697 research outputs found
Radiative processes as a condensation phenomenon and the physical meaning of deformed canonical structures
Working with well known models in we discuss the physics behind the
deformation of the canonical structure of these theories. A new deformation is
constructed linking the massless scalar field theory with the self-dual theory.
This is the exact dual of the known deformation connecting the Maxwell theory
with the Maxwell-Chern-Simons theory. Duality is used to establish a web of
relations between the mentioned theories and a physical picture of the
deformation procedure is suggested.Comment: revtex4 file, 16 page
Role of rare earth elements and entropy on the anatase-to-rutile phase transformation of TiO2thin films deposited by ion beam sputtering
The role played by oxygen vacancies and rare earth (RE) elements in the anatase-to-rutile (A−R) phase transformation of titanium dioxide (TiO2) is still a matter of controversy. Here, we report the A−R transformation of TiO2 thin solid films as obtained by ion beam sputtering a RE-decorated titanium target in an oxygen-rich atmosphere. The samples correspond to undoped, single-doped (Sm, Tm, and Tb), and codoped (Sm:Tb, Sm:Tm, and Sm:Tb:Tm) TiO2 films. In the as-prepared form, the films are amorphous and contain ∼0.5 at. % of each RE. The structural modifications of the TiO2 films due to the RE elements and the annealing treatments in an oxygen atmosphere are described according to the experimental results provided by Raman scattering, X-ray photoelectron spectroscopy, and optical measurements. The A−R transformation depends on both the annealing temperature and the characteristics of the undoped, single-doped, and codoped TiO2 films. As reported in the literature, the A−R transformation can be inhibited or enhanced by the presence of impurities and is mostly related to energetic contributions. The experimental results were analyzed, considering the essential and stabilizing role of the entropy of mixing in the A−R transformation due to the introduction of more and multiple quantum states originated in vacancies and impurities in the anatase phase.Fil: Scoca, Diego L.S.. Universidade Estadual de Campinas; BrasilFil: Cemin, Felipe. Universidade Estadual de Campinas; BrasilFil: Aldabe, Sara Alfonsina. Universidad de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; ArgentinaFil: Figueroa, Carlos A.. Universidade de Caxias Do Sul.; BrasilFil: Zanatta, Antonio R.. Universidade de Sao Paulo; BrasilFil: Alvarez, Fernando. Universidade Estadual de Campinas; Brasi
Magnetic moments of the low-lying , resonances within the framework of the chiral quark model
The magnetic moments of the low-lying spin-parity ,
resonances, like, for example, ,
, as well as their transition magnetic moments, are
calculated using the chiral quark model. The results found are compared with
those obtained from the nonrelativistic quark model and those of unitary chiral
theories, where some of these states are generated through the dynamics of two
hadron coupled channels and their unitarization
Properties of hyperons in chiral perturbation theory
The development of chiral perturbation theory in hyperon phenomenology has
been troubled due to power-counting subtleties and to a possible slow
convergence. Furthermore, the presence of baryon-resonances, e.g. the
lowest-lying decuplet, complicates the approach, and the inclusion of their
effects may become necessary. Recently, we have shown that a fairly good
convergence is possible using a renormalization prescription of the
loop-divergencies which recovers the power counting, is covariant and
consistent with analyticity. Moreover, we have systematically incorporated the
decuplet resonances taking care of both power-counting and
problems. A model-independent understanding of diferent properties including
the magnetic moments of the baryon-octet, the electromagnetic structure of the
decuplet resonances and the hyperon vector coupling , has been
successfully achieved within this approach. We will briefly review these
developments and stress the important role they play for an accurate
determination of the Cabibbo-Kobayashi-Maskawa matrix element from
hyperon semileptonic decay data.Comment: To appear in HypX Proceeding
Cryptanalysis of an image encryption scheme based on the Hill cipher
This paper studies the security of an image encryption scheme based on the
Hill cipher and reports its following problems: 1) there is a simple necessary
and sufficient condition that makes a number of secret keys invalid; 2) it is
insensitive to the change of the secret key; 3) it is insensitive to the change
of the plain-image; 4) it can be broken with only one known/chosen-plaintext;
5) it has some other minor defects.Comment: 10 pages, three figure
On Necessary and Sufficient Conditions for Near-Optimal Singular Stochastic Controls
This paper is concerned with necessary and sufficient conditions for
near-optimal singular stochastic controls for systems driven by a nonlinear
stochastic differential equations (SDEs in short). The proof of our result is
based on Ekeland's variational principle and some delicate estimates of the
state and adjoint processes. This result is a generalization of Zhou's
stochastic maximum principle for near-optimality to singular control problem.Comment: 19 pages, submitted to journa
Testing spatial noncommutativiy via the Aharonov-Bohm effect
The possibility of detecting noncommutative space relics is analyzed using
the Aharonov-Bohm effect. We show that, if space is noncommutative, the
holonomy receives non-trivial kinematical corrections that will produce a
diffraction pattern even when the magnetic flux is quantized. The scattering
problem is also formulated, and the differential cross section is calculated.
Our results can be extrapolated to high energy physics and the bound is found. If this bound holds, then noncommutative
effects could be explored in scattering experiments measuring differential
cross sections for small angles. The bound state Aharonov- Bohm effect is also
discussed.Comment: 16 pp, Revtex 4, 2 fig, new references added. To appear in PR
Associations of Comorbid Conditions and Transitions Across States of Knee Osteoarthritis in a Community-Based Cohort
Objective: To examine relationships between knee osteoarthritis (KOA) and obesity, diabetes mellitus (DM), and cardiovascular disease (CVD). Methods: Associations of time-dependent obesity, DM, and CVD with KOA transition states over approximately 18 years were examined among 4093 participants from a community-based cohort. Transition states were 1) no knee symptoms and no radiographic KOA (rKOA; Kellgren-Lawrence grade ≥2 in at least one knee), 2) asymptomatic rKOA, 3) knee symptoms only, 4) symptomatic rKOA (sxKOA; rKOA and symptoms in same knee). Markov multistate models estimated adjusted hazard ratios (aHRs) and 95% confidence intervals (CIs) for associations between comorbid conditions and transitions across states, adjusting for baseline age, sex, race, education, enrollment cohort, birth year, and time-dependent knee injury history. Results: At baseline, 40% of participants had obesity, 13% had DM, and 22% had CVD (mean age = 61 years; 34% Black; 37% male). Compared with those without obesity, those with obesity had a higher hazard of worsening from no rKOA/no symptoms to asymptomatic rKOA (aHR = 1.7; 95% CI = 1.3-2.2) and from knee symptoms to sxKOA (aHR = 1.7; 95% CI = 1.3-2.3), as well as a lower hazard of symptom resolution from sxKOA to asymptomatic rKOA (aHR = 0.5 [95% = CI 0.4-0.7]). Compared with those without CVD, those with CVD had a higher hazard of worsening from no rKOA/symptoms to knee symptoms (aHR = 1.5; 95% CI = 1.1-2.1). DM was not associated with transitions of rKOA. Conclusion: Prevention of obesity and CVD may limit the development or worsening of rKOA and symptoms
Towards the high-accuracy determination of the 238U fission cross section at the threshold region at CERN - N-TOF
The 238U fission cross section is an international standard beyond 2 MeV where the fission plateau starts. However, due to its importance in fission reactors, this cross-section should be very accurately known also in the threshold region below 2 MeV. The 238U fission cross section has been measured relative to the 235U fission cross section at CERN - n-TOF with different detection systems. These datasets have been collected and suitably combined to increase the counting statistics in the threshold region from about 300 keV up to 3 MeV. The results are compared with other experimental data, evaluated libraries, and the IAEA standards
A Measurement of Coherent Neutral Pion Production in Neutrino Neutral Current Interactions in NOMAD
We present a study of exclusive neutral pion production in neutrino-nucleus
Neutral Current interactions using data from the NOMAD experiment at the CERN
SPS. The data correspond to muon-neutrino Charged Current
interactions in the energy range GeV. Neutrino
events with only one visible in the final state are expected to result
from two Neutral Current processes: coherent production, {\boldmath
} and single production in
neutrino-nucleon scattering. The signature of coherent production is an
emergent almost collinear with the incident neutrino while 's
produced in neutrino-nucleon deep inelastic scattering have larger transverse
momenta. In this analysis all relevant backgrounds to the coherent
production signal are measured using data themselves. Having determined the
backgrounds, and using the Rein-Sehgal model for the coherent
production to compute the detection efficiency, we obtain {\boldmath } corrected coherent- events with GeV. We measure {\boldmath }.
This is the most precise measurement of the coherent production to
date.Comment: 23 pages, 9 figures, accepted for publication in Phys. Lett.
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