The observation of the shadow supermassive black hole M87$^{*}$ by Event Horizon Telescope (EHT) is sensitive to spacetime geometry near circular photon orbit and beyond, it thus has potential test general relativity in strong field regime. Obstacles this program, however, include degeneracies between putative deviations from both description accretion flow uncertainties on "calibration paramet...

Naked singularities in the gravitational backgrounds dual to gauge theories can be hidden behind the black hole horizon. We present an exact black hole solution in the Klebanov-Tseytlin geometry [hepth/0002159]. Our solution realizes Maldacena dual of the finite temperatureN = 1 duality cascade of [hep-th/0007191] above the temperature of the chiral symmetry breaking. We compare the BekensteinH...

We present the spacetime of a five-dimensional static black hole within EinsteinMaxwell theory. The solution represents a Kaluza-Klein black hole, whereby the solution is wholly five-dimensional near the horizon, but becomes effectively fourdimensional (with a compact fifth dimension) at the spatial infinity. The black-hole is electrically charged and so has two horizons, with a horizon geometr...

The exact black hole solution of 2D closed string theory has, as any other maximally extended Schwarzschild-like geometry, two asymptotically flat spacetime domains. One can get rid of the second domain by gauging the discrete symmetry on the SL(2,R)/U(1) coset that interchanges the two asymptotic domains and preserves the Kruskal time orientation everywhere in the Kruskal plane. Here it is sho...

We prove that, in the non-extreme Kerr-Newman black hole geometry, the Dirac equation has no normalizable, time-periodic solutions. A key tool is Chandrasekhar’s separation of the Dirac equation in this geometry. A similar non-existence theorem is established in a more general class of stationary, axisymmetric metrics in which the Dirac equation is known to be separable. These results indicate ...

First-principles calculations show that the electronic structure of graphene on SiO2 strongly depends on the surface polarity and interface geometry. Surface dangling bonds mediate the coupling to graphene and can induce hole or electron doping via charge transfer even in the absence of extrinsic impurities in substrate. In an interface geometry where graphene is weakly bonded to an O-polar sur...

We use ab initio density functional calculations to study the effect of electron and hole doping on the equilibrium geometry and electronic structure of C, Si, and S monatomic wires. Independent of doping, all these nanowires are found to be metallic. In absence of doping, C wires are straight, whereas Si and S wires display a zigzag structure. Besides two preferred bond angles of 60° and 120° ...

The kinematic evolution of axisymmetric magnetic and electric fields is investigated numerically in Kerr geometry for a simplified Keplerian disk near a rotating black hole. In the cases investigated it is found that a magnetic field cannot be sustained against ohmic diffusion. In flat space this result is known as Cowling’s antidynamo theorem. No support is found for the possibility that the g...

Using the classical Hamiltonian framework of [1] as the point of departure, we carry out a non-perturbative quantization of the sector of general relativity, coupled to matter, admitting non-rotating isolated horizons as inner boundaries. The emphasis is on the quantum geometry of the horizon. Polymer excitations of the bulk quantum geometry pierce the horizon endowing it with area. The intrins...