Gravity: Challenges beyond General Relativity

Session

Gongshow

22 May 2024, 16:30

Sala de Graus Eduard Fontseré (UB Physics Faculty)

54. Perturbation of slowly evolving black holes: quasi-normal modes and tidal response

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
a significant impact on astrophysical observables like the inspiral or ringdown signal. An effective
description of a spherically symmetric evolving black hole is...

21. Thermodynamics of black holes featuring primary scalar hair

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...

45. The non-spherical ground state of Proca stars

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...

20. Ringdowns for black holes with scalar hair: the large mass case

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...

44. Anomaly-induced Inflation in the Minimal Quartic Extension of Einstein’s Gravity

Kerim Demirel

22/05/2024, 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...

52. The entropy of non-smooth black holes

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...

55. Cosmological Constrains on 4-dimensional Einstein-Gauss-Bonnet Gravity

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...

29. Exact black holes in string-inspired Euler-Heisenberg theory

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
black-hole solution, in the presence of non-trivial dilaton configurations. Specifically, by considering the gravitational theory of Euler-Heisenberg non-linear electrodynamics...

36. Dynamics, hyperbolicity and singularities in spherically symmetric massive gravity

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...

31. Scalar-Induced Gravitational Waves probing cosmological models

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...

1. Black hole thermodynamics and boundary terms

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...

53. Ringdown of rotating black holes in higher-derivative gravity

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...

59. Light rings in stationary axisymmetric spacetimes: blind to the horizon's topology and able to coexist

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...

28. The Fate of Matter Fields in Metric-Affine Gravity

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...

56. Revisiting alpha prime corrections to heterotic two-charge black holes

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,...