Search

A nanoflower structure of Zn 0. 7 6 Co 0. 2 4 S directly grown on carbon fiber papers (CFP) was successfully designed by a mild two-step hydrothermal method. Benefiting from their fascinating structural features, Zn 0. 7 6 Co 0. 2 4 S/CFP electrode exhibits a maximum specific capacitance of 300 F g − 1 at current density of 1 A g − 1 and 84% capacitance retention after 5,000 cycles at current density of 5 A g − 1 . Subsequently, Zn 0. 7 6 Co 0. 2 4 S/CFP//AC all-solid-state asymmetric supercapacitor (ASC) device is assembled and able to illuminate the red LEDs. ASC devices deliver a maximum energy density of 9.59 W h kg − 1 at a power density of 750 W kg − 1 . Therefore, this impressive result demonstrates that the nanoflower Zn 0. 7 6 Co 0. 2 4 S have promising applications in the development of high-performance supercapacitors. Zn0.76Co0.24S/CFP was obtained using two-step hydrothermal method. Its microstructure presents a novel nanoflower arrays. The synergistic effect between Zn0.76Co0.24S nanoflower and CFP improves the electrons transport efficiency, conductivity and structural stability of the hybrid. The as-prepared Zn0.76Co0.24S/CFP electrode delivers a specific capacitances of 300 F g−1 and exhibits an excellent cycling stability (retaining 84% after 5000 cycles) as well as a high energy density of 9.59 W h kg−1. [ABSTRACT FROM AUTHOR]

NiCo2S4/CNTs (NCS/CNTs) hybrid nanostructures have been synthesized by a facile one-step solvothermal method with varying content of CNTs. The structure and morphology of the synthesized NCS/CNTs hybrid revealed the formation of platelets anchored on the CNT matrix. When evaluated as electrode materials for supercapacitor, the as-synthesized NCS/CNT-1 hybrid (with 1% of CNT) manifested remarkable specific capacitance of 1690 F g − 1 at the current density of 5 A g − 1 . More importantly, an asymmetric supercapacitor (ASC) assembled based on NCS/CNT-1 as positive electrode and carbon nanotube paper (CNP) as a negative electrode delivered high energy density of 58 Wh kg − 1 under power density of 8 kW kg − 1 . Furthermore, the ASC device exhibited high cycling stability and 77.7% of initial specific capacitance retention after 7000 charge–discharge cycles at a current density of 8 A g − 1 . The large enhancement in the electrochemical performance is attributed to the benefits of the nanostructured architecture, including good mechanical stability, high electrical conductivity as well as buffering for the volume changes during charge–discharge process. These convincing results show that NCS/CNTs hybrid nanostructures are promising electrode materials for high energy density supercapacitors (SCs). [ABSTRACT FROM AUTHOR]

High performance dielectric capacitors are ubiquitous components in the modern electronics industry, owing to the highest power density, fastest charge–discharge rates, and long lifetime. However, the wide application of dielectric capacitors is limited owing to the low energy density. Over the past decades, multiscale structures of dielectric ceramics have been extensively explored and many exciting developments have been achieved. Despite the rapid development of energy storage properties, the atomic structure of dielectric materials is rarely investigated. In this paper, we present a brief overview of how scanning transmission electron microscopy (STEM) is used as a tool to elucidate the morphology, local structure heterogeneity, atomic resolution structure phase evolution and the correlation with energy storage properties, which provides a powerful tool for rational design and synergistic optimization. [ABSTRACT FROM AUTHOR]

In this paper, spin polarized domain walls in Einstein–Cartan (EC) gravity have been recently investigated [L. C. Garcia de Andrade, Einstein–Cartan non-supersymmetric dynamo walls, Ann. Phys. 432 (2021).], where the spin polarizes along the direction orthogonal to planar domain wall. In this case, dynamo effects may appear on the wall. Moreover, dilatonic domain walls (DDWs) have shown to be responsible for inflating DWs in EC gravity, where DWs were non-magnetized [L. Garcia de Andrade, Axial and chiral anomalies in Riemann–Cartan spacetime black holes and electrodynamics, Class. Quantum Grav. 16 (1999) 2097–2103.]. In this paper, our goal is to show that when we consider a magnetized DW in the EC–Maxwell cosmology, the dilaton potential in the form of a DDW potential expressed in terms of torsion and the magnetic energy density may drive dynamo effects. Analytical solution of the dynamo equation shows that depending on the handness of DDW metric, the magnetic fields are amplified by dynamo action. From the coupled system of ECM and dilaton field equations, we find a relation between the magnetic energy density of 1 0 − 3 8 G 2 and the DDW torsion of 1 0 − 1 7 cm − 1 = 1 0 − 3 1 GeV which leads to a thin DDW thickness of 1 fm. For a galactic magnetic field, energy density of 1 0 − 1 2 G 2 leads to a thickness of 1 0 1 8 fm , a much thinner DDW. For galactic dynamo amplification, the ratio r between the magnetic energy density and photon energy density is around 1 0 − 3 4 . From this ratio, a relation between photon mass density and torsion is obtained. Chiral Magnetic effect (CME), torsion and magnetic discontinuities along the wall are investigated. Magnetic field discontinuity across the wall allows us to understand why the magnetic fields at DDW must be located along the wall since the orthogonal magnetic field may vanish. [ABSTRACT FROM AUTHOR]

In Einstein's General Relativity (GR), the gravitational interactions are described by the spacetime curvature. Recently, other alternative geometric formulations and representations of GR have emerged in which the gravitational interactions are described by the so-called torsion or non-metricity. Here, we consider the recently proposed modified symmetric teleparallel theory of gravity or f (Q) gravity, where Q represents the non-metricity scalar. In this paper, motivated by several papers in the literature, we assume the power-law form of the function f (Q) as f (Q) = α Q n + 1 + β , (where α , β , and n are free model parameters) that contains two models: Linear (n = 0) and nonlinear (n ≠ 0). Further, to add constraints to the field equations we assume the deceleration parameter form as a divergence-free parametrization. Then, we discuss the behavior of various cosmographic and cosmological parameters such as the jerk, snap, lerk, O m diagnostic, cosmic energy density, isotropic pressure, and equation of state (EoS) parameter with a check of the violation of the strong energy condition (SEC) to obtain the acceleration phase of the Universe. Hence, we conclude that our cosmological f (Q) models behave like quintessence dark energy (DE). [ABSTRACT FROM AUTHOR]

In materials that undergo martensitic phase transformation, distinct elastic phases often form layered microstructures — a phenomenon known as twinning. In some settings the volume fractions of the phases vary macroscopically; this has been seen, in particular, in experiments involving the bending of a bar. We study a two-dimensional (2D) model problem of this type, involving two geometrically nonlinear phases with a single rank-one connection. We adopt a variational perspective, focusing on the minimization of elastic plus surface energy. To get started, we show that twinning with variable volume fraction must occur when bending is imposed by a Dirichlet-type boundary condition. We then turn to paper's main goal, which is to determine how the minimum energy scales with respect to the surface energy density and the transformation strain. Our analysis combines ansatz-based upper bounds with ansatz-free lower bounds. For the upper bounds we consider two very different candidates for the microstructure: one that involves self-similar refinement of its length scale near the boundary, and another based on piecewise-linear approximation with a single length scale. Our lower bounds adapt methods previously introduced by Chan and Conti to address a problem involving twinning with constant volume fraction. The energy minimization problem considered in this paper is not intended to model twinning with variable volume fraction involving two martensite variants; rather, it provides a convenient starting point for the development of a mathematical toolkit for the study of twinning with variable volume fraction. [ABSTRACT FROM AUTHOR]

In this paper, we consider a simple, purely stochastic model characterized by two conserved quantities (mass density a and energy density h) which is known to display a condensation transition when h > 2 a 2 : in the localized phase a single site hosts a finite fraction of the whole energy. Its equilibrium properties in the thermodynamic limit are known and in a recent paper [G. Gotti, S. Iubini and P. Politi, Finite-size localization scenarios in condensation transitions, Phys. Rev. E 103 (2021) 052133] we studied the transition for finite systems. Here, we analyze finite-size effects on the energy distribution and on the relaxation dynamics, showing that extremely large systems should be studied in order to observe the asymptotic distribution and even larger systems should be simulated in order to observe the expected relaxation dynamics. [ABSTRACT FROM AUTHOR]

Smoothed particle hydrodynamics (SPH) has its unique advantages in simulating large deformation. However, in its calculation, it is easy for some regional particles to break off. This paper puts forward the concept of virtual crack boundary to solve crack propagating problems in the framework of SPH. The parameters of virtual crack boundary are determined by the projection method of descending dimension, which improves the support domains of crack tip particles. Based on the principle of minimum strain energy density factor in fracture mechanics, the initiation and extended directions of cracks in materials are estimated. By simulating the generation and expansion of three modes of cracks in materials, the SPH calculation results of the three types of support domain forms are compared with the ABAQUS simulation results and experiment results. It indicates that the method of virtual crack boundary method is more stable than the one based on discontinuous medium. And it can generate more reasonable results than the method based on continuous medium. This paper proves the effectiveness of strain energy density factor based on fracture mechanics theory in searching the direction of crack expansion using SPH, and explores the application of new support domain model in SPH crack solution. [ABSTRACT FROM AUTHOR]

This paper further studies the cosmological evolution and geometry diagnosis of Barrow holographic dark energy (BHDE) in the DGP braneworld, specifically, by choosing the interaction between dark energy and dark matter item. Q 1 = 3 H ξ ρ de , Q 2 = 3 H ξ ρ dm , Q 3 = 3 H ξ ρ de 2 / (ρ de + ρ dm ) , Q 4 = 3 H ξ ρ dm 2 / (ρ de + ρ dm ) are discussed in the case of no interaction and four different interactions, the evolution laws of energy density parameters, deceleration parameters and EOS (equation of state) parameters of Barrow holographic dark energy. The results show that the Barrow holographic dark energy in the DGP braneworld conforms to the current cosmic evolution rule, already achieved the universe main ingredients from matter to the transition of energy, and explains the problem of cosmic acceleration. Further, in order to distinguish between the model and Λ CDM model, this paper also geometrically diagnoses the model with the two ways of Statefinder hierarchy and Om (z). From their respective evolution image you can see, these two kinds of diagnosis methods can not only distinguish different from Λ CDM model, but also can intuitively reflect the coupling parameters that can significantly affect the dark energy model. [ABSTRACT FROM AUTHOR]

In this paper, we study the accretion process of a charged black hole in the background of cloud of strings in the framework of 4D Einstein–Gauss–Bonnet (EGB) gravity theory. Firstly, the steady spherical accretion process of ideal fluid on 4D cloud of strings EGB black hole is studied from the aspects of the radial velocity, the energy density, the mass accretion rate and the sound speed. Then, the general analytical expressions of the accretion process are determined, and the effects of the black hole parameters on the radial velocity, the energy density, the mass accretion rate and the sound velocity are discussed. When the GB coupling constant increases, the energy density and mass accretion rate increase, and the sound velocity and radial speed decrease. EGB gravity and charge have similar physical effects on the accretion process of black hole. [ABSTRACT FROM AUTHOR]

Dielectric capacitors are receiving increasing attention due to the high-power density and fast charge–discharge speed. However, defects are inevitably induced during the preparation process and then weaken the breakdown strength, thereby limiting their energy density. The phenomenon gives rise to self-healing technology. The discovery of sol–gel-derived aluminum oxide with electrolysis and dielectric dual-characteristic provides a novel, simple and cost-effective self-healing method to heal defects and enhance energy density. In this paper, we systematically reviewed the current self-healing technologies and the important progress of electrolysis and dielectric co-existence dielectrics. Finally, we outlook the electrolysis and dielectric co-existence dielectrics and potential challenge. [ABSTRACT FROM AUTHOR]

This paper explores the existence of static wormholes in 4-Dimensional Einstein Gauss–Bonnet (4D EGB) gravity. We discuss some possibilities for constructing radial-dependent shape functions via different strategies to develop some non-conventional wormhole geometries by considering anisotropic matter sources. In this regard, we assume a specific form of the equation of state and investigate its effects on Gauss–Bonnet (GB) coupling parameter. Next, we impose a traceless condition on the anisotropic fluid distribution as well as radial-dependent energy density profile to explore wormhole geometries as separate cases. It is seen that the obtained results can be reduced into Morris–Throne wormholes for the zero value of GB-coupled parameter for anisotropic fluid distribution. Furthermore, we scrutinize flaring-out conditions and examine asymptotically flatness constraints for the existence of wormholes. Our analysis shows that the weak energy condition (WEC) is satisfied for a particular range by constraining GB-coupled parameter. We study the dynamics of GB-coupled parameter for both cases μ > 0 and μ < 0. It is concluded that wormhole solutions are possible for μ > 0 and, in some cases, μ < 0. The active gravitational mass of developed wormholes is calculated and plotted graphically. The wormhole geometry is discussed by plotting 2D and 3D embedding diagrams. In order to analyze the complexity of the system, we have plotted the complexity factor for each wormhole. [ABSTRACT FROM AUTHOR]

The primary goal of this paper is to examine spacetimes admitting semiconformal curvature tensor in f (ℛ) modify gravity. The semiconformal flatness of general spacetime and spacetime in f (ℛ) gravity with perfect fluid, has been analyzed. For this consideration, we generate the forms of isotropic pressure p and energy density σ. After that, a few energy conditions are taken into account. Finally, we study the divergence-free semiconformal curvature tensor in f (ℛ) gravity in presence of perfect fluid. We emphasize that for recurrent or bi-recurrent energy–momentum tensor, Ricci tensor of this spacetime is semi-symmetric and consequently, the resulting spacetimes either accomplish inflation or possess fixed isotropic pressure and energy density. [ABSTRACT FROM AUTHOR]

In recent years, a class of compact objects called gravastars have drawn immense interest as regular solutions to end state stellar collapse. Since the energy density involved in collapse process is expected to be high, it is a natural choice to study such compact objects in context of modified gravity theories which reduce to General Relativity (GR) in the low energy regime. We have already framed a model of gravastar in such a modified gravity framework involving extra dimensional Randall–Sundrum (RS) single brane gravity [R. Sengupta, S. Ghosh, S. Ray, B. Mishra and S. K. Tripathy, Phys. Rev. D 102, 024037 (2020)]. As a sequel in this paper, we substantially improve our previous model by choosing the Kuchowicz function as one of the metric potentials, which leads to many new interesting results and physical features from our analysis as discussed in this paper. Also, we provide essential additional stability checks on our gravastar model to investigate the possibility of any instability creeping in due to the higher-dimensional framework. Our present improved gravastar model is found to clear all the stability checks successfully. Very interestingly, the static spherically symmetric matter distributions are found to accommodate both classes of solutions obeying and violating the modified energy conditions on the RS brane as we find in this work. We can conclude from our analysis that the Kuchowicz metric potential is very effective for describing regular solutions to compact objects at substantially high energies on the three-brane. [ABSTRACT FROM AUTHOR]

In this paper, we have provided a discussion regarding the structural properties of a spherical compact stellar object within the background of f (R , G) modified gravity. We have considered that the interior region of the compact stellar body is filled by a composition of anisotropic dark energy and isotropic normal matter which are assumed to be non-interacting. To relate the two stated fluids, we have considered the dark energy density directly proportional to the matter density. In particular, Krori–Barua (K–B) matric potentials are used to explore the solutions of modified field equations corresponding to f (R , G) = R + β R 2 + G m . Next, we have delivered a detailed 3-dimensional graphical analysis to design physically well-behavior and stability of different parameters like energy density, individual pressure components for both dark energy and normal matter and anisotropy. Also, we have explored the stability and physical acceptability criterion by causality conditions, adiabatic index, TOV equation, and Harrison–Zeldovich–Novikov criteria. Consequently, we have discussed the violation of energy conditions for dark energy and hold the same for the normal matter. Here is an important note we have taken for three compact objects like, SAX JI808.4-3658, PSR J1614-2230, and 4U1820-30, for graphical analysis. Furthermore, we have calculated the predicted values of central density, central pressure, and surface pressure for both dark and normal matter. Finally, we concluded that our proposed dark energy stellar configuration maintains all required stability and physical acceptability criteria. [ABSTRACT FROM AUTHOR]

In this paper, we analyze energy density inhomogeneities for charged fluid configuration in the background of f (T) theory and recognize its prime features as computed in GR. The dynamical equations are composed employing Bianchi identities for the standard, f (T) extra terms, and energy-momentum tensor for the electromagnetic field. We evaluate various mathematical models of dissipative and anisotropic fluid distributions in-plane symmetry under f (T) gravity. To proceed with the investigation, we design the f (T) field equations, kinematical quantities, and mass function. We analyzed dynamical variables and Ellis equations in terms of our considered theory. To examine the associated inhomogeneity factors, specific scenarios are illustrated alongside and without dissipation. Within a non-radiating situation, we analyze dust and isotropic and anisotropic matter in the state of electric charge. We examine the inhomogeneity factor of a dissipative fluid via a charged dust haze. We derive that the electromagnetic field fosters matter inhomogeneity, but additional curvature factors make the entire structure more homogenous as time passes. [ABSTRACT FROM AUTHOR]

In this paper, we use the cosmographic approach to discuss Friedmann space-time in the presence of torsion. For this, we explore equations of motion that explain creation in an isotropic and homogeneous cosmic backdrop with nonzero torsion. Here, we consider the energy density of holographic dark energy model ρd = 3c2(z)M p2L−2 where c2 is a dimensionless parameter depending on redshift parameter z,Mp = 1 κ is the reduced Planck mass and L represents the holographic length scale. We examine this dark energy model with both constant and variable holographic length scales in terms of Hubble parameter to determine the best-fit scale. The interaction between dark sector components is taken to evaluate cosmographic parameters, like Hubble, equation of state, deceleration, jerk, snap, lerk and statefinder parameters. We consider four c(z) parametrizations, which are Chevallier–Polarski–Linder, Jassal–Bagla–Padmanabhan, Wetterich and Ma–Zhang for both cases. We obtain consistent results for specific choices of constant parameters in the underlying scenario. [ABSTRACT FROM AUTHOR]

This paper is devoted to investigating the behavior of charged compact stars in the f(R,ϕ,X) theory of gravity, where R denotes the Ricci Scalar, ϕ is a scalar potential, and X is a kinetic term. For this purpose, we consider spherically symmetric spacetime with Bardeen geometry as exterior spacetime to investigate various properties of compact stars, including energy density and pressure components. Matching conditions are used to find model parameters. We present a detailed analysis, including a discussion of equations of state parameters, and stability criteria. In this analysis, we discuss the energy conditions to check the viability of our model. Furthermore, an equilibrium condition can be visualized through the modified Tolman–Oppenheimer–Volkov equation. It is concluded that Bardeen’s geometry supports the existence of compact stars in the background of the f(R,ϕ,X) theory of gravity. [ABSTRACT FROM AUTHOR]

In this paper, we present a novel curvature tensor called the 풦-curvature tensor, which is formed by combining the Weyl tensor and the 풲2-curvature tensor. It is proved that a semi-Riemannian manifold with traceless 풦-curvature tensor is Einstein, while a 풦-curvature flat semi-Riemannian manifold exhibits constant sectional curvature. We show that a space-time with traceless 풦-curvature tensor or 풦-curvature flat represents dark energy era. A semi-Riemannian manifold with divergence-free 풦-curvature tensor is Weyl harmonic. In a space-time where the 풦-curvature tensor is of divergence-free, both the isotropic pressure and energy density are constants. Under certain conditions, it is shown that a pseudo-풦-symmetric semi-Riemannian manifold reduces to a pseudo-Riemannian manifold. It is demonstrated that pseudo-풦-symmetric space-times can be regarded as generalized Robertson–Walker (GRW) space-times. Finally, a concrete example of pseudo-풦-symmetric semi-Riemannian manifolds is presented. [ABSTRACT FROM AUTHOR]

The primary objective of this paper is to examine singularity-free solutions within the framework of anisotropic solutions for the Chaplygin equation of state in f (R , ϕ , X) modified gravity theory. Herein, R signifies the Ricci scalar, ϕ denotes the scalar field, and X represents the kinetic term associated with ϕ. The investigation employs the Krori–Barua metric to explore the characteristics of an anisotropic compact star. In the course of our analysis, we specifically consider observational data about three distinct stellar structures: Her X-I, LMC X-4, and 4U 1538-52. Our inquiry extends to the graphical examination of various physical parameters, encompassing energy density, pressure components, anisotropic components, equation of state parameters, equilibrium conditions, stability analysis, adiabatic index, and energy conditions. Furthermore, we delve into the intricacies of the mass-radius function, compactness factor, and surface redshift–integral features of charged compact stars. The culmination of our findings suggests that the f (R , ϕ , X) theory of gravity when subjected to observational scrutiny, manifests as realistic, stable, and devoid of singularities. [ABSTRACT FROM AUTHOR]

In this paper, 3D–2D-dimensional reduction for hyperelastic thin films modeled through energies with point-dependent growth, assuming that the sample is clamped on the lateral boundary, is performed in the framework of Γ -convergence. Integral representation results, with a more regular Lagrangian related to the original energy density, are provided for the lower dimensional limiting energy, in different contexts. [ABSTRACT FROM AUTHOR]

One of the most important issues in cosmology is the study of a series of hypothetical objects called wormholes. Recently, researchers have studied these hypothetical objects under different conditions. In this paper, we aim to evaluate the traversable wormhole according to a modified f (R) gravitational model, specifically − R 2 + a R 2 (1 − n) , from the perspective of two essential functions in wormhole structure: shape and redshift function. These hypothetical objects can solve Einstein's equations by tolerating the violation of null energy conditions (NEC). With respect to these concepts, we examine various energy conditions such as the NEC, weak energy condition (WEC), dominant energy condition (DEC) and strong energy condition (SEC) using radial pressure, tangential pressure and energy density obtained from the wormhole equations. Finally, we evaluate different energy conditions by plotting some figures and checking for satisfaction or violation. We will analyze the results and present the conclusions in tables. [ABSTRACT FROM AUTHOR]

In this paper, we have investigated an anisotropic cosmological model in f (Q) gravity with string fluid in LRS Bianchi type-I universe. We have considered the arbitrary function f (Q) = Q + α Q + 2 Λ , where α is model free parameter and Λ is the cosmological constant. We have established a relationship between matter energy density parameter Ω m and dark energy density parameter Ω Λ through Hubble function using constant equation of state parameter ω. We have made observational constraint on the model using χ 2 -test with observed Hubble datasets H (z) and SNe Ia datasets, and obtained the best fit values of cosmological parameters. We have used these best fit values in the result and discussion. We have discussed our result with cosmographic coefficients and found a transit phase dark energy model. Also, we analyzed the Om diagnostic function for anisotropic universe and found that our model is quintessence dark energy model. [ABSTRACT FROM AUTHOR]

In this paper, we calculate a new class of wormhole solutions in the framework of teleparallel gravity. To obtain a characteristic wormhole solution, we use anisotropic matter distribution and a specific form of two dark matter profiles (URC profile and Quantum wave dark matter). As a general strategy, we create a relationship between calculated energy density and dark matter profiles for the system and investigate the physical properties of the wormhole geometry. A detailed analytical and graphical explanation of the matter contents via energy conditions is provided. The calculated shape functions of wormhole geometry meet the required conditions in both circumstances. Several intriguing features have emerged from the investigation, as have the properties of the exotic matter within the wormhole geometry. Finally, we have concluding remarks. [ABSTRACT FROM AUTHOR]

In this paper, we investigated the general behaviors of the Tsallic holographic dark energy (THDE) model in general relativity. Here, we take the Bianchi V I 0 metric, which is homogeneous and anisotropic. We investigate the THDE models with the Hubble horizon and Granda–Oliveros (GO) cutoffs. We have studied the behavior of a few quantities, such as dark energy density (ρ D ,) , matter-energy density (ρ m) , and skewness parameter (γ) and discuss their physical significances. In our THDE models, the EoS parameter explains the universe's evolution based on the value of the non-extensive or Tsallis parameter δ. In addition, we develop the cosmographic parameters like, deceleration parameter (q) , jerk parameter (j) , lerk parameter (l) , snap parameter (S) and maxout parameter (m). We have explored the ω D − ω D ′ plane and the stability analysis of the THDE model by a perturbation method. We have also constructed a correspondence between the THDE model with quintessence. Some physical and geometrical behaviors of the models are also discussed. [ABSTRACT FROM AUTHOR]

In this paper, the energy density of plane gravitational wave is studied by using Einstein and Møller's prescription of energy–momentum pseudotensors. The linearly polarized plane gravitational wave solution of Einstein field equation, which has been defined by Bondi et al., is represented by four kinds of different coordinates. The energy distributions of gravitational wave solution in Einstein and Møller's prescription are obtained. Particularly, the energy component is zero in null coordinates. [ABSTRACT FROM AUTHOR]

This paper is devoted to an analysis of the crack deflection angle in a semi-circular disc made of a fine-grained composite based on water glass-activated slag. Three-point bending together with an inclined crack ensures the crack propagation in I + II mixed mode. Generally, concrete material exhibits quasi-brittle fracture behavior, which is difficult to understand. Multi-parameter fracture mechanics (MPFMs) concept shall help us to describe the crack propagation and the influence of choice of a suitable distance for application of generalized fracture criteria is investigated. In this work, the well-known maximum tangential stress (MTS) criterion as well as strain energy density (SED) criterion are applied in their multi-parameter (MP) form to find the initial kink angle. Williams power expansion is used to approximate the crack-tip stress field. Its coefficients need to be calculated numerically via combination of the finite-element (FE) solution and over-deterministic method. Results are discussed and recommendations are stated regarding the critical length parameter as well as the number of the Williams expansion (WE) coefficients. [ABSTRACT FROM AUTHOR]

In this paper, we investigate how the electromagnetic field influences the idea of complexity within the framework of squared gravity. The physical traits, including heat dissipation, charge, anisotropic pressure, energy density variations and correction components are found to be significant contributors of complexity in celestial objects. By employing Herrera's orthogonal splitting approach, scalar functions are obtained yielding a complexity factor that incorporates the crucial attributes of the self-gravitating system. Furthermore, we examine the dynamics of charged spherical configuration by considering homologous mode as the simplest evolutionary pattern. Our investigation includes complexity-free scenarios (dissipative/non-dissipative) with homologous constraints. Moreover, we explore the components that contribute toward complexity during the evolutionary process. We conclude that self-gravitating structures get more complex with the inclusion of extra curvature terms of squared gravity and charge. [ABSTRACT FROM AUTHOR]

In this paper, we explore the existence of wormholes in the context of f (R , T) gravity. The f (R , T) theory is a curvature-matter coupled modified gravity that depends on an arbitrary function of the Ricci scalar R and the trace of the stress-energy tensor T. In this work, we adopt two different choices for the matter Lagrangian density ( ℒ m = and ℒ m = p r ) and investigate the impact of each one on wormhole structure. By adequately specifying the redshift function and the shape function, we found a variety of exact wormhole solutions in the theory. Our finding indicates that for both classes of wormholes, the energy density is always positive throughout the spacetime, while the radial pressure is negative. This means exotic matter is necessary for the existence of wormholes in f (R , T) gravity. [ABSTRACT FROM AUTHOR]

Alcubierre's warp-drive was the first to introduce superluminal travel from different approaches. Instead of creating a shortcut through spacetime via a wormhole, geometrodynamics of simultaneously contracting and expanding spacetime were conjectured. However, both methods require exotic matter that violates energy conditions. In this paper, we employ the concept of braneworld that naturally influences spacetime geometrodynamics. Starting from defining and developing the spacetime metric of the braneworld warp bubble, the expression for energy densities as a function of relevant parameters which contributes to the braneworld approach of superluminal travel by hyperspace-drive was derived. [ABSTRACT FROM AUTHOR]

In this paper, we study an isotropic flat FLRW-model in scale-covariant theory of gravity f γ δ (ϕ) 1 which is explained in terms of ordinary and covariant differentiation of scalar field ϕ. As we know, the deceleration parameter (DP) is time-dependent, so we consider the DP q as the function of t. Using this methodology, we find all the important cosmological factors in terms of a hyperbolic function of the cosmic time t. In turn, we create the model having the behavior of the late-time universe, which is ever accelerated expanding and faces a Big Freeze at the end. The model shows the quintessence dark energy model from early to late times. We compute the constrained values of Hubble parameter H 0 = 7 0. 9 7 9 − 0. 0 0 4 3 + 0. 0 2 1 and the model parameter n = 1. 2 4 0 7 9 − 0. 0 0 0 7 9 + 0. 0 0 0 1 5 using joint analysis of the OHD data of 77-points and Pantheon bin data. The model exhibits point-type singularity as it begins with a point of zero volume, infinite energy density and temperature. Furthermore, we obtain the present value of DP (q 0) ≈ − 0. 5 4. Also, we examine the ultimate behavior of our model by the proper analysis of energy conditions (ECs), cosmographical parameters and Statefinder diagnostic. Finally, the proposed model behaves like a quintessence dark energy model. [ABSTRACT FROM AUTHOR]

This paper is devoted to study FRW universe in the context of Chern–Simons corrected f (R) gravity. In particular, the work provides the investigation of cosmological dynamics within modified gravity by assuming a suitable Hubble parameter that might result in a realistic bouncing universe. For this purpose, we consider a suitable Hubble parameter and examine the bouncing cosmology by assuming a well-known f (R) gravity model. Further, we explore the behavior of energy density and pressure profiles by employing the chosen Hubble parameter. We obtain positive and increasing trends of energy density during the bouncing phase while the negative behavior of pressure in our work could potentially be associated with cosmic expansion. We have also studied the energy conditions and in our case NEC is not violated perhaps due to the reason that the equation of state parameter is not crossing the phantom divide. However, the SEC is violated justifying a successful bounce. Moreover, the validation of DEC and TEC suggests that the chosen model is well behaved in nature. The Hubble parameter passing through the bouncing point shows an increasing trend, indicating an expansion phase after the bounce. The equation of state parameter is negative after the bouncing spot, particularly around ω ≈ − 1. This behavior justifies the current cosmic expansion. The deceleration parameter exhibits a negative behavior implies that the cosmological model demonstrates cosmic expansion. Thus all the results validate the existence of a bouncing universe with the chosen model in Chern–Simons corrected f (R) gravity. [ABSTRACT FROM AUTHOR]

The aim of this paper is to examine the singularity-free solutions for anisotropic stellar structures in f (R , ϕ) theory of gravity, where R denotes the Ricci scalar and ϕ represents the scalar field. For this purpose, we consider the spherically symmetric spacetime to discuss the stellar structures with anisotropic fluid. Moreover, the Einstein field equations are solved by using Chaplygin equation of state, and the Karori–Barua metric. To analyze the charged stellar structure, we use the matching conditions of spherically symmetric spacetime with the Reissner–Nordstrom exterior metric and develop some expressions for finding the unknown parameters. We further investigate the graphical behavior of energy density, pressure components, anisotropic component, equation of state parameters, equilibrium condition, stability analysis, adiabatic index and energy conditions. Conclusively, our considered stellar structures under observations are realistic, stable, and are free from any singularities. [ABSTRACT FROM AUTHOR]

The construction of compact star models with quintessence and cloud of strings anisotropic fluid lays the foundation for the research presented in this paper, which focuses on the ansatz of f(Q) gravity. We utilized a spherically symmetric spacetime to derive the field equations incorporating quintessence and cloud of strings anisotropic matter fields. The well-known Karmarkar condition was employed to obtain the gravitational components of the spherically symmetric spacetime. The constant parameters used in the study were obtained by applying junction conditions on the interior and exterior spacetimes. We used the mass and radius of P S R J 1 6 1 4 − 2 2 3 0 & S M C X − 1 , which are already present in the literature. Afterward, we calculated the important properties of quintessence stars in the presence of cloud of strings to ensure the stability and physical presence of compact models. To achieve this goal, we studied features such as energy density, quintessence density, pressure profiles, gradients, anisotropic factor, energy conditions, sound speeds, TOV forces, EoS components, mass function, compactification and redshift. [ABSTRACT FROM AUTHOR]

This paper explores the dynamic behavior of the universe within the framework of the f (R , G) theory of gravity. Here, R and G represent the Ricci scalar and Gauss–Bonnet invariant, respectively. By solving the modified field equations with the chosen f (R , G) function, specifically f (R , G) = R + m R 2 + n G 2 , we determine the best fit values of model parameters that are consistent with recent observational datasets. These datasets include 57 data points from the Cosmic Chronometers, Pantheon, and BAO datasets. Furthermore, we analyze the physical properties of cosmographic parameters, such as energy density and pressure, corresponding to the constrained values of the model parameters. The evolution of the deceleration parameter in our study indicates a transition from a decelerated phase to an accelerated phase in the universe. Remarkably, our f (R , G) cosmological model effectively describes the late-time cosmic acceleration without requiring the introduction of a dark energy component in the field equations. [ABSTRACT FROM AUTHOR]

In this paper, we inspect the stable geometry of thin-shell wormholes in the background of static spherically-symmetric AdS black holes solution bounded by dark fluid and Chaplygin-like equation of state p = − ℬ / ρ , where p and ρ denote the pressure and energy density that are related through positive constant ℬ. For this purpose, we consider the two equivalent copies of black holes and connected them at the hypersurface through cut and paste approach. Then, we employ the linearized radial perturbation to discuss the stability of the developed wormhole geometry by assuming variable equations of state. We obtain the maximum stable configuration for massive black holes for both barotropic and Chaplygin variable equations of state while for higher values of n , stable regions decrease. It is found that for every selection of physical parameters of black hole geometry with low intensity of Chaplygin dark fluid, we get the stable configuration of thin-shell wormholes. [ABSTRACT FROM AUTHOR]

In this paper, we show Liouville-type theorems for exponentially harmonic maps and p-harmonic maps between Kähler manifolds. We then study the quadratic form of an exponentially harmonic map of Kähler manifolds and its applications. We also prove that if f : M → N is an exponentially harmonic map from a compact Kähler manifold M into a Kähler manifold N with constant energy density such that the curvature of N is strongly semi-negative, then f is holomorphic or antiholomorphic. [ABSTRACT FROM AUTHOR]

This paper explores collapsing solutions of the field equations in the context of 4D Einstein–Gauss–Bonnet (EGB) gravity. We study the effects of GB-term on the energy density, pressure (tangential and radial) and anisotropy of the collapsing system. We consider expansion scalar (Θ < 0) to obtain the collapsing solution. Furthermore, we discuss the graphical behavior of the source variables. [ABSTRACT FROM AUTHOR]

In this paper, we study a flat homogeneous FLRW model in Lyra geometry which is described by a time-dependent displacement vector. We consider an appropriate parametrization of the energy density of scalar field ρ ϕ in terms of the cosmic scale factor. The result shows two transitions from deceleration to acceleration. Furthermore, we constrain the model parameter α and the displacement field vector β using the recent supernovae data, Hubble dataset of 77 points and their joint data which predict the accelerated expanding phase of the universe in late times. The effective equation of state parameter ω eff speculates Λ CDM in late times. Finally, we use the statefinder diagnostic to differentiate our model from the various dark energy models. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the thermodynamics of a dark energy bulk viscosity model as a cosmic fluid. In this regard, the two theories of Eckart and Israel–Stewart (IS) are the bases of our work. Therefore, we first investigate the thermodynamics of cosmic fluids in the dark energy bulk viscosity model and the general relationships. Then, we express the thermodynamic relationships of Eckart's theory. Due to the basic equations of Eckart's theory and Friedmann's equations, we consider two states, one is p = − ρ (standard) and the other is p ≠ − ρ (non-standard). In the standard state, we define the pressure (p) , energy density (ρ) and bulk viscosity coefficient (ξ) of the cosmic fluid in terms of cosmic time and we obtain its relations. We also mention that in this standard state, because of p = − ρ , the value of a (t) is zero, so a (t) is not defined in this state. But in the non-standard case (p ≠ − ρ) , the bulk viscosity coefficient (ξ) is zero and only the scale factor, pressure and energy density of the cosmic fluid are defined. We also consider two states of constant and variable bulk viscosity coefficients and obtain three Hubble constant parameters and scale factor in terms of cosmic time, and energy density in terms of scale factor. In the state of variable bulk viscosity coefficient, we consider the viscosity coefficient as the power law from energy density (ξ = α ρ s) , which is α > 0 and a constant. Following this, we discuss about the dissipative effects of cosmic fluids and examine the effects of energy density for dark energy in the IS theory. The results are comprehensively presented in Tables 1 and 2. Also, according to observational constraints, the results of the likelihood analysis for the IS viscous model are summarized in Table 3. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to examine the anisotropic matter distribution concerning one of the well-known f (R , T) theories of gravity, where R and T represent the Ricci scalar and trace of the energy–momentum tensor, respectively. We consider anisotropic matter distribution in spherically symmetric spacetime for our desired work. We investigate the physical behavior of pressure components, energy density, anisotropic function, equation of state parameters, and energy conditions. Furthermore, we analyze the stability of compact stars by investigating the causality condition, adiabatic index, and generalized Tolman–Oppenheimer–Volkoff equation. Some fundamental features of compact stars have been investigated, like compactness factor, mass function, and surface redshift. Our calculated solutions for Bardeen stellar structures are consistent and stable in the background of the f (R , T) theory of gravity. [ABSTRACT FROM AUTHOR]

In this paper, the Morris–Thorne wormholes are studied in the background of f (R , T) = R + α R 2 + β ln T gravity, where α and β are constants. The wormhole solutions are derived in two cases with different assumptions for the matter forms. In each case, the null energy condition (NEC) is analyzed and the range of parameters satisfying the NEC are determined. Further, the stability of solutions is examined with the help of the generalized Tolman–Oppenheimer–Volkoff (TOV) equation. [ABSTRACT FROM AUTHOR]

In this paper, we analyzed charged particle transverse momentum spectra in high multiplicity events in proton–proton and nucleus–nucleus collisions at LHC energies from the ALICE experiment using the color string percolation model (CSPM). The color reduction factor and associated string density parameters are extracted for various multiplicity classes in p p collisions and centrality classes for heavy-ion collisions at various LHC energies to study the effect of collision geometry and collision energy. These parameters are used to extract the thermodynamical quantities temperature and the energy density of the hot nuclear matter. A universal scaling is observed in initial temperature when studied as a function of charged particle multiplicity scaled by transverse overlap area. From the measured initial energy density and the initial temperature T, a dimensionless quantity / T 4 is constructed which is used to obtain the degrees of freedom (DOF) of the deconfined phase. A two-step behavior and a sudden increase in DOF of ∼ 47 for the ideal gas, above the hadronization temperature (T ≈ 210 MeV), are observed in case of heavy-ion collisions at LHC energies. [ABSTRACT FROM AUTHOR]

The treatment of (1+3)-covariant perturbation in a multifluid cosmology with the consideration of f (G) gravity, G being the Gauss–Bonnet term, is done in this paper. We define a set of covariant and gauge-invariant variables to describe density, velocity and entropy perturbations for both the total matter and component fluids. We then use different techniques such as scalar decomposition, harmonic decomposition, quasi-static approximation together with the redshift transformation to get simplified perturbation equations for analysis. We then discuss a number of interesting applications like the case where the universe is filled with a mixture of radiation and Gauss–Bonnet fluids as well as dust with Gauss–Bonnet fluids for both short- and long-wavelength limits. Considering polynomial f (G) model, we get numerical solutions of energy density perturbations and show that they decay with increase in redshift. This feature shows that under f (G) gravity, specifically under the considered f (G) model, one expects that the formation of the structure in the late Universe is enhanced. [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]

There are a number of different theories which tend to explain the concept of universe's accelerated expansion. Among these theories, modified gravity is the most promising one. This paper elaborates matter distribution along with different characteristics of anisotropic compact stars in f (R , G) gravity background. Specifically, to profoundly understand physical behavior of the compact stars, we considered six compact stars, namely: Her X-1 ( CS 1 ), SAXJ1808.4-3658 ( CS 2 ), 4U1820-30 ( CS 3 ), PSR J 1614 2230 ( CS 4 ), VELA X-1 ( CS 5 ) and Cen X-3 ( CS 6 ) and calculated the corresponding quantities such as energy density (ρ), radial pressure ( p r ) and tangential pressure ( p t ) using three distinct models of f (R , G) gravity. For simplicity, f (R , G) gravity is divided into two parts as: f (R , G) = f 1 (R) + f 2 (G). The first part f 1 (R) is considered Hu–Sawicki like model, while the second part f 2 (G) is considered logarithmic like for Model 1 and power law like for Model 2 and Model 3. Predominantly, measurements of anisotropy, the energy conditions (ECs) and stability aspects of models for considered compacts stars are presented using graphical techniques. Furthermore, we also established that for the f (G) model parameter (n > 0), all the six stars show conventional behavior. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the most general exact solutions of Brans–Dicke cosmology by choosing the scale factor "a" as the new independent variable. It is shown that a set of three field equations can be reduced to a constraint equation and a first-order linear differential equation. Thus this new set of equations is solvable when one supplies one of the following pairs of functions: (ϕ (a) , ρ (a)), (ϕ (a) , V (a)) or (ϕ (a) , H (a)). A universe with a single component energy-matter density, the early universe with constant energy density and radiation and the present universe with constant energy density and matter are studied. It is seen that in all cases initial values of the universe cause ϕ 2 potential and a constant term in the Hubble function which causes an exponential expansion of the universe. The relation between cosmological constant and initial values of the universe is found. [ABSTRACT FROM AUTHOR]

The holographic Ricci dark energy (HRDE) can be treated as a running vacuum due to its analogy in the energy density, which is a combination of H and Ḣ , the model can predict either eternal acceleration or eternal deceleration. In the earlier works, we have shown that the presence of additive constant in the energy density or by considering possible interaction between dark sectors through a phenomenological term, the model can predict a transition from a prior decelerated to a late accelerated epoch. This paper analyzes the cosmic evolution of HRDE as running vacuum with a nonlinear interaction (NLI) between dark sectors in a flat Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. We consider three possible NLI forms which give analytically feasible solutions. We have constrained the model using the Type1a Supernova(Pantheon) + CMB(Planck 2018) + BAO(SDSS) data and evaluated the best estimated values of all the model parameters. We have analyzed the evolution of the Hubble parameter and deceleration parameter of all three cases. We perform state finder analysis of the model, which implies the quintessence nature of the model and found that it is distinguishably different from the standard Λ CDM model. The dynamical system analysis of all three cases confirms the evolution of the universe from an unstable prior matter-dominated era to a stable end de Sitter phase. [ABSTRACT FROM AUTHOR]

In this paper, the effective potential approach in quantum field theory is used in order to investigate self-interaction loop correction to the Casimir energy density and generation of topological mass for both massless and massive real scalar fields. It is assumed that the scalar field obeys a helix boundary condition. In addition, it is also considered a CPT-even aether-type violation of the Lorentz symmetry. In the absence of the Lorentz violation, we obtain analytical expressions for the loop correction to the Casimir energy density and to the mass of the scalar field. The same expressions are also obtained assuming the Lorentz violation in each of the spacetime directions. We also show some graphs that exhibit how the loop correction and the Lorentz violation affect the Casimir energy density and the mass of the scalar field. [ABSTRACT FROM AUTHOR]

In this paper, we explore the wormhole solutions (which are initially proposed by R. Garattini [Eur. Phys. J. C 79 (2019) 951] who take generalized uncertainty principle (GUP) with Casimir energy) in the framework of two well-known dark energy (DE) models, generalized Chaplygin gas (GCG) and polytropic gas. We consider the GUP corrected pressure (force per unit surface area) in the equation of state (EoS) of these DE models to construct the GCG corrected energy density and polytropic gas corrected energy density. Three models of redshift function are taken into account to construct shape function as well as wormhole geometry for both cases of corrected energy densities. We find the behavior of EoS parameters, redshift function for isotropic and anisotropic fluid, equilibrium conditions, null energy condition and exotic volume at the throat of the wormhole with radius r 0 . [ABSTRACT FROM AUTHOR]