Physics of the Dark Universe最新文献

This research deals with the impacts of non-conserved gravitational theory on the physical behavior of three anisotropic compact stars. For this purpose, the metric of static spherically symmetric comprising the anisotropic matter composition is taken into account. To examine the various aspects of some particular compact star models, the Durgapal–Lake metric functions are considered. The unknown parameters involved in Durgapal–Lake metric functions are computed via matching constraints with observed data of masses and radii of three particular stellar objects. The obtained results are noted to be as accurate as possible in terms of physical viability. All the physical crucial parameters and characteristics are displayed graphically and these visuals depict the evaluated solutions that are consistent for three distinct stellar models. It is observed that the parameters occurring in the set of solutions have some valuable insights for these solutions. It is determined that the stars under consideration manifest stable structures corresponding to Durgapal–Lake metric potentials in this framework while they exhibit instability in the case of conservative theory, i.e., general relativity. Further, it is exhibited that for the theory factor equals to zero, the results of general relativity can also be observed graphically.

We explore the effect of the plasma (uniform and non-uniform) on the deflection angle of relativistic neutral particles and the light of the charged black hole surrounded by fluid dark matter. It also shows how the plasma modifies the deflection angle aspects for a charged black hole within fluid dark matter. The thermodynamic features of a charged black hole in the background of perfect fluid dark matter are discussed. The temperature, mass, entropy, Gibbs free energy, and heat capacity are also analyzed under the effect of the fluid dark matter parameter. Further, we discuss some different aspects of heat capacity to check the transition from a stable phase to an unstable one for the considered black hole. It is found that all the required properties related to thermodynamics are well satisfied for the different values of charge and perfect fluid parameters.

In this work, we explore the thermodynamic topology of phantom AdS black holes in the context of massive gravity. To this end, we evaluate these black holes in two distinct ensembles: the canonical and grand canonical ensembles (GCE). We begin by examining the topological charge linked to the critical point and confirming the existence of a conventional critical point $\left(C{P}_1\right)$ in the canonical ensemble (CE), this critical point has a topological charge of $-1$ and acts as a point of phase annihilation, this situation can only be considered within the context of the classical Einstein–Maxwell (CEM) theory $(\eta =1)$, while no critical point is identified in the GCE. Furthermore, we consider black holes as a topological defect within the thermodynamic space. To gain an understanding of the local and global topological configuration of this defect, we will analyze its winding numbers, and observe that the total topological charge in the CE consistently remains at 1. When the system experiences a pressure below the critical threshold, it gives rise to the occurrence of annihilation and generation points. The value of electric potential determines whether the total topological charge in the GCE is zero or one. As a result, we detect a point of generation point or absence of generation/annihilation point. Based on our analysis, it can be inferred that ensembles significantly impact the topological class of phantom AdS black holes in massive gravity.

This work investigates the shadow and quasinormal modes of a novel rotating Born–Infeld-type black hole. First, we study the effect of interaction between nonlinear electrodynamic fields and photons on shadow radius and show that it is less than the error of shadow measurements in Event Horizon Telescope (EHT) observations. Then, we obtain a rotating metric using the Newman–Janis algorithm, starting with the initial metric of the nonrotating novel Born–Infeld black hole solution. Next, we analyze the null geodesics to determine the celestial coordinates. The black hole’s shadow radius is determined by using celestial coordinates. The mass, spin, charge, and nonlinearity parameters all influence the shape and size of the black hole shadow. An increase in the spin parameter results in a gradual reduction in the size of black hole shadows and further distortion of the shadows. Furthermore, constraints on the spin and electric charge of black holes, as well as the nonlinearity parameter, are derived through the utilization of the shadow sizes of supermassive black holes Sagittarius (Sgr) A* and M87* obtained from observations of the EHT. Also, we investigate the correlation between the standard shadow radius and the equatorial and polar quasinormal modes for revolving black holes. Finally, we analyze the emission energy rate from the black hole based on different spacetime parameters. Our observation indicates that the emission energy rate decreases as the values of spin and nonlinearity parameters increase, keeping the charge-to-mass ratios of the Born–Infeld black hole constant.

We explore the implications of Rainbow Gravity on the properties of quark stars (QSs), hypothesized compact stars composed of strange quark matter. Utilizing the theories of Rainbow Gravity, this study integrates these frameworks to analyze QSs, particularly focusing on their structural and stability characteristics under extreme conditions. By employing the modified gravitational field equations and energy-dependent spacetime metrics, we investigate how these alterations affect the theoretical predictions concerning QSs, potentially providing insights into quantum chromodynamics at high energy scales. Our results indicate that within the Rainbow Gravity framework, QSs can potentially exceed the typical 2$M_{\odot }$ mass limit, suggesting a stiffer equation of state and larger radii compared to predictions by General Relativity. These findings highlight significant modifications in the structure and stability characteristics of QSs, offering new perspectives on the interplay between gravity and quantum field theory.

In this paper, we study the Tsallis holographic dark energy model to examine the cosmic evolution in the framework of energy–momentum squared gravity. For this purpose, we use three distinct horizons as infrared cut-offs such as the particle horizon, event horizon and the conformal age of the universe. We analyze the behavior of different parameters like Hubble, density, equation of state and deceleration corresponding to different infrared cut-offs and explore the mysterious universe. The stability analysis is also performed using the squared sound speed method for all horizons. Our findings indicate that the considered dark energy model supports the accelerated expansion of the universe in all cut-offs. The stability is achieved for the particle horizon, while partial stability is observed for event horizon and conformal age of the universe. We also assess the behavior of standard diagnostic tools such as the ${\omega }_{TDE}-{\omega }_{TDE}^{{}^{\prime }}$ analysis and statefinder pair $(r,s)$ to discuss different cosmic eras. This delves into the intricate interplay between dark energy model and modified gravitational theory, shedding light on the overarching dynamics of the cosmos.

The focus of this work is to examine the dynamical behavior of thin-shell wormholes developed from the polymer black hole in loop quantum gravity. Such geometrical structure is formulated by considering the cut and paste approach to avoid the appearance of singularity as well as the position of the horizon. Then, we are interested in exploring the impact of different types of matter contents on the stable configurations of the shell using linearized radial perturbation. It is observed that the quantum term ${\Theta }_k$ possesses a marvelous role in obtaining the stability of the shell. For the choice of variable phantomlike model, we find the stability for some specific values of $n$ by applying the constraints $0<{\Theta }_k<M^2$. In the literature, many researchers find stability for some specific ranges of $n$. In the presence of ${\Theta }_k$, the thin-shell wormhole becomes stable for the variable Chaplygin gas model for all choices of $n$ as compared to phantomlike and barotropic equations of state. As ${\Theta }_k$ approaches to $M^2$, we get the maximum stable behavior for all positive values of the variable $n$ for the choice of variable Chaplygin gas model.

We investigate a black hole solution analogous to Hayward regular black holes with a negative cosmological constant surrounded by quintessence — the Hayward–Kiselev anti-de Sitter (AdS) black hole, derived from Einstein equations coupled with nonlinear electrodynamics. The solution reveals a singularity due to the quintessential dark energy, and we have outlined the conditions necessary for regularity. When pressure, e.g., $P=0.016$, the effect of quintessential dark energy results in an otherwise absent van der Waal phase transition and second-order phase transition. Interestingly, the impact of dark energy decreases critical temperature ($T_c$), whereas critical pressure ($P_c$) increases. Investigating the correlation between photon sphere radius and the first-order phase transition exhibited non-monotonic behaviour among the photon sphere radius, nonlinear charge parameter, temperature, and pressure under certain conditions. Variations in the photon sphere radius and impact parameter before and after the phase transition serve as order parameters. The critical exponents $\Delta r_{ps}$ and $\Delta u_{ps}$ near the critical point consistently approach 1/2, suggesting that $r_{ps}$ and $u_{ps}$ can be order parameters for black hole phase transitions and indicating a potential universal gravitational relationship near the critical point within a black hole thermodynamic system. We also analysed the previously unexplored Kiselev-AdS black hole, which emerges as a particular case in the limit $g\to 0$.