On the Topology of the Inflaton Field in Minimal Supergravity Models

We consider global issues in minimal supergravity models where a single field inflaton potential emerges. In a particular case we reproduce the Starobinsky model and its description dual to a certain formulation of R+R^2 supergravity. For definiteness we confine our analysis to spaces at constant curvature, either vanishing or negative. Five distinct models arise, two flat models with respectively a quadratic and a quartic potential and three based on the SU(1,1)/U(1) space where its distinct isometries, elliptic, hyperbolic and parabolic are gauged. Fayet-Iliopoulos terms are introduced in a geometric way and they turn out to be a crucial ingredient in order to describe the de Sitter inflationary phase of the Starobinsky model.Comment: 31 pages, LaTex, 7 eps figures, 2 table

R-Symmetry and the Topological Twist of N=2 Effective Supergravities of Heterotic Strings

We discuss R-symmetries in locally supersymmetric N=2 gauge theories coupled to hypermultiplets which can be thought of as effective theories of heterotic superstring models. In this type of supergravities a suitable R-symmetry exists and can be used to topologically twist the theory: the vector multiplet containing the dilaton-axion field has different R-charge assignments with respect to the other vector multiplets. Correspondingly a system of coupled instanton equations emerges, mixing gravitational and Yang--Mills instantons with triholomorphic hyperinstantons and axion-instantons. For the tree-level classical special manifolds $ST(n)=SU(1,1)/U(1)\times SO(2,n)/(SO(2)$ $\times SO(n))$ R-symmetry with the specified properties is a continuous symmetry, but for the quantum corrected manifolds ${\hat {ST}}(n)$ a discrete R--group of electric--magnetic duality rotations is sufficient and we argue that it exists.Comment: 40 pages, plain LaTeX. Final version to appear on IJMP

The Great Green Forest is here and expanding all on its own: A call for action

Prosopis juliflora is recognized as one of the most invasive tree species worldwide. Following widespread introductions throughout arid and semi-arid regions of Africa and throughout the world, it has spread rapidly, threatening natural ecosystems and livelihoods. Control through utilization as a resource is now accepted as the way forward in developing countries, but efforts have so far been uncoordinated, with only isolated impacts. This paper reports on the global state of knowledge and recent advances, but focuses on prosopis-related research and innovations from IGAD member countries; the successes, failures, challenges and opportunities. It underlines the need to build and apply scientific knowledge to scale up new, resilient, drought-proof livelihood options in the Greater Horn of Africa and elsewhere where introduced, from value-added prosopis wood and non wood products. The authors estimate that there are at least five million hectares of prosopis forest across the region of the perhaps ten million throughout Africa, and growing significantly in extent every year. Experiences from the native range such as in Peru are well documented, where community associations sustainably manage and make a living from fuel, fodder, food, honey and timber from their prosopis forests. Efforts in Ethiopia, Djibouti and Kenya have had mixed results, but milling the sweet protein-rich pods into animal feed is becoming increasingly popular with the introduction of appropriate small scale technologies. Its use as a human food ingredient has also been promoted, though with little uptake, but there is sharp rise in the use of prosopis charcoal in the region, and the possibility of electricity generation using wood chips (bioenergy), with the transfer of experiences from India where there are at least 15 power stations fueled entirely by prosopis. But much more can be done by applying scientific knowledge and innovation to enhance the role of prosopis in improving food security, climate change mitigation and adaptation, and building resilience for millions of the poorest rural and urban people in the Greater Horn of Africa, with great potential for exchange and scaling up in other arid areas in Africa, Asia and the Americas. This paper is a call to the African Union, national governments, IGAD, IFAD, FAO, the Arab League and other international, regional and bilateral donors, to come together and support a regional research and development programme to push the frontiers on prosopis management and utilization and develop a transnational strategy, as the impacts are potentially enormous and immediate. The initial objectives are to take stock of existing knowledge and practices, assess prosopis forest areas throughout the region, estimate wood and pod volumes and production rates, document prosopis management and utilization experiences, enhance South-South knowledge sharing, and rapidly and effectively scale up the successes