7,627 research outputs found
Quantum anisotropic Heisenberg chains with superlattice structure: a DMRG study
Using the density matrix renormalization group technique, we study spin
superlattices composed of a repeated pattern of two spin-1/2 XXZ chains with
different anisotropy parameters. The magnetization curve can exhibit two
plateaus, a non trivial plateau with the magnetization value given by the
relative sizes of the sub-chains and another trivial plateau with zero
magnetization. We find good agreement of the value and the width of the
plateaus with the analytical results obtained previously. In the gapless
regions away from the plateaus, we compare the finite-size spin gap with the
predictions based on bosonization and find reasonable agreement. These results
confirm the validity of the Tomonaga-Luttinger liquid superlattice description
of these systems.Comment: 6 pages, 6 figure
Luttinger liquid superlattices: realization of gapless insulating phases
We investigate Luttinger Liquid superlattices, a periodic structure composed
of two kinds of one-dimensional systems of interacting electrons. We calculate
several properties of the low-energy sector: the effective charge and spin
velocities, the compressibility, various correlation functions, the Landauer
conductance and the Drude weight. The low-energy properties are subsumed into
effective parameters, much like homogeneous one-dimensional systems. A generic
result is the weighted average nature of these parameters, in proportion to the
spatial extent of the underlying subunits, pointing to the possibility of
``engineered'' structures. As a specific realization, we consider a
one-dimensional Hubbard superlattice, which consists of a periodic arrangement
of two long Hubbard chains with different coupling constants and different
hopping amplitudes. This system exhibits a rich phase diagram with several
phases, both metallic and insulating. We have found that gapless insulating
phases are present over a wide range of parameters.Comment: 16 pages, 15 figures, RevTeX
Un Análisis Lingüístico Comparativo del Sistema Fonológico del inglés y el español
This paper analyzes a few significant differences between Spanish and English in relation to phonological patterns. First, a short introduction is given about these two languages, and it is briefly explained in what linguistic aspects they are similar or different. Then, each of these linguistic features is analyzed in detail, clearly establishing the differences existing between Spanish and English. The specific phonological features that are addressed on this academic paper are vowel and consonant phonemes, diphthongs and triphthongs, as well as syllable and sentence stress. Furthermore, several pronunciation difficulties for Spanish speakers are discussed. Finally, some didactic implications are considered so that teachers can help their students of either language learn the second one considering important linguistic features.Este artículo analiza algunas diferencias significativas entre el español y el inglés en relación con los patrones fonológicos. En primer lugar, se hace una breve introducción sobre estos dos idiomas y se explica brevemente en qué aspectos lingüísticos son similares o diferentes. A continuación, se analiza en detalle cada uno de estos rasgos lingüísticos, estableciendo claramente las diferencias existentes entre el español y el inglés. Las características fonológicas específicas que se abordan en este artículo académico son los fonemas vocales y consonantes, diptongos y triptongos, así como el acento de sílabas y oraciones. Además, se discuten varias dificultades de pronunciación para hispanohablantes. Finalmente, se consideran algunas implicaciones didácticas para que los profesores puedan ayudar a sus alumnos de cualquiera de los dos idiomas a aprender el segundo considerando características lingüísticas importantes
A comparative Digital Soil Mapping (DSM) study using a non-supervised clustering analysis and an expert knowledge based model - A case study from Ahuachapán, El Salvador
DSM is the inference of spatial and temporal soil property variations using mathematical models based on quantitative relationships between environmental information and soil measurements. The quality of DSM information depends on the method and environmental covariates used for its estimations. We compared two DSM methods to predict soil properties such as Organic Matter “MO” (%), Sand (%), Clay (%), pH (H2O), Phosphorus (mg/kg), Effective Cationic Exchange Capacity “CICE” (cmol/L), Potassium (cmol/L) and Water Holding Capacity (mm/m) for the department of Ahuachapán in El Salvador to support the activities of the Agriculture Landscape Restoration Initiative (ALRI) in the countr
A comparative Digital Soil Mapping (DSM) study using a non-supervised clustering analysis and an expert knowledge based model - A case study from Ahuachapán, El Salvador
DSM is the inference of spatial and temporal soil property variations using mathematical models based on quantitative relationships between environmental information and soil measurements. The quality of DSM information depends on the method and environmental covariates used for its estimations. We compared two DSM methods to predict soil properties such as Organic Matter “MO” (%), Sand (%), Clay (%), pH (H2O), Phosphorus (mg/kg), Effective Cationic Exchange Capacity “CICE” (cmol/L), Potassium (cmol/L) and Water Holding Capacity (mm/m) for the department of Ahuachapán in El Salvador to support the activities of the Agriculture Landscape Restoration Initiative (ALRI) in the countr
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