Seminar is held on Tuesdays at 13:10 pm in the lecture room of the Institute
on the 10th floor of the department building at Trója, V Holešovičkách 2, Prague 8
I consider light propagation in a plasma on a general relativistic spacetime. In the first part of my talk I review a Hamiltonian formalism for light rays in a pressure-less non-magnetised plasma and I present, on the basis of this formalism, the resulting equations for the deformation of light bundles (Sachs equations). In the second part I discuss the shadows of black holes in the presence of a plasma. The latter is of relevance in view of the forthcoming observations by the Event Horizon Telescope.
An existing canonical formulation of dynamics for a discrete system will be briefly reviewed and used to define a version of quantum field theory on a fixed simplicial lattice. Such a model may serve as an intermediate step for incorporating matter or gauge fields into lattice-based quantum gravity theories. For start, we shall consider Euclidean lattice and real scalar field. We will discuss the relation to the algebraic approach used in quantum field theory in curved spacetime and to path integral.
The fate of Cauchy horizons, such as those found inside charged black holes, is intrinsically connected to the decay of small perturbations exterior to the event horizon. As such, the validity of the Strong Cosmic Censorship conjecture is tied to how effectively the exterior damps fluctuations. By studying scalar and fermionic fields in the exterior of Reissner-Nordstrom-de Sitter black holes we identify three families of modes: one directly linked to the photon sphere, another family whose existence and timescale is closely related to the de Sitter horizon and, finally, a third family which dominates for near-extremally-charged black holes. We give a detailed description of scalar and fermionic perturbations of such black holes, and conjecture that Strong Cosmic Censorship is violated in the near extremal regime.
Jiří Bičák Oldřich Semerák