4,669 research outputs found
A Realistic Description of Nucleon-Nucleon and Hyperon-Nucleon Interactions in the SU_6 Quark Model
We upgrade a SU_6 quark-model description for the nucleon-nucleon and
hyperon-nucleon interactions by improving the effective meson-exchange
potentials acting between quarks. For the scalar- and vector-meson exchanges,
the momentum-dependent higher-order term is incorporated to reduce the
attractive effect of the central interaction at higher energies. The
single-particle potentials of the nucleon and Lambda, predicted by the G-matrix
calculation, now have proper repulsive behavior in the momentum region q_1=5 -
20 fm^-1. A moderate contribution of the spin-orbit interaction from the
scalar-meson exchange is also included. As to the vector mesons, a dominant
contribution is the quadratic spin-orbit force generated from the rho-meson
exchange. The nucleon-nucleon phase shifts at the non-relativistic energies up
to T_lab=350 MeV are greatly improved especially for the 3E states. The
low-energy observables of the nucleon-nucleon and the hyperon-nucleon
interactions are also reexamined. The isospin symmetry breaking and the Coulomb
effect are properly incorporated in the particle basis. The essential feature
of the Lambda N - Sigma N coupling is qualitatively similar to that obtained
from the previous models. The nuclear saturation properties and the
single-particle potentials of the nucleon, Lambda and Sigma are reexamined
through the G-matrix calculation. The single-particle potential of the Sigma
hyperon is weakly repulsive in symmetric nuclear matter. The single-particle
spin-orbit strength for the Lambda particle is very small, in comparison with
that of the nucleons, due to the strong antisymmetric spin-orbit force
generated from the Fermi-Breit interaction.Comment: Revtex v2.09, 69 pages with 25 figure
Long- and medium-range components of the nuclear force in quark-model based calculations
Quark-model descriptions of the nucleon-nucleon interaction contain two main
ingredients, a quark-exchange mechanism for the short-range repulsion and
meson-exchanges for the medium- and long-range parts of the interaction. We
point out the special role played by higher partial waves, and in particular
the 1F3, as a very sensitive probe for the meson-exchange part employed in
these interaction models. In particular, we show that the presently available
models fail to provide a reasonable description of higher partial waves and
indicate the reasons for this shortcoming.Comment: 19 pages, 7 figure
Estimation of unitary quantum operations
The problem of optimally estimating an unknown unitary quantum operation with
the aid of entanglement is addressed. The idea is to prepare an entangled pair,
apply the unknown unitary to one of the two parts and then measure the joint
output state. This measurement could be an entangled one or it could be
separable (e.g., LOCC). A comparison is made between these possibilities and it
is shown that by using non-separable measurements one can improve the accuracy
of the estimation by a factor of where is the dimension of the
Hilbert space on which acts.Comment: 6 pages. Revised version. Typos corrected. Some discussion added.
Reference fixe
The critical properties of the agent-based model with environmental-economic interactions
The steady-state and nonequilibrium properties of the model of
environmental-economic interactions are studied. The interacting heterogeneous
agents are simulated on the platform of the emission dynamics of cellular
automaton. The model possess the discontinuous transition between the safe and
catastrophic ecology. Right at the critical line, the broad-scale power-law
distributions of emission rates have been identified. Their relationship to
Zipf's law and models of self-organized criticality is discussed.Comment: 12 pages, 6 figures, published in Physica
Shape-Designable Polyhedral Liquid Marbles/Plasticines Stabilized with Polymer Plates
Polyhedral liquid marbles/plasticines are prepared using (sub)millimeter-sized polymer plates as a stabilizer and water as an inner liquid. Precise control of size and shape can be successfully performed by tuning the size ratio of the water droplet and the plate, number of plates adsorbed to the droplet, coalescence (jointing) of multiple polyhedral liquid marbles/plasticines, and application of external mechanical stress. Thanks to interfacial jamming of the plates, plastic deformation of the liquid marbles/plasticines is achieved. The authors are able to fabricate liquid marbles/plasticines with various shapes including AâZ letters of alphabet. Liquid marble/plasticine with an aspect ratio exceeding 800, the largest aspect ratio ever reported, is also successfully prepared; the length of the liquid marble/plasticine exceeded 1.5 m. The liquid marbles can be picked up and be piled up on top of each other using tweezers or fingers. Furthermore, Janus-type liquid marbles/plasticines with different curvatures and different stabilizers in a single liquid marble/plasticine can be fabricated by coalescence (jointing) of near-spherical and cuboid liquid marbles/plasticines stabilized by plates with different sizes. An internal liquid flow from the near-spherical liquid marble to the cuboid liquid marble/plasticine immediately after jointing is observed, making this system act as a micropump
Large-scale structure of a nation-wide production network
Production in an economy is a set of firms' activities as suppliers and
customers; a firm buys goods from other firms, puts value added and sells
products to others in a giant network of production. Empirical study is lacking
despite the fact that the structure of the production network is important to
understand and make models for many aspects of dynamics in economy. We study a
nation-wide production network comprising a million firms and millions of
supplier-customer links by using recent statistical methods developed in
physics. We show in the empirical analysis scale-free degree distribution,
disassortativity, correlation of degree to firm-size, and community structure
having sectoral and regional modules. Since suppliers usually provide credit to
their customers, who supply it to theirs in turn, each link is actually a
creditor-debtor relationship. We also study chains of failures or bankruptcies
that take place along those links in the network, and corresponding
avalanche-size distribution.Comment: 17 pages with 8 figures; revised section VI and references adde
Seasonal variations of CO and HCN in the troposphere measured by solar absorption spectroscopy over Poker Flat, Alaska
Tropospheric partial column abundances of CO and HCN have been retrieved from infrared solar spectra observed with a ground-based spectrometer at Poker Flat Alaska (65°N, 147°W) over the time period from 2000 to 2004. From these data we report the transpacific transport induced inter-annual variability of tropospheric CO over Poker Flat. This is the first report of solar infrared data from the Poker Flat station, where the geographical location of the site means that remote sensing measurements are sampling the transport of transpacific air parcels going to Northern America from Eastern Siberia and Asia. The five year time-span of the data also show significant differences in year to year CO and HCN tropospheric column enhancements driven by changes in Siberian/Asian pollution sources
Measurement of the Xi-p Scattering Cross Sections at Low Energy
In this paper we report cross-section measurements for elastic and
inelastic scatterings at low energy using a scintillating fiber active target.
Upper limit on the total cross-section for the elastic scattering was found to
be 24 mb at 90% confidence level, and the total cross section for the
reaction was found to be mb. We
compare the results with currently competing theoretical estimates.Comment: 9 page
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