Seminar of Theory of Relativity and Gravitation
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2019-06-07 (Friday)
room 1.40, Pasteura 5 at 11:15 
Jorge Ovalle (Universidad Simón Bolívar, Caracas)Black holes and gravitational decoupling
The so-called gravitational decoupling (MGD-decoupling) is a new approach which is being widely used. In this talk we explain in detail the MGD-decoupling mechanism and we show how to generate new black hole solutions when a spherically symmetric source modifies the Schwarzschild vacuum. Also we show the potential of the MGD-decoupling to study gravity beyond general relativity.
2019-05-31 (Friday)
room 1.40, Pasteura 5 at 11:15
Piotr Chruściel (University of Vienna)Maskit gluings and energy of asymptotically hyperbolic manifolds
In arXiv:0910.187, Isenberg, Lee, and Stavrov Allen presented a gluing construction of asymptotically hyperbolic general relativistic initial data sets which can be used to change the topology of the conformal boundary at infinity. The construction was inspired by a similar construction of Maskit in the context of complex geometry. In this work we present two applications of the method: 1) the first proof of positivity of total hyperbolic mass when the conformal boundary has spherical topology without restrictions on the dimension and the interior topology, and 2) a construction of initial data sets with negative total mass for higher genus boundary manifolds. The talk is based on joint work with Erwann Delay.
2019-05-24 (Friday)
room 1.40, Pasteura 5 at 11:15
Lennart Brocki (UWr)BMS Group at Spatial Infinity
In this talk I present a recent publication by Henneaux and Troessaert in which they propose new boundary conditions for asymptotically flat spacetimes at spatial infinity and find that the conserved charges close according to the BMS algebra. Their analysis relies on the Hamiltonian formalism of general relativity and is an extension of the work done by Regge and Teitelboim in 1974, which will therefore also be summarized, and mainly differs in the choice of parity conditions. For a more complete understanding the talk will also cover some basics about the BMS Group.
2019-05-17 (Friday)
room 1.40, Pasteura 5 at 11:15
István Rácz (MTA Budapest & IFT UW)Construction of initial data with monotonous Geroch mass
2019-04-26 (Friday)
room 1.40, Pasteura 5 at 11:15
Mikołaj Korzyński (CFT)Probing the spacetime curvature using geometric optics
In general relativity light propagation is affected by gravity, leading to the well-known effects of light bending, Shapiro delays and gravitational redshift. On top of that the results of observation of light by an observer are also affected by the special relativistic phenomena like the aberration or time dilation. All these effects influence the measurements of shape, parallax, redshift and position drift (proper motion) of distant objects. We show that all results of those measurements can be understood in terms of the kinematical variables, describing the motion of the observer and the emitter with respect to their local inertial frames, and certain functionals of the curvature along the line of sight. This opens up the possibility to probe the spacetime curvature directly using optical observations. Applications of the results include cosmology and numerical relativity.
2019-04-12 (Friday)
room 1.40, Pasteura 5 at 11:15
Michele Arzano (Sapienza University of Rome)Accelerated horizons and Planck scale kinematics
We extend the concept of accelerated horizons to the framework of deformed relativistic kinematics at the Planck scale. We show that the non-trivial effects due to symmetry deformation lead to a "blurring" of the horizon which manifests in a finite blueshift for Rindler modes approaching the horizon. We investigate whether, at a field theoretic level, this effect could manifest in the possibility of a finite horizon entropy density, thus providing a covariant version of 't Hooft "brick-wall" regulator.
2019-04-05 (Friday)
room 1.40, Pasteura 5 at 11:15
Remigiusz Durka (UWr)Pokręcone podejście do czasoprzestrzeni Tauba-NUT
Nuts approach to the Taub-NUT space-time
I offer new approach to the subject of Taub-NUT space-time supposedly possessing gravitational analog of the magnetic monopole. Starting from realizing that the source of many inconsistencies lies in neglecting the effects of the wire singularities present in that solution, I am able to explain existence of the NUT parameter by the means of quite peculiar rotation. Among many things, this leads to the consistent description of the black hole thermodynamics for the Lorentzian Taub-NUT spacetime with the essential contribution to the angular momentum and the total entropy.
2019-03-29 (Friday)
room 1.40, Pasteura 5 at 11:15
Paweł Nurowski (CFT)Parabolic geometry of a car
2019-03-22 (Friday)
room 1.40, Pasteura 5 at 11:15
Tomasz Pawłowski (UWr)Semiclassical states, high order quantum corrections and cosmology
Determining the dynamics of quantum systems beyond simplest 'textbook' ones on the genuine quantum level is usually very computationally expansive to the level of impractical. In cases, when the point of focus is the evolution of the semiclassical states, an alternative approach based on the so called Hamburger decomposition can be taken. There, one encodes the information about the state in the countable set of (expectation values of the) observables -- the moments, which essentially are the polynomial decomposition coefficients of the Wigner quasi-probability distribution. The set of the equations of motion for these moments is equivalent to a genuine quantum evolution, however a convenient cutoff (on the order of the moments) can be introduced, leaving just a couple of most relevant degrees of freedom. The accuracy of the resulting effective dynamics depends on the order of cutoff and the properties of particular system. In this presentation I will discuss the result of application of this (long known) formalism to a simple quantum model of inflationary cosmology, studying in particular the issue of accuracy of the description and effect of high order quantum corrections on Universe dynamics. I will present the case, where the high order effects significantly change the conclusions drawn from models including just the 2nd order moments (variances), in particular significant corrections may actually compensate the effects of variances making the evolution more classical.
2019-03-15 (Friday)
room 1.40, Pasteura 5 at 11:15
Jan Kwapisz (UW)Asymptotic safety in gravity and Conformal Standard Model
There are many proposals to extend the Standard Model designed to deal with its fundamental inconsistencies. Since no new particles have been detected experimentally so far, the models which add only one more scalar particle and possibly right-chiral neutrinos are favored. One of them is the Conformal Standard Model, which proposes a coherent solution to the Standard Model drawbacks including the hierarchy problem and a dark matter candidate.On the other hand there are signs that gravity is asymptotically safe. If there are no intermediate scales between electroweak and Planck scale then the Conformal Standard Model supplemented with asymptotically safe gravity can be valid up to arbitrarily high energies and give a complete description of particle physics phenomena.Moreover asymptotic safety hypothesis restricts the mass of the second scalar particle to $300 \pm 28$ GeV. The masses of heavy neutrinos can also be estimated as $683 \pm 83$ GeV so these predictions can be explicitly tested in the nearby future.