A property well known as the first law of black hole is a relation among infinitesimal variations of parameters of stationary black holes. We consider a dynamical version of the first law, which may be called the first law of black hole dynamics. The first law of black hole dynamics is derived without assuming any symmetry or any asymptotic conditions. In the derivation, a definition of dynamic...

We describe an explicit in time, finite-difference code designed to simulate black holes by using the excision method. The code is based upon the harmonic formulation of the Einstein equations and incorporates several features regarding the well-posedness and numerical stability of the initial-boundary problem for the quasilinear wave equation. After a discussion of the equations solved and of ...

It is shown that the event horizon of 4D black hole or ds2 = 0 surfaces of multidimensional wormhole-like solutions reduce the amount of information necessary for determining the whole spacetime and hence satisfy the Holography principle. This leads to the fact that by matching two metrics on a ds2 = 0 surface (an event horizon for 4D black holes) we can match only the metric components but not...

I describe the general mathematical construction and physical picture of topological black holes, which are black holes whose event horizons are surfaces of non-trivial topology. The construction is carried out in an arbitrary number of dimensions, and includes all known special cases which have appeared before in the literature. I describe the basic features of massive charged topological blac...

Roughly a dozen X-ray binaries are presently known in which the compact accreting primary stars are too massive to be neutron stars. These primaries are identified as black holes, though there is as yet no definite proof that any of the candidate black holes actually possesses an event horizon. We discuss how Type I X-ray bursts may be used to verify the presence of the event horizon in these o...

The traditional description of black holes in terms of event horizons is inadequate for many physical applications, especially when studying black holes in non-stationary spacetimes. In these cases, it is often more useful to use the quasi-local notions of trapped and marginally trapped surfaces, which lead naturally to the framework of trapping, isolated and dynamical horizons. This framework ...

Biomimetics often provides efficient ways to create a product incorporating novel properties. Here we present the replication of the Pieris rapae butterfly optical structure. This butterfly has white wings with black spots. The white coloration is produced by light scattering on pterin beads ranging from 100 to 500 nm whereas black spots correspond to areas without pterin beads, thus revealing ...

The aim of this study was to investigate the effects of breading materials and two different frying oils on the fat up-take in the fish fillets during frying process. Breaded and non-breaded black pomfret (Parastromateus niger) fillets were fried in sunflower oil and palm olein. Fat content by Soxhelet method and scanning electron microscopy (SEM) was studied. Results from Soxhelet method showe...

black humor plays a crucial role in fulfilling langston hughes's anti-racist purposes as an integral notionin his poetry. accordingly, translation(s) of his poetry are to benefit from the same indexes onthe basis of equivalent effect principle. on this account, 33 black-humor-rich poems of hughes, translatedby ahmad shamloo, yaghma golruee and hassan fayyad, were selected to be analyzed co...

There are many observational evidences for the detection of compact objects with masses significantly larger (in galactic cases) or much larger (in extragalactic cases) than the upper limits of masses of cold Neutron Stars. Such compact objects are commonly interpreted as Black Holes (BHs). However, we point out that while such Black Hole Candidates (BHCs) must be similar to BHs in many respect...