152 research outputs found
Identification of Oceanographic Parameters for Determining Pelagic Tuna Fishing Ground in the North Papua Waters Using Multi-sensor Satellite Data
The North Papua waters as one of the important fishing grounds in the world contribute approximately 75% of world production of pelagic tunas. These fishing grounds are still determined by hunting method. This method is time consuming and costly. However, in many areas determination of fishing ground using satellited data lias been applied by detecting the important oceanographic parameter of the presence of fish schooling such as, sea surface temperature and chlorophyl. Mostly these parameters are used integratedly. The aim of this study is to assess the important oceanographic parameters detected from multi-sensor satellites (NOAA/AVHRR, Seawifs and Topex Poisedon) for determining fishing ground of pelagic tunas in the North Papua waters at east season. The parameters include Sea Surface Temperature (STT), chlorophyl-a and currents. The availability of data from optic sensor (Seawifs: chl-a and AVHRR: Thermal) is limited by the presence of cloud cover. In that case, Topex Poseidon satellite data can be used to provide the currents data. The integration of data from multi-sensors increases the availability of the oceanographic parameters for prediction of the potential fishing zones in the study area
- nucleus relativistic mean field potentials consistent with kaonic atoms
atomic data are used to test several models of the nucleus
interaction. The t() optical potential, due to coupled channel
models incorporating the (1405) dynamics, fails to reproduce these
data. A standard relativistic mean field (RMF) potential, disregarding the
(1405) dynamics at low densities, also fails. The only successful
model is a hybrid of a theoretically motivated RMF approach in the nuclear
interior and a completely phenomenological density dependent potential, which
respects the low density theorem in the nuclear surface region. This best-fit
optical potential is found to be strongly attractive, with a depth of 180
\pm 20 MeV at the nuclear interior, in agreement with previous phenomenological
analyses.Comment: revised, Phys. Rev. C in pres
Incremental expansions for Hubbard-Peierls systems
The ground state energies of infinite half-filled Hubbard-Peierls chains are
investigated combining incremental expansion with exact diagonalization of
finite chain segments. The ground state energy of equidistant infinite Hubbard
(Heisenberg) chains is calculated with a relative error of less than for all values of using diagonalizations of 12-site (20-site)
chain segm ents. For dimerized chains the dimerization order parameter as a
function of the onsite repulsion interaction has a maximum at nonzero
values of , if the electron-phonon coupling is lower than a critical
value . The critical value is found with high accuracy to be
. For smaller values of the position of the maximum of is
approximately , and rapidly tends to zero as approaches from
below. We show how our method can be applied to calculate breathers for the
problem of phonon dynamics in Hubbard-Peierls systems.Comment: 4 Pages, 3 Figures, REVTE
Solitonic approach to the dimerization problem in correlated one-dimensional systems
Using exact diagonalizations we consider self-consistently the lattice
distortions in odd Peierls-Hubbard and spin-Peierls periodic rings in the
adiabatic harmonic approximation. From the tails of the inherent spin soliton
the dimerization d_\infty of regular even rings is found by extrapolations to
infinite ring lengths. Considering a wide region of electron-electron onsite
interaction values U>0 compared with the band width 4t_0 at intermediately
strong electron-phonon interaction g, known relationships obtained by other
methods are reproduced and/or refined within one unified approach: such as the
maximum of d_\infty at U \simeq 3 t_0 for g \simeq 0.5 and its shift to zero
for g \to g_c \approx 0.7. The hyperbolic tangent shape of the spin soliton is
retained for any U and g <~ 0.6. In the spin-Peierls limit the d_\infty are
found to be in agreement with results of DMRG computations.Comment: 4 pages, 4 figures, Physical Review B, Rapid Communications, v. 56
(1997) accepte
Kaon effective mass and energy from a novel chiral SU(3)-symmetric Lagrangian
A new chiral SU(3) Lagrangian is proposed to describe the properties of kaons
and antikaons in the nuclear medium, the ground state of dense matter and the
kaon-nuclear interactions consistently.
The saturation properties of nuclear matter are reproduced as well as the
results of the Dirac-Br\"{u}ckner theory. Our numerical results show that the
kaon effective mass might be changed only moderately in the nuclear medium due
to the highly non-linear density effects. After taking into account the
coupling between the omega meson and the kaon, we obtain similar results for
the effective kaon and antikaon energies as calculated in the
one-boson-exchange model while in our model the parameters of the kaon-nuclear
interactions are constrained by the SU(3) chiral symmetry.Comment: 13 pages, Latex, 3 PostScript figures included; replaced by the
revised version, to appear in Phys. Rev.
Constraints on the threshold K- nuclear potential from FINUDA (stopped K-, pi-) hypernuclear spectra
1s(Lambda) hypernuclear formation rates in stopped K- reactions on several
p-shell targets are derived from hypernuclear formation spectra measured
recently by the FINUDA Collaboration and are compared with calculated
1s(Lambda) formation rates based on a KbarN coupled channels chiral model. The
calculated rates are about 15% of the derived rates, depending weakly on the
depth of the threshold K- nuclear potential. The A dependence of the calculated
rates is in fair agreement with that of the derived rates, showing a slight
preference for a deep density dependent K- nuclear potential of depth (150-200)
MeV at nuclear matter density over a shallow potential of depth about 50 MeV.
These new features originate from a substantial energy and density dependence
found for the in-medium subthreshold (K- n --> pi- Lambda) branching ratio that
serves as input to the K- capture at rest calculations.Comment: 12 pages, 2 figures, 2 tables; v2 is a substantially revised version,
v3 matches journal versio
First Order Kaon Condensate
First order Bose condensation in asymmetric nuclear matter and in neutron
stars is studied, with particular reference to kaon condensation. We
demonstrate explicitly why the Maxwell construction fails to assure equilibrium
in multicomponent substances. Gibbs conditions and conservation laws require
that for phase equilibrium, the charge density must have opposite sign in the
two phases of isospin asymmetric nuclear matter. The mixed phase will therefore
form a Coulomb lattice with the rare phase occupying lattice sites in the
dominant phase. Moreover, the kaon condensed phase differs from the normal
phase, not by the mere presence of kaons in the first, but also by a difference
in the nucleon effective masses. The mixed phase region, which occupies a large
radial extent amounting to some kilometers in our model neutron stars, is thus
highly heterogeneous. It should be particularly interesting in connection with
the pulsar glitch phenomenon as well as transport properties.Comment: 25 pagees, 20 figures, Late
Nonequilibrium Weak Processes in Kaon Condensation II - Kinetics of condensation ---
The kinetics of negatively charged kaon condensation in the early stages of a
newly born neutron star is considered. The thermal kaon process, in which kaons
are thermally produced by nucleon-nucleon collisions, is found to be dominant
throughout the equilibration process. Temporal changes of the order parameter
of the condensate and the number densities of the chemical species are obtained
from the rate equations, which include the thermal kaon reactions as well as
the kaon-induced Urca and the modified Urca reactions. It is shown that the
dynamical evolution of the condensate is characterized by three stages: the
first, prior to establishment of a condensate, the second, during the growth
and subsequent saturation of the condensate, and the third, near chemical
equilibrium. The connection between the existence of a soft kaon mode and the
instability of the noncondensed state is discussed. Implications of the
nonequilibrium process on the possible delayed collapse of a protoneutron star
are also mentioned.Comment: 27 pages, incl. 8 eps figures, RevTe
On the correllation effect in Peierls-Hubbard chains
We reexamine the dimerization, the charge and the spin gaps of a half-filled
Peierls-Hubbard chain by means of the incremental expansion technique. Our
numerical findings are in significant quantitative conflict with recently
obtained results by M. Sugiura and Y. Suzumura [J. Phys. Soc. Jpn. v. 71 (2002)
697] based on a bosonization and a renormalization group method, especially
with respect to the charge gap. Their approach seems to be valid only in the
weakly correlated case.Comment: 7pages,4figures(6eps-files
Chiral dynamics of baryon resonances and hadrons in a nuclear medium
In these lectures I make an introduction to chiral unitary theory applied to
the meson baryon interaction and show how several well known resonances are
dynamically generated, and others are predicted. Two very recent experiments
are analyzed, one of them showing the existence of two
states and the other one providing support for the
resonance as a quasibound state of . The
use of chiral Lagrangians to account for the hadronic interaction at the
elementary level introduces a new approach to deal with the modification of
meson and baryon properties in a nuclear medium. Examples of it for ,
and modification in the nuclear medium are presented.Comment: Lectures given in the Workshop on Hadron Physics, Puri (India), march
200
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