A 2D integrable axion model and Target space duality

A review is given on the recently proposed two dimensional axion model (O(3) sigma-model with a dynamical Hopf-term) and the T-duality relating it to the SU(2)xU(1) symmetric anisotropic sigma-model. Strong evidence is presented for the correctness of the proposed S-matrix for both models comparing perturbative and Thermodynamical Bethe Ansatz calculations for different types of free energies. This also provides a very stringent test of the validity of T-duality transformation at the quantum level. The quantum non-integrability of the O(3) sigma-model with a non-dynamical Hopf-term, in contradistinction to the axion model, is illustrated by calculating the 2-->3 particle production amplitude to lowest order.Comment: LateX, 21 pages, 1 figure. Improved version of a talk delivered at the Johns Hopkins workshop `Non-perturbative QFT Methods and their Applications', Budapest, 200

An Exactly Soluble Model of Directed Polymers with Multiple Phase Transitions

Polymer chains with hard-core interaction on a two-dimensional lattice are modeled by directed random walks. Two models, one with intersecting walks (IW) and another with non-intersecting walks (NIW) are presented, solved and compared. The exact solution of the two models, based on a representation using Grassmann variables, leads, surprisingly, to the same analytic expression for the polymer density and identical phase diagrams. There are three different phases as a function of hopping probability and single site monomer occupancy, with a transition from the dense polymer system to a polymer liquid (A) and a transition from the liquid to an empty lattice (B). Within the liquid phase there exists a self-dual line with peculiar properties. The derivative of polymer density with respect to the single site monomer occupancy diverges at transitions A and B, but is smooth across and along the self-dual line. The density-density correlation function along the direction $x$, perpendicular to the axis of directedness has a power law decay 1/$x^2$ in the entire liquid phase, in both models. The difference between the two models shows up only in the behavior of the correlation function along the self-dual line: it decays exponentially in the IW model and as 1/$x^4$ in the NIW model.Comment: 8 pages, plain-TeX, figures available upon reques

SMALL FARMS IN CENTRAL AND EASTERN EUROPE: IS THERE A FUTURE FOR THEM?

Agribusiness, Agricultural and Food Policy, Consumer/Household Economics, Land Economics/Use,

THE CHOICE BETWEEN CONVENTIONAL AND ORGANIC FARMING – A HUNGARIAN EXAMPLE

The organic agriculture represents a promising alternative for the future of European agriculture. It is consistent with the notion of sustainable development set forth already in the 1992 CAP Reform. Despite of increasing importance of organic farming, the research on organic farming is still limited. This scarcity of the research is especially true for New Member States of the enlarged EU. This paper investigates the choice between conventional and organic production technologies for individual farmers in Hungarian agriculture. We apply a model that explicitly accounts for the effects of farm-specific variables like age and education on the expectations farmers have on the utility of both production technologies. In addition we take into account the perceptions of farmers about the organic farming. The model was estimated on a cross-section data set of Hungarian farmers for the period 2007 using a logit specification. It appears that education has a positive impact on the choice between conventional and organic farming, and, the size of the farm in hectares has a negative effect on this choice. Age and some general considerations on environmental friendly technologies do not have a significant effect on choice between conventional and organic farming.Innovation, Attitudes, Organic production, Diffusion, Agribusiness, Crop Production/Industries, Food Consumption/Nutrition/Food Safety,

WILLINGNESS OF FOOD INDUSTRY COMPANIES IN CO-FINANCING COLLECTIVE AGRICULTURAL MARKETING (CAM) ACTIONS

Marketing,

Classification of Static, Spherically Symmetric Solutions of the Einstein-Yang-Mills Theory with Positive Cosmological Constant

We give a complete classification of all static, spherically symmetric solutions of the SU(2) Einstein-Yang-Mills theory with a positive cosmological constant. Our classification proceeds in two steps. We first extend solutions of the radial field equations to their maximal interval of existence. In a second step we determine the Carter-Penrose diagrams of all 4-dimensional space-times constructible from such radial pieces. Based on numerical studies we sketch a complete phase space picture of all solutions with a regular origin.Comment: 49 pages, 19 figures, submitted to Commun. Math. Phy

Interface Unbinding in Structured Wedges

The unbinding properties of an interface near structured wedges are investigated by discrete models with short range interactions. The calculations demonstrate that interface unbinding take place in two stages: $i$) a continuous filling--like transition in the pure wedge--like parts of the structure; $ii$) a conclusive discontinuous unbinding. In 2$D$ an exact transfer matrix approach allows to extract the whole interface phase diagram and the precise mechanism at the basis of the phenomenon. The Metropolis Monte Carlo simulations performed in 3$D$ reveal an analogous behavior. The emerging scenario allows to shed new light onto the problem of wetting of geometrically rough walls.Comment: 5 pages, 5 figures, to appear in Phys. Rev.

Euclidean solutions of Yang-Mills-dilaton theory

Classical solutions of the Yang-Mills-dilaton theory in Euclidean space-time are investigated. Our analytical and numerical results imply existence of infinite number of branches of dyonic type solutions labelled by the number of nodes of gauge field amplitude $W$. We find that the branches of solutions exist in finite region of parameter space and discuss this issue in detail in different dilaton field normalization.Comment: 16 pages, 11 figures, references added, matches published vesio

Spatially Compact Solutions and Stabilization in Einstein-Yang-Mills-Higgs Theories

New solutions to the static, spherically symmetric Einstein-Yang-Mills-Higgs equations with the Higgs field in the triplet resp. doublet representation are presented. They form continuous families parametrized by $\alpha=M_W/M_Pl$ ($M_W$ resp. $M_Pl$ denoting the W-boson resp. the Planck mass). The corresponding spacetimes are regular and have spatially compact sections. A particularly interesting class with the Yang-Mills amplitude being nodeless is exhibited and is shown to be linearly stable with respect to spherically symmetric perturbations. For some solutions with nodes of the Yang-Mills amplitude a new stabilization phenomenon is found, according to which their unstable modes disappear as $\alpha$ increases (for the triplet) or decreases (for the doublet).Comment: 7 pages, 4 figure