as a function of the core condition. An objective function is set as the root mean square (RMS) error (MOC-SP3 discrepancy) on absorption distribution and leakage rates defined over the macro-geometry in DONJON5. Our algorithm is a quasi-Newtonian gradient search based on the Limited memory Broyden-Fletcher-Goldfarb-Shanno (LBFGS) method. Numerical results are presented with Hafnium bars withdrawn or inserted.

OpenNTP: Implementation of the S[formula omitted] method in cartesian 2D geometry and the CP method in cylindrical and spherical 1D geometry

This paper presents the implementation of the discrete ordinates method (SN) in 2D cartesian geometry and the collision probability method (CP) in cylindrical and spherical 1D geometry in OpenNTP code (Open Neutron Transport Package). This code is a pedagogical tool for computer analysis of nuclear reactors. Its main features are as follows: a free software with an open source, it solves the neutron transport equation to a few steady-state groups on a grid structured in one or two spatial dimensions with an isotropic and anisotropic dispersion source, and any new calculation method and algorithm would be easy to implement in this proposed code. Also, the code offers the possibility to calculate the main parameters of nuclear reactors such as the multiplication factor and the distribution of the scalar and angular neutron fluxes. Additional parameters, like the reaction rates, the pin power distribution and the boundary currents are also calculated. Moreover, a graphical user interface written in Python 3 programming language has been developed to simplify the use of OpenNTP. Some applications of the OpenNTP code have been compared on the one hand with the Monte Carlo OpenMC and MCNP6.1 codes and the WIMSD-5B lattice transport code, on the other hand. Numerical results are given to illustrate the accuracy of the OpenNTP code. Program summaryProgram Title: OpenNTP, version 1.2CPC Library link to program files:https://doi.org/10.17632/gm2b6799j6.1Developer’s repository link:https://github.com/mohamedlahdour/OpenNTPLicensing provisions: GPLv2Programming language: fortran90 and Python 3External routines/libraries: NumPy, Matplotlib, PyQt5, f2pyNature of problem: Solving the steady-state multigroup neutron transport equation by different methods in one, or two spatial dimensions.Solution method: the characteristic method (MOC), the discrete ordinate (SN) method and the collision probability method (CP)

Decoupled anisotropic spheres in self-interacting Brans-Dicke gravity

The focus of this paper is to obtain anisotropic spherically symmetric solutions by means of gravitational decoupling in the background of self-interacting Brans-Dicke theory. We introduce minimal geometric deformation in the radial metric component to decouple the field equations into two arrays. The first set, governed by the seed source, is determined through metric functions of isotropic solution (Heintzmann/Tolman VII spacetimes) while the second set is solved by imposing two constraints on the anisotropic source. The unknown constants are evaluated via matching conditions at the stellar boundary. We investigate the effects of massive scalar field as well as decoupling parameter on the physical structure of anisotropic models and check them for viability through energy conditions. It is concluded that the anisotropic solutions obtained through constraint I are well-behaved for selected values of the decoupling parameter. For the second constraint, the extended Heintzmann solution is viable but anisotropic Tolman solution does not comply with dominant energy condition for higher values of the decoupling parameter.

Lithospheric mantle anisotropy from local events beneath the Sunda–Banda arc transition and its geodynamic implications

Shear wave splitting analysis to characterise lithospheric mantle anisotropy has been performed to provide better knowledge about lithospheric deformation and mantle flow beneath the Sunda–Banda arc transition, Indonesia. The tectonic setting of the study area is very complex characterised by the transition from subduction along Sunda arc to collision in Banda arc. The splitting measurements show lateral and vertical variation in the fast directions of the S-waves in this region. When the splitting results are analysed through 2D delay-time tomography and spatial averaging, systematic patterns in delay times and fast polarisation become more visible. In the subduction domain, the spatial averages of fast directions are dominated by two distinct fast polarisations: perpendicular and parallel to the plate motion for shallow and deep events, respectively. The results suggest that anisotropy in this area is not only controlled by anisotropic source related to the simple mantle flow model, but also by anisotropic fabric in the mantle deformed under influence of high stresses, high water contents and low temperatures. In addition, there might also be contribution from the anisotropic body in the upper layer. In the collision domain, spatially averaged fast directions show mostly perpendicular to the plate motion for all deep levels. For shallow level in this region, this trend is mainly governed by the lithospheric deformation process due to the continent-arc collision as also shown by delay time tomographic inversion. For deeper part of the region, the result of tomographic inversion and spatial averaging reveals a high anisotropy followed by rotational pattern of fast directions in the north of Timor. We suggest that this pattern might be related to the induced mantle flow due to lateral tearing of the slab.

Wormholes in 4D Einstein\u2013Gauss\u2013Bonnet gravity

Recent times witnessed a significant interest in regularizing, a D rightarrow 4 limit, of EGB gravity initiated by Glavan and Lin [Phys. Rev. Lett. 124, 081301 (2020)] by re-scaling GB coupling constant as alpha /(D-4) and taking limit D rightarrow 4, and in turn these regularized 4D gravities have nontrivial gravitational dynamics. Interestingly, the maximally or spherically symmetric solution to all the regularized gravities coincides in the 4D case. In view of this, we obtain an exact spherically symmetric wormhole solution in the 4D EGB gravity for an isotropic and anisotropic matter sources. In this regard, we consider also a wormhole with a specific radial-dependent shape function, a power-law density profile as well as by imposing a particular equation of state. To this end, we analyze the flare-out conditions, embedding diagrams, energy conditions and the volume integral quantifier. In particular our −ve branch results, in the limit alpha rightarrow 0, reduced exactly to vis-grave{a}-vis 4D Morris-Thorne of GR.

Extended gravitational decoupled solutions in self-interacting Brans–Dicke theory

In this paper, we construct anisotropic spherical solutions from known isotropic solutions through extended gravitational decoupling method in the background of self-interacting Brans-Dicke theory. The field equations are decoupled into two sets by applying geometric deformations on radial as well as temporal metric components. The first array corresponds to isotropic fluid while influence of the anisotropic source is confined to the second set. The isotropic sector is determined through metric functions of isotropic solutions (Tolman IV/Krori-Barua) whereas two constraints on the anisotropic source are required to close the second system. The impact of the massive scalar field as well as the decoupling parameter on the physical characteristics of the anisotropic solutions is analyzed graphically. We also check the viability, compactness, surface redshift and stability of the obtained solutions. It is found that the resulting solutions follow accepted physical trend for some values of the decoupling parameter.

Retrieval of amplitude and attenuation from ambient seismic noise: synthetic data and practical considerations

SUMMARY Ambient noise correlation has been used extensively to retrieve traveltimes of surface waves. However, studies of retrieving amplitude information and attenuation from ambient noise are limited. In this study, we develop methods and strategies to extract Rayleigh wave amplitude and attenuation from ambient noise correlation, based on theoretical derivation, numerical simulation, and practical considerations of real seismic data. The synthetic data included a numerical simulation of a highly anisotropic noise source and Earth-like temporally varying strength. Results from synthetic data validate that amplitudes and attenuations can indeed be extracted from noise correlations for a linear array. A temporal flattening procedure is effective in speeding up convergence while preserving relative amplitudes. The traditional one-bit normalization and other types of temporal normalization that are applied to each individual station separately are problematic in recovering attenuation and should be avoided. In this study, we propose an ‘asynchronous’ temporal flattening procedure for real data that does not require all stations to have data at the same time. Furthermore, we present the detailed procedure for amplitude retrieval from ambient noise. Tests on real data suggest attenuations extracted from our noise-based methods are comparable with those from earthquakes. Our study shows an exciting promise of retrieving amplitude and attenuation information from ambient noise correlations and suggests practical considerations for applications to real data.

Upper mantle seismic anisotropy beneath the Kachchh rift zone, Gujarat, India, from shear wave splitting analysis

Unravelling the anisotropic behaviour of the upper mantle helps to shed light on its present and past deformation processes. In this study, we attempt to explore the seismic anisotropy prevailing within the upper mantle beneath the Kachchh rift zone through shear wave splitting analysis. We have measured the splitting parameters (e.g., fast axis orientation ( $$ \varPhi $$ ) and delay time ( $$ \delta t $$ )) using SKS/SKKS core refracted phases from 112 teleseismic events recorded at NGRI network in the Kachchh region, during 2006–2009 and 2013–2016. The ‘ $$ \varPhi $$ ’ and ‘ $$ \delta t $$ ’ estimates vary from N34° to N73°E and 0.80 to 1.5 s, respectively. The average vector means of ‘ $$ \varPhi $$ ’ and ‘ $$ \delta t $$ ’ for all the stations are found to be $$ {\text{N}}\left( {58 \pm 10} \right) $$ °E and (0.99 ± 0.19) s, respectively. Measurements of 59 good SKS/SKKS splitting parameters from 112 earthquakes reveal that the upper mantle is highly anisotropic beneath the Kachchh rift zone with an average fast axis orientation of $$ {\text{N}}\left( {58 \pm 10} \right) $$ °E, which is deviated nearly $$ (\sim{\text{N}}18 $$ °E) from the absolute plate motion (APM) direction (~N40°E) of the Indian plate in a no-net-rotation reference frame. This deviation of fast axis orientation from APM direction may be attributed to the effect of Kachchh rift zone as well as the presence of structural imprints of the 65 Ma Deccan mantle plume in the study region. And the average delay time of (0.99 ± 0.19) s is consistent with the global average (1 s) for continents. Furthermore, the modelled seismic layer thicknesses reveal that anisotropic sources beneath study region are associated with both the lithospheric deformation processes (e.g., 184 Ma African rifting, 88 Ma Madagascar rifting, 65 Ma Deccan mantle plume) as well as asthenospheric flows.

Stable Wormholes in the Background of an Exponential f(R) Gravity

The current paper is devoted to investigating wormhole solutions with an exponential gravity model in the background of f ( R ) theory. Spherically symmetric static spacetime geometry is chosen to explore wormhole solutions with anisotropic fluid source. The behavior of the traceless matter is studied by employing a particular equation of state to describe the important properties of the shape-function of the wormhole geometry. Furthermore, the energy conditions and stability analysis are done for two specific shape-functions. It is seen that the energy condition are to be violated for both of the shape-functions chosen here. It is concluded that our results are stable and realistic.

Complexity factor for cylindrical system in Brans–Dicke gravity

In this paper, we explore the physical aspects that create complexity within a static anisotropic cylindrical source in the framework of self-interacting Brans–Dicke theory. We split the Riemann tensor to formulate structure scalars associated with fundamental properties of the fluid in the presence of the scalar field. We define the complexity factor based on these scalars and then discuss the criteria for zero complexity. Finally, we use the condition of vanishing complexity as a constraint to check the behavior for two compact objects. It is deduced that the inclusion of the scalar field increases the complexity of the system.

Anisotropic compact stars in self-interacting Brans-Dicke gravity

This paper focuses on the extension of isotropic spherically symmetric solutions to anisotropic domain by means of minimal geometric deformations in the context of self-interacting Brans-Dicke theory. These deformations decouple the system of field equations into two sets, one describing the isotropic matter field and the other governed by anisotropic source. The former array is evaluated by assuming the metric potentials of isotropic solution (Durgapal-Fuloria/Krori-Barua spacetimes) while additional constraints are applied to solve the later. The junction conditions at the hypersurface of the compact object are employed to determine the unknown constants. The effect of scalar field on physical behavior and viability of all anisotropic solutions is analyzed through regularity and energy conditions. It is observed that anisotropic Krori-Barua solution is viable only for small values of the decoupling parameter whereas the extended Durgapal-Fuloria solution is viable under all constraints.

Realistic solutions of fluid spheres in [formula omitted] Gravity under Karmarkar condition

This manuscript investigates the compact stars solutions in the background of observational data (radii and mass) by employing the Karmarkar condition under the f(G,T) modified gravity for an anisotropic source of fluid. For this study, we have assumed a specific model for grr metric potential function, which has fulfilled the Karmarkar condition. This assuming model helps to calculate another metric function gtt by using the Karmarkar condition scenario. Further, this study deals to discuss the necessary physically properties by using the observational data for 4U1538-52, LMCX-4, and PSRJ1614-2230 models with three different values of parameter β. It is depicted from this current study; the calculated solutions are physically acceptable with best degree of accuracy. All the physically necessary relevant parameters and properties compact stars are presented graphically. It is noticed during this study the parameter β, has some importance and considerable role for these calculated solutions. In the end, it is concluded that our obtained solutions are physically arguable with well-behaved nature for f(G,T) modified gravity for these discussed compact stars.

Correlated magnetic noise from anisotropic lightning sources and the detection of stochastic gravitational waves

Direct detection of gravitational waves (GWs) from compact binary systems suggests that the merger rate of such events is large, and the sum of their GWs can be viewed as stochastic signals. Because of its random nature, cross-correlating the signals from multiple detectors is essential to disentangle the GWs from instrumental noise. However, the global magnetic fields in the Earth-ionosphere cavity produce the environmental disturbances at low-frequency bands, known as Schumann resonances, and coupled with GW detectors, they potentially contaminate the stochastic GW signal as a correlated noise. Previously, we have presented a simple analytical model to estimate its impact on the detection of stochastic GWs. Here, extending the analysis to further take account of the effects of anisotropic lightning source distributions, we present a comprehensive study of the impact of correlated magnetic noise at low-frequency bands, including non-tensor-type GWs, as well as circularly polarized tensor-type GWs. We find that as opposed to a naive expectation, the impact of correlated magnetic noise does not always increase with anisotropies in the lighting source distribution. Even in the presence of large anisotropies, there is a robust detector pair for which the amplitude of correlated magnetic noise becomes comparable to or well below detectable amplitude of stochastic GWs. The results indicate that the properties of the correlated magnetic noise depend crucially on both the geometrical and geographical setup of the detector's pair, and Virgo and KAGRA would be potentially the most insensitive detector pair against the correlated magnetic for both tensor- and non-tensor-type stochastic GWs.