Article
Physics, Particles & Fields
Masoud Ghezelbash, Haryanto M. Siahaan
Summary: A new class of exact solutions in the Einstein-Maxwell theory was discovered by applying the Ernst magnetization process to Kerr-Newman-Taub-NUT spacetimes. The solutions were found to be regular everywhere, and quasilocal conserved quantities, the corresponding Smarr formula, and the first law of thermodynamics were also identified for these spacetimes.
EUROPEAN PHYSICAL JOURNAL C
(2021)
Article
Astronomy & Astrophysics
Meng-Yun Lai, Yun Soo Myung, Rui-Hong Yue, De-Cheng Zou
Summary: In this paper, we study the tachyonic instability of Kerr-Newman (KN) black holes in the Einstein-Maxwell-scalar (EMS) theory with nonminimal negative scalar coupling to the Maxwell term. We obtain a bound for the spin parameter a of a KN black hole in the limit of a coupling constant approaching negative infinity. Additionally, we numerically perform a 2+1-dimensional time evolution of linearized scalar field perturbation on the KN black hole background, recovering the phenomenon of spontaneous scalarization in certain regions of the parameter spaces. We also plot the corresponding threshold curves alpha(a) that describe the boundary between bald KN black holes and scalarized spinning black holes in the EMS theory.
Article
Astronomy & Astrophysics
Francisco Cabral, Francisco S. N. Lobo, Diego Rubiera-Garcia
Summary: In this study, the effects of torsion-fermionic interaction on the energy levels of fermions in Riemann-Cartan geometry are investigated using a model-independent approach. Interesting Zeeman-like effects on the energy levels of fermions and anti-fermions are found, depending on their alignment with respect to the axial vector part of the torsion. The study also discusses non-minimal couplings between fermionic fields and torsion in Einstein-Cartan theory and its extension to include parity-breaking interactions. Furthermore, the potential detection of torsion effects in astrophysics, cosmology, and solid state physics is elaborated using current capabilities.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Astronomy & Astrophysics
Martin Blaschke, Zdenek Stuchlik, Sudipta Hensh
Summary: We study the evolution of the braneworld Kerr-Newman (K-N) naked singularities with a focus on the influence of tidal charge. We find that counterrotating accretion transforms a K-N naked singularity into an extreme black hole, while corotating accretion leads to various outcomes. Notably, a low-spin naked singularity with a dimensionless tidal charge less than 0.25 can be converted into an extreme black hole, whereas other cases result in transcendent states.
Article
Astronomy & Astrophysics
V. S. Manko, E. Ruiz
Summary: In this paper, two physically meaningful configurations of a pair of equal Kerr-Newman corotating black holes separated by a massless strut are elaborated using the general equatorially symmetric two-soliton solution. The thermodynamic properties of these binary configurations are studied and the first law of thermodynamics taking correctly into account the magnetic field contribution is formulated for each case.
Article
Astronomy & Astrophysics
I Cabrera-Munguia
Summary: This paper studies binary systems composed of two unequal co-and counter-rotating extreme Kerr-Newman black holes within the framework of stationary axisymmetric spacetimes. The metric describing both configurations is introduced in a closed analytical form. The obtained results are novel and significant for understanding the merging process.
Article
Astronomy & Astrophysics
Yun Soo Myung
Summary: The conditions for superradiant instability of Kerr-Newman black holes under a charged massive scalar perturbation are found by analyzing the asymptotic scalar potential and far-region wave function. It is also discovered that the conditions for superradiant stability of Kerr-Newman black holes correspond to the absence of a trapping well. The analysis is applied to Kerr black holes to find a condition for superradiant instability.
Article
Astronomy & Astrophysics
Meng-Yun Lai, Yun Soo Myung, Rui-Hong Yue, De-Cheng Zou
Summary: We investigate the onset of spontaneous scalarization for Kerr-Newman black holes in the Einstein-Maxwell-scalar theory. By numerically solving the linearized scalar equation, we obtain the onset surface for spontaneous scalarization and confirm that high rotation enhances this phenomenon for KN black holes in the EMS theory.
Article
Astronomy & Astrophysics
Klaus Morawetz
Summary: The Einstein-Cartan equations in first-order action of torsion are explored, deriving consistence conditions for the torsion parameters from the Belinfante-Rosenfeld equation. Inside matter, torsion is determined by spin, resulting in an extended Oppenhaimer-Volkov equation. Outside matter, a new solution is found with torsion completely determined by the metric.
CLASSICAL AND QUANTUM GRAVITY
(2021)
Article
Physics, Particles & Fields
Guangzhou Guo, Peng Wang, Houwen Wu, Haitang Yang
Summary: In this paper, scalarized rotating black holes are constructed within the framework of Einstein-Maxwell-scalar models. The presence of scalarized KN black holes is suppressed by the black hole spin, with a maximum spin threshold. Furthermore, the paper observes the existence of unstable and stable light rings on the equatorial plane in specific parameter regimes for scalarized KN black holes.
JOURNAL OF HIGH ENERGY PHYSICS
(2023)
Article
Astronomy & Astrophysics
Kris Schroven, Saskia Grunau
Summary: This article investigates the innermost stable circular orbit (ISCO) of electrically charged particles in different spacetimes. The study shows that the radius of the ISCO is affected by the product of the charges of the particle and the black hole, while repulsive and attractive Coulomb interactions can change the characteristics of the ISCO.
Article
Astronomy & Astrophysics
Sebastian Bahamonde, Jorge Gigante Valcarcel
Summary: We present new rotating vacuum configurations endowed with both dynamical torsion and nonmetricity fields in the framework of Metric-Affine gauge theory of gravity. By considering scalar-flat Weyl-Cartan geometries, we obtain an axisymmetric Kerr-Newman solution in the decoupling limit between the orbital and the spin angular momentum.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2022)
Article
Mathematics, Applied
Christoph Krpoun, Olaf Mueller
Summary: We investigate the Dirac equation in Kerr-Newman space-time and utilize horizon penetrating coordinates and the Newman-Penrose formalism to separate the equation into radial and angular systems of ordinary differential equations. We also derive the asymptotics of the radial solutions at infinity and at the Cauchy horizon.
JOURNAL OF GEOMETRY AND PHYSICS
(2023)
Article
Physics, Particles & Fields
Chiang-Mei Chen, Sang Pyo Kim
Summary: Using the enhanced symmetry in the near horizon region of the near-extremal dyonic Kerr-Newman (KN) black hole in the (A)dS space, the exact solutions for dyonic charged scalar field are found and the Schwinger effect for the emission of electric and/or magnetic charges is explicitly computed. The emission formula confirms the universal factorization of the Schwinger formula in the AdS2 and another Schwinger formula in the two-dimensional Rindler space determined by the effective temperature and the Hawking temperature with the chemical potentials of electric and/or magnetic charges and the angular momentum. The AdS geometry of near-horizon gives the Breitenloher-Freedman (BF) bound, guaranteeing the stability of dyonic KN black holes against both the emission of charges and Hawking radiation.
EUROPEAN PHYSICAL JOURNAL C
(2023)
Article
Astronomy & Astrophysics
Joshua Foo, Michael R. R. Good
Summary: This paper examines a simplified model for Hawking radiation produced by Kerr-Newman black holes, deriving the particle spectrum of the outgoing massless, scalar field and its thermal distribution. It also calculates the particle spectrum of the extremal Kerr-Newman system, demonstrating that the total emitted energy is finite.
JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS
(2021)
Article
Physics, Multidisciplinary
Nikodem J. Poplawski
ANNALEN DER PHYSIK
(2011)
Article
Astronomy & Astrophysics
Nikodem J. Poplawski
CLASSICAL AND QUANTUM GRAVITY
(2014)
Article
Astronomy & Astrophysics
Nikodem J. Poplawski
GENERAL RELATIVITY AND GRAVITATION
(2012)
Article
Astronomy & Astrophysics
Nikodem Poplawski
GENERAL RELATIVITY AND GRAVITATION
(2014)
Article
Astronomy & Astrophysics
Nikodem J. Poplawski
Article
Astronomy & Astrophysics
Nikodem Poplawski
Article
Astronomy & Astrophysics
Nikodem Poplawski
Article
Astronomy & Astrophysics
Nikodem Poplawski
INTERNATIONAL JOURNAL OF MODERN PHYSICS D
(2018)
Article
Astronomy & Astrophysics
Nikodem Poplawski
MODERN PHYSICS LETTERS A
(2018)
Letter
Physics, Particles & Fields
Nikodem J. Poplawski
EUROPEAN PHYSICAL JOURNAL C
(2019)
Article
Physics, Multidisciplinary
Nikodem Poplawski
FOUNDATIONS OF PHYSICS
(2020)
Article
Astronomy & Astrophysics
Nikodem J. Poplawski
MODERN PHYSICS LETTERS A
(2020)
Article
Astronomy & Astrophysics
Nikodem J. Poplawski
Summary: The study examines the formation of a universe in a black hole with spin and torsion, suggesting that torsion could prevent a singularity and replace it with a nonsingular bounce, leading to a finite period of inflation.
GENERAL RELATIVITY AND GRAVITATION
(2021)
Article
Physics, Multidisciplinary
Nikodem Poplawski
Summary: The study suggests that gravitational collapse of a fluid sphere with spin and torsion into a black hole can be prevented from forming a singularity by the gravitational repulsion of torsion, resulting in a nonsingular bounce. Quantum particle production during contraction helps torsion dominate over shear, while particle production during expansion can lead to a finite period of inflation and produce significant amounts of matter. The resulting closed universe on the other side of the event horizon may undergo multiple bounces, creating an oscillatory universe that expands indefinitely. This suggests that our universe may have originated from a black hole.
JOURNAL OF EXPERIMENTAL AND THEORETICAL PHYSICS
(2021)
Article
Astronomy & Astrophysics
Nikodem Poplawski
ASTROPHYSICAL JOURNAL
(2016)
Article
Astronomy & Astrophysics
Nelson R. F. Braga, Octavio C. Junqueira
Summary: This study investigates the influence of rotation on the transition temperature of strongly interacting matter produced in non-central heavy ion collisions. By using a holographic description of an AdS black hole, the authors extend the analysis to the more realistic case where the matter spreads over a region around the rotational axis. The results show the coexistence of confined and deconfined phases and are consistent with the concept of local temperature in rotating frames developed by Tolman and Ehrenfest.
Article
Astronomy & Astrophysics
Bing Sun, Jiachen An, Zhoujian Cao
Summary: This paper investigates the effect of gravitational constant variation on the propagation of gravitational waves. By employing two analytical methods, the study finds that variations in the gravitational constant result in amplitude and phase corrections for gravitational waves, and the time variation of the gravitational constant can be constrained through the propagation of gravitational waves.
Article
Astronomy & Astrophysics
Abdellah Touati, Zaim Slimane
Summary: This letter presents the first study of Hawking radiation as a tunneling process within the framework of non-commutative gauge theory of gravity. The non-commutative Schwarzschild black hole is reconstructed using the Seiberg-Witten map and the star product. The emission spectrum of outgoing massless particles is computed using the quantum tunneling mechanism. The results reveal pure thermal radiation in the low-frequency scenario, but a deviation from pure thermal radiation in the high-frequency scenario due to energy conservation. It is also found that noncommutativity enhances the correlations between successively emitted particles.
Article
Astronomy & Astrophysics
Shahar Hod
Summary: The travel times of light signals between two antipodal points on a compact star's surface are calculated for two different trajectories. It is shown that, for highly dense stars, the longer trajectory along the surface may have a shorter travel time as measured by asymptotic observers. A critical value of the dimensionless density-area parameter is determined for constant density stars to distinguish cases where crossing through the star's center or following a semi-circular trajectory on the surface has a shorter travel time as measured by asymptotic observers.