title: Density Dependent Hadron Field Theory

abstract:
  A fully covariant approach to a density dependent hadron field theory is
presented. The relation between in--medium NN interactions and
field--theoretical meson--nucleon vertices is discussed. The medium dependence
of nuclear interactions is described by a functional dependence of the
meson--nucleon vertices on the baryon field operators. As a consequence, the
Euler--Lagrange equations lead to baryon rearrangement self--energies which are
not obtained when only a parametric dependence of the vertices on the density
is assumed. It is shown that the approach is energy--momentum conserving and
thermodynamically consistent. Solutions of the field equations are studied in
the mean--field approximation. Descriptions of the medium dependence in terms
of the baryon scalar and vector density are investigated. Applications to
infinite nuclear matter and finite nuclei are discussed. Density dependent
coupling constants obtained from Dirac--Brueckner calculations with the Bonn
NN-potentials are used. Results from Hartree calculations for energy spectra,
binding energies and charge density distributions of $^{16}O$, $^{40,48}Ca$ and
$^{208}Pb$ are presented. Comparisons to data strongly support the importance
of rearrangement in a relativistic density dependent field theory. Most
striking is the simultanuous improvement of charge radii, charge densities and
binding energies. The results indicate the appearance of a new "Coester line"
in the nuclear matter equation of state.


title:
Collisions of Deformed Nuclei: A Path to the Far Side of the Superheavy
  Island

abstract:
  A detailed understanding of complete fusion cross sections in heavy-ion
collisions requires a consideration of the effects of the deformation of the
projectile and target. Our aim here is to show that deformation and orientation
of the colliding nuclei have a very significant effect on the fusion-barrier
height and on the compactness of the touching configuration. To facilitate
discussions of fusion configurations of deformed nuclei, we develop a
classification scheme and introduce a notation convention for these
configurations. We discuss particular deformations and orientations that lead
to compact touching configurations and to fusion-barrier heights that
correspond to fairly low excitation energies of the compound systems. Such
configurations should be the most favorable for producing superheavy elements.
We analyse a few projectile-target combinations whose deformations allow
favorable entrance-channel configurations and whose proton and neutron numbers
lead to compound systems in a part of the superheavy region where alpha
half-lives are calculated to be observable, that is, longer than 1 microsecond.


title:
Volume, Coulomb, and volume-symmetry coefficients of nucleus
  incompressibility in the relativistic mean field theory with the excluded
  volume effects

abstract:
  The relation among the volume coefficient $K$(=incompressibility of the
nuclear matter), the Coulomb coefficient $K_c$, and the volume-symmetry
coefficient $K_{vs}$ of the nucleus incompressibility are studied in the
framework of the relativistic mean field theory with the excluded volume
effects of the nucleons, under the assumption of the scaling model. It is found
that $K= 300\pm 50$MeV is necessary to account for the empirical values of $K$,
$K_c$, and $K_{vs}$, simultaneously, as is in the case of the point-like
nucleons. The result is independent on the detail descriptions of the potential
of the $\sigma$-meson self-interaction and is almost independent on the
excluded volume of the nucleons.


title: Thermal fission rate around super-normal phase transition

abstract:
  Using Langer's $Im F$ method, we discuss the temperature dependence of
nuclear fission width in the presence of dissipative environments. We introduce
a low cut-off frequency to the spectral density of the environmental
oscillators in order to mimic the pairing gap. It is shown that the decay width
rapidly decreases at the critical temperature, where the phase transition from
super to normal fluids takes place. Relation to the recently observed threshold
for the dissipative fission is discussed.


title: Bose-Einstein correlations in thermal field theory

abstract:
  Two-particle correlation functions are calculated for bosons emitted from a
localized thermal source (the ``glow'' of a ``hot spot''). In contrast to
existing work, non-equilibrium effects up to first order in gradients of the
particle distribution function are taken into account. The spectral width of
the bosons is shown to be an important quantity: If it is too small, they do
not equilibrate locally and therefore strongly increase the measured
correlation radius. In memoriam of Eugene Wigner and Hiroomi Umezawa.


title:
Nuclear Responses to Electro-Weak Probes and In-Medium Chiral
  Perturbation Theory

abstract:
  We discuss two topics concerning the application of chiral perturbation
theory to nuclear physics: (1) the latest developments in the study of possible
kaon condensation in dense baryonic systems; (2) nuclear responses to
electro-weak probes.


title:
Analysis of the (N,xN') reactions by quantum molecular dynamics plus
  statistical decay model

abstract:
  We propose a model based on quantum molecular dynamics (QMD) incorporated
with statistical decay model (SDM) to describe various nuclear reactions in an
unified way. In this first part of the work, the basic ingredients of the model
are defined and the model is applied systematically to the nucleon($N$)-induced
reactions. It has been found that our model can give a remarkable agreement in
the energy-angle double differential cross sections of $(N,xN')$ type reactions
for incident energies from 100 MeV to 3 GeV with a fixed parameter set. An
unified description of the major three reaction mechanisms of $(N,xN')$
reactions, i.e. compound, pre-equilibrium and spallation processes, is given
with our model.


title: The reaction $pp \to pp\pi^0$ near threshold

abstract:
  We perform a momentum-space calculation of the reaction $pp \rightarrow pp\pi
^0$ near threshold. Direct production and pion rescattering are taken into
account. For the latter a T-matrix obtained from a microscopic model of the
$\pi N$ interaction is employed. The effects of some approximations commonly
used in studies of $ pp \rightarrow pp\pi ^0$ \ are discussed. We find that
those approximations overestimate the cross section and also modify its energy
dependence. We obtain a significant contribution from rescattering, but not
nearly enough to describe the data.


title: Phenomenological Three-Cluster Model of 6He

abstract:
  By using the method of hyperspherical functions within the appropriate for
this method $K_{\min}$ approximation, the simple three-cluster model for
description of the ground state and the continuous spectrum states of \6He is
developed. It is shown that many properties of \6He (its large rms radius and
large values of the matrix elements of electromagnetic transitions from the
ground state into the continuous spectrum) follow from the fact that the
potential energy of \6He system decreases very slowly (as $\rho^{-3}$) and the
binding energy is small.


title: Heavy Ion Collisions and the Density Dependence of the Local Mean Field

abstract:
  We study the effect of the density dependence of the scalar and the vector
part of the nucleonic self-energy in Relativistic Quantum Molecular Dynamics
(RQMD) on observables like the transversal flow and the rapidity distribution.
The stability of nuclei in RQMD is greatly improved if the density dependence
is included in the self-energies compared to a calculation assuming always
saturation density of nuclear matter. Different approaches are studied: The
main results are calculated with self-energies extracted from a
Dirac-Br\"uckner-Hartree-Fock G-matrix of a one boson exchange model, i.e. the
Bonn potential. These results are compared with those obtained by a
generalization of static Skyrme force, with calculations in the simple linear
Walecka model and results of the Br\"uckner-Hartree-Fock G-matrix of the Reid
soft core potential. The transversal flow is very sensitive to these different
approaches. A comparison with the data is given.


title:
The hole spectral function and the relationship between overlap
  functions, natural orbitals and the one-body density matrix in nuclei

abstract:
  A method to calculate the hole spectral function in the discrete part of the
spectrum is suggested within the natural orbital representation of the one-body
density matrix of $A$-nucleon system using its relationship with the overlap
functions of the eigenstates in the $(A-1)$-nucleon system.


title: Neutrinos from Protoneutron Stars: A Probe of Hot and Dense matter

abstract:
  Neutrino processes in dense matter play a key role in the dynamics,
deleptonization and early cooling of hot protoneutron stars formed in the
gravitational collapse of massive stars. Here we calculate neutrino mean free
paths from neutrino-hyperon interactions in dense matter containing hyperons.
Significant contributions to the neutrino opacity arise from scattering and
absorption reactions involving the sigma minus particle. The estimates given
here emphasise the need for (a) opacities which incoparate many-body effects in
a multi-component mixture, and (b) new calculations of thermal and leptonic
evolution of protoneutron stars with neutrino transport and equations of state
with strangeness-rich matter.


title:
Inhomogeneous Nucleation of Quark-Gluon Plasma in High Energy Nuclear
  Collisions

abstract:
  We estimate the probability that a hard nucleon-nucleon collision is able to
nucleate a seed of quark--gluon plasma in the surrounding hot and dense
hadronic matter formed during a central collision of two large nuclei at AGS
energies. The probability of producing at least one such seed is on the order
of 1-100\%. We investigate the influence of quark--gluon plasma formation on
the observed multiplicity distribution and find that it may lead to noticable
structure in the form of a bump or shoulder.


title: The d'-Dibaryon in the Nonrelativistic Quark Model

abstract:
  The narrow peak recently found in various pionic double charge exchange (DCX)
cross sections can be explained by the assumption of a universal resonance at
2065 MeV, called d'. We calculate the mass of a six-quark system with J^P=0^-,
T=0 quantum numbers employing a cluster model and a shell model basis to
diagonalize the nonrelativistic quark model Hamiltonian.


title: Sum Rules for B(M1,0+ -> 1+) Strength in IBM-3 and IBM-4

abstract:
  Sum rules for $B(M1,0^+_1\rightarrow1^+_i)$ strength are derived for
even-even nuclei in the isospin-invariant forms of the IBM, IBM-3 and IBM-4, in
the cases where the respective natural internal symmetries, isospin $U$(3) and
$U(6)\supset SU$(4), are conserved. Subsequently, the total strength is
resolved into its component partial sums to the allowed isospins (and $SU(4)$
representations in IBM-4). In cases where the usual IBM dynamical symmetries
are also valid, a complete description of all $B(M1,0^+_1\rightarrow1^+_i)$ is
given. In contrast to IBM-2, there is fragmentation of the strength even in the
dynamical symmetry cases, for $T\neq 0$, over two states in IBM-3, and over
three states in IBM-4. The presence of $pn$ bosons in the ground state of the
extended versions reduces the expected strength from that for IBM-2, allowing
in principle the possibility of using $B(M1)$ data for a given nucleus to infer
which version is the most appropriate.


title:
sd-Shell Study with a Multi-Configuration Mixing Approach designed for
  Large Scale Nuclear Structure Calculations

abstract:
  A systematic numerical investigation of a recently developed nuclear
structure approach is presented which diagonalizes the Hamiltonian in the space
of the symmetry-projected Hartree-Fock-Bogoliubov (HFB) vacuum and
symmetry-projected quasiparticle excitations with respect to it. The underlying
HFB transformation, which is assumed to be time-reversal and axially symmetric,
is determined by variation after the projection. The model allows the use of
large basis systems. It has been applied to the calculation of energy spectra
of several even-even, odd-odd and odd mass nuclei in the sd shell with mass
numbers reaching from A=20 to 30. The Chung-Wildenthal interaction has been
used. Good agreement with the exact shell model diagonalization and a
considerable improvement on a previous approach, where the HFB transformation
was significantly more restricted, is obtained.


title: Parity violating pion electroproduction off the nucleon

abstract:
  Parity violating (PV) contributions due to interference between $\gamma$ and
$Z^0$ exchange are calculated for pion electroproduction off the nucleon. A
phenomenological model with effective Lagrangians is used to determine the
resulting asymmetry for the energy region between threshold and $\Delta(1232)$
resonance. The $\Delta$ resonance is treated as a Rarita-Schwinger field with
phenomenological $N \Delta$ transition currents. The background contributions
are given by the usual Born terms using the pseudovector $\pi N$ Lagrangian.
Numerical results for the asymmetry are presented.


title: Multifragmentation in alpha(5GeV/u) + Au Reactions

abstract:
  We simulate the fragmentation processes in the \alAu collisions at the
bombarding energy 5 GeV/u using the simplified RQMD approach. The statistical
decay calculation is connected to obtain the final state. >From the simulation
we find that the residual nucleus created by this collision has a annular
eclipse shape, and then expands more strongly to the transverse direction than
to the beam-direction. Then the angular-distribution of the intermediate mass
fragments has a sideward peak; this result explains the experimental result.


title: Distillation of Strangelets for low initial mu/T

abstract:
  We calculate the evolution of quark-gluon-plasma droplets during the
hadronization in a thermodynamical model. It is speculated that cooling as well
as strangeness enrichment allow for the formation of strangelets even at very
high initial entropy per baryon $S/A^{\rm init}\approx 500$ and low initial
baryon numbers of $A_{\rm B}^{\rm init}\approx 30$. It is shown that the
droplet with vanishing initial chemical potential of strange quarks and a very
moderate chemical potential of up/down quarks immediately charges up with
strangeness. Baryon densities of $\approx 2\rho_0$ and strange chemical
potentials of $\mu_s>350$~MeV are reached if strangelets are stable. The
importance of net--baryon and net--strangeness fluctuations for the possible
strangelet formation at RHIC and LHC is emphasized.


title: Fusion reactions in molecules via nuclear threshold resonances

abstract:
  It is widely accepted that in molecular systems the nuclear interaction plays
a negligible role, because of the strong Coulomb repulsion of the nuclei at
small distances. We are going to show that this is not always true. The
existence of an extended nuclear resonance may lead to considerably enhanced
nuclear reaction rates in appropriately prepared molecules. Especially we point
out that p+p+ ^{16}O, i.e., the constituents of water, can form a ^{18}Ne(1^-)
threshold resonance which decays under energy release into ^{17}F and a proton.


title: Direct radiative capture of p-wave neutrons

abstract:
  The neutron direct radiative capture (DRC) process is investigated,
highlighting the role of incident p-wave neutrons. A set of calculations is
shown for the 12-C(n,gamma) process at incoming neutron energies up to 500 keV,
a crucial region for astrophysics. The cross section for neutron capture
leading to loosely bound s, p and d orbits of 13-C is well reproduced by the
DRC model demonstrating the feasibility of using this reaction channel to study
the properties of nuclear wave functions on and outside the nuclear surface. A
sensitivity analysis of the results on the neutron-nucleus interaction is
performed for incident s- as well as p-waves. It turned out that the DRC cross
section for p-wave neutrons is insensitive to this interaction, contrary to the
case of incident s-wave neutrons.
  PACS number(s): 25.40Lw,21.10Gv,23.40.Hc


title: Instabilities in Nuclei

abstract:
  The evolution of dynamical perturbations is examined in nuclear
multifragmentation in the frame of Vlasov equation. Both plane wave and bubble
type of perturbations are investigated in the presence of surface (Yukawa)
forces. An energy condition is given for the allowed type of instabilities and
the time scale of the exponential growth of the instabilities is calculated.
The results are compared to the mechanical spinodal region predictions. PACS:
25.70 Mn


title:
Thermal and Hadrochemical Equilibration in Nucleus-Nucleus Collisions at
  the SPS

abstract:
  The currently available set of hadron abundances at the SPS for central
S+Au(W,Pb) collisions is compared to predictions from a scenario assuming local
thermal and hadrochemical equilibrium. The data are consistent with a
freeze-out temperature T = 160-170 MeV. Spectra are consistent with this
temperature range and a moderate transverse expansion. The freeze-out points at
the AGS and SPS are found to be close to the phase boundary between a hadron
gas and an ideal quark-gluon phase.


title:
$\pi NN$ and $\pi N\Delta$ formfactors determined from a microscopic
  model for $\pi N$ scattering

abstract:
  We determine the $\pi NN$ and $\pi N\Delta$ formfactors from the $P_{11}$
resp. $P_{33}$ partial wave of $\pi N$ scattering by dressing corresponding
bare vertices with the help of $\pi N$ non--pole contributions. The underlying
model is based on meson exchange, and involves nucleon and delta--isobar pole
and crossed--pole terms together with correlated $\pi\pi$--exchange in the
$J^P=0^+$ ($\sigma$) and $1^-$ ($\rho$) channel. The results are very similar
for $\pi NN$ and $\pi N\Delta$ and can be roughly parametrized by a monopole
with cutoff mass $>$ 500 MeV, with some variation due to model dependencies.
Thus the formfactors are much less soft than derived before for the $\pi NN$
case by Saito and Afnan using the same procedure but different $\pi N$
interaction models.


title: Correlated $\bbox{\pi \rho}$ Exchange in the $\bbox{NN}$ Interaction

abstract:
  We evaluate the contribution to the nucleon-nucleon interaction due to
correlated $\pi\rho$ exchange in the $\pi$, $\omega$, and $A_1$/$H_1$ channels
by means of dispersion-theoretic methods based on a realistic meson exchange
model for the interaction between $\pi$ and $\rho$ mesons. These processes have
substantial effects: In the pionic channel it counterbalances the suppression
generated by a soft $\pi NN$ form factor of monopole type with a cutoff mass of
about 1 GeV; in the $\omega$-channel it provides nearly half of the empirical
repulsion, leaving little room for explicit quark-gluon effects.


title:
Precise solution of few-body problems with stochastic variational method
  on correlated Gaussian basis

abstract:
  Precise variational solutions are given for problems involving diverse
fermionic and bosonic $N=2-7$-body systems. The trial wave functions are chosen
to be combinations of correlated Gaussians, which are constructed from products
of the single-particle Gaussian wave packets through an integral
transformation, thereby facilitating fully analytical calculations of the
matrix elements. The nonlinear parameters of the trial function are chosen by a
stochastic technique. The method has proved very efficient, virtually exact,
and it seems feasible for any few-body bound-state problems emerging in nuclear
or atomic physics.


title: Weakly-Bound Three-Body Systems with No Bound Subsystems

abstract:
  We investigate the domain of coupling constants which achieve binding for a
3-body system, while none of the 2-body subsystems is bound. We derive some
general properties of the shape of the domain, and rigorous upper bounds on its
size, using a Hall--Post decomposition of the Hamiltonian. Numerical
illustrations are provided in the case of a Yukawa potential, using a simple
variational method.


title:
Improvement of the nucleon emission process and the statistical property
  in molecular dynamics

abstract:
  We propose to introduce a new stochastic process in molecular dynamics in
order to improve the description of the nucleon emission process from a hot
nucleus. We give momentum fluctuations originating from the momentum width of
the nucleon wave packet to the nucleon stochastically when it is being emitted
from the nucleus. We show by calculating the liquid gas phase equilibrium in
the case of antisymmetrized molecular dynamics, that with this improvement, we
can recover the quantum mechanical statistical property of the nucleus for the
particle emission process.


title: Chirally Constraining the $\pi \pi$ Interaction in Nuclear Matter

abstract:
  A general prescription for the construction of $\pi \pi$ interaction
potentials which preserve scattering length constraints from chiral symmetry
when iterated in scattering equations is derived. The prescription involves
only minor modifications of typical meson-exchange models, so that coupling
constants and cut-off masses in the models are not greatly affected.
Calculations of $s$-wave $\pi \pi$ scattering amplitudes in nuclear matter for
two models are compared with those for similar models which violate the chiral
constraint. While the prescription tends to suppress the accumulation of the
near sub-threshold strength of the $\pi \pi$ interaction, an earlier conjecture
that amplitudes which satisfy chiral constraints will not exhibit an
instability towards $\pi \pi~s-$wave pair condensation appears to be incorrect.
At the same time, however, conventional $\pi \pi$ interaction models which fit
scattering data well can readily be adjusted to avoid the instability in
nuclear matter without recourse to exotic mechanisms.


title: Few-Body Descriptions of the piNN System in Three and Four Dimensions

abstract:
  We summarise the recent theoretical progress in few-body descriptions of the
piNN system. Previous descriptions, both three- and four-dimensional, are shown
to possess serious theoretical inconsistencies. We illustrate how
three-dimensional approaches suffer from renormalisation problems, and how
four-dimensional descriptions contain both overcounting and undercounting of
diagrams. We then show how such theoretical problems have been recently
overcome, leading to new practical few-body equations for the piNN system.


title: Multifragmentation calculated with relativistic force

abstract:
  A saturating hamiltonian is presented in a relativistically covariant
formalism. The interaction is described by scalar and vector mesons, with
coupling strengths adjusted to the nuclear matter. No explicit density depe
ndence is assumed. The hamiltonian is applied in a QMD calculation to determine
the fragment distribution in O + Br collision at different energies (50 -- 200
MeV/u) to test the applicability of the model at low energies. The results are
compared with experiment and with previous non-relativistic calculations.
  PACS: 25.70Mn, 25.75.+r


title:
Do final state interactions obscure short range correlation effects in
  quasielastic $A(e,e'p)$ scattering?

abstract:
  Are short range correlations in the ground state of the target nucleus
(initial state correlations ISC)observable inexperiments on quasielastic
$A(e,e'p)$ scattering at large missing momentum $p_{m}$? Will the missing
momentum spectrum observed at CEBAF be overwhelmed by final state interactions
of the struck proton? Taking the $^{4}He$ nucleus with a realistic model wave
function for a testing ground, we present a full calculation of the missing
momentum distribution in inclusive $^{4}He(e,e'p)$ scattering. We find a
complex interplay and strong quantum-mechanical interference of FSI and ISC
contributions to scattering at large $p_{m}$, with drastic change of the
interference pattern from the (anti)parallel to transverse kinematics. We show
that in all the kinematical conditions, for missing momenta $p_{m}\gsim
1$\,fm$^{-1}$, quasielastic scattering is dominated by FSI effects and the
sensitivity to details of the nuclear ground state is lost. The origin of the
FSI dominance is well understood and can be traced back to the anisotropic
behaviour of FSI which is long ranged in the longitudinal direction and short
ranged in the transverse direction in the opposite to the short ranged ground
state correlations.


title: Symmetry Problems in Low Energy Physics

abstract:
  Some recent experimental and theoretical work on 1) charge symmetry-breaking,
2) parity non-conservation, and 3) searches for breaking of time reversal
invariance are reviewed. The examples illustrate the uses of symmetry to learn
about underlying dynamics and/or structure.


title: Does the quark cluster model predict any isospin two dibaryon resonance?

abstract:
  We analyze the possible existence of a resonance in the $J^P=0^-$ channel
with isospin two by means of nucleon-$\Delta$ interactions based on the
constituent quark model. We solve the bound state and the scattering problem
using two different potentials, a local and a non-local one. The non-local
potential results to be the more attractive, although not enough to generate
the experimentally predicted resonance.


title: Description of superdeformed nuclei in the interacting boson model

abstract:
  The interacting boson model is extended to describe the spectroscopy of
superdeformed bands. Microscopic structure of the model in the second minimum
is discussed and superdeformed bosons are introduced as the new building
blocks. Solutions of a quadrupole Hamiltonian are implemented through the $1/N$
expansion method. Effects of the quadrupole parameters on dynamic moment of
inertia and electric quadrupole transition rates are discussed and the results
are used in a description of superdeformed bands in the Hg-Pb and Gd-Dy
regions.


title:
Nuclear Structure Corrections to Deuterium Hyperfine Structure and Lamb
  Shift

abstract:
  The low-energy theorem for the forward Compton scattering is generalized to
the case of an arbitrary target spin. The generalization is used to calculate
the corresponding contribution to the deuterium hyperfine structure. The
nuclear-structure corrections are quite essential in this case due to the
deuteron large size. Corrections of this type calculated here remove the
discrepancy between the theoretical and experimental values of the deuterium
hyperfine splitting. Explicit analytical result is obtained also for the
deuteron polarizability contribution to the Lamb shift.


title:
Universal pattern in (e,e'p) at large missing momenta: quasi-deuteron or
  diffractive final state interactions?

abstract:
  The intrinsic single particle momentum distributions in nuclei are supposed
to show a universal behavior at large momenta, dominated by short-range
correlated pairs, or quasi-deuterons. We discuss whether the quasi-deuteron
universality survives the final state interaction effects, which are present in
the missing momentum spectra measured in $A(e,e'p)$ experiments at GeV
energies. We demonstrate that in the observed missing momentum spectra an
approximate universality is present, but originating from the universal pattern
of diffractive final state interactions of the struck proton independent of the
target nucleus.


title:
Isospin-Violating Meson-Nucleon Vertices as an Alternate Mechanism of
  Charge-Symmetry Breaking

abstract:
  We compute isospin-violating meson-nucleon coupling constants and their
consequent charge-symmetry-breaking nucleon-nucleon potentials. The couplings
result from evaluating matrix elements of quark currents between nucleon states
in a nonrelativistic constituent quark model; the isospin violations arise from
the difference in the up and down constituent quark masses. We find, in
particular, that isospin violation in the omega-meson--nucleon vertex dominates
the class IV CSB potential obtained from these considerations. We evaluate the
resulting spin-singlet--triplet mixing angles, the quantities germane to the
difference of neutron and proton analyzing powers measured in elastic
$\vec{n}-\vec{p}$ scattering, and find them commensurate to those computed
originally using the on-shell value of the $\rho$-$\omega$ mixing amplitude.
The use of the on-shell $\rho$-$\omega$ mixing amplitude at $q^2=0$ has been
called into question; rather, the amplitude is zero in a wide class of models.
Our model possesses no contribution from $\rho$-$\omega$ mixing at $q^2=0$, and
we find that omega-meson exchange suffices to explain the measured $n-p$
analyzing power difference~at~183 MeV.


title:
Treatment of Pionic Modes at the Nuclear Surface for Transport
  Descriptions

abstract:
  Dispersion relations and amplitudes of collective pionic modes are derived in
a pi + nucleon-hole + delta-hole model for use in transport descriptions by
means of a local density approximation. It is discussed how pionic modes can be
converted to real particles when penetrating the nuclear surface and how
earlier treatments can be improved. When the surface is stationary only free
pions emerge. The time-dependent situation is also addressed, as is the
conversion of non-physical (i.e. unperturbed delta-hole) modes to real
particles when the nuclear density vanishes. A simplified one-dimensional
scenario is used to investigate the reflection and transmission of pionic modes
at the nuclear surface. It is found that reflection of pionic modes is rather
unlikely, but the process can be incorporated into transport descriptions by
the use of approximate local transmission coefficients.


title: $g_{K N \Lambda}$ and $g_{K N \Sigma}$ from QCD sum rules

abstract:
  $g_{K N \Lambda}$ and $g_{K N \Sigma}$ are calculated using a QCD sum rule
motivated method used by Reinders, Rubinstein and Yazaki to extract Hadron
couplings to goldstone bosons. The SU(3) symmetry breaking effects are taken
into account by including the contributions from the strange quark mass and
assuming different values for the strange and the up down quark condensates. We
find $g_{K N \Lambda}/\sqrt{4 \pi} = - 1.96 $ and $g_{K N \Sigma}/\sqrt{4 \pi}
= 0.33 $


title: Exact methods for Campi plots

abstract:
  We introduce for canonical fragmention models an exact method for computing
expectation values which exclude the largest cluster. This method allows for
the computation of the reduced multiplicity and other quantities of interest
introduced by Campi, and a comparison shows that the percolation model and a
recent canonical model differ mostly only in small respects in these ensemble
averages.


title: Collisions of Deformed Nuclei and Superheavy-Element Production

abstract:
  A detailed understanding of complete fusion cross sections in heavy-ion
collisions requires a consideration of the effects of the deformation of the
projectile and target. Our aim here is to show that deformation and orientation
of the colliding nuclei have a very significant effect on the fusion-barrier
height and on the compactness of the touching configuration. To facilitate
discussions of fusion configurations of deformed nuclei, we develop a
classification scheme and introduce a notation convention for these
configurations. We discuss particular deformations and orientations that lead
to compact touching configurations and to fusion-barrier heights that
correspond to fairly low excitation energies of the compound systems. Such
configurations should be the most favorable for producing superheavy elements.
We analyse a few projectile-target combinations whose deformations allow
favorable entrance-channel configurations and whose proton and neutron numbers
lead to compound systems in a part of the superheavy region where alpha
half-lives are calculated to be observable, that is, longer than 1 microsecond.


title: Transverse Momentum Dependence of Hanbury-Brown/Twiss Correlation Radii

abstract:
  The transverse momentum dependence of Hanbury-Brown/Twiss (HBT)
interferometry radii for 2-body correlation functions provides experimental
access to the collective dynamics in heavy-ion collisions. We present an
analytical approximation scheme for these HBT radii which combines the recently
derived model-independent expressions with an approximate determination of the
saddle point of the emission function. The method is illustrated for a
longitudinally boost-invariant hydrodynamical model of a heavy ion collision
with freeze-out on a sharp hypersurface. The analytical approximation converges
rapidly to the width of the numerically computed correlation function and
reproduces correctly its exact transverse momentum dependence. However, higher
order corrections within our approximation scheme are essential, and the
previously published lowest order results with simple $m_{\perp}$ scaling
behaviour are quantitatively and qualitatively unreliable.


title: Quark Model Calculations Of Symmetry Breaking in Parton Distributions

abstract:
  Using a quark model, we calculate symmetry breaking effects in the valence
quark distributions of the nucleon. In particular, we examine the breaking of
the quark model SU(4) symmetry by color magnetic effects, and find that color
magnetism provides an explanation for deviation of the ratio $d_V(x)/u_V(x)$
from $1/2$. Additionally, we calculate the effect of charge symmetry breaking
in the valence quark distributions of the proton and neutron and find, in
contrast to other authors, that the effect is too small to be seen
experimentally.


title:
On the relationship of the scaled phase space and Skyrme-coherent state
  treatments of proton antiproton annihilation at rest

abstract:
  We discuss pion multiplicities and single pion momentum spectra from proton
antiproton annihilation at rest. Both the scaled phase space model and the
Skyrme-coherent state approach describe these observables well. In the coherent
state approach the puzzling size of the scale parameter relating the phase
space integrals for different multiplicities is replaced by a well defined
weight function. The strength of this function is determined by the intensity
of the classical pion field and its spatial extent is of order 1 fm.


title: Decay Anisotropy of $e^+e^-$ Sources from $pN$ and $pd$ collisions

abstract:
  A full calculation of lepton-pair angular characteristics is carried out for
$e^+e^-$ pairs created in $pp$, $pn$ and $pd$ collisions at intermediate
energies. It is demonstrated that the proposed new observable, the dilepton
decay anisotropy, quite sensitively changes for different sources and may be
useful for their disentangling. The relevance of the dilepton decay anisotropy
is shown in the context of a puzzling energy behavior for the ratio of the
lepton yield from $pd$ to $pp$ reactions as observed at the BEVALAC.


title: K^+ production in p-C-collisions at a beam energy 1.2 GeV

abstract:
  The isobar model and the resonance model are applied for the first analysis
of the subthreshold $K^+$-meson production in proton-carbon collisions, which
was perfomed at GSI at an emission angle of 40 degrees and a bombarding energy
of 1.2 GeV. In this study, we focus on the role of the secondary processes $\pi
N \to K^+ Y$ in normal nuclear matter density. It turns out that the present
approach can reproduce very well both the $\pi^+$- and $K^+$- meson spectra. It
is also demonstrated that the different kinds of descriptions for the $\pi N
\to K^+ \Lambda$ reactions substantially differentiate the calculated results
for the $p A \to K^+ X$ differential cross sections.


title: Spinodal instabilities within BUU approach

abstract:
  Using a recently developed method for the inclusion of fluctuation in the BUU
dynamics, we study the self-consistent propagation of inherent thermal noise of
unstable nuclear matter. The large time behaviour of the evolving system
exhibits synergism between fluctuation and non-linearities in a universal
manner which manifest in the appearance of macroscopic structure in the average
description.


title: The Changes in Properties of Hadrons in Nuclei and Nuclear Matter

abstract:
  The changes of hadron properties in dense and/or hot matter are discussed in
terms of effective chiral Lagrangians with the parameters of the theory scaled
in a simple way. The phenomenologically successful Walecka model is identified
as a mean field chiral Lagrangian with the scaled parameters. Kaon condensation
and chiral restoration transitions can be described within the same mean field
framework.


title: Angular Correlations in Internal Pair Conversion of Aligned Heavy Nuclei

abstract:
  We calculate the spatial correlation of electrons and positrons emitted by
internal pair conversion of Coulomb excited nuclei in heavy ion collisions. The
alignment or polarization of the nucleus results in an anisotropic emission of
the electron-positron pairs which is closely related to the anisotropic
emission of $\gamma$-rays. However, the angular correlation in the case of
internal pair conversion exhibits diverse patterns. This might be relevant when
investigating atomic processes in heavy-ion collisions performed at the Coulomb
barrier.


title:
The Nucleon-Nucleon Interaction in the Chromo-Dielectric Soliton Model:
  Dynamics

abstract:
  The present work is an extension of a previous study of the nucleon-nucleon
interaction based on the chromo-dielectric soliton model. The former approach
was static, leading to an adiabatic potential. Here we perform a dynamical
study in the framework of the Generator Coordinate Method. In practice, we
derive an approximate Hill-Wheeler differential equation and obtain a local
nucleon-nucleon potential as a function of a mean generator coordinate. This
coordinate is related to an effective separation distance between the two
nucleons by a Fujiwara transformation. This latter relationship is especially
useful in studying the quark substructure of light nuclei. We investigate the
explicit contribution of the one-gluon exchange part of the six-quark
Hamiltonian to the nucleon-nucleon potential, and we find that the dynamics are
responsible for a significant part of the short-range N-N repulsion.


title: Quasi-Elastic Scattering in the Inclusive ($^3$He, t) Reaction

abstract:
  The triton energy spectra of the charge-exchange $^{12}$C($^3$He,t) reaction
at 2 GeV beam energy are analyzed in the quasi-elastic nucleon knock-out
region. Considering that this region is mainly populated by the charge-exchange
of a proton in $^3$He with a neutron in the target nucleus and the final proton
going in the continuum, the cross-sections are written in the distorted-wave
impulse approximation. The t-matrix for the elementary exchange process is
constructed in the DWBA, using one pion- plus rho-exchange potential for the
spin-isospin nucleon- nucleon potential. This t-matrix reproduces the
experimental data on the elementary pn $\rightarrow $np process. The calculated
cross-sections for the $^{12}$C($^3$He,t) reaction at $2^o$ to $7^o$ triton
emission angle are compared with the corresponding experimental data, and are
found in reasonable overall accord.


title:
Nuclear muon capture by 3He: meson exchange currents for the triton
  channel

abstract:
  Exchange current corrections are calculated using currents found from the
hard-pion model and AV14+3BF wavefunctions. Results are given for the rate and
spin observables. Their sensitivity to g_P, the nucleon pseudoscalar form
factor, is reported.


title:
Extension of Quantum Molecular Dynamics and its Application to Heavy-Ion
  Collisions

abstract:
  In order to treat low-energy heavy-ion reactions, we make an extension of
quantum molecular dynamics method. A phenomenological Pauli potential is
introduced into effective interactions to approximate the nature of the Fermion
many-body system. We treat the widths of nucleon wave-packets as time-dependent
dynamical variables. With these modifications, our model can well describe the
ground-state properties in wide mass range. Improvements due to the extension
are also obtained in the nucleus-nucleus collision calculations.


title:
Radiative $\pi \rho$ and $\pi \omega$ transition form factors in a
  light-front constituent quark model

abstract:
  The form factors of the $\pi \rho$ and $\pi \omega$ radiative transitions are
evaluated within a light-front constituent quark model, using for the first
time the eigenfunctions of a light-front mass operator reproducing the meson
mass spectrum and including phenomenological Dirac and Pauli quark form factors
in the one-body electromagnetic current operator. The sensitivity of the
transition form factors both to the meson wave functions and to the constituent
quark form factors is illustrated. It is shown that the measurement of the $\pi
\rho$ and $\pi \omega$ radiative transitions could help in discriminating among
various models of the meson structure.


title: Updated resonance photo-decay amplitudes to 2 GeV

abstract:
  We present the results of an energy-dependent and set of single-energy
partial-wave analyses of single-pion photoproduction data. These analyses
extend from threshold to 2 GeV in the laboratory photon energy, and update our
previous analyses to 1.8 GeV. Photo-decay amplitudes are extracted for the
baryon resonances within this energy range. We consider two photoproduction sum
rules and the contributions of two additional resonance candidates found in our
most recent analysis of $\pi N$ elastic scattering data. Comparisons are made
with previous analyses.


title:
Comparison of the Effective Interaction to Various Orders in Different
  Mass Regions

abstract:
  The convergence of the perturbation expansion for the effective interaction
to be used in shell-model calculations is investigated as function of the mass
number $A$, from $A=4$ to $A=208$. As the mass number increases, there are more
intermediate states to sum over in each higher-order diagram which contributes
to the effective interaction. Together with the fact that the energy
denominators in each diagram are smaller for larger mass numbers, these two
effects could largely enhance higher-order contributions to the effective
interaction, thereby deteriorating the order-by-order convergence of the
effective interaction. This effect is counterbalanced by the short range of the
nucleon-nucleon interaction, which implies that its matrix elements are weaker
for valence single-particle states in ``large'' nuclei with large mass number
as compared to those in light nuclei. These effects are examined by comparing
various mean values of the matrix elements. It turns out that the contributions
from higher-order terms remain fairly stable as the mass number increases from
$A=4$ to $A=208$. The implications for nuclear structure calculations are
discussed.


title:
Flavor Production in Pb(160AGeV) on Pb Collisions: Effect of Color Ropes
  and Hadronic Rescattering

abstract:
  Collective interactions in the preequilibrium quark matter and hadronic
resonance gas stage of ultrarelativistic nucleus-nucleus collisions are studied
in the framework of the the transport theoretical approach RQMD. The paper
reviews string fusion into color ropes and hadronic rescattering which serve as
models for these interactions. Hadron production in central Pb(160AGeV) on Pb
collisions has been calculated. The changes of the final flavor composition are
more pronounced than in previous RQMD studies of light ion induced reactions at
200AGeV. The ratio of created quark pairs $s\bar{s}$/($u\bar{u}$+$d\bar{d}$) is
enhanced by a factor of 2.4 in comparison to $pp$ results. Color rope formation
increases the initially produced antibaryons to 3 times the value in the `NN
mode', but only one quarter of the produced antibaryons survives because of
subsequent strong absorption. The differences in the final particle composition
for Pb on Pb collisions compared to S induced reactions are attributed to the
hadronic resonance gas stage which is baryon-richer and lasts longer.


title: Strangeness Production in Neutron Stars

abstract:
  Production of strange quarks in neutron stars is investigated in this work.
Three cases, one in which the energy and neutrinos produced in the strangeness
production reactions are retained in the reaction region, second in which the
neutrinos are allowed to escape the reaction region but the energy is retained
and the third in which both the energy and neutrinos escape the reaction region
are considered. It is shown that the nonleptonic weak process dominates strange
quark production while semileptonic weak processes, which produce neutrinos,
lead to the cooling if the neutrinos escape the reaction region. It is found
that the time required for the saturation of the strangeness fraction is
between $10^{-7}$ and $10^{-5}$ sec, with the shorter time corresponding to the
first two cases. About 0.2 neutrinos/baryon are emitted during the process in
the first two cases where as the neutrino emission is somewhat suppressed in
the last case. The average energy of the neutrinos produced in all the three
cases is found to be several hundred $MeV$. We also find that a large amount of
energy is released during the strangeness production in the first two cases and
this leads to the heating of the reaction region. Implications of the neutrino
production are investigated.


title:
A Consistent Study of the the Low Energy Baryon Spectrum and the
  Nucleon-Nucleon Interaction within the Chiral Quark Model

abstract:
  By solving the Schr\"{o}dinger equation for the three-quark system in the
hyperspherical harmonic approach, we have studied the low energy part of the
nucleon and $\Delta$ spectra using a quark-quark interaction which reproduces
the nucleon-nucleon phenomenology. The quark-quark hamiltonian considered
includes, besides the usual one-gluon exchange, pion and sigma exchanges
generated by the chiral symmetry breaking. The baryonic spectrum obtained is
reasonable and the resulting wave function gives consistency to the ansatz used
in the two baryon system.


title: Higher excitations of $\omega$ and $\phi$ in dilepton spectra

abstract:
  We consider lepton pair production via two-hadron annihilation through
various isoscalar vector mesons within hot, baryon-free matter. This is
tantamount to constructing effective form factors which we model using a
vector-meson-dominance approach and compare with experiment. In particular, we
consider the reactions $\pi\rho\to e^+e^-$ and $\bar K K^{*}(892)$ + c.c. $\to
e^+e^-$. We find that $\omega(1390)$ and $\phi(1680)$ are visible in the mass
spectrum for the thermal production rate above the $\pi^{+}\pi^{-} \to e^+e^-$
tail and even above the $\pi a_{1}\to e^+e^-$ results---both of which were
considered important in their respective mass regions.


title: Neutrino Emissivity of Dense Stars

abstract:
  The neutrino emissivity of compact stars is investigated in this work. We
consider stars consisting of nuclear as well as quark matter for this purpose.
Different models are used to calculate the composition of nuclear and quark
matter and the neutrino emissivity. Depending on the model under consideration,
the neutrino emissivity of nuclear as well as quark matter varies over a wide
range. We find that for nuclear matter, the direct URCA processes are allowed
for most of the relativistic models without and with strange baryons, whereas
for the nonrelativistic models this shows a strong dependence on the type of
nuclear interaction employed. When the direct URCA processes are allowed, the
neutrino emissivity of hadronic matter is larger than that of the quark matter
by several orders of magnitude. We also find that the neutrino emissivity
departs from $T^6$ behavior when the temperature is larger than the difference
in the Fermi momenta of the particles, participating in the neutrino-producing
reactions.


title: Quark Cluster Model Study of Isospin-Two Dibaryons

abstract:
  Based on a quark cluster model for the non-strange sector that reproduces
reasonably well the nucleon-nucleon system and the excitation of the $\Delta$
isobar, we generate a nucleon-$\Delta$ interaction and present the predictions
for the several isospin two channels. The only attractive channels are $0^+$
and $0^-$, but not attractive enough to generate a resonance. If a resonance is
artificially generated and is required to have the observed experimental mass,
then our model predicts a width that agrees with the experimental result.


title: Causality Violations in Cascade Models of Nuclear Collisions

abstract:
  Transport models have successfully described many aspects of intermediate
energy heavy-ion collision dynamics. As the energies increase in these models
to the ultrarelativistic regime, Lorentz covariance and causality are not
strictly respected. The standard argument is that such effects are not
important to final results; but they have not been seriously considered at high
energies. We point out how and why these happen, how serious of a problem they
may be and suggest ways of reducing or eliminating the undesirable effects.


title:
Multifragmentation through Exotic Shape Nuclei in alpha(5GeV/u) + Au
  Reactions

abstract:
  We simulate the fragmentation processes in the {$\alpha$~$+$~Au~} collisions
at a bombarding energy of 5 GeV/u using the simplified RQMD approach plus the
statistical decay model. We find from the simulation that the
angular-distribution of the intermediate mass fragments has a sideward peak,
more strongly in the transverse direction than in the beam-direction, when the
intermediate nucleus formed by the dynamical process has an annular eclipse
shape, which explains the experimental results.


title:
Effect of $NN$-correlations on predictions of nuclear transparencies for
  protons, knocked-out in high $Q^2\,(e,e'p)$ reactions

abstract:
  We study the transparency $\cal T$ of nuclei for nucleons knocked-out in
high-energy semi-inclusive $(e,e'p)$ reactions, using an improved theoretical
input, discussed by Nikolaev et al. We establish that neglect of
$NN$-correlations between the knocked-out and core nucleons reduces nuclear
transparencies by $\approx 15 \%$ for light, to $\approx 10\%$ for heavy
nuclei. About the same is predicted for transparencies, integrated over the
transverse or longitudinal momentum of the outgoing proton. Hadron dynamics
predicts a roughly constant $\cal T$ beyond $Q^2\approx $2 GeV$^2$, whereas for
all targets the largest measured data point $Q^2$=6.7 GeV$^2$ appears to lie
above that plateau. Large error bars on those data-points preclude a conclusion
regarding the onset of colour transparency.


title: Asymmetric nuclear matter and neutron star properties

abstract:
  In this work we calculate the total mass, radius, moment of inertia, and
surface gravitational redshift for neutron stars using various equations of
state (EOS). Modern meson-exchange potential models are used to evaluate the
$G$-matrix for asymmetric nuclear matter. We calculate both a non-relativistic
and a relativistic EOS. Of importance here is the fact that relativistic
Brueckner-Hartree-Fock calculations for symmetric nuclear matter fit the
empirical data, which are not reproduced by non-relativistic calculations.
Relativistic effects are known to be important at high densities, giving an
increased repulsion. This leads to a stiffer EOS compared to the EOS derived
with a non-relativistic approach. Both the non-relativistic and the
relativistic EOS yield moments of inertia and redshifts in agreement with the
accepted values. The relativistic EOS yields, however, too large mass and
radius. The implications are discussed.


title: Three flavour Quark matter in chiral colour dielectric model

abstract:
  We investigate the properties of quark matter at finite density and
temperature using the nonlinear chiral extension of Colour Dielectric Model
(CCM). Assuming that the square of the meson fields devlop non- zero vacuum
expectation value, the thermodynamic potential for interacting three flavour
matter has been calculated. It is found that $<K^2>$ and $<\eta^2>$ remain zero
in the medium whereas $<\pi^2>$ changes in the medium. As a result, $u$ and $d$
quark masses decrease monotonically as the temperature and density of the quark
matter is increased.In the present model, the deconfinement density and
temperature is found to be lower compared to lattice results. We also study the
behaviour of pressure and energy density above critical temperature.


title: Form factors in an algebraic model of the nucleon

abstract:
  We study the electromagnetic form factors of the nucleon in a collective
model of baryons. In an algebraic approach to hadron structure, we derive
closed expressions for both elastic and transition form factors, and
consequently for the helicity amplitudes that can be measured in electro- and
photoproduction.


title: Role of Hyperon Negative Energy Sea in Nuclear Matter

abstract:
  We have examined the contribution of the filled negative energy sea of
hyperons to the energy/particle in nuclear matter at the one and two loop
levels. While this has the potential to be significant, we find a strong
cancellation between the one and two loop contributions for our chosen
parameters so that hyperon effects can be justifiably neglected.


title:
Chaos vs. Linear Instability in the Vlasov Equation: A Fractal Analysis
  Characterization

abstract:
  In this work we discuss the most recent results concerning the Vlasov
dynamics inside the spinodal region. The chaotic behaviour which follows an
initial regular evolution is characterized through the calculation of the
fractal dimension of the distribution of the final modes excited. The ambiguous
role of the largest Lyapunov exponent for unstable systems is also critically
reviewed.


title: Statistical Properties of Fermionic Molecular Dynamics

abstract:
  Statistical properties of Fermionic Molecular Dynamics are studied. It is
shown that, although the centroids of the single--particle wave--packets follow
classical trajectories in the case of a harmonic oscillator potential, the
equilibrium properties of the system are the quantum mechanical ones. A system
of weakly interacting fermions as well as of distinguishable particles is found
to be ergodic and the time--averaged occupation probabilities approach the
quantum canonical ones of Fermi--Dirac and Boltzmann statistics, respectively.


title: Polarization observables in vector meson photoproduction

abstract:
  An analysis of all possible polarization observables for the case of vector
meson photoproduction from a nucleon target is presented. The question of which
observables are needed to determine completely the basic photoproduction
amplitudes and the relationships between spin observables are addressed.


title:
Nucleus - Air Interactions for Extensive Air Showers Experiments at
  Ultrahigh Energies

abstract:
  The HIJING and VENUS models of relativistic hadron-nucleus and
nucleus-nucleus collisions are used to study interactions of proton and nuclei
with nitrogen, specific for the extensive air shower developments initiated by
cosmic rays in the atmosphere. The transverse energy,transverse momenta and
secondary particles produced spectra as well as their energy and mass
dependence were investigated in detail. Results are presented with particular
emphasis on the contributions of minijets in HIJING model and validity of
superposition models in this energy range .


title: The Nijmegen Potentials

abstract:
  A review is given of the various Nijmegen potentials. Special attention is
given to some of the newest developments, such as the extended soft-core model,
the high-quality potentials, and the Nijmegen optical potentials for NN.


title: Hbt Analysis of Anisotropic Transverse Flow

abstract:
  The effects of anisotropic transverse collective flow on the HBT correlation
function is studied. There exist three different physics contributions related
to flow which affect the correlation function: anisotropic source shape,
anisotropic space-momentum correlations in pion emission, and the effects
related to the HBT measurement of the size of a moving source in different
reference frames. Resolution of these contributions experimentally can lead to
a detailed understanding of both collective flow in nucleus-nucleus collisions
and the HBT technique itself. A method is presented which permits the
derivation of model independent relations between the radius of a source
measured in a frame in which it is moving and in its rest frame.


title: The role of nuclear form factors in Dark Matter calculations

abstract:
  The momentum transfer dependence of the total cross section for elastic
scattering of cold dark matter candidates, i.e. lightest supermymmetric
particle (LSP), with nuclei is examined. We find that even though the energy
transfer is small ($\le 100 KeV$) the momentum transfer can be quite big for
large mass of the LSP and heavy nuclei. The total cross section can in such
instances be reduced by a factor of about five.


title: Nodal trajectories of spin observables and kaon photoproduction dynamics

abstract:
  Spin observables for the reaction $\gamma p \rightarrow K^+ \Lambda$ are
examined using three recent dynamical models and are compared to the general
features of such observables deduced earlier by Fasano, Tabakin and Saghai.
These general features, such as the energy dependence of spin observables and
the location of nodes in their angle dependence, are realized. Several
instructive surprises, which occur in this comparison to the conjectures of
Fasano et al., are then discussed. The sensitivity of spin observables to
isobar and {\it t-}channel dynamics is analyzed and suggestions for selecting
experiments which provide important dynamical information are presented.


title: Structure of Pairs in Heavy Weakly-Bound Nuclei

abstract:
  We study the structure of nucleon pairs within a simple model consisting of a
square well in three dimensions and a delta-function residual interaction
between two weakly-bound particles at the Fermi surface. We include the
continuum by enclosing the entire system in a large spherical box. To a good
approximation, the continuum can be replaced by a small set of
optimally-determined resonance states, suggesting that in many nuclei far from
stability it may be possible to incorporate continuum effects within
traditional shell-model based approximations.


title:
Soft two-meson-exchange nucleon-nucleon potentials. I. Planar and
  crossed-box diagrams

abstract:
  Pion-meson-exchange nucleon-nucleon potentials are derived for two nucleons
in the intermediate states. The mesons we include are (i) pseudoscalar mesons:
$\pi, \eta, \eta'$; (ii) vector mesons: $\rho, \omega, \phi$; (iii) scalar
mesons: $a_{0}(980), \varepsilon(760), f_{0}(975)$; and (iv) the $J=0$
contribution from the Pomeron. Strong dynamical pair suppression is assumed,
and at the nucleon-nucleon-meson vertices Gaussian form factors are
incorporated into the relativistic two-body framework using a dispersion
representation for the pion- and meson-exchange amplitudes. The Fourier
transformations are performed using factorization techniques for the energy
denominators. The potentials are first calculated in the adiabatic
approximation to all planar and crossed three-dimensional momentum-space
$\pi$-meson diagrams. Next, we calculate the $1/M$ corrections.


title:
The Role of Color Neutrality in Nuclear Physics--Modifications of
  Nucleonic Wave Functions

abstract:
  The influence of the nuclear medium upon the internal structure of a
composite nucleon is examined. The interaction with the medium is assumed to
depend on the relative distances between the quarks in the nucleon consistent
with the notion of color neutrality, and to be proportional to the nucleon
density. In the resulting description the nucleon in matter is a superposition
of the ground state (free nucleon) and radial excitations. The effects of the
nuclear medium on the electromagnetic and weak nucleon form factors, and the
nucleon structure function are computed using a light-front constituent quark
model. Further experimental consequences are examined by considering the
electromagnetic nuclear response functions. The effects of color neutrality
supply small but significant corrections to predictions of observables.


title:
Soft two-meson-exchange nucleon-nucleon potentials. II. One-pair and
  two-pair diagrams

abstract:
  Two-meson-exchange nucleon-nucleon potentials are derived where either one or
both nucleons contains a pair vertex. Physically, the meson-pair vertices are
meant to describe in an effective way (part of) the effects of heavy-meson
exchange and meson-nucleon resonances. {}From the point of view of ``duality,''
these two kinds of contribution are roughly equivalent. The various
possibilities for meson pairs coupling to the nucleon are inspired by the
chiral-invariant phenomenological Lagrangians that have appeared in the
literature. The coupling constants are fixed using the linear $\sigma$ model.
We show that the inclusion of these two-meson exchanges gives a significant
improvement over a potential model including only the standard one-boson
exchanges.


title: The Low-Energy Neutron-Proton Scattering Parameters and the Deuteron

abstract:
  The low-energy parameters describing the np scattering in the 3S1 + 3D1
partial waves, the deuteron parameters, and their relations are discussed.
These parameters can be determined quite accurately in the energy-dependent
Nijmegen partial-wave analyses of the np data and are also given by the
high-quality Nijmegen potentials. The newest values for these parameters are
presented.


title:
Electromagnetic $N - \Delta$ transition form factors in a light-front
  constituent quark model

abstract:
  A parameter-free evaluation of the $N - \Delta$ electromagnetic transition
form factors is carried out in a light-front constituent quark model, based on
$N$ and $\Delta$ eigenstates of a mass operator which reproduces a large set of
hadron energy levels. A one-body electromagnetic current, including the
constituent quark form factors previously determined within the same approach
from nucleon and pion experimental data, is used. Our prediction for the
magnetic transition form factor is compared with the results both of
phenomenological analyses of experimental data for the $\Delta$
electroproduction, and of an analysis which includes the effects of
off-energy-shell $\pi - N$ final state interaction.


title: The role of nucleon structure in finite nuclei

abstract:
  The quark-meson coupling model, based on a mean field description of
non-overlapping nucleon bags bound by the self-consistent exchange of $\sigma$,
$\omega$ and $\rho$ mesons, is extended to investigate the properties of finite
nuclei. Using the Born-Oppenheimer approximation to describe the interacting
quark-meson system, we derive the effective equation of motion for the nucleon,
as well as the self-consistent equations for the meson mean fields. The model
is first applied to nuclear matter, after which we show some initial results
for finite nuclei.


title:
Modern meson--exchange potential and superfluid neutron star crust
  matter

abstract:
  In this work we study properties of neutron star crusts, where matter is
expected to consist of nuclei surrounded by superfluid neutrons and a
homogeneous background of relativistic electrons. The nuclei are disposed in a
Coulomb lattice, and it is believed that the structure of the lattice
influences considerably the specific heat of the neutronic matter inside the
crust of a neutron star. Using a modern meson--exchange potential in the
framework of a local--density approximation we calculate the neutronic specific
heat accounting for various shapes of the Coulomb lattice, from spherical to
non--spherical nuclear shapes. We find that a realistic nucleon--nucleon
potential leads to a significant increase in the neutronic specific heat with
respect to that obtained assuming a uniform neutron distribution. The increase
is largest for the non--spherical phase of the crust. These results may have
consequences for the thermal history of young neutron stars.


title: Color Transparency

abstract:
  The current status of the theory of and the experimental evidence for color
transparency are reviewed. The problems with interpretation of quasielastic
scattering on nuclei are discussed to some detail.


title:
Competing electric and magnetic excitations in backward electron
  scattering from heavy deformed nuclei

abstract:
  Important $E2$ contributions to the $(e,e^{\prime})$ cross sections of
low-lying orbital $M1$ excitations are found in heavy deformed nuclei, arising
from the small energy separation between the two excitations with $I^{\pi}K =
2^+1$ and 1$^+1$, respectively. They are studied microscopically in QRPA using
DWBA. The accompanying $E2$ response is negligible at small momentum transfer
$q$ but contributes substantially to the cross sections measured at $\theta =
165 ^{\circ}$ for $0.6 < q_{\rm eff} < 0.9$ fm$^{-1}$ ($40 \le E_i \le 70$ MeV)
and leads to a very good agreement with experiment. The electric response is of
longitudinal $C2$ type for $\theta \le 175 ^{\circ}$ but becomes almost purely
transverse $E2$ for larger backward angles. The transverse $E2$ response
remains comparable with the $M1$ response for $q_{\rm eff} > 1.2$ fm$^{-1}$
($E_i > 100$ MeV) and even dominant for $E_i > 200$ MeV. This happens even at
large backward angles $\theta > 175 ^{\circ}$, where the $M1$ dominance is
limited to the lower $q$ region.


title: Monte Carlo Methods for Nuclear Structure

abstract:
  Quantum Monte Carlo methods find fruitful application in large shell model
problems. These methods reduce the imaginary-time many-body evolution operator
to a coherent superposition of one-body evolutions in a fluctuating one-body
field; the resultant path integral is evaluated stochastically. After a brief
review of the capabilities and general strategy of Shell Model Monte Carlo
methods, I discuss results and insights obtained from a number of applications.
These include the ground state and thermal properties of {\it pf}-shell nuclei,
the thermal and rotational behavior of rare-earth and $\gamma$-soft nuclei, and
the calculation of double beta-decay matrix elements. Prospects for further
progress in such calculations are also discussed.


title:
Cascade particles, nuclear evaporation, and residual nuclei in high
  energy hadron-nucleus interactions

abstract:
  Based on a Monte Carlo realization of the Dual Parton Model we study the
production of target associated particles and of nuclear fragments in high
energy hadron-nucleus interactions. A formation zone intranuclear cascade of
low energy secondaries inside the target nucleus is discussed. We calculate
excitation energies of residual nuclei left after the intranuclear cascade
process and treat their further disintegration by introducing models for the
evaporation of protons, neutrons, and light fragments, high energy fission, and
by applying a Fermi Break-up model to light nuclear fragments. The results are
compared to data on target associated particle production. We furthermore
calculate cross sections for the production of nuclear fragments.


title: The Maximum Lifetime of the Quark-Gluon Plasma

abstract:
  The width $\Delta T$ of the deconfinement transition region is shown to
influence strongly the flow structure in the (Landau-) hydrodynamical expansion
of a quark-gluon plasma. For a sharp first order transition ($\Delta T=0$) the
mixed phase is rather long-lived, with a lifetime that has a maximum when the
initial energy density is at the phase boundary between mixed and pure
quark-gluon matter. For increasing $\Delta T$, however, the lifetime decreases
rapidly. Hadronic matter, however, remains long-lived as a consequence of the
rapid change in the degrees of freedom in the transition region and the
corresponding ``softening'' of the equation of state.


title: Phase Transition in Evolutionary Games

abstract:
  The evolution of cooperative behaviour is studied in the deterministic
version of the Prisoners' Dilemma on a two-dimensional lattice. The payoff
parameter is set at the critical region $1.8 < b < 2.0$ , where clusters of
cooperators are formed in all spatial sizes. Using the factorial moments
developed in particle and nuclear physics for the study of phase transition,
the distribution of cooperators is studied as a function of the bin size
covering varying numbers of lattice cells. From the scaling behaviour of the
moments a scaling exponent is determined and is found to lie in the range where
phase transitions are known to take place in physical systems. It is therefore
inferred that when the payoff parameter is increased through the critical
region the biological system of cooperators undergoes a phase transition to
defectors. The universality of the critical behaviour is thus extended to
include also this particular model of evolution dynamics.


title: Energy--level splitting in antiprotonic helium atoms

abstract:
  Recent experiments on the laser-induced resonant annihilation provide a
precise measurement of transition energies of antiprotonic helium atoms.
Relativistic corrections of an order of $\alpha ^2$ to the pure Coulomb
interaction will be taken into account in the theoretical description of energy
spectra of antiprotonic helium atoms. The splitting of energy levels arising
due to the spin-dependent part of the relativistic interaction is considered
for a number of states of $^{3,4}\! H\! e\bar pe$ systems.


title: Octupole Vibrations at High Angular Momenta

abstract:
  Properties of octupole vibrations in rapidly rotating nuclei are discussed.
Microscopic RPA calculations based on the cranked shell model are performed to
investigate the interplay between rotation and vibrations. The ability of this
model to describe the properties of collective vibrations built on the ground
bands in rare-earth and actinide nuclei is demonstrated at high angular
momentum. The octupole vibrational states in even-even superdeformed Hg nuclei
are also predicted and compared with available experimental data. A new
interpretation of the observed excited superdeformed bands invoking these
octupole bands is proposed.


title:
Mesonic Contribution to the Compton Scattering Amplitude for Heavy
  Nuclei

abstract:
  The contribution of mesonic exchange currents to nuclear Compton scattering
is investigated within the framework of a Fermi gas model of nuclear matter in
the non-relativistic limit. The additional interaction between the nucleons is
accounted for by including two- and three-body diagrams. As a test of this
model, the enhancement constant $\kappa $ is calculated. The full correlators
for the central and tensor part of the nucleon-nucleon interaction due to pion
exchange are obtained and the energy dependence of the amplitude is
investigated. The contribution of the $\Delta $-excitation to the mesonic part
of the Compton amplitude is calculated explicitely using an effective
Hamiltonian in the static limit.


title: A Test of the Eikonal Approximation in High-Energy (e,e'p) Scattering

abstract:
  The Glauber method is extensively used to describe the motion of a hadronic
projectile in interaction with the surrounding nuclear medium. One of the main
approximations consists in the linearization of the wave equation for the
interacting particle. We have studied the consequences of such an assumption in
the case of the $^{12}\mathrm{C(e,e}'\mathrm{p)}^{11}\hbox{\rm B}^*$ reaction
at high proton momenta by comparing the results with the predictions obtained
when all the ingredients of the calculation are unchanged but the second-order
differential equation for the scattered wave, which is solved exactly for each
partial wave up to a maximum of 120 spherical harmonics. We find that the
Glauber cross section is always larger by a factor $10 \div 20 \%$, even at
vanishing missing momenta. We give a quantum-mechanical explanation of this
discrepancy. Nevertheless, a good correlation is found between the two
predictions as functions of the missing momentum, especially in parallel
kinematics.


title: Effects of Instantons on the Excited Baryons and Two-Nucleon Systems

abstract:
  The effects of the spin-orbit and the tensor parts of the instanton-induced
interaction on the excited nonstrange baryons up to $N$=2 and on the
two-nucleon systems are investigated. The spin-orbit force from the
instanton-induced interaction cancels most of that from the one-gluon exchange
in the excited baryons while the spin-orbit force in the nucleon systems
remains strong after the inclusion of the instanton-induced interaction. The
model including the spin-orbit and the tensor terms of the instanton-induced
interaction as well as the one-gluon exchange is found to reproduce
successfully the excited baryon mass spectrum and the scattering phase shifts
of two nucleons in the spin-triplet relative $P$-wave state.


title: Electromagnetic Form Factors in a Collective Model of the Nucleon

abstract:
  We study the electromagnetic form factors of the nucleon in a collective
model of baryons. Using the algebraic approach to hadron structure, we derive
closed expressions for both elastic and transition form factors, and
consequently for the helicity amplitudes that can be measured in electro- and
photoproduction. Effects of spin-flavor symmetry breaking and of swelling of
hadrons with increasing excitation energy are considered.


title: Universal Predictions for Statistical Nuclear Correlations

abstract:
  We explore the behavior of collective nuclear excitations under a
multi-parameter deformation of the Hamiltonian. The Hamiltonian matrix elements
have the form $P(|H_{ij}|)\propto 1/\sqrt{|H_{ij}|}\exp(-|H_{ij}|/V)$, with a
parametric correlation of the type $\log \langle H(x)H(y)\rangle\propto
-|x-y|$. The studies are done in both the regular and chaotic regimes of the
Hamiltonian. Model independent predictions for a wide variety of correlation
functions and distributions which depend on wavefunctions and energies are
found from parametric random matrix theory and are compared to the nuclear
excitations. We find that our universal predictions are observed in the nuclear
states. Being a multi-parameter theory, we consider general paths in parameter
space and find that universality can be effected by the topology of the
parameter space. Specifically, Berry's phase can modify short distance
correlations, breaking certain universal predictions.


title: Off-shell effects in heavy particle production

abstract:
  Off-shell propagation of nucleons is neglected in one-body transport models
of heavy-ion collisions, but it could be significant in processes that are
limited by phase space, such as the threshold production of heavy particles. We
estimate the relative magnitude of off-shell production to on-shell production
of the N$^*$(1535) resonance in heavy ion collisions. In the region where the
on-shell production is dominated by a~two-step mechanism with an intermediate
$\Delta$, we find that the contribution of off-shell scattering between
projectile and target nucleons is indeed small. Beyond the latter contribution,
however, correlations in the initial wave function produce off-shell
contributions which can exceed those of the on-shell $\Delta$ mechanism.


title: The dd -> 4He eta Reaction Near Threshold

abstract:
  The cross section for the reaction $dd\rightarrow \,^4\!H\!e\,\eta$ close to
threshold is estimated in a two-step model, similar to that which successfully
describes near-threshold $pd\rightarrow \,^3\!H\!e\,\eta$ production. A
$\pi$-meson, created in a $dp\rightarrow \,^3\!H\!e\,\pi^o$ process on one
nucleon in the target deuteron, is converted into an $\eta$-meson by a
secondary $\pi^o n \to n\,\eta$ reaction on the other nucleon. The kinematics
are such that both processes are nearly physical so that only small Fermi
momenta are required. The predictions of the model are in good agreement with
recent Saclay experimental data.
  An analogous model, when applied to the near-threshold
$n\,^3\!H\!e\rightarrow \,^4\!H\!e\,\eta$ reaction, predicts a cross section of
a rather similar size, but experimental difficulties render this a doubtful
means of studying the $\eta\, ^4\!H\!e$ interaction.


title:
Critical point multiplicities and multiplicity fluctuations in heavy ion
  collisions

abstract:
  An exactly solvable model of nuclear fragmentation is shown to lead to a
simple connection between the critical point multiplicity $\langle m
\rangle_{c}$ and the critical point exponent $\tau$ recently reported on in the
EOS collaboration. The importance of multiplicity fluctuations on critical
point behavior is also discussed.


title:
Parity violation in quasielastic electron scattering from closed-shell
  nuclei

abstract:
  The electromagnetic and weak neutral current matrix elements that enter in
the analysis of parity-violating quasielastic electron scattering are
calculated using a continuum nuclear shell model. New approximations to the
on-shell relativistic one-body currents and relativistic kinematics for use in
such models are developed and discussed in detail. Results are presented for
three closed-shell nuclei of interest: $^{16}$O, $^{40}$Ca and $^{208}$Pb. The
current work concludes with a study of the sensitivity of the resulting
parity-violating asymmetries to properties of the nucleon form factors
including the possible strangeness content of the nucleon.


title:
The N*(1520) ---> Delta pi Amplitudes Extracted from the gamma p --->
  pi+ pi- p Reaction and Comparison to Quark Models

abstract:
  The gamma p ---> pi+ pi- p reaction, in combination with data from the pi N
---> pi pi N reaction, allows one to obtain the s- and d-wave amplitudes for
the N*(1520) decay into Delta pi with absolute sign with respect to the
N*(1520) ---> N gamma helicity amplitudes. In addition one obtains the novel
information on the q dependence of the amplitudes. This dependence fits exactly
with the predictions of the non-relativistic constituent quark models. The
absolute values provided by these models agree only qualitatively, and a
discussion is done on the reasons for it and possible ways to improve.


title:
Contribution of the NN inelasticity into photodisintegration of the
  deuteron

abstract:
  The technique of dispersion integration over the mass of composite particle
is used to describe the reaction of the deuteron photodisintegration. The
influence of the final state interaction (FSI) on the total cross section,
calculated with and without inelasticity is investigated. Numerical results
depend on the choice of the vertex function for the isobar photoproduction.


title: Time-odd components in the rotating mean field and identical bands

abstract:
  A systematic construction of the energy-density functional within the local
density approximation is presented. The Hartree-Fock equations corresponding to
such a functional are solved in case of rotating superdeformed nuclei. The
identical bands in $^{152}$Dy, $^{151}$Tb, and $^{150}$Gd are investigated and
the time-odd components in the rotating mean field are analyzed.


title:
Two step mechanism of $\eta , \eta', \omega , \phi $ meson prodction in
  $pD \to ^3He $ reaction$

abstract:
  The differential cross sections of $pD\to ^3He X$ reactions, where $X=\eta, \
\eta'\ ,\omega, \ \phi $, are calculated on the basis of a two-step mechanism
involving the subprocesses $pp\to d\pi ^+$ and $\pi^+n\to Xp $. It is shown
that this model describes well the form of energy dependence of available
experimental cross sections at the final c.m.s. momentum $p^*$=0.4-1$ GeV/c$
for the $\eta $ and at $p^*=0-0.5$ GeV/c for the $\omega $ meson as well as the
ratios $R(\eta'/\eta) $ and $R(\phi/\omega)$. The absolute value of the cross
section is underestimated by an overall normalization factor of about 3 for
$\eta, \ \eta '$ and by nearly one order of magnitude for $\omega$ and $\phi$.
The spin-spin correlations are predicted for the reaction ${\vec D}{\vec p}\to
^3He X$ in the forward-backward approximations for the elementary amplitudes.


title: Hot nuclear matter with dilatons

abstract:
  We study hot nuclear matter in a model based on nucleon interactions deriving
from the exchange of scalar and vector mesons. The main new feature of our work
is the treatment of the scale breaking of quantum chromodynamics through the
introduction of a dilaton field. Although the dilaton effects are quite small
quantitatively, they affect the high-temperature phase transition appreciably.
We find that inclusion of the dilaton leads to a metastable high-density state
at zero pressure, similar to that found by Glendenning who considered instead
the admixture of higher baryon resonances.


title: Quantum Chaos in Vibrational Nuclei: the Green Function Approach

abstract:
  We show that the collective vibrational model of atomic nuclei displays
quantum chaos. To avoid the problems related to the tunneling effects, a Green
function deterministic numerical method has been used to evaluate the energy
levels.


title: Microscopic study of superdeformation in the A=150 mass region

abstract:
  The cranked Hartree-Fock-Bogoliubov method presented in previous studies of
superdeformed bands in Hg and Pb isotopes is applied to the study of
superdeformed bands in Gd150, Dy152, Dy151 and Tb151. The same
density-dependent zero-range pairing interaction used in the A=190 mass region
leads to a similarly good agreement with the experimental data. In particular,
our results confirm the importance of a correct treatment of pairing
correlations in Gd150 to reproduce its experimental dynamical moment of
inertia. The quasi-particle spectra obtained for all the nuclei studied here
are compatible with the experimental results obtained for excited bands in this
mass region. The quality of our results opens the possibility of studying
microscopically very subtle phenomena like the properties of identical bands.


title: Parity Violation in Neutron-Nucleus Collisions at Very Low Energies

abstract:
  We investigate parity violation in neutron-nucleus collisions at very low
energy region $(E \leq 100 \ev)$, including resonance states. We use the
coupled channel formalism for resonances with radiative emission. The parity
mixing between resonances with opposite parities is taken into account.
Finally, our theory is applied to $n-^{139}$La collision and relevant remarks
are given.


title: Solution of the Nuclear Shell Model by Symmetry-Dictated Truncation

abstract:
  The dynamical symmetries of the Fermion Dynamical Symmetry Model are used as
a principle of truncation for the spherical shell model. Utilizing the usual
principle of energy-dictated truncation to select a valence space, and
symmetry-dictated truncation to select a collective subspace of that valence
space, we are able to reduce the full shell model space to one of manageable
dimensions with modern supercomputers, even for the heaviest nuclei. The
resulting shell model then consists of diagonalizing an effective Hamiltonian
within the restricted subspace. This theory is not confined to any symmetry
limits, and represents a full solution of the original shell model if the
appropriate effective interaction of the truncated space can be determined. As
a first step in constructing that interaction, we present an empirical
determination of its matrix elements for the collective subspace with no broken
pairs in a representative set of nuclei with $130\le A \le 250$. We demonstrate
that this effective interaction can be parameterized in terms of a few
quantities varying slowly with particle number, and is capable of describing a
broad range of low-energy observables for these nuclei. Finally we give a brief
discussion of extending these methods to include a single broken collective
pair.


title:
The fermion dynamical symmetry model for the even--even and even--odd
  nuclei in the Xe--Ba region

abstract:
  The even--even and even--odd nuclei $^{126}$Xe-$^{132}$Xe and
$^{131}$Ba-$^{137}$Ba are shown to have a well-realized $SO_8 \supset SO_6
\supset SO_3$ fermion dynamical symmetry. Their low-lying energy levels can be
described by a unified analytical expression with two (three) adjustable
parameters for even--odd (even--even) nuclei that is derived from the fermion
dynamical symmetry model. Analytical expressions are given for wavefunctions
and for $E2$ transition rates that agree well with data. The distinction
between the FDSM and IBM $SO_6$ limits is discussed. The experimentally
observed suppression of the the energy levels with increasing $SO_5$ quantum
number $\tau$ can be explained as a perturbation of the pairing interaction on
the $SO_6$ symmetry, which leads to an $SO_5$ Pairing effect for $SO_6$ nuclei.


title: Searching for three-nucleon resonances

abstract:
  We search for three-neutron resonances which were predicted from pion double
charge exchange experiments on He-3. All partial waves up to J=5/2 are
nonresonant except the J=3/2^+ one, where we find a state at E=14 MeV energy
with 13 MeV width. The parameters of the mirror state in the three-proton
system are E=15 MeV and Gamma=14 MeV. The possible existence of an excited
state in the triton, which was predicted from a H(He-6,alpha) experiment, is
also discussed.


title:
Towards a Unified Description of the Baryon Spectrum and the
  Baryon-Baryon Interaction within a Potential Model Scheme

abstract:
  We study the low energy part of the nucleon and $\Delta$ spectra by solving
the Schr\"{o}dinger equation for the three-quark system in the hyperspherical
harmonic approach. The quark-quark hamiltonian considered includes, besides the
usual one-gluon exchange, pion and sigma exchanges generated by the chiral
symmetry breaking. This quark-quark potential reproduces, in a Resonating Group
Method calculation, the nucleon-nucleon scattering phase shifts and the
deuteron properties. The baryonic spectrum obtained is quite reasonable and the
resulting wave function is consistent with the ansatz used in the two baryon
system.


title: Nuclear Physics --- at the frontiers of knowledge

abstract:
  (transcript of a talk given by Prof.~Feshbach:) Nuclear physics has been and
will be a major factor in science and technology. It makes unique and important
contributions to medicine, to industry and to other sciences. Interaction with
other physics has been strong. Astrophysics and mesoscopic physics are notable
examples. But what I shall talk about today are labeled {\bf``universals"}.
This refers to results which transcend the limits of a given subject providing
fundamental principles which inform not only nuclear physics but all of
science. It is the universals which take nuclear physics research from the
parochial albeit fascinating studies of nuclear reactions and structure to the
development and formulation of concepts of significance for all of the physical
sciences.


title: Parity-violating longitudinal response

abstract:
  The longitudinal quasielastic parity-violating electron scattering response
is explored within the context of a model that builds antisymmetrized RPA-HF
correlations on a relativistic Fermi gas basis. The large sensitivity to
nuclear dynamics of this observable, found in previous studies where only
pionic correlations were included, is shown to survive in the present model
where the effects from pion, rho, sigma and omega exchange in a version of the
Bonn potential are incorporated. Through an intricate diagrammatic
cancellation/filtration mechanism the longitudinal parity-violating response
turns out to be close to the one obtained in first-order perturbation theory
with the pion alone. Finally, in accord with our previous work, the
parity-violating response is seen to display appreciable sensitivity to the
electric strangeness content of the nucleon, especially at high momentum
transfer.


title: Parity-violating longitudinal response

abstract:
  The parity-violating quasielastic electron scattering response is explored
within the context of a model that builds antisymmetrized random phase
approximation and Hartree-Fock correlations on a relativistic Fermi gas basis.
Particular emphasis is put on the weak-neutral longitudinal response function,
since this observable displays a strong sensitivity to isospin correlations:
specifically, it is shown how, through a diagrammatic cancellation/filtration
mechanism, this response acts as a magnifier of pionic correlations in the
nuclear medium. The parity-violating longitudinal response function also
displays appreciable sensitivity to the electric strangeness content of the
nucleon, thus making quasielastic electron scattering a possible candidate to
measure the nucleon electric strange form factor at relatively high momentum
transfers. Finally, we discuss how observables, related to the asymmetry, can
be constructed to disentangle the nuclear and nucleonic effects.


title: Neutron Drops and Skyrme Energy-Density Functionals

abstract:
  The J$^{\pi}$=0$^+$ ground state of a drop of 8 neutrons and the lowest
1/2$^-$ and 3/2$^-$ states of 7-neutron drops, all in an external well, are
computed accurately with variational and Green's function Monte Carlo methods
for a Hamiltonian containing the Argonne $v_{18}$ two-nucleon and Urbana IX
three-nucleon potentials. These states are also calculated using Skyrme-type
energy-density functionals. Commonly used functionals overestimate the central
density of these drops and the spin-orbit splitting of 7-neutron drops.
Improvements in the functionals are suggested.


title:
The Non-Local Nature of the Nuclear Force and its Impact on Nuclear
  Structure

abstract:
  We calculate the triton binding energy with a non-local NN potential that
fits the world NN data below 350 MeV with the almost perfect $\chi^2$/datum of
1.03. The non-locality is derived from relativistic meson field theory. The
result obtained in a 34-channel, charge-dependent Faddeev calculation is 8.00
MeV, which is 0.4 MeV above the predictions by local NN potentials. The
increase in binding energy can be clearly attributed to the off-shell behavior
of the non-local potential. Our result cuts in half the discrepancy between
theory and experiment established from local NN potentials. Implications for
other areas of microscopic nuclear structure, in which underbinding is a
traditional problem, are discussed.


title:
Stability Analysis of the Instantaneous Bethe-Salpeter Equation and the
  Consequences for Meson Spectroscopy

abstract:
  We investigate the light and heavy meson spectra in the context of the
instantaneous approximation to the Bethe-Salpeter equation (Salpeter's
equation). We use a static kernel consisting of a one-gluon-exchange component
and a confining contribution. Salpeter's equation is known to be formally
equivalent to a random-phase-approximation equation; as such, it can develop
imaginary eigenvalues. Thus, our study can not be complete without first
discussing the stability of Salpeter's equation. The stability analysis limits
the form of the kernel and reveals that, contrary to the usual assumption, the
confining component can not transform as a Lorentz scalar; it must transform as
the timelike component of a vector. Moreover, the stability analysis sets an
upper limit on the size of the one-gluon-exchange component; the value for the
critical coupling is determined through a solution of the ``semirelativistic''
Coulomb problem. These limits place important constraints on the interaction
and suggest that a more sophisticated model is needed to describe the light and
heavy quarkonia.


title:
An Extension of the Fractional Parentage Expansion to Nonrelativistic
  and Relativistic $SU(3)_{f}$ Dibaryon Calculations

abstract:
  The fractional parentage expansion method is extended from $SU(2)_{f}$
nonrelativistic to $SU(3)_{f}$ and relativistic dibaryon calculations. A
transformation table between physical bases and symmetry bases for the
$SU(3)_{f}$ dibaryon is provided. A program package has been written for
dibaryon calculation based on the fractional parentage expansion method.


title: Relativistic Dynamics and Space-Time Structure of Few-Body Processes

abstract:
  The space-time features of the relativistic dynamics are analyzed in the
framework of the time dependent propagator theory. The adiabatic hypothesis is
substituted by the disturbative adiabatic hypothesis, resulting with the
corresponding space-time regionalization of scattering processes. The other
kind of generalization introduces forms of the propagator theory for the
particle systems whose propagation is based on the family of spacelike
surfaces. The mathematical basis is established allowing the definition of the
corresponding, generalized propagators and amplitudes.


title: Chaos and Quantum Chaos in Nuclear Systems

abstract:
  The presence of chaos and quantum chaos is shown in two different nuclear
systems. We analyze the chaotic behaviour of the classical SU(2)
Yang--Mills--Higgs system, and then we study quantum chaos in the nuclear shell
model calculating the spectral statistics of $A=46$--$50$ atomic nuclei.


title: Nuclear phenomena at HERA energies

abstract:
  We argue that current data on nuclear shadowing confirm expectations of the
color singlet models of nuclear shadowing. We demonstrate that unitarity
constrains require nuclear shadowing for gluons to be very significant already
for $x \le 10^{-3}$ . Physics of coherent diffraction production of vector
mesons off light nuclei is also discussed.


title: Studies of valence-quark shadowing at HERA

abstract:
  We propose to measure valence-quark shadowing by observing charged pion
productions in electron-nucleus scattering at HERA. Studies of shadowing
phenomena in the valence-quark distribution could be useful in discriminating
among various models, which produce similar results in the $F_2$ shadowing.


title: Virtual Pion Scattering

abstract:
  We propose a theory which exploits the charge-exchange reactions
($^3$He,$^3$H$\pi^+$) and (p,n$\pi^+$) as effective sources of virtual pions.
We consider processes in which the creation of virtual pions is followed by
conventional coupled-channel pion scattering to discrete nuclear states. This
picture allows us to incorporate successful theories of pion scattering and
utilize virtual pions as probes of the nuclear matter. For coherent pion
production we clearly demonstrate that the shift of the coherent peak position
in the excitation function of $^3$He-A relative to $^3$He-N scattering is
determined entirely by the pion nucleus rescattering.


title: Nuclear Reactions of Astrophysical Interest Involving Light Nuclei

abstract:
  An introduction to nucleosynthesis, the creation of the elements in the big
bang, in interstellar matter and in stars is given. The two--step process
$^4$He(2n,$\gamma$)$^6$He and the reverse photodisintegration
$^6$He($\gamma$,2n)$^4$He involving the halo nucleus $^6$He could be of
importance in the $\alpha$--process in type--II supernovae. The reaction rates
for the above processes are calculated using three--body methods and show an
enhancement of more than three orders of magnitude compared to the previous
adopted value. Direct--capture calculations give similar values for the above
reaction rates. Therefore, this method was also used to calculate the reaction
rates of the two--step processes $^6$He(2n,$\gamma$)$^8$He and
$^9$Li(2n,$\gamma$)$^{11}$Li and the reverse photodisintegration of $^8$He and
$^{11}$Li that could be also of importance in the $\alpha$-process.


title:
First Order Variational Calculation of Form Factor in a Scalar
  Nucleon--Meson Theory

abstract:
  We investigate a relativistic quantum field theory in the particle
representation using a non-perturbative variational technique. The theory is
that of two massive scalar particles, `nucleons' and `mesons', interacting via
a Yukawa coupling. We calculate the general Euclidean Green function involving
two external nucleons and an arbitrary number of external mesons in the
quenched approximation for the nucleons. The non-perturbative renormalization
and truncation is done in a consistent manner and results in the same
variational functional independent of the number of external mesons. We check
that the calculation agrees with one-loop perturbation theory for small
couplings. As an illustration the special case of meson absorption on the
nucleon is considered in detail. We derive the radius of the dressed particle
and numerically investigate the vertex function after analytic continuation to
Minkowski space.


title: About the decay of the $\Lambda$ in a nucleus

abstract:
  A few aspects of the $\Lambda$ mesonic and non-mesonic decay in nuclei are
shortly addressed.


title:
Character States and Generator Matrix Elements for $Sp(4) \supset SU(2)
  \times U(1)$

abstract:
  A new set of polynomial states (to be called character states) are derived
for $Sp(4)$ reduced to its $SU(2) \times U(1)$ subgroup, and the relevant
generator matrix elements are evaluated. The group--subgroup in question is
that of the seniority model of nuclear physics.


title: Opportunities in (semi-)inclusive deep inelastic scattering

abstract:
  Inclusive and semi-inclusive deep inelastic leptoproduction offers
possibilities to study details of the quark and gluon structure of the hadrons
involved. In many of these experiments polarization is an essential ingredient.
We also emphasize the dependence on transverse momenta of the quarks, which
leads to azimuthal asymmetries in the produced hadrons.


title: Modelling distribution functions and fragmentation functions

abstract:
  We present examples for the calculation of the distribution and fragmentation
functions using the representation in terms of non-local matrix elements of
quark field operators. As specific examples, we use a simple spectator model to
estimate the leading twist quark distribution functions and the fragmentation
functions for a quark into a nucleon or a pion.


title:
Nucleon-Nucleon Correlations and Inclusive Electron Scattering off
  Few-Nucleon Systems at $x>1$

abstract:
  Inclusive electron scattering off few-nucleon systems is investigated at
$x>1$ and high momentum transfer, including the contributions from
quasi-elastic and deep inelastic scattering processes. It is shown that at
$x>1$ the inclusive cross section is dominated by the process of virtual photon
absorption on a pair of correlated nucleons both in case of quasi-elastic and
deep inelastic scattering events. The sensitivity of the nuclear response to
the effects arising from the possible presence of multiquark cluster
configurations at short internucleon separations as well as from possible
medium-dependent modifications of the nucleon structure function, is
illustrated.