Seminar of Theory of Relativity and Gravitation
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2023-03-10 (Friday)
room 1.40, Pasteura 5 at 11:15 
Jerzy Kijowski (CFT)On the dangers and ambushes awaiting a theoretical physicist as soon as he starts to apply variational principles
Deriving field equations from a variational principle has now become standard in theoretical physics. However, the very derivation of the Euler-Lagrange equations often relies on outdated prejudices and inevitably leads to paradoxes. I will try to put some order in this area.
2023-03-03 (Friday)
room 1.40, Pasteura 5 at 11:15
Adam Bac (FUW)Yang-Mills theory of the conformal Cartan connection: applications to gravity
We investigate the presymplectic potential current obtained from theYang-Mills theory with the normal conformal Cartan connection as itsgauge field. We compare it to the current derived from theEinstein-Hilbert action as well as the holographically renormalizedgravitational action on the conformal boundary of asymptotically deSitter spacetime. We also describe the Noether currents and chargesassociated with diffeomorphisms and gauge transformations. Seminar is also broadcasted via zoom
2023-01-27 (Friday)
room 1.40, Pasteura 5 at 11:15
Paweł Nurowski (CFT & Guandong Technion - Israel Institute of Technology)Triality and realizations of real forms of simple exceptional Lie group E6
2023-01-20 (Friday)
join us at 11:15
Włodzimierz Piechocki (NCBJ)Stochasticity of the BKL scenario
We quantize the solution to the massive model of the Belinski-Khalatnikov-Lifshitz (BKL)scenario using the integral quantization method. Quantization turns classical deterministicchaos into stochastic chaos. Broadcast in room 1.40
2023-01-13 (Friday)
room 1.40, Pasteura 5 at 11:15
Omid Makhmali (CFT)Conformal structures with an infinitesimal symmetry
We interpret the property of having an infinitesimal symmetry as a variational property in certain geometric structures. This is achieved by establishing a one-to-one correspondence between a class of cone structures with an infinitesimal symmetry and geometric structures arising from certain systems of ODEs that are variational. Such cone structures include conformal pseudo-Riemannian structures and distributions of growth vectors (2,3,5) and (3,6). In this talk we will primarily focus on conformal structures. The correspondence is obtained via symmetry reduction and quasi-contactification. Subsequently, we provide examples of each class of cone structures with more specific properties, such as having a null infinitesimal symmetry, being foliated by null submanifolds, or having reduced holonomy to the appropriate contact parabolic subgroup. As an application, we show that chains in integrable CR structures of hypersurface type are metrizable. This is a joint work with Katja Sagerschnig.
2022-12-16 (Friday)
room 1.40, Pasteura 5 at 11:15
James Lucietti (University of Edinburgh)Classification of static extreme black holes
The uniqueness theorems for asymptotically flat, static, black hole solutions to Einstein-Maxwell theory in four and higher dimensions are only valid for non-extreme black holes. In the extreme case the solution must belong to a generalised class of Majumdar-Papapetrou solutions. I will discuss recent work which establishes that the only spacetimes in this class, with a suitably regular event horizon, are the standard multi-black hole solutions. The proof involves a careful analysis of the near-horizon geometry and an extension of the positive mass theorem to Riemannian manifolds with conical singularities.
2022-12-09 (Friday)
join us at 11:15
Marek Szczepańczyk (University of Florida, Gainesville)Multi-messenger Astrophysics with gravitational-wave sources - preparing for the unexpected
The newly-born Multi-messenger Gravitational-Wave Astrophysics is the emerging Cosmic Frontier; it is also one of the most exciting areas in Science. Each observing run of gravitational-wave detectors provides plenty of surprises, challenging our understanding of the Universe and testing theories at an unprecedented level. For example, the discoveries of the first binary black hole merger or an intermediate-mass black hole came as great surprises. I will discuss how such unexpected sources challenged the astrophysical models and theories. The number of gravitational-wave detections will grow rapidly in the future observing runs, and the discoveries of unexpected gravitational-wave sources might play a key role in the endeavor of exploring the Universe. I will describe the suitable methods and the preparation for future observations. Broadcast in room 1.40
2022-12-02 (Friday)
join us at 15:30
Edward Wilson-Ewing (University of New Brunswick, Canada)On the fate of quantum black holes
I will present some work studying the quantum dynamics of the Lemaître-Tolman-Bondi space-times using a polymer quantization prescription in an analogous fashion to loop quantum cosmology. By solving an effective equation derived from this quantization, we find analytical solutions for the Oppenheimer-Snyder and thin-shell collapse models, and numerical solutions for a variety of asymptotically flat collapsing dust profiles. Quantum gravity effects cause a nonsingular bounce to occur in the Planck regime, resolving the singularity and resulting in the formation of an outgoing shockwave that substantially modifies the standard information loss problem.
2022-11-25 (Friday)
join us at 11:15
Theodore A. Jacobson (University of Maryland)Reduced phase space quantization of a 2+1 dimensional causal diamond
The system is defined as the domain of dependence of a topological disc with fixed boundary metric. We identify the reduced phase space as an infinite dimensional space of "boundary gravitons". To quantize we apply Isham’s group-theoretic scheme, with respect to a BMS_3 group acting on the phase space. We find that the twist of the diamond boundary loop is quantized in integer or half-integer multiples of the ratio of the Planck length to the boundary length.
2022-11-18 (Friday)
room 1.40, Pasteura 5 at 11:15
Igor Khavkine (Czech Academy of Sciences, Prague)Initial data for closed conformal Killing vectors and Killing-Yano 2-forms
Given an initial data set for the vacuum Einstein equations, KIDs (Killing Initial Data) are additional tensor fields and differential equations on them (restricted to the initial data surface) which, if they exist, are in bijection with Killing vectors on the bulk spacetime. We generalize this well-known construction also to CKIDs (Conformal Killing Initial Data) and cCYKIDs (closed Conformal Killing-Yano Initial Data). Our approach involves an exhaustive search through covariant "propagation identities" up to a given differential order. Important examples of vacuum spacetimes admitting conformal Killing vectors are pp-waves, while those admitting closed conformal Killing-Yano 2-forms are Kerr-NUT-(A)dS spacetimes.This is joint work with Alfonso García-Parrado. [arXiv:1912.04752]