Relativistický seminář
Ústavu teoretické fyziky

jaro 2017

Proběhlé semináře:

7. března 2017
Dissipative effects in cosmology
Dr. Giovanni Acquaviva
(seminář v angličtině)

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.

14. března 2017
Generalising the coupling between spacetime and matter
Dr. Sante Carloni
Multidisciplinary Centre for Astrophysics (CENTRA), Instituto Superior Técnico (IST), University of Lisbon
(seminář v angličtině)
21. března 2017
Exact solutions with a scalar field in general relativity
Prof. Hideki Maeda
Hokkai-Gakuen University, Sapporo, Japan
(seminář v angličtině)
28. března 2017
Canonical quantization of homogeneous cosmological models
MSc. Manto Zampeli
National and Kapodistrian University of Athens
(seminář v angličtině)
4. dubna 2017
Hypervelocity stars and S-stars
Dr. Jaroslav Haas
Astronomický ústav UK
(seminář v angličtině)
11. dubna 2017
Celestial Cinematography with Large Synoptic Survey Telescope
Dr. Andrei Nomerotski
Brookhaven National Laboratory (Cosmology and Astrophysics Group), New York
(seminář v angličtině)

Investigation of Dark Energy remains one of the most compelling tasks for modern cosmology. It can be studied with several probes which are accessible through precise and deep surveys of the Universe. In the talk I will review the next generation of experiments to probe the Dark Energy with an emphasis on fully depleted silicon sensors with extended infrared sensitivity. Large Synoptic Survey Telescope which will start to take data in 2021 remains the front-runner in the sensitivity. It will precisely measure the positions and shapes of four billion galaxies along with estimates of their distances, 100,000 massive galaxy clusters, and 250,000 Type Ia Supernovae, providing an order-of-magnitude improvement relative to current experiments.

25. dubna 2017
A short introduction to xAct - efficient tensor computer algebra for Mathematica
Dr. Tomáš Málek
Matematický ústav AV ČR (Oddělení algebry, geometrie a matematické fyziky)
(seminář v angličtině)

The package is availabe on the website 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:

2. května 2017
Kerr-Newman black hole in the formalism of isolated horizons
Mgr. Aleš Flandera
(seminář v angličtině)
9. května 2017
Pictures at an exhibition (of GW collapse)
Mgr. Anton Khirnov
(seminář v angličtině)
23. května 2017
Analytical study of spinning objects in general relativity
Dr. Satish Kumar Saravanan
National Institute for Subatomic Physics (Nikhef), Amsterdam
(seminář v angličtině)
13. června 2017
Horizon thermodynamics from Einstein's equation of state
(See also seminar at 10:40)
Dr. David Kubizňák
Perimeter Institute for Theoretical Physics, Waterloo, Ontario
(seminář v angličtině)

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.

16. června 2017
!!! MIMOŘÁDNĚ V PÁTEK (ve 13:10) !!!
Gravitational-wave echoes from macroscopic quantum gravity effects
Prof. Luis J. Garay
Department of Theoretical Physics, Faculty of Physics, Complutense University of Madrid
(seminář v angličtině)
23. června 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
(seminář v angličtině)

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.

29. června 2017
Primordial power spectra in loop quantum cosmology
Dr. Daniel Martin de Blas
Instituto de Física, Pontificia Universidad Catolica de Chile
(seminář v angličtině)

Loop quantum cosmology is a theory for the quantization of cosmological spacetimes that follows the ideas and techniques of loop quantum gravity. The detailed study of its quantum evolution for simple cosmological spacetimes has been shown that the classical singularity of the Big Bang is cured and replaced by a quantum bounce. In the recent years a lot of effort has been put in the study of cosmological perturbations in the context of loop quantum cosmology, mixing its techniques of quantization with more standard quantum field theory ones for the perturbations. In this talk I will focus on presenting numerical results for the primordial power spectra for cosmological perturbations using the effective equations of motion coming from loop quantum cosmology and different elections of vacuum for the perturbations.

20. července 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
(seminář v angličtině)

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.

Další ročníky:

© 6. října 2017; Oldřich Semerák <>
© 2. října 2022; vygenerováno pomocí aplikace seminar, verze 2.04 (2003-09-02); správce <>