arXiv subjects

Tayyab Naseer

Publications and source records attributed to Tayyab Naseer.

At least 37 records · Page 2Linked to original sources

arXiv2024

Anisotropic Durgapal-Fuloria Neutron Stars in $f(\mathcal{R},\mathrm{T}^{2})$ Gravity

The main purpose of this paper is to obtain physically stable stellar models coupled with anisotropic matter distribution in the context of $f(\mathcal{R},\mathrm{T}^{2})$ theory. For this, we consider a static spherical geometry and formulate modified field equations containing various unknowns such as matter determinants and metric potentials. We then obtain a unique solution to these equations by employing Durgapal-Fuloria ansatz possessing a constant doublet. We also use matching criteria to calculate the values of these constants by considering the Schwarzschild exterior spacetime. Two different viable models of this modified theory are adopted to analyze the behavior of effective matter variables, anisotropy, energy conditions, compactness and redshift in the interiors of Her X-1, PSR J0348-0432, LMC X-4, SMC X-1, Cen X-3, and SAX J 1808.4-3658 star candidates. We also check the stability of these models by using three different physical tests. It is concluded that our considered stars satisfy all the physical requirements and are stable in this modified gravity for the considered parametric values.

gr-qc↗

arXiv2024

Study of Charged Cylindrical Collapse in $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ Gravity

This paper investigates the effects of electromagnetic field on the gravitational collapse in $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ theory, where $\mathcal{Q} = \mathcal{R}_{φ\vartheta} \mathcal{T}^{φ\vartheta}$. For this, we assume dynamical cylindrically symmetric self-gravitating geometry which is coupled with generalized anisotropic matter distribution as well as dissipation flux. We adopt the model $\mathcal{R}+Φ\sqrt{\mathcal{T}}+Ψ\mathcal{Q}$ to formulate the corresponding dynamical and transport equations by employing the Misner-Sharp as well as Müler-Israel Stewart formalisms, where $Φ$ and $Ψ$ are real-valued coupling constants. The influence of state variables, heat dissipation, charge and the bulk viscosity on the collapsing phenomenon is then studied by establishing some relations between these evolution equations. Moreover, the Weyl scalar and the modified field equations are expressed in terms of each other. We apply some constraints on the considered modified model and the fluid configuration to obtain conformally flat spacetime. Finally, we address different cases to check how the modified corrections and charge affect the collapse rate of cylindrical matter source.

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arXiv2024

Study of Decoupled Anisotropic Solutions in $f(R,T,R_{ρη}T^{ρη})$ Theory

In this paper, we consider isotropic solution and extend it to two different exact well-behaved spherical anisotropic solutions through minimal geometric deformation method in $f(R,T,R_{ρη}T^{ρη})$ gravity. We only deform the radial metric component that separates the field equations into two sets corresponding to their original sources. The first set corresponds to perfect matter distribution while the other set exhibits the effects of additional source, i.e., anisotropy. The isotropic system is resolved by assuming the metric potentials proposed by Krori-Barua while the second set needs one constraint to be solved. The physical acceptability and consistency of the obtained solutions are analyzed through graphical analysis of effective matter components and energy bounds. We also examine mass, surface redshift and compactness of the resulting solutions. For particular values of the decoupling parameter, our both solutions turn out to be viable and stable. We conclude that this curvature-matter coupling gravity provides more stable solutions corresponding to a self-gravitating geometry.

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arXiv2024

Influence of $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ Gravity on Cylindrical Collapse

This article examines the dynamics of gravitational collapse in $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ gravity, where $\mathcal{Q}=\mathcal{R}_{\mathrm{ab}}\mathcal{T}^{\mathrm{ab}}$. We consider self-gravitating anisotropic cylindrical geometry whose interior is filled with dissipative matter configuration and match it with exterior cylindrically symmetric spacetime at the hypersurface through junction conditions. We employ the Misner-Sharp and Müler-Israel Stewart formalisms to derive the dynamical as well as transport equations corresponding to the model $\mathcal{R}+Φ\sqrt{\mathcal{T}}+Ψ\mathcal{Q}$, where $Φ$ and $Ψ$ are arbitrary coupling constants. We then establish some relations between these equations through which the impact of effective matter variables, heat dissipation and the bulk viscosity on the collapse rate is studied. Further, we express the Weyl scalar in terms of the effective matter sector. We also obtain the conformal flatness by applying some restrictions on the considered model and taking dust configuration into the account. Finally, we investigate various cases to check whether the modified corrections increase or decrease the collapse rate.

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arXiv2024

Charged Anisotropic Spherical Collapse in $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ Gravity

This paper discusses the gravitational collapse of dynamical self-gravitating fluid distribution in $f(\mathcal{R},\mathcal{T},\mathcal{Q})$ gravity, where $\mathcal{Q}=\mathcal{R}_{φ\vartheta}\mathcal{T}^{φ\vartheta}$. In this regard, we assume a charged anisotropic spherical geometry involving dissipation flux and adopt standard model of the form $\mathcal{R}+Φ\sqrt{\mathcal{T}}+Ψ\mathcal{Q}$, where $Φ$ and $Ψ$ symbolize real-valued coupling parameters. The Misner-Sharp as well as Müler-Israel Stewart mechanisms are employed to formulate the corresponding dynamical and transport equations. We then interlink these evolution equations which help to study the impact of state variables, heat dissipation, modified corrections and charge on the collapse rate. The Weyl scalar is further expressed in terms of the modified field equations. The necessary and sufficient condition of conformal flatness of the considered configuration and homogeneous energy density is obtained by applying some constraints on the model along with disappearing charge and anisotropy. Finally, we discuss different cases to investigate how the spherical matter source is affected by the charge and modified corrections.

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arXiv2023

Impact of Charge on Complexity Analysis and Isotropic Decoupled Solutions in $f(\mathbb{R},\mathbb{T})$ Gravity

In this paper, we formulate two exact charged solutions to the field equations by extending the domain of existing anisotropic models with the help of minimal gravitational decoupling in $f(\mathbb{R},\mathbb{T})$ theory. For this, the anisotropic fluid distribution is considered as a seed source that is extended through the inclusion of a new gravitational source. The influence of the later matter configuration is controlled by the decoupling parameter. We formulate the field equations corresponding to the total matter source that are then decoupled into two distinct sets by implementing a transformation only on the radial metric coefficient. Both of these under-determined sets correspond to their parent sources. Some well-behaved forms of the metric potentials are taken into account to deal with the first set of equations. On the other hand, we solve the second set corresponding to an additional source by taking different constraints on the matter sector. We then consider the radius and mass of a compact star $4U~1820-30$ to analyze the physical feasibility of the resulting solutions for a particular modified model. It is concluded that our resulting solutions show stable behavior for certain values of the decoupling parameter and charge.

gr-qc↗

arXiv2023

Effects of Charge and Gravitational Decoupling on Complexity and Isotropization of Anisotropic Models

This paper constructs two immediate extensions of the existing anisotropic solutions in the context of Einstein-Maxwell framework by employing minimal geometric deformation. To achieve this, we assume a static spherical interior initially filled with anisotropic fluid and call it a seed source. We extend this matter configuration by including a new source whose impact on the self-gravitating system is governed by a decoupling parameter. The charged field equations analogous to the total fluid source are formulated. We then implement a transformation on the radial metric potential that divides the field equations into two new under-determined systems, corresponding to the initial and new sources. The first of them is addressed by taking two well-known metric ansatz so that the number of unknowns can be tackled. Further, the vanishing of total anisotropy and complexity-free constraints are used to solve the second set. The estimated radius and mass of a compact star $4U~1820-30$ is utilized to interpret the resulting solutions graphically for different values of the charge and decoupling parameter $ω$. We conclude that our both developed models are physically acceptable for all parametric values except $ω=1$.

gr-qc↗

arXiv2023

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 $\mathcal{Q}=\mathcal{R}_{βξ}\mathcal{T}^{βξ}$. In this regard, a standard model of this modified gravity is taken as $\mathcal{R}+ν_{3}\mathcal{R}_{βξ}\mathcal{T}^{βξ}$, where $ν_{3}$ 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 $ν_{3}$. 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.

gr-qc↗

arXiv2023

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

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arXiv2023

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 $\mathcal{Q}=\mathcal{R}_{ϕψ}\mathcal{T}^{ϕψ}$. For this purpose, we take a linear model of this gravity as $\mathcal{R}+ζ\mathcal{Q}$, where $ζ$ 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 $ζ$.

gr-qc↗

arXiv2023

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-Nordström 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.

gr-qc↗

arXiv2023

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

gr-qc↗

arXiv2023

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 $\mathcal{Q}=\mathcal{R}_{ησ}\mathcal{T}^{ησ}$. 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 $\mathcal{R}+\varpi\mathcal{R}_{ησ}\mathcal{T}^{ησ}$ 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 $\varpi=5$.

gr-qc↗

arXiv2023

Extended Decoupled Anisotropic Solutions in $f(\mathcal{R},\mathcal{T},\mathcal{R}_{γχ}\mathcal{T}^{γχ})$ Gravity

In this paper, we consider static spherical structure to develop some anisotropic solutions by employing the extended gravitational decoupling scheme in the background of $f(\mathcal{R},\mathcal{T},\mathcal{R}_{γχ}\mathcal{T}^{γχ})$ gravity, where $\mathcal{R}$ and $\mathcal{T}$ indicate the Ricci scalar and trace of the energy-momentum tensor, respectively. We transform both radial as well as temporal metric functions and apply them on the field equations that produce two different sets corresponding to the decoupling parameter $ξ$. The first set is associated with isotropic distribution, i.e., modified Krori-Barua solution. The second set is influenced from anisotropic factor and contains unknowns which are determined by taking some constraints. The impact of decoupling parameter is then analyzed on the obtained physical variables and anisotropy. We also investigate energy conditions and some other parameters such as mass, compactness and redshift graphically. It is found that our solution corresponding to pressure-like constraint shows stable behavior throughout in this gravity for the considered range of $ξ$.

gr-qc↗

arXiv2023

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.

gr-qc↗

arXiv2022

Isotropization and Complexity Analysis of Decoupled Solutions in $f(\mathbb{R},\mathbb{T})$ Theory

This paper formulates some new exact solutions to the field equations by means of minimal gravitational decoupling in the context of $f(\mathbb{R},\mathbb{T})$ gravity. For this purpose, we consider anisotropic spherical matter distribution and add an extra source to extend the existing solutions. We apply the transformation only on the radial metric potential that results in two different sets of the modified field equations, each of them corresponding to their parent source. The initial anisotropic source is represented by the first set, and we consider two different well-behaved solutions to close that system. On the other hand, we impose constraints on the additional source to make the second set solvable. We, firstly, employ the isotropization condition which leads to an isotropic system for a particular value of the decoupling parameter. We then use the condition of zero complexity of the total configuration to obtain the other solution. The unknowns are determined by smoothly matching the interior and exterior spacetimes at the hypersurface. The physical viability and stability of the obtained solutions is analyzed by using the mass and radius of a compact star $4U 1820-30$. It is concluded that both of our extended solutions meet all the physical requirements for considered values of the coupling/decoupling parameters.

gr-qc↗

arXiv2022

Quantity over Quality: Training an AV Motion Planner with Large Scale Commodity Vision Data

With the Autonomous Vehicle (AV) industry shifting towards machine-learned approaches for motion planning, the performance of self-driving systems is starting to rely heavily on large quantities of expert driving demonstrations. However, collecting this demonstration data typically involves expensive HD sensor suites (LiDAR + RADAR + cameras), which quickly becomes financially infeasible at the scales required. This motivates the use of commodity sensors like cameras for data collection, which are an order of magnitude cheaper than HD sensor suites, but offer lower fidelity. Leveraging these sensors for training an AV motion planner opens a financially viable path to observe the `long tail' of driving events. As our main contribution we show it is possible to train a high-performance motion planner using commodity vision data which outperforms planners trained on HD-sensor data for a fraction of the cost. To the best of our knowledge, we are the first to demonstrate this using real-world data. We compare the performance of the autonomy system on these two different sensor configurations, and show that we can compensate for the lower sensor fidelity by means of increased quantity: a planner trained on 100h of commodity vision data outperforms the one with 25h of expensive HD data. We also share the engineering challenges we had to tackle to make this work.

cs.RO↗

arXiv2022

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 $\mathcal{R}+Φ\mathcal{Q}$ ($Φ$ is the coupling parameter, $\mathcal{Q}=\mathcal{R}_{φ\vartheta}\mathcal{T}^{φ\vartheta}$) 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.

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