3,520 research outputs found
Is Sustainable Development of Deserts Feasible?
Hot deserts that presently cover about one-fifth of the land area of our planet are rapidly devouring more and more arable lands mostly due to anthropogenic causes. We propose an interdisciplinary approach to revitalizing and commercializing hot deserts, which is based on systems thinking and Russian and NASA space technology experience in designing life-support systems for long-duration flights. We formulate ten principles for the design of sustainable life support systems in deserts, which can make the development of the deserts feasible. It is discussed how the principles can be employed to design and operate desert’s eco-industrial parks with greenhouses in which the transpired and evaporated moisture is collected and condensed. The potential benefits of setting up the eco-industrial parks in deserts include the slowdown and eventual reversal of the desertification trend, the migration of many industrial production facilities from mild-climate regions to deserts, the increased availability of potable water and food in deserts, the development of poor African countries, and the emergence of new investment markets
Dispersive evaluation of the D-term form factor in deeply virtual Compton scattering
We present a dispersive representation of the D-term form factor for hard
exclusive reactions, using unsubtracted -channel dispersion relations. The
-channel unitarity relation is saturated with the contribution of two-pion
intermediate states, using the two-pion distributions amplitude for the
subprocess and reconstructing the
subprocess from available information on
pion-nucleon partial-wave helicity amplitudes. Results for the D-term form
factor as function of as well as at are discussed in comparison with
available model predictions and phenomenological parametrizations.Comment: 8 pages, 3 figures; improved presentation of the results; version to
appear in Phys. Lett.
Flavor asymmetry of polarized antiquark distributions and semi-inclusive DIS
The -expansion of QCD suggests large flavor asymmetries of the
polarized antiquark distributions in the nucleon. This is confirmed by model
calculations in the large- limit (chiral quark-soliton model), which give
sizable results for and . We compute the contributions of
these flavor asymmetries to the spin asymmetries in hadron production in
semi-inclusive deep-inelastic scattering. We show that the large flavor
asymmetries predicted by the chiral quark-soliton model are consistent with the
recent HERMES data for spin asymmetries in charged hadron production.Comment: 21 pages, LaTeX2e, 9 eps figures include
AdS/CFT correspondence via R-current correlation functions revisited
Motivated by realizing open/closed string duality in the work by Gopakumar
[Phys. Rev. D70:025009,2004], we study two and three-point correlation
functions of R-current vector fields in N=4 super Yang-Mills theory. These
correlation functions in free field limit can be derived from the worldline
formalism and written as heat kernel integrals in the position space. We show
that reparametrizing these integrals converts them to the expected AdS
supergravity results which are known in terms of bulk to boundary propagator.
We expect that this reparametrization corresponds to transforming open string
moduli parameterization to the closed string ones.Comment: 23 pages, v2: calculations clarified, references added, v3: sections
re-arranged with more explanations, 4 figures and an appendix adde
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