Journal of High Energy Astrophysics最新文献

We investigate the dynamics of neutral test particles revolving around a non-rotating black hole immersed in dark matter DM. We derive exact solutions for the radial profiles of specific angular momentum and energy for equatorial stable circular orbits as a function of the parameters of the black hole. Using the effective potential approach, we explore the stability of these circular orbits and the effective force acting on particles in the presence of dark matter. Additionally, we examine the impact of dark matter on the innermost stable circular orbits. By numerically integrating the equations of motion, we plot the trajectories of particles around the black hole and analyze how dark matter affects these trajectories. We also calculate the analytical frequencies of radial and latitudinal harmonic oscillations as functions of the dark matter parameter for both local and distant observers. We compare these results with scenarios where dark matter is absent. Furthermore, we study the effects of dark matter on periastron precession. We present an analysis of the constraints on the dark matter and black hole mass parameters using Markov Chain Monte Carlo (MCMC) methods. Our study focuses on QPOs observed in X-ray binaries, in particular, the microquasars GRO J1655-40 and XTE J1550-564, and the centers of the galaxies M82 X-1 and Sgr A^⁎. We also analyze the particle collisions, discussing the center-of-mass energy of the colliding particles. Our observations reveal that the motion of particles revolving around the black hole is significantly affected by varying the model parameters.

Motivated by the recently exploited concept of Kaniadakis entropy, we construct a five-dimensional spherically symmetric static black hole (BH) solution surrounded by dark fluid with a Chaplygin-like equation of state $p=-\gamma /\rho$ (CDF) in anti-de Sitter space (AdS). Conventionally speaking, Boltzmann entropy-based thermodynamics of charged AdS black holes (BHs) have been shown to display physically interesting features, viz., P–v criticalities and van der Waals-type BHs. This work highlights the extended version of the standard Boltzmann entropy, i.e., Kaniadakis entropy, which is a non-extensive generalization of classical statistical mechanics. Borrowing ideas from the condensed matter physics realm, we assess the impact of Kaniadakis entropy on the P–v critical study, Gibbs free energy, and critical exponents of five-dimensional AdS BHs with CDF background in the extended phase space. A particular interest is concerned with the exploitation of geothermodynamics tools, especially Hendi, Panahiyan, Eslam Panah, and Momennia (HPEM) geometry. This offers the possibility of predicting physical limitations and physical transition points. Our analysis breaks new ground in the understanding of BH thermodynamics in a relativistic statistical framework, emphasizing the role of non-extensive corrections in the dual AdS BH/Van der Waals fluid pattern.

This paper investigates the complex interplay between charged anti-de Sitter black hole thermodynamic behavior and nonlinear electrodynamics. Strong insights are obtained by examining the impact of nonlinear electrodynamics on the Joule-Thomson expansion of charged black holes and assessing the thermal fluctuations with higher-order corrections in the context of Barrow entropy. The research shows the complex interactions influencing thermal properties from Joule-Thomson coefficients are affected by temperature, pressure, and changes in gas composition due to the effects of charges and nonlinear electrodynamics factors on inversion temperature and pressure. Furthermore, analyzing black hole isenthalpic curves provides important insights into the thermodynamic behavior of the system by highlighting discrete heating and cooling zones in the inversion curve. Significant effects of nonlinear dynamics on the thermodynamic parameters of the system are highlighted by the notable variations in the Helmholtz free energy, internal energy, enthalpy, and Gibbs free energy of charged anti-de Sitter black holes. By demonstrating the complex and captivating nature of these interactions, the paper concludes by emphasizing the significant influence of nonlinear dynamics on the thermodynamic parameters of charged black holes within the framework of Barrow entropy.

We introduce a new approach for detecting potential cosmological changes in the proton-to-electron mass ratio (µ) by studying the absorption lines of molecular hydrogen (H2) in the high-redshift quasar QSO 0347–383. By comparing these observations with high-precision laboratory data, we determine a variation of ∆µ/µ = (0.120 ± 0.144) × 10⁻⁸ at z_abs = 3.025. This highly precise result offers valuable insights into the constancy of fundamental physical constants over extended cosmic periods.

In this study, we have formulated the Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model of the universe, selecting the source to be Holographic and Renyi holographic dark energy. Holographic and Renyi holographic dark energy fluids have demonstrated their prevalence over Hubble's and Granda-Oliveros cutoffs in $f(Q,C)$ gravity, where Q is the non-metricity scalar and C represents the boundary term. We assume the scale factor's form, $a\left(t\right)=sin{h}^{\frac{1}{m}}\left(\alpha t\right)$ to illustrate the characteristics of the cosmological parameters. We determine the appropriate values of the parameters by employing the MCMC technique with both the Hubble dataset consisting of 46 data points and 15 BAO dataset. The increasing energy density, coupled with $q=-1$, indicates the Universe's acceleration period, while the EoS parameter $\omega =-1$ corresponds to the ΛCDM model. After investigating the energy conditions, we recognized that our model violates the strong energy constraint. We examine how the statefinder parameters behave in our model. We also investigate the Universe's age.

The Finsler-Randers space-time offers a novel perspective on cosmic dynamics, departing from the constraints of General Relativity. This paper thoroughly investigates two dark energy models resulting from the parametrization of H within this geometric framework. We have conducted some geometrical and physical analysis of the dark energy models in Finslerian geometry. First, we have derived the field equations governing the universe's evolution within the Finsler-Randers formalism, incorporating the presence of dark energy. Through this, we explore its implications on cosmological phenomena, including cosmic expansion, late-time behavior of the universe, cosmological phase transition, and a few more. Also, we employ observational data such as Cosmic Chronometer, Supernovae, Gamma-Ray Bursts, Quasar, and baryon acoustic oscillations to constrain the parameters associated with dark energy in the Finsler-Randers universe. Comparing theoretical predictions with empirical observations, we assess the model viability and discern any deviations from the standard ΛCDM cosmology. Our findings offer intriguing insights into the nature of dark energy within this alternative gravitational framework, providing a deeper understanding of its role in shaping cosmic evolution. The implications of our results extend to fundamental cosmology, hinting at new avenues for research to unravel the mysteries surrounding dark energy and the geometric structure of the universe within non-standard gravitational theories.

The modern sky surveys accelerates astronomical data collection. We proposed a multi-model fusion method aimed at comprehensive and fine-grained astronomical source classification. This method incorporates a redshift estimation model using the mixture density network into a source classification model. Based on 1.2 million sources from the SDSS and the ALLWISE, we performed three-class experiments for stars, quasars, and galaxies, four-class experiments to further classify galaxies into normal and emission-line galaxies (NGs; ELGs), and seven-class experiments where ELG were refined into active galactic nuclei (AGNs), broad-line galaxies (BLs), star-forming galaxies (SFs), and starburst galaxies (SBs). In all experiments, our proposed method is superior to direct classification. In three- and four-class, we obtains 0.77% and 1.14% improvement in accuracy, demonstrating the effectiveness of adding redshift estimation. Meanwhile, three machine learning algorithms were stacked into one by us to finish fine-grained classification, which achieved an accuracy of 78.5%, with F1 scores of 99.2% for stars, 97% for quasars, 64.3% for NGs, 60.8% for AGNs, 68.3% for BLs, 87.2% for SBs, and 71.3% for SFs. The NMAD and $R^2$ for the redshift estimation part of our method are 0.18 and 0.916, while it has only 2.65% outliers. The method we proposed further mines the information contained in the photometry to achieve comprehensive and fine-grained classification, which will be beneficial for immediate analysis in large-scale surveys. Besides, this method can leverage feature importance to stimulate new insights for astronomers.