XV Black Holes Workshop

Session

Session 2

Dec 19, 2022, 11:00 AM

ISCTE - University Institute of Lisbon

94. C. Herdeiro: The fate of the light-ring instability

12/19/22, 11:00 AM

Ultracompact objects with light-rings (LRs) but without an event horizon could mimic black holes (BHs) in their strong gravity phenomenology. But are such objects dynamically viable? Stationary and ax- isymmetric ultracompact objects that can form from smooth, quasi-Minkowski initial data must have at least one stable LR, which has been argued to trigger a spacetime instability; but its...

95. P. Cunha: Fundamental photon orbits and spacetime instabilities

12/19/22, 11:15 AM

Generic equilibrium black holes (BHs) and ultra-compact horizonless objects can admit a special set of planar and circular bound null orbits: Light Rings (LRs). These orbits are deeply connected to strong gravitational lensing. For instance, in spherical symmetry, LRs completely determines the photon spheres and the BH shadow image.

In generic equilibrium spacetimes, non-planar bound photon...

96. A. Frassino: Quantum black holes and holographic complexity

12/19/22, 11:30 AM

In this talk, I will consider quantum effects on some specific black hole solutions and take into account their gravitational backreaction. In particular, I will describe the holographic construction of the quan- tum BTZ black hole (quBTZ) from an exact four-dimensional bulk solution.

I will present some of the thermodynamic properties of these black holes, focus on the generalized first...

97. L. Annulli: Spin-induced scalarization and magnetic fields

12/19/22, 11:45 AM

In the presence of certain non-minimal couplings between a scalar field and the Gauss-Bonnet curvature invariant, Kerr black holes can scalarize, as long as they are spinning fast enough. This provides a distinctive violation of the Kerr hypothesis, occurring only for some high spin range. Motivated by the fact that self-gravitating magnetic fields, by themselves, can promote “spin-induced”...

98. G. Raposo: Elastic stars and compactness bounds

12/19/22, 12:00 PM

In this presentation I will introduce a rigorous and general framework to study systematically self- gravitating elastic materials within general relativity. I will introduce two classes of elastic equations of state that can be used to explore properties of exotic compact objects. I will discuss the general effects of elasticity on the structure of compact objects, including an analysis on...

99. R. Panosso Macedo: Pseudospectrum and quasinormal mode (in)stability

12/19/22, 12:15 PM

Black hole spectroscopy is as a powerful approach to extract space- time information from gravitational wave observed signals. However, quasinormal mode (QNM) spectral instability under high wave- number perturbations has been recently shown to be a common classical general relativistic phenomenon. I will discuss these recent results on the stability of QNM in asymptotically flat black hole...

100. P. Garcia: Recent results from the GRAVITY collaboration on SgrA* supermassive black hole

12/19/22, 12:30 PM

GRAVITY is the most advanced optical-infrared instrument in a ground-based observatory. It sharpens the light of four giant 8 m telescopes with advanced adaptive optics and combines it interferometrically, achieving exquisite precision. It was central to the experimental breakthrough justifying part of the 2020 Physics Nobel Prize.

We will conduct a review of past achievements of the...