11,235 research outputs found
Specific heat at constant volume in the thermodynamic model
A thermodynamic model for multifragmentation which is frequently used appears
to give very different values for specific heat at constant volume depending
upon whether canonical or grand canonical ensemble is used. The cause for this
discrepancy is analysed.Comment: Revtex, 7 pages including 4 figure
Negative specific heat in a thermodynamic model of multifragmentation
We consider a soluble model of multifragmentation which is similar in spirit
to many models which have been used to fit intermediate energy heavy ion
collision data. In this model is always positive but for finite nuclei
can be negative for some temperatures and pressures. Furthermore,
negative values of can be obtained in canonical treatment. One does not
need to use the microcanonical ensemble. Negative values for can persist
for systems as large as 200 paticles but this depends upon parameters used in
the model calculation. As expected, negative specific heats are absent in the
thermodynamic limit.Comment: Revtex, 13 pages including 6 figure
Model of multifragmentation, Equation of State and phase transition
We consider a soluble model of multifragmentation which is similar in spirit
to many models which have been used to fit intermediate energy heavy ion
collision data. We draw a p-V diagram for the model and compare with a p-V
diagram obtained from a mean-field theory. We investigate the question of
chemical instability in the multifragmentation model. Phase transitions in the
model are discussed.Comment: Revtex, 9 pages including 6 figures: some change in the text and Fig.
Incorporating Radial Flow in the Lattice Gas Model for Nuclear Disassembly
We consider extensions of the lattice gas model to incorporate radial flow.
Experimental data are used to set the magnitude of radial flow. This flow is
then included in the Lattice Gas Model in a microcanonical formalism. For
magnitudes of flow seen in experiments, the main effect of the flow on
observables is a shift along the axis.Comment: Version accepted for publication in Phys. Rev. C, Rapid Communicatio
Caloric Curves for small systems in the Nuclear Lattice Gas Model
For pedagogical reasons we compute the caloric curve for 11 particles in a
lattice. Monte-Carlo simulation can be avoided and exact results are
obtained. There is no back-bending in the caloric curve and negative specific
heat does not appear. We point out that the introduction of kinetic energy in
the nuclear Lattice Gas Model modifies the results of the standard Lattice Gas
Model in a profound way.Comment: 12 pages, Revtex, including 4 postscript figure
Temperature determination from the lattice gas model
Determination of temperature from experimental data has become important in
searches for critical phenomena in heavy ion collisions. Widely used methods
are ratios of isotopes (which rely on chemical and thermal equilibrium),
population ratios of excited states etc. Using the lattice gas model we propose
a new observable: where is the charge multiplicity and
is the charge of the fragmenting system. We show that the reduced multiplicity
is a good measure of the average temperature of the fragmenting system.Comment: 11 pages, 2 ps file
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