113,861 research outputs found
A Unification Free Introduction to Logic Programming
In this paper, we give a new presentation of the fundamental results of the theory of Logic Programming, which differs from classical introductions in at least two ways: the use of predicate algebras to deal with model theoretical aspects and the parameterization of the resolution algorithm with respect to the specific unification algorithm implemented
Pettis integrability of fuzzy mappings with values in arbitrary Banach spaces
In this paper we study the Pettis integral of fuzzy mappings in arbitrary
Banach spaces. We present some properties of the Pettis integral of fuzzy
mappings and we give conditions under which a scalarly integrable fuzzy mapping
is Pettis integrable
Open boundary Quantum Knizhnik-Zamolodchikov equation and the weighted enumeration of Plane Partitions with symmetries
We propose new conjectures relating sum rules for the polynomial solution of
the qKZ equation with open (reflecting) boundaries as a function of the quantum
parameter and the -enumeration of Plane Partitions with specific
symmetries, with . We also find a conjectural relation \`a la
Razumov-Stroganov between the limit of the qKZ solution and refined
numbers of Totally Symmetric Self Complementary Plane Partitions.Comment: 27 pages, uses lanlmac, epsf and hyperbasics, minor revision
Probing the Nuclear Symmetry Energy with Heavy Ion Collisions
Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium
nuclear interaction in regions away from saturation. In this report we present
a selection of new reaction observables in dissipative collisions particularly
sensitive to the symmetry term of the nuclear Equation of State (). We
will first discuss the Isospin Equilibration Dynamics. At low energies this
manifests via the recently observed Dynamical Dipole Radiation, due to a
collective neutron-proton oscillation with the symmetry term acting as a
restoring force. At higher beam energies Iso-EoS effects will be seen in an
Isospin Diffusion mechanism, via Imbalance Ratio Measurements, in particular
from correlations to the total kinetic energy loss. For fragmentation reactions
in central events we suggest to look at the coupling between isospin
distillation and radial flow. In Neck Fragmentation reactions important Iso-EoS
information can be obtained from fragment isospin content, velocity and
alignement correlations. The high density symmetry term can be probed from
isospin effects on heavy ion reactions at relativistic energies (few AGeV
range), in particular for high transverse momentum selections of the reaction
products. Rather isospin sensitive observables are proposed from
nucleon/cluster emissions, collective flows and meson production. The
possibility to shed light on the controversial neutron/proton effective mass
splitting in asymmetric matter is also suggested.
A large symmetry repulsion at high baryon density will also lead to an
"earlier" hadron-deconfinement transition in n-rich matter. The binodal
transition line of the (T,\rho_B) diagram is lowered to a region accessible
through heavy ion collisions in the energy range of the new planned facilities,
e.g. the FAIR/NICA projects. Some observable effects of the formation of a
Mixed Phase are suggested, in particular a Neutron Trapping mechanism. The
dependence of the results on a suitable treatment of the isovector part of the
interaction in effective QCD Lagrangian approaches is critically discussed. We
stress the interest of this study in nuclear astrophysics, in particular for
supernovae explosions and neutron star structure, where the knowledge of the
Iso-EoS is important at low as well as at high baryon density.Comment: 52 pages, 28 figures, topical review submitted to J. Phys. G: Nucl.
Phys (IOP Latex
Isospin in fragment production
Based on a general approach to binary systems we show that in the low density
region asymmetric nuclear matter (ANM) is unstable only against isoscalarlike
fluctuations. The physical meaning of the thermodynamical chemical and
mechanical instabilities is related to the inequality relations verified by the
strength of interaction among different components. Relevance of these results
in bulk and neck fragmentation is discussed.Comment: 8 pages, 5 Postscript figures, talk at Cortona 2002 Conference,
Oct.7-Oct.12, Italy, World Scientific (in press
Reaction Dynamics with Exotic Beams
We review the new possibilities offered by the reaction dynamics of
asymmetric heavy ion collisions, using stable and unstable beams. We show that
it represents a rather unique tool to probe regions of highly Asymmetric
Nuclear Matter () in compressed as well as dilute phases, and to test the
in-medium isovector interaction for high momentum nucleons. The focus is on a
detailed study of the symmetry term of the nuclear Equation of State () in
regions far away from saturation conditions but always under laboratory
controlled conditions.
Thermodynamic properties of are surveyed starting from nonrelativistic
and relativistic effective interactions. In the relativistic case the role of
the isovector scalar -meson is stressed. The qualitative new features
of the liquid-gas phase transition, "diffusive" instability and isospin
distillation, are discussed. The results of ab-initio simulations of n-rich,
n-poor, heavy ion collisions, using stochastic isospin dependent transport
equations, are analysed as a function of beam energy and centrality. The
isospin dynamics plays an important role in all steps of the reaction, from
prompt nucleon emissions to the final fragments. The isospin diffusion is also
of large interest, due to the interplay of asymmetry and density gradients. In
relativistic collisions, the possibility of a direct study of the covariant
structure of the effective nucleon interaction is shown. Results are discussed
for particle production, collective flows and iso-transparency.
Perspectives of further developments of the field, in theory as well as in
experiment, are presented.Comment: 167+5 pages, 77 figures, general revie
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