17 research outputs found
Simple mechanism rules the dynamics of volleyball
In volleyball games, we define a rally as the succession of events observed
since the ball is served until one of the two teams on the court scores the
point. In this process, athletes evolve in response to physical and information
constraints, spanning several spatiotemporal scales and interplaying
co-adaptively with the environment. Aiming to study the emergence of complexity
in this system, we carried out a study focused on three steps: data collection,
data analysis, and modeling. First, we collected data from 20 high-level
professional volleyball games. Then we conducted a data-driven analysis from
where we identified fundamental insights that we used to define a parsimonious
stochastic model for the dynamics of the game. On these bases, we show that it
is possible to give a closed-form expression for the probability that the
players perform n hits in a rally using only two stochastic variables. Our
results fully agree with the empirical observations and represent a new advance
in the comprehension of team-sports competition complexity and dynamics
Probabilistic model for Padel games dynamics
This study applies complexity sciences to analyze the game of Padel. Data
from 18 professional matches were collected, and the probability distributions
of the total number of shots and the probability distribution of rallies'
duration were analyzed. Based on these empirical observations and previous
reports, a probabilistic model with two parameters was proposed to describe the
game dynamics. One of them controls the probability of making a shot and the
other probability of doing it offensively. The model also considers the
offensive advantage of the team serving the ball. Using this model, an
analytical expression for the probability distribution of the total number of
shots was obtained and fit to the data. The results reveal that the complex
dynamics of Padel can be effectively approximated as a stochastic process
governed by simple probabilistic rules
Anisotropy-based mechanism for zigzag striped patterns in magnetic thin films
In this work we studied a two dimensional ferromagnetic system using Monte
Carlo simulations. Our model includes exchange and dipolar interactions, a
cubic anisotropy term, and uniaxial out-of-plane and in-plane ones. According
to the set of parameters chosen, the model including uniaxial out-of-plane
anisotropy has a ground-state which consists of a canted state with stripes of
opposite out-of-plane magnetization. When the cubic anisotropy is introduced
zigzag patterns appear in the stripes at fields close to the remanence. An
analysis of the anisotropy terms of the model shows that this configuration is
related to specific values of the ratio between the cubic and the effective
uniaxial anisotropy. The mechanism behind this effect is related to particular
features of the anisotropy's energy landscape, since a global minima transition
as a function of the applied field is required in the anisotropy terms. This
new mechanism for zigzags formation could be present in monocrystal
ferromagnetic thin films in a given range of thicknesses.Comment: 910 pages, 10 figure
The exchange bias phenomenon in uncompensated interfaces: Theory and Monte Carlo simulations
We performed Monte Carlo simulations in a bilayer system composed by two thin
films, one ferromagnetic (FM) and the other antiferromagnetic (AFM). Two
lattice structures for the films were considered: simple cubic (sc) and a body
center cubic (bcc). In both lattices structures we imposed an uncompensated
interfacial spin structure, in particular we emulated a FeF2-FM system in the
case of the (bcc) lattice. Our analysis focused on the incidence of the
interfacial strength interactions between the films J_eb and the effect of
thermal fluctuations on the bias field H_EB. We first performed Monte Carlo
simulations on a microscopic model based on classical Heisenberg spin
variables. To analyze the simulation results we also introduced a simplified
model that assumes coherent rotation of spins located on the same layer
parallel to the interface. We found that, depending on the AFM film anisotropy
to exchange ratio, the bias field is either controlled by the intrinsic pinning
of a domain wall parallel to the interface or by the stability of the first AFM
layer (quasi domain wall) near the interface.Comment: 18 pages, 11 figure
A Scaling Hypothesis for Modulated Systems
We propose a scaling hypothesis for pattern-forming systems in which
modulation of the order parameter results from the competition between a
short-ranged interaction and a long-ranged interaction decaying with some power
of the inverse distance. With L being a spatial length characterizing
the modulated phase, all thermodynamic quantities are predicted to scale like
some power of L. The scaling dimensions with respect to L only depend on the
dimensionality of the system d and the exponent \alpha. Scaling predictions are
in agreement with experiments on ultra-thin ferromagnetic films and
computational results. Finally, our scaling hypothesis implies that, for some
range of values \alpha>d, Inverse-Symmetry-Breaking transitions may appear
systematically in the considered class of frustrated systems.Comment: 13 pages, 6 figures, expanded versio
Anomalous behavior of the irreversible magnetization and time relaxation in YBaCuO single crystals with splayed tracks
We have studied the angular dependence of the irreversible magnetization and
its time relaxation in YBaCuO single crystals with one or two
families of columnar defects inclined with respect to the c-axis. At high
magnetic fields, the magnetization shows the usual maximum centered at the mean
tracks' orientation and an associated minimum in the normalized relaxation
rate. In contrast, at low fields we observe an anomalous local minimum in the
magnetization and a maximum in the relaxation rate. We present a model to
explain this anomaly based on the slowing down of the creep processes arising
from the increase of the vortex-vortex interactions as the applied field is
tilted away from the mean tracks' direction.Comment: 15 pages, 6 figures. Submitted to Phys. Rev .