Relativistic Gravitational Collapse of a Cylindrical Shell of Dust

The gravitational collapse of a thick cylindrical shell of dust matter is investigated. It is found that a spacetime singularity forms on the symmetry axis and that it is necessarily naked, i.e., observable in principle. We propose a physically reasonable boundary condition at this naked singularity to construct the solution including its causal future. This boundary condition enables us to construct the unique continuation of spacetime beyond the naked singularity and ensures that the dust shell passes through the naked singularity. When the cylindrical shell leaves its symmetry axis away, the naked singularity disappears, and regularity is recovered. We construct numerical solutions with this feature. This result implies that the gravity produced by a thick cylindrical shell of dust is too weak to bind the shell even if it engenders the formation of a curvature singularity which is so strong as to satisfy the limiting focusing condition. For this reason, this naked singularity is very weak in the extended spacetime; the metric tensor is $C^{1-}$ even at the naked singularity, and the extended spacetime is complete for almost all geodesics. This feature is also seen for singular hypersurfaces. Such an extended spacetime can be regarded as phenomenological in the sense that it is valid if the relevant microphysics length scale is sufficiently small compared to the scale of interest.Comment: 32 pages, 6 figure

The Japanese space gravitational wave antenna; DECIGO

DECi-hertz Interferometer Gravitational wave Observatory (DECIGO) is the future Japanese space gravitational wave antenna. DECIGO is expected to open a new window of observation for gravitational wave astronomy especially between 0.1 Hz and 10 Hz, revealing various mysteries of the universe such as dark energy, formation mechanism of supermassive black holes, and inflation of the universe. The pre-conceptual design of DECIGO consists of three drag-free spacecraft, whose relative displacements are measured by a differential Fabry– Perot Michelson interferometer. We plan to launch two missions, DECIGO pathfinder and pre- DECIGO first and finally DECIGO in 2024

The tremendous potential of deep-sea mud as a source of rare-earth elements

金沢大学理工研究域地球社会基盤学系Potential risks of supply shortages for critical metals including rare-earth elements and yttrium (REY) have spurred great interest in commercial mining of deep-sea mineral resources. Deep-sea mud containing over 5,000 ppm total REY content was discovered in the western North Pacific Ocean near Minamitorishima Island, Japan, in 2013. This REY-rich mud has great potential as a rare-earth metal resource because of the enormous amount available and its advantageous mineralogical features. Here, we estimated the resource amount in REY-rich mud with Geographical Information System software and established a mineral processing procedure to greatly enhance its economic value. The resource amount was estimated to be 1.2 Mt of rare-earth oxide for the most promising area (105 km2 × 0-10 mbsf), which accounts for 62, 47, 32, and 56 years of annual global demand for Y, Eu, Tb, and Dy, respectively. Moreover, using a hydrocyclone separator enabled us to recover selectively biogenic calcium phosphate grains, which have high REY content (up to 22,000 ppm) and constitute the coarser domain in the grain-size distribution. The enormous resource amount and the effectiveness of the mineral processing are strong indicators that this new REY resource could be exploited in the near future. © 2018 The Author(s)

DECIGO pathfinder

DECIGO pathfinder (DPF) is a milestone satellite mission for DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) which is a future space gravitational wave antenna. DECIGO is expected to provide us fruitful insights into the universe, in particular about dark energy, a formation mechanism of supermassive black holes, and the inflation of the universe. Since DECIGO will be an extremely large mission which will formed by three drag-free spacecraft with 1000m separation, it is significant to gain the technical feasibility of DECIGO before its planned launch in 2024. Thus, we are planning to launch two milestone missions: DPF and pre-DECIGO. The conceptual design and current status of the first milestone mission, DPF, are reviewed in this article

The status of DECIGO

DECIGO (DECi-hertz Interferometer Gravitational wave Observatory) is the planned Japanese space gravitational wave antenna, aiming to detect gravitational waves from astrophysically and cosmologically significant sources mainly between 0.1 Hz and 10 Hz and thus to open a new window for gravitational wave astronomy and for the universe. DECIGO will consists of three drag-free spacecraft arranged in an equilateral triangle with 1000 km arm lengths whose relative displacements are measured by a differential Fabry-Perot interferometer, and four units of triangular Fabry-Perot interferometers are arranged on heliocentric orbit around the sun. DECIGO is vary ambitious mission, we plan to launch DECIGO in era of 2030s after precursor satellite mission, B-DECIGO. B-DECIGO is essentially smaller version of DECIGO: B-DECIGO consists of three spacecraft arranged in an triangle with 100 km arm lengths orbiting 2000 km above the surface of the earth. It is hoped that the launch date will be late 2020s for the present

Producing animation: work, creativity, and aspirations in the Japanese animation industry

This thesis examines shifting relations of labour, creativity, and political economy in the context of commercial animation production in contemporary Tokyo. Based on 12 months of fieldwork in the Japanese animation industry (2009-2010), the ethnography of the thesis is centred on young animation makers whose lives are fraught with persistent job insecurity and socio-economic precariousness. Contrary to celebratory narratives of the global success of anime, found in both Japanese media discourses and the literature of Japanese studies, these professional young workers live on the socio-economic fringe of mainstream Japanese society. Despite such instability, labour discourses in the animation industry are notable for their highly aspirational quality, which appears to be based on global liberal discourses of self-realisation through the pursuit of dreams in the labour market. Commercial animation production in the Japanese industry entails a complex division of labour in which animation makers are, at the root, divided between managers and creators. This management-creative relation structures the primary context of commercial production. Thematically, the thesis engages mainly with three research literatures in anthropology: the anthropology of creativity, the anthropology of work, and Japanese ethnography. The analytical locus is built on the perspective of young entry-level managers, with whom I worked during fieldwork and who were on the lowest strata of the workplace hierarchy. Through the detailed ethnography of animation production – one of Japan’s premier creative industries – the thesis examines creative processes of animation making within the terms of work and labour. In so doing, it engages critically with the social and economic structures of commercial animation production, and explores the lived dimension of labour on the production floor. Methodologically, this means combining the perspectives of political economy and phenomenology by situating the micro-processes of animation making firmly in the industry’s social and economic relations of production. I pay particular attention to the ways in which shifting social and cultural discourses of labour in Japan intersect with global liberal ideologies, such as creativity and self-realisation, in the context of commercial animation production. The major focus of the thesis is therefore to explicate what it is that makes these young animation makers, despite adverse conditions of labour, retain their aspirations to pursue the profession of animation making

Producing animation: work, creativity, and aspirations in the Japanese animation industry

This thesis examines shifting relations of labour, creativity, and political economy in the context of commercial animation production in contemporary Tokyo. Based on 12 months of fieldwork in the Japanese animation industry (2009-2010), the ethnography of the thesis is centred on young animation makers whose lives are fraught with persistent job insecurity and socio-economic precariousness. Contrary to celebratory narratives of the global success of anime, found in both Japanese media discourses and the literature of Japanese studies, these professional young workers live on the socio-economic fringe of mainstream Japanese society. Despite such instability, labour discourses in the animation industry are notable for their highly aspirational quality, which appears to be based on global liberal discourses of self-realisation through the pursuit of dreams in the labour market. Commercial animation production in the Japanese industry entails a complex division of labour in which animation makers are, at the root, divided between managers and creators. This management-creative relation structures the primary context of commercial production. Thematically, the thesis engages mainly with three research literatures in anthropology: the anthropology of creativity, the anthropology of work, and Japanese ethnography. The analytical locus is built on the perspective of young entry-level managers, with whom I worked during fieldwork and who were on the lowest strata of the workplace hierarchy. Through the detailed ethnography of animation production â one of Japanâs premier creative industries â the thesis examines creative processes of animation making within the terms of work and labour. In so doing, it engages critically with the social and economic structures of commercial animation production, and explores the lived dimension of labour on the production floor. Methodologically, this means combining the perspectives of political economy and phenomenology by situating the micro-processes of animation making firmly in the industryâs social and economic relations of production. I pay particular attention to the ways in which shifting social and cultural discourses of labour in Japan intersect with global liberal ideologies, such as creativity and self-realisation, in the context of commercial animation production. The major focus of the thesis is therefore to explicate what it is that makes these young animation makers, despite adverse conditions of labour, retain their aspirations to pursue the profession of animation making.</p