Uniqueness and non-uniqueness of static vacuum black holes in higher dimensions

We prove the uniqueness theorem for asymptotically flat static vacuum black hole solutions in higher dimensional space-times. We also construct infinitely many non-asymptotically flat regular static black holes on the same spacetime manifold with the same spherical topology.Comment: to appear in Progress of Theoretical Physics Supplement No. 14

Uniqueness Theorem for Static Black Hole Solutions of sigma-models in Higher Dimensions

We prove the uniqueness theorem for self-gravitating non-linear sigma-models in higher dimensional spacetime. Applying the positive mass theorem we show that Schwarzschild-Tagherlini spacetime is the only maximally extended, static asymptotically flat solution with non-rotating regular event horizon with a constant mapping.Comment: 5 peges, Revtex, to be published in Class.Quantum Gra

Evaluating the potential of innovations across aquaculture product value chains for poverty alleviation in Bangladesh and India

Evidence is presented that innovation across aquaculture value chains can contribute to poverty reduction through income generation and increased consumption of nutritious aquatic foods. Innovation is defined and contextualized in relation to aquaculture development. Opportunities for aquaculture innovation across value chains for poverty reduction and sustainable production are described. Contemporary trends in aquaculture development in Bangladesh and India, with a focus on 2011-2020, are reviewed, as understanding transformative change to aquatic food systems during this period could benefit millions of poor and marginal consumers. Market-led commercial production, instigated by private sector entrepreneurs for domestic markets, has underpinned the surge in freshwater fish culture in key geographical locations. In contrast booms in shrimp production have been associated with export opportunities and related cycles of boom-and-bust have been described, with busts attributed to falling market prices and disease outbreaks. Innovation could safeguard supplies of affordable fish to poorer groups (especially young children and pregnant and breastfeeding women) and enable better health management of aquatic animals including coordination of surveillance and disease control measures. Innovation to effectively promote better management practices and integrated services provision to large numbers of small- and medium-scale producers could contribute to poverty reduction. Opportunities for future innovation to ensure that aquaculture development is sustainable are critically reviewed. Innovative strategies to add value to byproducts and utilize waste resources could avoid negative environmental impacts, recycle nutrients and create income generating opportunities. A new paradigm for development assistance that identifies and supports promising innovation trajectories across jurisdictions, product value chains, institutional regimes and food systems is needed. Government agencies must be responsive to the needs of businesses throughout aquatic food systems and devise policies and regulatory regimes that support transformative and sustained growth of the aquaculture sector. Investment in capacity-building, education, research and training and action to promote an enabling institutional environment must be regarded as essential elements to maximize and share equitably the benefits arising and avoid potential negative impacts of inappropriate innovations

THE UNIQUENESS THEOREM FOR ROTATING BLACK HOLE SOLUTIONS OF SELF-GRAVITATING HARMONIC MAPPINGS

We consider rotating black hole configurations of self-gravitating maps from spacetime into arbitrary Riemannian manifolds. We first establish the integrability conditions for the Killing fields generating the stationary and the axisymmetric isometry (circularity theorem). Restricting ourselves to mappings with harmonic action, we subsequently prove that the only stationary and axisymmetric, asymptotically flat black hole solution with regular event horizon is the Kerr metric. Together with the uniqueness result for non-rotating configurations and the strong rigidity theorem, this establishes the uniqueness of the Kerr family amongst all stationary black hole solutions of self-gravitating harmonic mappings.Comment: 18 pages, latex, no figure

Uniqueness Theorem of Static Degenerate and Non-degenerate Charged Black Holes in Higher Dimensions

We prove the uniqueness theorem for static higher dimensional charged black holes spacetime containing an asymptotically flat spacelike hypersurface with compact interior and with both degenerate and non-degenerate components of the event horizon.Comment: 9 pages, RevTex, to be published in Phys.Rev.D1

The classification of static vacuum space-times containing an asymptotically flat spacelike hypersurface with compact interior

We prove non-existence of static, vacuum, appropriately regular, asymptotically flat black hole space-times with degenerate (not necessarily connected) components of the event horizon. This finishes the classification of static, vacuum, asymptotically flat domains of outer communication in an appropriate class of space-times, showing that the domains of outer communication of the Schwarzschild black holes exhaust the space of appropriately regular black hole exteriors.Comment: This version includes an addendum with a corrected proof of non-existence of zeros of the Killing vector at degenerate horizons. A problem with yet another Lemma is pointed out; this problem does not arise if one assumes analyticity of the metric. An alternative solution, that does not require analyticity, has been given in arXiv:1004.0513 [gr-qc] under appropriate global condition

Extrema of Mass, First Law of Black Hole Mechanics and Staticity Theorem in Einstein-Maxwell-axion-dilaton Gravity

Using the ADM formulation of the Einstein-Maxwell axion-dilaton gravity we derived the formulas for the variation of mass and other asymptotic conserved quantities in the theory under consideration. Generalizing this kind of reasoning to the initial dota for the manifold with an interior boundary we got the generalized first law of black hole mechanics. We consider an asymptotically flat solution to the Einstein-Maxwell axion-dilaton gravity describing a black hole with a Killing vector field timelike at infinity, the horizon of which comprises a bifurcate Killing horizon with a bifurcate surface. Supposing that the Killing vector field is asymptotically orthogonal to the static hypersurface with boundary S and compact interior, we find that the solution is static in the exterior world, when the timelike vector field is normal to the horizon and has vanishing electric and axion- electric fields on static slices.Comment: 17 pages, Revtex, a few comments (introduction) and references adde