137 research outputs found
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
Viscosity and viscosity anomalies of model silicates and magmas: a numerical investigation
We present results for transport properties (diffusion and viscosity) using
computer simulations. Focus is made on a densified binary sodium disilicate
2SiO-NaO (NS2) liquid and on multicomponent magmatic liquids (MORB,
basalt). In the NS2 liquid, results show that a certain number of anomalies
appear when the system is densified: the usual diffusivity maxima/minima is
found for the network-forming ions (Si,O) whereas the sodium atom displays
three distinct r\'egimes for diffusion. Some of these features can be
correlated with the obtained viscosity anomaly under pressure, the latter being
be fairly well reproduced from the simulated diffusion constant. In model
magmas (MORB liquid), we find a plateau followed by a continuous increase of
the viscosity with pressure. Finally, having computed both diffusion and
viscosity independently, we can discuss the validity of the Eyring equation for
viscosity which relates diffusion and viscosity. It is shown that it can be
considered as valid in melts with a high viscosity. On the overall, these
results highlight the difficulty of establishing a firm relationship between
dynamics, structure and thermodynamics in complex liquids.Comment: 13 pages, 8 figure
Partial energies fluctuations and negative heat capacities
We proceed to a critical examination of the method used in nuclear
fragmentation to exhibit signals of negative heat capacity. We show that this
method leads to unsatisfactory results when applied to a simple and well
controlled model. Discrepancies are due to incomplete evaluation of potential
energies.Comment: Modified figures 3 and
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
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
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