Masoud Ghezelbash, Haryanto M. Siahaan
We find a new class of exact solutions in the Einstein-Maxwell theory by employing the Ernst magnetization process to the Kerr-Newman-Taub-NUT spacetimes. We study the solutions and find that they are regular everywhere. We also find the quasilocal conserved quantities for the spacetimes, the corresponding Smarr formula and the first law of thermodynamics.
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In this paper we study the symmetries of the dual Taub-NUT metrics. Generic and non-generic symmetries of dual Taub-NUT metrics are investigated. The existence of the Runge-Lenz type symmetry is analyzed for dual Taub-NUT metrics. We find that in some cases the symmetries of the dual metrics are the same with the symmetries of Taub-NUT metric.
We construct a global flat embedding structure of a Taub-NUT-AdS spacetime to yield a (6+5)-dimensional novel global embedding Minkowski spacetime. We also investigate Taub-NUT, Schwarzschild-AdS and Schwarzschild limits of the global embedding by exploiting parameter reduction scheme. In particular, we observe in the vanishing monopole strength limit of the Taub-NUT-AdS that the parameter reduction is not smoothly applicable to the Schwarzschild-AdS, due to the presence of imaginary roots of its lapse function associated with event horizon. Moreover, reductions from the Taub-NUT-AdS and Schwa…
We find an exact solution describing the spacetime outside a massive object with NUT parameter embedded in an external magnetic field. To get the solution, we employ the Ernst magnetization transformation to the Taub-NUT metric as the seed solution. The massless limit of this new solution is the Melvin-Taub-NUT spacetime. Some aspects in the magnetized Taub-NUT spacetime are investigated, such as the surface geometry, the existence of closed time like curve, and the electromagnetic properties.
On Taub-NUT spacetime, we investigate hydrodynamic properties of perfect fluid spiraling inward toward the spacetime along a conical surface. On the equatorial plane of the Taub-NUT spacetime, we derive radial equations of motion with effective potentials and the Euler equation for steady state axisymmetric fluid. Higher dimensional global embeddings are constructed inside and outside the event horizons of the Taub-NUT spacetime. We also study the effective potentials of particles on the Taub-NUT spacetime in terms of gravitational magnetic monopole strength of the source, total energy and ang…
The occurrence of chaos for test particles moving in a Taub-NUT spacetime with a dipolar halo perturbation is studied using Poincaré sections. We find that the NUT parameter (magnetic mass) attenuates the presence of chaos.
Symmetric conformal Killing tensors and (skew-symmetric) conformal Yano-Killing tensors for Euclidean Taub-NUT metric are given in explicit form. Relations between Yano and CYK tensors in terms of conformal rescaling are discussed.
We investigate a biaxial Bianchi IX model with positive cosmological constant, which is sometimes called the Lambda-Taub-NUT spacetime, whose exact solution is well known. The minisuperspace of biaxial Bianchi IX models admits two non-trivial Killing tensors that play an important role for deriving the Taub-NUT metric. We also give a brief discussion about the asymptotic behaviour of Bianchi IX models.
We present a novel solution describing magnetized spacetime outside a massive object with electric charge equipped with NUT parameter. To get the solution, we employ the Ernst magnetization to the Reissner-Nordstrom-Taub-NUT spacetime as the seed. After discussing some physical aspects of the spacetime, we show that the extremal entropy of a magnetized Reissner-Nordstrom-Taub-NUT black hole can be reproduced by using the Cardy formula.
In this paper, we revisit the possibilities of Bañados-Silk-West (BSW) effect in Kerr-Newman-Taub-NUT (KNTN) spacetime for two neutral particles moving over the equatorial plane and constant $θ$ in Boyer-Lindquist coordinate. Contrary to a previous study on this topic, we found that BSW effect for two particles confined to move over the equatorial plane is not possible. Numerical calculations shows that BSW effect in constant $θ$ geodesics is possible under certain circumstances.
In this paper, we consider a new vacuum solution of the Kaluza-Klien theory which resembles the Taub-NUT metric in five dimensions and we investigate its physical properties as projected into four dimensions. We show that the Taub-NUT Kaluza-Klein vacuum solution in five dimensions is a static magnetic monopole in four dimensions. We find that the four dimensional matter properties do not obey the equation of state of radiation and there is no event horizon.
We present a new solution in Einstein-Maxwell theory which can be considered as the magnetized version of Kerr-Taub-NUT solution. Some properties of the spacetime are discussed. We also compute the entropy of extremal black hole in the spacetime by using the Kerr/CFT correspondence approach.
In this paper, we investigate the center of mass energy of the collision for two neutral particles with different rest masses falling freely from rest at infinity in the background of a Kerr-Newman-Taub-NUT black hole. Further, we discuss the center of mass energy near the horizon(s) of an extremal and non-extremal Kerr-Newman-Taub-NUT black hole and show that an arbitrarily high center of mass energy is achievable under some restrictions. We will study the special case of the center of mass energy when the specific energy, specific angular momentum and Carter constant of both the particles ar…
We show that the study of hidden conformal symmetry that associates to the Kerr/CFT correspondence can also apply to the cosmological horizon in Kerr-Newman-Taub-NUT-de Sitter spacetime. This symmetry allows one to employ some two dimensional conformal field theory methods to understand the properties of the cosmological horizon. The entropy can be understood by using the Cardy formula, and the equation for scattering process in the near region has an agreement with the one obtained from a two point function in two dimensional conformal field theory. We also show that pair production can occur…
We have investigated the acceleration of the unbound high energy particles moving along the rotation axis in the Kerr-Taub-NUT spacetime, and then study the dependence of the repulsive effects on the NUT charge for the particles in the spacetime. Whether the repulsive effects with the NUT charge become stronger depends on the Carter constant, the position and velocity of the particles themselves. We also present numerically the changes of the observable velocity and acceleration with the NUT charge for the unbound particles in the Kerr-Taub-NUT spacetime.
We study causal geodesics in the equatorial plane of the extremal Kerr-Taub-NUT spacetime, focusing on the Innermost Stable Circular Orbit (ISCO),and compare its behaviour with extant results for the ISCO in the extremal Kerr spacetime. Calculation of the radii of the direct ISCO, its Kepler frequency, and rotational velocity show that the ISCO coincides with the horizon in the exactly extremal situation. We also study geodesics in the strong {\it non}-extremal limit, i.e., in the limit of vanishing Kerr parameter (i.e., for Taub-NUT and massless Taub-NUT spacetimes as special cases of this sp…
An exact expression derived in the literature for the rate of dragging of inertial frames (Lense-Thirring (LT) precession) in a general stationary spacetime, is reviewed. The exact LT precession frequencies for Kerr, Kerr-Taub-NUT and Taub-NUT spacetimes are explicitly derived. Remarkably, in the case of the zero angular momentum Taub-NUT spacetime, the frame-dragging effect is shown {\it not} to vanish, when considered for spinning test gyroscopes. The result becomes sharper for the case of vanishing ADM mass of that spacetime. We clarify how our results are consistent with claims in the rece…
We study a charged Taub-NUT spacetime solution in the DGP brane. We show that the Reissner-Nordstrom-Taub-NUT-de Sitter solution of Einstein-Maxwell gravity solves the corresponding equations of motion, where the cosmological constant is related to the cross-over scale in the DGP model. Following the approach by Teitelboim in discussing the thermodynamics of de Sitter spacetime and the proposal by Wu et al. for a conserved charge associated to the NUT parameter, we obtained the generalized Smarr mass formula and the first law of thermodynamics of the spacetime.
Taub-NUT-like Black Holes in Einstein-Bumblebee Gravity
本文在Einstein-Bumblebee引力中构造了非Ricci平坦的类Taub-NUT黑洞及类Taub-NUT-AdS黑洞，并利用Wald形式证实其热力学第一定律与Smarr关系均成立。
A class of charged-Taub-NUT-scalar metrics via Harison and Ehlers Transformations
本文通过Harrison和Ehlers变换构造了带电-Taub-NUT-标量度规的精确解，并研究了其引力透镜和准正则模等天体物理性质。
Charged Taub-NUT type Black Holes in Einstein-Weyl-Maxwell Theory
该研究在四维爱因斯坦-外尔-麦克斯韦理论中数值构建了新型带电Taub-NUT型黑洞解，探明了相关参数的影响，揭示其解分支数量与静态球对称黑洞的差异及与中性NUT解的连通性区别。
In this work we study the equatorial causal geodesics of the Taub-NUT (TN) space-time in comparison with \emph{mass-less} TN space-time. We emphasized both on the null circular geodesics and time-like circular geodesics. From the effective potential diagram of null and time-like geodesics, we differentiate the geodesics structure between TN spacetime and mass-less TN space-time. It has been shown that there is a key role of the NUT parameter to changes the shape of pattern of the potential well in the NUT spacetime in comparison with \emph{mass-less} NUT space-time. We compared the ISCO (inner…
We have studied electromagnetic line emissions from near-horizon region in the extremal Kerr-Taub-NUT black hole spacetime and then probe the effects of NUT charge on the electromagnetic line emissions. Due to the presence of the NUT charge, the equatorial plane is no more a symmetry plane of the KTN spacetime, which leads to that the dependence of electromagnetic line emission on the NUT charge for the observer in the Southern Hemisphere differs from that in the Northern one. Our result indicate that the electromagnetic line emission in the Kerr-Taub-NUT black hole case is brighter than that …
Parallel transport around closed circular orbits in the equatorial plane of the Taub-NUT spacetime is analyzed to reveal the effect of the gravitomagnetic monopole parameter on circular holonomy transformations. Investigating the boost/rotation decomposition of the connection 1-form matrix evaluated along these orbits, one finds a situation that reflects the behavior of the general orthogonally transitive stationary axisymmetric case and indeed along Killing trajectories in general.
Gravitational Faraday rotation of light propagation in the Kerr-Newman-Taub-NUT space-time
本文在弱偏转极限下研究 Kerr-Newman-Taub-NUT 时空中的引力法拉第效应，发现源和观测者远离黑洞时仍存在非零旋转角，其大小取决于黑洞自旋、质量、观测者角位置以及电荷和 NUT 电荷。
Stationary spherically symmetric gravity is equivalent to a nonlinear coset sigma model on SL(2,R)/SO(2) coupled to a gravitational remnant. Classically there are stationary solutions besides the static Schwarzschild metric labeled by the Schwarzschild mass $m$ and the Taub-NUT charge $l$. Imposing the SL(2,R) symmetry at the quantum level the Wheeler-DeWitt equation becomes related to the Casimir operator on the coset, which makes the system amenable to exact quantization.
In this paper, we show the additive separation of the Hamilton-Jacobi equation, present the 4-velocity of the test particles, and attempt to find the equatorial circular photon orbit (ECPO) in the Kerr-Sen-Taub-NUT (KSTN) solution of the low energy limit of heterotic string theory. In the process of trying to find the ECPO, we instead encounter a ring singularity that could be outside the horizon of the KSTN black hole.
We construct new solutions of the vacuum Einstein field equations in four dimensions via a solution generating method utilizing the SL(2,R) symmetry of the reduced Lagrangian. We apply the method to an accelerating version of the Zipoy-Voorhees solution and generate new solutions which we interpret to be the accelerating versions of the Zipoy-Voorhees generalisation of the Taub-NUT solution (with Lorentzian signature) and the Zipoy-Voorhees generalisation of the Eguchi-Hanson solitons (with Euclidean signature). As an intermediary in the solution-generating process we obtain charged versions o…
When we consider five-dimensional warped Taub-NUT/Bolt AdS black string with minimally coupled massive scalar field, we calculate entropy by using the brick wall method. It is found that they are proportional to being quadratically divergent in a cutoff parameter. In particular, we show that the entropy of warped Taub-NUT AdS black string holds for an area law in the bulk as well as on the brane. Furthermore, when the negative cosmological constant is treated as thermodynamic pressure, we calculate the thermodynamic quantities and investigate their extended thermodynamic properties. Interestin…
We present a novel solution obeying classical equation of motion in the low energy limit of heterotic string theory. The solution represents a rotating mass with electric charge and gravitomagnetic monopole moment. The corresponding conserved charges are discussed. We also study the test body circular equatorial motions in the spacetime.
We introduce a new class of inhomogeneous cosmological models as solutions to the Einstein-Maxwell equations in electrovacuum. The new models can be considered to be nonlinear perturbations, through an electromagnetic field, of the previously studied `smooth Gowdy-symmetric generalised Taub-NUT solutions' in vacuum. Utilising methods from soliton theory, we analyse the effects of the Maxwell field on global properties of the solutions. In particular, we show existence of regular Cauchy horizons, and we investigate special singular cases in which curvature singularities form.
We present a Kaluza-Klien vacuum solution which closely resembles the Taub-NUT magnetic monopole and we investigate its physical properties as viewed from four space-time dimensions. We show that the Taub-NUT Kaluza-Klein vacuum solution in five dimensions is a static magnetic monopole. We find that the four dimensional matter properties do not obey the equation of state of radiation and there is no event horizon. A comparison with the available magnetic monopole solutions and the issue of vanishing and negative mass are discussed.
First law of black hole thermodynamics and the weak cosmic censorship conjecture for Kerr-Newman Taub-NUT black holes
本研究构建了Kerr-Newman Taub-NUT黑洞自洽的热力学第一定律，并通过带电检验粒子与复标量场验证弱宇宙监督猜想，发现极端黑洞无法被摧毁，小NUT参数近极端黑洞可被带电粒子摧毁但不受复标量场影响。
Newman-Janis Algorithm from Taub-NUT Instantons
本文展示Kerr度规是自对偶与反自对偶Taub-NUT瞬间子的非线性叠加，推动Newman-Janis算法成为具有明确物理起源的Kerr度规推导方法。
An important aspect of General Relativity is to study properties of geodesics. A useful tool for describing geodesic behavior is the geodesic deviation equation. It allows to describe the tidal properties of gravitating objects through the curvature of spacetime. This article focuses on the study of the axially symmetric Taub-NUT metric. We study tidal effects in this metric using the geodesic deviation equation. Radial geodesics along the symmetry axis of spacetime are considered. We show that all spatial components of tidal forces always change sign under the event horizon. We find a solutio…
Rotating disks with nonzero radial pressure and finite radius are studied. The models are based in the Taub-NUT metric and constructed using the well-known ``displace, cut and reflect'' method. We find that the disks are made of perfect fluids with constant energy density and pressure. The energy density is negative, but the effective Newotnian density is possitive as the strong energy condition requires. We also find that the disks are not stable under radial perturbations and that there are regions of the disks where the particles move with superluminal velocities.
Shadows for Kerr-Sen-Taub-NUT black holes with Manko-Ruiz parameter
本文探究含Manko-Ruiz参数的Kerr-Sen-Taub-NUT时空，证明测试粒子哈密顿-雅可比方程可分离并推导黑洞阴影边界方程，揭示时空参数（含Manko-Ruiz参数）对阴影形状的影响，为该时空几何研究提供新见解。
Time evolution of Von Neumann entropy for a Kerr-Taub-NUT black hole
本文研究了Kerr-Taub-NUT黑洞蒸发发射标量粒子时的演化，发现辐射会增加角动量损失率并降低质量与NUT参数损失率，且其Von Neumann熵近似遵循Page曲线，高$β$值会加速蒸发过程。
We discuss the generalization of the NUT spacetime in General Relativity (GR) within the framework of the (dynamical) Einstein--Chern-Simons (ECS) theory with a massless scalar field. These configurations approach asymptotically the NUT spacetime and are characterized by the `electric' and `magnetic' mass parameters and a scalar `charge'. The solutions are found both analytically and numerically. The analytical approach is perturbative around the Einstein gravity background. Our results indicate that the ECS configurations share all basic properties of the NUT spacetime in GR. However, when co…
Scalarization of Taub-NUT Black Holes in Extended scalar-tensor-Gauss-Bonnet Theory
本研究在扩展标量-张量-高斯-博内理论框架下探究Taub-NUT黑洞的标量化，通过探测分析与打靶法数值构建出两支平滑相连的带毛黑洞，发现其熵高于无标量黑洞，且正质量参数下分岔点处熵恒定，并推测存在最大熵界。
We consider higher dimensional topological Taub-NUT/Bolt-AdS solutions where a cosmological constant is treated as a pressure. The thermodynamic quantities of these solutions are explicitly calculated. Furthermore, we find these thermodynamic quantities satisfy the Clapeyron equation. In particular, a new thermodynamically stable region for the NUT solution is found by studying the Gibbs free energy. Intriguingly, we also find that like the AdS black hole case, the G-T diagram of the Bolt solution has two branches which are joined at a minimum temperature. The Bolt solution with the large radi…
Membrane method is used to compute the entropy of the NUT-Kerr-Newman black holes. It is found that even though the Euler characteristic is greater than two, the Bekenstein-Hawking area law is still satisfied. The formula $S=χA/8$ relating the entropy and the Euler characteristic becomes inapplicable for non-extreme four dimensional NUT-Kerr-Newman black holes.
Repetitive Penrose Process in Kerr-Taub-NUT black hole spacetime
研究Kerr-Taub-NUT黑洞中的重复Penrose过程，分析引力磁电荷对事件视界和能层半径的影响，以及通过守恒定律和迭代停止条件计算可提取能量的变化。
Geometric phase in Taub-NUT spacetime
在Taub-NUT时空中，通过η表示构造哈密顿量，发现几何相位同时包含Aharonov-Bohm效应和Pancharatnam-Berry相位，而静态时空中仅后者出现，并提出了针对原初黑洞的测量方案。
Scalarization of charged Taub-NUT black hole and the entropy bound
研究带电Taub-NUT黑洞在爱因斯坦-麦克斯韦-标量-高斯-博内引力中的自发标量化，发现其在特定参数范围内不稳定，导致新的带发带电Taub-NUT黑洞分支出现，分析其标量电荷、温度和熵特性。
We use the harmonic space technique to construct explicitly a quaternionic extension of the Taub-NUT metric. It depends on two parameters, the first being the Taub-NUT `mass' and the second one the cosmological constant.
Second order variations and the overspinning problem in Kerr-Taub-NUT spacetime
本文通过评估 Sorce-Wald 条件并计算面积的二阶变化，证明二阶变化能驱使 Kerr-Taub-NUT 黑洞偏离极端状态，从而避免超旋并保留事件视界，符合宇宙审查猜想。
The Kerr-Taub-NUT spacetime in the Kaluza-Klein theory represents a localized stationary and axisymmetric object in four dimensions from the Kaluza-Klein viewpoint. That is, it harbors companion electromagnetic and dilaton fields, thereby showing up the signature of the extra fifth dimension. We explore the separability structure of this spacetime and show that the Hamilton-Jacobi equation for geodesics admits the complete separation of variables only for massless geodesics. This implies the existence of the hidden symmetries in the spacetime, which are generated by the conformal Killing tenso…
The scalar angular Teukolsky equation and its solution for the Taub-NUT spacetime
研究Taub-NUT时空中的标量角Teukolsky方程及其解，推导特征值并解析求解波光学散射问题。
We study the behavior of phase transitions for the four-dimensional charged Taub-NUT-AdS spacetime with the Newman-Unti-Tamburino (NUT) parameter interpreted as the thermodynamic multihair in the extended thermodynamic phase space, and mainly focus on the effects of the NUT parameter on the phase transitions. We find that there is an upper bound on the value of the NUT parameter beyond which the corresponding physical inflection point or critical point will not exist, and the thermodynamic trihair interpretation of the NUT parameter would admit a little larger upper bound than the thermodynami…
The interpretation of a family of electrovacuum stationary Taub-NUT-type fields in terms of finite charged perfect fluid disks is presented. The interpretation is mades by means of an "inverse problem" approach used to obtain disk sources of known solutions of the Einstein or Einstein-Maxwell equations. The diagonalization of the energy-momentum tensor of the disks is facilitated in this case by the fact that it can be written as an upper right triangular matrix. We find that the inclusion of electromagnetic fields changes significatively the different material properties of the disks and so w…
The generalized Killing equations and the symmetries of Taub-NUT spinning space are investigated. For spinless particles the Runge-Lenz vector defines a constant of motion directly, whereas for spinning particles it now requires a non-trivial contribution from spin. The generalized Runge-Lenz vector for spinning Taub-NUT space is completely evaluated.
New Taub-NUT Black Holes with Massive Spin-2 Hair
本文在含二次曲率不变量的爱因斯坦引力中，通过分析Taub-NUT背景的不稳定Lichnerowicz模式确定参数区域，并数值构造出从Ricci-flat解分岔的具有大质量自旋-2毛发的新Taub-NUT黑洞，发现在适当温度下可共存三个黑洞。
We construct novel solutions to the effective Einstein equation with four dimensional cosmological constant on a 3-brane in Randall-Sundrum II scenario. The charged solution is obtained by assuming the existence of localized Maxwell fields on the 3-brane. Timelike and null circular geodesics in the neutral rotating braneworld spacetime with NUT parameter are discussed, and we find that such geodesics cannot occur on the equatorial plane. On non-equatorial planes, timelike circular geodesics can occur for the negative tidal charge, but we cannot find numerical results to support the existence o…
The geodesic motion of pseudo-classical spinning particles in Euclidean Taub-NUT space is analysed. The constants of motion are expressed in terms of Killing-Yano tensors. Some previous results from the literature are corrected.
We present investigations of a class of solutions of Einstein's field equations close to the family of lambda-Taub-NUT spacetimes. The studies are done using a numerical code introduced by the author elsewhere. One of the main technical complication is due to the S3-topology of the Cauchy surfaces. Complementing these numerical results with heuristic arguments, we are able to yield some first insights into the strong cosmic censorship issue and the conjectures by Belinskii, Khalatnikov, and Lifschitz in this class of spacetimes. In particular, the current investigations suggest that strong cos…
We study aspects of the extended gravitational thermodynamics for the Taub-NUT and Taub-Bolt geometries in four dimensional locally anti-de Sitter spacetime, where the cosmological constant is treated as a dynamical pressure. Attention is paid to the phase structure in the (p,T) plane, which has a line of first order phase transitions extending from the origin. We argue for a dynamical interpretation of the unstable physics in the negative specific heat region. A deformation corresponding to a dyonic Taub-NUT/Bolt system is also explored, and the effect of the deformation on the phase diagram …
I show that there are no SU(2)-invariant (time-dependent) tensorial perturbations of Lorentzian Taub-NUT space. It follows that the spacetime is unstable at the linear level against generic perturbations. I speculate that this fact is responsible for so far unsuccessful attempts to define a sensible thermodynamics for NUT-charged spacetimes.
We present further analysis of an anisotropic, non-singular early universe model that leads to the viable cosmology presented in Dechant et al (arXiv:0809.4335). Although this model (the DLH model) contains scalar field matter, it is reminiscent of the Taub-NUT vacuum solution in that it has biaxial Bianchi IX geometry and its evolution exhibits a dimensionality reduction at a quasi-regular singularity that one can identify with the big-bang. We show that the DLH and Taub-NUT metrics are related by a coordinate transformation, in which the DLH time coordinate plays the role of conformal time f…
Exact Analytical Taub-NUT like Solution in f(T) Gravity
本文在 f(T) 引力框架下构造精确解析的类 Taub-NUT 解，分析其物理性质，并与 Einstein 引力对应解比较。
A class of generalized Taub-NUT gravitational instantons is reported in five - dimensional Einstein gravity coupled to a non-linear sigma model. The geodesic dynamics of a spinless particle of unit mass on these static gravitational instantons is studied. This is accomplished by finding a generalized Runge-Lenz vector. Unlike the Kepler problem, or, the dynamics of a spinless particle on the familiar Taub-NUT gravitational instantons, the orbits are not conic sections.
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