Relativity Seminar
of the Institute of Theoretical Physics

fall 2017

Given seminars:

October 3, 2017
Remarks on non-singular black holes
Prof. Valeri P. Frolov
Theoretical Physics Institute, Department of Physics, University of Alberta, Edmonton
October 9, 2017
!!! Monday, from 16:00 !!!
Inhomogeneous cosmological models, dark energy, black holes and viscous fluids in general relativity
Dr. Daniele Gregoris
Department of Mathematics, Dalhousie University, Halifax

I will introduce two different inhomogeneous cosmological models one of which is based on a regular lattice of black holes and a second one following the Geroch-Stephani generating technique. The second part will explain how dark energy and the inflation field can be modeled through the non-ideal equation of state of Shan-Chen accounting for their microscopical foundations and the motion of test particles undergoing scattering effect according to the Poynting-Robertson model and I will conclude mentioning a local way of detecting the horizon of a black hole in terms of the zeros of Cartan invariants.

October 10, 2017
at 13:15: Binary black hole initial data with a Schwarzschildean completion at space-like infinity
Dr. Georgios Doulis
Max Planck Institute for Gravitational Physics, Potsdam/Golm

Corvino (2000) showed that any given asymptotically flat and conformally flat initial data set can be truncated and glued along an annulus to a Schwarzschild metric in the exterior. It will be shown that this powerful result can be implemented numerically in an axisymmetric setting: a Schwarzschildean end will be glued to Brill-Lindquist data describing two non-rotating black holes. The total ADM mass of the resulting space-time will be computed and its dependence on the details of the gluing construction will be thorough investigated.

October 10, 2017
at 14:00: Local non-negative initial data scalar characterisation of the Kerr solution
Dr. Alfonso García-Parrado Gómez-Lobo
Theoretical Physics Department, Universidad del País Vasco, Bilbao

For any vacuum initial data set, we define a local, non-negative scalar quantity which vanishes at every point of the data hypersurface if and only if the data are Kerr initial data. Our scalar quantity only depends on the quantities used to construct the vacuum initial data set which are the Riemannian metric defined on the initial data hypersurface and a symmetric tensor which plays the role of the second fundamental form of the embedded initial data hypersurface. The dependency is algorithmic in the sense that given the initial data one can compute the scalar quantity by algebraic and differential manipulations, being thus suitable for an implementation in a numerical code. The scalar could also be useful in studies of the non-linear stability of the Kerr solution because it serves to measure the deviation of a vacuum initial data set from the Kerr initial data in a local and algorithmic way.

October 17, 2017
On the maximum energy of particles accelerated in the termination shocks of AGN jets
Anabella Araudo, PhD.
Astronomical Institute of the Czech Academy of Sciences, Spořilov

It has been suggested that relativistic shocks in extragalactic sources may accelerate the highest energy cosmic rays, but recent theoretical advances indicate that relativistic shocks are probably unable to accelerate particles to energies much larger than a PeV. We study the hotspots of radiogalaxies. The observed turnover of the synchrotron spectrum indicates that the maximum energy of electrons accelerated at the jet termination shock is less than 1 TeV in a 100 microG magnetic field. We show that this maximum energy cannot be constrained by synchrotron losses as usually assumed. We propose that the maximum energy is determined by ceasing the cross-field diffusion in a perpendicular 1 microG magnetic field. We demonstrate that Bell instabilities generated by the streaming of cosmic rays with the same energy as the most energetic electrons in the hotspot can amplify the turbulent field up to 100 microG. If the maximum energy of electrons is determined by the diffusion condition, the same limit applies to protons and therefore the maximum energy of ions is also less than 1 TeV. As a consequence, relativistic jet termination shocks are poor cosmic ray accelerators. We test this result by considering the radiogalaxy Cygnus A as a case study.

October 24, 2017
GW170817: the lightest black hole?
Dr. Ondřej Pejcha (and guests)
October 31, 2017
The things you did not like to know about spinning particles
Georgios Lukes-Gerakopoulos, PhD.
Astronomical Institute of the Czech Academy of Sciences, Spořilov
November 7, 2017
Time-domain metric reconstruction for self-force applications
Paco Giudice
Mathematical Sciences, University of Southampton
November 7, 2017
Entropy entanglement and information in black-hole evaporation
Dr. Ana Alonso-Serrano
November 14, 2017
Amplification of waves by scattering on rotating bodies
Mgr. Václav Bára
November 21, 2017
Probabilistic spacetimes
Mgr. Jakub Káninský
November 28, 2017
Kundt spacetimes in modified theories of gravity
Mgr. Michal Karamazov
December 5, 2017
Hidden symmetries of higher-dimensional black holes
doc. Pavel Krtouš
December 12, 2017
Classical and quantum description of minisuperspace actions of Einstein's gravity
Dr. Adamantia Zampeli
Department of Nuclear and Particle Physics, National and Kapodistrian University of Athens
December 19, 2017
A first-order secular theory for the post-Newtonian two-body problem with spin: the restricted case
Prof. Sante Carloni
Centro Multidisciplinar de Astrofisica, IST, University of Lisbon

We revisit the relativistic restricted two-body problem with spin employing a perturbation scheme based on Lie Series. Starting from a post-Newtonian expansion of the field equations, we develop a first-order secular theory that reproduces well-known relativistic effects such as the precession of the pericentre and the Lense-Thirring and geodetic effects. Additionally, our theory takes into full account the complex interplay between the various relativistic effects, and provides a new explicit solution of the averaged equations of motion in terms of elliptic functions. Our analysis reveals the presence of particular configurations for which non-periodical behaviour can arise. The application of our results to real astrodynamical systems (such as Mercury-like and pulsar planets) highlights the contribution of relativistic effects to the long-term evolution of the spin and orbit of the secondary body.

Other semesters:

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