A quantum information approach to statistical mechanics

We review some connections between quantum information and statistical mechanics. We focus on three sets of results for classical spin models. First, we show that the partition function of all classical spin models (including models in different dimensions, different types of many-body interactions, different symmetries, etc) can be mapped to the partition function of a single model. Second, we give efficient quantum algorithms to estimate the partition function of various classical spin models, such as the Ising or the Potts model. The proofs of these two results are based on a mapping from partition functions to quantum states and to quantum circuits, respectively. Finally, we show how classical spin models can be used to describe certain fluctuating lattices appearing in models of discrete quantum gravity.Comment: 9 pages, 9 figure

Simple universal models capture all classical spin physics

Spin models are used in many studies of complex systems---be it condensed matter physics, neural networks, or economics---as they exhibit rich macroscopic behaviour despite their microscopic simplicity. Here we prove that all the physics of every classical spin model is reproduced in the low-energy sector of certain `universal models'. This means that (i) the low energy spectrum of the universal model reproduces the entire spectrum of the original model to any desired precision, (ii) the corresponding spin configurations of the original model are also reproduced in the universal model, (iii) the partition function is approximated to any desired precision, and (iv) the overhead in terms of number of spins and interactions is at most polynomial. This holds for classical models with discrete or continuous degrees of freedom. We prove necessary and sufficient conditions for a spin model to be universal, and show that one of the simplest and most widely studied spin models, the 2D Ising model with fields, is universal.Comment: v1: 4 pages with 2 figures (main text) + 4 pages with 3 figures (supplementary info). v2: 12 pages with 3 figures (main text) + 35 pages with 6 figures (supplementary info) (all single column). v2 contains new results and major revisions (results for spin models with continuous degrees of freedom, explicit constructions, examples...). Close to published version. v3: minor typo correcte

Predictive validity of the Sidorkiewicz instrument in Spanish: Assessing individual drug adherence in psychiatric patients

Background/Objective: Concomitant prescription of two or more psychiatric med-ications has become the rule and patients could adhere differently to their variousdrugs prescribed. Sidorkiewicz et al. published a questionnaire for assessing adherenceto each specific drug. Method: This study explored the predictive validity of the Span-ish version of the Sidorkiewicz questionnaire in a sample of 470 consecutive psychiatricoutpatients using 897 psychiatric drugs. Results: The questionnaire showed adequate pre-dictive validity in both univariate and multivariate analyses (logistic regression and CHAIDsegmentation) since they demonstrated a significant association with the 10-item DrugAttitude Inventory and with the Necessity and Concern Scales of the Beliefs aboutMedications Questionnaire. Some demographic and clinical variables were significant inthe univariate analyses but lost significance in the multivariate analyses. Conclusions:The adherence of the psychiatric patient to his/her prescribed treatment may not besignificantly influenced by socio-demographic or clinical characteristics, but rather by atti-tudes toward medication, perceptions of personal necessity for medication, and concerns∗Antecedentes/Objetivo: La prescripción concomitante más de un psicofármaco enun mismo paciente se ha convertido en la regla de la práctica clínica psiquiátrica actual,pudiendo adherirse los pacientes de manera diferente a sus diversos fármacos prescritos.Sidorkiewicz y colaboradores publicaron un cuestionario para evaluar la adherencia a cadafármaco tomado por el paciente. Método: Este estudio valora la validez predictiva de la ver-sión espa˜nola del cuestionario de Sidorkiewicz en una muestra de 470 pacientes ambulatoriospsiquiátricos consecutivos que usaban 897 fármacos psiquiátricos. Resultados: El cuestionariomostró una adecuada validez predictiva, tanto en análisis univariados como multivariados(regresión logística y CHAID), registrándose asociaciones significativas con el DAI-10 y con lasescalas de Necesidad y Preocupación del BMQ. Algunas variables sociodemográficas y clínicasfueron significativas en el análisis univariado perdiendo su significación en el multivariado.Conclusiones: La adherencia del paciente psiquiátrico al tratamiento no está condicionada porcaracterísticas sociodemográficas o clínicas, sino por actitudes hacia la medicación y por laspercepciones de necesidad personal de la medicación y preocupaciones sobre sus posibles efec-tos adversos. La versión espa˜nola del cuestionario de Sidorkiewicz es un instrumento válidopara evaluar la adherencia a cada fármaco tomado por pacientes psiquiátricos ambulatoriospolimedicados

Tesis doctoral: Análisis del contenido en agua en formaciones salinas. Su aplicación al almacenamiento de residuos radioactivos

Rock salt formations are one of the suitable host rocks for high radioactive waste disposal. Among the site selection criteria, one of great importance is the presence of water in the host rock. Due to their genesis and to their mineralogical composition salt formations always contain small amounts of water. This water can be present as interstitial brine, in hydrated minerals and as intragranular fluid inclusions. In order to define the range of water content present in rock salt, as well as its relation between mineralogy and stratigraphical position, five rock salt types have been studied. For each sample water content and also mineralogical analysis has been performed. In most of the studied samples water is present as interstitial bnne and fluid inclusions. In some cases water can also be present in form of hydrated minerals. The distribution of the water content is usually of lognormal type. In some rock salt formations, severa1 subpopulations could be found. Total water content ranges from 0.01 to 3.50%.Mathematical treatment on the aforementioned data consisted of the estimation of the error related to the sampling procedure, statistical tests (univariant, ANOVA, correlation, PCA and trend analysis) and Geostatistics. These treatments have allowed to discern between waternch and water-poor rock salt and also to confirm that there are three factors controlling the amount of water content: mineralogical composition, halitic lithofacies and degree of tectonic stresses. Geostatistical analysis has shown that for detailed characterization purposes a sarnpling interval of 1 m is convenient, whereas for a first characterization of a salt formation a sampling interval of 5 m seems reasonable.Finally, trend analysis has confirmed that along a rock salt formation, alternancy of water-rich and water-poor zones may exist. The methodology described in this study can be very useful for site characterization purposes. Data arising from laboratory research on the aforementioned parameters combined with safety assessment methods can provide the technical basis to decide whether the proposed disposal site offers a satisfactory leve1 of safety

Comparación metodológica de la determinación del contenido en agua en rocas salinas mediante titulación de Karl Fischer y termogravimetría

Water rnay be present in geological formations, filling pores, as fluid inclusions or as hydrated minerals. This study shows a comparison different methodologies in the determination of the water content in rock salt subsamples, using Karl Fischer titration and thermogravimetry, in order to establish an efficient and routinary analytical methodology for water content determination. The study has shown significant discrepancies in the water content results for the same samples, depending on the methodology and the granulometry selected

Aplicación del análisis geoestadístico al diseño de programas de muestreos en formaciones salinas

Water content in salt formations is a regionalised variable rather than a random variable. This means that the yield of the variable in one location varies very slightly from that of close locations. This paper focus on the minimisation of uncertainties of the water content caused by spatial variability and limited number of samples, in order to assess optimised sampling intervals for representative sampling procedures in salt formations. Geostatistical analyses have been performed using small-scale and large-scale sampling intervals in several salt formations. Results show that geostatistical analyses can be successfully used, provided that the dimensions of the studied rockbody do not exceed the range of the regionalised variable by more than one order of magnitude. Otherwise, a simple statistical approximation should provide the degree of accuracy needed when estimating sample means

Algunas reflexiones metodológicas sobre la evaluación coste-beneficio de la sanidad

The recent literature on cost-benefit analysis in Health Economics normally follows the methodology accepted by the Environmental Economics rather than the classical Human Capital hypothesis adopted successfully by the Economics of Education. In this paper we try to argue what could be the main reasons for such an investigation line.La literatura reciente en la evaluación coste-beneficio de los proyectos sanitarios prefiere seguir la línea de la economía medioambiental y acercarse a una posición welfarista en la determinación de los cambios en el bienestar que continuar la hipótesis del capital humano, que había proporcionado en las últimas décadas unos notables resultados en los modelos de evaluación coste beneficio en la Economía de la Educación