254 research outputs found
Measuring the fluctuation-dissipation ratio in glassy systems with no perturbing field
A method is presented for measuring the integrated response in Ising spin
system without applying any perturbing field. Large-scale simulations are
performed in order to show how the method works. Very precise measurements of
the fluctuation-dissipation ratio are presented for 3 different Ising models:
the 2-dimensional ferromagnetic model, the mean-field diluted 3-spin model, and
the 3-dimensional Edwards-Anderson model.Comment: 4 pages, 4 figure
Ultrametricity in 3D Edwards-Anderson spin glasses
We perform an accurate test of Ultrametricity in the aging dynamics of the
three dimensional Edwards-Anderson spin glass. Our method consists in
considering the evolution in parallel of two identical systems constrained to
have fixed overlap. This turns out to be a particularly efficient way to study
the geometrical relations between configurations at distant large times. Our
findings strongly hint towards dynamical ultrametricity in spin glasses, while
this is absent in simpler aging systems with domain growth dynamics. A recently
developed theory of linear response in glassy systems allows to infer that
dynamical ultrametricity implies the same property at the level of equilibrium
states.Comment: 4 pages, 5 figure
Quantum theta functions and Gabor frames for modulation spaces
Representations of the celebrated Heisenberg commutation relations in quantum
mechanics and their exponentiated versions form the starting point for a number
of basic constructions, both in mathematics and mathematical physics (geometric
quantization, quantum tori, classical and quantum theta functions) and signal
analysis (Gabor analysis).
In this paper we try to bridge the two communities, represented by the two
co--authors: that of noncommutative geometry and that of signal analysis. After
providing a brief comparative dictionary of the two languages, we will show
e.g. that the Janssen representation of Gabor frames with generalized Gaussians
as Gabor atoms yields in a natural way quantum theta functions, and that the
Rieffel scalar product and associativity relations underlie both the functional
equations for quantum thetas and the Fundamental Identity of Gabor analysis.Comment: 38 pages, typos corrected, MSC class change
About the Functional Form of the Parisi Overlap Distribution for the Three-Dimensional Edwards-Anderson Ising Spin Glass
Recently, it has been conjectured that the statistics of extremes is of
relevance for a large class of correlated system. For certain probability
densities this predicts the characteristic large fall-off behavior
, . Using a multicanonical Monte Carlo technique,
we have calculated the Parisi overlap distribution for the
three-dimensional Edward-Anderson Ising spin glass at and below the critical
temperature, even where is exponentially small. We find that a
probability distribution related to extreme order statistics gives an excellent
description of over about 80 orders of magnitude.Comment: 4 pages RevTex, 3 figure
Off-equilibrium fluctuation-dissipation relations in the 3d Ising Spin Glass in a magnetic field
We study the fluctuation-dissipation relations for a three dimensional Ising
spin glass in a magnetic field both in the high temperature phase as well as in
the low temperature one. In the region of times simulated we have found that
our results support a picture of the low temperature phase with broken replica
symmetry, but a droplet behavior can not be completely excluded.Comment: 9 pages, 11 ps figures, revtex. Final version to be published in
Phys. Rev.
Ability of the Schatzker classification to predict posteromedial fragmentation in tibial plateau fractures
BACKGROUND : The Schatzker classification is the most widely accepted system used to classify tibial plateau fractures. The presence of
posteromedial fragments in the more severe fracture types is known, but the presence of posteromedial fragmentation in the less severe
fracture types is unknown. The ability of the Schatzker classification to predict posteromedial fragmentation was evaluated.
METHODS : Two hundred patients were reviewed of which only 67 met the inclusion criteria. The X-rays were reviewed by three independent
orthopaedic surgeons and classified according to the Schatzker classification. A radiologist reviewed the CT scans and noted the presence
or absence of a posteromedial fragment and if present, the largest diameter of the fragment was measured.
RESULTS : The mean age of the sample was 44.79 (SD: 14.03) years. Seventy-five per cent of the females (n=33) presented with
posteromedial fragmentation compared to 65.20% of the males (n=44) (chi²-test, P=0.399). The incidence of posteromedial fragmentation
varied between 15.8 and 26.3% for Schatzker 1 and 2 fractures and 73.7 and 84.2% for Schatzker 3 to 6 (chi2-test, p<0.001) based on
the three independent assessments. The mean length of the posteromedial fragmentation ranged from 41.87 to 47.77 mm for Schatzker
1 and 2 fractures, and 44.74 to 46.12 mm for Schatzker 3 to 6 for the three assessors (statistically not significant [T-test, P=0.536,
P=0.551 and P=0.652]).
CONCLUSION : The Schatzker classification by itself is not adequate to identify all fractures with posteromedial fragmentation. There is a
higher association of posteromedial fragmentation with fracture types 3 to 6. There is a high probability of missing a significantly sized
posteromedial fragment in Schatzker type 1 and 2 fractures if a CT scan is not performed which might influence and compromise fracture
stability, joint congruency and the ability to rehabilitate optimally.http://journal.saoa.org.zaam2019Orthopaedic SurgeryRadiolog
Extended droplet theory for aging in short-ranged spin glasses and a numerical examination
We analyze isothermal aging of a four dimensional Edwards-Anderson model in
detail by Monte Carlo simulations. We analyze the data in the view of an
extended version of the droplet theory proposed recently (cond-mat/0202110)
which is based on the original droplet theory plus conjectures on the
anomalously soft droplets in the presence of domain walls. We found that the
scaling laws including some fundamental predictions of the original droplet
theory explain well our results. The results of our simulation strongly suggest
the separation of the breaking of the time translational invariance and the
fluctuation dissipation theorem in agreement with our scenario.Comment: 27 pages, 39 epsfiles, revised versio
Chaotic, memory and cooling rate effects in spin glasses: Is the Edwards-Anderson model a good spin glass?
We investigate chaotic, memory and cooling rate effects in the three
dimensional Edwards-Anderson model by doing thermoremanent (TRM) and AC
susceptibility numerical experiments and making a detailed comparison with
laboratory experiments on spin glasses. In contrast to the experiments, the
Edwards-Anderson model does not show any trace of re-initialization processes
in temperature change experiments (TRM or AC). A detailed comparison with AC
relaxation experiments in the presence of DC magnetic field or coupling
distribution perturbations reveals that the absence of chaotic effects in the
Edwards-Anderson model is a consequence of the presence of strong cooling rate
effects. We discuss possible solutions to this discrepancy, in particular the
smallness of the time scales reached in numerical experiments, but we also
question the validity of the Edwards-Anderson model to reproduce the
experimental results.Comment: 17 pages, 10 figures. The original version of the paper has been
split in two parts. The second part is now available as cond-mat/010224
Breakup Reactions of 11Li within a Three-Body Model
We use a three-body model to investigate breakup reactions of 11Li (n+n+9Li)
on a light target. The interaction parameters are constrained by known
properties of the two-body subsystems, the 11Li binding energy and
fragmentation data. The remaining degrees of freedom are discussed. The
projectile-target interactions are described by phenomenological optical
potentials. The model predicts dependence on beam energy and target,
differences between longitudinal and transverse momentum distributions and
provides absolute values for all computed differential cross sections. We give
an almost complete series of observables and compare with corresponding
measurements. Remarkably good agreement is obtained. The relative neutron-9Li
p-wave content is about 40%. A p-resonance, consistent with measurements at
about 0.5 MeV of width about 0.4 MeV, seems to be necessary. The widths of the
momentum distributions are insensitive to target and beam energy with a
tendency to increase towards lower energies. The transverse momentum
distributions are broader than the longitudinal due to the diffraction process.
The absolute values of the cross sections follow the neutron-target cross
sections and increase strongly for beam energies decreasing below 100 MeV/u.Comment: 19 pages, 14 figures, RevTeX, psfig.st
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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