835 research outputs found
Access to diagnosis and treatment of Chagas disease/infection in endemic and non-endemic countries in the XXI century.
In this article, Médicos Sin Fronteras (MSF) Spain faces the challenge of selecting, piecing together, and conveying in the clearest possible way, the main lessons learnt over the course of the last seven years in the world of medical care for Chagas disease. More than two thousand children under the age of 14 have been treated; the majority of whom come from rural Latin American areas with difficult access. It is based on these lessons learnt, through mistakes and successes, that MSF advocates that medical care for patients with Chagas disease be a reality, in a manner which is inclusive (not exclusive), integrated (with medical, psychological, social, and educational components), and in which the patient is actively followed. This must be a multi-disease approach with permanent quality controls in place based on primary health care (PHC). Rapid diagnostic tests and new medications should be available, as well as therapeutic plans and patient management (including side effects) with standardised flows for medical care for patients within PHC in relation to secondary and tertiary level, inclusive of epidemiological surveillance systems
Superconducting pairing of interacting electrons: implications from the two-impurity Anderson model
We study the non-local superconducting pairing of two interacting Anderson
impurities, which has an instability near the quantum critical point from the
competition between the Kondo effect and an antiferromagnetic inter-impurity
spin exchange interaction. As revealed by the dynamics over the whole energy
range, the superconducting pairing fluctuations acquire considerable strength
from an energy scale much higher than the characteristic spin fluctuation scale
while the low energy behaviors follow those of the staggered spin
susceptibility. We argue that the glue to the superconducting pairing is not
the spin fluctuations, but rather the effective Coulomb interaction. On the
other hand, critical spin fluctuations in the vicinity of quantum criticality
are also crucial to a superconducting pairing instability, by preventing a
Fermi liquid fixed point being reached to keep the superconducting pairing
fluctuations finite at low energies. A superconducting order, to reduce the
accumulated entropy carried by the critical degrees of freedom, may arise
favorably from this instability.Comment: 6 pages, 2 figure
Singular dynamics and pseudogap formation in the underscreened Kondo impurity and Kondo lattice models
We study a generalization of the Kondo model in which the impurity spin is
represented by Abrikosov fermions in a rotation group SU(P) larger than the
SU(N) group associated to the spin of the conduction electrons, thereby forcing
the single electronic bath to underscreen the localized moment. We demonstrate
how to formulate a controlled large N limit preserving the property of
underscreening, and which can be seen as a ``dual'' theory of the multichannel
large N equations usually associated to overscreening. Due to the anomalous
scattering on the uncompensated degrees of freedom, the Fermi liquid
description of the electronic fluid is invalidated, with the logarithmic
singularities known to occur in the S=1 SU(2) Kondo impurity model being
replaced by continuous power laws at N=\infty. The present technique can be
extended to tackle the related underscreened Kondo lattice model in the large N
limit. We discover the occurence of an insulating pseudogap regime in place of
the expected renormalized metallic phase of the fully screened case, preventing
the establishement of coherence over the lattice. This work and the recent
observation of a similar weakly insulating behavior on transport in CeCuAs_2
should give momentum for further studies of underscreened impurity models on
the lattice.Comment: 9 pages, 3 figures. Several modifications in published version,
including new title, further details on the interpretation of the formalism
and possible experimental connection
Spectral scaling and quantum critical behaviour in the pseudogap Anderson model
The pseudogap Anderson impurity model provides a classic example of an
essentially local quantum phase transition. Here we study its single-particle
dynamics in the vicinity of the symmetric quantum critical point (QCP)
separating generalized Fermi liquid and local moment phases, via the local
moment approach. Both phases are shown to be characterized by a low-energy
scale that vanishes at the QCP; and the universal scaling spectra, on all
energy scales, are obtained analytically. The spectrum precisely at the QCP is
also obtained; its form showing clearly the non-Fermi liquid, interacting
nature of the fixed point.Comment: 7 pages, 2 figure
A spin-dependent local moment approach to the Anderson impurity model
We present an extension of the local moment approach to the Anderson impurity
model with spin-dependent hybridization. By employing the two-self-energy
description, as originally proposed by Logan and co-workers, we applied the
symmetry restoration condition for the case with spin-dependent hybridization.
Self-consistent ground states were determined through variational minimization
of the ground state energy. The results obtained with our spin-dependent local
moment approach applied to a quantum dot system coupled to ferromagnetic leads
are in good agreement with those obtained from previous work using numerical
renormalization group calculations
Single-particle dynamics of the Anderson model: a two-self-energy description within the numerical renormalization group approach
Single-particle dynamics of the Anderson impurity model are studied using
both the numerical renormalization group (NRG) method and the local moment
approach (LMA). It is shown that a 'two-self-energy' description of dynamics
inherent to the LMA, as well as a conventional 'single-self-energy'
description, arise within NRG; each yielding correctly the same local
single-particle spectrum. Explicit NRG results are obtained for the broken
symmetry spectral constituents arising in a two-self-energy description, and
the total spectrum. These are also compared to analytical results obtained from
the LMA as implemented in practice. Very good agreement between the two is
found, essentially on all relevant energy scales from the high-energy Hubbard
satellites to the low-energy Kondo resonance.Comment: 12 pages, 6 figure
Quantum Monte Carlo calculation of the finite temperature Mott-Hubbard transition
We present clear numerical evidence for the coexistence of metallic and
insulating dynamical mean field theory(DMFT) solutions in a half-filled
single-band Hubbard model with bare semicircular density of states at finite
temperatures. Quantum Monte Carlo(QMC) method is used to solve the DMFT
equations. We discuss important technical aspects of the DMFT-QMC which need to
be taken into account in order to obtain the reliable results near the
coexistence region. Among them are the critical slowing down of the iterative
solutions near phase boundaries, the convergence criteria for the DMFT
iterations, the interpolation of the discretized Green's function and the
reduction of QMC statistical and systematic errors. Comparison of our results
with those of other numerical methods is presented in a phase diagram.Comment: 4 pages, 5 figure
Uncovering Values: Detecting Latent Moral Content from Natural Language with Explainable and Non-Trained Methods
Moral values as commonsense norms shape our everyday individual and community behavior. The possibility to extract moral attitude rapidly from natural language is an appealing perspective that would enable a deeper understanding of social interaction dynamics and the individual cognitive and behavioral dimension. In this work we focus on detecting moral content from natural language and we test our methods on a corpus of tweets previously labeled as containing moral values or violations, according to Moral Foundation Theory. We develop and compare two different approaches: (i) a frame-based symbolic value detector based on knowledge graphs and (ii) a zero-shot machine learning model fine-tuned on a task of Natural Language Inference (NLI) and a task of emotion detection. Our approaches achieve considerable performances without the need for prior training
Magnetic properties of the Anderson model: a local moment approach
We develop a local moment approach to static properties of the symmetric
Anderson model in the presence of a magnetic field, focussing in particular on
the strong coupling Kondo regime. The approach is innately simple and
physically transparent; but is found to give good agreement, for essentially
all field strengths, with exact results for the Wilson ratio, impurity
magnetization, spin susceptibility and related properties.Comment: 7 pages, 3 postscript figues. Latex 2e using the epl.cls Europhysics
Letters macro packag
Numerical renormalization group calculation of near-gap peaks in spectral functions of the Anderson model with superconducting leads
We use the numerical renormalization group method (NRG) to investigate a
single-impurity Anderson model with a coupling of the impurity to a
superconducting host. Analysis of the energy flow shows, in contrast to
previous belief, that NRG iterations can be performed up to a large number of
sites, corresponding to energy differences far below the superconducting gap.
This allows us to calculate the impurity spectral function very accurately for
frequencies near the gap edge, and to resolve, in a certain parameter regime,
sharp peaks in the spectral function close to the gap edge.Comment: 18 pages, 7 figures, accepted for publication in Journal of Physics:
Condensed Matte
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