The entropy-area spectrum of a black hole has been a long-standing and unsolved problem. Based on a recent methodology introduced by two of the authors, for the black hole radiation (Hawking effect) as tunneling effect, we obtain the entropy spectrum of a black hole. In Einstein’s gravity, we show that both entropy and area spectrum are evenly spaced. But in more general theories (like Einstein...

The transmission of light through a subwavelength hole drilled in a metallic thin .lm is calculated by numerically solving Maxwell's equations both for a simple hole and for a hole with additional structure. A maximum in the transmission cross section is observed for hole diameters of the order of but smaller than the wavelength. Transmission cross sections well above the hole area are shown to...

A “clean” black hole is a black hole in vacuum such as the Schwarzschild black hole. However in real physical systems, there are matter fields around a black hole. Such a black hole is called a “dirty black hole”. In this paper, the effect of matter fields on the black hole and the greybody factor is investigated. The results show that matter fields make a black hole smaller. They can increase ...

this study is focused on investigating the parameters of laser percussion drilling process of nickel-base super alloy inconel 718 with thickness of 1 mm. fiber laser with the power of 500 watts was used as the laser source. laser pulse frequency, duty cycle, laser power, focal point position, were assumed as the laser drilling process variables. the hole geometry features, i.e. entrance hole di...

The computation of gravitational radiation generated by the coalescence of inspiralling binary black holes is nowdays one of the main goals of numerical relativity. Perturbation theory has emerged as an ubiquitous tool for all those dynamical evolutions where the two black holes start close enough to each other, to be treated as single distorted black hole (close limit approximation), providing...

This is the second of a series of papers investigating the oscillation properties of relativistic, non-selfgravitating tori orbiting around black holes. Extending the work done in a Schwarzschild background, we here consider the axisymmetric oscillations of vertically integrated tori in a Kerr spacetime. The tori are modeled with a number of different non-Keplerian distributions of specific ang...

The standard approach to initial data for both analytic and numerical computations of black hole collisions has been to use conformally-flat initial geometry. Among other advantages, this choice allows the simple superposition of holes with arbitrary mass, location and spin. The conformally flat restriction, however, is inappropriate to the study of Kerr holes, for which the standard constant-t...

Was the black hole in XTE J1118+480 ejected from a globular cluster or kicked away from the galactic disk? 1. The intriguing origin of the kinematic of XTE J1118 + 480 Strong dynamical evidence now exists for 17 black holes (BHs) in X-ray novae but only a few have been observed away from the galactic plane (White & van Paradijs 1996). XTE J1118 + 480 is a high galactic latitude (b = 62.3) BH X-...

A unified approach to regular interiors of black holes with smooth matter distributions in the core region is given. The approach is based on a class of Kerr-Schild metrics representing minimal deformations of the Kerr-Newman solution, and allows us to give a common treatment for (charged and uncharged) rotating and nonrotating black holes. It is shown that the requirement of smoothness of the ...

We discuss the features that mark the Flat Spectrum Radio Quasars from the BL Lacertae objects. We propose that FSRQs exceeding L ∼ 10 46 erg s −1 are powered by black hole accreting at rates ˙ m ∼ 1 ÷ 10; their power is dominated by the disk components, thermal and BZ. Instead, sources accreting at rates ˙ m ∼ 10 −2 ÷ 10 −3 radiate in the BL Lac mode; here the power is mainly non-thermal, and ...