Explicit Local Integrals of Motion for the Many-Body Localized State

Recently, it has been suggested that the Many-Body Localized phase can be characterized by local integrals of motion. Here we introduce a Hilbert space preserving renormalization scheme that iteratively finds such integrals of motion exactly. Our method is based on the consecutive action of a similarity transformation using displacement operators. We show, as a proof of principle, localization and the delocalization transition in interacting fermion chains with random onsite potentials. Our scheme of consecutive displacement transformations can be used to study Many Body Localization in any dimension, as well as disorder-free Hamiltonians.Comment: 5 pages, 2 figures, and Supplementary Information. Second version contains new numerical result

Construction of Many-Body Eigenstates with Displacement Transformations

Many-body eigenstates beyond the gaussian approximation can be constructed in terms of local integrals of motion (IOM), although their actual computation has been until now a daunting task. We present a new practical computation of IOMS based on displacement transformations. It represents a general and systematic way to extend Hartree-Fock and configuration interaction theories to higher order. Our method combines minimization of energy and energy variance of a reference state with exact diagonalization. We show that our implementation is able to perform ground state calculations with high precision for relatively large systems. Since it keeps track of the IMO's forming a reference state, our method is particularly efficient dealing with excited states, both in accuracy and the number of different states that can be constructed

Análisis clínico y posturográfico en ancianos con patología vestibular y su relación con las caídas

RESUMEN INTRODUCCIÓN: El equilibrio postural se logra merced a la interacción entre los receptores sensoriales localizados en los sistemas vestibular, visual y somatosensorial, el Sistema Nervioso Central y los arcos reflejos musculares esqueléticos. Las enfermedades vestibulares pueden originar una alteración postural que contribuya a la mayor incidencia de caídas en los ancianos. El control postural puede estudiarse mediante test clínicos o a través de un estudio instrumental (posturografía), el cual permite objetivar y cuantificar aspectos estático y dinámicos del equilibrio e incluso incorporar pasillos de marcha para conocer las características biomecánicas de la misma. OBJETIVOS: 1) Determinar si existen diferencias en el número de caídas, los resultados de un conjunto de test clínicos específicos de equilibrio y el estudio instrumental practicado mediante el sistema NedSVE/IBV entre ancianos normales y con patología vestibular; 2) Establecer las correlaciones entre test clínicos, estudio instrumental y caídas, 3) Conocer la relación entre el estado de compensación vestibuloocular y el control postural de la muestra estudiada. MATERIAL Y MÉTODOS: se estudian 120 sujetos (60 normales, 60 patológicos). Los patológicos se dividen en 4 subgrupos de diagnóstico clínico; los patológicos periféricos se dividen según el estado de compensación vestibular. Toda la muestra estudiada realizó 4 test clínicos (tiempos de apoyo unipodal, Timed Up and Go, test de Tinetti y test de Berg) y un estudio instrumental (posturografía estática, límites de estabilidad, pruebas de control rítmico y direccional y estudio de la marcha) RESULTADOS. A) Caídas: Los pacientes tuvieron significativamente mayor número de caídas que los sujetos normales. El número de caídas en los subgrupos de diagnóstico clínico y según el estado de compensación vestibular fue muy similar. B) Test clínicos: alta correlación de los resultados de los test clínicos con el número de caídas. No se observaron diferencias significativas entre los grupos y subgrupos comparados. C) Posturografía estática: la mejor condición para discriminar sujetos normales de patológicos y a éstos según su compensación vestibular, fue la de RGA. Sólo finalizaron la condición de RGC 46 sujetos normales y 22 patológicos. Múltiples correlaciones entre los test clínicos y las oscilaciones posturales en RGA. El desplazamiento máximo anteroposterior en ROA fue el único parámetro que se correlacionó con el número de caídas. D) Límites de estabilidad y de control rítmico-direccional: No diferencias significativas entre los grupos y subgrupos estudiados. Escasa correlación con test clínicos. No correlación con caídas. E) Marcha: parámetros cinemáticos: amplia correlación con test clínicos pero no correlación con caídas; parámetros cinéticos: escaso valor para distinguir entre los distintos subgrupos. Múltiples correlaciones con los test clínicos. Muy escasa correlación con el número de caídas durante el año anterior al estudio. CONCLUSIONES. Los pacientes sufrieron más caídas que los sujetos normales. El número de caídas se correlacionó bien con los resultados de los test clínicos pero no con el estudio instrumental. La condición de RGA fue la más útil para conocer el estado funcional del equilibrio. Los resultados de las pruebas de límites de estabilidad y control rítmico direccional fueron muy similares en los diferentes subgrupos estudiados. La velocidad fue el parámetro de la marcha mejor correlacionado con los test clínicos. __________________________________________________________________________________________________INTRODUCTION: vestibular disorders can origine postural disturbances and contribute to the higher incidence of falls among the elderly. The balance can be studied through clinical tests or through a posturography system, which allows quantify static and dynamic aspects of balance. OBJECTIVES: 1) To determine whether there are differences in the number of falls, the clinical tests and the posturographic studies (NedSVE / IBV) among normal and vestibular old patients; 2) To establish correlations among clinical tests, posturographic studies and falls, 3) To know the relationship between the vestibular compensation and postural control of the sample studied. MATERIALS AND METHODS: we studied 120 subjects (60 normal, 60 pathological). Patients were divided into clinical diagnosis groups. All sample made 4 clinical tests (one leg standing, Timed Up and Go, Tinetti test and the Berg Balance Scale) and a posturographic study (static posturography, stability limits, rhythmic weight shift and gait analysis) RESULTS. A) Falls: patients had more greater number of falls that normal subjects. B) Clinical Tests: high correlation with the number of falls. No significant differences among the compared groups and subgroups. C) Static posturography: the RGA was the best condition to discriminate pathological and normal subjects and the compensated vs. non compensated patients. A lot of normal people and patients didnt finish RGC condition. Multiple correlations among clinical tests and postural oscilations in RGA. D) Stability limits and rhythmic weight shift: No significant differences among the groups and subgroups studied. Low correlation with clinical tests. No correlation with falls. E) Gait: kinematic parameters: good correlations with clinical tests but not with the number of falls; kinetic parameters: good correlation with clinical tests. Poor correlation with the number of falls. CONCLUSIONS. Patients had more falls than normal subjects. The number of falls was correlated with the clinical tests but not with the posturographic studies. The RGA condition was the most useful in order to know the functional status of balance. The stability limits and rhythmic weight shift results were similar in the studied subgroups. Velocity was the gait parameter better correlated with the clinical tests

Dielectric susceptibility of the Coulomb-glass

We derive a microscopic expression for the dielectric susceptibility X of a Coulomb glass, which corresponds to the definition used in classical electrodynamics, the derivative of the polarization with respect to the electric field. The fluctuation–dissipation theorem tells us that is a function of the thermal fluctuations of the dipole moment of the system. We calculate X numerically for three–dimensional Coulomb glasses as a function of temperature and frequency.We acknowledge financial support from the DGES project number PB96-1118, SMWK, and DFG (SFB 393). A great part of this work was performed during A. D.-S.’s visit at the IFW Dresden; A. D.-S. thanks the IFW for its hospitality

Abbreviated dynamic souce ruoting: source routing with not-unique network identifiers

Current ad-hoc network protocols are designed for host similar to those used in fixed networks. Those protocols are not adequate for some applications of ad-hoc networks, where used resources are very scarce. One example is the size of the network addresses, which may be a critical issue, specially whit the use of IPv6 in DRS. This is due to the fact that this protocol uses souece ruoting, so each datagram must carry the sddresses of all the machines in its path. In this paper a new protocol named ADSR is proposed the solve this problem. This new protocol is a modified version of DSR based on using abbreviated addresses. The abreviation procedure can lead to two different nodes having the same address, what we will named "collision

Communications for cooperation: the RoboCup 4-legged passing challenge

Communications are the basis for the collaborative activities in the TeamChaos 4-legged team. In this paper we present the communications architecture developed both to let teammates communicate, and to easy the debugging of robot behaviors from external computers. Details of its implementation on the aiBo robots are also given. Using this infrastructure we describe a protocol for role exchange named Switch! that we have created. We also describe the use of both the communication architecture, and the Switch! protocol in the passing challenge of the 2006 edition of the RoboCu

Current-Driven Production of Vortex-Antivortex Pairs in Planar Josephson Junction Arrays and Phase Cracks in Long-Range Order

Proliferation of topological defects like vortices and dislocations plays a key role in the physics of systems with long-range order, particularly, superconductivity and superfluidity in thin films, plasticity of solids, and melting of atomic monolayers. Topological defects are characterized by their topological charge reflecting fundamental symmetries and conservation laws of the system. Conservation of topological charge manifests itself in extreme stability of static topological defects because destruction of a single defect requires overcoming a huge energy barrier proportional to the system size. However, the stability of driven topological defects remains largely unexplored. Here we address this issue and investigate numerically a dynamic instability of moving vortices in planar arrays of Josephson junctions. We show that a single vortex driven by sufficiently strong current becomes unstable and destroys superconductivity by triggering a chain reaction of self-replicating vortex-antivortex pairs forming linear of branching expanding patterns. This process can be described in terms of propagating phase cracks in long-range order with far-reaching implications for dynamic systems of interacting spins and atoms hosting magnetic vortices and dislocations

Systemic models as optimization tool for territory design: Case study

[EN] The objective of this research is the optimized design of the territory with respect to the sustainability of systems belonging to the "new rurality", based on action research, through the use of systemic models, which intend to carry out a design of the territory, according to the use of the new technologies and with the consideration of the socioeconomic and technical aspects of local development. For this, two cases belonging to the Colombian territory have been studied, in matters related to emerging systems of the territory. The use of systemic models has enabled the approach and simulation of the models, which represent the territory and therefore of decision-making, which allow the optimization of available resources in units considered as sustainability modules. The initial results suggest the extraction of knowledge necessary for systemic implementation. The results obtained allow the achievement of objectives and their final representation.Hernandis Ortuño, B.; Esnal, I.; Agustín Fonfría, MÁ.; Arzuza, AJ.; Arévalo, D. (2020). Systemic models as optimization tool for territory design: Case study. Projética. 11(3):45-69. https://doi.org/10.5433/2236-2207.2020v11n3esp.p45S456911

Role of Anions in 5-Hydroxymethylfurfural Solvation in Ionic Liquids from Molecular Dynamics Simulations

The proper selection of solvents for biomass upgrading is a crucial task as it should carefully balance the enhancement of reactivity with a facile product recovery. A challenging case is the conversion of glucose and fructose to 5-hydroxymethylfurfural (HMF). Ionic liquids (ILs) are often employed to boost the activity and selectivity of this process, although the isolation of HMF from the medium remains a major drawback. To investigate such solvent effects in a realistic (dynamic) environment, classical molecular dynamics (MD) simulations of HMF are performed in imidazolium-based ILs with different anions. Several parameters are identified that directly control HMF–anion interactions, which may hamper product separation, as well as HMF–HMF contacts, which can promote undesired side-reactions. These computational results would guide future high-throughput screenings of new and improved IL mediaThis work was funded by the Spanish Ministry of Economy and Competitiveness (under projects MAT2017-89239-C2-1-P and PID2020-119116RA-I00) and by the Xunta de Galicia (ED431D 2017/06, ED431E 2018/08, GRC ED431C 2016/001, and GRC ED431C 2020/10). All these projects were partially supported by FEDER. H.M.C. thanks the USC for his “Convocatoria de Recualificación do Sistema Universitario Español-Margarita Salas” postdoctoral grant under the “Plan de Recuperación Transformación” program funded by the Spanish Ministry of Universities with European Union's NextGenerationEU funds. T.M.M. acknowledges her contract funded by the pilot program of the USC for the recruitment of distinguished research personnel—call 2021 under the agreement between the USC and the Santander Bank for 2021–2024. M.A.O. acknowledges the Xunta Distinguished Researcher program (ED431H 2020/21), the Xunta de Galicia (Centro singular de investigación de Galicia accreditation 2019–2022, ED431G 2019/03), and the European Union (European Regional Development Fund – ERDF) for funding. He also acknowledges CESGA (“Centro de Supercomputación de Galicia”) for providing computational resourcesS

Dirección discriminante para el encaminamiento: un nuevo tipo de identificador para la computación ubicua

Any device we want to be ab le connect to a global network should have an unique global identifier. The size of this identifier can be an unaceptable overhead for devices with limited resources (sensors, toys, disposable devices, microrobots, etc.), because conventional protocols use full addresses to transmit, process and store the data required for routing. The usual solution for such devices is to limit the address space to one or two bytes, but this sacrifices the global unicity of the identifiers. Another more drastic maesure is to without any routing at al