23,828 research outputs found
Matrix models without scaling limit
In the context of hermitean one--matrix models we show that the emergence of
the NLS hierarchy and of its reduction, the KdV hierarchy, is an exact result
of the lattice characterizing the matrix model. Said otherwise, we are not
obliged to take a continuum limit to find these hierarchies. We interpret this
result as an indication of the topological nature of them. We discuss the
topological field theories associated with both and discuss the connection with
topological field theories coupled to topological gravity already studied in
the literature.Comment: Latex, SISSA-ISAS 161/92/E
The (N,M)-th KdV hierarchy and the associated W algebra
We discuss a differential integrable hierarchy, which we call the (N, M)MW_N$ algebra. We show
that there exist M distinct reductions of the (N, M)--th KdV hierarchy, which
are obtained by imposing suitable second class constraints. The most drastic
reduction corresponds to the (N+M)--th KdV hierarchy. Correspondingly the W(N,
M) algebra is reduced to the W_{N+M} algebra. We study in detail the
dispersionless limit of this hierarchy and the relevant reductions.Comment: 40 pages, LaTeX, SISSA-171/93/EP, BONN-HE-46/93, AS-IPT-49/9
Disentangling the Demand-enhancing Effect and Trade-cost Effect of Technical Measures in Agricultural Trade among OECD countries
Domestic technical measures such as SPS and TBTs can enhance import demand via information disclosure and quality improvement, or hamper foreign export supply via imposing sizeable compliance costs, or both. The traditional gravity equation model estimates the net effect of these measures on international trade with a loss of useful inference on separate effects. We stipulate a generalized gravity equation model to disentangle the two effects. We apply the augmented approach to agricultural trade among OECD countries in 2004. We find that technical measures in agriculture often jointly enhance import demand and hinder export supply with the net effect of promoting the propensity to trade. Further disaggregated data analysis reveals heterogeneity across sectors in terms of net effects of technical measures, despite common demand-enhancing and supply-hindering effects. These measures in the net decrease the probability of intra-OECD trade in dairy products, whereas they increase that of intra-OECD trade in cereal preparations.sanitary and phytosanitary, SPS, technical measures, NTM, TBT, standards, gravity equation, protectionism, OECD, International Relations/Trade,
Does European Aflatoxin Regulation Hurt Groundnut Exporters from Africa?
We provide an ex-post econometric examination of the harmonization and tightening of the EU Maximum Residues Limit (MRL) on aflatoxins in 2002, and its impact on African exports of groundnut products. We show that the MRL set by the EU has no significant trade impact on groundnut exports from Africa across various methods of estimation. African domestic supply plays an important role in the determination of the volumes of trade and the propensity to trade. Our findings suggest that the trade potential of African groundnut exporters is more constrained by domestic supply issues rather than by limited market access.food safety; standards; aflatoxin; MRL; groundnut; Africa; EU; market access
Aflatoxin Redux: Does European Aflatoxin Regulation Hurt Groundnut Exporters from Africa?
Replaced with revised version of paper 07/02/10.food safety, standards, aflatoxin, Maximum Residues Limit, groundnut, gravity equation, Africa, market access, EU, Agricultural and Food Policy, Community/Rural/Urban Development, Crop Production/Industries, Food Consumption/Nutrition/Food Safety, Food Security and Poverty, International Development, International Relations/Trade, Q17, F13,
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