Global Food Production under Alternative Scenarios

global food production, agriculture trade liberalisation, climate policy, EU agricultural subsidies, economic recession, Agribusiness, Q17, Q18, Q54,

Topological Sigma-model, Hamiltonian Dynamics and Loop Space Lefschetz Number

We use path integral methods and topological quantum field theory techniques to investigate a generic classical Hamiltonian system. In particular, we show that Floer's instanton equation is related to a functional Euler character in the quantum cohomology defined by the topological nonlinear $\sigma$--model. This relation is an infinite dimensional analog of the relation between Poincar\'e--Hopf and Gauss--Bonnet--Chern formul\ae$~$ in classical Morse theory, and can also be viewed as a loop space generalization of the Lefschetz fixed point theorem. By applying localization techniques to path integrals we then show that for a K\"ahler manifold our functional Euler character coincides with the Euler character determined by the finite dimensional de Rham cohomology of the phase space. Our results are consistent with the Arnold conjecture which estimates periodic solutions to classical Hamilton's equations in terms of de Rham cohomology of the phase space.Comment: 10 pages, LaTEX. New title and some modifications in the text. Version to appear in Phys. Lett.

Massively parallel approximate Gaussian process regression

We explore how the big-three computing paradigms -- symmetric multi-processor (SMC), graphical processing units (GPUs), and cluster computing -- can together be brought to bare on large-data Gaussian processes (GP) regression problems via a careful implementation of a newly developed local approximation scheme. Our methodological contribution focuses primarily on GPU computation, as this requires the most care and also provides the largest performance boost. However, in our empirical work we study the relative merits of all three paradigms to determine how best to combine them. The paper concludes with two case studies. One is a real data fluid-dynamics computer experiment which benefits from the local nature of our approximation; the second is a synthetic data example designed to find the largest design for which (accurate) GP emulation can performed on a commensurate predictive set under an hour.Comment: 24 pages, 6 figures, 1 tabl

The Next WTO Round on Agriculture and EU Enlargement: Pressures on the EU Dairy Sector

The EU dairy sector will be one of the most sensitive sectors to be affected by the outcome of the on-going negotiations for the new WTO round for agriculture. Nevertheless, if the Next WTO Round is going to be along the same lines as the Uruguay Round, the EU may be able to stay within the WTO commitments for export subsidy in the dairy sector without further reforms in the Common Agricultural Policy. Certainly, some minor reforms are needed to relieve the binding commitments for cheese and other milk products. The upcoming reform in the dairy sector under Agenda 2000 starting from year 2005 may help in reforming the dairy sector for the new round. In contrast, a steeper reduction in the export subsidy commitments compared to the Uruguay Round may cause problems for cheese and other milk products because the majority of exports in these products will have to be exported without any export subsidy. After enlargement, in particular with a steeper reduction formula, the EU may face troubles in the categories of butter, skim milk powder, cheese, and other milk products. The reforms under Agenda 2000 may not be sufficient because the difference between the EU internal market price and world market price is still too high for EU dairy products to allow unsubsidised exports to the world market. The EU internal market will have to absorb the dairy products intended for the export market. Consequently, the EU internal market for dairy products will be under pressure for further price reduction, and the EU world market share in dairy products will shrink.EU, WTO, enlargement, dairy sector, export subsidy, International Relations/Trade,

The Effects of China's Tariff Reductions on EU Agricultural Exports

China's accession to the WTO means significant increases in export opportunities for China's trading partners. This study attempts to identify and measure quantitatively the effects of changing economic environment and trade policies on China's agricultural imports from the European Union (EU). The approach is to estimate demand functions for China's agri-food imports from the EU using semi-annual data from 1980 to 2000. The demand functions are used to measure the impacts of relative-price and trade policy changes on EU agricultural exports to China. The results suggest that in China, there is a relatively strong demand response for agrifood imports to changes in income and prices. Furthermore, the results indicate that relative-price variations affect significantly the export market shares of the EU. Trade liberalisation in the form of tariff reductions is found to be relatively significant in changing the quantity of agri-food imports demand from China.China, WTO, agricultural trade, tariffs, demand functions, estimation, International Relations/Trade,

Antibrackets, Supersymmetric σ\sigma-Model and Localization

We consider supersymmetrization of Hamiltonian dynamics via antibrackets for systems whose Hamiltonian generates an isometry of the phase space. We find that the models are closely related to the supersymmetric non-linear $\sigma$-model. We interpret the corres\-ponding path integrals in terms of super loop space equivariant cohomology. It turns out that they can be evaluated exactly using localizations techniques.Comment: 9, pages, standard LaTe

Could Spin-Charge Separation be the Source of Confinement?

Yang-Mills gauge field with gauge group SU(2) decomposes into a single charge neutral complex vector, and two spinless charged scalar fields. At high energies these constituents are tightly confined into each other by a compact U(1) interaction, and the Yang-Mills Lagrangian describes the dynamics of asymptotically free massless gauge vectors. But in a low energy and finite density environment the interaction between the constituents can become weak, and a spin-charge separation may occur. We suggest that the separation between the spin and charge with the ensuing condensation of the charged scalars takes place when the Yang-Mills theory enters confinement. The confining phase becomes then surprisingly similar to the superconducting phase of a high-$T_c$ superconductor.Comment: Talk presented at QCD@Work 2005 (Conversano

Index Theorems and Loop Space Geometry

We investigate the evaluation of the Dirac index using symplectic geometry in the loop space of the corresponding supersymmetric quantum mechanical model. In particular, we find that if we impose a simple first class constraint, we can evaluate the Callias index of an odd dimensional Dirac operator directly from the quantum mechanical model which yields the Atiyah-Singer index of an even dimensional Dirac operator in one more dimension. The effective action obtained by BRST quantization of this constrained system can be interpreted in terms of loop space symplectic geometry, and the corresponding path integral for the index can be evaluated exactly using the recently developed localization techniques.Comment: 15 pages, report CERN-TH-6471 and HU-TFT-92-1