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Journal articles on the topic 'Newman-Janis Algorithm'

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Published: 10 March 2023

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1

Brauer, O., H. A. Camargo, and M. Socolovsky. "Newman-Janis Algorithm Revisited." International Journal of Theoretical Physics 54, no. 1 (July 2, 2014): 302–14. http://dx.doi.org/10.1007/s10773-014-2225-3.

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2

Harold Erbin and Lucien Heurtier. "Five-dimensional Janis–Newman algorithm." Classical and Quantum Gravity 32, no. 16 (July 23, 2015): 165004. http://dx.doi.org/10.1088/0264-9381/32/16/165004.

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3

Rajan, Del, and Matt Visser. "Cartesian Kerr–Schild variation on the Newman–Janis trick." International Journal of Modern Physics D 26, no. 14 (December 2017): 1750167. http://dx.doi.org/10.1142/s021827181750167x.

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The Newman–Janis trick is a procedure, (not even really an ansatz), for obtaining the Kerr spacetime from the Schwarzschild spacetime. This 50 years old trick continues to generate heated discussion and debate even to this day. Most of the debate focusses on whether the Newman–Janis procedure can be upgraded to the status of an algorithm, or even an inspired ansatz, or is it just a random trick of no deep physical significance. (That the Newman–Janis procedure very quickly led to the discovery of the Kerr–Newman spacetime is a point very much in its favor.) In the current paper, we will not answer these deeper questions, we shall instead present a much simpler alternative variation on the theme of the Newman–Janis trick that might be easier to work with. We shall present a 2-step version of the Newman–Janis trick that works directly with the Kerr–Schild “Cartesian” metric presentation of the Kerr spacetime. That is, we show how the original 4-step Newman–Janis procedure can, (using the interplay between oblate spheroidal and Cartesian coordinates), be reduced to a considerably cleaner 2-step process.

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4

Keane, Aidan J. "An extension of the Newman–Janis algorithm." Classical and Quantum Gravity 31, no. 15 (July 14, 2014): 155003. http://dx.doi.org/10.1088/0264-9381/31/15/155003.

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5

Erbin, Harold. "Janis-Newman algorithm for supergravity black holes." Fortschritte der Physik 64, no. 4-5 (March 15, 2016): 376–77. http://dx.doi.org/10.1002/prop.201500065.

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6

Gutiérrez-Chávez, Carlos, Francisco Frutos-Alfaro, Iván Cordero-García, and Javier Bonatti-González. "A Computer Program for the Newman-Janis Algorithm." Journal of Modern Physics 06, no. 15 (2015): 2226–30. http://dx.doi.org/10.4236/jmp.2015.615227.

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7

Erbin, Harold, and Lucien Heurtier. "Supergravity, complex parameters and the Janis–Newman algorithm." Classical and Quantum Gravity 32, no. 16 (July 23, 2015): 165005. http://dx.doi.org/10.1088/0264-9381/32/16/165005.

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8

Drake, S. P., and Peter Szekeres. "Uniqueness of the Newman–Janis Algorithm in Generating the Kerr–Newman Metric." General Relativity and Gravitation 32, no. 3 (March 2000): 445–57. http://dx.doi.org/10.1023/a:1001920232180.

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9

Babar, Rimsha, Muhammad Asgher, and Riasat Ali. "Gravitational analysis of Einstein-non-linear-Maxwell-Yukawa black hole under the effect of Newman-Janis algorithm." Physica Scripta 97, no. 12 (October 28, 2022): 125201. http://dx.doi.org/10.1088/1402-4896/ac9863.

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Abstract In this paper, we analyze the rotating Einstein-non-linear-Maxwell-Yukawa black hole solution by Janis-Newman algorithmic rule and complex calculations. We investigate the basic properties (i.e., Hawking radiation) for the corresponding black hole solution. From the horizon structure of the black hole, we discuss the graphical behavior of Hawking temperature T H and analyze the effects of spin parameter (appears due to Newman-Janis approach) on the T H of black hole. Furthermore, we investigate the corrected temperature for rotating Einstein-non-linear-Maxwell-Yukawa black hole by using the vector particles tunneling strategy which is based on Hamilton-Jacobi method. We additionally study the graphical explanation of corrected T H through outer horizon to investigate the physical and stable conditions of black hole. Finally, we compute the corrected entropy and check that the effect of charged, rotation and gravity on entropy.

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10

Erbin, Harold. "Janis–Newman Algorithm: Generating Rotating and NUT Charged Black Holes." Universe 3, no. 1 (March 7, 2017): 19. http://dx.doi.org/10.3390/universe3010019.

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11

Lombardo, Diego Julio Cirilo. "The Newman–Janis algorithm, rotating solutions and Einstein–Born–Infeld black holes." Classical and Quantum Gravity 21, no. 6 (February 20, 2004): 1407–17. http://dx.doi.org/10.1088/0264-9381/21/6/009.

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12

Larrañaga, Alexis, Claudia Grisales, and Manuel Londoño. "A Topologically Charged Rotating Black Hole in the Brane." Advances in High Energy Physics 2013 (2013): 1–6. http://dx.doi.org/10.1155/2013/727294.

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We have obtained a rotating black hole solution in the braneworld scenario by applying the Newman-Janis algorithm. The new solution carries two types of charge, one arising from the bulk Weyl tensor and one from the gauge field trapped on the brane. In order to obtain this result, we used a modified version of the algorithm in which the involved complexification is the key point. The analysis of the horizon structure of the new metric shows similarities to the Kerr-Newman solution. In particular, there is a minimal mass to which the black hole can decay through the Hawking radiation. From the thermodynamical analysis, the possibility of a degenerate horizon gives a temperature that, instead of a divergent behaviour at short scales, admits both a minimum and a maximum before cooling down towards a zero temperature remnant configuration.

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13

VIAGGIU, STEFANO. "INTERIOR KERR SOLUTIONS WITH THE NEWMAN–JANIS ALGORITHM STARTING WITH STATIC PHYSICALLY REASONABLE SPACE–TIMES." International Journal of Modern Physics D 15, no. 09 (September 2006): 1441–53. http://dx.doi.org/10.1142/s0218271806009169.

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We present a simple approach for obtaining Kerr interior solutions with the help of the Newman–Janis algorithm (NJA) starting with static space–times describing physically sensible interior Schwarzschild solutions. In this context, the Darmois–Israel (DI) junction conditions are analyzed. Starting from the incompressible Schwarzschild solution, a class of Kerr interior solutions is presented, together with a discussion of the slowly rotating limit. The energy conditions are discussed for the solutions so obtained. Finally, the NJA algorithm is applied to the static, anisotropic, conformally flat solutions found by Stewart leading to interior Kerr solutions with oblate spheroidal boundary surfaces.

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14

Dymnikova, Irina, and Evgeny Galaktionov. "Dynamics of Electromagnetic Fields and Structure of Regular Rotating Electrically Charged Black Holes and Solitons in Nonlinear Electrodynamics Minimally Coupled to Gravity." Universe 5, no. 10 (September 27, 2019): 205. http://dx.doi.org/10.3390/universe5100205.

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We study the dynamics of electromagnetic fields of regular rotating electrically charged black holes and solitons replacing naked singularities in nonlinear electrodynamics minimally coupled to gravity (NED-GR). They are related by electromagnetic and gravitational interactions and described by the axially symmetric NED-GR solutions asymptotically Kerr-Newman for a distant observer. Geometry is described by the metrics of the Kerr-Schild class specified by T t t = T r r ( p r = − ρ ) in the co-rotating frame. All regular axially symmetric solutions obtained from spherical solutions with the Newman-Janis algorithm belong to this class. The basic generic feature of all regular objects of this class, both electrically charged and electrically neutral, is the existence of two kinds of de Sitter vacuum interiors. We analyze the regular solutions to dynamical equations for electromagnetic fields and show which kind of a regular interior is favored by electromagnetic dynamics for NED-GR objects.

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15

Drake, S. P., and R. Turolla. "The application of the Newman - Janis algorithm in obtaining interior solutions of the Kerr metric." Classical and Quantum Gravity 14, no. 7 (July 1, 1997): 1883–97. http://dx.doi.org/10.1088/0264-9381/14/7/021.

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16

Dymnikova, Irina. "Image of the Electron Suggested by Nonlinear Electrodynamics Coupled to Gravity." Particles 4, no. 2 (March 26, 2021): 129–45. http://dx.doi.org/10.3390/particles4020013.

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We present a systematic review of the basic features that were adopted for different electron models and show, in a brief overview, that, for electromagnetic spinning solitons in nonlinear electrodynamics minimally coupled to gravity (NED-GR), all of these features follow directly from NED-GR dynamical equations as model-independent generic features. Regular spherically symmetric solutions of NED-GR equations that describe electrically charged objects have obligatory de Sitter center due to the algebraic structure of stress–energy tensors for electromagnetic fields. By the Gürses-Gürsey formalism, which includes the Newman–Janis algorithm, they are transformed to axially symmetric solutions that describe regular spinning objects asymptotically Kerr–Newman for a distant observer, with the gyromagnetic ratio g=2. Their masses are determined by the electromagnetic density, related to the interior de Sitter vacuum and to the breaking of spacetime symmetry from the de Sitter group. De Sitter center transforms to the de Sitter vacuum disk, which has properties of a perfect conductor and ideal diamagnetic. The ring singularity of the Kerr–Newman geometry is replaced with the superconducting current, which serves as the non-dissipative source for exterior fields and source of the intrinsic magnetic momentum for any electrically charged spinning NED-GR object. Electromagnetic spinning soliton with the electron parameters can shed some light on appearance of a minimal length scale in the annihilation reaction e+e−→γγ(γ).

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Dymnikova, Irina, and Kirill Kraav. "Identification of a Regular Black Hole by Its Shadow." Universe 5, no. 7 (July 3, 2019): 163. http://dx.doi.org/10.3390/universe5070163.

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We study shadows of regular rotating black holes described by the axially symmetric solutions asymptotically Kerr for a distant observer, obtained from regular spherical solutions of the Kerr–Schild class specified by T t t = T r r ( p r = − ε ) . All regular solutions obtained with the Newman–Janis algorithm belong to this class. Their basic generic feature is the de Sitter vacuum interior. Information about the interior content of a regular rotating de Sitter-Kerr black hole can be in principle extracted from observation of its shadow. We present the general formulae for description of shadows for this class of regular black holes, and numerical analysis for two particular regular black hole solutions. We show that the shadow of a de Sitter-Kerr black hole is typically smaller than that for the Kerr black hole, and the difference depends essentially on the interior density and on the pace of its decreasing.

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18

Jusufi, Kimet, Mustapha Azreg-Aïnou, Mubasher Jamil, and Qiang Wu. "Equatorial and Polar Quasinormal Modes and Quasiperiodic Oscillations of Quantum Deformed Kerr Black Hole." Universe 8, no. 4 (March 26, 2022): 210. http://dx.doi.org/10.3390/universe8040210.

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In this paper, we focus on the relation between quasinormal modes (QNMs) and a rotating black hole shadow. As a specific example, we consider the quantum deformed Kerr black hole obtained via Newman–Janis–Azreg-Aïnou algorithm. In particular, using the geometric-optics correspondence between the parameters of a QNMs and the conserved quantities along geodesics, we show that, in the eikonal limit, the real part of QNMs is related to the Keplerian frequency for equatorial orbits. To this end, we explore the typical shadow radius for the viewing angles, θ0=π/2, and obtained an interesting relation in the case of viewing angle θ0=0 (or equivalently θ0=π). Furthermore we have computed the corresponding equatorial and polar modes and the thermodynamical stability of the quantum deformed Kerr black hole. We also investigate other astrophysical applications such as the quasiperiodic oscillations and the motion of S2 star to constrain the quantum deforming parameter.

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19

Dymnikova, Irina, Anna Dobosz, and Bożena Sołtysek. "Classification of Circular Equatorial Orbits around Regular Rotating Black Holes and Solitons with the de Sitter/ Phantom Interiors." Universe 8, no. 2 (January 20, 2022): 65. http://dx.doi.org/10.3390/universe8020065.

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We study the basic properties of the circular equatorial orbits for the regular axially symmetric solutions, obtained with using the Gürses–Gürsey formalism which includes the Newman–Janis algorithm, from regular spherically symmetric metrics of the Kerr–Schild class specified by Ttt=Trr. Solutions of this class describe regular rotating black holes and spinning solitons replacing naked singularities. All these objects have the interior de Sitter equatorial disk, and can have two kinds of interiors determined by the energy conditions. One of them contains an additional interior de Sitter vacuum S-surface with the de Sitter disk as a bridge, whose internal cavities are filled with a phantom fluid. We study in detail the innermost equatorial circular orbits and show that in the field of spinning solitons, the innermost orbits exist within ergoregions related to phantom regions. We show also that around spinning solitons there can exist four corotating light rings and around a regular black hole, one corotating light ring, which is stable for a certain class of black holes. For all objects there exists one counterrotating light ring.

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20

Hendi, S. H., Kh Jafarzade, and B. Eslam Panah. "Black holes in dRGT massive gravity with the signature of EHT observations of M87*." Journal of Cosmology and Astroparticle Physics 2023, no. 02 (February 1, 2023): 022. http://dx.doi.org/10.1088/1475-7516/2023/02/022.

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Abstract The recent Event Horizon Telescope (EHT) observations of the M87* have led to a surge of interest in studying the shadow of black holes. Besides, investigation of time evolution and lifetime of black holes helps us to veto/restrict some theoretical models in gravitating systems. Motivated by such exciting properties, we study optical features of black holes, such as the shadow geometrical shape and the energy emission rate in modified gravity. We consider a charged AdS black hole in dRGT massive gravity and look for criteria to restrict the free parameters of the theory. The main goal of this paper is to compare the shadow of the mentioned black hole in a rotating case with the EHT data to obtain the allowed regions of the model parameters. Therefore, we employ the Newman-Janis algorithm to build the rotating counterpart of static solution in dRGT massive gravity. We also calculate the energy emission rate for the rotating case and discuss how the rotation factor and other parameters affect the emission of particles around the black holes.

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21

Kumar, Jitendra, Shafqat Ul Islam, and Sushant G. Ghosh. "Loop Quantum Gravity motivated multihorizon rotating black holes." Journal of Cosmology and Astroparticle Physics 2022, no. 11 (November 1, 2022): 032. http://dx.doi.org/10.1088/1475-7516/2022/11/032.

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Abstract With a semiclassical polymerization in the loop quantum gravity (LQG), the interior of the Schwarzschild black holes provides a captivating single-horizon regular black hole spacetime. The shortage of rotating black hole models in loop quantum gravity (LQG) substantially restrains the progress of testing LQG from observations. Motivated by this, starting with a spherical LQG black hole as a seed metric, we construct a rotating spacetime using the revised Newman-Janis algorithm, namely, the LQG-motivated rotating black holes (LMRBH), which encompasses Kerr (l = 0) black holes as an exceptional case. We discover that for any random l > 0, unlike Kerr black hole, an extremal LMRBH refers to a black hole with angular momentum a > M. The rotating metric, in parameter space, describes (1) black holes with an event and Cauchy horizon, (2) black holes with three horizons, (3) black holes with only one horizon or (4) no horizon spacetime. We also discuss the horizon and global structure of the LMRBH spacetimes and its dependence on l/M that exhibits rich spacetime structures in the (M, a, l) parameter space.

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22

Ma, Tian-Chi, He-Xu Zhang, Peng-Zhang He, Hao-Ran Zhang, Yuan Chen, and Jian-Bo Deng. "Shadow cast by a rotating and nonlinear magnetic-charged black hole in perfect fluid dark matter." Modern Physics Letters A 36, no. 17 (May 28, 2021): 2150112. http://dx.doi.org/10.1142/s0217732321501121.

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In this paper, we derived an exact solution of the spherically symmetric Hayward black hole surrounded by perfect fluid dark matter (PFDM). By applying the Newman–Janis algorithm, we generalized it to the corresponding rotating black hole. Then, we studied the shadows of rotating Hayward black hole in PFDM. The apparent shape of the shadow depends upon the black hole spin [Formula: see text], the magnetic charge [Formula: see text] and the PFDM intensity parameter [Formula: see text]. The shadow is a perfect circle in the non-rotating case [Formula: see text] and a deformed one in the rotating case [Formula: see text]. For a fixed value of [Formula: see text], the size of the shadow increases with the increasing [Formula: see text], but decreases with the increasing [Formula: see text]. We further investigated the black hole emission rate. We found that the emission rate decreases with the increasing [Formula: see text] (or [Formula: see text]) and the peak of the emission shifts to lower frequency. Finally, we discussed the observational prospects corresponding to the supermassive black hole Sgr A[Formula: see text] at the center of the Milky Way.

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Shaikh, Rajibul, Kunal Pal, Kuntal Pal, and Tapobrata Sarkar. "Constraining alternatives to the Kerr black hole." Monthly Notices of the Royal Astronomical Society 506, no. 1 (June 28, 2021): 1229–36. http://dx.doi.org/10.1093/mnras/stab1779.

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ABSTRACT The recent observation of the shadow of the supermassive compact object M87* by the Event Horizon Telescope (EHT) collaboration has opened up a new window to probe the strong gravity regime. In this paper, we study shadows cast by two viable alternatives to the Kerr black hole, and compare them with the shadow of M87*. The first alternative is a horizonless compact object (HCO) having radius r0 and exterior Kerr geometry. The second one is a rotating generalization of the recently obtained one parameter (r0) static metric by Simpson and Visser. This latter metric, constructed using the Newman–Janis algorithm, is a special case of a parametrized rotating non-Kerr geometry obtained by Johannsen. Here, we constrain the parameter r0 of these alternatives using the results from M87* observation. We find that, for the mass, inclination angle and the angular diameter of the shadow of M87* reported by the EHT collaboration, the maximum value of the parameter r0 must be in the range 2.54r+ ≤ r0, max ≤ 3.51r+ for the dimensionless spin range 0.5 ≤ a* ≤ 0.94, with r+ being the outer horizon radius of the Kerr black hole at the corresponding spin value. We conclude that these black hole alternatives having r0 below this maximum range (i.e. r0 ≤ r0, max) is consistent with the size and deviation from circularity of the observed shadow of M87*.

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24

Dymnikova, Irina. "Dark Matter Candidates with Dark Energy Interiors Determined by Energy Conditions." Symmetry 12, no. 4 (April 22, 2020): 662. http://dx.doi.org/10.3390/sym12040662.

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We outline the basic properties of regular black holes, their remnants and self-gravitating solitons G-lumps with the de Sitter and phantom interiors, which can be considered as heavy dark matter (DM) candidates generically related to a dark energy (DE). They are specified by the condition T t t = T r r and described by regular solutions of the Kerr-Shild class. Solutions for spinning objects can be obtained from spherical solutions by the Newman-Janis algorithm. Basic feature of all spinning objects is the existence of the equatorial de Sitter vacuum disk in their deep interiors. Energy conditions distinguish two types of their interiors, preserving or violating the weak energy condition dependently on violation or satisfaction of the energy dominance condition for original spherical solutions. For the 2-nd type the weak energy condition is violated and the interior contains the phantom energy confined by an additional de Sitter vacuum surface. For spinning solitons G-lumps a phantom energy is not screened by horizons and influences their observational signatures, providing a source of information about the scale and properties of a phantom energy. Regular BH remnants and G-lumps can form graviatoms binding electrically charged particles. Their observational signature is the electromagnetic radiation with the frequencies depending on the energy scale of the interior de Sitter vacuum within the range available for observations. A nontrivial observational signature of all DM candidates with de Sitter interiors predicted by analysis of dynamical equations is the induced proton decay in an underground detector like IceCUBE, due to non-conservation of baryon and lepton numbers in their GUT scale false vacuum interiors.

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25

Ferraro, Rafael. "Untangling the Newman–Janis algorithm." General Relativity and Gravitation 46, no. 4 (March 25, 2014). http://dx.doi.org/10.1007/s10714-014-1705-3.

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26

Erbin, Harold. "Deciphering and generalizing Demiański–Janis–Newman algorithm." General Relativity and Gravitation 48, no. 5 (April 6, 2016). http://dx.doi.org/10.1007/s10714-016-2054-1.

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27

Erbin, Harold. "Janis–Newman algorithm: simplifications and gauge field transformation." General Relativity and Gravitation 47, no. 3 (February 11, 2015). http://dx.doi.org/10.1007/s10714-015-1860-1.

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28

Chou, Yu-Ching,. "Extension Rules of Newman–Janis Algorithm for Rotation Metrics in General Relativity." Physical Science International Journal, July 15, 2020, 1–14. http://dx.doi.org/10.9734/psij/2020/v24i630194.

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Aims: The aim of this study is to extend the formula of Newman–Janis algorithm (NJA) and introduce the rules of the complexifying seed metric. The extension of NJA can help determine more generalized axisymmetric solutions in general relativity.Methodology: We perform the extended NJA in two parts: the tensor structure and the seed metric function. Regarding the tensor structure, there are two prescriptions, the Newman–Penrose null tetrad and the Giampieri prescription. Both are mathematically equivalent; however, the latter is more concise. Regarding the seed metric function, we propose the extended rules of a complex transformation by r2/Σ and combine the mass, charge, and cosmologic constant into a polynomial function of r. Results: We obtain a family of axisymmetric exact solutions to Einstein’s field equations, including the Kerr metric, Kerr–Newman metric, rotating–de Sitter, rotating Hayward metric, Kerr–de Sitter metric and Kerr–Newman–de Sitter metric. All the above solutions are embedded in ellipsoid- symmetric spacetime, and the energy-momentum tensors of all the above metrics satisfy the energy conservation equations. Conclusion: The extension rules of the NJA in this research avoid ambiguity during complexifying the transformation and successfully generate a family of axisymmetric exact solutions to Einsteins field equations in general relativity, which deserves further study.

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29

Solanki, Divyesh N., Parth Bambhaniya, Dipanjan Dey, Pankaj S. Joshi, and Kamlesh N. Pathak. "Shadows and precession of orbits in rotating Janis–Newman–Winicour spacetime." European Physical Journal C 82, no. 1 (January 2022). http://dx.doi.org/10.1140/epjc/s10052-022-10045-1.

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AbstractIn this paper, we construct the rotating Janis–Newman–Winicour (JNW) naked singularity spacetime using Newman–Janis Algorithm (NJA). We analyse NJA with and without complexification methods and find that the energy conditions do satisfied when we skip the complexification step. We study the shadows cast by rotating JNW naked singularity and compare them with the shadows cast by the Kerr black hole. We find that the shadow of the rotating naked singularity can be distinguished from the shadow of the Kerr black hole. While we analyse the precession of timelike bound orbits in rotating JNW spacetime, we find that it can have a negative (or opposite) precession, which is not present in the Kerr black hole case. These novel signatures of the shadow and orbital precession in rotating JNW naked singularity spacetime could be important in the context of the recent observation of the shadow of the M87 galactic center and the stellar dynamics of ‘S-stars’ around Milkyway galactic center.

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Junior, Haroldo C. D. Lima, Luís C. B. Crispino, Pedro V. P. Cunha, and Carlos A. R. Herdeiro. "Spinning black holes with a separable Hamilton–Jacobi equation from a modified Newman–Janis algorithm." European Physical Journal C 80, no. 11 (November 2020). http://dx.doi.org/10.1140/epjc/s10052-020-08572-w.

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AbstractObtaining solutions of the Einstein field equations describing spinning compact bodies is typically challenging. The Newman–Janis algorithm provides a procedure to obtain rotating spacetimes from a static, spherically symmetric, seed metric. It is not guaranteed, however, that the resulting rotating spacetime solves the same field equations as the seed. Moreover, the former may not be circular, and thus expressible in Boyer–Lindquist-like coordinates. Amongst the variations of the original procedure, a modified Newman–Janis algorithm (MNJA) has been proposed that, by construction, originates a circular, spinning spacetime, expressible in Boyer–Lindquist-like coordinates. As a down side, the procedure introduces an ambiguity, that requires extra assumptions on the matter content of the model. In this paper we observe that the rotating spacetimes obtained through the MNJA always admit separability of the Hamilton–Jacobi equation for the case of null geodesics, in which case, moreover, the aforementioned ambiguity has no impact, since it amounts to an overall metric conformal factor. We also show that the Hamilton–Jacobi equation for light rays propagating in a plasma admits separability if the plasma frequency obeys a certain constraint. As an illustration, we compute the shadow and lensing of some spinning black holes obtained by the MNJA.

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31

Contreras, Ernesto, J. M. Ramirez–Velasquez, Ángel Rincón, Grigoris Panotopoulos, and Pedro Bargueño. "Black hole shadow of a rotating polytropic black hole by the Newman–Janis algorithm without complexification." European Physical Journal C 79, no. 9 (September 2019). http://dx.doi.org/10.1140/epjc/s10052-019-7309-z.

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Abstract In this work, starting from a spherically symmetric polytropic black hole, a rotating solution is obtained by following the Newman–Janis algorithm without complexification. Besides studying the horizon, the static conditions and causality issues of the rotating solution, we obtain and discuss the shape of its shadow. Some other physical features as the Hawking temperature and emission rate of the rotating polytropic black hole solution are also discussed.

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32

Broccoli, Matteo, and Adriano Viganò. "Electromagnetic self-force in curved spacetime: New insights from the Janis-Newman algorithm." Physical Review D 98, no. 8 (October 5, 2018). http://dx.doi.org/10.1103/physrevd.98.084007.

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33

Shaikh, Rajibul. "Black hole shadow in a general rotating spacetime obtained through Newman-Janis algorithm." Physical Review D 100, no. 2 (July 15, 2019). http://dx.doi.org/10.1103/physrevd.100.024028.

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34

Makukov, Maxim, and Eduard Mychelkin. "Rotation in vacuum and scalar background: are there alternatives to Newman-Janis algorithm?" International Journal of Modern Physics D, January 27, 2023. http://dx.doi.org/10.1142/s0218271823500232.

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35

Chen, Che-Yu. "On the possible spacetime structures of rotating loop quantum black holes." International Journal of Geometric Methods in Modern Physics, July 8, 2022. http://dx.doi.org/10.1142/s0219887822501766.

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To date, a mathematically consistent construction of effective rotating black hole models in the context of Loop Quantum Gravity (LQG) is still lacking. In this work, we start with the assumption that rotating LQG black hole metrics can be effectively obtained using Newman–Janis Algorithm. Then, based on a few extra fair assumptions on the seed metric functions, we make a conjecture on what a rotating LQG black hole would generically look like. Our general arguments and conclusions can be supported by some known specific examples in the literature.

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Rahim, Rehana, and Khalid Saifullah. "The charged CPR black hole." International Journal of Modern Physics D 31, no. 01 (October 30, 2021). http://dx.doi.org/10.1142/s0218271821501236.

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The non-Kerr black hole is an important metric to study the possible deviations from the Kerr black hole of general relativity. It has been constructed by applying the Newman–Janis algorithm on a deformed Schwarzschild black hole. This approach has been generalized to include two different deformation functions to obtain CPR black holes [V. Cardoso, P. Pani and J. Rico, Phys. Rev. D 89 (2014) 064007]. In this paper, we develop the charged analogue of this spacetime. The new metric is studied for the particle dynamics also.

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37

Chen, Che-Yu, and Pisin Chen. "Separability of the Klein-Gordon equation for rotating spacetimes obtained from Newman-Janis algorithm." Physical Review D 100, no. 10 (November 26, 2019). http://dx.doi.org/10.1103/physrevd.100.104054.

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38

Hansen, Devin, and Nicolás Yunes. "Applicability of the Newman-Janis algorithm to black hole solutions of modified gravity theories." Physical Review D 88, no. 10 (November 19, 2013). http://dx.doi.org/10.1103/physrevd.88.104020.

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39

Ali, Riasat, Rimsha Babar, Muhammad Asgher, and G. Mustafa. "Tunneling Analysis of Null Aether Black Hole Theory in the Background of Newman-Janis Algorithm." International Journal of Modern Physics A, July 27, 2022. http://dx.doi.org/10.1142/s0217751x22501342.

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40

Ali, Riasat, Rimsha Babar, Muhammad Asgher, and Xia Tie-Cheng. "Tunneling Analysis of Regular Black Holes with Cosmic Strings-Like Solution in Newman-Janis Algorithm." International Journal of Modern Physics A, June 3, 2022. http://dx.doi.org/10.1142/s0217751x22501081.

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41

Patel, Vishva, Divya Tahelyani, Ashok B. Joshi, Dipanjan Dey, and Pankaj S. Joshi. "Light trajectory and shadow shape in the rotating naked singularity." European Physical Journal C 82, no. 9 (September 7, 2022). http://dx.doi.org/10.1140/epjc/s10052-022-10638-w.

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AbstractIn this paper, we investigate the light trajectories and shadow properties in the rotating version of null naked singularity (NNS) spacetime which is derived using the Newman–Janis algorithm without complexification method. We discuss some of the geometrical properties and causal structure of Rotating Naked Singularity (RNS) spacetime. The gravitational lensing in a rotating naked singularity is analyzed, and the results are compared to those of a Kerr black hole. In the case of a Kerr black hole, the photon sphere exists for both prograde and retrograde photon orbits, whereas for RNS, the photon sphere exists only for retrograde photon orbits. As a result, the naked singularity projects an arc-shaped shadow that differs from the contour-shaped shadow cast by a Kerr black hole.

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42

Huang, Yang, and Zhoujian Cao. "Finite-distance gravitational deflection of massive particles by a rotating black hole in loop quantum gravity." European Physical Journal C 83, no. 1 (January 27, 2023). http://dx.doi.org/10.1140/epjc/s10052-023-11180-z.

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AbstractA rotating black hole in loop quantum gravity was constructed by Brahma, Chen, and Yeom based on a nonrotating counterpart using the revised Newman–Janis algorithm recently. For such spacetime, we investigate the weak gravitational deflection of massive particles to explore observational effects of the quantum correction. The purpose of this article is twofold. First, for Gibbons–Werner (GW) method, a geometric approach computing the deflection angle of particles in curved spacetimes, we refine its calculation and obtain a simplified formula. Second, by using GW method and our new formula, we work out the finite-distance weak deflection angle of massive particles for the rotating black hole in loop quantum gravity obtained by Brahma et al. An analysis to our result reveals the repulsive effect of the quantum correction to particles. What’s more, an observational constraint on the quantum parameter is obtained in solar system.

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43

Zubair, M., Muhammad Ali Raza, and Ghulam Abbas. "Optical features of rotating black hole with nonlinear electrodynamics." European Physical Journal C 82, no. 10 (October 27, 2022). http://dx.doi.org/10.1140/epjc/s10052-022-10925-6.

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AbstractIn this article, we considered the strong field approximation of nonlinear electrodynamics black hole and constructed its rotating counterpart by applying the modified Newman–Janis algorithm. The corresponding metric function in the strong field limit of the static black hole is identified in order to study the radius of photon sphere. However, the metric function for the rotating counterpart in the strong field limit is considered in order to study the horizon radius w.r.t spin parameter. We considered the Hamilton–Jacobi method to derive the geodesic equations for photon and constructed an orthonormal tetrad for deriving the equations for celestial coordinates in the observer’s sky. Shadows, distortions and energy emission rates are investigated and the results are compared for different values of nonlinear electrodynamics parameter, charge and spin. It is found that the presence of the nonlinear electrodynamics parameter affects the shape and size of the shadows and thus the distortion in the case of rotation. It is also found that the nonlinearity of electrodynamics diminishes the flatness in the shadow due to the effect of spin and other parameters.

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44

Zahid, Muhammad, Saeed Ullah Khan, Jingli Ren, and Javlon Rayimbaev. "Geodesics and shadow formed by a rotating Gauss–Bonnet black hole in AdS spacetime." International Journal of Modern Physics D, May 6, 2022. http://dx.doi.org/10.1142/s0218271822500584.

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The latest findings of static and spherically symmetric black hole solution give a potential platform to investigate the novel four-dimensional Einstein Gauss–Bonnet gravity. In order to obtain a rotating black hole solution, we first adopt the Newman Janis algorithm and study the structure of its horizons. To analyze the said black hole shadow, we move forward to compute expressions of the celestial coordinates using the geodesic equations. Furthermore, we provide a detailed analysis of the shadow size and its distortion parameter, adopting the Hioki and Maeda method, together with the applications of a supermassive black hole shadow in the center of nearby galaxy Messier 87 and obtained constraints on the relationships of spin and charge. From the obtained results, we demonstrate that both spin and coupling parameters of the black hole have a substantial influence on shadow structure. The increment in the values of these parameters diminishes the shadow radius. We also study the energy emission rate using the Hawking temperature. Furthermore, it is shown that whenever the collision of two electrically neutral test particles takes place in the vicinity of the black hole horizon, the Gauss–Bonnet black hole may serve as a particle accelerator with an infinitely large center of mass energy.

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45

Tang, Meirong, and Zhaoyi Xu. "The no-hair theorem and black hole shadows." Journal of High Energy Physics 2022, no. 12 (December 21, 2022). http://dx.doi.org/10.1007/jhep12(2022)125.

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Abstract The successful observation of M87 supermassive black hole by the Black Hole Event Horizon Telescope(EHT) provides a very good opportunity to study the theory of gravity. In this work, we obtain the exact solution for the short hair black hole (BH) in the rotation situation, and calculate in detail how hairs affect the BH shadow. For the exact solution part, using the Newman-Janis algorithm, we generalize the spherically symmetric short-hair black hole metric to the rotation case (space-time lie element (2.25)). For the BH shadow part, we study two hairy BH models. In model 1, the properties of scalar hair are determined by the parameters α0 and L (We re-obtained the results in reference [48] for the convenience of discussion in this work). In model 2, the scalar hair of the BH is short hair. In this model, the shape of the BH shadow is determined by scalar charge Qm and k. The main results are as follows: (1) In the case of rotational short-hair BH, the value range of parameter k is k > 1 (2.25), the range of short-hair charge value Qm is greatly reduced due to the introduction of the BH spin a. When $$ 0\leqslant {Q}_m\leqslant \frac{2}{3}\times {4}^{\frac{1}{3}} $$ 0 ⩽ Q m ⩽ 2 3 × 4 1 3 , the rotational short-hair BH has two event horizons at this time. When $$ {Q}_m>\frac{2}{3}\times {4}^{\frac{1}{3}} $$ Q m > 2 3 × 4 1 3 , the rotational short-hair BH has three unequal event horizons, so the space-time structure of the BH is significantly different from that of Kerr BH. (2) For model 1, the effect of scalar hair on the BH shadows corresponds to that of ε > 0 in reference [38, 48], but the specific changes of the shadows in model 1 are different. This is because the BH hair in reference [38] is considered as a perturbation to the BH, while the space-time metric of model 1 is accurate and does not have perturbation property. For model 2, that is, the change of the BH shadow caused by short hairs, the main change trend is consistent with that of ε < 0 in reference [38]. Because of the special structure of the short-hair BH, the specific changes of BH shadows are different. (3) the variation of Rs and δs with L and α0 is not a monotone function in model 1, but in model 2, it is. These results show that scalar hairs (model 1) have different effects on Kerr BH shadows than short hairs (model 2), so it is possible to distinguish the types and properties of these hairs if they are detected by EHT observations. (4) as for the effects of the hairs on energy emissivity, the main results in model 1 [48], different energy emissivity curves have intersection phenomenon, while in model 2 (short-hair BH), there is no similar intersection phenomenon. In general, various BH hairs have different effects on the shadows, such as non-monotonic properties and intersection phenomena mentioned in this work. Using these characteristics, it is possible to test the no-hair theorem in future EHT observations, so as to have a deeper understanding of the quantum effect of BHs. In future work, we will use numerical simulations to study the effects of various hairs on BHs and their observed properties.

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