Commutation Relations for Unitary Operators

Let $U$ be a unitary operator defined on some infinite-dimensional complex Hilbert space ${\cal H}$. Under some suitable regularity assumptions, it is known that a local positive commutation relation between $U$ and an auxiliary self-adjoint operator $A$ defined on ${\cal H}$ allows to prove that the spectrum of $U$ has no singular continuous spectrum and a finite point spectrum, at least locally. We show that these conclusions still hold under weak regularity hypotheses and without any gap condition. As an application, we study the spectral properties of the Floquet operator associated to some perturbations of the quantum harmonic oscillator under resonant AC-Stark potential

Commutation Relations for Unitary Operators III

Let $U$ be a unitary operator defined on some infinite-dimensional complex Hilbert space ${\cal H}$. Under some suitable regularity assumptions, it is known that a local positive commutation relation between $U$ and an auxiliary self-adjoint operator $A$ defined on ${\cal H}$ allows to prove that the spectrum of $U$ has no singular continuous spectrum and a finite point spectrum, at least locally. We prove that under stronger regularity hypotheses, the local regularity properties of the spectral measure of $U$ are improved, leading to a better control of the decay of the correlation functions. As shown in the applications, these results may be applied to the study of periodic time-dependent quantum systems, classical dynamical systems and spectral problems related to the theory of orthogonal polynomials on the unit circle

Zonificación del potencial energético de la biomasa residual forestal en la cuenca del lago Ranco, Chile. Antecedentes para la planificación energética regional

Land planning comprises a stage of land management whose aim is to generate proposals from analyzing the information of the territory, which represents multiple variables of the geographic space. Some of the most recent lines of planning are renewable energies and particularly residual forest biomass since this is a non used environmental element but with a high growth potential. For this task, using technological tools like geographic information systems or remote sensing permits to handle these topics and express them in a spatial zoning for decision making. According to this, a prospective work was made in the watershed of Ranco Lake, where optimum spaces were defined to obtain residual forest biomass in four vegetational units (coigüe-raulí-tepa, roble-raulí-coigüe, evergreen and forest plantations). The results showed that there exists an overall potential surface to handle of 45,555 hectares, from which the forest type coigüe-raulí-tepa highlights with a 62.4 % of the surface. Under the assumption of availability of residual forest biomass in the watershed and a scene of energetic crisis, the importance of prioritizing regional policies and research concerning the development of non conventional renewable energies is recognized

Evaluation of Corrosion Caused by Biogenic Sulfuric Acid (BSA) on the Concrete Structures of Sewerage Systems: Chemical Tests

The research studies of the kinetics of the corrosion process that attacks concrete and occurs within sewerage systems agree on the amount of variables that interfere in the process. This study aims to check the impact of the pH levels of the corrosive environment and the concrete surface, the concentrations of chemical sulfuric acid, and in turn, measure the resistance of concrete to this attack under controlled laboratory conditions; it also aims to contribute to the development of further research related to the topic, in order to compare the impact of biogenic sulfuric acid and chemical sulfuric acid involvement on concrete structures, especially in scenarios such as sewerage systems

Evaluation of Corrosion Caused by Biogenic Sulfuric Acid (BSA) on the Concrete Structures of Sewerage Systems: Chemical Tests

The research studies of the kinetics of the corrosion process that attacks concrete and occurs within sewerage systems agree on the amount of variables that interfere in the process. This study aims to check the impact of the pH levels of the corrosive environment and the concrete surface, the concentrations of chemical sulfuric acid, and in turn, measure the resistance of concrete to this attack under controlled laboratory conditions; it also aims to contribute to the development of further research related to the topic, in order to compare the impact of biogenic sulfuric acid and chemical sulfuric acid involvement on concrete structures, especially in scenarios such as sewerage systems

Tendencias y problemas actuales relacionados con a actividad turística

El texto que se ofrece es una construcción prospectiva sobre el comportamiento turístico en el contexto de las megatendencias de la economía global, la política, la sustentabilidad, la dinámica social y el desarrollo tecnológico. El análisis consisten en delinear elementos significativos del comportamiento turístico en el entorno de los aspectos mencionados