Seventeenth Marcel Grossmann Meeting

Session

Gravitational instantons and black holes

BH1

12 Jul 2024, 15:00

Aurum, the ‘Gabriele d’Annunzio’ University and ICRANet

Conveners

Gravitational instantons and black holes: Friday block 1

• Reinoud Slagter (ASFYON, Astronomisch Fysisch Onderzoek Nederland)

Gravitational instantons and black holes: Friday block 2

• Reinoud Slagter (ASFYON, Astronomisch Fysisch Onderzoek Nederland)

Description

This parallel session covers instanton solutions on pseudo-Riemannian and Riemannian spacetime. These solutions originate from quantum field theory on Euclidean space, e.g. from Yang-Mills gauge theories. Their connections/curvatures are self-dual. In gravity, there are a handful of exact solutions. They have vanishing classical action and nontrivial topological invariant. The relation to quantum gravity is then easy. One can also relate these solutions to (primordial) black holes. After the discovery of black holes in the very early stages of the universe, the question arises as to how they came into being. Probably by an instanton. On the other hand, when a black hole evaporates completely, what is left behind? Related subjects: Kähler manifold, complex manifolds, symplectic structure, n-instanton moduli spaces.

388. Non-perturbative quantum gravity denounces singular Black Holes

Prof. Anna Tokareva (Hangzhou Institute for Advanced Study & ICTP-AP Centre Beijing/Hangzhou)

12/07/2024, 15:00

Gravitational instantons and black holes

Talk in a parallel session

Although General Relativity predicts the presence of a singularity inside of a Black Hole, it is not a complete theory of gravity. A real structure of a Black Hole interior near an expected singularity depends on the UV completion of gravity. In this paper, we establish that the question whether singular spherically symmetric solutions are absent is governed by the functional form of a...

1. Probing deviations to Kerr geometry with extreme mass-ratio inspirals

Dr Shailesh Kumar (Indian Institute of Technology Gandhinagar)

12/07/2024, 15:20

Gravitational instantons and black holes

Invited talk in a parallel session

One of the primary research aims of the Laser Interferometer Space Antenna (LISA) mission is to comprehensively map the Kerr spacetime, a fundamental pursuit in the realm of general relativity. To achieve this goal, it is essential to develop precise tools capable of discerning any deviations from the Kerr geometry. Extreme mass-ratio inspirals (EMRIs) stand out as particularly promising...

123. Energy formula, surface geometry and energy extraction for Kerr-Sen black hole

PARTHA PRATIM PRADHAN (HIRALAL MAZUMDAR MEMORIAL COLLEGE FOR WOMEN)

12/07/2024, 15:40

Gravitational instantons and black holes

Talk in a parallel session

We evaluate the surface energy~(${\mathcal{E}}_s^{\pm }$), rotational energy~(${\mathcal{E}}_r^{\pm }$) and electromagnetic energy~(${\mathcal{E}}_{em}^{\pm }$) for a Kerr-Sen black hole~(BH) having the event horizon~(${\mathcal{H}}^{+}$) and the Cauchy horizon~(${\mathcal{H}}^{-}$).
Interestingly, we find that the sum of these three energies is equal to the mass parameter i.e. ${\cal E}_{s}^{\pm}+{\cal...

66. Testing black hole with electromagnetic perturbations

Bobir Toshmatov (New Uzbekistan University)

12/07/2024, 16:00

Gravitational instantons and black holes

Talk in a parallel session

It is a well-known fact that light rays do not follow the null geodesics of spacetime, instead, they propagates along the null geodesics of the effective spacetime. In my presentation, we discuss the construction of the effective spacetime by studying the electromagnetic perturbations of black holes in general relativity coupled with nonlinear electrodynamics. Additionally, we explore the...

211. Multi-Black Hole Gravitational Field

Eliska Klimesova (Institute of Theoretical Physics, Charles University Prague, Czech Republic)

12/07/2024, 17:00

Gravitational instantons and black holes

Talk in a parallel session

We shall discuss a system consisting of three extremally charged black holes moving in their own gravitational and electromagnetic fields. Based on a method by Ferrell & Eardley for an arbitrary number of holes, we take the exact static Majumdar-Papapetrou spacetime, and perturb it by giving the holes small velocities.

Suprisingly, the complicated equations can be reduced to a classical...

6. Calculating quasinormal modes of extremal and non-extremal Reissner-Nordström black holes with the continued fraction method

Ramin Daghigh (Metropolitan State University)

12/07/2024, 17:20

Gravitational instantons and black holes

Invited talk in a parallel session

We use the numerical continued fraction method to investigate quasinormal mode spectra of extremal and non-extremal Reissner-Nordström black holes in the low and intermediate damping regions. In the extremal case, we develop techniques that significantly expand the calculated spectrum from what had previously appeared in the literature. This allows us to determine the asymptotic behavior of...

374. Analyzing Shadows of Naked Singularities and Black Holes

Ms Aray Muratkhan (Al farabi Kazakh National University), Saken Toktarbay (Al-Farabi Kazakh National University)

12/07/2024, 17:40

Gravitational instantons and black holes

Talk in a parallel session

We investigate the shadows produced by naked singularity spacetimes. Most analytical solutions for black hole shadows have focused on scenarios where the geodesic equations for photons. We examine the spherical null naked singularity metric, which is a spherically symmetric solution to Einstein's equations. Additionally, we consider a static, axially symmetric singular solution of the vacuum...

137. Entropy Product Function and Central charges in NUT Geometry

PARTHA PRATIM PRADHAN (HIRALAL MAZUMDAR MEMORIAL COLLEGE FOR WOMEN)

12/07/2024, 18:00

Gravitational instantons and black holes

Talk in a parallel session

We define an entropy product function (EPF) for Taub-Newman-Unti-Tamburino(TNUT) black hole(BH) following the prescription suggested by Wu et al. [PRD 100, 101501(R) (2019)].
The prescription argues that a generic four-dimensional TNUT spacetime might be expressed in terms of three or four different types of thermodynamic hairs. They can be defined as the Komar mass($M=m$), the angular...

171. Accretion flows around spinning compact objects in the post-Newtonian regime

Samik Mitra (Indian Institute of Technology Guwahati)

12/07/2024, 18:20

Gravitational instantons and black holes

Talk in a parallel session

We present the structure of a low angular momentum accretion flows around rotating compact objects incorporating relativistic corrections up to the leading post-Newtonian order. To begin with, we formulate the governing post-Newtonian hydrodynamic equations for the mass and energy-momentum flux without imposing any symmetries. However, for the sake of simplicity, we consider the flow to be...