MG14 - Talk detail |
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Participant |
Maselli, Andrea | |||||||
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Center for Relativistic Astrophysics, Georgia Institute of Technology - 837 State Street - Atlanta - Georgia - USA | |||||||
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Oral abstract |
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Testing the strong field gravity regime with QPOs observations | |||||
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Abstract |
In this talk I analyze the chances to detect strong gravity effects through quasi-periodic oscillations (QPOs) of rotating black holes. Indeed, I derive the epicyclic frequencies of a slowly rotating black hole in the Eisntein-Dilaton-Gauss-Bonnet gravity, finding that they significantly differ from those computed in General Relativity. Then I apply the so called Relativistic Precession Model, showing that the differences between the QPOs frequencies predicted by the two theories of gravity considered, can be large enough to be observed. |
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Title |
Interacting vacuum-energy in a Post-Friedmann expanding Universe | |||||
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Abstract |
In this talk I use the recently derived post-Friedmann (PF) approach to cosmological large scale structure to study the interacting vacuum scenario in general relativity, which was proposed as a possible explanation for the current accelerated expansion of the universe. In this scenario vacuum can interact with cold dark matter, while it reduces to the cosmological constant when the interaction switches off. Extending the original PF formalism to describe a pressurelsess dust component coupled with the vacuum, I present the derivation of a new set of equations wich can be used to study structure formation, providing a comprehensive treatment of small and large scales. Analyzing the various regimes of this new approach, I show that at leading order, in the Newtonian approximation, only the background is modified compared to the standard \LambdaCDM equations. This simple result suggests a straightforward recipe to implement an interacting vacuum into cosmological N-body simulations, and to extract quantities such as the vector potential and difference between the scalar potentials, possibly leading to new observational signatures of these models. |
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