3,538 research outputs found
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
Kinetic Heterogeneities at Dynamical Crossovers
We perform molecular dynamics simulations of a model glass-forming liquid to
measure the size of kinetic heterogeneities, using a dynamic susceptibility
that quantifies the number of particles whose dynamics
are correlated on the length scale and time scale . By measuring
as a function of both and , we locate local maxima
at distances and times . Near the dynamical
glass transition, we find two types of maxima, both correlated with crossovers
in the dynamical behavior: a smaller maximum corresponding to the crossover
from ballistic to sub-diffusive motion, and a larger maximum corresponding to
the crossover from sub-diffusive to diffusive motion. Our results indicate that
kinetic heterogeneities are not necessarily signatures of an impending glass or
jamming transition.Comment: 6 pages, 4 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,
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
Chiral symmetry restoration in (2+1)-dimensional with a Maxwell-Chern-Simons term at finite temperature
We study the role played by a Chern-Simons contribution to the action in the
formulation of a two-dimensional Heisenberg model of quantum spin
systems with a strictly fixed site occupation at finite temperature. We show
how this contribution affects the screening of the potential which acts between
spinons and contributes to the restoration of chiral symmetry in the spinon
sector. The constant which characterizes the Chern-Simons term can be related
to the critical temperature above which the dynamical mass goes to zero.Comment: 8 pages, 4 figure
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
A model for nuclear matter fragmentation: phase diagram and cluster distributions
We develop a model in the framework of nuclear fragmentation at thermodynamic
equilibrium which can be mapped onto an Ising model with constant
magnetization. We work out the thermodynamic properties of the model as well as
the properties of the fragment size distributions. We show that two types of
phase transitions can be found for high density systems. They merge into a
unique transition at low density. An analysis of the critical exponents which
characterize observables for different densities in the thermodynamic limit
shows that these transitions look like continuous second order transitions.Comment: 27 pages, 5 figures; comments on microcanonical approach and other
minor corrections added; references added; 1 figure change
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