Seminář se koná v úterý ve 13:10 v posluchárně ÚTF MFF UK
v 10. patře katedrové budovy v Tróji, V Holešovičkách 2, Praha 8
A series of works by Belinskii, Khalatnikov and Lifshitz (BKL) conjectured that spacetime near a generic spacelike singularity locally behaves in a chaotic way. Since BKL conjecture concerns very strong gravity regimes, it is natural to ask how quantum gravity influences it. We tackle this question by looking at perturbative quantum corrections to Bianchi I and II metrics approximating the relevant features of BKL conjecture. We argue that even such perturbative effects can completely change the nature of BKL dynamics. While we work in the framework of thermodynamic gravity, our findings also apply to the effective dynamics of loop quantum cosmology.
Isolated horizons provide a local generalization of the black hole horizon adapted to dynamical settings. Their intrinsic geometry is described by a Riemannian 2-metric and a rotation 1-form. Curiously, if the horizon is extremal or of Petrov Type D, the induced Einstein Equations may be expressed as local geometry constraints, namely the Petrov Type D and the Near Horizon Geometry Equations. I will present the full family of solutions for spherical, axially symmetric horizons, possibly with a conical singularity. I will discuss their embeddings into the Plebański-Demiański spacetimes with the NUT parameter, either in the periodic-time interpretation by Misner or in the presence of space-time conical singularities.
TBA
I will describe a new construction of Ricci flat metrics using gauged linear sigma models satisfying the Calabi-Yau condition. The approach will be introductory using elementary examples to illustrate the main points and to underline the connection between physical and mathematical concepts.
David Kubizňák Oldřich Semerák