2,925 research outputs found
Is binary sequential decay compatible with the fragmentation of nuclei at high energy?
We use a binary sequential decay model in order to describe the fragmentation
of a nucleus induced by the high energy collisions of protons with Au nuclei.
Overall agreement between measured and calculated physical observables is
obtained. We evaluate and analyse the decay times obtained with two different
parametrisations of the decay rates and discuss the applicability of the model
to high energy fragmentation.Comment: 6 pages, 4 eps figures. Small changes at the end of the text. More
arguments are given in the discussion of the time scale of the proces
Microscopic systems with and without Coulomb interaction, fragmentation and phase transitions in finite nuclei
We test the influence of the Coulomb interaction on the thermodynamic and
cluster generation properties of a system of classical particles described by
different lattice models. Numerical simulations show that the Coulomb
interaction produces essentially a shift in temperature of quantities like the
specific heat but not qualitative changes. We also consider a cellular model.
The thermodynamic properties of the system are qualitatively unaltered.Comment: 8 pages, 9 figures. New comments concerning the effect of the Coulomb
interaction on the caloric curve. Justification of the criterion which
defines bound clusters. Further comments about the identification of the
order of the transition. To be published in Eur. Phys. J.
Phase space characteristics of fragmenting nuclei described as excited disordered systems
We investigate the thermodynamical content of a cellular model which
describes nuclear fragmentation as a process taking place in an excited
disordered system. The model which reproduces very well the size distribution
of fragments does not show the existence of a first order phase transition.Comment: 14 pages, TeX type, 7 figure
Site occupation constraints in mean-field approaches of quantum spin systems at finite temperature
We study the effect of site occupation on the description of quantum spin
systems at finite temperature and mean-field level. We impose each lattice site
to be occupied by a single electron. This is realized by means of a specific
prescription. The outcome of the prescription is compared to the result
obtained by means of a projection procedure which fixes the site occupation to
one particle per site on an average. The comparison is performed for different
representations of the Hamiltonian in Fock space leading to different types of
mean-field solutions. The behaviour of order parameters is analyzed for each
choice of the mean-field and constraint which fixes the occupation rate at each
site. Sizable quantitative differences between the outcomes obtained with the
two different constraints are observed.Comment: 18 pages, 2 figure
Integrated On-Farm Decision Making: Economic Implications of Increased Variation in Litter Size
Increased litter sizes and associated piglet performance consequences, challenge swine producers. Stochastic modeling captured bioeconomic performance of individual piglets. As average litter size increased from 8.8 to 20.8 piglets, costs and revenues per head marketed from the demonstration herd decreased and total profit increased at a decreasing rate.stochastic modeling, farm business management, swine litter size, Agribusiness, Farm Management, Livestock Production/Industries,
About the determination of critical exponents related to possible phase transitions in nuclear fragmentation
We introduce a method based on the finite size scaling assumption which
allows to determine numerically the critical point and critical exponents
related to observables in an infinite system starting from the knowledge of the
observables in finite systems. We apply the method to bond percolation in 2
dimensions and compare the results obtained when the bond probability p or the
fragment multiplicity m are chosen as the relevant parameter.Comment: 12 pages, TeX, 4 figure
Localization Properties of Two Interacting Electrons in a Disordered Quasi One-Dimensional Potential
We study the transport properties of two electrons in a quasi one-dimensional
disordered wire. The electrons are subject to both, a disorder potential and a
short range two-body interaction. Using the approach developed by Iida et al. [
Ann. Phys. (N.Y.) 200 (1990) 219 ], the supersymmetry technique, and a suitable
truncation of Hilbert space, we work out the two-point correlation function in
the framework of a non-linear sigma model. We study the loop corrections to
arbitrary order. We obtain a remarkably simple and physically transparent
expression for the change of the localization length caused by the two-body
interaction.Comment: 10 page
Thermodynamics of a finite system of classical particles with short and long range interactions and nuclear fragmentation
We describe a finite inhomogeneous three dimensional system of classical
particles which interact through short and (or) long range interactions by
means of a simple analytic spin model. The thermodynamic properties of the
system are worked out in the framework of the grand canonical ensemble. It is
shown that the system experiences a phase transition at fixed average density
in the thermodynamic limit. The phase diagram and the caloric curve are
constructed and compared with numerical simulations. The implications of our
results concerning the caloric curve are discussed in connection with the
interpretation of corresponding experimental data.Comment: 11pages, LaTeX, 6 figures. Major change : A new section dealing with
numerical simulations in the framework of a cellular model has been adde
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