Search Talks

In this talk, we will provide an overview of recent developments in the quantization of Cylindrically symmetric spacetimes, which contain the Einstein-Rosen gravitational waves. This class of solutions leads to an integrable field theory, and its phase space can be expressed directly in terms of initial data living on a null generator. The corresponding Poisson algebra appears in the double null sheet formulation of full 3+1 gravity (Reisenberger, 2007), as essentially a Poisson subalgebra on each null generator. This suggests that the algebraic quantization introduced by Korotkin-Samtleben in the context of cylindrically symmetric gravity is relevant for the search for the full quantum theory. We will present some results concerning this quantum algebra, where two Wick-type algebraic structures emerge. Finally, we will discus the known quantization of the Einstein-Rosen waves with one polarization, due to Ashtekar-Pierri, as a subsector of the general two polarizations case.

Gravitational waves (GW) from compact binaries provide excellent opportunities for testing general relativity (GR) in the strong- and dynamical-field regime. So far, inspiral-based tests have mostly assumed smooth deviations from GR within a post-Newtonian description, thereby overlooking certain beyond-GR effects that can arise in well-motivated extensions including quantum gravity, dark energy, and dark matter. In this talk, I will present an example of such an overlooked effect arising from massive scalar fields nonminimally coupled to gravity, and discuss recent constraints on this scenario using GW observations. I will then introduce a recently developed AI-based approach that incorporates both smooth and nonsmooth deviations within a unified, theory-agnostic parametrization for inspiral tests of GR. 

Current waveform models of binary black hole mergers incorporate a large amount of analytical information during the inspiral phase. In contrast, post-merger descriptions typically rely on phenomenological ansätze informed by numerical relativity, with the quasi-normal mode frequencies providing the only direct analytical input. In this seminar, I will first give a gentle introduction to black hole perturbation theory and the Green’s function approach, which is useful for describing the time-domain response of a black hole to a dynamical source, e.g., an infalling test particle. I will then present an analytical framework to study the dynamical excitation of quasi-normal modes during the plunge–merger–ringdown stages for generic orbits, including highly eccentric ones, and discuss its implications for ringdown modeling. I will conclude by presenting novel insights into the modelling of the prompt response, fundamental to correctly capture the signal emitted during the merger at the linear level. 

We study thermodynamics of spherically-symmetric spacetime with the aim of exploring spacetime entropy as an adiabatic invariant. We first describe the geometry and dynamics in terms of a local frame adapted to spherical foliations and find a geometro-hydrodynamic interpretation: the spacetime can be viewed as the worldvolume of a concentric stack of "gravitational bubbles", spherical collective modes with the Misner-Sharp energy density and a geometric pressure. We then introduce a notion of work and heat, and investigate the covariant phase space of a thermodynamic action corresponding to the adiabatic boundary condition. Identifying the phase space with the thermodynamic state space, these should provide the foundation for the spacetime thermodynamics. As an example, we apply this to the apparent horizon and employ Caratheodory’s idea, to derive the entropy of the dynamical horizon as an adiabatic-invariant Hamiltonian. This agrees with the Bekenstein-Hawking formula for the surface area of the apparent horizon, where a dynamical version of Hawking temperature appears. [arXiv: 2601.03077 + to appear]