Relativity Seminar
of the Department of Theoretical Physics


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


Next seminars:

No seminars are planned for the near future.


Previous seminars:

October 18, 2016
An investigation of quasilocal systems in general relativity
Nezihe Uzun, PhD.
Middle East Technical University, Ankara / University of Canterbury, Christchurch
October 25, 2016
Quantum cosmology: Games without frontiers
Ana Alonso-Serrano, PhD.
Institute for Fundamental Physics, Spanish National Research Council, Madrid
November 1, 2016
Scalar perturbations of K-essence models with applications to late-time cosmic acceleration
Mgr. Jan Novák, PhD.
Department of Mathematics, Faculty of Informatics and Statistics, University of Economics in Prague

An elementary introduction to scalar perturbations of the K-essence models. I will show how to obtain a late-time cosmic acceleration and indicate how to use the approach also for a>a0, which will be useful for modelling of the earlier stages of cosmic evolution.

November 8, 2016
No seminar (Dean's day)
(seminar in Czech language)
November 15, 2016
Rotational electromagnetic supperradiance
Mgr. Tomáš Ledvinka, PhD.
ITP
November 22, 2016
Isolated horizons and the Meissner effect
Mgr. Martin Scholtz, PhD.
ITP
November 29, 2016
Kundt spacetimes with scalar field
RNDr. Otakar Svítek, PhD.
ITP
December 6, 2016
Isolated horizons and the Meissner effect (continued from slide 22)
Mgr. Martin Scholtz, PhD.
ÚTF
December 13, 2016
Mass of Kerr-Newman black holes in external magnetic field
Roberto Oliveri
Université Libre de Bruxelles / International Solvay Institutes, Bruxelles
March 7, 2017
Dissipative effects in cosmology
Dr. Giovanni Acquaviva
ITP

I review some models that take into account dissipative effects of fluids in an expanding Universe, in the context of General Relativity. The effect of dissipation on the cosmic evolution is assessed by means of different methods, such as perturbation theory and dynamical systems analysis.

March 14, 2017
Generalising the coupling between spacetime and matter
Dr. Sante Carloni
Multidisciplinary Centre for Astrophysics (CENTRA), Instituto Superior Técnico (IST), University of Lisbon
March 21, 2017
Exact solutions with a scalar field in general relativity
Prof. Hideki Maeda
Hokkai-Gakuen University, Sapporo, Japan
March 28, 2017
Canonical quantization of homogeneous cosmological models
MSc. Manto Zampeli
National and Kapodistrian University of Athens
April 4, 2017
Hypervelocity stars and S-stars
Dr. Jaroslav Haas
Astronomical Institute, Charles University
April 11, 2017
!!! IN THE "T1" LECTURE ROOM !!!
Celestial Cinematography with Large Synoptic Survey Telescope
Dr. Andrei Nomerotski
Brookhaven National Laboratory (Cosmology and Astrophysics Group), New York

April 18, 2017
No seminar
(seminar in Czech language)
April 25, 2017
A short introduction to xAct - efficient tensor computer algebra for Mathematica
Dr. Tomáš Málek
Institute of Mathematics of the Czech Academy of Sciences (Department of algebra, geometry a mathematical physics)

The package is availabe on the website www.xact.es. There you can find synopsis:
xAct is a suite of free packages for tensor computer algebra in Mathematica. xAct implements state-of-the-art algorithms for fast manipulations of indices and has been modelled on the current geometric approach to General Relativity. It is highly programmable and configurable. Since its first public release in March 2004, xAct has been intensively tested and has solved a number of hard problems in GR.

Below you can find notebooks prepared for the seminar:

May 2, 2017
Kerr-Newman black hole in the formalism of isolated horizons
Mgr. Aleš Flandera
ITP
May 9, 2017
Pictures at an exhibition (of GW collapse)
Mgr. Anton Khirnov
ITP
May 16, 2017
No seminar
(seminar in Czech language)
May 23, 2017
Analytical study of spinning objects in general relativity
Dr. Satish Kumar Saravanan
National Institute for Subatomic Physics (Nikhef), Amsterdam
June 13, 2017
Horizon thermodynamics from Einstein's equation of state
Dr. David Kubizňák
Perimeter Institute for Theoretical Physics, Waterloo, Ontario

Padmanabhan's horizon thermodynamics is an alternative proposal for seeking connections between black hole physics and thermodynamics. I will overview the original Padmanabhan's argument and point towards its weaknesses and how to amend them. Namely, I will show that by regarding the Einstein equations as equations of state, a full cohomogeneity horizon thermodynamics first law can be derived. In this approach both the entropy and the free energy are derived concepts, while the original (degenerate) horizon first law is recovered by a Legendre projection. These results readily generalize to higher curvature gravities and establish a way of how to formulate consistent black hole thermodynamics without conserved charges.

June 16, 2017
!! ON FRIDAY !!!
Gravitational-wave echoes from macroscopic quantum gravity effects
Prof. Luis J. Garay
Department of Theoretical Physics, Faculty of Physics, Complutense University of Madrid
June 23, 2017
!!! Beware the change in date, time is still 13:10 !!!
Dark energy without dark energy: Observational tests and theoretical challenges
Prof. David L. Wiltshire
Department of Physics and Astronomy, University of Canterbury, Christchurch, New Zealand

I will give an overview of the timescape cosmology. It is assumed that inhomogeneities - voids, walls and filaments - modify the average background geometry of the universe, which is no longer a simple solution of Einstein's equations with homogeneous dust. To obtain a viable phenomenology without dark energy, I provide a framework for interpreting Buchert's backreaction formalism, by revisiting fundamental issues relating to the definition of gravitational energy in a complex geometry. Cosmic acceleration is realized as an apparent effect due both to backreaction and the relative calibration of the asymptotic clocks of observers in gravitationally bound structures relative to the time parameter that best describes the average statistical evolution. The cosmic coincidence problem is solved directly in relation to the growth of the void fraction.

Predictions of the timescape phenomenology are very close to the standard cosmology, but with differences which can be tested. I will outline current observational constraints, future tests (e.g., with the Euclid satellite), and also theoretical challenges that need to be overcome for backreaction models to fully compete with the Lambda Cold Dark Matter cosmology.

June 29, 2017
!!! MIMOŘÁDNĚ VE ČTVRTEK V 10:30 !!!
Primordial power spectra in loop quantum cosmology
Dr. Daniel Martin de Blas
Instituto de Física, Pontificia Universidad Catolica de Chile

July 20, 2017
!!! MIMOŘÁDNÝ SEMINÁŘ, ve ČTVRTEK od 13:10 !!!
Lorentz invariance and the zero-point stress-energy
Prof. Matt Visser
School of Mathematics, Statistics, and Computer Science, Victoria University of Wellington, New Zealand

Some 65 years ago (1951) Wolfgang Pauli noted that the zero-point energy density could be set to zero by a carefully fine-tuned cancellation between bosons and fermions. In this seminar I will argue in a slightly different direction: The zero-point energy density is only one component of the zero-point stress energy tensor, and it is this tensor quantity that is in many ways the more fundamental object of interest. I shall demonstrate that Lorentz invariance of the zero-point stress energy tensor implies finiteness of the zero-point stress energy tensor, and vice versa.


Previous semesters:


Jiří Bičák                                                                                                  Oldřich Semerák


© July 12, 2017; Oldřich Semerák <semerak@mbox.troja.mff.cuni.cz>
© September 22, 2017; generated by application seminar, version 2.04 (2003-09-02); webmaster <Pavel.Krtous@mff.cuni.cz>