Black Hole Perturbations and Holography

9 Mar 2026, 09:00 → 20 Mar 2026, 18:00 Europe/Zurich

Seminar Room D (IGAP, Trieste)

Recent progresses in the study of black hole perturbations have driven important developments into the understanding of their gravitational dynamics and their holographic dual strongly coupled systems. Further progress has also been made in understanding how dynamical gravity and bulk geometry emerge from strongly coupled systems. This yields the need for a platform where researchers of these fields can collaborate and share insights. This program aims to provide such a platform. A range of topics will be covered in this event, including black hole perturbations, boundary signatures of bulk geometry and conformal field theories at finite temperature.

Recordings of the talk can be found at: www.youtube.com/@InstituteforGeometryandPhysics

Monday 9 March

Coffee break

Alessio Miscioscia: Regge's Inferno

I will focus on large-spin operators in conformal field theories (CFTs) in d>2 (2+1 and 3+1 in particular) space-time dimensions and I will show how these operators could be studied by placing the CFT on appropriate pp-wave backgrounds. These geometries admit Heisenberg-group symmetries, and together with the locality of quantum fields on such spacetimes, constrains the asymptotic behavior of the spectrum in the large-spin limit.
Studying CFT on the pp-wave backgrounds provides a smooth interpolation between the small-twist regime, corresponding to the Regge or light-cone bootstrap limit, at low temperature and a strongly coupled regime characterized by large twist at high temperature. Finally, I will comment on how the existence of a vacuum state on the pp-wave is equivalent to a novel unitarity bound in 3+1 dimensions.

Natalia Pinzani-Fokeeva: Horizon symmetries, hydrodynamics, and chaos

A local symmetry is required to formulate fluid dynamics from a modern effective field theory point of view. Black hole horizons possess the same redundancy. In this talk, I will show how asymptotic symmetries of horizons can be interpreted as symmetries of a dual hydrodynamic theory in the context of holography. I will also show how the horizon structure leads to additional symmetries responsible for the chaotic behavior of the dual theory.

Coffee break

Tuesday 10 March

Coffee break

Talk: Manuela Kulaxizi

Rodolfo Russo: Black hole perturbation theory for microstates

I will discuss how to apply black hole perturbation theory to regular supergravity solutions in a holographic setup. Such solutions represent heavy states in the dual CFT. I will focus on examples relevant to the AdS3/CFT2 and the AdS5/N=4-SYM dualities. On the technical side the problem involves the Heun equation, as it also happens in the standard case of black holes. I'll highlight the similarities and the differences between these various cases and, as a physical application, show how to derive strongly coupled 4-point CFT correlators via the AdS/CFT duality.

Coffee break

Wednesday 11 March

Coffee break

Enrico Marchetto: Thermal analytic bootstrap methods for holography

In this talk I will introduce a general analytic bootstrap framework for thermal scalar two-point functions, explaining how to decompose them in terms of generalized free field correlators. I will then apply this framework to holographic CFTs at leading order in large N and large coupling, with the intent of studying AdS black brane solutions. I will address the specific challenges for the analytic bootstrap arising from considering correlators of scalar fields with integer dimensions and the role played by bouncing singularities. Finally, I will comment on the agreement between our results, perturbative, and numerical computations in the gravitational bulk.

Nejc Čeplak: Complex Geodesics and Black Hole Singularities in Holography

Black hole singularities leave distinct imprints on holographic correlation functions. These signatures can be traced back to bouncing geodesics: Null geodesics that originate on one boundary of an eternal AdS black hole, reflect off the curvature singularity, and return to a different asymptotic boundary. This picture applies both to neutral solutions, where the singularity is spacelike, and to charged black holes, where it is timelike.
In this talk, I will discuss bouncing geodesics in a simple and analytically tractable model that interpolates between neutral and charged black holes while retaining the essential features of both. I will emphasize the role of complex geodesics that probe timelike singularities and show, using the Operator Product Expansion (OPE), that divergences in the complex-time plane of holographic correlation functions occur precisely at the locations predicted by these geodesics.

Coffee break

Thursday 12 March

Coffee break

Jordan Cotler: Quantum Mechanics of the Hartle-Hawking State

The no-boundary state in de Sitter offers a compelling framework for specifying the initial conditions of our universe. Many (but famously not all) features of the state agree beautifully with empirical observations and have served as a foundation for initial conditions in inflationary cosmology. We explore its relation to entropy puzzles in de Sitter spacetimes. We then compute the norm of the no-boundary state and show that the contributions from geometries with spherical spatial slices, including the Hartle-Hawking geometry and fluctuations around it, vanish to all loops in perturbation theory. We then discuss the resulting implications for theoretical cosmology.

Discussion session: Andrei Parnachev, Elli Pomoni

Coffee break

Carlo Heissenberg: Waveforms at Infinity and at the Horizon

The direct detection of gravitational waves has put the relativistic two-body problem in the spotlight and stimulated progress in perturbative approaches that provide analytic insight into its dynamics. Two strategies that have been witnessing interesting developments to this end are the ones based on scattering amplitudes, which apply to binary scatterings at large impact parameter, and on black-hole perturbation theory, which applies to extreme-mass-ratio binaries. In this talk, I will discuss how these two methods play complementary roles, and how they can be employed to calculate the gravitational perturbations induced by scatterings of black holes both far away, at null infinity, and close to the event horizons. Such waveforms characterize in particular the amounts of energy and angular momentum that are emitted and reabsorbed by the system.

Friday 13 March

Coffee break

Riccardo Gonzo: Self-force EFT for black hole binaries: bridging weak and strong field expansions via critical orbits

We discuss an effective field theory for point particles modeling black holes within the gravitational self-force (small mass ratio, or GSF) expansion, including spin effects. Using both diagrammatic background-field methods and traditional self-force techniques, we analyze the resulting 1SF metric perturbations and radiative observables. We then show that orbit-averaged observables such as the energy loss exhibit characteristic logarithmic divergences near the separatrix curve between scattering and plunging orbits, signalling the presence of a non-perturbative Regge cut in the strong-field. Exploiting this analytic structure, we construct resummed expressions that interpolate between perturbative weak-field results (Post-Minkowskian and Post-Newtonian expansions) and strong-field (GSF) dynamics. Finally, I will comment on the implications of such critical orbits for holography applications.

Fabio Riccioni: The multipolar structure of Myers-Perry black holes and scattering amplitudes

Inspired by scattering amplitude techniques, we show how to derive the most general class of energy-momentum tensors in momentum space associated with a given multipolar structure of spacetime in arbitrary dimensions, and built out of a mass and an angular momentum, at any order in the spin expansion and at linear order in the gravitational coupling. We identify the recurrence relations allowing to obtain the multipolar structure of the Kerr and the Myers-Perry black hole solutions. We show how minimally coupled spin 1 and spin 3/2 fields reproduce the energy-momentum tensor of Kerr up to quadrupole and octupole moment respectively, and we perform the same analysis for vectors and antisymmetric tensors in five dimensions.

Coffee break

Monday 16 March

Coffee break

Yilber Fabian Bautista:: Gravitational Waves meet Black Hole Perturbations

In this talk, we review the modern effective field theory approach to precision
computations of gravitational-wave templates for binary black hole mergers. In
particular, we emphasize the characterization of finite-size effects—such as tidal
Love numbers, horizon dissipation, and spin effects—for black holes in both four
and five dimensions.
Although finite-size effects are expected to contribute subdominantly to bi-
nary waveforms, they may nevertheless become measurable with future gravitational-
wave observatories. For black holes, the corresponding effective coefficients are
obtained through a matching computation between the effective point-particle
description and the ultraviolet-complete solutions provided by black hole per-
turbation theory.
We also review a reformulation of these perturbative results in terms of
Nekrasov–Shatashvili functions.

Benjamin Withers: Spectral decomposition of the black hole Green’s function

For approximately 40 years the state of the art in black hole spectroscopy has been to try to represent retarded Green’s functions as a sum of quasinormal modes. This appears to follow as a natural consequence from doing a Fourier integral. However, it is well known that such a sum cannot be complete, and at early times the quasinormal mode sum does not converge. I will present a resolution of this puzzle, and show that retarded Green’s functions of black hole spacetimes can be expressed as a convergent mode sum everywhere in spacetime. At late times a quasinormal mode sum converges, while at early times a Matsubara mode sum converges. The two regions are separated by a lightcone which scatters from the black hole potential.

Coffee break

Tuesday 17 March

Coffee break

Paolo Arnaudo: Gravitational perturbations of asymptotically AdS black branes and multiple polylogarithms

In this talk, I will present different analytic techniques to obtain the quasinormal mode frequencies of gravitational perturbation of asymptotically anti-de Sitter black branes. The focus will be primarily on computing the transport coefficients associated with the shear sector for N = 4 SYM, by performing a bulk computation in the five-dimensional black brane background. The procedure will be then generalised to d + 1 dimensions, characterising the mathematical structure of the resulting transport coefficient expressions.
The last part of the talk will be a discussion on the more involved sound sector, for which I will present results for the transport coefficients associated with the sound mode living on the 3-dimensional CFT.

Marina David: No Love for Quantum Black Holes

We investigate quantum corrections to the tidal Love numbers of near-extremal Reissner-Nordström black holes. In the near-extremal regime, the black hole develops a long AdS2 throat whose low-energy dynamics are governed by the Schwarzian action and whose quantum fluctuations become parametrically large at low temperatures. We consider the tidal response to an external scalar field probing the mouth of this throat and compute the quantum-corrected Green's function, extracting both static and dissipative Love numbers. We find that the scalar Love numbers vanish, to all orders in ℏ, providing a non-trivial quantum extension of the classical result.

Coffee break

Wednesday 18 March

Coffee break

Vania Vellucci: Regular black holes perturbations

Spacetime singularities are expected to be resolved in a complete (quantum) theory of gravity. Assuming that compact objects can still be described within a spacetime framework, such regularization may give rise to various classes of regular black hole mimickers. In this talk, I will discuss their possible structures and show how perturbation theory can be used to analyze their stability and potential phenomenological signatures.

Talk: Sašo Grozdanov

Coffee break

Thursday 19 March

Coffee break

Thomas Mertens: Quantum groups in lower-dimensional gravity models

In this talk I will discuss recent progress in uncovering the presence of quantum group symmetries in both 2d and 3d gravity models. This structure is then utilized to better understand various aspects of gravitational models, such as the structure of boundary correlation functions and quasi-normal modes, and edge states at the black hole horizon. Largely based on 2507.13873 and 2505.00501.

Francesco Aprile: Dynamics of Heavy Operators

Coffee break

Discussion session: Michal Heller, Giuseppe Policastro

Friday 20 March

Pablo Cano: Amplification of new physics in the QNM spectrum of highly rotating black holes

The computation of quasinormal modes of rotating black holes in modified theories of gravity has recently been achieved thanks to the development of new techniques, like a modified Teukolsky equation and spectral methods. However, the case of highly rotating black holes — close to extremality — remains challenging. In this talk, I will address this question in a quartic-curvature extension of GR that preserves QNM isospectrality in the eikonal regime. I will show that such property implies that large-momentum gravitational perturbations can be described by an effective scalar equation. By solving it with WKB methods, we obtain the corrections to the Kerr eikonal QNMs for arbitrary rotation in a fully analytic way. For moderate rotation, we check that the eikonal computation gives a good approximation to the exact QNMs obtained from the modified Teukolsky equation, even for low harmonics. For high rotation, we discover that the corrections to GR become much larger and can lead to dramatic effects. Our results suggest that the observation of the ringdown of a highly rotating black hole would be a “golden event” to search for new physics.

Coffee break

Laura Donnay: Null infinity and the black hole horizon: new conserved quantities for gravitational perturbations from a geometric duality

I will present a unified treatment for the boundary geometry of asymptotically flat spacetimes and black hole horizons. This geometric duality implies an exact inversion isometry for extremal, non-rotating horizons, which will be used to relate and derive new infinite towers of conserved quantities. This is a work in collaboration with Shreyansh Agrawal and Panagiotis Charalambous.

Coffee break