Talk detail

Participant	Zakharov, Alexander
Institution	Institute of Theoretical and Experimental Physics - B. Cheremushkinskaya, 25 - Moscow - - Russia

Session	BH1-2-3	Accepted		Order	Time
Talk	Oral abstract	Title	The Galactic Center: possible interpretations of observational data
Coauthors
Abstract	Now there are two basic observational techniques to investigate a gravitational potential at the Galactic Center, namely, a) monitoring the orbits of bright stars near the Galactic Center to reconstruct a gravitational potential; b) measuring a size and a shape of shadows around black hole giving an alternative possibility to evaluate black hole parameters in mm-band with VLBI-technique. At the moment one can use a small relativistic correction approach for stellar orbit analysis (however, in the future the approximation will not be not precise enough due to enormous progress of observational facilities) while now for smallest structure analysis in VLBI observations one really needs a strong gravitational field approximation. We discuss results of observations, their conventional interpretations, tensions between observations and models and possible hints for a new physics from the observational data and tensions between observations and interpretations.
Pdf file

Session	PT2	Accepted		Order	Time
Talk	Oral abstract	Title	Shadow size for the supermassive black hole at the Galactic Center
Coauthors
Abstract	We discuss a shadow concept introduced by Falcke, Melia and Agol. We present estimates of shadow sizes for different parameters of black hole at the Galactic Center. We discuss results of observations of the smallest spot at the Galactic Center and their connections with the shadow size. We describe analytical dependences of shadow sizes as functions of charge and cosmological constant and discuss opportunity to get better fits with anti-de-Sitter or Reissner -- Nordstrom black hole models.
Pdf file

Session	GL3	Accepted		Order	Time
Talk	Oral abstract	Title	Gravitational Lensing Properties of Cosmological Black Holes
Coauthors
Abstract	If really such objects like cosmological black holes exist they may be studied with a standard technique like strong and weak gravitational lensing. Cosmological voids can be explained as the result the collapse of large perturbations into black hole with masses of the order of $10^{14}M_{\odot}$ and the expansion of the universe. The resulting image of the universe is that it is more homogeneous than expected from present observations. We discuss some lensing properties related to the cosmological black holes (CBHs), namely we consider differences in gravitational lensing for point like mass and extended mass distributions. We consider the singular isothermal sphere model as a toy (illustrative) model for an extended distribution of dark matter and a slightly more complicated isothermal sphere with a core.
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