High-Field Low-Frequency Spin Dynamics

The theory of exchange symmetry of spin ordered states is extended to the case of high magnetic field. Low frequency spin dynamics equation for quasi-goldstone mode is derived for two cases of collinear and noncollinear antiferromagnets.Comment: 2 page

Structural compliance, misfit strain and stripe nanostructures in cuprate superconductors

Structural compliance is the ability of a crystal structure to accommodate variations in local atomic bond-lengths without incurring large strain energies. We show that the structural compliance of cuprates is relatively small, so that short, highly doped, Cu-O-Cu bonds in stripes are subject to a tensile misfit strain. We develop a model to describe the effect of misfit strain on charge ordering in the copper oxygen planes of oxide materials and illustrate some of the low energy stripe nanostructures that can result.Comment: 4 pages 5 figure

Magnetic double refraction in piezoelectrics

A new type of magneto-optical effect in piezoelectrics is predicted. A low frequency behavior of Faraday effect is found.Comment: 2 pages, to be published in Europhys. Lett

Inverse spectral problems for Sturm--Liouville operators with matrix-valued potentials

We give a complete description of the set of spectral data (eigenvalues and specially introduced norming constants) for Sturm--Liouville operators on the interval $[0,1]$ with matrix-valued potentials in the Sobolev space $W_2^{-1}$ and suggest an algorithm reconstructing the potential from the spectral data that is based on Krein's accelerant method.Comment: 39 pages, uses iopart.cls, iopams.sty and setstack.sty by IO

Elastic domains in antiferromagnets

We consider periodic domain structures which appear due to the magnetoelastic interaction if the antiferromagnetic crystal is attached to an elastic substrate. The peculiar behavior of such structures in an external magnetic field is discussed. In particular, we find the magnetic field dependence of the equilibrium period and the concentrations of different domains

Bunching Transitions on Vicinal Surfaces and Quantum N-mers

We study vicinal crystal surfaces with the terrace-step-kink model on a discrete lattice. Including both a short-ranged attractive interaction and a long-ranged repulsive interaction arising from elastic forces, we discover a series of phases in which steps coalesce into bunches of n steps each. The value of n varies with temperature and the ratio of short to long range interaction strengths. We propose that the bunch phases have been observed in very recent experiments on Si surfaces. Within the context of a mapping of the model to a system of bosons on a 1D lattice, the bunch phases appear as quantum n-mers.Comment: 5 pages, RevTex; to appear in Phys. Rev. Let

Electric-field induced capillary interaction of charged particles at a polar interface

We study the electric-field induced capillary interaction of charged particles at a polar interface. The algebraic tails of the electrostatic pressure of each charge results in a deformation of the interface $u\sim \rho ^{-4}$. The resulting capillary interaction is repulsive and varies as $\rho ^{-6}$ with the particle distance. As a consequence, electric-field induced capillary forces cannot be at the origin of the secondary minimum observed recently for charged PMMA particles at on oil-water interface.Comment: June 200

Simulación y control predictivo del sistema de transporte de gas en una gran zona industrial

El artículo describe un enfoque para el control operativo y de supervisión de un sistema de transmisión de gas para grandes zonas industriales utilizando un modelo de control predictivo, así como métodos analíticos y de simulación. El control operativo y de supervisión del sistema de transporte de gas cubre el horizonte temporal de varias horas a varios días e implica la realización de varias acciones cíclicamente repetidas. Los autores proponen un modelo predictivo de series de tiempo del parámetro de consumo de gas considerando las condiciones climáticas de temperatura, que se amplía con base en la contabilidad de las relaciones de correlación entre los volúmenes de consumo de cada consumidor. Los métodos de control utilizados en la actualidad, reaccionando a las desviaciones actuales del régimen planificado, a priori no permiten lograr los mejores resultados. Se puede lograr un aumento significativo en la estabilidad del control y una reducción en el costo del combustible y los recursos energéticos utilizando el método de control basado en modelos predictivos. En este caso, el modelo de objeto de control se utiliza para predecir su comportamiento dentro del horizonte de tiempo seleccionado, y las acciones de control óptimas se seleccionan sobre esta base. El proceso de predecir y seleccionar acciones de control se repite periódicamente, cambiando constantemente los límites del horizonte temporal. El método descrito para cambiar el diagrama de flujo consiste en cambiar todos los flujos al mismo tiempo o en una transición preventiva y suave basada en la introducción de un diagrama de flujo ponderado para varios modos estacionarios, siempre que su desajuste se minimice en intervalos de tiempo vecinos. correspondiente a los intervalos de constancia de las solicitudes de consumo

On a systematic approach to defects in classical integrable field theories

We present an inverse scattering approach to defects in classical integrable field theories. Integrability is proved systematically by constructing the generating function of the infinite set of modified integrals of motion. The contribution of the defect to all orders is explicitely identified in terms of a defect matrix. The underlying geometric picture is that those defects correspond to Backlund transformations localized at a given point. A classification of defect matrices as well as the corresponding defect conditions is performed. The method is applied to a collection of well-known integrable models and previous results are recovered (and extended) directly as special cases. Finally, a brief discussion of the classical $r$-matrix approach in this context shows the relation to inhomogeneous lattice models and the need to resort to lattice regularizations of integrable field theories with defects.Comment: 27 pages, no figures. Final version accepted for publication. References added and section 5 amende

Influence of Strain on the Kinetics of Phase Transitions in Solids

We consider a sharp interface kinetic model of phase transitions accompanied by elastic strain, together with its phase-field realization. Quantitative results for the steady-state growth of a new phase in a strip geometry are obtained and different pattern formation processes in this system are investigated