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
In this talk I analyze the construction of quantum field theory in multiply-connected spacetimes (i.e. spacetimes that contain regions with closed timelike curves (CTCs)). Additionally, I explore how particle detectors can discern the presence of CTCs in causally disconnected regions and differentiate between various spacetime topologies.
In this talk, I will show that the general EFT extension of GR can be constrained with two fundamental properties of GR: non-birefringent gravitational waves and isospectral black hole quasinormal modes (QNMs). This leads to a novel class of EFTs which exhibit intriguing features that align with string theory predictions. I will then discuss how to compute the QNMs through a geometric correspondence between eikonal QNMs and unstable gravitational wave orbits, which I will apply to equatorial orbits. Beyond the equatorial plane, we solve the full wave equation using an effective scalar description of gravitational perturbations. These results provide the first computation of QNMs for Kerr black holes with arbitrary spin in an EFT extension of GR.
In this talk I shall discuss propagation of the high-frequency electromagnetic and gravitational waves in a curved spacetime. I shall describe a so-called spinoptics formalism which takes into account the interaction of the spin of the field with the curvature of the background metric. This is achieved by modifying the standard geometric optics equations by including the helicity sensitive terms of the order $1/\omega$ in the eikonal equation. I shall demonstrate that these spinoptics equations can be obtained from an effective action. This allows one to reduce the study of the propagation of the high-frequency waves to the study of classical dynamics of massless particles with internal discrete degrees of freedom (helicity). The formalism is covariant and it can be applied for arbitrary (vacuum) space-time background. I shall illustrate the application of the spinoptics by discussing circular light propagation near a stationary black hole, and explain how hidden symmetries of the Kerr metric make it possible to solve the spinoptics equations exactly. At the end of the talk, I shall briefly discuss possible applications of the developed formalist to astrophysical problems.
In this talk, I will show how an infinite tower of higher-curvature corrections to Einstein gravity gives rise to the formation of regular black holes in space-time dimensions larger than four. These theories consist of specific combinations of higher-curvature terms at each order, multiplied by free couplings. I will begin by introducing a class of higher-curvature gravities with second-order equations of motion on spherically symmetric backgrounds, which will play a central role in the mechanism leading to these regular black holes. I will then examine the static and spherically symmetric black holes of these theories, which become regular after the introduction of the infinite tower of corrections, and demonstrate that the spherical collapse of a thin shell indeed leads to the formation of such regular black holes.
David Kubizňák Oldřich Semerák