324 research outputs found
Phase of bi-particle localized states for the Cooper problem in two-dimensional disordered systems
The Cooper problem is studied numerically for the Anderson model with
disorder in two-dimensions. It is shown that the attractive Hubbard interaction
creates a phase of bi-particle localized states in the regime where
non-interacting states are delocalized. This phase cannot be obtained in the
mean-field approximation and the pair coupling energy is strongly enhanced in
this regime. The effects of magnetic field are studied and it is shown that
under certain conditions they lead to delocalization.Comment: revtex, 7 pages, 8 figure
Recommended from our members
Positively and negatively valenced customer engagement: the constructs and their organizational consequences
Until recently, the majority of academic research on customer engagement (CE) has
focused on the conceptâs positive valence that reflects consumersâ favorable brand-related
cognitions, emotions, and behaviors, which typically contribute positively to brand performance.
While the existence of negative CE manifestations has been recognized, little is known regarding
their particular expressions, characteristics, and position in the broader nomological network, as
explored in this chapter. While the antecedents and consequences of unidimensional and
multidimensional negatively valenced CE (NVCE) have been explored in the literature, the
consequences of multidimensional NVCE, particularly those at the organizational level, remain
nebulous, as explored in this chapter. In addition, we examine organizational-level consequences
of positively valenced CE (PVCE) that are contrasted to those of NVCE. To achieve these
objectives, we first conceptualize positively and negatively valenced CE, followed by an
exploration of their respective consequences. We conclude by offering specific managerial
recommendations to increase positive CE whilst halting the conceptâs negative expressions
First In-Situ Measurements of Plume Chemistry at Mount Garet Volcano, Island of Gaua (Vanuatu)
Recent volcanic gas compilations have urged the need to expand in-situ plume measurements to poorly studied, remote volcanic regions. Despite being recognized as one of the main volcanic epicenters on the planet, the Vanuatu arc remains poorly characterized for its subaerial emissions and their chemical imprints. Here, we report on the first plume chemistry data for Mount Garet, on the island of Gaua, one of the few persistent volatile emitters along the Vanuatu arc. Data were collected with a multi-component gas analyzer system (multi-GAS) during a field campaign in December 2018. The average volcanic gas chemistry is characterized by mean molar CO2/SO2, H2O/SO2, H2S/SO2 and H2/SO2 ratios of 0.87, 47.2, 0.13 and 0.01, respectively. Molar proportions in the gas plume are estimated at 95.9 ± 11.6, 1.8 ± 0.5, 2.0 ± 0.01, 0.26 ± 0.02 and 0.06 ± 0.01, for H2O, CO2, SO2, H2S and H2. Using the satellite-based 10-year (2005â2015) averaged SO2 flux of ~434 t dâ1 for Mt. Garet, we estimate a total volatile output of about 6482 t dâ1 (CO2 ~259 t dâ1; H2O ~5758 t dâ1; H2S ~30 t dâ1; H2 ~0.5 t dâ1). This may be representative of a quiescent, yet persistent degassing period at Mt. Garet; whilst, as indicated by SO2 flux reports for the 2009â2010 unrest, emissions can be much higher during eruptive episodes. Our estimated emission rates and gas composition for Mount Garet provide insightful information on volcanic gas signatures in the northernmost part of the Vanuatu Arc Segment. The apparent CO2-poor signature of high-temperature plume degassing at Mount Garet raises questions on the nature of sediments being subducted in this region of the arc and the possible role of the slab as the source of subaerial CO2. In order to better address the dynamics of along-arc volatile recycling, more volcanic gas surveys are needed focusing on northern Vanuatu volcanoes
Decoherence by a chaotic many-spin bath
We numerically investigate decoherence of a two-spin system (central system)
by a bath of many spins 1/2. By carefully adjusting parameters, the dynamical
regime of the bath has been varied from quantum chaos to regular, while all
other dynamical characteristics have been kept practically intact. We
explicitly demonstrate that for a many-body quantum bath, the onset of quantum
chaos leads to significantly faster and stronger decoherence compared to an
equivalent non-chaotic bath. Moreover, the non-diagonal elements of the
system's density matrix decay differently for chaotic and non-chaotic baths.
Therefore, knowledge of the basic parameters of the bath (strength of the
system-bath interaction, bath's spectral density of states) is not always
sufficient, and much finer details of the bath's dynamics can strongly affect
the decoherence process.Comment: 4 pages, RevTeX, 5 eps figure
Relationship of dietary pattern with body composition and symptoms in patients with COPD
This study explored the relationship of dietary patterns with body composition and symptoms in patients with COPD. Data collection included: dietary pattern â n. meals/day; period of the day of highest food intake (morning [6 AMâ12 PM], afternoon [12â18 PM], and evening [18 PMâ6 AM]); the time interval between meals (3-4h, 5-6h, 9-10h), and daily energy and nutrient intake using a semiquantitative food frequency questionnaire (last 12 months); body composition â body mass index (BMI), % fat mass (%FM), % fat-free mass (%FFM), % total muscle mass (%MM), fat-free mass index (FFMI) and visceral fat index (VAT) (SECA mBCA 525); symptoms â dyspnoea (modified Medical Research Council Dyspnea Scale, mMRC), fatigue (Checklist of Individual Strength, CIS20-P total score), impact of COPD (COPD Assessment Test, CAT). Pearsonâs (r) or Spearmanâs (Ï) correlations were conducted. 18 patients participated (16 males, 68±7 years old, FEV1 43±20% predicted, BMI 25±5kg/m2, FFMI 18±3kg/m2). Most participants reported having 3-4 meals/day (n=14, 78%) with a 3-4-hour interval (n=15, 83%). Moderate correlations were found between %FM and carbohydrates (Ï=-.501) and between FFMI and monosaturated fat (r=.476) (p.05). Energy and nutrient intake are related to COPD symptoms and body composition. The nature of these relationships should be explored.info:eu-repo/semantics/publishedVersio
First in-situ measurements of plume chemistry at mount garet volcano, island of gaua (Vanuatu)
Recent volcanic gas compilations have urged the need to expand in-situ plume measurements to poorly studied, remote volcanic regions. Despite being recognized as one of the main volcanic epicenters on the planet, the Vanuatu arc remains poorly characterized for its subaerial emissions and their chemical imprints. Here, we report on the first plume chemistry data for Mount Garet, on the island of Gaua, one of the few persistent volatile emitters along the Vanuatu arc. Data were collected with a multi-component gas analyzer system (multi-GAS) during a field campaign in December 2018. The average volcanic gas chemistry is characterized by mean molar CO2 /SO2, H2 O/SO2, H2 S/SO2 and H2 /SO2 ratios of 0.87, 47.2, 0.13 and 0.01, respectively. Molar proportions in the gas plume are estimated at 95.9 ± 11.6, 1.8 ± 0.5, 2.0 ± 0.01, 0.26 ± 0.02 and 0.06 ± 0.01, for H2 O, CO2, SO2, H2 S and H2 . Using the satellite-based 10-year (2005â2015) averaged SO2 flux of ~434 t dâ1 for Mt. Garet, we estimate a total volatile output of about 6482 t dâ1 (CO2 ~259 t dâ1; H2 O ~5758 t dâ1; H2 S ~30 t dâ1; H2 ~0.5 t dâ1 ). This may be representative of a quiescent, yet persistent degassing period at Mt. Garet; whilst, as indicated by SO2 flux reports for the 2009â2010 unrest, emissions can be much higher during eruptive episodes. Our estimated emission rates and gas composition for Mount Garet provide insightful information on volcanic gas signatures in the northernmost part of the Vanuatu Arc Segment. The apparent CO2-poor signature of high-temperature plume degassing at Mount Garet raises questions on the nature of sediments being subducted in this region of the arc and the possible role of the slab as the source of subaerial CO2 . In order to better address the dynamics of along-arc volatile recycling, more volcanic gas surveys are needed focusing on northern Vanuatu volcanoes
Cooper problem in the vicinity of Anderson transition
We study numerically the ground state properties of the Cooper problem in the
three-dimensional Anderson model. It is shown that attractive interaction
creates localized pairs in the metallic noninteracting phase. This localization
is destroyed at sufficiently weak disorder. The phase diagram for the
delocalization transition in the presence of disorder and interaction is
determined.Comment: revtex, 4 pages, 4 figure
Transition to an Insulating Phase Induced by Attractive Interactions in the Disordered Three-Dimensional Hubbard Model
We study numerically the interplay of disorder and attractive interactions
for spin-1/2 fermions in the three-dimensional Hubbard model. The results
obtained by projector quantum Monte Carlo simulations show that at moderate
disorder, increasing the attractive interaction leads to a transition from
delocalized superconducting states to the insulating phase of localized pairs.
This transition takes place well within the metallic phase of the
single-particle Anderson model.Comment: revtex, 4 pages, 3 figure
On the Inverse Problem of Binocular 3D Motion Perception
It is shown that existing processing schemes of 3D motion perception such as interocular velocity difference, changing disparity over time, as well as joint encoding of motion and disparity, do not offer a general solution to the inverse optics problem of local binocular 3D motion. Instead we suggest that local velocity constraints in combination with binocular disparity and other depth cues provide a more flexible framework for the solution of the inverse problem. In the context of the aperture problem we derive predictions from two plausible default strategies: (1) the vector normal prefers slow motion in 3D whereas (2) the cyclopean average is based on slow motion in 2D. Predicting perceived motion directions for ambiguous line motion provides an opportunity to distinguish between these strategies of 3D motion processing. Our theoretical results suggest that velocity constraints and disparity from feature tracking are needed to solve the inverse problem of 3D motion perception. It seems plausible that motion and disparity input is processed in parallel and integrated late in the visual processing hierarchy
From Feynman Proof of Maxwell Equations to Noncommutative Quantum Mechanics
In 1990, Dyson published a proof due to Feynman of the Maxwell equations
assuming only the commutation relations between position and velocity. With
this minimal assumption, Feynman never supposed the existence of Hamiltonian or
Lagrangian formalism. In the present communication, we review the study of a
relativistic particle using ``Feynman brackets.'' We show that Poincar\'e's
magnetic angular momentum and Dirac magnetic monopole are the consequences of
the structure of the Lorentz Lie algebra defined by the Feynman's brackets.
Then, we extend these ideas to the dual momentum space by considering
noncommutative quantum mechanics. In this context, we show that the
noncommutativity of the coordinates is responsible for a new effect called the
spin Hall effect. We also show its relation with the Berry phase notion. As a
practical application, we found an unusual spin-orbit contribution of a
nonrelativistic particle that could be experimentally tested. Another practical
application is the Berry phase effect on the propagation of light in
inhomogeneous media.Comment: Presented at the 3rd Feynman Festival (Collage Park, Maryland,
U.S.A., August 2006
- âŠ