Article
Astronomy & Astrophysics
J. Ovalle, E. Contreras, Z. Stuchlik
Summary: The research indicates that the cosmological constant is deformed near a black hole, leading to a reexamination of the black hole solution and the proposal of a new, simpler and more geometrically rich solution. A detailed study of the new black hole solution was carried out, showing the impact of rotation on the curvature, and a conjecture was made regarding its possible implications on alternative theories.
Article
Physics, Particles & Fields
Javlon Rayimbaev, Sanjar Shaymatov, Mubasher Jamil
Summary: This paper investigates circular orbits around a black hole surrounded by dark matter, showing how dark matter impacts the existence of circular orbits and exploring its applications in fitting and explaining black hole parameters.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Guillem Domenech, Misao Sasaki
Summary: The end state of Hawking evaporation of a black hole is uncertain. Some quantum gravity theories suggest the existence of Planck sized remnants, such as loop quantum gravity and asymptotic safe gravity. If this is the case, the Universe might be filled with remnants of tiny primordial black holes, formed with mass M<109 M & SIM; 5x105.
CLASSICAL AND QUANTUM GRAVITY
(2023)
Article
Physics, Particles & Fields
Sanjar Shaymatov, Bobomurat Ahmedov, Mubasher Jamil
Summary: This study tests the weak cosmic censorship conjecture for the Reissner-Nordstrom-de Sitter black hole surrounded by perfect fluid dark matter, showing that even in a realistic scenario with cosmological parameters, the black hole cannot be overcharged unless the induced fields by dark matter and cosmological parameters are completely balanced. Additionally, it is found that a certain threshold limit exists beyond which the black hole cannot be overcharged, indicating that the effect of the cosmological constant dominates over the effect of perfect fluid dark matter in the overcharging process.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Haximjan Abdusattar
Summary: In this paper, the authors investigate the Ruppeiner thermodynamic geometry in the extended phase space of Reissner-Nordstrom (RN)-AdS black holes immersed in perfect fluid dark matter (PFDM) via P - V criticality. They find that the critical exponents near the critical point are consistent with those in the mean field theory and satisfy the scaling laws, suggesting that the PFDM does not change the critical exponents. Furthermore, they study the divergence behavior of the thermodynamic curvature scalar of this black hole at the critical point of P - V phase transition. They discover that the behavior of the Ruppeiner curvature scalar near criticality is characterized by a dimensionless constant identical with the van der Waals fluid.
PHYSICS OF THE DARK UNIVERSE
(2023)
Article
Astronomy & Astrophysics
Lam Hui, Y. . T. Albert Law, Luca Santoni, Guanhao Sun, Giovanni Maria Tomaselli, Enrico Trincherini
Summary: Studies on black hole superradiance often focus on the growth of a cloud in isolation and the spin-down of the black hole. However, this paper considers the additional effect of matter and angular momentum accretion from the surrounding environment. The authors demonstrate that the black hole can evolve by drifting along the superradiance threshold, allowing for analytical or semi-analytical description of its parameter evolution. They also propose the concept of oversuperradiance, where accretion effectively feeds the superradiance cloud through the black hole. Two examples of accretion processes are provided: from a vortex in wave dark matter and from a baryonic disk. The paper also discusses level transition in a similar manner.
Article
Astronomy & Astrophysics
Ratchaphat Nakarachinda, Chakrit Pongkitivanichkul, Daris Samart, Lunchakorn Tannukij, Pitayuth Wongjun
Summary: This study investigates the role of anti-de Sitter black hole in the holographic principle. By modifying the upper bound of energy corresponding to the mass of the black hole, the constant term in the energy density of the holographic dark energy is obtained. The cosmic evolution is explored and the accelerated expansion at late time is observed in the proposed model.
Article
Astronomy & Astrophysics
Emil T. Akhmedov, Kirill V. Bazarov
Summary: In this paper, we study a quantum real massive scalar field in the de Sitter-Schwarzschild spacetime background. To make analytical progress, we focus on the two-dimensional case, assuming that the situation in four dimensions will be similar conceptually. We assume the quantum field to be in a thermal state, described by the Planckian distribution for the exact modes in the given geometry. We approximately calculate the expectation value of the stress-energy tensor near the cosmological and black hole horizons. It is found that the geometry is strongly modified by the quantum fluctuations of the matter fields, due to the backreaction from quantum fields with a generic temperature.
Article
Astronomy & Astrophysics
D. Pugliese, Z. Stuchlik
Summary: By comparing different dark matter models, we have investigated the influence of dark matter on black hole accretion disk physics. Our results show that the accretion onto a black hole can serve as a good indicator of the presence of dark matter. We have analyzed the accretion around spinning black holes immersed in perfect-fluid dark matter, cold dark matter, and scalar field dark matter. The study reveals distinctive effects of dark matter on toroidal accretion disks and protojet configurations, suggesting that black hole accretion tori immersed in dark matter may exhibit characteristics similar to superspinars and naked singularity attractors.
Article
Physics, Multidisciplinary
Eunice Omwoyo, Humberto Belich, Julio C. Fabris, Hermano Velten
Summary: Analytical solutions using Jacobi elliptic functions for bound and nearly bound photon orbits in Kerr-de Sitter and Kerr-de Sitter revisited spacetimes are derived in this paper. Analytic ray-tracing is conducted based on the obtained solutions in both spacetimes. Direct images, lensing rings and photon rings for equatorial disks are obtained for inclined locally static observers. The images corresponding to n = (2, 3) exhibit a significantly closer resemblance to the critical curve, showcasing the potential of these higher-order images as robust testing grounds for general relativity.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Astronomy & Astrophysics
Yu Cheng, Shao-Feng Ge, Xiao-Gang He, Jie Sheng
Summary: The possibility of reactivating the forbidden annihilation channel of dark matter around supermassive black holes has been discovered, providing a unique signal that can serve as evidence for its existence. Fermi-LAT data around Sgr ★ provides preliminary support for this theory.
Article
Astronomy & Astrophysics
Cheng-Yong Zhang, Peng Liu, Yun-Qi Liu, Chao Niu, Bin Wang
Summary: The study focuses on the fully nonlinear dynamics of spherically symmetric black hole spontaneous scalarization in Einstein-Maxwell-scalar theory. It is found that by adjusting the coupling function and black hole charge, the development and stabilization of hairy black holes can be influenced.
Article
Mathematics, Applied
Peter Hintz
Summary: The article presents a method for constructing dynamical many-black-hole spacetimes with well-controlled asymptotic behavior as solutions of the Einstein vacuum equation. It involves gluing different types of black hole metrics around points on the future conformal boundary of de Sitter space and solving the Einstein equation while considering scattering data. The main step in the construction is solving a linear divergence equation for trace-free symmetric 2-tensors, which is closely related to Friedrich's analysis of scattering problems on asymptotically simple spacetimes.
COMMUNICATIONS IN PARTIAL DIFFERENTIAL EQUATIONS
(2021)
Article
Astronomy & Astrophysics
Ruth Gregory, Ian G. Moss, Naritaka Oshita, Sam Patrick
Summary: In this study, we investigate the evaporation process of a Kerr-de Sitter black hole with the Unruh-Hawking-like vacuum state and calculate the greybody factors for different particles. The presence of the cosmological constant dampens the amplification factor, approaching zero near the critical point where the Nariai and extremal limits merge. Despite the proximity to the critical point, gravitons exhibit more significant superradiance compared to photons and scalar particles, carrying angular momentum at a faster rate than mass energy decreases. The total entropy of the black hole and cosmological horizon increases with time, in accordance with the generalized second law of thermodynamics.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
Miguel Correa, Mayukh R. Gangopadhyay, Nur Jaman, Grant J. Mathews
Summary: This study investigates the natural warm inflationary paradigm and reveals two significant new findings. Firstly, the observational constraints on the primordial power spectrum from the cosmic microwave background (CMB) can be met within the Planck scale of the effective field theory. Secondly, the natural warm inflationary paradigm can inevitably generate primordial black holes (PBHs) in a specific mass range, which can account for the entirety of the universe's dark matter while satisfying observational constraints.
Article
Physics, Multidisciplinary
Z. Yousaf, M. Z. Bhatti, Maxim Khlopov, H. Asad
Summary: This paper examines the characteristics of static irrotational matter with hyperbolic symmetry using metric f(R) gravity. It reveals the existence of an empty core and negative effective energy density, which could be crucial for understanding quantum field events. Relationships among matter variables and structure scalars are determined, and hyperbolically symmetric cosmological models are studied through generating functions.
Article
Astronomy & Astrophysics
Z. Yousaf, Maxim Yu Khlopov, M. Z. Bhatti, H. Asad
Summary: In this work, the study focuses on the fluid distributions affected by electromagnetism, specifically on the hyperbolically symmetric metric. Modified gravitational formulations with charge are used to calculate the effective energy-momentum tensor, which is then refined using tetrad field components in the Minkowski coordinate system. The results show that the hyperbolically symmetrical source has a negative effective matter density in all stellar formulations. This emphasizes the importance of quantum processes and specific constraints in explaining physical phenomena under the influence of electromagnetic fields.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Multidisciplinary Sciences
Arnab Chaudhuri, Maxim Yu. Khlopov, Shiladitya Porey
Summary: The density of dark matter can be reduced if entropy production occurs after the freeze-out of dark matter particles in the early universe. This study investigates the possibility of such reduction due to entropy production in the electroweak phase transition. The authors compare scenarios of entropy production in the standard model and its simplest extension, the two-Higgs doublet model. The findings suggest that the dilution effect in the electroweak phase transition has significant implications for the observation of various forms of dark matter.
Article
Astronomy & Astrophysics
Oem Trivedi, Maxim Khlopov
Summary: Interest in cosmological singularities, particularly future singularities, has grown recently with the discovery of late-time acceleration and dark energy. This study explores the occurrence of w-singularities in various non-standard cosmologies and finds that they occur under the same conditions as in the usual general relativistic cosmology. These unexpected results highlight the similarities between non-standard and standard cosmologies in terms of the conditions for cosmological singularities.
PHYSICS OF THE DARK UNIVERSE
(2022)
Article
Physics, Multidisciplinary
Indranath Bhattacharyya, Saibal Ray, Maxim Khlopov, Rau Nag, Samudra Sundar Nag
Summary: The study focuses on the McVittie solution of the Einstein equations, which describes a black hole embedded in dynamic spacetime. It examines the geodesic of test particles falling towards the black hole in the Schwarzschild-de Sitter spacetime, showing that the behavior differs from the Schwarzschild case. The research reveals that observers or particle systems are stretched near the black hole singularity in the SdS spacetime.
FORTSCHRITTE DER PHYSIK-PROGRESS OF PHYSICS
(2022)
Article
Multidisciplinary Sciences
Vladislav Golubkov, Maxim Khlopov, Anastasia Kirichenko, Alexandra Kravtsova, Andrey Mayorov, Rustam Yulbarisov
Summary: Several candidates for anti-helium events have been discovered in the AMS-02 experiment, suggesting the existence of antimatter stars in our galaxy. Numerical studies were conducted to simulate the creation and propagation of anti-helium flux from antimatter globular clusters, providing insights into the magnetic cutoff for the penetration of anti-helium nuclei into the Galaxy disk and the energy range for optimal search and detection of anti-helium.
Article
Astronomy & Astrophysics
Oem Trivedi, Maxim Khlopov
Summary: This study explores the formation of cosmological singularities in asymptotically safe cosmology using renormalization group approaches. It discovers special conditions and forms of cosmological singularities in this cosmology, which differ significantly from standard cosmology and do not require free parameters. Additionally, conventional singularity removal methods are ineffective in this cosmology.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Review
Multidisciplinary Sciences
Irina Dymnikova, Anna Dobosz
Summary: In this article, we provide an overview of the basic properties and generic behavior of circular equatorial particle orbits and light rings around regular rotating compact objects with dark energy interiors. These objects are described by regular metrics of the Kerr-Schild class and include rotating black holes and self-gravitating spinning solitons. Our study reveals that these objects have an internal de Sitter vacuum disk and can have two types of dark interiors, depending on the energy conditions. We also discuss the importance of innermost stable orbits and light rings as diagnostic tools for investigating the dark interiors of de Sitter-Kerr objects and observing rotating black holes.
Article
Multidisciplinary Sciences
Vitaly A. Beylin, Maxim Yu. Khlopov, Danila O. Sopin
Summary: The new stable fermion family should participate in sphaleron transitions in the early Universe before the breaking of the electroweak symmetry in the Standard Model. The conditions for the balance between the excess of new fermions (additional superheavy U, D quarks, and new E, N leptons) and baryon asymmetry were considered using a system of equations for chemical potentials, both above and below the phase transition.
Article
Multidisciplinary Sciences
Maxim Khlopov, Sourav Roy Chowdhury
Summary: An investigation has been conducted on a reconfigured form of the Einstein-Hilbert action, f(R,Tf), which involves the energy-momentum tensor trace of a scalar field. The study focuses on how the structural behavior of the scalar field changes with the shape of the potential, resulting in a new set of Friedmann equations. In the context of modified theories, researchers have explored the range of gravitational wave polarization modes associated with relevant fields, identifying two additional scalar modes: a massive longitudinal mode and a massless transverse mode, known as the breathing mode.
Article
Astronomy & Astrophysics
Maxim Yu. Khlopov, Orchidea Maria Lecian
Summary: If baryosynthesis is strongly nonhomogeneous, macroscopic regions with antibaryon excess can be created, potentially confirming the existence of primordial antimatter objects in our Galaxy. By analyzing the evolution of antibaryon domains and considering the annihilation of baryon-antibaryon at the domain borders, as well as the possible Swiss cheese structure of the domains, we can understand the possible forms and properties of antimatter bodies in our Galaxy. This formalism provides the creation of evolutionary scenarios linking nonhomogeneous baryosynthesis to antimatter evolution in our expanding Universe.
Article
Physics, Multidisciplinary
Z. Yousaf, Maxim Yu Khlopov, Bander Almutairi, M. M. M. Nasir
Summary: In this article, we explore simpler models for charged spherically symmetric structures. By using orthogonal splitting technique, we formulate two different expressions for stellar mass in terms of structure scalars. We find that the structure scalar YTF serves as a complexity factor in studying various characteristics of relativistic spherical interiors.
Article
Astronomy & Astrophysics
Vitaly A. Beylin, Maxim Yu. Khlopov, Danila O. Sopin
Summary: According to the walking technicolor models, stable multiple charged particles can possess electroweak charges. An asymmetry of these particles can be balanced by sphaleron transitions, which can provide an excess of baryons and/or leptons. This paper considers the possibility of generating a sufficient amount of particles with charge -2n, in the form of bound states of multiple charged techniparticles with n helium nuclei (dark atoms), to explain the observed dark matter density within the framework of thermodynamic approach.
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2023)
Proceedings Paper
Astronomy & Astrophysics
Andrea Addazi, Konstantin Belotsky, Vitaly Beylin, Marco Cirelli, Arman Esmaili, Nicolao Fornengo, Qingyu Gan, Michael Kachekriess, Maxim Khlopov, Vladimir Korchagin, Alexander Korochkin, Vladimir Kuksa, Antonino Marciano, Andrei Neronov, Paolo Panci, Roman Pasechnick, Alexander Sakharov, Filippo Sala, Pino Di Sciascio, Dimitri Semikoz, Pasquale Dario Serpico, Nikolay Volchanskiy
37TH INTERNATIONAL COSMIC RAY CONFERENCE, ICRC2021
(2022)
Article
Physics, Particles & Fields
Oem Trivedi, Maxim Khlopov
Summary: The study of the true nature of dark energy is an exciting topic in cosmology. In this work, the authors investigate the existence of finite time singularities in scalar field dark energy models based on the RS-II Braneworld. The results show that these models can exhibit various types of singularities under certain initial conditions.
EUROPEAN PHYSICAL JOURNAL C
(2022)