18,938 research outputs found
Fourier-Mukai transforms for coherent systems on elliptic curves
We determine all the Fourier-Mukai transforms for coherent systems consisting
of a vector bundle over an elliptic curve and a subspace of its global
sections, showing that these transforms are indexed by the positive integers.
We prove that the natural stability condition for coherent systems, which
depends on a parameter, is preserved by these transforms for small and large
values of the parameter. By means of the Fourier-Mukai transforms we prove that
certain moduli spaces of coherent systems corresponding to small and large
values of the parameter are isomorphic. Using these results we draw some
conclusions about the possible birational type of the moduli spaces. We prove
that for a given degree of the vector bundle and a given dimension of the
subspace of its global sections there are at most different possible
birational types for the moduli spaces.Comment: LaTeX2e, 21 pages, some proofs simplified, typos corrected. Final
version to appear in Journal of the London Mathematical Societ
The Epistemic Control Loop
In the ICEA project we are concerned with the extraction of general designs from rat brains
Climate Change Impacts on Maize and Dry Bean Yields of smallholder farmers in Honduras
The rotation maize and dry bean provides the main food supply of smallholder farmers in Honduras. Crop model assessment of climate change impacts (2070?2099 compared to a 1961?1990 baseline) on a maize?dry bean rotation for several sites across a range of climatic zones and elevations in Honduras. Low productivity systems, together with an uncertain future climate, pose a high level of risk for food security. The cropping systems simulation dynamic model CropSyst was calibrated and validated upon field trail site at Zamorano, then run with baseline and future climate scenarios based upon general circulation models (GCM) and the ClimGen synthetic daily weather generator. Results indicate large uncertainty in crop production from various GCM simulations and future emissions scenarios, but generally reduced yields at low elevations by 0 % to 22 % in suitable areas for crop production and increased yield at the cooler, on the hillsides, where farming needs to reduce soil erosion with conservation techniques. Further studies are needed to investigate strategies to reduce impacts and to explore adaptation tactics
Strengthening financial innovations in energy supply projects for rural exploitations in developing countries
Sustainable energy supply models are needed to achieve the Millennium Development Goals established by the United Nations for 2015. On the other hand, sustainability of agricultural exploitations in rural areas is a pre-requisite to achieve the objective of halving the proportion of people that lives in poverty, and productivity of such exploitations is closely related to energy supply. This article analyses the results of a survey of experts, suggesting that there may be good chances to innovate in the financing of agricultural electrification projects in developing countries. The experts’ opinion suggests that new sources of financing could be mobilised and oriented towards the promotion of sustainable initiatives in developing countries. Financial mechanisms should be adapted to the characteristics of decentralised systems of energy production with renewable sources or with mixed technologies, in order to overcome the barriers derived from the high initial price of the applications, and to the specific conditions of the agricultural sector. The participation of funds from the beneficiaries and the incorporation of the beneficiaries in the initial phases of project organisation would allow for the development of productive solutions with a higher potential to generate resources and to articulate sustainable proposals. r 2007 Elsevier Ltd. All rights reserved
Intergenerational social mobility in Spain between 1956 and 2011: the role of educational expansion and economic modernisation in a late industrialised country
This article explores intergenerational class mobility patterns and the role played by education in Spain usingcounterfactuals. Both men and women born from 1926 to 1981 are analysed, meaning the study covers a periodof profound economic and educational advances in a late-industrialised country. The results suggest that, amongthe cohorts born in the 1970s, men have experienced a slight increase in socialfluidity, while women haveexperienced a substantial increase that seems partially driven by their massively increased access to routine non-manual positions independent of their social origins. Inequality of educational opportunities and class returns toeducation have declined, whereas the direct effect of social origins (DESO) has remained constant for men andhas decreased considerably for women. The counterfactual analysis shows that the slight increase in socialfluidity for men is mainly driven by educational expansion. For women, theDESOand educational expansionaccount for a great share of increasingfluidity. Therefore, certain assumptions made by theModernization TheoryandGoldthorpe’s Theory of Social Mobilitycan be put into questio
Methodological Flaws in Cognitive Animat Research
In the field of convergence between research in autonomous machine construction and biological systems understanding it is usually argued that building robots for research on auton- omy by replicating extant animals is a valuable strategy for engineering autonomous intelligent systems. In this paper we will address the very issue of animat construction, the ratio- nale behind this, their current implementations and the value they are producing. It will be shown that current activity, as it is done today, is deeply flawed and useless as research in the science and engineering of autonomy
Emotion and Metacontrol
In the ICEA Project we are concerned with the extraction of general designs from rat brains.
We are interested in designs that capture the core integrational aspects of emotion and cognition
Risk, Concentration and Market Power in the Banking Industry: Evidence from the Colombian System (1997-2006)
This paper examines the relationship between risk, concentration and the exercise of market power by banking institutions. We use monthly balance-sheet and interest rate data for the Colombian banking system from 1997 to 2006. The evidence shows that, in the face of high risk, banks transfer a larger share of risk to customers through higher intermediation margins. The result suggests that systemic risk acts as a collusion" device for banks: while high concentration is not enough to have collusion, the true effects of high market concentration on interest rates´ mark-ups emerge when the system is under stress."Banking, market power, risk, concentration, intermediation margins
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