4,528 research outputs found
Duality symmetry in four-dimensional string actions
We reduce the dual version of , supergravity coupled to
vector fields to four dimensions, and derive the
transformations which leave the equations of motion invariant. For
is also a symmetry of the action, but for only those
transformations which act linearly on all fields leave the action invariant.
The resulting four-dimensional theory is related to the bosonic part of the
usual formulation of supergravity coupled to matter by a duality
transformation.Comment: 9 pages, Latex fil
De Sitter in Extended Supergravity
We show that known de Sitter solutions in extended gauged supergravity
theories are interrelated via a web of supersymmetry-breaking truncations. In
particular, all N=8 models reduce to a subset of the N=4 possibilities.
Furthermore, a different subset of the N=4 models can be truncated to stable de
Sitter vacua in N=2 theories. In addition to relations between the known cases,
we also find new (un)stable models.Comment: 16 page
Dual versions of extended supergravities
Recently, using the model of N=2 supergravity -- vector multiplets
interaction with the scalar field geometry as an
example, we have shown that even when the scalar field geometry is fixed, one
can have a whole family of the Lagrangians, which differ by vector field
duality transformation. In this paper we carry out the construction of such
families for the case of N=3 and N=4 supergravities, the scalar field geometry
being and , correspondingly. Moreover, it turns out that these
families contain, as a partial case, the models describing the interaction of
arbitrary number of vector multiplets with our hidden sectors, admitting
spontaneous supersymmetry breaking without a cosmological term.Comment: 9 pages, plain LaTeX, no figure
The role, opportunities and challenges of 3D and geo-ICT in archaeology
Archaeology joins in the trend of three-dimensional (3D) data and geospatial information technology (geo-ICT). Currently, the spatial archaeological data acquired is 3D and mostly used to create realistic visualizations. Geographical information systems (GIS) are used for decades in archaeology. However, the integration of geo-ICT with 3D data still poses some problems. Therefore, this paper clarifies the current role of 3D, and the opportunities and challenges for 3D and geo-ICT in the domain of archaeology. The paper is concluded with a proposal to integrate both trends and tackle the outlined challenges. To provide a clear illustration of the current practices and the advantages and difficulties of 3D and geo-ICT in the specific case of archaeology, a limited case study is presented of two structures in the Altay Mountains
Good Governance of land and natural resources : Balancing local and global interests
This report presents the results of a seminar on âgood governance of land and natural resources; balancing local and global interestsâ. Three case studies were presented on large-scale land acquisitions, biofuels â fuelling development in Brazil and governance of the mineral sector in Eastern DRC. Participants identified 6 important challenges for improving land and natural resource governance and concluded that: more research and information sharing is needed; collaborative voluntary and legally binding initiatives are needed at international level to balance local and global interests; accountability arrangements need to be set up that enable stakeholders to hold each other accountable; capacity building of all actors is needed and that each actor has its own contributions to make to good governance
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