182 research outputs found
Two- and three-alpha systems with nonlocal potential
Two body data alone cannot determine the potential uniquely, one needs
three-body data as well. A method is presented here which simultaneously fits
local or nonlocal potentials to two-body and three-body observables. The
interaction of composite particles, due to the Pauli effect and the
indistinguishability of the constituent particles, is genuinely nonlocal. As an
example, we use a Pauli-correct nonlocal fish-bone type optical model for the
potential and derive the fitting parameters such that it
reproduces the two- and three- experimental data.Comment: 16 pages, 5 figures, Inverse Scattering Conference, Aug 2007, Siofok,
Hungary New reference adde
Incompressibility in finite nuclei and nuclear matter
The incompressibility (compression modulus) of infinite symmetric
nuclear matter at saturation density has become one of the major constraints on
mean-field models of nuclear many-body systems as well as of models of high
density matter in astrophysical objects and heavy-ion collisions. We present a
comprehensive re-analysis of recent data on GMR energies in even-even Sn and Cd and earlier data on 58 A 208
nuclei. The incompressibility of finite nuclei is expressed as a
leptodermous expansion with volume, surface, isospin and Coulomb coefficients
, , and . \textit{Assuming}
that the volume coefficient is identified with , the
= -(5.2 0.7) MeV and the contribution from the curvature
term KA in the expansion is neglected, compelling
evidence is found for to be in the range 250 315
MeV, the ratio of the surface and volume coefficients to be between -2.4 and -1.6 and between -840 and -350 MeV.
We show that the generally accepted value of = (240 20) MeV
can be obtained from the fits provided -1, as predicted by the
majority of mean-field models. However, the fits are significantly improved if
is allowed to vary, leading to a range of , extended to higher
values. A self-consistent simple (toy) model has been developed, which shows
that the density dependence of the surface diffuseness of a vibrating nucleus
plays a major role in determination of the ratio K and
yields predictions consistent with our findings.Comment: 26 pages, 13 figures; corrected minor typos in line with the proof in
Phys. Rev.
Short range correlations in relativistic nuclear matter models
Short range correlations are introduced using unitary correlation method in a
relativistic approach to the equation of state of the infinite nuclear matter
in the framework of the Hartree-Fock approximation. It is shown that the
correlations give rise to an extra node in the ground-state wave-function in
the nucleons, contrary to what happens in non-relativistic calculations with a
hard core. The effect of the correlations in the ground state properties of the
nuclear matter and neutron matter is studied. The nucleon effective mass and
equation of state (EOS) are very sensitive to short range correlations. In
particular, if the pion contact term is neglected a softening of the EOS is
predicted. Correlations have also an important effect on the neutron matter EOS
which presents no binding but only a very shallow minimum contrary to the
Walecka model.Comment: 8pages, 4 figure
A Complete Axiom System for Propositional Interval Temporal Logic with Infinite Time
Interval Temporal Logic (ITL) is an established temporal formalism for
reasoning about time periods. For over 25 years, it has been applied in a
number of ways and several ITL variants, axiom systems and tools have been
investigated. We solve the longstanding open problem of finding a complete
axiom system for basic quantifier-free propositional ITL (PITL) with infinite
time for analysing nonterminating computational systems. Our completeness proof
uses a reduction to completeness for PITL with finite time and conventional
propositional linear-time temporal logic. Unlike completeness proofs of equally
expressive logics with nonelementary computational complexity, our semantic
approach does not use tableaux, subformula closures or explicit deductions
involving encodings of omega automata and nontrivial techniques for
complementing them. We believe that our result also provides evidence of the
naturalness of interval-based reasoning
Deformed nuclear halos
Deformation properties of weakly bound nuclei are discussed in the deformed
single-particle model. It is demonstrated that in the limit of a very small
binding energy the valence particles in specific orbitals, characterized by a
very small projection of single-particle angular momentum onto the symmetry
axis of a nucleus, can give rise to the halo structure which is completely
decoupled from the rest of the system. The quadrupole deformation of the
resulting halo is completely determined by the intrinsic structure of a weakly
bound orbital, irrespective of the shape of the core.Comment: LaTeX source (21 pages) and postscript file with figures (15 pages).
Accepted to Nucl. Phys.
Improved lower bounds for the ground-state energy of many-body systems
New lower bounds for the binding energy of a quantum-mechanical system of
interacting particles are presented. The new bounds are expressed in terms of
two-particle quantities and improve the conventional bounds of the Hall-Post
type. They are constructed by considering not only the energy in the
two-particle system, but also the structure of the pair wave function. We apply
the formal results to various numerical examples, and show that in some cases
dramatic improvement over the existing bounds is reached.Comment: 29 pages, 5 figures, to be published in Phys. Rev.
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