3,494 research outputs found
One-Nucleon Effective Generators of the Poincare Group derived from a Field Theory: Mass Renormalization
We start from a Lagrangian describing scalar "nucleons" and mesons which
interact through a simple vertex. Okubo's method of unitary transformation is
used to describe a single nucleon dressed by its meson cloud. We find an
expression for the physical mass of the nucleon being correct up to second
order in the coupling constant. It is then verified that this result is the
same as the corresponding expression found by Feynman techniques. Finally we
also express the three boost operators in terms of the physical nucleon mass.
Doing so we find expressions for all the ten generators of Poincar\'e
transformations for the system of one single dressed nucleon.Comment: 19 pages, no figure
Scattering of neutrinos on a polarized electron target as a test for new physics beyond the Standard Model
In this paper, we analyze the scattering of the neutrino beam on the
polarized electron target, and predict the effects of two theoretically
possible scenarios beyond the Standard Model. In both scenarios, Dirac
neutrinos are assumed to be massive.
First, we consider how the existence of CP violation phase between the
complex vector V and axial A couplings of the Left-handed neutrinos affects the
azimuthal dependence of the differential cross section. The future superbeam
and neutrino factory experiments will provide the unique opportunity for the
leptonic CP violation studies, if the large magnetized sampling calorimeters
with good event reconstruction capabilities are build.
Next, we take into account a scenario with the participation of the exotic
scalar S coupling of the Right-handed neutrinos in addition to the standard
vector V and axial A couplings of the Left-handed neutrinos. The main goal is
to show how the presence of the R-handed neutrinos, in the above process
changes the spectrum of recoil electrons in relation to the expected Standard
Model prediction, using the current limits on the non-standard couplings. The
interference terms between the standard and exotic couplings in the
differential cross section depend on the angle between the transverse
incoming neutrino polarization and the transverse electron polarization of the
target, and do not vanish in the limit of massless neutrino. The detection of
the dependence on this angle in the energy spectrum of recoil electrons would
be a signature of the presence of the R-handed neutrinos in the
neutrino-electron scattering. To make this test feasible, the polarized
artificial neutrino source needs to be identified.Comment: 11 pages, 3 eps figures, revtex, submitted to publicatio
Access control for social care platforms using fast healthcare interoperability resources
The definition of authorization policies is essential to prevent information misuse and to guarantee that only authorized personnel can access specific information. Since not everyone is familiar with special purpose languages, an interpretation tool can allow the management of policies and rules using natural languages. This paper focuses on a parser developed as a component of a platform to support the care of community-dwelling older adults, the SOCIAL platform, allowing to create, read, update and delete authorization policies and rules, using natural languages.publishe
Local Electronic Correlation at the Two-Particle Level
Electronic correlated systems are often well described by dynamical mean
field theory (DMFT). While DMFT studies have mainly focused hitherto on
one-particle properties, valuable information is also enclosed into local
two-particle Green's functions and vertices. They represent the main ingredient
to compute momentum-dependent response functions at the DMFT level and to treat
non-local spatial correlations at all length scales by means of diagrammatic
extensions of DMFT. The aim of this paper is to present a DMFT analysis of the
local reducible and irreducible two-particle vertex functions for the Hubbard
model in the context of an unified diagrammatic formalism. An interpretation of
the observed frequency structures is also given in terms of perturbation
theory, of the comparison with the atomic limit, and of the mapping onto the
attractive Hubbard model.Comment: 29 pages, 26 Figures. Accepted for publication in Phys. Rev.
Aktuelle theoretische AnsÀtze und empirische Befunde im Bereich der Lehr-Lern-Forschung:Schwerpunkt Erwachsenenbildung
Das Gutachten dient dem im Jahr 2004 vom DIE ins Leben gerufenen âExpertenkreis Lehre in der Weiterbildungâ als Arbeitsgrundlage. Es stellt die aktuellen AnsĂ€tze und Befunde im Bereich des Lehrens und Lernens mit Schwerpunkt auf der Erwachsenenbildung dar. Neuere AnsĂ€tze zum Lehren und Lernen aus der Empirischen PĂ€dagogik und PĂ€dagogischen Psychologie werden vorgestellt und auf spezifische Aspekte der Weiterbildung wie Communities, berufliche Weiterbildung und Blended Learning eingegangen. Die verschiedenen Ebenen, Aufgabenfelder und Phasen des Bildungsmanagements werden beleuchtet und das Bildungscontrolling nĂ€her erlĂ€utert. Danach folgen AusfĂŒhrungen zu einem mitarbeiterorientierten Implementationsmodell innovativer Lehr-Lern-AnsĂ€tze in Organisationen. Anhand der vorgestellten AnsĂ€tze und Befunde des Lehrens und Lernens werden Folgerungen fĂŒr die Forschung und fĂŒr die Ausund Weiterbildung der Lehrenden im Bereich der Erwachsenenbildung gezogen
Thermodynamics of a model for RNA folding
We analyze the thermodynamic properties of a simplified model for folded RNA
molecules recently studied by G. Vernizzi, H. Orland, A. Zee (in {\it Phys.
Rev. Lett.} {\bf 94} (2005) 168103). The model consists of a chain of
one-flavor base molecules with a flexible backbone and all possible pairing
interactions equally allowed. The spatial pseudoknot structure of the model can
be efficiently studied by introducing a hermitian random matrix
model at each chain site, and associating Feynman diagrams of these models to
spatial configurations of the molecules. We obtain an exact expression for the
topological expansion of the partition function of the system. We calculate
exact and asymptotic expressions for the free energy, specific heat,
entanglement and chemical potential and study their behavior as a function of
temperature. Our results are consistent with the interpretation of as
being a measure of the concentration of in solution.Comment: 11 pages, 4 figure
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An unsupervised classification method for inferring original case locations from low-resolution disease maps
BACKGROUND: Widespread availability of geographic information systems software has facilitated the use of disease mapping in academia, government and private sector. Maps that display the address of affected patients are often exchanged in public forums, and published in peer-reviewed journal articles. As previously reported, a search of figure legends in five major medical journals found 19 articles from 1994â2004 that identify over 19,000 patient addresses. In this report, a method is presented to evaluate whether patient privacy is being breached in the publication of low-resolution disease maps. RESULTS: To demonstrate the effect, a hypothetical low-resolution map of geocoded patient addresses was created and the accuracy with which patient addresses can be resolved is described. Through georeferencing and unsupervised classification of the original image, the method precisely re-identified 26% (144/550) of the patient addresses from a presentation quality map and 79% (432/550) from a publication quality map. For the presentation quality map, 99.8% of the addresses were within 70 meters (approximately one city block length) of the predicted patient location, 51.6% of addresses were identified within five buildings, 70.7% within ten buildings and 93% within twenty buildings. For the publication quality map, all addresses were within 14 meters and 11 buildings of the predicted patient location. CONCLUSION: This study demonstrates that lowering the resolution of a map displaying geocoded patient addresses does not sufficiently protect patient addresses from re-identification. Guidelines to protect patient privacy, including those of medical journals, should reflect policies that ensure privacy protection when spatial data are displayed or published
Langevin Trajectories between Fixed Concentrations
We consider the trajectories of particles diffusing between two infinite
baths of fixed concentrations connected by a channel, e.g. a protein channel of
a biological membrane. The steady state influx and efflux of Langevin
trajectories at the boundaries of a finite volume containing the channel and
parts of the two baths is replicated by termination of outgoing trajectories
and injection according to a residual phase space density. We present a
simulation scheme that maintains averaged fixed concentrations without creating
spurious boundary layers, consistent with the assumed physics
Non-Markovian dynamics of a nanomechanical resonator measured by a quantum point contact
We study the dynamics of a nanomechanical resonator (NMR) subject to a
measurement by a low transparency quantum point contact (QPC) or tunnel
junction in the non-Markovian domain. We derive the non-Markovian
number-resolved (conditional) and unconditional master equations valid to
second order in the tunneling Hamiltonian without making the rotating-wave
approximation and the Markovian approximation, generally made for systems in
quantum optics. Our non-Markovian master equation reduces, in appropriate
limits, to various Markovian versions of master equations in the literature. We
find considerable difference in dynamics between the non-Markovian cases and
its Markovian counterparts. We also calculate the time-dependent transport
current through the QPC which contains information about the measured NMR
system. We find an extra transient current term proportional to the expectation
value of the symmetrized product of the position and momentum operators of the
NMR. This extra current term, with a coefficient coming from the combination of
the imaginary parts of the QPC reservoir correlation functions, has a
substantial contribution to the total transient current in the non-Markovian
case, but was generally ignored in the studies of the same problem in the
literature. Considering the contribution of this extra term, we show that a
significantly qualitative and quantitative difference in the total transient
current between the non-Markovian and the Markovian wide-band-limit cases can
be observed. Thus, it may serve as a witness or signature of the non-Markovian
features in the coupled NMR-QPC system.Comment: Accepted for publication in Physical Review B (20 pages, 13 figures
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