We present a second order sharp interface finite volume method for the solution of the three-dimensional elliptic equation ∇ pβp~xq∇up~xqq fp~xq with variable coefficients on Cartesian grids. In particular, we focus on interface problems with discontinuities in the coefficient, the source term, the solution, and the fluxes across the interface. The method uses standard piecewiese trilinear fini...

Currently, within business, intangible assets are growing in significance in relation to traditional tangible assets. There is a need of alternative approaches in order to measure the value of knowledge. This paper looks at the problem of knowledge measurement and argues for the importance of metrics to the overall process of knowledge management. The concept of Balanced Scorecard is critically...

Low-dimensional quantum magnets promote strong correlations between magnetic moments that lead to fascinating quantum phenomena. A particularly interesting system is the antiferromagnetic spin-1/2 Heisenberg chain because it is exactly solvable by the Bethe-Ansatz method. It is approximately realized in the magnetic insulator copper pyrazine dinitrate, providing a unique opportunity for a quant...

Integrable open-boundary conditions for the supersymmetric t-J model. The quantum group invariant case. Abstract We consider integrable open–boundary conditions for the supersymmetric t–J model commuting with the number operator n and S z. Four families, each one depending on two arbitrary parameters, are found. We find the relation between Sklyanin's method of constructing open boundary condit...

The paper is a review of recent works devoted to analysis of classical integrable structures in quantum integrable models solved by one or another version of the Bethe ansatz. Similarities between elements of the quantum and classical theories of integrable systems are discussed. Some key notions of the quantum theory, now standard in the quantum inverse scattering method, are identiied with ty...

We study integrable vertex models and quantum spin chains with toroidal boundary conditions. An interesting class of such boundaries is associated with non-diagonal twist matrices. For such models there are no trivial reference states upon which a Bethe ansatz calculation can be constructed, in contrast to the well-known case of periodic boundary conditions. In this paper we show how the transf...