77 research outputs found
Exact methods for Campi plots
We introduce for canonical fragmention models an exact method for computing
expectation values which exclude the largest cluster. This method allows for
the computation of the reduced multiplicity and other quantities of interest
introduced by Campi, and a comparison shows that the percolation model and a
recent canonical model differ mostly only in small respects in these ensemble
averages.Comment: 7 pages, revtex 3.0, 2 figs. available on reques
Nuclear Incompressibility in Asymmetric Systems at Finite Temperature and Entropy
The nuclear incompressibility is investigated in asymmetric systems
in a mean field model. The calculations are done at zero and finite
temperatures and include surface, Coulomb and symmetry energy terms for several
equations of state. Also considered is the behavior of the incompressibility at
constant entropy which is shown to have a very different behavior
than the isothermal . Namely, decreases with increasing
entropy while the isothermal increases with increasing . A duality
is found between the adiabatic and the T=0 isothermal .
Analytic and also simple approximate expressions for are given.Comment: 11 page
Feshbach Resonances and Limiting Thermodynamics of Strongly Correlated Nucleons
A finite temperature model of strongly correlated nucleons with underlying
isospin symmetries is developed. The model can be used to study the role of
bound states and Feshbach resonances on the thermal properties of a spin 1/2,
isospin 1/2 system of protons and neutrons by varying the proton fraction. An
analysis of features associated with a universal thermodynamic limit or unitary
limit is given. In the limit of very large scattering length, the effective
range to quantum thermal wavelength appears as a limiting scale in an
interaction energy and equation of state.Comment: 8 pages, 4 figure
Disoriented Chiral Condensates, Pion Probability Distributions and Parallels with Disordered System
A general expression is discussed for pion probability distributions coming
from relativistic heavy ion collisions. The general expression contains as
limits: 1) The disoriented chiral condensate (DCC), 2) the negative binomial
distribution and Pearson type III distribution, 3) a binomial or Gaussian
result, 4) and a Poisson distribution. This general expression approximates
other distributions such as a signal to noise laser distribution. Similarities
and differences of the DCC distribution with these other distribution are
studied. A connection with the theory of disordered systems will be discussed
which include spin-glasses, randomly broken objects, random and chaotic maps.Comment: 5 pages, 1 figure include
Nuclear Chemical and Mechanical Instability and the Liquid-Gas Phase Transition in Nuclei
The thermodynamic properties of nuclei are studied in a mean field model
using a Skryme interaction. Properties of two component systems are
investigated over the complete range of proton fraction from a system of pure
neutrons to a system of only protons. Besides volume, symmetry, and Coulomb
effects we also include momentum or velocity dependent forces. Applications of
the results developed are then given which include nuclear mechanical and
chemical instability and an associated liquid/gas phase transition in two
component systems. The velocity dependence leads to further changes in the
coexistence curve and nuclear mechanical and chemical instability curves.Comment: 21 pages, 9 figures, Results are changed due to error in progra
A study of Feshbach resonances and the unitary limit in a model of strongly correlated nucleons
A model of strongly interacting and correlated hadrons is developed. The
interaction used contains a long range attraction and short range repulsive
hard core. Using this interaction and various limiting situations of it, a
study of the effect of bound states and Feshbach resonances is given. The
limiting situations are a pure square well interaction, a delta-shell potential
and a pure hard core potential. The limit of a pure hard core potential are
compared with results for a spinless Bose and Fermi gas. The limit of many
partial waves for a pure hard core interaction is also considered and result in
expressions involving the hard core volume. This feature arises from a scaling
relation similar to that for hard sphere scattering with diffractive
corrections. The role of underlying isospin symmetries associated with the
strong interaction of protons and neutrons in this two component model is
investigated. Properties are studied with varying proton fraction. An analytic
expression for the Beth Uhlenbeck continuum integral is developed which closely
approximates exact results based on the potential model considered. An analysis
of features associated with a unitary limit is given. In the unitary limit of
very large scattering length, the ratio of effective range to thermal
wavelength appears as a limiting scale. Thermodynamic quantities such as the
entropy and compressibility are also developed. The effective range corrections
to the entropy vary as the cube of this ratio for low temperatures and are
therefore considerably reduced compared to the corrections to the interaction
energy which varies linearly with this ratio. Effective range corrections to
the compressibility are also linear in the ratio.Comment: 39 pages, 15 figures, 2 table
Various Models for Pion Probability Distributions from Heavy-Ion Collisions
Various models for pion multiplicity distributions produced in relativistic
heavy ion collisions are discussed. The models include a relativistic
hydrodynamic model, a thermodynamic description, an emitting source pion laser
model, and a description which generates a negative binomial description. The
approach developed can be used to discuss other cases which will be mentioned.
The pion probability distributions for these various cases are compared.
Comparison of the pion laser model and Bose-Einstein condensation in a laser
trap and with the thermal model are made. The thermal model and hydrodynamic
model are also used to illustrate why the number of pions never diverges and
why the Bose-Einstein correction effects are relatively small. The pion
emission strength of a Poisson emitter and a critical density
are connected in a thermal model by , and this fact
reduces any Bose-Einstein correction effects in the number and number
fluctuation of pions. Fluctuations can be much larger than Poisson in the pion
laser model and for a negative binomial description. The clan representation of
the negative binomial distribution due to Van Hove and Giovannini is discussed
using the present description. Applications to CERN/NA44 and CERN/NA49 data are
discussed in terms of the relativistic hydrodynamic model.Comment: 12 pages, incl. 3 figures and 4 tables. You can also download a
PostScript file of the manuscript from
http://p2hp2.lanl.gov/people/schlei/eprint.htm
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