International Journal of Modern Physics D

The Large High Altitude Air Shower Observatory (LHAASO) has recently published the first results, including the discovery of 12 ultrahigh-energy gamma-ray sources (with emission above 100TeV) above $7\sigma$ confidence level and a detailed analysis of Crab Nebula. This contribution gives a brief introduction to the LHAASO experiment and its recent discoveries.

Cosmological and astrophysical surveys in various wavebands, in particular from the radio to the far-infrared, offer a unique view of the universe’s properties and the formation and evolution of its structures. After a preamble on the so-called tension problem, which occurs when different types of data are used to determine cosmological parameters, we discuss the role of fast radio bursts in cosmology, in particular for the missing baryon problem, and the perspectives from the analysis of the 21 cm redshifted line from neutral hydrogen. We then describe the Planck Legacy Archive, its wealth of scientific information and next developments, and the promising perspectives expected from higher resolution observations, in particular for the analysis of the thermal Sunyaev–Zel’dovich effect. Three cosmological results of the Planck mission are presented next: the implications of the map of Comptonization fluctuations, the dipole analysis from cross-correlating cosmic microwave background anisotropy and Comptonization fluctuation maps, and the constraints on the primordial tensor-to-scalar perturbation ratio. Finally, we discuss some future perspectives and alternative scenarios in cosmology, such as the study of the Lorentz invariance violation with the cosmic microwave background polarization, the introduction of new gravitational degrees of freedom to solve the dark matter problem, and the exploitation of the magnification bias with high-redshift sub-millimeter galaxies to constrain cosmological parameters.

Following the GRB 170817A prompt emission lasting a fraction of a second, $10^8$s of data in the X-rays, optical, and radio wavelengths have been acquired. We here present a model that fits the spectra, flux, and time variability of all these emissions, based on the thermal and synchrotron cooling of the expanding matter ejected in a binary white dwarf merger. The $10^{-3}{M}_{\odot }$ of ejecta, expanding at velocities of $10^9$cms${}^{-1}$, are powered by the newborn massive, fast rotating, magnetized white dwarf with a mass of $1.3M_{\odot }$, a rotation period of $\gtrsim 12$s, and a dipole magnetic field $\sim 10^{10}$ G, born in the merger of a $1.0+0.8M_{\odot }$ white dwarf binary. Therefore, the long-lasting mystery of the GRB 170817A nature is solved by the merger of a white dwarf binary that also explains the prompt emission energetics.

In this paper, we investigate the cosmological evolution of the Hubble and the matter-radiation anisotropies, characterized by $\mathrm{\Sigma }$ and ${𝒩}$, respectively, under the power-law condition ${𝒩}\sim {\mathrm{\Sigma }}^d$. This is a suitable choice in order to understand how different $\mathrm{\Sigma }$ and ${𝒩}$ would behave in the expanding universe if they had distinct orders of magnitude. Hence, their early and late-time behaviors are examined, and in particular, the dependence of their qualitative features on $d$. This includes some nontrivial aspects in their long-time dynamics, which goes beyond the reach of the linear perturbations of the homogeneous and isotropic models. Besides those cosmological concerns, the concept of anisotropy in general relativity and its counterpart in Einstein’s equations is clarified and interpreted, and the general notion of the Kasner plane, the arena where its dynamics takes place, is extended beyond the reach of the spatially homogeneous models.

In this work, we show that the structural configuration of a collection of generic nonrelativistic bosons forming a gravitationally bound Bose–Einstein condensate can be interpreted as a nonrelativistic boson star. With the approach followed in this work, we can analyze with a concise and straightforward procedure the equilibrium properties of nonrelativistic boson stars viewed as a Bose–Einstein condensate. The system’s behavior is obtained by analyzing its fundamental constituent properties, i.e. the associated single-particle properties. Additionally, we show that by expressing the corresponding Newtonian gravitational potential, under certain circumstances, as a harmonic oscillator potential one, we can describe the conditions in which the nonrelativistic boson star can form equilibrium configurations. In order to analyze the boson star’s structural configuration, we employ four different ansätzes commonly used in the literature. These ansätzes allow us to compare the cloud’s structural properties of the boson star, which leads us to obtain several gravitational equilibrium configurations from compact objects matching the size of typical stars to gigantic systems comparable to the size of galaxy cluster dark matter halos. Finally, we show that these ansätzes predict, qualitatively speaking, the same structural and gravitational equilibrium configurations for different values of the parameters involved.

In this work, we use $13$ microlensing candidates with dark lenses from OGLE III catalogue [L. Wyrzykowski et al., Mon. Not. R. Astron. Soc. 458 (2016) 3012.] and cross-match them with the GAIA catalogue. We identify the microlensing source stars in the GAIA catalogue by comparing the coordinate and the magnitude of stars and using the proper motion and the parallax parameters of the source stars. Combining with the microlensing light curves as well as the microlensing parallax effect, we determine the mass and the distance of lenses from Earth. We conclude that the lens for this set of microlensing events for the massive lenses are black hole and for the small lenses are neutron/white dwarf candidates.

The Lagrangian approach of the structure formation is generalized to Newtonian cosmologies with two gravity-coupled fluids by applying the adhesion approximation to the multistreaming regime in the absence of thermodynamic pressures. The dynamic pressures arising from the velocity dispersion are considered as second-order terms. We obtain a semi-exact master evolution equation for the mixed fluid, and derive the evolution equation of each fluid by perturbation up to second order. We find that the effects of the relative motion of two fluids on the evolution of the fluid mixture are limited but will be comparatively significant at third and higher orders.

We present a model of compact astrophysical object under General Theory of Relativity using the anisotropic extension of Tolman IV solution. The anisotropy function, derived from the model, remains well behaved throughout the interior of the star. The model satisfies several necessary conditions for a physically realistic compact star. Physical viability of the model is verified specifically by plugging in the estimated parameter values of the Low Mass X-ray Binary (LMXB) candidate 4U 1608–52. Our stability analysis of this star, by using various criteria for stability, provides satisfactory results. In connection to anisotropy, we compute the Tidal Love Number (TLN) for the compact stellar model and compare the calculated values with existing literature.

Motivated by recent works on light deflection and shadow behaviors on AdS geometries [S. Haroon, M. Jamil, K. Jusufi, K. Lin and R. B. Mann, Phys. Rev. D 99 (2019) 044015, arXiv:1810.04103; A. Belhaj, H. Belmahi and M. Benali, Phys. Lett. B 821 (2021) 136619, arXiv:2110.06771], we investigate the deflection angle of light rays by superentropic black holes. Taking appropriate approximations, we first obtain the involved expression. For large values of the impact parameter, we get a specific value being zero for ordinary black holes without AdS backgrounds. Then, we examine and analyze such an optical quantity by providing graphical discussions in terms of a bounded region of the moduli space required by superentropic black hole conditions. Concretely, we study the deflection angle aspects by varying the black hole mass being fixed in the previous findings.

In this paper, we study dynamics of massless (photon and neutrino-like) particles in the spacetime of regular Bardeen black hole (BH) in novel four-dimensional Einstein–Gauss–Bonnet (4D EGB) theory. First, we have analyzed the hor properties of the spacetime of the Bardeen BH with respect to the Gauss–Bonnet (GB) coupling parameter $\alpha$. Our detailed analysis has shown that the GB coupling parameter is limited by maximum and minimum values at, $\alpha \in (-0.15÷1)$ and the extreme value of magnetic charge of the BH depends on the parameter $\alpha$. We have explored motion of neutrino-like particles and photons around the Bardeen BH. We have also explored the possibility of mimicking cases of the spin of Kerr BH and charge of Reissner–Nordström BH by the Bardeen charge, providing the same values of impact parameter for photons corresponding to the BH shadow size. Finally, we have investigated spherically infalling accretion and shadow of the Bardeen BHs in 4D EGB theory.

In this paper, the recently proposed mass dimension one fermionic field is supposed to be responsible for the dark matter (DM) halo around galactic nuclei, through the quantum degeneracy pressure effect of the field. It will be shown that the mass-ratio relation for dwarf galaxies can be well explained for a particle DM mass of about 100–200eV. For a large galaxy, as Milky Way, the observational data for rotation curve can be well reproduced for a particle mass of about 23eV, with the addition of other substructures.