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The different methods of determination of black holes (BHs) masses are presented for three classes of BHs observed in the Universe: stellar mass BHs, intermediate mass BHs (IMBHs) and supermassive BHs (SBHs). The results of these determinations are briefly reviewed: stellar mass BHs are found in the range of about 3 to about 20 solar masses, IMBHs in the range of a few hundreds to a few tens of thousands solar masses (the determinations are much less precise for these objects) and SBHs in the range of about 3x10^5 to about 6x10^10 solar masses.
Reverberation mapping methods have been used to measure masses in about three dozen AGNs. The consistency of the virial masses computed from line widths and time delays, the relationship between black hole mass and host-galaxy stellar bulge velocity
It is well established that between 380000 and 1 billion years after the Big Bang the Inter Galactic Medium (IGM) underwent a phase transformation from cold and fully neutral to warm (~10^4 K) and ionized. Whether this phase transformation was fully
Ernsts solution generating technique is adapted to Einstein-Maxwell theory conformally (and minimally) coupled to a scalar field. This integrable system enjoys a SU(2,1) symmetry which enables one to move, by Kinnersley transformations, though the ax
We investigate the spontaneous creation of primordial black holes in a lower-dimensional expanding early universe. We use the no-boundary proposal to construct instanton solutions for both the background and a black hole nucleated inside this backgro
We track the evolution of entropy and black holes in a cyclic universe that undergoes repeated intervals of expansion followed by slow contraction and a smooth (non-singular) bounce. In this kind of cyclic scenario, there is no big crunch and no chao