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Vitor Cardoso22/05/2024, 09:45
Precision gravitational-wave astronomy is under way, able to probe strong-field gravity to unprecedented levels. Which is the correct description of gravity, and of the matter content of the universe? I will not answer these questions, but will discuss some of the smoking-guns for the simplest extensions of General Relativity and of the Standard Model, in the context of black hole physics: new...
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Laura Sberna22/05/2024, 11:15
I will introduce a new method to study perturbations around black holes, using the black hole’s characteristic (quasinormal, quasibound or superradiant) modes. The new method hinges on a new relativistic product, under which modes are orthogonal. Using this product, one can derive the analog of time-dependent and independent perturbation theory in quantum mechanics. I will present a first...
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Mateja Boskovic (DESY)22/05/2024, 12:00
We show that the existence of clouds of ultralight particles surrounding black holes during their cosmological history as members of a binary system can leave a measurable imprint on the distribution of masses and orbital eccentricities observable with future gravitational-wave detectors. Notably, we find that for nonprecessing binaries with chirp masses < 10 solar masses, formed exclusively...
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Athanasios Bakopoulos (National Technical University of Athens)22/05/2024, 12:15
We analyse in all generality beyond Horndeski theories of shift symmetry in a static and spherically symmetric spacetime. By introducing four auxiliary functions, we write the field equations in a particularly compact form. We show that assuming additionally parity symmetry renders the system directly integrable giving multiple families of black-hole solutions. These have typically an...
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Theodoros Nakas (National Technical University of Athens)22/05/2024, 12:30
We present explicit black holes endowed with primary scalar hair within the shift-symmetric subclass of Beyond Horndeski theories. These solutions depend, in addition to the conventional mass parameter, on a second free parameter encoding primary scalar hair. The properties and characteristics of the solutions at hand are analyzed with varying scalar charge. We observe that when the scalar...
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Bayram Tekin22/05/2024, 14:30
For asymptotically constant curvature spaces, such as (A)dS, the conserved quantities depend not only on the geometry but also on the theory under consideration. I shall give a new construction of conserved charges both in cosmological Einstein's theory and generic f(Riemann) theories. The final expressions are in terms of the linearized Riemann tensor at the boundary of spacetime and are...
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Adolfo Cisterna22/05/2024, 15:15
This talk explores novel algebraically general black hole solutions by reevaluating Buchdahl transformations within Einstein and Einstein-Scalar theories. It investigates the relationship between Buchdahl transformations and Levi-Civita spacetimes when applied along a spacelike Killing vector of a given seed. By employing Kerr-Schild transformations, our study extends Buchdahl's theorem to...
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Lodovico Capuano (SISSA)22/05/2024, 16:30
The mass of a black hole can dynamically evolve due to various physical processes beyond vacuum General Relativity, such as accretion, Hawking radiation, superradiance or gravitational wave backreaction. This evolution can have
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a significant impact on astrophysical observables like the inspiral or ringdown signal. An effective
description of a spherically symmetric evolving black hole is... -
Nikos Chatzifotis (National Technical University of Athens)22/05/2024, 16:35
In this work, we embark on the thermodynamic investigation concerning a family of primary charged black holes within the context of shift and parity symmetric Beyond Horndeski gravity. Employing the Euclidean approach, we derive the functional expression for the free energy and derive the first thermodynamic law, offering a methodology to address the challenge of extracting the thermal...
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Etevaldo Costa (University of Aveiro)22/05/2024, 16:40
Spherical Proca Stars (PSs) are regarded as the ground state amongst the family of PSs. In accordance, spherical PSs are thought to have a fundamental branch of stable solutions. In this Letter, we provide energetic, morphological and dynamical evidence that spherical PSs are actually excited states. The ground state is shown to be a family of static, non-spherical, in fact prolate, PSs. The...
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Giovanni D'Addario (University of Nottingham)22/05/2024, 16:45
Deviations from General Relativity can be probed with black hole spectroscopy, as the quasi-normal mode (QNM) frequency spectrum of a black hole with additional ‘hair’ is expected to differ from that of a Kerr black hole. We construct an effective field theory scheme for QNMs to capture deviations from Kerr for black holes in theories with a coupling between a shift-symmetric scalar and the...
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Kerim Demirel22/05/2024, 16:50
The exploration of modified gravity theories using cosmology has gained considerable attention in recent years. In this context, we investigate anomaly-induced inflation within the framework of a Born-Infeld type modified gravity theory, which represents a minimal extension of Einstein's gravity. This theory, elaborated in recent works [1][2][3], exhibits intriguing properties, including a...
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Maxime Gadioux (University of Cambridge)22/05/2024, 16:55
In general relativity, dynamical black holes generically have non-smooth horizons. One can study the properties of the non-smooth structures that are stable under perturbations of the horizon. This analysis does not make use of the Einstein equations, and hence is potentially relevant to higher-derivative theories of gravity. We describe the possible non-smooth structures and discuss some...
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Brayden R. Hull (University of Waterloo)22/05/2024, 17:00
In the last few years the contribution of higher-curvature terms in modified gravity has received quite a lot of attention. This is due to the discovery of a 4-dimensional limit of Einstein-Gauss-Bonnet theory that has non-trivial contributions from the Gauss-Bonnet invariant. The theory is a very interesting phenomenological competitor to General Relativity insofar as it passes all...
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Thanasis Karakasis (National Technical University of Athens)22/05/2024, 17:05
We consider higher-order derivative gauge field corrections that arise in the fundamental context of dimensional reduction of String Theory and Lovelock-inspired gravities and obtain an exact and asymptotically flat
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black-hole solution, in the presence of non-trivial dilaton configurations. Specifically, by considering the gravitational theory of Euler-Heisenberg non-linear electrodynamics... -
Jan Kożuszek (Imperial College London)22/05/2024, 17:10
In modified theories of gravity, the question of well-posedness of their equations underlies any attempts at numerical simulations. These in turn are crucial for comparison with experimental data and possible confirmation of the theory’s predictions. In this talk, we will concentrate on ghost-free massive gravity, notable for being a genuine IR modification of general relativity. Through a...
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Anjali Abirami Kugarajh (Gran Sasso Science Institute)22/05/2024, 17:15
There are a few unanswered questions about standard cosmological model. An open question to answer is if we can use gravitational waves (GWs) to probe beyond General Relativity? Due to their weak interaction with matter, we hope to observe Primordial GWs which can give us a better understanding of the physics of the early Universe. Primordial GWs come in the form of a stochastic background...
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Marek Liška (Charles University, Prague)22/05/2024, 17:20
I discuss sensitivity of black hole thermodynamics to certain boundary terms in the gravitational action. In some cases, boundary terms can alter not only the black hole entropy but even its thermodynamic temperature. Remarkably, this behaviour is confirmed by both covariant phase space (Iyer-Wald) and Euclidean (Brown-York) methods. I demonstrate our results on the example of 4D scalar-tensor...
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Simon Maenaut (KU Leuven)22/05/2024, 17:25
We computed the spectrum of linearized gravitational excitations of black holes with substantial angular momentum in the presence of higher-derivative corrections to general relativity. We do so perturbatively to leading order in the higher-derivative couplings and to more than sixteen orders in the black hole angular momentum. This allows us to accurately predict quasi-normal mode frequencies...
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João Novo (Universidade de Aveiro)22/05/2024, 17:30
It is well established that black holes satisfying some quite general set of assumptions are always surrounded by a light ring. These are a special set of bound null orbits. Such orbits are of particular relevance when entering the new era of precision test of General Relativity, as they leave imprints on both gravitational wave observations, and on the black hole shadows, the two main new...
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Claire Rigouzzo (King's College London)22/05/2024, 17:35
General relativity (GR) exists in different formulations. They are equivalent in pure gravity but generically lead to distinct predictions once matter is included. After a brief overview of various versions of GR, I will focus on metric-affine gravity, which avoids any assumption about the vanishing of curvature, torsion, or nonmetricity. With a view toward the Standard Model, we can construct...
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Matteo Zatti (IFT UAM/CSIC)22/05/2024, 17:40
Based on: 2311.03308
Authors: Stefano Massai, Alejandro Ruiperez, Matteo Zatti
Abstact: We find solutions of the heterotic string effective action describing the first-order alpha prime corrections to two-charge black holes at finite temperature. Making explicit use of these solutions, we compute the corrections to the thermodynamic quantities: temperature, chemical potentials, mass,...
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David Kubiznak23/05/2024, 09:45
Using the framework of extended black hole thermodynamics, where the cosmological constant is one of the thermodynamic parameters and is allowed to vary in the first law, I will discuss some recent advances towards understanding the thermodynamic behavior of exotic black hole spacetimes, such as accelerated black holes or black holes equipped with the NUT parameter.
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Alejandro Ruipérez23/05/2024, 11:05
Holography allows us to address the microstate counting of AdS black holes from the dual CFT. Recently, a certain Cardy-like regime of the so-called superconformal index has been shown to single out the saddle which carries the Bekenstein-Hawking entropy of the dual supersymmetric AdS_5 black hole. In this talk I shall discuss how this match can be extended to account for corrections in the...
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Manus Visser (University of Cambridge)23/05/2024, 11:50
We study the first law for non-stationary perturbations of a stationary black hole whose event horizon is a Killing horizon, that relates the first-order change in the mass and angular momentum to the change in the entropy of an arbitrary horizon cross-section. Recently, Hollands, Wald and Zhang [1] have shown that the dynamical black hole entropy that satisfies this first law, for general...
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Marina David (KU Leuven)23/05/2024, 12:05
It is well known that in the semi-classical limit, the entropy of black holes is universally given by the Bekenstein-Hawking formula. There are in fact corrections to this formula arising from higher derivative terms in the gravitational path integral or quantum effects to due matter fields propagating on a fixed gravitational background. Evaluating such corrections is a challenging endeavor,...
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Leonardo Gualtieri23/05/2024, 14:15
Black holes are the perfect probes to understand the nature of the gravitational interaction: they are the simplest gravitating objects in the universe, and can generate the strongest gravitational fields. We shall discuss how black hole solutions and their behaviour are affected by modifications of general relativity, and how gravitational and electromagnetic signals from black holes can be...
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Katy Clough23/05/2024, 15:00
I will describe recent developments in numerical relativity that permit us to simulate non trivial scalar-tensor theories of gravity, which represent the next order corrections in an effective field theory approach. Whilst these techniques were developed mainly to aid the study of black holes spacetimes, they can also be applied to cosmology, in particular to the non linear dynamics of...
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Adria Delhom i Latorre23/05/2024, 15:45
In this talk we will explain how to quantify the entanglement generated in the Hawking process for rotating black holes iluminated by CMB radiation. We will show how ergoregions leave a specific signature in the entanglement structure of Hawking radiation, absent for Schwarzschild black holes. The formalism we develop applies for gravitational as well as analogue black holes. We will finish by...
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Nicola Franchini (APC)23/05/2024, 16:30
In this talk, I will summarize the recent advancements of quasi-normal modes in alternative theories of gravity. I will briefly explain the main issues in computing the characteristic frequencies of rotating black holes and what are the most prominent strategies to tackle this problem. The approaches covered include the slow-spin and small-coupling expansions. In particular, I will present a...
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Georgios Antoniou (INFN Rome)23/05/2024, 16:45
Various recent works have explored the emergence and properties of compact object solutions including black holes, in models with a metric tensor and a scalar field within the Horndeski framework of theories. Studying the quasinormal mode (QNM) spectrum of hairy black holes is particularly useful when considering the potential of observing hairy solutions in nature. In this talk we discuss how...
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Andrew Spiers (University of Nottingham)23/05/2024, 17:00
A key science target for LISA is testing General Relativity by measuring extreme-mass-ratio inspirals. Modelling such binaries with numerical relativity is not viable due to the disparate length scales. Perturbation theory comes to the rescue: leveraging the disparate length scales, we can model the binary using the self-force approach. Great effort is being expounded in pursuing high-accuracy...
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Alexandros Karam (NICPB, Tallinn)23/05/2024, 17:15
We present an introduction to cosmic inflation in the framework of Palatini gravity, which provides an intriguing alternative to the conventional metric formulation of gravity. In the latter, only the metric specifies the spacetime geometry, whereas in the former, the metric and the spacetime connection are independent variables-an option that can result in a gravity theory distinct from the...
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Ángel Jesús Murcia Gil (Istituto Nazionale di Fisica Nucleare, Sezione di Padova (Italia))23/05/2024, 17:30
In this talk I will present some classification results of higher-curvature gravities (in generic spacetime dimensions) satisfying a quite remarkable property: the differential order of their equations of motion gets reduced when considered on certain specific backgrounds. First, I will consider those higher-order gravities whose equations of motion become second-order (or less) on top of...
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Ruth Gregory24/05/2024, 09:45
A black hole is characterised by the event horizon, a boundary of information that can be accessed from that which cannot. Horizons can occur in a wide range of physical situations, many of which we can construct in the lab, leading to the field of Analog Gravity. Most gravity simulators observe features, like super-radiance, that are analysed as a continuum effect in gravity, whereas many...
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Andrew Svesko24/05/2024, 11:05
Semi-classical gravity is a useful proxy to study quantum effects in gravity. Yet, generically, consistent solutions to the semi-classical Einstein equations accounting backreaction remain out of reach, limiting our understanding of quantum corrections to black hole physics. In this talk, I review the construction of three-dimensional `quantum' black holes. Such spacetimes live on holographic...
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Ivan Kolar (Charles University)24/05/2024, 11:50
The covariant position-space propagators for GR in the Euclidean AdS background have been known for more than 25 years (partially even before the AdS/CFT). However, due to the complicated bi-tensorial structure of these quantities, no such explicit formulas have been presented in the literature for gravitational theories beyond GR. In this talk, I will describe a new method of construction of...
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Dr Gabriel Arenas-Henriquez (Tsinghua University)24/05/2024, 12:05
In this talk, we will focus on describing features of the C-metric in 2+1 dimensions. Starting from a general ansatz we construct three classes of geometries which can be interpreted by studying their physical parameters. From these, we identify stationary, accelerating point particles; one-parameter extensions of the BTZ family resembling an accelerating black hole; and a novel “accelerating...
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Jorge Rocha24/05/2024, 14:15
The collision of compact objects, such as black holes and neutron stars, is a spectacular cosmic event of great interest to gravitational wave astronomy. Since 2015 we have been gathering information about such binary systems through the observation of the gravitational waves they generate. Most of these detections —and the determination of the parameters of the binary that sourced the gravi-...
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Raúl Carballo-Rubio24/05/2024, 15:00
Black holes are arguably the most fascinating prediction of general relativity. These solutions of general relativity are singular and are therefore expected to be an approximation. One of the promises of quantum gravity is providing a complete and non-singular description of black holes. This complex task has been addressed by different groups using different bottom-up and top-down approaches...
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Mariano Chernicoff (Facultad de Ciencias, UNAM)24/05/2024, 15:45
We study the interplay between higher curvature terms and the backreaction of quantum fluctuations in 3-dimensional massive gravity in asymptotically (Anti-)de Sitter space. We focus on the theory at the special point of the parameter space where the two maximally symmetric vacua coincide. In the case of positive cosmological constant, this corresponds to the partially massless point, at which...
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David Pereñiguez (Niels Bohr Institute)24/05/2024, 16:30
Black hole superradiance has proven being very valuable in several realms of gravitational physics, and holds a promising discovery potential. In this talk I will show how it can sheed light on a long
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standing problem in physics, the quest for magnetic monopoles in the Universe. Placing them in the interior of primordial rotating black holes, which act as natural amplifiers, I will show that... -
Ryotaku Suzuki (Toyota Technological Institute)24/05/2024, 16:45
Black holes are not unique in higher dimensions. It is well known that, in five dimensions, stationary, biaxisymmetric black holes with the horizon of $S^3$-topology and $S^2 \times S^1$-topology can exist for the same asymptotic charges, in contrast to the black holes in four dimensions where the horizon must have $S^2$-topology.
In this talk, we aim to demonstrate that even if the horizon...
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Javier Moreno24/05/2024, 17:00
We show that, in general three-dimensional higher-curvature gravity, imposing a simple holographic c-theorem as well as a single vacuum allows for the existence of a family of hairy black hole solutions. These solutions, which exist in a special point in the theory space, correspond to a generalization of the usual the Bañados-Teitelboim-Zanelli black hole. We compute the thermodynamic...
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Pablo Bueno (ICCUB)24/05/2024, 17:15
I will show via an explicit construction how an infinite tower of higher-curvature corrections generically leads to the resolution of the Schwarzschild singularity in any spacetime dimension D≥5. The theories we consider have two key properties that ensure the results are general and robust: (1) they provide a basis for (vacuum) gravitational effective field theory in five and...
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Dr Ivan de Martino (Universidad de Salamanca)
The Galactic Center of the Milky Way can serve as a test bench to investigate physical phenomena at the edge of astrophysics and fundamental physics. As such, it offers a unique laboratory to probe General Relativity, modified theories of gravity, different paradigms of dark matter, and black hole mimickers. I will provide a general overview of the results achieved in recent years emphasizing...
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