2,881 research outputs found
Neutron star properties in the Thomas-Fermi model
The modern nucleon-nucleon interaction of Myers and Swiatecki, adjusted to
the properties of finite nuclei, the parameters of the mass formula, and the
behavior of the optical potential is used to calculate the properties of
--equilibrated neutron star matter, and to study the impact of this
equation of state on the properties of (rapidly rotating) neutron stars and
their cooling behavior. The results are in excellent agreement with the outcome
of calculations performed for a broad collection of sophisticated
nonrelativistic as well as relativistic models for the equation of state.Comment: 23 pages, LaTeX, 15 ps-figure
Compatibility of neutron star masses and hyperon coupling constants
It is shown that the modern equations of state for neutron star matter based
on microscopic calculations of symmetric and asymmetric nuclear matter are
compatible with the lower bound on the maximum neutron-star mass for a certain
range of hyperon coupling constants, which are constrained by the binding
energies of hyperons in symmetric nuclear matter. The hyperons are included by
means of the relativistic Hartree-- or Hartree--Fock approximation. The
obtained couplings are also in satisfactory agreement with hypernuclei data in
the relativistic Hartree scheme. Within the relativistic Hartree--Fock
approximation hypernuclei have not been investigated so far.Comment: 12 pages, 3 figures. Dedicated to Prof. Georg Suessmann on the
occasion of his 70th birthday. To be published in Zeitschrift fuer
Naturforschung
Symmetric and asymmetric nuclear matter in the relativistic approach at finite temperatures
The properties of hot matter are studied in the frame of the relativistic
Brueckner-Hartree-Fock theory. The equations are solved self-consistently in
the full Dirac space. For the interaction we used the potentials given by
Brockmann and Machleidt. The obtained critical temperatures are smaller than in
most of the nonrelativistic investigations. We also calculated the
thermodynamic properties of hot matter in the relativistic Hartree--Fock
approximation, where the force parameters were adjusted to the outcome of the
relativistic Brueckner--Hartree--Fock calculations at zero temperature. Here,
one obtains higher critical temperatures, which are comparable with other
relativistic calculations in the Hartree scheme.Comment: 8 pages, 9 figures, submitted in a shorter version to Phys. Rev.
Scaling Behavior in Soliton Models
In the framework of chiral soliton models we study the behavior of static
nucleon properties under rescaling of the parameters describing the effective
meson theory. In particular we investigate the question of whether the
Brown--Rho scaling laws are general features of such models. When going beyond
the simple Skyrme model we find that restrictive constraints need to be imposed
on the mesonic parameters in order to maintain these scaling laws. Furthermore,
in the case when vector mesons are included in the model it turns out that the
isoscalar form factor no longer scales according to these laws. Finally we note
that, in addition to the exact scaling laws of the model, one may construct
approximate {\it local scaling laws}, which depend of the particular choice of
Lagrangian parameters.Comment: 10 pages Latex, figures added using epsfi
The reliability of simple progressive dies
The stamping process, of which the punching process is a major division, is one of the most important metal parts production methods in industry. Punching dies are the heart of the punching process. Die performance, as measured by the number of strokes between sharpenings and/or repairs, determines the important per part costs of die depletion and maintenance. Existing quantitative studies are principally on tool wear and punchability
Soliton Models for the Nucleon and Predictions for the Nucleon Spin Structure
In these lectures the three flavor soliton approach for baryons is reviewed.
Effects of flavor symmetry breaking in the baryon wave--functions on axial
current matrix elements are discussed. A bosonized chiral quark model is
considered to outline the computation of spin dependent nucleon structure
functions in the soliton picture.Comment: 12 pages, Lectures presented at the Advanced Study Institute Symmetry
and Spin, Prague, 2001, to appear in the proceedings. References correcte
Phase Field Crystal model for particles with n-fold rotational symmetry in two dimensions
We introduce a Phase Field Crystal (PFC) model for particles with n-fold
rotational symmetry in two dimensions. Our approach is based on a free energy
functional that depends on the reduced one-particle density, the strength of
the orientation, and the direction of the orientation, where all these order
parameters depend on the position. The functional is constructed such that for
particles with axial symmetry (i. e. n = 2) the PFC model for liquid crystals
as introduced by H. L\"owen [J. Phys.: Condens. Matter 22, 364105 (2010)] is
recovered. We discuss the stability of the functional and explore phases that
occur for . In addition to isotropic, nematic, stripe, and
triangular order, we also observe cluster crystals with square, rhombic,
honeycomb, and even quasicrystalline symmetry. The n-fold symmetry of the
particles corresponds to the one that can be realized for colloids with
symmetrically arranged patches. We explain how both, repulsive as well as
attractive patches, are described in our model.Comment: 20 pages, 12 figure
Chiral Quark Model
In this talk I review studies of hadron properties in bosonized chiral quark
models for the quark flavor dynamics. Mesons are constructed from
Bethe--Salpeter equations and baryons emerge as chiral solitons. Such models
require regularization and I show that the two--fold Pauli--Villars
regularization scheme not only fully regularizes the effective action but also
leads the scaling laws for structure functions. For the nucleon structure
functions the present approach serves to determine the regularization
prescription for structure functions whose leading moments are not given by
matrix elements of local operators. Some numerical results are presented for
the spin structure functions.Comment: Talk presented at the workshop QCD 2002, IIT Kanpur, Nov. 2002, 10
pages, proceedings style files include
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