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This article investigates the physical features of static axial sources that produce complexity within the matter configuration within the perspective of f (R ,   T) theory, where R is the curvature invariant and T identifies the trace of matter energy tensor. In this case, the contracted Bianchi identities of effective as well as normal matter are used to develop the conservation equations. We split the curvature tensor to compute structure scalars, involving the physical aspects of the source in the influence of modified factors. We explore the evolving source and compute the complexity of the system. Three complexity factors are determined by using structure scalars; after that, the corresponding propagation equations are explored to investigate the intense gravitational consequences. Finally, the outcomes of irregular anisotropic spheroids are presented using the criterion of vanishing complexity. The f (R ,   T) corrections are shown to be an additional source of complexity for the axial anisotropic configuration. [ABSTRACT FROM AUTHOR]

Employing the Palatini version of f (R) gravity theory (R being the Ricci scalar), this paper describes the evolution of a radiating axially symmetric fluid and its changeover to a non-radiating state. Orthonormal tetrad formalism is taken into account because this technique is easier to use and yields simple tensors leaving the predictions of the theory unchanged. Effective tetrad components of the heat flux, the vorticity vector and the shear tensor are evaluated along with the two parts (electric and magnetic) of Weyl curvature tensor. Furthermore, certain structure scalars are procured from the orthogonal division of the Riemann tensor to figure out basic characteristics of the fluid source like the energy density, stress anisotropy and the heat flux. Few differential equations are worked out to gain insight into the consistency of modified field equations while the system transits from its radiating to equilibrium state. [ABSTRACT FROM AUTHOR]

This work aims to study the bouncing universe under f(G, T) theory of gravity (where G and T are the Gauss–Bonnet invariance and trace of energy–momentum tensor, respectively). We construct modified field equations (MFEs) to analyze the behavior of Hubble parameter (HP) for f (G , T) = G + α G n + 2 λ T with α , λ and (n > 0) are constant terms. Different constraints are applied, engaging HP to examine the accelerating universe and to test initial singularity. The graphical analysis is made for different values of n to explain bouncing process more precisely with respect to cosmic time that also provides an indication of null energy condition (NEC) violation. Resultantly, all mandatory conditions are fulfilled indicating that our proposed model provides good bouncing solutions. [ABSTRACT FROM AUTHOR]

This paper studies the complex mechanism of evolving charged self-gravitational (dissipating or non-dissipating) systems using a structure scalar Y T F , resulting from the basic procedure of orthogonal decomposition of the Riemann–Christoffel curvature tensor. The influence of electrical charge on the complexity of the considered system is analyzed in detail. We find several analytical Einstein–Maxwell models fulfilling the quasi-homologous ( Q H ) evolution plus the vanishing complexity factor ( C F ′ ) condition. Few of the presented models fulfill the Darmois constraints and exhibit shells, however, others satisfy the Israel constraints on both the boundary surfaces. Finally, some possible applications of the presented solutions are mentioned, which are important from astrophysical stand points. It is expected that some of the provided evolving Einstein–Maxwell fluid configurations may be utilized as a toy model of general frameworks like supernova explosions. It is found that the Q H implies the vanishing of the C F and gives rise to a unique and simplest configuration (Friedmann–Lemaître–Robertson–Walker model) fulfilling the condition Y T F = 0 and evolving in the Q H regime. [ABSTRACT FROM AUTHOR]

In this work, the study on static fluid distributions under the influence of electromagnetism has been carried out with an emphasis on the hyperbolically symmetric metric. For this purpose, modified gravitational formulations in the presence of charge are used to calculate the effective energy–momentum tensor, which is then further refined by taking into account tetrad field components in the Minkowski coordinate system. Also, we compute the Tolman mass and a suitable formulation of the mass function. It exhibits that the hyperbolically symmetrical source has a negative effective matter density in all stellar formulations. This demonstrates that the quantum processes together with certain excessive constraints are deemed important to explain any physical implementations under the effects of the electromagnetic field. Additionally, we assessed the structure scalars and implemented the orthogonal splitting of the structure scalars and Riemann tensor in this modified gravity. Subsequently, various explicit precise cosmological solutions and their generating functions are developed. [ABSTRACT FROM AUTHOR]

This work probes the influence of charge field on the unique stellar structure, regarded as gravastar, under the corrections of f () theory, i.e. (ℬ) theory, where is named as Gauss–Bonnet invariant. The gravastar has also been recognized as an alternate candidate of black hole structure and is illustrated by three distinct regions termed as (1) the exterior (2) the intermediate thin shell (3) the interior domain. We discussed the mathematical solutions for each of three regions separately with the assistance of different equation-of-states (EoS). The exterior charged vacuum domain is expressed by the Reissner–Nordström solution. The central region is illustrated by the EoS, i.e. a positive pressure of ultra-relativistic matter is equal to the energy density. Whereas, the interior domain reflects that the negative pressure is equal to energy density and manifests a non-attractive force over the central spherical shell. We deduce that in the context of ℬ theory, the nonsingular charged model with distinct physical features, such as energy, length, entropy, is physically viable and consistent. [ABSTRACT FROM AUTHOR]

In this paper, we analyze a few physical characteristics of gravastar with cylindrical geometry in f (R , T) theory, where R is the Ricci scalar and T is the trace of energy-momentum tensor. The gravastar is generally considered to be a substitute of a black hole with three different regions. In this work, we examine the formulation of gravastar-like cylindrical structures in f (R , T) theory. By using Darmois and Israel matching conditions, we formulate a mass function of a thin shell. We calculate the different physical characteristics of gravastar, in particular, entropy within the thin shell, proper length of the intermediate thin shell as well as energy of the shell. [ABSTRACT FROM AUTHOR]

We explore the aspects of the electromagnetism on the stability of gravastar in a particular modified theory, i.e. f (R , T , Q) where Q = R μ ν T μ ν , R is the Ricci scalar and T is the trace of energy–momentum tensor. We assume a spherically symmetric static metric coupled comprising of perfect fluid in the presence of electric charge. The purpose of this paper is to extend the results of [S. Ghosh, F. Rahaman, B. K. Guha and S. Ray, Phys. Lett. B767 (2017) 380.] to highlight the effects of f (R , T , Q) gravity in the formation of charged gravastars. We demonstrated the mathematical formulation, utilizing different equations of state, for the three respective regions (i.e. inner, shell, exterior) of the gravastar. We have matched smoothly the interior de Sitter and the exterior Reissner–Nordström metric at the hypersurface. At the end we extracted few conclusions by working on the physical features of the charged gravastar, mathematically and graphically. [ABSTRACT FROM AUTHOR]

The aim of this paper is to generalize the definition of complexity for the static self-gravitating structure in f  (R, T, Q) gravitational theory, where R is the Ricci scalar, T is the trace part of energy–momentum tensor, and Q ≡ R αβ T  αβ. In this context, we have considered locally anisotropic spherical matter distribution and calculated field equations and conservation laws. After the orthogonal splitting of the Riemann curvature tensor, we found the corresponding complexity factor with the help of structure scalars. It is seen that the system may have zero complexity factor if the effects of energy density inhomogeneity and pressure anisotropy cancel the effects of each other. All of our results reduce to general relativity on assuming f  (R, T, Q) = R condition. [ABSTRACT FROM AUTHOR]

We consider the definition of complexity for dynamical spherically self-gravitating matter distribution in the presence of heat dissipation introduced by Herrera [L. Herrera, A. Di Prisco and J. Ospino, Phys. Rev. D 98 (2018) 104059] and generalize it in f (R , T , R μ ν T μ ν) gravity, where R and T are the Ricci scalar and the trace of energy–momentum tensor, respectively. We measure the complexity of structure as well as pattern of evolution of the fluid distribution and examine these under the effects of dark source terms of modified gravity. Some dynamical and kinematical equations are observed in the dissipative and nondissipative cases in the background of modified theory. Finally, we discuss evolution of the structure scalars and stability of a condition where the complexity factor vanishes. [ABSTRACT FROM AUTHOR]

In this paper, we study the importance of configurations of the observer's congruences in the analysis of the dynamical properties of planar relativistic systems in f (R) geometry. To this end, we assume a relativistic distribution of matter contents whose gravitational effects would produce planar geometry. In order to relate matter ingredients seen by tilted and non-tilted observers, we have calculated particular theoretical relationships. After calculating dynamical, Ellis and transport equations, the pace of gravitational collapse as well as the corresponding stable epochs of the systems are discussed. The instability of non-comoving reference frame has been elaborated in a particular background. [ABSTRACT FROM AUTHOR]

In this article, we explore a few less complex models for the charged spherically symmetric structures. We take an anisotropic and static fluid distribution experiencing co-moving coordinate system. After using orthogonal splitting technique, we formulate two different formulations of stellar mass that would be then expressed in the values of structure scalars. A structure scalar Y T F is found to complexity factor that would lead us to study various characteristics of the relativistic spherical interiors. It is noticed that this factor disappears for both homogeneous isotropic fluids and inhomogeneous anisotropic gravitating source. Finally, we evaluate some theoretical models after using vanishing complexity condition. • We explore less complex models for the charged spheres. • We formulate two different forms of stellar mass in the structure scalars. • We evaluate some theoretical models with vanishing complexity condition. [ABSTRACT FROM AUTHOR]

This paper is aimed to set up a thin-shell gravastar model and address its physically accepted features in the background of noncommutative geometry. For this purpose, we have considered the cylindrically symmetric interior metric matched with suitable noncommutative exterior geometry using Israel boundary conditions. The stability of this thin-shell as well as thermodynamical stability is then explored under linear perturbations around the throat. We have found the stable regions near the horizon with some specific values of the involved parameters. [ABSTRACT FROM AUTHOR]

This paper studies the viable regions of some cosmic models in a higher derivative f (R , □ R , T) theory with the help of energy conditions (where R , □ and T are the Ricci scalar, d'Alembert's operator and trace of energy–momentum tensor, respectively). For this purpose, we assume a flat Friedmann–Lemaître–Robertson–Walker metric which is assumed to be filled with perfect fluid configurations. We take two distinct realistic models that might be helpful to explore stable regimes of cosmological solutions. After taking some numerical values of cosmic parameters, like crackle, snap, jerk (etc.) as well as viable constraints from energy conditions, the viable zones for the under observed f (R , □ R , T) models are examined. [ABSTRACT FROM AUTHOR]

Assuming a system with spherical symmetry in f(R) gravity filled with dissipative charged and anisotropic matter, we study the impact of density inhomogeneity and local anisotropy on the gravitational collapse in the presence of charge. For this purpose, we evaluated the modified Maxwell field equations, Weyl curvature tensor, and the mass function. Using Misner–Sharp mass formalism, we construct a relation between the Weyl tensor, density inhomogeneity, and local anisotropy. Specifically, we obtain the expression of modified Tolman mass which helps to analyze the influence of charge and dark source terms on different physical factors, also it helps to study the role of these factors on gravitational collapse. [ABSTRACT FROM AUTHOR]

This paper is aimed to study thermodynamical properties of phase transition for regular charged black holes (BHs). In this context, we have considered two different forms of BH metrics supplemented with exponential and logistic distribution functions and investigated the recent expansion of phase transition through grand canonical ensemble. After exploring the corresponding Ehrenfest’s equation, we found the second-order background of phase transition at critical points. In order to check the critical behavior of regular BHs, we have evaluated some corresponding explicit relations for the critical temperature, pressure and volume and draw certain graphs with constant values of Smarr’s mass. We found that for the BH metric with exponential configuration function, the phase transition curves are divergent near the critical points, while glassy phase transition has been observed for the Ayón–Beato-García–Bronnikov (ABGB) BH in n = 5 dimensions. [ABSTRACT FROM AUTHOR]

The aim of this paper is to explore some physically viable aspects for the possible emergence of compact stars in theory of gravity with some particular models, where and are Gauss-Bonnet invariant and trace of stress-energy tensor, respectively. We present basic formalism of this modified theory in the presence of anisotropic source. We explore some realistic aspects using the energy conditions with physical parameters. Three distinct known star models namely, and , are used for this systematic investigation. The physical behavior of anisotropic stresses, energy density, energy conditions, measure of anisotropy and stability of compact stars are discussed through plots. We conclude that compactness at the core of a star model increases and energy conditions hold. [ABSTRACT FROM AUTHOR]

In this paper, we study the impact of three different $f(R,T)$ models in the modeling of anisotropic relativistic stellar structures, where $R$ is the Ricci scalar and $T$ is the trace of the energy-momentum tensor. For this purpose, we assume static geometry of spherically symmetric self-gravitating object and after choosing appropriate vacuum solution, we evaluated some constraints for the smooth matching of exterior and interior geometries at the boundary surface. We considered observational values of three well-known stellar structures and checked the viability of energy conditions in the presence of quadratic, exponential and cubic $f(R,T)$ models. The distributions of energy density, behavior of anisotropic pressure, role of fundamental gravitational forces as well as stability investigation have been performed through plots in the realistic modeling of compact stars. We infer that modified gravitational theories could be treated as viable tool to study the existence of compact stellar structures at both theoretical and cosmological scales. [ABSTRACT FROM AUTHOR]

This paper aims to explore some realistic configurations of anisotropic spherical structures in the background of metric f( R) gravity, where R is the Ricci scalar. The solutions obtained by Krori and Barua are used to examine the nature of particular compact stars with three different modified gravity models. The behavior of material variables is analyzed through plots and the physical viability of compact stars is investigated through energy conditions. We also discuss the behavior of different forces, equation of state parameter, measure of anisotropy and Tolman-Oppenheimer-Volkoff equation in the modeling of stellar structures. The comparison from our graphical representations may provide evidence for the realistic and viable f( R) gravity models at both theoretical and the astrophysical scale. [ABSTRACT FROM AUTHOR]

This manuscript studies the inhomogeneity in the energy density for the relativistic dynamical charged system by invoking the outcomes coming from the considered anisotropic distribution of radiating fluid. We use newly developed f (G , T 2) theory, which was proposed by the addition of T 2 = T ζ ξ T ζ ξ in the usual action of f (G ,) gravity. We construct relativistic field equations for a specific model f (G , T 2) = λ T 2 + G (1 + G α) , to examine the gravitational structure in the influence of electromagnetic filed. We use dynamical expressions and differential equations for Weyl tensor for the inspection of sources of irregularities. By exploring special cases in the non-radiating and radiating scenarios, the irregularity elements for a fluid are examined. These special cases show that modified terms and charge have a considerable impact on the fluid inhomogeneity. • This manuscript studies the inhomogeneity in the energy density for the relativistic charged spherical system. • After constructing the evolution equations for Weyl tensor, we analyzed the sources of irregular energy density over the initially homogeneous objects. • The structure variable is found to be responsible for pushing the locally anisotropic system to enter in the inhomogeneous phase. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated the role of different fluid parameters particularly electromagnetic field and f(R) corrections on the evolution of cylindrical compact object. We have explored the modified field equations, kinematical quantities and dynamical equations. An expression for the mass function has been found in comparison with the Misner-Sharp formalism in modified gravity, after which different mass-radius diagrams are drawn. The coupled dynamical transport equation have been formulated to discuss the role of thermoinertial effects on the inertial mass density of the cylindrical relativistic interior. Finally, we have presented a framework, according to which all possible solutions of the metric f(R)-Maxwell field equations coupled with static fluid can be written through set of scalar functions. It is found that modified gravity induced by Lagrangians f(R) = αR2, f(R) = αR2 - βR and f (R) = αR2-βR 1+γR are likely to host more massive cylindrical compact objects with smaller radii as compared to general relativity. [ABSTRACT FROM AUTHOR]

The basic objective of this investigation is to explore the impact of a novel gravitational modification, specifically, the f (G , T 2) (where T 2 ≡ T α β T α β , T α β denotes the stress–energy tensor) model of gravitation, upon the complexity of time-dependent dissipative as well as non-dissipative spherically symmetric celestial structures. To find the complexity factor (ℂ F) from the generic version of the structural variables, we performed Herrera's scheme for the orthogonal splitting of Riemann tensor. In this endeavor, we are mainly concerned with the issue of relativistic gravitational collapse of the dynamically relativistic spheres fulfilling the presumption of minimal ℂ F. The incorporation of a less restrictive condition termed as quasi-homologous (Q H) condition together with the zero ℂ F , allows us to formulate a range of exact solutions for a particular choice of f (G , T 2) model. We find that some of the given exact solutions relax the Darmois junction conditions and describe thin shells by satisfying the Israel conditions, while some exhibit voids by fulfilling the Darmois constraints on both boundary surfaces. Eventually, few expected applications of the provided solutions in the era of modern cosmology are debated. [ABSTRACT FROM AUTHOR]

In this paper, we study the effects of polynomial f( R) model on the stability of homogeneous energy density in self-gravitating spherical stellar object. For this purpose, we construct couple of evolution equations which relate the Weyl tensor with matter parameters. We explore different factors responsible for density inhomogeneities with non-dissipative dust, isotropic as well as anisotropic fluids and dissipative dust cloud. We find that shear, pressure, dissipative parameters and f( R) terms affect the existence of inhomogeneous energy density. [ABSTRACT FROM AUTHOR]

This paper performs stability analysis of an adiabatic anisotropic cylindrical collapsing system in metric f(R) gravity. We construct general collapse equation from the dynamical equation through perturbation scheme. It is found that the dynamical stability of the system evolving with and without expansion at both Newtonian as well as post-Newtonian orders is controlled by the extra curvature f(R) gravity terms, radial density profile and pressure of the fluid. We conclude that the adiabatic index Γ1 or stiffness parameter plays a key role only if the system evolves with expansion scalar. We also reduce our solutions to constant curvature as well as f(R)→R limits. [ABSTRACT FROM AUTHOR]

This paper is devoted to understanding a few characteristics of static irrotational matter content that assumes hyperbolical symmetry. For this purpose, we use metric f (R) gravity to carry out our analysis. It is noticed that the matter distribution cannot fill the region close to the center of symmetry, thereby implying the existence of an empty core. Moreover, the evaluation of the effective energy density reveals that it is inevitably negative, which could have utmost relevance in understanding various quantum field events. To derive the structure scalars, we perform the orthogonal splitting of the Riemann tensor in this modified gravity. Few relationships among matter variables and both Tolman and Misner Sharp are determined. Through two generating functions, some hyperbolically symmetric cosmological models, as well as their physical interpretations, are studied. To delve deeply into the role of f (R) terms, the model of the less-complex relativistic system of Einstein gravity is presented. [ABSTRACT FROM AUTHOR]

The aim of this paper is to analyse the role of electromagnetic field and a viable Carroll–Duvvuri–Trodden–Turner (CDTT) model, $f(R)=R+\rho \frac{{\delta }^4}{R}$, in the range of dynamical instability. We assume non-viscous charged collapsing cylindrical star with heat flux dissipation. We formulate dynamical equations through perturbation scheme on the metric variables which eventually cause perturbation on physical variables as well as chosen f (R) model. The evolution of the matter variables is discussed with the help of these equations. It is concluded that the range of dynamical instability depends upon the electric field intensity, density profile, pressure and the curvature terms of the CDTT model. We find that our results of Newtonian and post-Newtonian regimes reduce asymptotically to General Relativity solutions as δ → 0. [ABSTRACT FROM AUTHOR]

We investigate some analytical models of the plane symmetric distribution of anisotropic fluid with vanishing expansion scalar. Darmois junction conditions, on both the internal and external hypersurfaces, are given. A relationship between the Weyl tensor and the matter variables is developed. We explore four families of solutions under expansion-free condition some of which indicate the presence of thin shell, while some others satisfy junction conditions. It is shown that the Skripkin model is incompatible with junction conditions in the plane symmetry. [ABSTRACT FROM AUTHOR]

This manuscript is devoted to a general study on axial and reflection-symmetric self-gravitating sources in the background of f (R , T) gravity, where T represents the trace of stress energy-tensor, while R is the Ricci scalar. For this purpose, all the fundamental equations and notions set to carry out the general study are established. The corresponding field, as well as dynamical equations, are also exhibited. In order to discuss the thermodynamics aspects of the selected system, the modified transport equation is presented. The Weyl-tensor is utilized to evaluate the generalized version of scalar variables termed structure scalars. To produce modified scalar equations, we employ the structure scalars. The applications of our obtained results are examined on the dynamics of the source in f (R , T) gravity. We conclude that the modified structure scalars play an important role in the dynamics of compact objects. • The relativistic equations for axial and reflection-symmetric system are calculated. • Modified transport equation is presented to discuss the thermodynamics of the system • The results are studied on the dynamics of the source in f (R , T) gravity. [ABSTRACT FROM AUTHOR]

This paper studies the evolutionary mechanism of the relativistic spherically symmetric spacetime who is coupled with both radiating and non-radiating matter content in f (R , T) gravity. This modeled system is assumed to obey the constraint of minimal complexity having areal radius velocity to be proportional to the areal radius, i.e., quasi-homologous condition. The corresponding few exact analytical solutions are examined with some realistic background. Our few models described the emergence of Minowskian cavity around the center of the relativistic spherical structure. We also calculated the structure scalars in modified gravity that are gained by splitting the Riemann tensor orthogonally. The structure scalar Y T F e f f is found to the complexity factor. Various realistic applications of our calculated models in relativistic astrophysics are described. • Evolutionary mechanism of relativistic star will be studied in f (R , T) gravity. • It obeys the constraint of minimal complexity with quasi-homologous condition. • Some exact analytical solutions are explored with realistic background. [ABSTRACT FROM AUTHOR]

• The aim of this paper is to present the definition of complexity for static self-gravitating anisotropic matter proposed in f (G , T) theory, where G is the Gauss-Bonnet term and T is the trace of energy momentum tensor. • Among the calculated modified scalar variables that are obtained from the orthogonal splitting of Riemann tensor, a single scalar function has been identified as the complexity factor. • After exploring the corresponding Tolmann mass function, it is seen that the complexity factor along with the f (G , T) terms have greatly influenced its formulation and its role in the subsequent radial phases of the spherical system. The aim of this paper is to present the definition of complexity for static self-gravitating anisotropic matter proposed in f (G , T) theory, where G is the Gauss-Bonnet term and T is the trace of energy momentum tensor. We evaluate field equations, Tolman-Oppenheimer-Volkoff equation, mass functions and structure scalars. Among the calculated modified scalar variables that are obtained from the orthogonal splitting of Riemann tensor, a single scalar function has been identified as the complexity factor. After exploring the corresponding Tolmann mass function, it is seen that the complexity factor along with the f (G , T) terms have greatly influenced its formulation and its role in the subsequent radial phases of the spherical system. We have also used couple of ansatz in order to discuss possible solutions of equations of motion in the study of the structure of compact object. [ABSTRACT FROM AUTHOR]

• A new solution of charged gravastars with isotropic matter configuration in the framework of f (R, T) theory of gravity has been presented. • We present an exact solution that free from event horizon and non-singular for this our new model. • We have found some physical aspects like length, energy, entropy and equation of state for charged spherical gravastar distribution. We have studied a new solution of charged gravastars with isotropic matter configuration in the framework of f (R, T) theory of gravity. For this purpose, we have assumed the electric charge as a constant. This stellar structure divided into three different regions: The preliminary part shows the interior charged region in which pressure equals to the negative density, second is the intermediate charged shell which is assumed to be very thin and filled with ultrarelativistic stiff fluid and the last corresponds to the electrovacuum region which is defined by an exterior Reissner-Nordström solution. Under these assumptions, we have found some physical aspects like length, energy, entropy and equation of state for charged spherical gravastar distribution. Moreover, we present an exact solution that free from event horizon and non-singular for this our new model. [ABSTRACT FROM AUTHOR]

In this paper, we investigate irregularities in a cylindrical self-gravitating system which contains the properties of an imperfect matter and electromagnetic field. For f (R , T , Q) theory, in which R represents the Ricci scalar and T shows the trace of matter stress–energy tensor while Q ≡ R γ δ T γ δ , the field equations containing electric charge, mass functions and Darmois junction conditions at the hypersurface are examined. We have adopted new definition of complexity introduced by Herrera (2018), generalized it for the static charged cylindrically symmetric case in f (R , T , Q) theory by performing a detailed analysis on the orthogonal splitting of the Riemann curvature tensor. One of the effective scalars, Y T F , has been recognized as a complexity factor. This factor is comprised of certain physical components of the fluid such as irregularity in energy density, locally pressure anisotropy and electric charge (arranged in a specific way). In addition, the effects of extra curvature terms of modified gravity are examined by making the relations among the complexity factor, Weyl scalar and Tolman mass. [ABSTRACT FROM AUTHOR]

This paper is devoted to present new definition of complexity factor for static cylindrically symmetric matter configurations in f (R , T , R μ ν T μ ν) gravity. For this purpose, we have considered irrotational static cylindrical spacetime coupled with a locally anisotropic relativistic fluid. After formulating gravitational field and conservation equations, we have performed orthogonal splitting of the Riemann curvature tensor. Unlike GR (for spherical case) the one of the structure scalars X T F , has been identified to be a complexity factor. This factor contains effective forms of the energy density, and anisotropic pressure components. Few peculiar relations among complexity factor, Tolman mass and Weyl scalar are also analyzed with the modified f (R , T , R μ ν T μ ν) corrections. [ABSTRACT FROM AUTHOR]

This work is devoted to study the analytical and regular solutions of a particular self-gravitating object (i.e., gravastar) in a particular theory of gravity. We derive the corresponding field equations in the presence of effective energy momentum tensor associated with the perfect fluid configuration of a spherical system. We then describe the mathematical formulations of the three respective regions i.e., inner, shell and exterior of a gravastar separately. Additionally, the significance and physical characteristics along with the graphical representation of gravastars are discussed in detail. It is seen that under some specific constraints, f (R , T , R μ ν T μ ν) gravity is likely to host gravastars. [ABSTRACT FROM AUTHOR]

In this work, we extend the work of gravastars to analyze the role of electromagnetic field in f (R , T) gravity. We consider the irrotational cylindrically symmetric geometry and established the f (R , T) field equations and conservation laws. After considering charged exterior geometry, the mathematical quantities for evaluating Israel junction conditions are being calculated. The mass of the gravastar-like cylindrical structure is calculated through the equations of motion at the hypersurface in the presence of an electromagnetic field. The behavior of electric charge on the length of the thin shell, energy content, and entropy of gravastar is being studied graphically. We concluded that charge has an important role in the length of the thin shell, energy content, and entropy of gravastar. [ABSTRACT FROM AUTHOR]

This manuscript aims to discuss the factors holding in/stability of axially symmetric compact system with anisotropic environment in the background of f (R , T) gravity, where R is invariant Ricci curvature and T stands for trace of energy–momentum tensor. We constituted field and conservation equations in the background of f (R , T) gravity. To establish the collapse equation, we make use of perturbation for all the variables involving in conservation equations, field equations, extra curvature terms of modified gravity and the particular f (R , T) model. To estimate dynamical in/stability of celestial compact system, we acquired some meaningful constraints for adiabatic index γ in Newtonian and Post Newtonian domains. Also, some constraints are imposed on physical quantities to maintain the stability of celestial self-gravitating astrophysical configuration. [ABSTRACT FROM AUTHOR]

Abstract This paper explores the circular geodesics of neutral test particles on an equatorial plane around a rotating black hole. After using equations of motion of scalar-tensor-vector gravity with the circular geodesics of null-like particles, we find the equation of photon orbit. With the help of an effective potential form, we have examined the stable regimes of photons orbits. The Lyapunov exponent, as well as the effective force acting on photons, is also investigated. We examine the energy extraction from a black hole via Penrose process. Furthermore, we discuss the negative energy state and the efficiency of energy extraction. We have made compare our results with that obtained for some well known black holes models. We concluded that the efficiency of the energy extraction decreases with the increase of dimensionless parameter of theory and increases as spin parameter increases. [ABSTRACT FROM AUTHOR]

• The phenomena of gravitational collapse of a unidirectional isotropic matter configuration. • The junction conditions for a static exterior geometry and the non-static interior geometry are evaluated. • We have calculated the time lapse for the appearance of the black hole and cosmological horizon. • We observed that in the de-Sitter space, the unidirectional perfect fluid flow does not make the collapse disappear. • We fund that the presence of string tension increases the time lapse of horizon formation. This paper explores the collapsing process of a unidirectional isotropic matter configuration. The junction conditions for a static exterior geometry and the non-static interior geometry are expressed in terms of the cosmological constant. The time-lapse for the appearance of the black hole and the cosmological horizon is calculated. It is observed that in the de-Sitter space, the unidirectional perfect fluid flow does not make the collapse disappear. The vacuum energy of the cosmological constant makes the collapsing process quite slow and affects the time-lapse of horizon formation. Moreover, the presence of string tension increases the time-lapse of horizon formation. [ABSTRACT FROM AUTHOR]