10,251 research outputs found
Resonating valence bond states in the PEPS formalism
We study resonating valence bond (RVB) states in the Projected Entangled Pair
States (PEPS) formalism. Based on symmetries in the PEPS description, we
establish relations between the toric code state, the orthogonal dimer state,
and the SU(2) singlet RVB state on the kagome lattice: We prove the equivalence
of toric code and dimer state, and devise an interpolation between the dimer
state and the RVB state. This interpolation corresponds to a continuous path in
Hamiltonian space, proving that the RVB state is the four-fold degenerate
ground state of a local Hamiltonian on the (finite) kagome lattice. We
investigate this interpolation using numerical PEPS methods, studying the decay
of correlation functions, the change of overlap, and the entanglement spectrum,
none of which exhibits signs of a phase transition.Comment: 11+9 pages, 28 figures. v2: More numerical results, and a few minor
improvements. v3: Accepted version (minor changes relative to v2),
Journal-Ref adde
Red-giant stars in eccentric binaries
The unparalleled photometric data obtained by NASA’s Kepler Space Telescope has led to improved understanding of red-giant stars and binary stars. We discuss the characterization of known eccentric system, containing a solar-like oscillating red-giant primary component. We also report several new binary systems that are candidates for hosting an oscillating companion. A powerful approach to study binary stars is to combine asteroseimic techniques with light curve fitting. Seismology allows us to deduce the properties of red giants. In addition, by modeling the ellipsoidal modulations we can constrain the parameters of the binary system. An valuable independent source are ground-bases, high-resolution spectrographs
Fundamental limitations in the purifications of tensor networks
We show a fundamental limitation in the description of quantum many-body
mixed states with tensor networks in purification form. Namely, we show that
there exist mixed states which can be represented as a translationally
invariant (TI) matrix product density operator (MPDO) valid for all system
sizes, but for which there does not exist a TI purification valid for all
system sizes. The proof is based on an undecidable problem and on the
uniqueness of canonical forms of matrix product states. The result also holds
for classical states.Comment: v1: 11 pages, 1 figure. v2: very minor changes. About to appear in
Journal of Mathematical Physic
Multiscale understanding of tricalcium silicate hydration reactions
Tricalcium silicate, the main constituent of Portland cement, hydrates to produce crystalline calcium
hydroxide and calcium-silicate-hydrates (C-S-H) nanocrystalline gel. This hydration reaction is poorly
understood at the nanoscale. The understanding of atomic arrangement in nanocrystalline phases is
intrinsically complicated and this challenge is exacerbated by the presence of additional crystalline
phase(s). Here, we use calorimetry and synchrotron X-ray powder diffraction to quantitatively follow
tricalcium silicate hydration process: i) its dissolution, ii) portlandite crystallization and iii) C-S-H
gel precipitation. Chiefly, synchrotron pair distribution function (PDF) allows to identify a defective
clinotobermorite, Ca11Si9O28(OH)2.8.5H2O, as the nanocrystalline component of C-S-H. Furthermore,
PDF analysis also indicates that C-S-H gel contains monolayer calcium hydroxide which is stretched
as recently predicted by first principles calculations. These outcomes, plus additional laboratory
characterization, yielded a multiscale picture for C-S-H nanocomposite gel which explains the observed
densities and Ca/Si atomic ratios at the nano- and meso- scales.This work has been supported by Spanish MINECO through BIA2014-57658-C2-2-R, which is co-funded by
FEDER, BIA2014-57658-C2-1-R and I3 (IEDI-2016-0079) grants. We also thank CELLS-ALBA (Barcelona,
Spain) for providing synchrotron beam time at BL04-MSPD beamline
Análisis del entrenamiento pliométrico como trabajo de transferencia de la electroestimulación neuromuscular
Peer Reviewe
Participatory Militias: An Analysis of an Armed Movement's Online Audience
Armed groups of civilians known as "self-defense forces" have ousted the
powerful Knights Templar drug cartel from several towns in Michoacan. This
militia uprising has unfolded on social media, particularly in the "VXM"
("Valor por Michoacan," Spanish for "Courage for Michoacan") Facebook page,
gathering more than 170,000 fans. Previous work on the Drug War has documented
the use of social media for real-time reports of violent clashes. However, VXM
goes one step further by taking on a pro-militia propagandist role, engaging in
two-way communication with its audience. This paper presents a descriptive
analysis of VXM and its audience. We examined nine months of posts, from VXM's
inception until May 2014, totaling 6,000 posts by VXM administrators and more
than 108,000 comments from its audience. We describe the main conversation
themes, post frequency and relationships with offline events and public
figures. We also characterize the behavior of VXM's most active audience
members. Our work illustrates VXM's online mobilization strategies, and how its
audience takes part in defining the narrative of this armed conflict. We
conclude by discussing possible applications of our findings for the design of
future communication technologies.Comment: Participatory Militias: An Analysis of an Armed Movement's Online
Audience. Saiph Savage, Andres Monroy-Hernandez. CSCW: ACM Conference on
Computer-Supported Cooperative Work 201
Luxación tibio astragalina posteromedial sin fractura de maleolos: a propósito de un caso
Se describe un caso de luxación tibioastragalina posteromedial abierta sin fractura
asociada de maleolos, en un paciente de 28 años. A los dos años del desbridamiento quirúrgico,
reducción manual y reparación capsuloligamentosa, el paciente estaba libre de dolor y
presentaba una función semejante a la del tobillo contralateral. Se revisa la literatura sobre el
tema y se discuten los factores etiopatológicos, complicaciones y principios de tratamiento
Fracturas de cadera y diáfisis femoral ipsilaterales
Se aportan 10 casos de fracturas de cadera y diáfisis femoral ipsilaterales tratados
quirúrgicamente de forma diferida con un tiempo medio de demora de 12 días (rango: 3 a
22 días). Nueve fracturas diafisarias fueron tratadas con placa AO de fémur, y una, donde la
fractura de cadera asociada pasó inicialmente inadvertida, mediante un clavo de Küntscher. Las
fracturas de cadera se fijaron con tornillos de esponjosa (8 casos) o clavo-placa de Richards (2
casos). En todos los pacientes se inició un programa de rehabilitación precoz. El seguimiento
medio ha sido de 31 meses (rango: 12 a 84 meses). Todas las fracturas consolidaron. Las complicaciones
fueron un caso de acortamiento femoral y otro de artrosis coxofemoral post-traumá-
tica. En nuestra experiencia, la fijación de la fractura diafisaria con placa AO, combinada con
tornillos de esponjosa o clavo-placa de Richards para la síntesis de la fractura de cadera, proporciona
resultados satisfactoriosWe review 10 cases of ipsilateral hip and femoral shaft fractures. Operative treatment
was performed in all cases, with an average delay of 12 days (range: 3 to 22 days). Nine
femoral shaft fractures were stabilizated with an AO plate, and one, where the associated hip
fracture was initially missed, with a Küntscher rod. Hip fractures were fixed with cancellous
screws (8 cases) or Richards compression screw (2 cases). An early rehabilitation program was
carried out in all patients. The average follow-up was 31 months (range: 12 to 84 months). All
fractures healed. Complications were a case of femoral shortening an a case of post-traumatic
hip osteoarthritis. In our study, the combination of AO plate for the shaft fracture with cancellous
screws or Richards compression screw for the hip fracture provides good results
The KINDRA project – towards Open Science in Hydrogeology for higher impact
Groundwater knowledge and research in the European Union is often scattered and non-standardised. Therefore, KINDRA is conducting an EU-wide assessment of existing groundwater-related practical and scientific knowledge based on a new Hydrogeological Research Classification System (HRC-SYS). The classification is supported by a web service, the European Inventory of Groundwater Research (EIGR), which acts not only as a knowledge repository but also as a tool to help identify relevant research topics, existing research trends and critical research challenges. These results will be useful for
producing synergies, implementing policies and optimising water management in Europe. This article presents the work of the project during the first two years in relation to a common classification system and an activity for data collection and training delivered by the EFG’s National Associations in 20 European countries
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