162 research outputs found
Final-state interactions in the response of nuclear matter
Final-state interactions in the response of a many-body system to an external
probe delivering large momentum are normally described using the eikonal
approximation, for the trajectory of the struck particle, and the frozen
approximation, for the positions of the spectators. We propose a generalization
of this scheme, in which the initial momentum of the struck particle is
explicitly taken into account. Numerical calculations of the nuclear matter
response at 1 2 GeV/c show that the inclusion of this momentum
dependence leads to a sizable effect in the low energy tail. Possible
implications for the analysis of existing electron-nucleus scattering data are
discussed.Comment: 21 pages, 4 figure
Deuteron distribution in nuclei and the Levinger's factor
We compute the distribution of quasideuterons in doubly closed shell nuclei.
The ground states of O and Ca are described in coupling
using a realistic hamiltonian including the Argonne and the
Urbana IX models of two-- and three--nucleon potentials, respectively. The
nuclear wave function contains central and tensor correlations, and correlated
basis functions theory is used to evaluate the distribution of neutron-proton
pairs, having the deuteron quantum numbers, as a function of their total
momentum. By computing the number of deuteron--like pairs we are able to
extract the Levinger's factor and compare to both the available experimental
data and the predictions of the local density approximation, based on nuclear
matter estimates. The agreement with the experiments is excellent, whereas the
local density approximation is shown to sizably overestimate the Levinger's
factor in the region of the medium nuclei.Comment: 26 pages, 8 figures, typeset using REVTe
Neutron star matter equation of state and gravitational wave emission
The EOS of strongly interacting matter at densities ten to fifteen orders of
magnitude larger than the typical density of terrestrial macroscopic objects
determines a number of neutron star properties, including the pattern of
gravitational waves emitted following the excitation of nonradial oscillation
modes. This paper reviews some of the approaches employed to model neutron star
matter, as well as the prospects for obtaining new insights from the
experimental study of gravitational waves emitted by neutron stars.Comment: 15 pages, 8 figures. To be published as a Brief Review in Modern
Physics Letters
Multipair contributions to the spin response of nuclear matter
We analyse the effect of non-central forces on the magnetic susceptibility of
degenerate Fermi systems. These include the presence of contributions from
transitions to states containing more than one quasiparticle-quasihole pair,
which cannot be calculated within the framework of Landau Fermi-liquid theory,
and renormalization of the quasiparticle magnetic moment, as well as explicit
non-central contributions to the quasiparticle interaction. Consequently, the
relationship between the Landau parameters and the magnetic susceptibility for
Fermi systems with non-central forces is considerably more complicated than for
systems with central forces. We use sum-rule arguments to place a lower bound
on the contribution to the static susceptibility coming from transitions to
multipair states
Spin susceptibility of neutron matter at zero temperature
The Auxiliary Field Diffusion Monte Carlo method is applied to compute the
spin susceptibility and the compressibility of neutron matter at zero
temperature. Results are given for realistic interactions which include both a
two-body potential of the Argonne type and the Urbana IX three-body potential.
Simulations have been carried out for about 60 neutrons. We find an overall
reduction of the spin susceptibilty by about a factor 3 with respect to the
Pauli susceptibility for a wide range of densities. Results for the
compressibility of neutron matter are also presented and compared with other
available estimates obtained for semirealistic nucleon-nucleon interactions by
using other techniques
Magnetars as cooling neutron stars with internal heating
We study thermal structure and evolution of magnetars as cooling neutron
stars with a phenomenological heat source in a spherical internal layer. We
explore the location of this layer as well as the heating rate that could
explain high observable thermal luminosities of magnetars and would be
consistent with the energy budget of neutron stars. We conclude that the heat
source should be located in an outer magnetar's crust, at densities rho < 5e11
g/cm^3, and should have the heat intensity of the order of 1e20 erg/s/cm^3.
Otherwise the heat energy is mainly emitted by neutrinos and cannot warm up the
surface.Comment: 8 pages, 5 figures, submitted to MNRA
Thermodynamic Properties of Holographic Multiquark and the Multiquark Star
We study thermodynamic properties of the multiquark nuclear matter. The
dependence of the equation of state on the colour charges is explored both
analytically and numerically in the limits where the baryon density is small
and large at fixed temperature between the gluon deconfinement and chiral
symmetry restoration. The gravitational stability of the hypothetical
multiquark stars are discussed using the Tolman-Oppenheimer-Volkoff equation.
Since the equations of state of the multiquarks can be well approximated by
different power laws for small and large density, the content of the multiquark
stars has the core and crust structure. We found that most of the mass of the
star comes from the crust region where the density is relatively small. The
mass limit of the multiquark star is determined as well as its relation to the
star radius. For typical energy density scale of ,
the converging mass and radius of the hypothetical multiquark star in the limit
of large central density are approximately solar mass and 15-27 km.
The adiabatic index and sound speed distributions of the multiquark matter in
the star are also calculated and discussed. The sound speed never exceeds the
speed of light and the multiquark matters are thus compressible even at high
density and pressure.Comment: 27 pages, 17 figures, 1 table, JHEP versio
Ground State Correlations in 16O and 40Ca
We study the ground state properties of doubly closed shell nuclei O
and Ca in the framework of Correlated Basis Function theory using state
dependent correlations, with central and tensor components. The realistic
Argonne and two-nucleon potentials and three-nucleon
potentials of the Urbana class have been adopted. By means of the Fermi
Hypernetted Chain integral equations, in conjunction with the Single Operator
Chain approximation, we evaluate the ground state energy, one- and two-body
densities and electromagnetic and spin static responses for both nuclei. In
O we compare our results with the available Monte Carlo and Coupled
Cluster ones and find a satisfying agreement. As in the nuclear matter case
with similar interactions and wave functions, the nuclei result under-bound by
2--3 MeV/A.Comment: 33 RevTeX pages + 8 figures, to appear in Phys.Rev.
A Self-Consistent Solution to the Nuclear Many-Body Problem at Finite Temperature
The properties of symmetric nuclear matter are investigated within the
Green's functions approach. We have implemented an iterative procedure allowing
for a self-consistent evaluation of the single-particle and two-particle
propagators. The in-medium scattering equation is solved for a realistic
(non-separable) nucleon-nucleon interaction including both particle-particle
and hole-hole propagation. The corresponding two-particle propagator is
constructed explicitely from the single-particle spectral functions. Results
are obtained for finite temperatures and an extrapolation to T=0 is presented.Comment: 11 pages 5 figure
Short-range correlations in low-lying nuclear excited states
The electromagnetic transitions to various low-lying excited states of 16O,
48Ca and 208Pb are calculated within a model which considers the short-range
correlations. In general the effects of the correlations are small and do not
explain the required quenching to describe the data.Comment: 6 pages, 2 postscript figures, 1 tabl
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