Yukawa couplings and proton decay in SUSY models

We discuss proton decay induced by dimension--5 operators in supersymmetric models containing extra hypercharge-1/3 color-triplets. We derive a general formula relating dimension-5 operator to the color-triplet mass matrix. We show that certain zeros in the triplet mass-matrix together with some triplet coupling selection rules can lead to elimination of dimension-5 operators. We apply this mechanism to SU(5) and flipped SU(5) theories with extended Higgs sectors.Comment: 6 pages, uses JHEP.cls, talk given at the Trieste Meeting of the TMR Network on Physics Beyond the Standard Model, 24-27 February 1999, Trieste, Italy (to appear in the proceedings

On the classical limit of quantum mechanics, fundamental graininess and chaos: compatibility of chaos with the correspondence principle

The aim of this paper is to review the classical limit of Quantum Mechanics and to precise the well known threat of chaos (and fundamental graininess)to the correspondence principle. We will introduce a formalism for this classical limit that allows us to find the surfaces defined by the constants of the motion in phase space. Then in the integrable case we will find the classical trajectories, and in the non-integrable one the fact that regular initial cells become "amoeboid-like". This deformations and their consequences can be considered as a threat to the correspondence principle unless we take into account the characteristic timescales of quantum chaos. Essentially we present an analysis of the problem similar to the one of Omn\`{e}s [10,11], but with a simpler mathematical structure.Comment: 27 pages, 6 figure

The MODERE Model and The Economic Analysis of Farmers’ Decisions

The MODERE, the Ministry of the Environment Irrigation Decision Model, is a simulation tool which uses mathematical programming methods to reveal the implicit multiattribute objective function lying behind the observed cropping decision. The model takes different criteria such as profit maximization, risk aversion, avoidance of management complexities and so forth into account. In order to determine the feasible combination of attributes of this objective function the model considers the production possibility frontier explicitly as depending on market prices, policy incentives, availability of production factors, water irrigation facilities agronomic vocation and other constraints. Once calibrated the model becomes a powerful tool to assess the impact of different policy scenarios such as subsidies decoupling, water prices modifications, irrigation technique substitution and so on. The MODERE is a preference revelation model purposedly designed to be integrated in the Decision Support Platform which is used by the Spanish Ministry of the Environment to compare the policy scenarios which are relevant to assess the effectiveness and economic impact of the measures designed to reach the environmental objectives of the Water Framework Directive. The model is supported by a comprehensive data base built on purpose for its implementation covering almost all the Spanish Irrigation Districts with high spatial detail. This model is currently one of the important modules of the information and decision support systems developed by the Economic Analysis Unit of the Water Directorate at the Ministry of the Environment in Spain.Agricultural Economics, Water Economics, Simulated Models, Land Economics/Use, Political Economy, Research Methods/ Statistical Methods, Resource /Energy Economics and Policy,

Economic regional impacts of water transfers: the role of factor mobility in a case study of the agricultural sector in the Balearic Islands

Using a CGE model for the Balearic Islands, we simulate the effects of an agricultural water market in the farming sector facing reductions in the water endowment. The market lessens the negative effects on farming communities of short-term water restrictions associated with cyclical droughts. However, in scenarios of permanent reductions, such as those envisaged by global warming predictions or those that result from the implementation of the European Water Framework Directive, a water market may aggravate the negative effects of water shortage. Therefore, the paper shows that generalizations cannot be made about the effects of water markets on farming communities.Agricultural and Food Policy, Environmental Economics and Policy, D58, Q1, Q25, R13,

Enhancing Irrigation Efficiency but Increasing Water Use: The Jevons' Paradox

In this paper we analyze the conditions under which increasing technical efficiency of water use in the agricultural sector might not reduce water demand and pressures on water ecosystems. Departing from this basic problem we discuss how policy measures performed to enhance water productivity in the agriculture might be transformed into effective alternatives to improve the conservation of water resources and then guarantee the successful implementation of the Water Framework Directive. A preference revelation model is presented in the third section of the paper and one empirical application to an irrigation district in southern Spain is used in the fourth section to discuss the effectiveness of water savings measures.Water Framework Directive, Water Economics, Agricultural Economics, Simulation Models, Preference Revelation., Resource /Energy Economics and Policy,