7,974 research outputs found
Effects of nucleus initialization on event-by-event observables
In this work we present a study of the influence of nucleus initializations
on the event-by-event elliptic flow coefficient, . In most Monte-Carlo
models, the initial positions of the nucleons in a nucleus are completely
uncorrelated, which can lead to very high density regions. In a simple, yet
more realistic model where overlapping of the nucleons is avoided, fluctuations
in the initial conditions are reduced. However, distributions are not
very sensitive to the initialization choice.Comment: 4 pages, 5 figures, to appear in the Bras. Jour. Phy
Three-dimensional patchy lattice model: ring formation and phase separation
We investigate the structural and thermodynamic properties of a model of
particles with patches of type and patches of type . Particles
are placed on the sites of a face centered cubic lattice with the patches
oriented along the nearest neighbor directions. The competition between the
self-assembly of chains, rings and networks on the phase diagram is
investigated by carrying out a systematic investigation of this class of
models, using an extension of Wertheim's theory for associating fluids and
Monte Carlo numerical simulations. We varied the ratio
of the interaction between patches and
, , and between patches, (
is set to ) as well as the relative position of the patches, i.e., the
angle between the (lattice) directions of the patches. We found
that both and ( or ) have a
profound effect on the phase diagram. In the empty fluid regime () the
phase diagram is re-entrant with a closed miscibility loop. The region around
the lower critical point exhibits unusual structural and thermodynamic behavior
determined by the presence of relatively short rings. The agreement between the
results of theory and simulation is excellent for but
deteriorates as decreases, revealing the need for new theoretical
approaches to describe the structure and thermodynamics of systems dominated by
small rings.Comment: 26 pages, 10 figure
Diffusion-limited deposition with dipolar interactions: fractal dimension and multifractal structure
Computer simulations are used to generate two-dimensional diffusion-limited
deposits of dipoles. The structure of these deposits is analyzed by measuring
some global quantities: the density of the deposit and the lateral correlation
function at a given height, the mean height of the upper surface for a given
number of deposited particles and the interfacial width at a given height.
Evidences are given that the fractal dimension of the deposits remains constant
as the deposition proceeds, independently of the dipolar strength. These same
deposits are used to obtain the growth probability measure through Monte Carlo
techniques. It is found that the distribution of growth probabilities obeys
multifractal scaling, i.e. it can be analyzed in terms of its
multifractal spectrum. For low dipolar strengths, the spectrum is
similar to that of diffusion-limited aggregation. Our results suggest that for
increasing dipolar strength both the minimal local growth exponent
and the information dimension decrease, while the fractal
dimension remains the same.Comment: 10 pages, 7 figure
Diffusion-limited deposition of dipolar particles
Deposits of dipolar particles are investigated by means of extensive Monte
Carlo simulations. We found that the effect of the interactions is described by
an initial, non-universal, scaling regime characterized by orientationally
ordered deposits. In the dipolar regime, the order and geometry of the clusters
depend on the strength of the interactions and the magnetic properties are
tunable by controlling the growth conditions. At later stages, the growth is
dominated by thermal effects and the diffusion-limited universal regime
obtains, at finite temperatures. At low temperatures the crossover size
increases exponentially as T decreases and at T=0 only the dipolar regime is
observed.Comment: 5 pages, 4 figure
Topological defects in lattice models and affine Temperley-Lieb algebra
This paper is the first in a series where we attempt to define defects in
critical lattice models that give rise to conformal field theory topological
defects in the continuum limit. We focus mostly on models based on the
Temperley-Lieb algebra, with future applications to restricted solid-on-solid
(also called anyonic chains) models, as well as non-unitary models like
percolation or self-avoiding walks. Our approach is essentially algebraic and
focusses on the defects from two points of view: the "crossed channel" where
the defect is seen as an operator acting on the Hilbert space of the models,
and the "direct channel" where it corresponds to a modification of the basic
Hamiltonian with some sort of impurity. Algebraic characterizations and
constructions are proposed in both points of view. In the crossed channel, this
leads us to new results about the center of the affine Temperley-Lieb algebra;
in particular we find there a special subalgebra with non-negative integer
structure constants that are interpreted as fusion rules of defects. In the
direct channel, meanwhile, this leads to the introduction of fusion products
and fusion quotients, with interesting mathematical properties that allow to
describe representations content of the lattice model with a defect, and to
describe its spectrum.Comment: 41
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