Spin-boson coupling in continuous-time quantum Monte Carlo

A vector bosonic field coupled to the electronic spin is treated by means of the continuous-time quantum Monte Carlo method. In the Bose Kondo model with a sub-Ohmic density of states $\rho_{B}(\omega) \propto \omega^{s}$ with s=0.2, two contributions to the spin susceptibility, the Curie term T^{-1} and the term T^{-s} due to bosonic fluctuations, are observed separately. This result indicates the existence of a residual moment and a hidden critical behavior. By including hybridization with itinerant electrons, a quantum critical point is identified between this local-moment state and the Kondo singlet state. It is demonstrated that the energy scale of the bosonic fluctuations is not affected by the quantum phase transition.Comment: 8 pages, 7 figure

On the spaces with normal projective connexions and some imbedding problem of Riemannian spaces

In the present paper, we shall investigate the conditions under which a given Riemannian space Vn can be imbedded, as a hypersurface, into a Riemannian space Vn+1 which has the following properties I) and II). I) The group of holonomy of the space with a normal projective .connexion corresponding to Vn+1 fixes a hyperquadric and Vn is its image in Vn+1 , that is, the locus of points lying on the parallel displaced hyperquadrics, regarded as points in the tangent projective spaces. If Vn+1 has the property above, there exist a scalar y such that the hypersurface is given by the relation y -= 0. II) The orthogonal trajectories of the family of the hypersurfaces on which y is constant are geodesics in Vn+1. If the group of holonomy of the space with a normal projective eonnexion corresponding to a Vn+1 fixes a hyperquadric, it is projectively equivalent to an Einstein space2 ). In the previous paper, the author have studied the problem of the same kind as this under the conditions I) and II') Vn+1 is an Einstein space. The imbedding problem of Vn into Vn+1 under the only condition I) is very complicated in structure. The purpose of the present paper is also to search for the methods dealing with the problem, as the previous one. </p

Two-Particle Self-Consistent Approach to Anisotropic Superconductivity

A nonperturbative approach to anisotropic superconductivity is developed based on the idea of two-particle self-consistent (TPSC) theory by Vilk and Tremblay. A sum-rule which the momentum-dependent pairing susceptibility satisfies is derived. An effective pairing interaction between quasiparticles is determined so that the susceptibility should fulfill this exact sum-rule, in which fluctuations belonging to different symmetries couple at finite momentum. It is demonstrated that the mode coupling between d-wave and s-wave pairing fluctuations leads to suppression of the d-wave fluctuation near the Mott insulator.Comment: 7 pages, 5 figure

Estimating Agroforestry's Effect on Productivity in Kenya: An Application of a Treatment Effects Model

This study investigates the effects of adopting agroforestry and other soil conservation technologies (SCTs) on agricultural productivity in Kenya, using plot-level data on agricultural production. Using a treatment effects model, it is found that adopting agroforestry methods, as well as manure, chemical fertilizer, and terracing/trenching, increases total factor productivity (TFP) and land productivity. The TFP gain is estimated to be 40.7 percent from agroforestry. The average treatment effect for the adopters, however, turns slightly negative due to the negative self-selection effect, possibly because the agroforestry adopters tend to perceive adverse conditions on their land, which motivates them to adopt SCTs. In this sense, agroforestry and the other SCTs are preventive actions predominantly taken by farmers facing adverse conditions. The analysis demonstrates that both the simple mean comparison and the least squares estimation, due to their failure to reflect those complexities, could obscure the real benefits of SCTs.soil conservation technology; sustainability and agricultural productivity; self-selected participation; treatment effects model

Quantifying the Benefits of Trade Facilitation in ASEAN

This paper assesses the performance and progress of the ASEAN economies in trade facilitation, and the effect of improved trade facilitation on the regionfs manufacturing trade with a focus on port efficiency, customs environment, regulatory environment and service sector infrastructure. Under a scenario of raising the below-average countries halfway to the global average, ASEANfs trade is estimated to increase by $99 billion, three-quarters of which comes from the regionfs own improvements. Also, regulatory reforms, for example, enhancing transparency of trade-related regulations and ensuring law-abiding operations of the regulatory authorities, are found to be most effective.regional integration, trade facilitation, gravity model

Demand Response for Imported and Domestic Poultry Meat Products to Food Safety Regulations in Japan: An Application of the Almost Ideal Demand System Model

This study estimates the response of Japanese consumersf demand for poultry meat to the food safety regulations at the border using the almost ideal demand system (AIDS) with a particular focus on the maximum residue limits (MRL) on pesticides and veterinary drugs. The AIDS model allows for differing demand response to the food safety regulations across goods from different origins as consumers tend to rearrange their consumption within a product category. The results indicate the asymmetry of the demand response to a change in MRLs and avian-influenza bans. Tightening the MRLs reduces domestic demand for poultry meat as well as demand for imports from China and the US, and increases demand for imports from Brazil. Thus, the assessment of the impact of regulatory policies needs to take consumersf flexible rearrangement of bundles into account.Poultry meat trade, food safety regulations, the AIDS model

Systematized and Path-independent Measurement of Biased Technical Change

The sample-specificity and path-dependence of the data envelopment analysis (DEA) based technical change index as a component of Malmquist indexes prevent us from obtaining overall and systematic information on technical change. This paper develops a pathindependent method to estimate technical change using a systematized set of controlled input- output vectors and visualization of the DEA frontiers. The application to the panel datasets of agricultural production in the Brazil Amazon in 1975-1995 indicates non-Hicks-neutral technical change, with crossings of frontiers in both the 1975-1985 and the 1985-1995 periods. The alternative measure of overall technical change shows that moderate technological progress may have occurred on the whole in 1975-1995. The results also show heterogeneous trends across products. The mean of the sample-specific technical change scores are found to be quite different from the overall technical change measure.Data envelopment analysis, Path dependence, Agricultural intensification

Effect of International Standards Certification on Firm-Level Exports: An Application of the Control Function Approach

Growing number of firms in developing countries have earned certifications such as International Standards Organization (ISO) as it enhances reputation of their company or brand and attract buyers particularly in export market. This study evaluates the effect of international standards certification on firm's export performance in Europe and Central Asia by applying the control function approach with endogenous treatment effect to firm-level data. Certification is found to increase export share in firm's sales by 44.9% on average. The results suggest that ignoring the effect of self-selection of certification leads to a substantial bias in the estimated treatment effect.ontrol Function, international standards, international trade, self-selection

Memory effect on the formation of drying cracks

We propose a model for the formation of drying cracks in a viscoplastic material. In this model, we observe that when an external force is applied to a viscoplastic material before drying, the material memorizes the effect of the force as a plastic deformation. The formation of the drying cracks is influenced by this plastic deformation. This outcome clarifies the result of a recent experiments which demonstrated that a drying fracture pattern on a powder-water mixture depends on the manner in which an external force is applied before drying. We analytically express the position of the first crack as a function of the strength of an external force applied before drying. From the expression, we predict that there exists a threshold on the strength of the force. When the force applied is smaller than the threshold, the first crack is formed at the center of the mixture; however, when the force applied exceeds the threshold, the position of the first crack deviates from the center. The extent of the deviation increases as a linear function of the difference between the strength of the force and the threshold.Comment: 9 pages, 9 figure