Talk detail

Participant	Bozza, Valerio
Institution	Università di Salerno - Via Giovanni Paolo II 132 - Fisciano - - Italy

Session	PT2	Accepted		Order	Time
Talk	Oral abstract	Title	Alternatives To Schwarzschild In The Weak Field Limit
Coauthors
Abstract	Isolated objects are normally matched to an exterior Schwarzschild metric asymptotically falling down as 1/r. However, some examples of metrics falling faster than Schwarzschild are known: the Ellis wormhole, for example, falls as 1/r^2. Metrics falling faster than Schwarzschild have also been studied in the context of gravitational lensing, since they give rise to characteristic defocusing effects. Here we present a full classification and investigation of metrics with non-Schwarzschild weak field limit, analyzing the physical properties of the sources that support them, including the validity of energy conditions and the observational consequences of such metrics. Interestingly, we notice that even a minimally coupled scalar field with a simple power law potential can support a metric falling as 1/r^q with arbitrary exponent. The observation of objects with non-Schwarzschild metrics would be the signature of local violations of the weak energy condition.
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Session	GL3	Accepted		Order	Time
Talk	Oral abstract	Title	Gravitational lensing by black holes and the case of Sgr A*
Coauthors
Abstract	Light rays passing close to a black hole experience very strong deflections and can give rise to infinite sequences of images for any given source. We show how these images can be analytically described for any kinds of static or rotating metrics. In the case of Kerr metric, caustics become larger and larger for higher orders, and an exponentially large number of higher order images arises. We discuss how these results have been used in the popular movie "Interstellar". Some perspectives for observations of the strong deflection phenomenology come from the black hole in the Galactic center, where high resolution observational efforts are being concentrated.
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