Black holes in a box: towards the numerical evolution of black holes in AdS

The evolution of black holes in "confining boxes" is interesting for a number of reasons, particularly because it mimics the global structure of Anti-de Sitter geometries. These are non-globally hyperbolic space-times and the Cauchy problem may only be well defined if the initial data is supplemented by boundary conditions at the time-like conformal boundary. Here, we explore the active role that boundary conditions play in the evolution of a bulk black hole system, by imprisoning a black hole binary in a box with mirror-like boundary conditions. We are able to follow the post-merger dynamics for up to two reflections off the boundary of the gravitational radiation produced in the merger. We estimate that about 15% of the radiation energy is absorbed by the black hole per interaction, whereas transfer of angular momentum from the radiation to the black hole is only observed in the first interaction. We discuss the possible role of superradiant scattering for this result. Unlike the studies with outgoing boundary conditions, both the Newman-Penrose scalars \Psi_4 and \Psi_0 are non-trivial in our setup, and we show that the numerical data verifies the expected relations between them.Comment: REvTex4, 17 pages, 12 Figs. v2: Minor improvements. Published version. Animation of a black hole binary in a box can be found at http://blackholes.ist.utl.pt

Black hole binaries: ergoregions, photon surfaces, wave scattering, and quasinormal modes

Closed photon orbits around isolated black holes are related to important aspects of black hole physics, such as strong lensing, absorption cross section of null particles and the way that black holes relax through quasinormal ringing. When two black holes are present -- such as during the inspiral and merger events of interest for gravitational-wave detectors -- the concept of closed photon orbits still exists, but its properties are basically unknown. With these applications in mind, we study here the closed photon orbits of two different static black hole binaries. The first one is the Majumdar-Papapetrou geometry describing two extremal, charged black holes in equilibrium, while the second one is the double sink solution of fluid dynamics, which describes (in a curved-spacetime language) two "dumb" holes. For the latter solution, we also characterize its dynamical response to external perturbations, and study how it relates to the photon orbits. In addition, we compute the ergoregion of such spacetime and show that it does not coincide with the event horizon.Comment: 13 pages, 11 figures. v3: minor edits, to appear in Physical Review

Higher dimensional Numerical Relativity: code comparison

The nonlinear behavior of higher dimensional black hole spacetimes is of interest in several contexts, ranging from an understanding of cosmic censorship to black hole production in high-energy collisions. However, nonlinear numerical evolutions of higher dimensional black hole spacetimes are tremendously complex, involving different diagnostic tools and "dimensional reduction methods". In this work we compare two different successful codes to evolve Einstein's equations in higher dimensions, and show that the results of such different procedures agree to numerical precision, when applied to the collision from rest of two equal-mass black holes. We calculate the total radiated energy to be E/M=9x10^{-4} in five dimensions and E/M=8.1x10^{-4} in six dimensions.Comment: 7 pages, RevTex

A Double Myers-Perry Black Hole in Five Dimensions

Using the inverse scattering method we construct a six-parameter family of exact, stationary, asymptotically flat solutions of the 4+1 dimensional vacuum Einstein equations, with U(1)^2 rotational symmetry. It describes the superposition of two Myers-Perry black holes, each with a single angular momentum parameter, both in the same plane. The black holes live in a background geometry which is the Euclidean C-metric with an extra flat time direction. This background possesses conical singularities in two adjacent compact regions, each corresponding to a set of fixed points of one of the U(1) actions in the Cartan sub-algebra of SO(4). We discuss several aspects of the black holes geometry, including the conical singularities arising from force imbalance, and the torsion singularity arising from torque imbalance. The double Myers-Perry solution presented herein is considerably simpler than the four dimensional double Kerr solution and might be of interest in studying spin-spin interactions in five dimensional general relativity.Comment: 23 pages, 7 figures, LaTeX. v2: minor changes, references added; version published in JHE

Black holes in a box

The evolution of BHs in "confining boxes" is interesting for a number of reasons, particularly because it mimics some aspects of anti-de Sitter spacetimes. These admit no Cauchy surface and are a simple example of a non-globally hyperbolic spacetime. We are here interested in the potential role that boundary conditions play in the evolution of a BH system. For that, we imprison a binary BH in a box, at which boundary we set mirror-like boundary conditions. © 2010 IOP Publishing Ltd

Middle Palaeolithic flint procurement in Central Mediterranean Iberia: IMplications for human mobility.

Different flint types from the Middle Palaeolithic site of Abrigo de la Quebrada (Chelva, Valencia) are characterized, both macro- and microscopically, and compared with types found at other localities in the region. Although procurement predominantly concerned the immediate vicinity of sites, our results show the presence of the same types in assemblages separated by distances of up to 120 km. The long distances involved are suggestive of a pattern of North-South mobility of human groups along the coastline of central Mediterranean Iberia

La ocupación solutrense del Abrigo de la Boja (Mula, Murcia, España)

El relleno pleistoceno del Abrigo de la Boja (ADB) empieza con un nivel adscrito al Magdaleniense superior, seguido de un potente paquete con ocupación difusa bajo el cual se desarrolla una secuencia depositada durante el último máximo glacial caracterizada por una serie de estructuras de combustión, de tipo hogar plano/amorfo (open hearth), existiendo también hogares de cubeta. Destaca un hogar enlosado, completo y muy bien conservado, excavado en 2012 y adscrito provisionalmente al Solutreogravetiense. Los niveles solutrenses subyacentes son ricos en elementos de adorno, entre los cuales conchas perforadas de Littorina obtusata y Smaragdia viridis; su industria lítica incluye raspadores, algunas puntas, y escasos buriles. La datación 14C de muestras de carbón de Juniperus sp. sitúa este paquete entre 16990 ± 70 BP (VERA-5364a), a techo, y 20980 ± 120 BP (VERA-5366), a muro. The Pleistocene fill of the La Boja rock shelter (ADB) starts with an Upper Magdalenian level, followed by a thick package with poorly defined occupations under which there is a Last Glacial Maximum sequence with combustion features, mostly of the open hearth type. A particularly well preserved and seemingly complete stone-paved hearth of probable Solutreogravettian age was excavated in 2012. The abundant ornaments in the Solutrean levels include pierced Littorina obtusata and Smaragdia viridis shells and the stone tool assem- blages feature endscrapers, some points and rare burins. The 14C dating of Juniperus sp. charcoal samples places this sequence between 16990 ± 70 BP (VERA-5364a), at the top, and 20980 ± 120 BP (VERA-5366), at the bottom