2,590 research outputs found
Neutron star structure and collective excitations of finite nuclei
We study relationships between properties of collective excitations in finite
nuclei and the phase transition density and pressure at the inner
edge separating the liquid core and the solid crust of a neutron star. A
theoretical framework that includes the thermodynamic method, relativistic
nuclear energy density functionals and the quasiparticle random-phase
approximation is employed in a self-consistent calculation of and
collective excitations in nuclei. The covariance analysis shows that properties
of charge-exchange dipole transitions, isovector giant dipole and quadrupole
resonances and pygmy dipole transitions are correlated with the core-crust
transition density and pressure. A set of relativistic nuclear energy density
functionals, characterized by systematic variation of the density dependence of
the symmetry energy of nuclear matter, is used to constrain possible values for
. By comparing the calculated excitation energies of giant
resonances, energy weighted pygmy dipole strength, and dipole polarizability
with available data, we obtain the weighted average values: fm and MeV fm.Comment: 4 pages, 3 figures, paper submitted for publicatio
Neutrino and antineutrino cross sections in C
We extend the formalism of weak interaction processes, obtaining new
expressions for the transition rates, which greatly facilitate numerical
calculations, both for neutrino-nucleus reactions and muon capture. We have
done a thorough study of exclusive (ground state) properties of B and
N within the projected quasiparticle random phase approximation (PQRPA).
Good agreement with experimental data is achieved in this way. The inclusive
neutrino/antineutrino () reactions C(N
and C(B are calculated within both the PQRPA, and
the relativistic QRPA (RQRPA). It is found that the magnitudes of the resulting
cross-sections: i) are close to the sum-rule limit at low energy, but
significantly smaller than this limit at high energies both for and
, ii) they steadily increase when the size of the configuration
space is augmented, and particulary for energies MeV,
and iii) converge for sufficiently large configuration space and final state
spin.Comment: Proceedings of the International Nuclear Physics Conference 2010,
Vancouver, BC - Canada 4-9 Jul 201
Bursts in the Chaotic Trajectory Lifetimes Preceding the Controlled Periodic Motion
The average lifetime () it takes for a randomly started trajectory
to land in a small region () on a chaotic attractor is studied. is
an important issue for controlling chaos. We point out that if the region
is visited by a short periodic orbit, the lifetime strongly deviates
from the inverse of the naturally invariant measure contained within that
region (). We introduce the formula that relates
to the expanding eigenvalue of the short periodic orbit
visiting .Comment: Accepted for publication in Phys. Rev. E, 3 PS figure
Semantic Transformation of Web Services
Web services have become the predominant paradigm for the development of distributed software systems. Web services provide the means to modularize software in a way that functionality can be described, discovered and deployed in a platform independent manner over a network (e.g., intranets, extranets and the Internet). The representation of web services by current industrial practice is predominantly syntactic in nature lacking the fundamental semantic underpinnings required to fulfill the goals of the emerging Semantic Web. This paper proposes a framework aimed at (1) modeling the semantics of syntactically defined web services through a process of interpretation, (2) scop-ing the derived concepts within domain ontologies, and (3) harmonizing the semantic web services with the domain ontologies. The framework was vali-dated through its application to web services developed for a large financial system. The worked example presented in this paper is extracted from the se-mantic modeling of these financial web services
Deformed Gaussian Orthogonal Ensemble Analysis of the Interacting Boson Model
A Deformed Gaussian Orthogonal Ensemble (DGOE) which interpolates between the
Gaussian Orthogonal Ensemble and a Poissonian Ensemble is constructed. This new
ensemble is then applied to the analysis of the chaotic properties of the low
lying collective states of nuclei described by the Interacting Boson Model
(IBM). This model undergoes a transition order-chaos-order from the
limit to the limit. Our analysis shows that the quantum fluctuations of
the IBM Hamiltonian, both of the spectrum and the eigenvectors, follow the
expected behaviour predicted by the DGOE when one goes from one limit to the
other.Comment: 10 pages, 4 figures (avaiable upon request), IFUSP/P-1086 Replaced
version: in the previous version the name of one of the authors was omitte
Neutrino and antineutrino cross sections in 12C
We extend our formalism of weak interaction processes, obtaining new expressions for the transition rates, which greatly facilitate numerical calculations, of neutrino (ν) and antineutrino (ν)-nucleus reactions and the muon capture. We have done a thorough study of exclusive (ground state) properties of 12B and 12N within the Projected Quasiparticle Random Phase Approximation (PQRPA). Good agreement with experimental data is achieved in this way. The inclusive ν/ν-nucleus reactions 12C(ν, e-)12N and 12C(ν, e+)12B are calculated within both the PQRPA, and the Relativistic QRPA (RQRPA). It is found that the magnitudes of the resulting cross-sections: i) are close to the sum-rule limit at low energy, but significantly smaller than this limit at high energies both for ν and ν, ii) steadily increase when the size of the configuration space is augmented, and particulary for ν/ν energies > 200 MeV, and iii) converge for sufficiently large configuration spaces and final state angular momenta.Facultad de Ciencias Exacta
Neutrino and antineutrino charge-exchange reactions on 12C
We extend the formalism of weak interaction processes, obtaining new
expressions for the transition rates, which greatly facilitate numerical
calculations, both for neutrino-nucleus reactions and muon capture. Explicit
violation of CVC hypothesis by the Coulomb field, as well as development of a
sum rule approach for the inclusive cross sections have been worked out. We
have done a thorough study of exclusive (ground state) properties of B
and N within the projected quasiparticle random phase approximation
(PQRPA). Good agreement with experimental data achieved in this way put in
evidence the limitations of standard RPA and the QRPA models, which come from
the inability of the RPA in opening the shell, and from the
non-conservation of the number of particles in the QRPA. The inclusive
neutrino/antineutrino () reactions C(N
and C(B are calculated within both the PQRPA, and
the relativistic QRPA (RQRPA). It is found that the magnitudes of the resulting
cross-sections: i) are close to the sum-rule limit at low energy, but
significantly smaller than this limit at high energies both for and
, ii) they steadily increase when the size of the configuration
space is augmented, and particulary for energies MeV,
and iii) converge for sufficiently large configuration space and final state
spin. The quasi-elastic C(N cross section recently
measured in the MiniBooNE experiment is briefly discussed. We study the
decomposition of the inclusive cross-section based on the degree of
forbiddenness of different multipoles. A few words are dedicated to the
-C charge-exchange reactions related with astrophysical
applications.Comment: 21 pages, 13 figures, 1 table, submitted to Physical Review
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