A5060530967- Black Holes and Theoretical Physics
- Cosmology and Gravitation Theories
- Noncommutative and Quantum Gravity Theories
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Semiconductor Quantum Structures and Devices
- Relativity and Gravitational Theory
- Quantum Electrodynamics and Casimir Effect
- Galaxies: Formation, Evolution, Phenomena
- Advanced Mathematical Physics Problems
- Advanced Differential Geometry Research
- GaN-based semiconductor devices and materials
- Chalcogenide Semiconductor Thin Films
- Semiconductor Lasers and Optical Devices
- Nanowire Synthesis and Applications
- Optical properties and cooling technologies in crystalline materials
- Nonlinear Dynamics and Pattern Formation
- Geophysics and Gravity Measurements
- Particle physics theoretical and experimental studies
- Photonic and Optical Devices
- Solid State Laser Technologies
- Semiconductor materials and devices
- Space Science and Extraterrestrial Life
- Solidification and crystal growth phenomena
- Quantum optics and atomic interactions
Kindai University
2016-2025
High Energy Accelerator Research Organization
2008-2012
Institute of Particle and Nuclear Studies
2008-2010
Perimeter Institute
2008-2009
University of Chicago
2002-2007
Kansai University
2007
Fermi National Accelerator Laboratory
2002-2006
University of Cambridge
2001-2005
Panasonic (Japan)
1999-2003
Kyoto University
1999-2003
Generic extensions of the standard model predict existence ultralight bosonic degrees freedom. Several ongoing experiments are aimed at detecting these particles or constraining their mass range. Here we show that massive vector fields around rotating black holes can give rise to a strong superradiant instability, which extracts angular momentum from hole. The observation supermassive spinning imposes limits on this mechanism. We current black-hole spin estimates provide tightest upper...
Light bosonic degrees of freedom have become a serious candidate for dark matter, which seems to pervade our entire Universe. The evolution these fields around curved spacetimes is poorly understood but expected display interesting effects. In particular, the interaction light with supermassive black holes, key players in most galaxies, could provide colorful examples superradiance and nonlinear bosenovalike collapse. turn, observation spinning holes impose stringent bounds on mass putative...
We show that in four or more spacetime dimensions, the Einstein equations for gravitational perturbations of maximally symmetric vacuum black holes can be reduced to a single second-order wave equation two-dimensional static spacetime, irrespective mode perturbations. Our starting point is gauge-invariant formalism an arbitrary number dimensions developed by present authors, and variable final master given simple combination variables this formalism. formulation applies case non-vanishing as...
In the present paper gauge-invariant formalism is developed for perturbations of brane world model in which our universe realized as a boundary higher dimensional spacetime. For background bulk spacetime $(n+m)$ and has spatial symmetry corresponding to isometry group an n-dimensional maximally symmetric space, equations are derived space-time. Further, case $m=2$ invariant under unperturbed background, relations between variables describing those from Israel's junction condition assumption...
In recent years, there has been considerable interest in theories formulated anti-de Sitter (AdS) spacetime. However, AdS spacetime fails to be globally hyperbolic, so a classical field satisfying hyperbolic wave equation on need not have well-defined dynamics. Nevertheless, is static, the possible rules of dynamics for linear are constrained by our previous general analysis—given paper II—where it was shown that choices correspond positive, self-adjoint extensions certain differential...
We extend the formulation for perturbations of maximally symmetric black holes in higher dimensions developed by present authors a previous paper to charged hole background whose horizon is described an Einstein manifold. For holes, electromagnetic fields are coupled vector and scalar modes metric non-trivially. show that taking appropriate combinations gauge-invariant variables these perturbations, perturbation equations Einstein-Maxwell system reduced two decoupled second-order wave...
We investigate the classical stability of higher-dimensional Schwarzschild black holes against linear perturbations, in framework a gauge-invariant formalism for gravitational perturbations maximally symmetric holes, recently developed by authors. The are classified into tensor, vector, and scalar-type modes according to their tensorial behaviour on spherical section background metric, where last two correspond respectively axial- polar-mode four-dimensional situation. show that, each mode...
We discuss a general method to study linear perturbations of slowly rotating black holes which is valid for any perturbation field, and particularly advantageous when the field equations are not separable. As an illustration we investigate massive vector (Proca) in Kerr metric, do appear be separable standard Teukolsky formalism. Working perturbative scheme, two important effects induced by rotation: Zeeman-like shift nonaxisymmetric quasinormal modes bound states with different azimuthal...
We derive hamiltionian generators of asymptotic symmetries for general relativity with AdS boundary conditions using the ``covariant phase space'' method Wald et al. then compare our results other definitions that have been proposed in literature. find definition agrees by Ashtekar al, spinor definition, and background dependent Henneaux Teitelboim. Our disagrees one obtained from ``counterterm subtraction method,'' but difference is found to consist only a ``constant offset'' determined...
No. It is simply not plausible that cosmic acceleration could arise within the context of general relativity from a back-reaction effect inhomogeneities in our universe, without presence cosmological constant or ``dark energy.'' We point out universe appears to be described very accurately on all scales by Newtonianly perturbed FLRW metric. (This assertion entirely consistent with fact we commonly encounter $\delta \rho/\rho > 10^{30}$.) If metric, then dynamics negligible. not, it burden an...
We review uniqueness theorems as well other general results about higher dimensional black hole spacetimes. This includes in particular the topology of spacetimes, their symmetries (rigidity theorem), and classification supersymmetric holes. outline basic ideas underlying proofs these statements, we also indicate ways to generalize some more contexts, such complicated theories.
We consider the memory effect in even dimensional spacetimes of dimension d ≥ 4 arising from a burst gravitational radiation.When = 4, natural frames stationary eras before and after differ by composition boost supertranslation, this supertranslation characterizes "memory effect," i.e., permanent displacement test particles near infinity produced radiation burst.However, we show that when > corresponding vanish.Consequently, it is to impose stronger asymptotic conditions at null reduce...
We further explore the counterterm subtraction definition of charges (e.g., energy) for classical gravitating theories in spacetimes relevance to gauge/gravity dualities; i.e., asymptotically anti-de Sitter (AdS) spaces and their kin. In particular, we show general that defined via method generate desired asymptotic symmetries. As a result, they can differ from any other such charges, as those by bulk spacetime-covariant techniques, only function auxiliary nondynamical structures choice...
To probe naked spacetime singularities with waves rather than particles we study the well posedness of initial value problems for test scalar fields finite energy so that natural function space data is Sobolev space. In case static and conformally spacetimes examine essential self-adjointness time translation operator in wave equation defined Hilbert For some classical singularity becomes regular if probed while stronger remain singular. If when may say ``globally hyperbolic.''
We give a general geometric definition of asymptotic flatness at null infinity in $d$-dimensional relativity ($d$ even) within the framework conformal infinity. Our is arrived via an analysis linear perturbations near and shown to be stable under such perturbations. The detailed fall off properties perturbations, as well gauge conditions that need imposed make regular infinity, are qualitatively different higher dimensions; particular, decay rate radiating solution differs from static...
In this chapter we consider perturbations and stability of higher dimensional black holes focusing on the static background case. We first review a gauge-invariant formalism for linear in fairly generic class (m+n)-dimensional spacetimes with warped product metric, including hole geometry. classify such into three types, tensor, vector scalar-type, according to their tensorial behavior n-dimensional part spacetime, each type perturbations, introduce set manifestly gauge invariant variables....
Physic in curved spacetime describes a multitude of phenomena, ranging from astrophysics to high-energy physics (HEP). The last few years have witnessed further progress on several fronts, including the accurate numerical evolution gravitational field equations, which now allows highly nonlinear phenomena be tamed. Numerical relativity simulations, originally developed understand strong-field astrophysical processes, could prove extremely useful HEP processes such as trans-Planckian...
We study the linear stability of asymptotically anti-de Sitter black holes in general relativity spacetime dimension . Our approach is an adaptation framework Hollands and Wald, which gives a criterion terms sign canonical energy, The was originally formulated for static or stationary axisymmetric flat case, analysis that case applies only to perturbations. However, requires hole have single Killing field normal horizon there are no restrictions on perturbations (apart from smoothness...
A bstract In the framework of AdS/CFT duality, we consider semiclassical problem in general quadratic theory gravity. We construct asymptotically global AdS and hyperbolic (topological) black hole solutions with non-trivial quantum hair 4 5-dimensions by perturbing maximally symmetric to holographic equations. find that under certain conditions, our solution holes can be dynamically unstable against linear perturbations. this context, also study thermodynamic instability hairy 5-dimensional...
It was previously shown by one of us that in any static, non-globally-hyperbolic, spacetime, it is always possible to define a sensible dynamics for Klein–Gordon scalar field. The prescription proposed doing so involved viewing the spatial derivative part, A, wave operator as an on certain L2 Hilbert space and then defining positive, self-adjoint taking Friedrichs extension (or other positive extension) A. However, this analysis left open possibility there could be inequivalent prescriptions...
We show a uniqueness theorem for charged rotating black holes in the bosonic sector of five-dimensional minimal supergravity. More precisely, under assumptions existence two commuting axial isometries and spherical topology horizon cross sections, we prove that an asymptotically flat, stationary hole with finite temperature Einstein-Maxwell-Chern-Simons theory is uniquely characterized by mass, charge, independent angular momenta therefore described Chong-Cveti\ifmmode \check{c}\else...
We explicitly calculate the gravitational wave memory effect for classical point particle sources in linearized gravity off of an even dimensional Minkowski background. show that there is no $d>4$ dimensions, agreement with general analysis Hollands, Ishibashi, and Wald (2016).
We consider quantum effects of gravitational and electromagnetic fields in spherically symmetric black hole spacetimes the asymptotic safety scenario. Introducing both running couplings from renormalization group equations applying a physically sensible scale identification scheme based on Kretschmann scalar, we construct mechanically corrected, or improved Reissner-Nordstrom metric. study global structure geometry show, particular, that central singularity is resolved, being generally...