THE PERCOLATION APPROACH TO NUCLEUS BREAK-UP

Nucleus break up in violent collisions is studied as a critical phenomenon. We show how to determine various critical exponents from experimental data on mass distributions. A comparison is made with the predictions of percolation theory

CRITICAL EXPONENTS IN NUCLEAR BREAKUP

The moments of the fragment size distribution are studied for single events in a nuclear fragmentation experiment. It is shown that this nuclear breakup has clean remanents of a critical phenomenon

Percolation line of stable clusters in supercritical fluids

We predict that self-bound clusters of particles exist in the supercritical phase of simple fluids. These clusters, whose internal temperature is lower than the global temperature of the system, define a percolation line that starts at the critical point. This line should be physically observable. Possible experiments showing the validity of these predictions are discussed.Comment: 5 pages, 3 figures, corrected some typo

Analyzing Fragmentation of Simple Fluids with Percolation Theory

We show that the size distributions of fragments created by high energy nuclear collisions are remarkably well reproduced within the framework of a parameter free percolation model. We discuss two possible scenarios to explain this agreement and suggest that percolation could be an universal mechanism to explain the fragmentation of simple fluids.Comment: 12 pages, 11 figure

Quantum wells, wires and dots with finite barrier: analytical expressions for the bound states

From a careful study of the transcendental equations fulfilled by the bound state energies of a free particle in a quantum well, cylindrical wire or spherical dot with finite potential barrier, we have derived analytical expressions of these energies which reproduce impressively well the numerical solutions of the corresponding transcendental equations for all confinement sizes and potential barriers, without any adjustable parameter. These expressions depend on a unique dimensionless parameter which contains the barrier height and the sphere, wire or well radius.Comment: 4 pages, 3 figure

Introduction à la théorie des modules de formation d'amas. Application à la fragmentation des noyaux

École thématiqu

A Little Big Bang scenario of fragmentation

We suggest a multifragmentation scenario in which fragments are produced at an early, high temperature and high density, stage of the reaction. In this scenario, self-bound clusters of particles in the hot and dense fluid are the precursors of the observed fragments. This solves a number of recurrent problems concerning the kinetic energies and the temperature of the fragments, encountered with the standard low density fragmentation picture. The possibility to recover the initial thermodynamic parameters from the inspection of the asymptotic fragment size and kinetic energy distributions is discussed

A "Little Big Bang" Scenario of Multifragmentation

We suggest a multifragmentation scenario in which fragments are produced at an early, high temperature and high density, stage of the reaction. In this scenario, self-bound clusters of particles in the hot and dense fluid are the precursors of the observed fragments. This solves a number of recurrent problems concerning the kinetic energies and the temperature of the fragments, encountered with the standard low density fragmentation picture. The possibility to recover the initial thermodynamic parameters from the inspection of the asymptotic fragment size and kinetic energy distributions is discussed.Comment: 15 pages, 12 figure

Liquid-Gas Phase Transition in Nuclear Equation of State

A canonical ensemble model is used to describe a caloric curve of nuclear liquid-gas phase transition. Allowing a discontinuity in the freeze out density from one spinodal density to another for a given initial temperature, the nuclear liquid-gas phase transition can be described as first order. Averaging over various freeze out densities of all the possible initial temperatures for a given total reaction energy, the first order characteristics of liquid-gas phase transition is smeared out to a smooth transition. Two experiments, one at low beam energy and one at high beam energy show different caloric behaviors and are discussed.Comment: 12 pages in Revtex including two Postscript figure

Manipulating electronic states at oxide interfaces using focused micro X-rays from standard lab-sources

Recently, x-ray illumination, using synchrotron radiation, has been used to manipulate defects, stimulate self-organization and to probe their structure. Here we explore a method of defect-engineering low-dimensional systems using focused laboratory-scale X-ray sources. We demonstrate an irreversible change in the conducting properties of the 2-dimensional electron gas at the interface between the complex oxide materials LaAlO3 and SrTiO3 by X-ray irradiation. The electrical resistance is monitored during exposure as the irradiated regions are driven into a high resistance state. Our results suggest attention shall be paid on electronic structure modification in X-ray spectroscopic studies and highlight large-area defect manipulation and direct device patterning as possible new fields of application for focused laboratory X-ray sources.Comment: 12 pages, 4 figure