14 research outputs found
The Anti-de Sitter Gott Universe: A Rotating BTZ Wormhole
Recently it has been shown that a 2+1 dimensional black hole can be created
by a collapse of two colliding massless particles in otherwise empty anti-de
Sitter space. Here we generalize this construction to the case of a non-zero
impact parameter. The resulting spacetime, which may be regarded as a Gott
universe in anti-de Sitter background, contains closed timelike curves. By
treating these as singular we are able to interpret our solution as a rotating
black hole, hence providing a link between the Gott universe and the BTZ black
hole. When analyzing the spacetime we see how the full causal structure of the
interior can be almost completely inferred just from considerations of the
conformal boundary.Comment: 46 pages (LaTeX2e), 13 figures (eps
Aboriginal Australian mitochondrial genome variation - An increased understanding of population antiquity and diversity
Aboriginal Australians represent one of the oldest continuous cultures outside Africa, with evidence indicating that their ancestors arrived in the ancient landmass of Sahul (present-day New Guinea and Australia) ∼55 thousand years ago. Genetic studies, though limited, have demonstrated both the uniqueness and antiquity of Aboriginal Australian genomes. We have further resolved known Aboriginal Australian mitochondrial haplogroups and discovered novel indigenous lineages by sequencing the mitogenomes of 127 contemporary Aboriginal Australians. In particular, the more common haplogroups observed in our dataset included M42a, M42c, S, P5 and P12, followed by rarer haplogroups M15, M16, N13, O, P3, P6 and P8. We propose some major phylogenetic rearrangements, such as in haplogroup P where we delinked P4a and P4b and redefined them as P4 (New Guinean) and P11 (Australian), respectively. Haplogroup P2b was identified as a novel clade potentially restricted to Torres Strait Islanders. Nearly all Aboriginal Australian mitochondrial haplogroups detected appear to be ancient, with no evidence of later introgression during the Holocene. Our findings greatly increase knowledge about the geographic distribution and phylogenetic structure of mitochondrial lineages that have survived in contemporary descendants of Australia's first settlers. © The Author(s) 2017
From Geometry to Numerics: interdisciplinary aspects in mathematical and numerical relativity
This article reviews some aspects in the current relationship between
mathematical and numerical General Relativity. Focus is placed on the
description of isolated systems, with a particular emphasis on recent
developments in the study of black holes. Ideas concerning asymptotic flatness,
the initial value problem, the constraint equations, evolution formalisms,
geometric inequalities and quasi-local black hole horizons are discussed on the
light of the interaction between numerical and mathematical relativists.Comment: Topical review commissioned by Classical and Quantum Gravity.
Discussion inspired by the workshop "From Geometry to Numerics" (Paris, 20-24
November, 2006), part of the "General Relativity Trimester" at the Institut
Henri Poincare (Fall 2006). Comments and references added. Typos corrected.
Submitted to Classical and Quantum Gravit