Landau-Ginzburg skeletons

We study the class of indecomposable two-dimensional Landau-Ginzburg theories with (2,2) supersymmetry and central charge c < 6 with the aim of classifying all such theories up to marginal deformations. Our results include cases overlooked in previous classifications. The results are rigorous for three or fewer fields and more generally are rigorous if we assume an extra bound. Numerics suggest that we have the complete set of indecomposable Landau-Ginzburg families with c<6. This set consists of 38 infinite families and a finite list of 418 sporadic cases. The basic tools are classic results of Kreuzer and Skarke on quasi-homogeneous isolated singularities and solutions to certain feasibility integer programming problems.Comment: 39 pages and tikz figures, three text files with LG charges included in submission; v2 fixes two sets of charge

Competition Policy Reform in Agriculture: A Comparison of the BRICs Countries

This paper forms part of a project titled ‘Facilitating Efficient Agricultural Markets in India: An Assessment of Competition and Regulatory Reform Requirements funded by the Australian Centre for International Agricultural Research (ACIAR). The project follows from previous research which found that India’s border reforms need to be complemented by ‘behind-the-border’ domestic reforms if government policy objectives of improved productivity, higher rural employment and incomes and enhanced food security are to be met. The project is being undertaken by Indian and Australian collaborators with expertise in agricultural policy development. Stage 1 of the project is designed to develop a common understanding among those collaborators of contemporary market based policy development principles and the extent to which they have been adopted in other developing countries. The BRICs economies of Brazil, Russia, India and China, as well as South Africa, were chosen for this purpose. A comparative overview of agricultural policy developments in these economies is underway drawing observations about policy reform impacts on agricultural production and the extent to which policy reforms have been consistent with competition policy and microeconomic reform principles applied in developed economies, such as Australia. The extent to which trade practices law has emerged in developing economies as an alternative to direct regulation is also considered. Preliminary findings are reported to facilitate broader discussion and encourage input from interested parties. Stage 2 of the project, commencing later in 2009, will involve the application of competition policy principles to the marketing regulations of a selection of agricultural industries in India. Consideration will be given to clarifying regulatory objectives, assessing their consistency with accepted forms of ‘market failure’ and assessing whether regulatory measures address those policy objectives in a manner least restrictive on competition. As well as facilitating efficient policy reform within India’s agricultural sector, the project aims to enhance the development of market based agricultural policy frameworks and the policy development skills of Indian and Australian policy makers.

Book reviews

Teaching/Communication/Extension/Profession,

The H=xp model revisited and the Riemann zeros

Berry and Keating conjectured that the classical Hamiltonian H = xp is related to the Riemann zeros. A regularization of this model yields semiclassical energies that behave, in average, as the non trivial zeros of the Riemann zeta function. However, the classical trajectories are not closed, rendering the model incomplete. In this paper, we show that the Hamiltonian H = x (p + l_p^2/p) contains closed periodic orbits, and that its spectrum coincides with the average Riemann zeros. This result is generalized to Dirichlet L-functions using different self-adjoint extensions of H. We discuss the relation of our work to Polya's fake zeta function and suggest an experimental realization in terms of the Landau model.Comment: 5 pages, 3 figure