21,200 research outputs found
Low-momentum interactions with Brown-Rho-Ericson scalings and the density dependence of the nuclear symmetry energy
We have calculated the nuclear symmetry energy up to
densities of with the effects from the Brown-Rho (BR) and
Ericson scalings for the in-medium mesons included. Using the
low-momentum interaction with and without such scalings, the equations of state
(EOS) of symmetric and asymmetric nuclear matter have been calculated using a
ring-diagarm formalism where the particle-particle-hole-hole ring diagrams are
included to all orders. The EOS for symmetric nuclear matter and neutron matter
obtained with linear BR scaling are both overly stiff compared with the
empirical constraints of Danielewicz {\it et al.} \cite{daniel02}. In contrast,
satisfactory results are obtained by either using the nonlinear Ericson scaling
or by adding a Skyrme-type three-nucleon force (TNF) to the unscaled
interaction.
Our results for obtained with the nonlinear Ericson scaling
are in good agreement with the empirical values of Tsang {\it et al.}
\cite{tsang09} and Li {\it et al.} \cite{li05}, while those with TNF are
slightly below these values. For densities below the nuclear saturation density
, the results of the above calculations are nearly equivalent to each
other and all in satisfactory agreement with the empirical values.Comment: 7 pages, 6 figure
Shell model description of the 14C dating beta decay with Brown-Rho-scaled NN interactions
We present shell model calculations for the beta-decay of the 14C ground
state to the 14N ground state, treating the states of the A=14 multiplet as two
0p holes in an 16O core. We employ low-momentum nucleon-nucleon (NN)
interactions derived from the realistic Bonn-B potential and find that the
Gamow-Teller matrix element is too large to describe the known lifetime. By
using a modified version of this potential that incorporates the effects of
Brown-Rho scaling medium modifications, we find that the GT matrix element
vanishes for a nuclear density around 85% that of nuclear matter. We find that
the splitting between the (J,T)=(1+,0) and (J,T)=(0+,1) states in 14N is
improved using the medium-modified Bonn-B potential and that the transition
strengths from excited states of 14C to the 14N ground state are compatible
with recent experiments.Comment: 4 pages, 5 figures Updated to include referee comments/suggestion
Criteria for the use of regression analysis for remote sensing of sediment and pollutants
Data analysis procedures for quantification of water quality parameters that are already identified and are known to exist within the water body are considered. The liner multiple-regression technique was examined as a procedure for defining and calibrating data analysis algorithms for such instruments as spectrometers and multispectral scanners
Suppression of core polarization in halo nuclei
We present a microscopic study of halo nuclei, starting from the Paris and
Bonn potentials and employing a two-frequency shell model approach. It is found
that the core-polarization effect is dramatically suppressed in such nuclei.
Consequently the effective interaction for halo nucleons is almost entirely
given by the bare G-matrix alone, which presently can be evaluated with a high
degree of accuracy. The experimental pairing energies between the two halo
neutrons in He and Li nuclei are satisfactorily reproduced by our
calculation. It is suggested that the fundamental nucleon-nucleon interaction
can be probed in a clearer and more direct way in halo nuclei than in ordinary
nuclei.Comment: 11 pages, RevTex, 2 postscript figures; major revisions, matches
version to appear in Phys. Rev. Letter
Quark Mass Matrices with Four and Five Texture Zeroes, and the CKM Matrix, in terms of Mass Eigenvalues
Using the triangular matrix techniques of Kuo et al and Chiu et al for the
four and five texture zero cases, with vanishing (11) elements for U and D
matrices, it is shown, from the general eigenvalue equations and hierarchy
conditions, that the quark mass matrices, and the CKM matrix can be expressed
(except for the phases) entirely in terms of quark masses. The matrix
structures are then quite simple and transparent. We confirm their results for
the five texture zero case but find, upon closer examination of all the CKM
elements which our results provide, that six of their nine patterns for the
four texture zero case are not compatible with experiments. In total, only one
five-texture zero and three four-texture zero patterns are allowed.Comment: 15 pages, 3 table
Family of Hermitian Low-Momentum Nucleon Interactions with Phase Shift Equivalence
Using a Schmidt orthogonalization transformation, a family of Hermitian
low-momentum NN interactions is derived from the non-Hermitian Lee-Suzuki (LS)
low-momentum NN interaction. As special cases, our transformation reproduces
the Hermitian interactions for Okubo and Andreozzi. Aside from their common
preservation of the deuteron binding energy, these Hermitian interactions are
shown to be phase shift equivalent, all preserving the empirical phase shifts
up to decimation scale Lambda. Employing a solvable matrix model, the Hermitian
interactions given by different orthogonalization transformations are studied;
the interactions can be very different from each other particularly when there
is a strong intruder state influence. However, because the parent LS
low-momentum NN interaction is only slightly non-Hermitian, the Hermitian
low-momentum nucleon interactions given by our transformations, including the
Okubo and Andreozzi ones, are all rather similar to each other. Shell model
matrix elements given by the LS and several Hermitian low-momentum interactions
are compared.Comment: 10 pages, 7 figure
Low-momentum ring diagrams of neutron matter at and near the unitary limit
We study neutron matter at and near the unitary limit using a low-momentum
ring diagram approach. By slightly tuning the meson-exchange CD-Bonn potential,
neutron-neutron potentials with various scattering lengths such as
and are constructed. Such potentials are renormalized
with rigorous procedures to give the corresponding -equivalent
low-momentum potentials , with which the low-momentum
particle-particle hole-hole ring diagrams are summed up to all orders, giving
the ground state energy of neutron matter for various scattering lengths.
At the limit of , our calculated ratio of to that of
the non-interacting case is found remarkably close to a constant of 0.44 over a
wide range of Fermi-momenta. This result reveals an universality that is well
consistent with the recent experimental and Monte-Carlo computational study on
low-density cold Fermi gas at the unitary limit. The overall behavior of this
ratio obtained with various scattering lengths is presented and discussed.
Ring-diagram results obtained with and those with -matrix
interactions are compared.Comment: 9 pages, 7 figure
Low Momentum Nucleon-Nucleon Interactions and Shell-Model Calculations
In the last few years, the low-momentum nucleon-nucleon (NN) interaction
V-low-k derived from free-space NN potentials has been successfully used in
shell-model calculations. V-low-k is a smooth potential which preserves the
deuteron binding energy as well as the half-on-shell T-matrix of the original
NN potential up to a momentum cutoff Lambda. In this paper we put to the test a
new low-momentum NN potential derived from chiral perturbation theory at
next-to-next-to-next-to-leading order with a sharp low-momentum cutoff at 2.1
fm-1. Shell-model calculations for the oxygen isotopes using effective
hamiltonians derived from both types of low-momentum potential are performed.
We find that the two potentials show the same perturbative behavior and yield
very similar results.Comment: 8 pages, 8 figures, to be published in Physical Review
Half-Skyrmions and the Equation of State for Compact-Star Matter
The half-skyrmions that appear in dense baryonic matter when skyrmions are
put on crystals modify drastically hadron properties in dense medium and affect
strongly the nuclear tensor forces, thereby influencing the equation of state
(EoS) of dense nuclear and asymmetric nuclear matter. The matter comprised of
half skyrmions has vanishing quark condensate but non-vanishing pion decay
constant and could be interpreted as a hadronic dual of strong-coupled quark
matter. We infer from this observation combined with certain predictions of
hidden local symmetry in low-energy hadronic interactionsa a set of new scaling
laws -- called "new-BR" -- for the parameters in nuclear effective field theory
controlled by renormalization-group flow. They are subjected to the EoS of
symmetric and asymmetric nuclear matter, and are then applied to nuclear
symmetry energies and properties of compact stars. The changeover from the
skyrmion matter to a half-skyrmion matter that takes place after the cross-over
density provides a simple and natural field theoretic explanation for
the change of the EoS from soft to stiff at a density above that of nuclear
matter required for compact stars as massive as . Cross-over
density in the range 1.5n_0 \lsim n_{1/2} \lsim 2.0 n_0 has been employed,
and the possible skyrmion half-skyrmion coexistence {or cross-over} near
is discussed. The novel structure of {the tensor forces and} the EoS
obtained with the new-BR scaling is relevant for neutron-rich nuclei and
compact star matter and could be studied in RIB (rare isotope beam) machines.Comment: 12 pages, 7 figures, slightly revised for PRC, in pres
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