Influence of Charge on Anisotropic Class-one Solution in Non-minimally Coupled Gravity

This paper studies charged star models associated with anisotropic matter distribution in $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ theory, where $\mathcal{Q}=\mathcal{R}_{\phi\psi}\mathcal{T}^{\phi\psi}$. For this purpose, we take a linear model of this gravity as $\mathcal{R}+\zeta\mathcal{Q}$, where $\zeta$ represents a coupling constant. We consider a self-gravitating spherical geometry in the presence of electromagnetic field and generate solution to the modified field equations by using the ``embedding class-one'' condition and $\mathbb{MIT}$ bag model equation of state. The observational data (masses and radii) of four different stellar models like 4U 1820-30,~SAX J 1808.4-3658,~SMC X-4 and Her X-I is employed to analyze the effects of charge on their physical properties. Finally, the effect of the coupling constant is checked on the viability, hydrostatic equilibrium condition and stability of the resulting solution. We conclude that the considered models show viable and stable behavior for all the considered values of charge and $\zeta$.Comment: 37 pages, 11 figure

Study of Charged Compact Stars in Non-minimally Coupled Gravity

This paper studies the structural formation of various spherically symmetric anisotropic configured stars in $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ gravity under the influence of electromagnetic field, where $\mathcal{Q}=\mathcal{R}_{\eta\sigma}\mathcal{T}^{\eta\sigma}$. We construct modified field equations by adopting the Krori-Barua metric potentials (involving unknowns ($A,B,C$)) and employ bag model equation of state to explore the physical characteristics of compact structures like Vela X-I,~4U 1820-30,~SAX J 1808.4-3658,~Her X-I and RXJ 1856-37. The bag constant ($\mathfrak{B_c}$) and other three unknowns are calculated by using experimental data of all considered stars. Further, we adopt a standard model $\mathcal{R}+\varpi\mathcal{R}_{\eta\sigma}\mathcal{T}^{\eta\sigma}$ to interpret the graphical behavior of energy density, pressure in radial and tangential directions as well as anisotropy. We also investigate mass, compactness parameter, surface redshift and energy conditions for compact bodies by taking model parameter ($\varpi$) as $\pm5$. The stability of the obtained solution is examined by means of two different criteria. We conclude that our proposed solution meets all the physical requirements and shows stable behavior everywhere for $\varpi=5$.Comment: 39 pages, 8 figure

Charged Anisotropic Models with Complexity-free Condition

This paper uses the definition of complexity for a static spherically symmetric spacetime and extends it to the case of charged distribution. We formulate the Einstein-Maxwell field equations corresponding to the anisotropic interior and calculate two different mass functions. We then take Reissner-Nordstr\"{o}m metric as an exterior spacetime to find the matching conditions at the spherical boundary. Some scalars are developed from the orthogonal splitting of the curvature tensor, and we call one of them, i.e., $\mathcal{Y}_{TF}$ as the complexity factor for the considered setup. Further, the three independent field equations are not enough to close the system, therefore, we adopt the complexity-free condition. Along with this condition, we consider three constraints that lead to different models. We also present the graphical interpretation of the resulting solutions by choosing some particular values of parameters. We conclude that the models corresponding to $p_r=0$ and a polytropic equation of state show viable and stable behavior everywhere.Comment: 25 pages, 13 figure

Cosmological Solutions through Gravitational Decoupling in f(R,T,RabTab)f(\mathcal{R},\mathcal{T},\mathcal{R}_{\mathrm{a}\mathrm{b}}\mathcal{T}^{\mathrm{a}\mathrm{b}}) Gravity

In this paper, we adopt minimal gravitational decoupling scheme to extend a non-static spherically symmetric isotropic composition to anisotropic interior in $f(\mathcal{R},\mathcal{T},\mathcal{R}_{\mathrm{a}\mathrm{b}}\mathcal{T}^{\mathrm{a}\mathrm{b}})$ theory. A geometric deformation is applied only on $g_{rr}$ metric component through which the modified field equations are separated into two sets, each of them correspond to their parent (seed and newly added) source. An isotropic model suggested by the Friedmann-Lemaitre-Robertson-Walker metric is adopted to reduce the unknowns in the first set. We then obtain an isotropic solution by making use of a linear equation of state and a particular form of the scale factor. A density-like constraint is chosen to solve the other sector containing the deformation function and multiple components of an additional matter source. Further, the graphical interpretation of the developed model is carried out to analyze how a decoupling parameter and modified gravity influence the evolutionary phases of the universe. It is concluded that only the radiation-dominated era meets stability criteria everywhere in this matter-geometry coupled theory.Comment: 30 pages, 10 figure

Complexity Analysis of Charged Dynamical Dissipative Cylindrical Structure in Modified Gravity

This article focuses on the formulation of some scalar factors which are uniquely expressed in terms of matter variables for dynamical charged dissipative cylindrical geometry in a standard gravity model $\mathcal{R}+\Phi\mathcal{Q}$ ($\Phi$ is the coupling parameter, $\mathcal{Q}=\mathcal{R}_{\varphi\vartheta}\mathcal{T}^{\varphi\vartheta}$) and calculates four scalars by orthogonally decomposing the Riemann tensor. We find that only $\mathcal{Y}_{TF}$ involves inhomogeneous energy density, heat flux, charge and pressure anisotropy coupled with modified corrections, and thus call it as complexity factor for the considered distribution. Two evolutionary modes are discussed to study the dynamics of cylinder. We then take the homologous condition with $\mathcal{Y}_{TF}=0$ to calculate unknown metric potentials in the absence as well as presence of heat dissipation. The stability criterion of the later condition is also checked throughout the evolution by applying some constraints. We conclude that the effects of charge and modified theory yield more complex system.Comment: 30 pages, no figur

Charged Anisotropic Tolman IV Solution in Matter-Geometry Coupled Theory

This paper discusses the interior distribution of several anisotropic star models coupled with an electromagnetic field in the context of $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ gravity, where $\mathcal{Q}=\mathcal{R}_{\beta\xi}\mathcal{T}^{\beta\xi}$. In this regard, a standard model of this modified gravity is taken as $\mathcal{R}+\nu_{3}\mathcal{R}_{\beta\xi}\mathcal{T}^{\beta\xi}$, where $\nu_{3}$ symbolizes an arbitrary coupling constant. We assume a charged spherically symmetric metric that represents the interior geometry of compact quark stars and develop the corresponding modified field equations. These equations are then solved with the help of metric potentials of Tolman IV spacetime and a linear bag model equation of state. We consider the experimental data (i.e., radii and masses) of different quark models such as SMC X-4, SAX J 1808.4-3658, Her X-I and 4U 1820-30 to analyze how the charge and modified corrections affect their physical characteristics. The viability and stability of the resulting model is also checked for the considered star candidates with two different values of $\nu_{3}$. We conclude that only two models, Her X-I and 4U 1820-30 show stable behavior in this modified framework for both values of the coupling constant.Comment: 36 pages, 9 figures, Accepted for publication in Physica Script

Effect of Extended Gravitational Decoupling on Isotropization and Complexity in f(\mathbb{R},\mathbb{T}) Theory

This paper develops some new analytical solutions to the $f(\mathbb{R},\mathbb{T})$ field equations through extended gravitational decoupling. For this purpose, we take spherical anisotropic configuration as a seed source and extend it to an additional source. The modified field equations comprise the impact of both sources which are then decoupled into two distinct sets by applying the transformations on $g_{tt}$ and $g_{rr}$ metric potentials. The original anisotropic source is adorned by the first sector, and we make it solvable by considering two different well-behaved solutions. The second sector is in terms of an additional source and we adopt some constraints to find deformation functions. The first constraint is the isotropization condition which transforms the total fluid distribution into an isotropic system only for a specific value of the decoupling parameter. The other constraint is taken as the complexity-free fluid distribution. The unknown constants are calculated at the hypersurface through matching conditions. The preliminary information (mass and radius) of a compact star $4U 1820-30$ is employed to analyze physical attributes of the resulting models. We conclude that certain values of both the coupling as well as decoupling parameter yield viable and stable solutions in this theory.Comment: 32 pages, 11 figure

Study of Decoupled Cosmological Solutions in f(R,T)f(\mathbb{R},\mathbb{T}) Theory

In this paper, we consider a non-static spherical geometry and formulate its extension for the case of anisotropic matter configuration through minimal gravitational decoupling in $f(\mathbb{R},\mathbb{T})$ theory. We apply a particular transformation only on the radial metric function that divides the modified field equations into two distinct sectors corresponding to their parent (original and additional) sources. The unknowns in the first (isotropic) set are reduced by taking the Friedmann-Lemaitre-Robertson-Walker cosmic model. We then obtain the isotropic solution by employing a linear equation of state and power-law form of the scale factor. The other set involves the decoupling function and components of an extra source, therefore we adopt a density-like constraint to close it. Finally, we analyze the role of this modified gravity and the decoupling parameter on three different eras of the cosmos by graphically observing the developed extended solution. It is concluded that the resulting solutions fulfill all the physical requirements only for the matter and radiation-dominated eras.Comment: 25 pages, 9 figure

A survey of simulation techniques in commerce and defence

Despite the developments in Modelling and Simulation (M&S) tools and techniques over the past years, there has been a gap in the M&S research and practice in healthcare on developing a toolkit to assist the modellers and simulation practitioners with selecting an appropriate set of techniques. This study is a preliminary step towards this goal. This paper presents some results from a systematic literature survey on applications of M&S in the commerce and defence domains that could inspire some improvements in the healthcare. Interim results show that in the commercial sector Discrete-Event Simulation (DES) has been the most widely used technique with System Dynamics (SD) in second place. However in the defence sector, SD has gained relatively more attention. SD has been found quite useful for qualitative and soft factors analysis. From both the surveys it becomes clear that there is a growing trend towards using hybrid M&S approaches

Analyzing Undergraduate Students’ Performance in Various Perspectives using Data Mining Approach

The data mining provides better insight rather than the predefined queries or reports for quality enhancement and improvement of an academic program to extract hidden knowledge in students’ performance in various courses. This paper presents data mining approach applied to discover students’ performance patterns in two different perspectives (a) supervised and unsupervised assessment instruments and (b) discover students’ performance patterns in mathematics, English, and programming courses in an engineering degree program. The interesting patterns emerging from both analytic studies offer helpful and constructive suggestions for the improvement and revision of assessment methodologies, restructuring the curriculum, and modifying the prerequisites requirements of various courses. Keywords: Association Rules, Supervised and Unsupervised Assessment, Educational Data Minin