2,296 research outputs found
Influence of Rashba and Dresselhaus spin-orbit interactions of equal strengths on electron states in a circular quantum ring in the presence of a magnetic field
Solutions of the Schr\"odinger equation are obtained for an electron in a
two-dimensional circular semiconductor quantum ring in the presence of both
external uniform constant magnetic field and the Rashba and Dresselhaus
spin-orbit interactions of equal strengths. Confinement is simulated by a
realistic potential well of a finite depth. The dependence of the energy levels
on a magnetic field strength, strength of spin-orbit interaction and a relative
ring width is presented.Comment: 6 pages, 2 figures, 1 tabl
Rashba spin-orbit interaction in a circular quantum ring in the presence of a magnetic field
Exact wave functions and energy levels are obtained for an electron in a
two-dimensional semiconductor circular quantum ring with a confining potential
of finite depth in the presence of both an external magnetic field and the
Rashba spin-orbit interaction.Comment: 7 pages, 4 figures, 2 table
Mean-field instabilities and cluster formation in nuclear reactions
We review recent results on intermediate mass cluster production in heavy ion
collisions at Fermi energy and in spallation reactions. Our studies are based
on modern transport theories, employing effective interactions for the nuclear
mean-field and incorporating two-body correlations and fluctuations. Namely we
will consider the Stochastic Mean Field (SMF) approach and the recently
developed Boltzmann-Langevin One Body (BLOB) model. We focus on cluster
production emerging from the possible occurrence of low-density mean-field
instabilities in heavy ion reactions. Within such a framework, the respective
role of one and two-body effects, in the two models considered, will be
carefully analysed. We will discuss, in particular, fragment production in
central and semi-peripheral heavy ion collisions, which is the object of many
recent experimental investigations. Moreover, in the context of spallation
reactions, we will show how thermal expansion may trigger the development of
mean-field instabilities, leading to a cluster formation process which competes
with important re-aggregation effects
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
- …