315 research outputs found
Mass inflation in a D dimensional Reissner-Nordstrom black hole: a hierarchy of particle accelerators ?
We study the geometry inside the event horizon of perturbed D dimensional
Reissner-Nordstrom-(A)dS type black holes showing that, similarly to the four
dimensional case, mass inflation also occurs for D>4. First, using the
homogeneous approximation, we show that an increase of the number of spatial
dimensions contributes to a steeper variation of the metric coefficients with
the areal radius and that the phenomenon is insensitive to the cosmological
constant in leading order. Then, using the code reported in arXiv:0904.2669
[gr-qc] adapted to D dimensions, we perform fully non-linear numerical
simulations. We perturb the black hole with a compact pulse adapting the pulse
amplitude such that the relative variation of the black hole mass is the same
in all dimensions, and determine how the black hole interior evolves under the
perturbation. We qualitatively confirm that the phenomenon is similar to four
dimensions as well as the behaviour observed in the homogeneous approximation.
We speculate about the formation of black holes inside black holes triggered by
mass inflation, and about possible consequences of this scenario.Comment: 8 pages, 6 figure
Nota sobre la taxonomía de Microtus (Iberomys) (Arvicolinae, Rodentia) del Pleistoceno superior de la Gruta do Caldeirão (Tomar, Portugal) e interpretación paleoclimática de la asociación de roedores
Gruta do Caldeirão is an archaeological cave site located in Tomar (Portugal, western Iberian Peninsula), which contains an important Late Pleistocene sequence from Middle Paleolithic (Mousterian) to Upper Paleolithic (Solutrean-Magdalenian), including lithic tools, human remains, and other large- and small-vertebrate remains. Our revision and interpretation of the rodent assemblage previously published in the 1990s leads to three important conclusions: 1) the only species of the subgenus Iberomys present in the sequence is the current endemic Iberian vole species Microtus (Iberomys) cabrerae (Cabrera’s vole); 2) the rodent assemblage is dominated throughout by open-forest species, such as the long-tailed field mouse (Apodemus sylvaticus), and species associated with open-humid areas such as the Mediterranean and Lusitanian pine voles (Microtus (Terricola) spp.), with the notable presence of an extinct hamster (Allocricetus bursae) in layer K, and three vole species not currently found in the vicinity of the cave (Microtus arvalis [the common vole], M. Agrestis [the field vole], and Chionomys nivalis [the European snow vole]) also in the assemblage; 3) the bioclimatic model, which is used to reconstruct climatic parameters on the basis of the rodent association, corroborates the proposal that the Solutrean occupation from layers H to Fa took place during a cold period equated to the Last Glacial Maximum (LGM), as indicated by the available radiocarbon dates and supported by the magnetic susceptibility data.Gruta do Caldeirão es un yacimiento arqueológico en cueva situado en Tomar (Portugal, oeste de la península Ibérica), que contiene una importante secuencia perteneciente al Pleistoceno superior, adscrita culturalmente al Paleolítico medio (Musteriense) y Paleolítico superior (Solutrense-Magdaleniense), que incluye industria lítica, restos humanos y restos de grandes y pequeños vertebrados. La revisión e interpretación de la asociación de roedores de la secuencia, previamente publicada en los años 90 del siglo pasado, nos ha permitido remarcar tres importantes conclusiones: 1) la única especie del subgénero Iberomys presente en la secuencia es la especie endémica actual de topillo Microtus (Iberomys) cabrerae (topillo de Cabrera); 2) la asociación de roedores está dominada en toda la secuencia por especies relacionadas con bosques abiertos, como el ratón de campo (Apodemus sylvaticus) y especies relacionadas con espacios abiertos-húmedos como los topillos mediterráneo y lusitánico (Microtus (Terricola) spp.), remarcando la presencia de un hámster extinto (Allocricetus bursae) en el nivel K y tres especies de topillos que no tienen representación actual en la zona circundante a la cavidad (Microtus arvalis - topillo campesino, Microtus agrestis – topillo agreste y Chionomys nivalis - topillo nival); 3) Finalmente, el método del Modelo Bioclimático, aplicado a la asociación de roedores, otorga resultados acordes con que la ocupaciones solutrenses situadas entre los niveles H y Fa están relacionadas con un periodo frío equiparado con el Último Máximo Glacial (LGM), indicado por las dataciones de radiocarbono y anteriores estudios de susceptibilidad magnética de la secuencia
Numerical relativity in higher dimensions
We give a status report on our project targeted at performing numerical simulations of a head-on collision of non-spinning black holes in higher dimensional non-compact space-times. These simulations should help us understand black objects in higher dimensions and their stability properties. They are also relevant for the problem of black hole formation and evaporation in particle accelerators and cosmic rays. We use the symmetries of the system to reduce the problem to an effective 3+1 problem, allowing the use of existing numerical codes. As a simple application of the formalism, we present the results for the evolution of a five dimensional single black hole space-time. © 2010 IOP Publishing Ltd
Modeling the role of voyaging in the coastal spread of the Early Neolithic in the West Mediterranean
The earliest dates for the West Mediterranean Neolithic indicate that it expanded across 2,500 km in about 300 y. Such a fast spread is held to be mainly due to a demic process driven by dispersal along coastal routes. Here, we model the Neolithic spread in the region by focusing on the role of voyaging to understand better the core elements that produced the observed pattern of dates. We also explore the effect of cultural interaction with Mesolithic populations living along the coast. The simulation study shows that (i) sea travel is required to obtain reasonable predictions, with a minimum sea-travel range of 300 km per generation; (ii) leapfrog coastal dispersals yield the best results (quantitatively and qualitatively); and (iii) interaction with Mesolithic people can assist the spread, but long-range voyaging is still needed to explain the archaeological pattern.info:eu-repo/semantics/publishedVersio
Head-on collisions of unequal mass black holes in D=5 dimensions
We study head-on collisions of unequal mass black hole binaries in D=5
space-time dimensions, with mass ratios between 1:1 and 1:4. Information about
gravitational radiation is extracted by using the Kodama-Ishibashi
gauge-invariant formalism and details of the apparent horizon of the final
black hole. For the first time, we present waveforms, total integrated energy
and momentum for this process. Our results show surprisingly good agreement,
within 5% or less, with those extrapolated from linearized, point-particle
calculations. Our results also show that consistency with the area theorem
bound requires that the same process in a large number of spacetime dimensions
must display new features.Comment: 10 pages, 5 figures, RevTex4. v2: Published versio
Addendum to “Strong cosmic censorship: The nonlinear story”
We clarify a number of issues that arise when extending the analysis of strong cosmic censorship (SCC) to perturbations of highly charged Reissner-Nordström de Sitter (RNdS) spacetimes. The linear stability of the Cauchy horizon can be determined from the spectral gap of quasinormal modes, thus giving a clear idea of the ranges of parameters that are likely to lead to SCC violations for infinitesimally small perturbations. However, the situation becomes much more subtle once the nonlinear backreaction is taken into account. These subtleties have created a considerable amount of confusion in the literature regarding the conclusions one is able to derive about SCC from the available numerical simulations. Here we present new numerical results concerning charged self-gravitating scalar fields in spherical symmetry, correct some previous claims concerning the neutral case, and argue that the existing numerical codes are insufficient to draw conclusions about the potential failure of SCC for near extremal RNdS black hole spacetimes.info:eu-repo/semantics/acceptedVersio
Numerical relativity for D dimensional axially symmetric space-times: formalism and code tests
The numerical evolution of Einstein's field equations in a generic background
has the potential to answer a variety of important questions in physics: from
applications to the gauge-gravity duality, to modelling black hole production
in TeV gravity scenarios, analysis of the stability of exact solutions and
tests of Cosmic Censorship. In order to investigate these questions, we extend
numerical relativity to more general space-times than those investigated
hitherto, by developing a framework to study the numerical evolution of D
dimensional vacuum space-times with an SO(D-2) isometry group for D\ge 5, or
SO(D-3) for D\ge 6.
Performing a dimensional reduction on a (D-4)-sphere, the D dimensional
vacuum Einstein equations are rewritten as a 3+1 dimensional system with source
terms, and presented in the Baumgarte, Shapiro, Shibata and Nakamura (BSSN)
formulation. This allows the use of existing 3+1 dimensional numerical codes
with small adaptations. Brill-Lindquist initial data are constructed in D
dimensions and a procedure to match them to our 3+1 dimensional evolution
equations is given. We have implemented our framework by adapting the LEAN code
and perform a variety of simulations of non-spinning black hole space-times.
Specifically, we present a modified moving puncture gauge which facilitates
long term stable simulations in D=5. We further demonstrate the internal
consistency of the code by studying convergence and comparing numerical versus
analytic results in the case of geodesic slicing for D=5,6.Comment: 31 pages, 6 figures; v2 Minor changes and added two references.
Matches the published version in PRD
The Reality of Neandertal Symbolic Behavior at the Grotte du Renne, Arcy-sur-Cure, France
The question of whether symbolically mediated behavior is exclusive to modern humans or shared with anatomically archaic populations such as the Neandertals is hotly debated. At the Grotte du Renne, Arcy-sur-Cure, France, the Châtelperronian levels contain Neandertal remains and large numbers of personal ornaments, decorated bone tools and colorants, but it has been suggested that this association reflects intrusion of the symbolic artifacts from the overlying Protoaurignacian and/or of the Neandertal remains from the underlying Mousterian
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