1,494 research outputs found
Non-Universal Behavior of the k-Body Embedded Gaussian Unitary Ensemble of Random Matrices
Using a novel approach, we investigate the shape of the average spectrum and
the spectral fluctuations of the -body embedded unitary ensemble in the
limit of large matrix dimension. We identify the transition point between
semicircle and Gaussian shape. The transition also affects the spectral
fluctuations which deviate from Wigner-Dyson form and become Poissonian in the
limit . Here is the number of Fermions and the number of
degenerate single-particle states.Comment: 4 pages, no figures, revised version including a new proof of one of
our main claim
Phase-Space Volume of Regions of Trapped Motion: Multiple Ring Components and Arcs
The phase--space volume of regions of regular or trapped motion, for bounded
or scattering systems with two degrees of freedom respectively, displays
universal properties. In particular, sudden reductions in the phase-space
volume or gaps are observed at specific values of the parameter which tunes the
dynamics; these locations are approximated by the stability resonances. The
latter are defined by a resonant condition on the stability exponents of a
central linearly stable periodic orbit. We show that, for more than two degrees
of freedom, these resonances can be excited opening up gaps, which effectively
separate and reduce the regions of trapped motion in phase space. Using the
scattering approach to narrow rings and a billiard system as example, we
demonstrate that this mechanism yields rings with two or more components. Arcs
are also obtained, specifically when an additional (mean-motion) resonance
condition is met. We obtain a complete representation of the phase-space volume
occupied by the regions of trapped motion.Comment: 19 pages, 17 figure
Non-Ergodic Behaviour of the k-Body Embedded Gaussian Random Ensembles for Bosons
We investigate the shape of the spectrum and the spectral fluctuations of the
-body Embedded Gaussian Ensemble for Bosons in the dense limit, where the
number of Bosons while both , the rank of the interaction,
and , the number of single-particle states, are kept fixed. We show that the
relative fluctuations of the low spectral moments do not vanish in this limit,
proving that the ensemble is non-ergodic. Numerical simulations yield spectra
which display a strong tendency towards picket-fence type. The wave functions
also deviate from canonical random-matrix behaviourComment: 7 pages, 5 figures, uses epl.cls (included
Recommended from our members
Food, Acid Supplementation and Drug Absorption - a Complicated Gastric Mix: a Randomized Control Trial.
PURPOSE:The purpose of this study was to determine the impact of food on gastric pH and the ability of over the counter betaine hydrochloride (BHCl) acid to reacidify gastric pH after food-induced elevations in gastric pH. METHODS:This open-label cross over clinical study (NCT02758015) included 9 subjects who were randomly assigned to one of 16 possible, 4-period cross-over sequences to determine the impact and relationship of food and gastric pH with acid supplementation. Subjects were administered various doses (1500 mg, 3000 mg and 4500 mg) of betaine hydrochloride (BHCl) to determine the ability of acid supplementation to reacidify gastric pH after the elevation of gastric pH caused by the ingestion of food. RESULTS:Following the administration of food and the resulting elevation in gastric pH, time to return to baseline gastric pH levels without acid supplementation was 49.7 ± 14.0 min. Administering 4500 mg of BHCl acid in capsules was able to reacidify gastric pH levels back to baseline following the administration of food in approximately 17.3 ± 5.9 min. AUCpH of each treatment were similar and not statistically different. Mean max pH following the administration of food was 3.20 ± 0.55. CONCLUSION:The ability of food to elevate and maintain gastric pH levels in the presence of acid supplementation was made evident throughout the study. A 4500 mg dose of BHCl was required to reacidify gastric pH after the administration of food. This study details the difficulty faced by clinicians in dosing a poorly soluble, weakly basic drug to patients receiving acid reducing agents where administration with food is recommended to avoid gastric side effects. TRIAL REGISTRATION:https://clinicaltrials.gov/ct2/show/NCT02758015
Alteración de las biotitas y biotitas clorizadas de la granodiorita de Collserola (Barcelona)
[ES] Se estudia la alteración natural experimentada por las biotitas y
biotitas cloritizadas de la granodiorita de la Serra de Collcerola (Barcelona),
bajo clima mediterráneo. Se muestrearon nueve perfiles, separándose
magnéticamente las biotitas de la fracción arena, analizándose
quÃmicamente (elementos totales), por difractometrÃa de R.X.
y microscopia electrónica de barrido. También se estudiaron con el
microscopio petrográfico láminas delgadas de muestras no
perturbadas.
Las biotitas evolucionan progresivamente primero a interestratificados
biotita-vermiculita y después a vermiculita, apreciándose una
tendencia a la esmectización, sugiriendo que las condiciones medioambitentales
en las que se ha producido la alteración son muy similares
a las actuales. La fase clorita procedente de las biotitas cloritizadas
permanece inalterada en dicho medio.[EN] The weathering of biotites and cloritized biotites from a granodiorite
from Serra de Collcerola (Barcelona, Spain), under mediterranean
climate, has been studied. The sand fraction from the horizons
of nine pedological profiles were sampled and the biotites magnetically
separated and analysed by XRD, SEM and chemically. Thin
sections of undisturbed samples were also studied.
The weathering sequence from non-cloritized biotites was Biotite - Interlayer B-V - Vermiculite with a trend towards smectitization.
The chlorite mineral from chloritized biotites remains unchanged
in this environment. These results suggest tliat the weathering
environment has been quite similar to the present one.Peer reviewe
Nearest-Neighbor Distributions and Tunneling Splittings in Interacting Many-Body Two-Level Boson Systems
We study the nearest-neighbor distributions of the -body embedded
ensembles of random matrices for bosons distributed over two-degenerate
single-particle states. This ensemble, as a function of , displays a
transition from harmonic oscillator behavior () to random matrix type
behavior (). We show that a large and robust quasi-degeneracy is present
for a wide interval of values of when the ensemble is time-reversal
invariant. These quasi-degenerate levels are Shnirelman doublets which appear
due to the integrability and time-reversal invariance of the underlying
classical systems. We present results related to the frequency in the spectrum
of these degenerate levels in terms of , and discuss the statistical
properties of the splittings of these doublets.Comment: 13 pages (double column), 7 figures some in color. The movies can be
obtained at http://link.aps.org/supplemental/10.1103/PhysRevE.81.03621
Disjoining Pressure and the Film-Height-Dependent Surface Tension of Thin Liquid Films: New Insight from Capillary Wave Fluctuations
In this paper we review simulation and experimental studies of thermal
capillary wave fluctuations as an ideal means for probing the underlying
disjoining pressure and surface tensions, and more generally, fine details of
the Interfacial Hamiltonian Model. We discuss recent simulation results that
reveal a film-height-dependent surface tension not accounted for in the
classical Interfacial Hamiltonian Model. We show how this observation may be
explained bottom-up from sound principles of statistical thermodynamics and
discuss some of its implications.Comment: File is accepted version with 70 pages and 13 figures. Submitted
23/08/2013; Accepted 06/11/2013; Online 17/11/201
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