scholarly journals Square Peg in a Circular Hole: Choosing the Right Ansatz for Isolated Black Holes in Generic Gravitational Theories

2021 ◽  
Vol 126 (24) ◽  
Author(s):  
Yiqi Xie ◽  
Jun Zhang ◽  
Hector O. Silva ◽  
Claudia de Rham ◽  
Helvi Witek ◽  
...  
2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Ben Craps ◽  
Marine De Clerck ◽  
Philip Hacker ◽  
Kévin Nguyen ◽  
Charles Rabideau

Abstract Out-of-time-order correlators (OTOCs) that capture maximally chaotic properties of a black hole are determined by scattering processes near the horizon. This prompts the question to what extent OTOCs display chaotic behaviour in horizonless microstate geometries. This question is complicated by the fact that Lyapunov growth of OTOCs requires nonzero temperature, whereas constructions of microstate geometries have been mostly restricted to extremal black holes.In this paper, we compute OTOCs for a class of extremal black holes, namely maximally rotating BTZ black holes, and show that on average they display “slow scrambling”, characterized by cubic (rather than exponential) growth. Superposed on this average power-law growth is a sawtooth pattern, whose steep parts correspond to brief periods of Lyapunov growth associated to the nonzero temperature of the right-moving degrees of freedom in a dual conformal field theory.Next we study the extent to which these OTOCs are modified in certain “superstrata”, horizonless microstate geometries corresponding to these black holes. Rather than an infinite throat ending on a horizon, these geometries have a very deep but finite throat ending in a cap. We find that the superstrata display the same slow scrambling as maximally rotating BTZ black holes, except that for large enough time intervals the growth of the OTOC is cut off by effects related to the cap region, some of which we evaluate explicitly.


2012 ◽  
Vol 466-467 ◽  
pp. 1000-1005 ◽  
Author(s):  
Yan Li ◽  
Jun Bin Cao ◽  
Xiao Lei Li

In order to study the effect of patch shape on the strength of the damaged skin after rivet repair, the paper uses the elastic-plastic finite element method to analyze the rivet repair of the circular hole damage and gives the rivet loads of all the rivets under the three shapes of patches respectively. The results show that the circular patch can observably improve the strength of the aircraft skin after rivet repair, compared with the right-angled rectangle patch and the fillet-rectangle patch, in the same condition of the patch materials and rivet parameters and technology equipments. The design can enhance the security of the repaired aircraft and have some values for the peacetime repair and the emergent repair of aircraft structure.


1993 ◽  
Vol 08 (18) ◽  
pp. 1701-1718 ◽  
Author(s):  
AVINASH DHAR ◽  
GAUTAM MANDAL ◽  
SPENTA R. WADIA

We further study the non-perturbative formulation of two-dimensional black holes. We find a nonlinear differential equation satisfied by the tachyon in the black hole background. We show that singularities in the tachyon field configurations are always associated with divergent semiclassical expansions and are absent in the exact theory. We also discuss how the Euclidean black hole emerges from an analytically continued fermion theory that corresponds to the right side up harmonic oscillator potential.


2013 ◽  
Vol 28 (12) ◽  
pp. 1350035 ◽  
Author(s):  
D. L. BENNETT ◽  
L. V. LAPERASHVILI ◽  
H. B. NIELSEN ◽  
A. TUREANU

We present several theories of four-dimensional gravity in the Plebanski formulation, in which the tetrads and the connections are the independent dynamical variables. We consider the relation between different versions of gravitational theories: Einsteinian, "topological," "mirror" gravities and gravity with torsion. We assume that our world, in which we live, is described by the self-dual left-handed gravity, and propose that if the Mirror World exists in Nature, then the "mirror gravity" is the right-handed antiself-dual gravity. In this connection, we give a brief review of gravi-weak unification models. In accordance with cosmological measurements, we consider the Universe with broken mirror parity. We also discuss the problems of cosmological constant and communication between visible and mirror worlds. Investigating a special version of the Riemann–Cartan space–time, which has torsion as an additional geometric property, we have shown that in the Plebanski formulation the ordinary and dual "topological" sectors of gravity, as well as the gravity with torsion, are equivalent. Equations of motion are obtained. In this context, we have also discussed a "pure connection gravity" — a diffeomorphism-invariant gauge theory of gravity. Loop Quantum Gravity is also briefly reviewed.


2007 ◽  
Vol 21 (23n24) ◽  
pp. 3990-3992 ◽  
Author(s):  
HOI-LAI YU

We have shown that terms in the action which won't contribute to local equation of motions do contribute to globally conversed physical quantities in classical theories of gravity due to general coordinate covariance. This observation allows one to determining the Immirzi parameter in the Ashtekar variable formulation of gravitational theories even at classical level. Applying Wald's Noether charge approach and identifying the entropy on black hole horizon as the Noether charge for translation, one can demonstrate explicitly that the Immirzi parameter does make its contributions through the boundary term. Our results also shed lights in connecting the Immirzi paramter to quasi-normal modes of black holes.


2003 ◽  
Vol 12 (09) ◽  
pp. 1699-1704 ◽  
Author(s):  
EUN-JOO AHN ◽  
MARCO CAVAGLIÀ

Production of high-energy gravitational objects is a common feature of gravitational theories. The primordial universe is a natural setting for the creation of black holes and other nonperturbative gravitational entities. Cosmic black holes can be used to probe physical properties of the very early universe which would usually require the knowledge of the theory of quantum gravity. They may be the only tool to explore thermalization of the early universe. Whereas the creation of cosmic black holes was active in the past, it seems to be negligible at the present epoch.


2018 ◽  
Vol 27 (07) ◽  
pp. 1850074 ◽  
Author(s):  
G. G. L. Nashed

Motivated by the substantial modifications of gravitational theories and by the models that come out of [Formula: see text], we apply the field equation of the charged [Formula: see text] as well as a general vector potential containing three unknown functions to two spherically symmetric spacetimes. We solve the output of the differential equations and derive a class of black holes that are electrically and magnetically rotating spacetimes. The asymptotic behavior of these black holes acts as anti-de Sitter spacetime. Moreover, these solutions have asymptotic curvature singularities as those of General Relativity. We investigate this by calculating the invariants of curvature. Also, we address the issue of the energy conditions and show that the strong energy condition is satisfied provided [Formula: see text]. Finally, we compute the conserved quantities like mass and angular momentum.


2021 ◽  
Vol 34 (70) ◽  
pp. 103-131
Author(s):  
Alexsandro Rodrigues ◽  
Leonardo Lemos De Souza

Por uma política de leitura aberta de mundos: o buraco negro e o fim do mundo como possibilidade de nascimentos crianceiros Resumo: Este artigo é resultado de conversas afiadas e tecidas nos inconformismos e rebeldias desde as margens dos buracos negros de vidas em dissidências. O texto busca tensionar os buracos fechados pela polícia do sistema sexo-gênero na manutenção de seus privilégios e que não nos permite, via políticas públicas, acessar histórias em gêneros e sexualidades diferentes das tradicionais narrativas feitas para meninos e meninas de um certo tipo. Há subjetividades circulando entre nós nos espaços educativos que convocam os corpos, os gêneros e as sexualidades ao direito de nascerem, crescerem, florescerem e coabitarem o mundo, as escolas, as memórias e as narrativas hegemônicas das políticas curriculares na literatura infanto-juvenil. Exercitando perguntas que não se conformam com as histórias contadas, apresentadas e curricularizadas diariamente, o artigo faz problema sobre os modos de ler heterocêntricos que privilegiam o cérebro. Propõe, então, leituras buraco-negro. Estas apostas políticas, feitas de políticas anais e suas revoluções, buscam despreguear as relações de poder e as literaturas. Palavras-chave: Leitura como atividade. Gênero e sexualidade. Buracos negros. For an open world reading policy: the black hole and the end of the world as a possibility for births of childhoods Abstract: This article is the result of sharp conversations woven into nonconformities and rebellion from the margins of black holes in dissenting lives. The text seeks to tension the holes closed by the sex-gender police in maintaining their privileges and that does not allow us, through public policy, to access stories in genres and sexualities different from traditional narratives made for boys and girls of a certain type. There are subjectivities circulating among us in the educational spaces that call the bodies, genders and sexualities to the right to be born, grow, flourish and cohabit the hegemonic world, schools, memories and narratives of curriculum policies in children's literature. Exercising questions that do not conform to the stories told, presented and curricularized daily, the article questions the heterocentric ways of reading that privilege the brain. It then proposes black hole readings. These political bets, made up of anal politics and their revolutions, seek to unravel power relations and literatures. Keywords: Reading as an activity. Gender and sexuality. Black holes. Por una política de lectura de mundo abierto: el agujero negro y el fin del mundo como posibilidad para el nascimiento de las infâncias Resumen: Este artículo es el resultado de conversaciones agudas entretejidas en no conformidades y rebeliones desde los márgenes de los agujeros negros en vidas disidentes. El texto busca tensar los agujeros cerrados por la policía de género y sexo para mantener sus privilegios y eso no nos permite, a través de políticas públicas, acceder a historias de géneros y sexualidades diferentes a las narrativas tradicionales hechas para niños y niñas de cierto tipo. Hay subjetividades que circulan entre nosotros en los espacios educativos que llaman a los cuerpos, los géneros y las sexualidades al derecho a nacer, crecer, florecer y convivir con el mundo hegemónico, las escuelas, los recuerdos y las narrativas de las políticas curriculares en la literatura infantil. Ejercitando preguntas que no se ajustan a las historias contadas, presentadas y curriculadas diariamente, el artículo cuestiona las formas heterocéntricas de lectura que privilegian el cerebro. Luego propone lecturas de agujeros negros. Estas apuestas políticas, formadas por políticas anales y sus revoluciones, buscan desentrañar las relaciones de poder y la literatura. Palavras clave: Lectura como actividad. Género y sexualidad. Agujeros negros. Data de registro:  11/12/2019 Data de aceite: 26/08/2020


2017 ◽  
Vol 13 (S338) ◽  
pp. 40-45
Author(s):  
Astrid Lamberts

AbstractThe LIGO/Virgo detections of gravitational waves from merging black holes of ≃ 30 solar mass suggest progenitor stars of low metallicity (Z/Z⊙≲ 0.3). In this talk I will provide constrains on where the progenitors of GW150914 and GW170104 may have formed, based on advanced models of galaxy formation and evolution combined with binary population synthesis models. First I will combine estimates of galaxy properties (star-forming gas metallicity, star formation rate and merger rate) across cosmic time to predict the low redshift BBH merger rate as a function of present day host galaxy mass, formation redshift of the progenitor system and different progenitor metallicities. I will show that the signal is dominated by binaries formed at the peak of star formation in massive galaxies with and binaries formed recently in dwarf galaxies. Then, I will present what very high resolution hydrodynamic simulations of different galaxy types can learn us about their black hole populations.


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