• General Relativity
• High-Energy Astrophysics
• MHD
• Plasma Physics
• QPD

At the edge of a rotating black-hole, the physics looks like a science fiction story. In its rotation the black-hole drags everything around it and throws energy flows in the surrounding space, loosing part of its own energy. Magnetic fields are generated by the accreting plasma. In this setting, between the magnetic and gravitational fields (``a tug of war'') the plasma is under extreme conditions (an exotic plasma). The main focus of the thesis is to understand this plasma dynamics, through the use of different tools.
The first tool is the research of B. Punsly, i.e. the theory of GeneralRelativisticMagnetoHydroDynamics (GRMHD), which describes the plasma as a fluid in which the magnetic field is frozen, in presence of a gravitational field. The second tool is the research of D. Melrose, i.e. the theory of QuantumPlasmaDynamics (QPD), which instead describes the plasma as a set of fluctuations (normal modes of the plasma) and test particles, interacting and developing nonlinearities.
First, I have reported the main points of the two theories, clarifying some logical developments. Then, I have shown as both can be used in order to understand better the plasma dynamics under these extreme conditions. In other words, my work is new in its attempt to reconcile the two views (valid in certain regimes: the GRMHD “globally” and the QPD “locally”), i.e. to consider the same system (the plasma) from different perspectives in particular conditions.
Among these things, I have underlined as a particular QPD process furnishes the plasma needed to have GRMHD interaction, i.e. interaction between the black hole and the surrounding space-time. Having intense magnetic fields with respect to the MHD-fluid dynamics and low magnetic fields with respect to the QED-microscopic dynamics, i.e. with respect to the Schwinger field, I have shown as the two-photon pair creation process is more significant then the one-photon pair creation, making the former one of the principal sources of plasma in the magnetosphere of the black-hole.
Below the path that has been followed.
Study of the Kerr space-time and of its electromagnetic properties. Introduction of a plasma around the black-hole in order to have interaction between the black-hole itself and the surrounding space-time, i.e. the GRMHD interaction. Study of the QPD description of the plasma. Calculation of a QPD process, one of the principal sources of plasma in the magnetosphere of the black-hole.