Seminar of Theory of Relativity and Gravitation
2006/2007 | 2007/2008 | 2008/2009 | 2009/2010 | 2010/2011 | 2011/2012 | 2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | Seminar homepage
2019-03-08 (Friday)
room 1.40, Pasteura 5 at 11:15 
Marcin Kisielowski (NCBJ)Spin-foam model for gravity coupled to massless scalar field
Spin-foam theory is a path integral approach to the problem of Quantum Gravity. It has been conjectured that it is a covariant formulation of Loop Quantum Gravity but precise link between the theories has been an open problem for many years. In my talk I will present a spin-foam model that we have derived recently from canonical Loop Quantum Gravity coupled to massless scalar field.
2019-03-01 (Friday)
room 1.40, Pasteura 5 at 11:15
Jerzy Lewandowski & Adam Szereszewski (IFT UW)Extremal isolated horizons: a new constraint
2019-01-25 (Friday)
room 1.40, Pasteura 5 at 11:15
Maciej Kolanowski (IFT UW)What new(s) at infinity?
During this talk we shall discuss the structure of null infinity in asymptotically Minkowskian spacetimes. We will start with introducing basic description of scri: its internal and external geometry and their symmetries which are naturally connected with the radiative modes of gravitational field. We shall continue by quantizing (a'la Fock) said modes which will lead us to the infrared issues and soft hairs in the theory of black holes. The talk will be based mainly on the review paper arXiv:1808.07093v2 [gr-qc].
2019-01-18 (Friday)
room 1.40, Pasteura 5 at 11:15
Paweł Nurowski (CFT)Parabolic geometry of a car
2019-01-11 (Friday)
room 1.40, Pasteura 5 at 11:15
Arman Taghavi-Chabert (American University of Beirut)Twisting shearfree congruences of null geodesics in higher dimensions
On a conformal Lorentzian 4-manifold, there are certain foliations of nullgeodesics, known as shearfree congruences of null geodesics (SCNG), which are of central importance in the study of solutions of Einstein's equations. It is well-known that their generators must be principal null directions of the Weyl tensor. What is more, their leaf space is endowed with the structure of a CR manifold.In this talk I will give the integrability condition for the existence of SCNGs in dimension greater than four, and show that remarkably, in even dimension, the connection between SCNGs and (almost) CR structures still subsist under relatively mild curvature conditions on the Weyl tensor.Finally, one can play a similar game in split signature: under suitable curvature prescriptions, SCNGs induce Lagrange contact structures and projective structures.
2018-12-14 (Friday)
room 1.40, Pasteura 5 at 11:15
Przemysław Małkiewicz (NCBJ)The issue of dynamics in quantum gravity
Quantum mechanics is based on an external and unique parameter called time. According to general relativity such an entity does not exist. The evolution of gravitational systems may be expressed in terms of internal degrees of freedom. In my talk I will propose a reformulation of quantum mechanics which removes the absolute time and replaces it with an arbitrarily chosen internal degree of freedom, the internal clock. Then I will focus on the comparison of different internal clock-based quantum dynamics and use simple quantum cosmological systems to illustrate the result.
2018-12-07 (Friday)
room 1.40, Pasteura 5 at 11:15
Adam Chudecki (Politechnika Łódzka)Hyperheavenly spaces and congruences of the null strings - some new results
2018-11-30 (Friday)
room 1.40, Pasteura 5 at 11:15
Marius Oancea (AEI, Potsdam)The gravitational spin Hall effect of light
According to the postulates of general relativity, test particleswithout internal structure propagate along geodesics. Similarly,according to geometric optics, high frequency wave packets propagatealong null geodesics. However, taking internal structure andbackreaction into account leads to modified dynamics, often referred toas spin-orbit coupling. An important manifestation of this phenomenon isthe Spin Hall Effect, which manifests as a spin-dependent transverseshift in the particle's trajectory. The spin Hall effect has beenexperimentally observed for electrons in materials with spin-orbitcoupling, as well as for light propagating in an inhomogenous medium. Itis also expected to occur for light propagating in a curved spacetime,in the vicinity of a compact object. Here I will review some of the maintheoretical approaches for the gravitational spin Hall effect, discusstheir predictions and limitations, and present a possible path towards amore general theoretical framework.
2018-11-23 (Friday)
room 1.40, Pasteura 5 at 11:15
Andrzej Odrzywołek (UJ)On the black hole - torus system
2018-11-16 (Friday)
room 1.40, Pasteura 5 at 11:15
Przemysław Małkiewicz (NCBJ)Hamiltonian formalism and gauge-fixing conditions for cosmological perturbation theory
I will apply the Dirac procedure for constrained systems to the Arnowitt-Deser-Misner Hamiltonian formalism linearized around the Friedmann-Lemaitre universe. I will explain and employ some basic concepts such as Dirac observables, Dirac brackets, gauge-fixing conditions, reduced phase space, physical Hamiltonian and physical dynamics. In particular, I will use the key concept which is the canonical isomorphism between different gauge-fixed surfaces. The formalism is first developed for the universe with a single fluid and then extended to the multi-fluid case. I will apply the formalism to describe the reduced phase space of cosmological perturbations in some gauges that are popular in the cosmological literature.