30,810 research outputs found
Determining distributions of weakly bound nuclei from breakup cross sections using Continuum Discretized Coupled Channels calculations. Application to Be
A novel method to extract the strength of a weakly bound nucleus from
experimental Coulomb dissociation data is proposed. The method makes use of
continuum discretized coupled channels (CDCC) calculations, in which both
nuclear and Coulomb forces are taken into account to all orders. This is a
crucial advantage with respect to the standard procedure based on the
Equivalent Photon Method (EPM) which does not properly take into account
nuclear distortion, higher order coupling effects, or Coulomb-nuclear
interference terms. The procedure is applied to the Be nucleus using two
sets of available experimental data at different energies, for which seemingly
incompatible have been reported using the EPM. We show that the present
procedure gives consistent strengths, thus solving the aforementioned
long-standing discrepancy between the two measurements.Comment: Submitted for publicatio
The electro production of d* dibaryon
dibaryon study is a critical test of hadron interaction models. The
electro production cross sections of have been calculated based on
the meson exchange current model and the cross section around 30 degree of 1
GeV electron in the laboratory frame is about 10 nb. The implication of this
result for the dibaryon search has been discussed.Comment: 12 pages, 12 figures, Late
Dark-matter dynamical friction versus gravitational-wave emission in the evolution of compact-star binaries
The measured orbital period decay of compact-star binaries, with
characteristic orbital periods ~days, is explained with very high
precision by the gravitational wave (GW) emission of an inspiraling binary in
vacuum. However, the binary gravitational binding energy is also affected by an
usually neglected phenomenon, namely the dark matter dynamical friction (DMDF)
produced by the interaction of the binary components with their respective DM
gravitational wakes. The entity of this effect depends on the orbital period
and on the local value of the DM density, hence on the position of the binary
in the Galaxy. We evaluate the DMDF produced by three different DM profiles:
the Navarro-Frenk-White (NFW), the non-singular-isothermal-sphere (NSIS) and
the Ruffini-Arg\"uelles-Rueda (RAR) profile based on self-gravitating keV
fermions. We first show that indeed, due to their Galactic position, the GW
emission dominates over the DMDF in the NS-NS, NS-WD and WD-WD binaries for
which measurements of the orbital decay exist. Then, we evaluate the conditions
under which the effect of DMDF on the binary evolution becomes comparable to,
or overcomes, the one of the GW emission. We find that, for instance for
-- NS-WD, --~ NS-NS, and
--~ WD-WD, located at 0.1~kpc, this occurs at orbital
periods around 20--30 days in a NFW profile while, in a RAR profile, it occurs
at about 100 days. For closer distances to the Galactic center, the DMDF effect
increases and the above critical orbital periods become interestingly shorter.
Finally, we also analyze the system parameters for which DMDF leads to an
orbital widening instead of orbital decay. All the above imply that a
direct/indirect observational verification of this effect in compact-star
binaries might put strong constraints on the nature of DM and its Galactic
distribution.Comment: 15 pages, 12 figures, 2 tables, accepted for publication in Phys.
Rev. D, 201
Towards an Ontology Metadata Standard
In this poster, we present (i) a proposal for a metadata standard, known as Ontology Metadata Vocabulary (OMV) which is based on discussions in the EU IST thematic network of excellence Knowledge Web1 and (ii) two complementary reference
implementations which show the benefit of such a standard in
decentralized and centralized scenarios, i.e. the Oyster P2P
system and the Onthology metadata portal
Science with the World Space Observatory - Ultraviolet
The World Space Observatory-Ultraviolet (WSO-UV) will provide access to the
UV range during the next decade. The instrumentation on board will allow to
carry out high resolution imaging, high sensitivity imaging, high resolution
(R~55000) spectroscopy and low resolution (R~2500) long slit spectroscopy. In
this contribution, we briefly outline some of the key science issues that
WSO-UV will address during its lifetime. Among them, of special interest are:
the study of galaxy formation and the intergalactic medium; the astronomical
engines; the Milky Way formation and evol ution, and the formation of the Solar
System and the atmospheres of extrasolar p lanets.Comment: Just one text file (aigomezdecastro.tex). To be published in the
proceeding of the conference: "New Quest in Stellar Astrophysics II: UV
properties of evolved stellar populations" held in Puerto Vallarta - Mexico,
in april 200
Reusing Human Resources Management Standards for Employment Services
Employment Services (ESs) are becoming more and more important for Public Administrations where their social implications on sustainability, workforce mobility and equal opportunities play a fundamental strategic importance for any central or local Government. The EU SEEMP project aims at improving facilitate workers mobility in Europe. Ontologies are used to model descriptions of job offers and curricula; and for facilitating the process of exchanging job offer data and CV data between ES. In this paper we present the methodological approach we followed for reusing existing human resources management standards in the SEEMP project, in order to build a common “language” called Reference Ontology
Description of the LiLi transfer reaction using structure overlaps from a full three-body model
Recent data on the differential angular distribution for the transfer
reaction Li(p,d)Li at MeV in inverse kinematics are
analysed within the DWBA reaction framework, using the overlap functions
calculated within a three-body model of Li. The weight of the different
Li configurations in the system's ground state is obtained from the
structure calculations unambiguously. The effect of the Li spin in the
calculated observables is also investigated. We find that, although all the
considered models succeed in reproducing the shape of the data, the magnitude
is very sensitive to the content of wave in the Li
ground-state wave function. Among the considered models, the best agreement
with the data is obtained when the Li ground state contains a 31\%
of wave in the -Li subsystem. Although this model takes into
account explicitly the splitting of the and resonances due to the
coupling of the wave to the spin of the core, a similar
degree of agreement can be achieved with a model in which the Li spin is
ignored, provided that it contains a similar p-wave content.Comment: 8 pages, 3 figures. Final versio
A new formulation of compartmental epidemic modelling for arbitrary distributions of incubation and removal times
The paradigm for compartment models in epidemiology assumes exponentially
distributed incubation and removal times, which is not realistic in actual
populations. Commonly used variations with multiple exponentially distributed
variables are more flexible, yet do not allow for arbitrary distributions. We
present a new formulation, focussing on the SEIR concept that allows to include
general distributions of incubation and removal times. We compare the solution
to two types of agent-based model simulations, a spatially homogeneous one
where infection occurs by proximity, and a model on a scale-free network with
varying clustering properties, where the infection between any two agents
occurs via their link if it exists. We find good agreement in both cases.
Furthermore a family of asymptotic solutions of the equations is found in terms
of a logistic curve, which after a non-universal time shift, fits extremely
well all the microdynamical simulations. The formulation allows for a simple
numerical approach; software in Julia and Python is provided.Comment: 21 pages, 11 figures. v2 matches published version: improved
presentation (including title, abstract and references), results and
conclusions unchange
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