We review current theoretical understanding of the spectral properties (low and high states, transition of states, quasi-periodic oscillations etc.) of the low mass as well as supermassive black hole candidates.

Quasi-periodic oscillations (QPOs) have been discovered in the X-ray emission of many neutron stars and black holes. The QPOs with frequencies ∼> 300 Hz are thought to be produced near the surfaces of neutron stars and the event horizons of black holes. I first summarize some of the most important properties of the QPOs seen in neutron star and black hole systems. I then review some of the mode...

We classify all spherically symmetric dust solutions of Einstein’s equations which are self-similar in the sense that all dimensionless variables depend only upon z ≡ r/t. We show that the equations can be reduced to a special case of the general perfect fluid models with equation of state p = αμ. The most general dust solution can be written down explicitly and is described by two parameters. ...

The early growth stage and growth evolution to a unique gold (Au) honeycomb nano-network on Si(111)7×7 at room temperature have been studied by direct filled-state and empty-state imaging by scanning tunneling microscopy (STM). The gold honeycomb structure is made up of six triangular gold clusters around the corner hole interconnected to one another in the dimer rows of the Si(111)7×7 substrate.

We study the class of endlessly single-mode all-silica photonic crystal fibers with a triangular air-hole cladding. We consider the sensibility to longitudinal nonuniformities and the consequences and limitations for realizing low-loss large-mode area photonic crystal fibers. We also discuss the dominating scattering mechanism and experimentally we confirm that both macro and microbending can b...

In this contribution I review recent work that goes beyond our model for the Low-Frequency Quasi-Periodic Oscillation of microquasars, based on the Accretion-Ejection Instability. I show that similar instabilities, which can be viewed as strongly unstable versions of the diskoseismologic modes, provide explanations for both the High-Frequency QPO and for the quasi-periodicity observed durng the...

We investigate a novel symmetry in dualities of Wu’s equation: wg(1+w)1−g = eβ( −μ) for a degenerate g-on gas with fractional exclusion statistics of g, where β = 1/kBT , the energy, and μ the chemical potential of the system. We find that the particle–hole duality between g and 1/g and the supersymmetric duality between g and 1 − g form a novel quasi-modular group of order six for Wu’s equatio...

By work of Farinati, Solberg, and Taillefer, it is known that the Hopf algebra cohomology a quasi-triangular algebra, as graded Lie under Gerstenhaber bracket, abelian. Motivated by question whether this holds for nonquasi-triangular algebras, we show brackets on can be expressed via an arbitrary projective resolution using Volkov's homotopy liftings generalized to some exact monoidal categorie...

We present the first results from fully general relativistic numerical studies of thick-disk accretion onto a rapidly-rotating (Kerr) black hole with a spin axis that is tilted (not aligned) with the angular momentum vector of the disk. We initialize the problem with the solution for an aligned, constant angular momentum, accreting thick disk around a black hole with spin a/M = J/M = +0.9 (prog...

This paper aims at optimizing the parameters involved in stress analysis of perforated plates, in order to achieve the least amount of stress around the square-shaped holes located in a finite isotropic plate using metaheuristic optimization algorithms. Metaheuristics may be classified into three main classes: evolutionary, physics-based, and swarm intelligence algorithms. This research uses Ge...