Correlations in mesoscopic magnetic systems

The purpose of this proposal is to study the ferro/para phase transition in a mesoscopic Ising-like lattice and in particular demonstrate the existence of a negative magnetic susceptibility in the fixed magnetization ensemble. To this aim we will use the correlation = /N2 where N is the total number of spins for a single cluster, M the total magnetization of the cluster, and the equality holds if we choose r0<Dr<R where r0 is the linear size of a spin site and R is the linear size of a cluster

GIANT RESONANCES IN HEAVY ION COLLISIONS

This paper presents some of the new results on giant resonances obtained using heavy ion projectiles. It is shown that the microscopic structure of giant states can be probed using γ coincidence measurements. An example of the search for high lying states with light "heavy ion" probes at high incident energy is given and, the investigation of multiphonon excitation using heavier ions at intermediate energy is discussed. These experimental results are compared with the theoretical predictions of the multiphonon model. The role of giant resonances in heavy ion reactions is discussed and in the light of the new experimental results the importance of the multiphonon excitation for the heavy ion dynamics is emphasized

Ising analogue to compact-star matter

By constructing an Ising analogue of compact-star matter at sub-saturation density we explored the effect of Coulomb frustration on the nuclear liquid-gas phase transition. Our conclusions is twofold. First, the range of temperatures where inhomogeneous phases form expands with increasing Coulomb-field strength. Second, within the approximation of uniform electron distribution, the limiting point upon which the phase-coexistence region ends does not exhibit any critical behaviour. Possible astrophysics consequences and thermodynamical connections are discussed.Comment: 4 pages, 3 figure

Comment on "Partial energies fluctuations and negative heat capacities" by X. Campi et al

Studying the energy partioning published in nucl-th/0406056v2 we show that the presented results do not fulfill the sum rule due to energy conservation. The observed fluctuations of the energy conservation test point to a numerical problem. Moreover, analysis of the binding energies show that the fragment recognition algorithm adopted by Campi et al. leads with a sizeable probability to fragments containing up to the total mass even for excitation energies as large as 3/4 of the total binding. This surprising result points to another problem since the published inter-fragment energy is not zero while a unique fragment is present. This problem may be due to either the fragment recognition algorithm or to the definition of the inter and intra-fragment energy. These numerical inconsistencies should be settled before any conclusion on the physics can be drawn

From energy-density functionals to mean field potentials: a systematic derivation

In this paper we present a systematic method to solve the variational problem of the derivation of a self-consistent Kohn-Sham field from an arbitrary local energy functional. We illustrate this formalism with an application in nuclear physics and give the general mean field associated to the widely used Skyrme effective interaction

Tracking energy fluctuations from fragment partitions in the Lattice Gas model

Partial energy fluctuations are known tools to reconstruct microcanonical heat capacities. For experimental applications, approximations have been developed to infer fluctuations at freeze out from the observed fragment partitions. The accuracy of this procedure as well as the underlying independent fragment approximation is under debate already at the level of equilibrated systems. Using a well controlled computer experiment, the Lattice Gas model, we critically discuss the thermodynamic conditions under which fragment partitions can be used to reconstruct the thermodynamics of an equilibrated system.Comment: version accepted for publication in Phys.Rev.

Isospin coupling in time-dependent-mean-field theories and decay of isovector excitations

We show that isospin non-diagonal terms should appear in the mean field Hamiltonian when neutron-proton symmetry is broken. They give rise to charge mixing in the single-particle wave-functions. We study the Time Dependent Hartree-Fock response of a charge-exchange excitation which generates a charge mixing in Ca isotopes. We find an enhancement of the low energy proton emission in neutron-rich isotopes interpreted in terms of a charge oscillation below the barrier.Comment: 4 pages, 3 figure

Quantal Extension of Mean-Field Dynamics

A method is presented for numerical implementation of the extended TDHF theory in which two-body correlations beyond the mean-field approximation are incorporated in the form of a quantal collision term. The method is tested in a model problem in which the exact solution can be obtained numerically. Whereas the usual TDHF fails to reproduce the long time evolution, a very good agreement is found between the extended TDHF and the exact solution.Comment: 22 Latex pages including 7 figure